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ABSTRACT

Wear Testing Machine also called Tribometer is a type of Machine which shows us the lives of different material during operations.

The general name given to wear testing machine or device is tribometer its function is to perform tests and simulations of wear and friction which are the subject of the study of Tribology. Often Tribometers are extremely specific in their function, different Tribometers are used for different processing conditions, which test and analyze the long-term performance of the products.

The word is derived from the Greek word tribos meaning rubbing, so the literal translation would be “the science of rubbing”. Dictionaries define tribology as the science and technology of interacting surfaces in relative motion and of related subjects and practices.

Tribology is the art of applying operational analysis to problems of great economic significance, namely, reliability, maintenance, and wear of technical equipment, ranging from spacecraft to household appliances. Surface interactions in a tribological interface are highly complex, and their understanding requires knowledge of various disciplines including physics, chemistry, applied mathematics, solid mechanics, fluid mechanics, thermodynamics. A pin on disc tribometer consists of a stationary “pin” under an applied load in contact with a rotating disc. The pin can have any shape to simulate a specific contact. Coefficient of friction is determined by the ratio of the frictional force to the loading force on the pin.eat transfer, materials science, lubrication, machine design, performance and reliability.

This machine has components AC motor, disc, friction sensors, Normal Load Sensor, Variable Speed Controller, shafts, bearings, Magnetic force device (Plunger) and testing specimens.

From a material point of view, the test is performed to evaluate the wear property of a material so as to determine whether the material is adequate for a specific wear application.

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From a surface engineering point of view, wear test is carried out to evaluate the potential of using a certain surface engineering technology to reduce wear for a specific application, and to investigate the effect of treatment conditions (processing parameters) on the wear performance, so that optimized surface treatment conditions can be realized.

The pin-on-disk Tribometer serves for the investigation and simulation of friction and wear processes under sliding conditions.

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Chapter-1

INTRODUCTION

1.1 Introduction

Tribological failure of mechanical components is among the most common problems that limit productivity. A “tribometer” is an instrument that measures tribological quantities, such as coefficient of friction, friction force, and wear volume, between two surfaces in contact. It was invented by the 18th century Netherlands Dutch scientist „Pieter van Musschenbroek?. A ”’tribotester”’ is the general name given to a machine or device used to perform tests and simulations of wear, friction and lubrication which are the subject of the study of tribology. Often tribotesters are extremely specific in their function and are fabricated by manufacturers who desire to test and analyze the long-term performance of their products. Friction and wear testing using tribometers is commonly conducted in laboratories throughout the world for accelerated testing of materials. Metal on metal sliding contact at high speeds and high contact pressures can result in wear of one or both of the contacting bodies. Typical engineering systems subjected to high sliding speeds and high contact pressures include high speed machining. As an interdisciplinary area of research, tribology requires a thorough understanding of the specific properties of the material in question in relation to the surfaces of moving components. This in turn can provide important information for industrial applications by enabling the prediction of wear rates in practical industrial problems 1. By conducting fundamental tribological research on applied problems, such investigations can lead to resolving industrial, scientific or biomedical friction and wear issues. By conducting experiments on simplified specimens that decouple the effects of geometry on the tribological response, the fundamental material behavior can be captured. Individual wear mechanisms and processes such as edge chipping may be separately and easily identified using such material-level test procedures. Directed investigation in such areas has the potential to lead to beneficial discoveries otherwise overlooked in the study of prolonged and multi-mechanistic wear testing 2. Further, by varying speeds,

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lubricants, pressures and durations, a material response map as a function of process conditions can be obtained.

A pin on disc tribometer consists of a stationary “pin” under an applied load in contact with a rotating disc. The pin can have any shape to simulate a specific contact. Coefficient of friction is determined by the ratio of the frictional force to the loading force on the pin.

The pin on disc test has proved useful in providing a simple wear and friction test

for low friction coatings such
as diamond-like
carbon coatings
on valve

train components
in internal
combustion
engines.

Friction is the resistance force between two sliding contact surfaces.
Wear is the removal of material during sliding contact between these two surfaces.

1.2 Objectives

The specific objectives of this project are listed below:

1. To develop a low cost indigenous wear testing facility at the department.

2. To design the components for controlling applied loads and measuring frictional forces. Mechanical components will be designed, fabricated and calibrated for precise application and measurement of the relevant forces.

3. To instrument this assembly for real-time data acquisition and control. Force data will be acquired using force traducers and associated hardware?s and software?s.

1.3 Expected Contributions

The major expected contributions from this work are:

1. Design and assembly of individual tribometric testing components.

2. Assembly of pin-on-disc tribometer.

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3. Implementation of hardware and software for real-time force data acquisition
4. A standardized template usable by other investigators

5. Preliminary results from pin on disk tribology experiments to identify the material?s tribological response.

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Chapter-2

BACKGROUND & LITERATURE REVIEWE

The understanding of Tribology involves an extensive working knowledge of its uses and applications as well as the multiple possibilities of acquiring the specific information needed to analyze this information appropriately. For the purposes of this research, an overview of the most important aspects of this field will be covered to give a general knowledge of what is being evaluated. The following sections include general information on tribometers, their working principles, The forces being measured and how those forces are converted to useful information.

2.1 Pin-on-Disk Tribometer (TRB)

The Pin-on-Disk Tribometer is a table-top instrument, which is compact and can be installed on any stable table. With its combined computer control and TriboX software, it represents an easy-to-use instrument for all materials laboratories interested in conducting Tribological tests. Moreover, the installation is easy. The Tribometers have proven their reliability in over hundreds of laboratories worldwide, for studying:

• New materials (ceramics, metals, polymers)

• Lubricants and oil additives

• Self-lubricating systems

• Quality assurance

2.1.1 Technical features

Precisely calibrated friction and wear measurements Stable contact point and no parasitic friction Variable sample sizes and shapes Test in liquids and controlled humidity Possibility to perform a cross section profile of the wear track by making a pause during the test without modification of the experimental set-up.

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2.2. Principle of Tribometers

Tribometers can use both linear and rotary modes of motion in a large range of rpm?s. After the sample is mounted, a known normal force is applied on a pin or ball. This is commonly done with the use of a dead-weight force. The contact of the pin or ball with the surface to be studied generates wear. Whether the motion is linear or rotary, the deflection of the elastic arm is detected by a high resolution force sensor as seen in Figure 2.2 . This information is then converted by software equipped with the tribometer to the appropriate coefficient of friction. In addition, the volume lost allows for calculating the wear rate of the material.

Figure 2.2: Working Principle of a Tribometer

2.3 Experimental Methods

Recent experimental methods are divided into three categories.

2.3.1. Laboratory Test

The laboratory specimen test is mainly used to study friction and wear mechanisms and influence factors such as friction pair materials and to evaluate lubricant performances.

In laboratory test the environmental and working parameters can be easily controlled, the reproducibility of experimental data is high and the experimental period is short, so large data can be obtained in a short time.

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2.3.2 Simulation test

In simulation test the conditions are close to actual working conditions, it increases the reliability of the experimental results.

At the same time, through strictly controlled experimental conditions, a series of experimental data can also be obtained within a short period of time and that factors that affects the wear performance can also be studied.

2.3.3 Actual test

Actual test is based on the above two tests, an actual test is the final test which is much more actual and reliable, long and costly test cycle. The experimental results may be affected by various factors so it is difficult to analyze the results deeply. Actual test is a means of the two tests mentioned above.

The above three tests are based on experimental study and it should be noted that the experimental tests are not universal and actual. Therefore, the laboratory test can simulate actual working conditions, such as sliding velocity, surface pressure, temperature, lubrication state, environmental media conditions, surface contact form, and so on.

For high speed friction and wear, temperature is the main effecting factor. Therefore, thermal conditions and temperature distribution is close to the actual situation.

Generally, friction and wear testing machines are mainly used to simulate the performances of different materials and lubricants under different velocity, load and temperature conditions.

2.4. Types of Tribometers and their Functions

There are different types of tribometers classified according to their applications.

These are following.

2.4.1 Four Ball Tester

The tester can perform both Wear Preventative (WP) and Extreme Pressure (EP) analysis. Three balls are brought together in a clamped fashion. The fourth ball

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sits on top of the three balls and rotates for a fixed period of time. The load on the 4th ball can be varied.

In Wear Preventive (WP) tests the average scar diameter on the bottom three balls is reported. The size of the scar shows the ability of the lubricant to prevent wear. Loads applied during wear tests, produces circular wear scar on each ball and the average wear scar diameter is determined for comparison. Wear scar diameter on the steel balls are measured using an image acquisition system.

In Extreme Pressure (EP) tests the lubricant is subjected to load that is increased in specified steps after every run. The load is increased continuously till a load is reached where the lubricant fails. Welding of the bottom three balls to the top ball indicates failure of lubricant. The load at which welding occurs represents extreme pressure property of the lubricant. The normal load, friction force, and temperature can be monitored using Windows-based Data Acquisition Software.

Figure 2.4.1 Four Ball Tester

2.4.2. Reciprocating Sliding Friction and Wear test

The Reciprocating Sliding Friction and Wear test can be used to measure average coefficient of friction (COF) and wear. It is possible to perform dry and lubricated tests. Different types of contact geometries are possible such as Ball-on-disc, ball-on-plate, cylinder-on-disc, cylinder-on-plate and disc-on-disc. Load, Frequency, Stroke length and Temperature can be varied according to requirements.

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Figure 2.4.2: Reciprocating Sliding Friction and Wear test

2.4.3. BioTribometer

Bio Tribometers are used to mimic situations encountered in biological environments such as artificial joint replacements. Behavior of the materials used in these devices can be tested (in accelerated manner) with such tribometers. Materials like UHMWPE, Al2O3, Polycarbonate urethanes (PCU),Ti-6Al-4V are used to replace ace tabular cup, femur head, meniscus and tibia (epiphysis), respectively. Lubricant materials like hydrogels based phospholipids and animal derived hyaluronic acids are used as injectable lubricant supplements for knee and hip joints.

Figure2.4.3: BioTribometer

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2.4.4. Dry sand rubber/wheel abrasion test

Dry sand rubber/wheel abrasion test is one of the most widely used abrasion testing method. Low-stress scratching abrasion is simulated in the test by trapping

a stream of free-falling abrasives between a wear specimen and a rotating rubber coated wheel. The wear is usually determined by weight loss. A wide range of materials can be tested for example; metals, ceramics, plastics, composite materials and coatings.

Figure 2.4.4: Dry sand rubber/wheel abrasion test

2.4.5 Falex Pin & Vee Block Test:

The Falex Pin & Vee Block Test Machine is a laboratory tool for evaluating wear,

friction and extreme pressure properties of materials and lubricants. A steel journal is locked in place with a brass pin. Two V-blocks surround the journal while it rotates. The blocks apply increased pressure over time. The wear on the blocks can be measured to determine how much of the block was worn away.

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Figure 2.4.5: Falex Pin & Vee Block Test

2.4.6. High temperature Tribometer

High temperature Tribometer are used for analysis of friction and wear properties of materials at elevated temperatures. These tribometers can be used to measure friction and wear at temperatures as high as 1200-1500oC. These kind of tribometers generally use a furnace or insulated chamber equipped with heating coils to obtain high temperatures.

Figure 2.4.6: High temperature Tribometer

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2.4.7. Low temperature Tribometer

Low temperature Tribometer are used for analysis of friction and wear properties of materials at very low temperatures 0 to -50oC. These are generally used for testing materials used in space applications or for very low temperature regions (pipelines in polar regions e.g. Siberia). These kind of tribometers generally use liquid nitrogen or liquid helium to cool the interface.

2.4.8. Vacuum Tribometer

Vacuum Tribometer are designed to provide controlled vacuum conditions for friction and wear studies. Some of the tribometers are equipped with heating devices to perform tests at high temperature.

Figure 2.4.8: Vacuum Tribometer

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2.4.9. Taber Abraser Test

Taber Abraser test is used for measuring the abrasive wear resistance of a material. Test specimens are cut in shape of a disc. Then the specimens are placed on the turn-table and are subjected to rubbing action of a pair of rotating abrasive wheels at known weights.

Figure 2.4.9: Taber Abraser Test

2.4.10. Air Jet Erosion Test

Used to test materials, coatings, surface treated parts under erosive

environment/conditions. The test sample is subjected to a high speed stream of abrasive particulate gas for a certain duration and after test completion, the sample is checked for wear. The result of the test is reported as the loss of weight of the sample.

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Figure 2.4.10: Air Jet Erosion Test

2.5. Why PIN On Disc Tribometer?

As we explained different types of tribometers having different features but we select “pin on disc” because of some unique properties.

• wide range of test loads

• wide range of test speeds.The use of different wear track diameters enables

multiple tests to be performed on one sample

• choice of wear pin diameter and material

• testing can be carried out under dry or lubricated conditions

• Friction monitoring.

Pin-on-disk wear test requires two specimens. One, a pin with a radius tip, is positioned perpendicular to the other, usually a flat circular disk. The tester causes to revolve the disc against the specimen. The pin specimen is pressed against the disk at a specified load usually by means of an arm or lever and attached weights. Other loading methods have been used, such as, hydraulic or pneumatic.

Wear results may different for different loading methods. Wear results are reported as volume loss in cubic millimeters. When two different materials are

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tested, it is recommended that each material be tested in both the pin and disk positions. The amount of wear is determined by measuring appropriate linear dimensions of both specimens before and after the test, or by weighing both specimens before and after the test. If linear measures of wear are used, the length change or shape change of the pin, and the depth or shape change of the disk wear track are determined. Linear measures of wear are converted to wear volume (in cubic millimeters) by using appropriate geometric relations. Linear measures of wear are used frequently in practice since mass loss is often too small to measure precisely. If loss of mass is measured, the mass loss value is converted to volume loss (in cubic millimeters) from specimen density. Wear results may in some cases be reported as plots of wear volume versus sliding distance using different specimens for different distances. Such plots may display non-linear relationships between wear volume and distance over certain portions of the total sliding distance, and linear relationships over other portions.

Figure 2.5. : Pin on disc mechanism

2.6. WORKING PRINCIPLE OF PIN ON DISK TRIBOMETER

As we discussed earlier that wear rate is the volume loss of the material being tested during the test.

The wear rate

is

influenced

by

the

following

parameters:

Normal Load ( N )

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Sliding Speed( v )

Sliding Distance( s )

Volume loss ( ?V )

Frictional Force ( F )

The normal load(N) can be find by Compressive load cell.

Sliding speed (v) can be find from rotational speed at which the disc is revolving.

v = 2?R × (R.P.M)/60

Where RPM is the rotational speed “R” is the radius of contact point from the center of the disc.

The sliding distance can be find by multiplying the sliding speed with time for which the machine runs.

s = v/t

Where “t” is time and “v” is sliding speed.

Volume loss is given by

?V= A. ?L

where “A” is the area and “?L” is the change in length, which can be find from the loss in dimension.

Frictional force is given by:

f = ? × N

Where “N” is Normal force and “?” kinetic coefficient of friction.

The Wear Rate “W” is then given by:

W = A. ?L / (f × S). mm^3/(N-m).

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2.7 Force Measurement Using Different Strain Gauge Types

The strain gauge is the primary component of a load cell/sensor which allows the measurement of a voltage output caused by a change in the resistance of the circuit. This is used to represent useful information including presser, force, torque, position, etc. They rely on a pattern of resistive foil mounted on the backing of the material. As the foil is subjected to stress, its resistance changes. This change in resistance is measured using a Wheatstone bridge circuit. A quarter Wheatstone bridge circuit is displayed in Figure 2.7.1. The circuit is excited using a DC supply and various signal conditioning. Then as a load is applied to the sensor, the resistance change causes the Wheatstone bridge to become unbalanced and results in a signal output. Typically, this output is in millivolts and is amplified by the conditioning electronics to around 5 to 10 volts.

Figure 2.7.1. : Wheatstone bridge Circuit

The sensors used in this experiment are capable of measuring applied loads in more than one direction. If absolutely symmetrical, the measured force in each direction should be the same magnitude but negatives of each other. Figure 2.7.2 shows the compression and tension forces for this concept within a half Wheatstone bridge circuit.

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Figure 2.7.2. : Compression and Tension Forces

2.8. Force Data Acquisition (DAQ) System

Data acquisition systems are available in a variety of forms. The main principle behind DAQ systems involves acquiring signals from measurement sources and storing these signals in a digitalized form for analysis and presentation on a PC. There are five main components of a typical DAQ system commonly needed for almost any application:

2.8.1. Transducers and Sensors

Transducers and sensors are devices used to transform the physical characteristics to electrical. These are most commonly in the form of force, pressure, temperature, flow, etc.

2.8.2. Signals

There electrical signal produced by the transducers will typically be in the form of dc voltage, ac voltage, resistance, frequency, and current. For strain gauges, voltage is the electrical characteristic that is evaluated.

2.8.3. Signal Conditioning

Each signal a transducer or sensor produces will need to be conditioned or amplified to a form that is more easily measured by the system. Strain gauges

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typically produce electrical signals in the millivolt range that will need to be amplified to volts to make measuring feasible.

2.8.4. DAQ Hardware

Data Acquisition hardware commonly uses an A/D converter, which converts dc voltages acquired from the transducers into digital data. Advanced systems may include this conversion in the same control module used to condition the signal.

2.8.5. Driver Software

A supporting driver software is required in order to view the output data acquired by the transducers. Many hardware systems will come with their own software capable of viewing this data for real-time analysis.

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Chapter-3

COMPONENT DESIGN & SETUP FOR FORCE DATA ACQUISITION

This chapter deals with the design of the various components needed for applying and measuring forces that will replicate the functionality of a tribometer. It will explain the details of the forces that need to be applied and measured, and review the options available that were considered. Lastly, the selection and design process is explained so that proper reasoning may be shown supporting the final decision for the experimental design setup.

3.1Force-Related Requirements of the PIN on DISK Related Tribology

Specimens of a tribometer experiment will experience two basic forces that are shown in Figure 3.1. These are the normal and frictional forces imparted on the pin or ball from the disc.

Figure 3.1: Tribometer Forces

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3.2 Options for Attaining these Requirements Of Forces

3.2.1 Normal Force Application

The application of the normal force can be achieved by a variety of methods. The options that were considered for the purpose of this research experiment include the following:

1. Dead Weight Force:

This has proven from past researchers to be a crude but simple force application technique. Due to unwanted variables in the machine from movement and vibration, this method may not produce results that are in the desired range of accuracy. However, with further experimentation this concept may be a possibility if a sound and robust fixture system is designed and implemented onto the CNC. Figure 3.2.1.1 shows a dead-weight force application.

Figure 3.2.1.1: Dead-Weight Force Application

2. Pneumatic Air Piston:

Using controlled air to provide a constant normal force application, pneumatics is a reliable and cost effective technique to exert a normal force. It relies upon the concept of differential pressure inside a cylinder, thus causing a constant force in either direction. This would include an air cylinder fixed to either the tool post or

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carriage table while controlled by means of a regulator. Figure 3.2.1.2 shows a pneumatic cylinder force application.

Figure 3.2.1.2: Pneumatic Cylinder Force Application

3. Force Transducer:

A force transducer is a common device used to accurately measure an applied force onto a surface. These are commercially available in many different forms, most including options for DAQ. This device may either be incorporated with the existing tool post or on the carriage table. It may also be used with other force application devices such as pneumatic air pistons. Another requirement to keep in mind for this type of application would be the resolution of the device. These features are dependent of the quality of the force sensor. Figure 3.2.1.3 shows an S-beam force measurement.

Figure 3.2.1.3 : S-Beam Force Measurement

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3.2.2 Frictional Force Measurement

The application of the frictional force can also be demonstrated by several methods. This will be a more difficult characteristic to measure in this experiment. The ability of an actual tribometer to measure the frictional force between two objects is what primarily sets it apart from typical applications that measure contact forces. The options that were considered for the purpose of this research experiment include the following:

1. Torque Sensor:

There are torque sensors available commercially that if incorporated correctly could effectively measure the frictional force caused by the contact made during the experiment. This would be accomplished by measuring the real time torque output of the lathe spindle and noting the different torque value displayed while making contact with the specimen. This information along with the known rpm value will allow for the frictional force calculation. 3.2.2.1 shows a torque sensor measurement.

Figure 3.2.2.1: Torque Sensor Measurement

2. Bending beam load cell:

This is a much simpler means of acquiring the frictional force. Because the measured load output of this device is transverse to the sensor rather than a

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compressional or tensional load, it can be used to gather frictional force data.

Figure 3.2.2.2. shows a bending beam force measurement.

Figure 3.2.2.3: Bending Beam Force Measurement

3.3. Component Selection & Design For Force Measurement

The desired force range for measurement and acquisition has initially been estimated to be 1 – 100 N. The S-beam type transducer was selected to fulfill the normal force application (Figure 3.3.1).

Figure 3.3.1: S-Beam Transducer

A bending beam type transducer (Figure 3.3.2) was chosen to apply and measure the normal and frictional forces to the specimen. These options were chosen because they are accurate, use full-bridge strain gauge circuits, are DAQ compatible and are adaptable for use of a fixture with the CNC machine.

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Figure 3.3.2: Bending-Beam Transducer

The following shows the first design iteration for this component setup. Figure 3.3.3 shows a solid model of design 1 assembly.

Figure 3.3.3: Design 1 Assembly

This first design was not found to be optimal due to the misalignment of the S-beam axis of measurement with the center of the system. Design analysis suggested this would have caused the normal force to produce an unwanted bending moment about the bending beam load cell, which would be counter-

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productive in the frictional force measurement and yield incorrect data. Figure 3.3.4 shows the expected force misalignment in design 1.

Figure 3.3.4: Design 1 Force Misalignment

A design iteration (design 2) was created to eliminate the previous misalignment problem. The machined fixture pieces were altered in the 3D modeling software, allowing the entire system to become aligned properly. Figure 3.3.5 shows the design 2 to minimize/eliminate the unwanted moment.

Figure 3.3.5: Design 2 Minimizing the Misaligned Forces

The final solid model of design 2 can be seen in Figure 3.3.5.

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3.4 Fabrication of the Fixtures

For instrumenting this transducer assembly, the CNC machine was examined in depth and strategies for incorporating force application and measurement capabilities were explored and evaluated. The applied normal force will need to have low variability, and be perpendicular to the sliding velocity.

The material chosen for this experiment for fixtures was brass alloy. Adequate thicknesses were chosen to ensure that the minimal material deflection caused by the normal and frictional forces would be much less than that of the force sensors and therefore have little effect on the data results. A manual milling machine using appropriate tooling and feeds/speeds was used to create the fixtures that included flat faces, square geometry and adequate surface finish. This ensured that the entire fixture system would assemble correctly with the transducers and the machine beam for support. Figure 3.4 shows photos of the completed fixture pieces.

Figure 3.4: Actual Fixture Pieces

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Chapter-4

DETAILED DESIGN

4.1. Introduction

Design is either to formulate a plan for the satisfaction of a specified need or to solve a problem. If the plan results in the creation of something having a physical reality, then the product must be functional, safe, reliable, competitive, useful, useable, manufacture able and marketable. Design is a communication insensitive activity in which both words and pictures are used and written and oral forms are implied these are important skills and engineer?s success depends on them. Design is innovative and highly iterative process it is also a decision making process. Decisions sometimes have to be made with too little information 8.

The design process is a series of steps that engineers use to guide them as they solve problems. The design process is cyclical, meaning that engineers repeat the steps as many times as needed, making improvements along the way.

Some of the steps that engineers used in designing:

• define the Problem

• Do Background Research

• Specify Requirements

• Brainstorm Solutions

• Choose the Best Solution

• Do Development Work

• Build a Prototype

• Test and Redesign

The design of the machine will show that every component is safe while applying loads.

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4.2. Engineering Analysis, Mechanical Design Analysis

Mechanical design shows that the complete construction of every component used in the apparatus. Multi-purpose friction and wear testing machine?s components face the various loads including fatigue, friction, impact etc. The shaft used may twist or shear due to applied torque. The lever beam may buckle or bend. Similarly the load range if exceeds the motor may destroy. To avoid all these failures proper design and material selection should be selected. Proper design will avoid the components and machine from failures.

The design of following components is explained below:

4.2.1. Shaft

Shaft is a mechanical component that transmits power (torsion load) from source to load. The shaft may be solid or hollow supported by bearings and it rotates a set of pulleys or gears for the purpose of power transmission. The shaft may be acted by bending moments, axial loads, vibrations or torsional loads.

Figure 4.2.1: Different shafts design

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4.2.1.1 Design Analysis

The shaft may be acted by bending moments, axial loads, vibrations or torsional loads. We are designing the only for torsional load.

Figure 4.2.1.1.: Torsion in shaft

?max= ( 16T/?d3)

T= (5252*hp)/rpm

T= 1.875 N.m

N for variable motor= 2800RPM

T=1.875N.m or

1875 N.mm

So ?max= (16×1875)/3.14d3

?max for steel = 383MPa or 383 N/mm
d=1.15 in 0r d= 2.921cm

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d= 29.21mm

4.2.1.2 Materials Used

For the design of shaft we use alloy steel material

Any steel containing a notable quantity of some other metal alloyed with the iron, usually chromium, nickel, manganese, tungsten, or vanadium.

Low alloy steels have higher tensile and yield strengths than mild steel or carbon structural steel. Since they have high strength-to-weight ratios, they reduce dead weight in railroad cars, truck frames, heavy equipment, etc.

The following is a range of improved properties in alloy steels (as compared to carbon steels):

Strength, hardness, toughness, wear resistance, corrosion resistance, harden ability, and hot hardness. To achieve some of these improved properties the metal may require heat treating.

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Table 4.1

4.2.2. Rotating disc

In multi-purpose friction and wear testing machine, the disc rotates and the material is removed from the test specimen.

4.2.2.1 Design analysis

Mass of Disc:

d= 13.97 cm or 139.7mm, r= 69.85mm, r= 0.069.85m and t=5mm, t=5×10 -3m

2 ? (HSS) = 7972Kg/m3
V= ?r h
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V= 1.75×10 -4m3

m= ?V

Putting the values of density and volume, we get

m=1.251Kg

4.2.2.2. Material selection

For disc we select such a material which is harder so we will be able to perform a large number of tests. For this purpose we select the HSS (High speed steel).

HSS is characterized by balanced combination of abrasion resistance, toughness and good red hardness.

CHEMISTRY: C 0.83 Cr 4.15 Mo 5.00 V 1.90 W 6.35

PROPERTIES:

• They all possess a high-alloy content

• They usually contain sufficient carbon to permit hardening to 64 HRC

• They harden so deeply that almost any section encountered commercially will have a uniform hardness from center to surface

• They are all hardened at high temperatures, and their rate of transformation is such that small sections can be cooled in still air and be near maximum hardness

4.2.3. Maximum load

The maximum load is the load, beyond which the machine can go in the failure region.

Total Mass= (mdisc+ mlever+ mapplied) Kg

m= 1.251+0.5+2

Total m= 4.021Kg

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As Load (W) = mg
Wtotal= 39.40N
Friction force= µ×RN
µ for HSS and harden steel= 0.42

Normal force= 2Kg, 19.6N

Friction force= 19.6×0.42

Friction force= 8.232N

4.2.4 Motor specifications

Table 4.2: Motor specifications

Shaft diameter Shaft length Speed Voltage Power

0.8in 8.5in 2800rpm 220v (AC) 1HP

4.3. Cost Analysis

Table 4.3: Cost Analysis

Items Estimated price(PKR)
Electric Motor 20000
Variable Speed Controller 18000
Bearings 5000
Tachometer 3500
Sensors 18000
Shafts 3000
Magnetic Force Device 1000
Base Frame 20000
Data Acquisition 6000
Disc And sink 2000
Water Pump 2000
Total 98500

4.4. Hazards and Failure Analysis

An engineer has the responsibility to that ensure that anything he going to design
is safe and good to the public sector. If the design of any project is useless then it
is impossible to manufacture. Worse design has no market and people don?t like
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so we should focus on the design of the project. If the load exceeds the maximum, any of the components may fail.

4.5. Summary

The engineers have a great variety of tools and advanced computers which assists in the solution of a need. In addition to these tools the engineers always know the technical information.

4.6 CAD Modelling

4.6.1 Introduction

Computer-aided design (CAD) is the use of computer systems to assist in the creation, modification, analysis, or optimization of a design. CAD software is used to increase the productivity of the designer, improve the quality of design, improve communications through documentation, and to create a database for manufacturing. CAD output is often in the form of electronic files for print, machining, or other manufacturing operations.

Computer-aided design is used in many fields. Its use in designing electronic
systems is known as electronic design automation, or EDA. In mechanical design
it is known as mechanical design automation (MDA) or computer-aided
design (CAD), which includes the process of creating a technical drawing with the
use of computer software.

CAD software for mechanical design uses either vector-based graphics to depict the objects of traditional drafting, or may also produce raster graphics showing the overall appearance of designed objects. However, it involves more than just shapes. As in the manual drafting of technical and engineering drawings, the output of CAD must convey information, such as materials, processes, dimensions, and tolerances, according to application-specific conventions.

CAD may be used to design curves and figures in two-dimensional (2D) space; or curves, surfaces, and solids in three-dimensional (3D) space.

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CAD is an important industrial art extensively used in many applications, including automotive, shipbuilding, and aerospace industries, industrial and
architectural design, prosthetics, and many more. CAD is also widely used to
produce computer animation for special effects in movies, advertising and
technical manuals, often called DCC digital content creation. The modern ubiquity

and power of computers means that even perfume bottles and shampoo dispensers are designed using techniques unheard of by engineers of the 1960s. Because of its enormous economic importance, CAD has been a major driving force for

research in computational geometry, computer graphics (both hardware and software), and discrete differential geometry.

Despite the fact that a good proportion of an engineer?s representation is informal sketching, CAD systems today do not support sketching in any meaningful way. In fact, when commercial CAD systems advertise a „sketching? feature, they usually refer to interactive techniques such as “rubber banding” and dragging, rather than true freehand sketching. These interactive techniques, however, place a mental load on the designer; the cognitive process of drawing a line with a pencil is markedly different from that of specifying its endpoints. Moreover, the need to operate menus, commands, and other interface gadgets impedes the creative process taking place at that instant. Partially, this is because the mental image, visualized in the designer?s mind, needs to be „translated? into a set of logical construction operations, the vocabulary of which is dictated by the 12 software?s interface. In essence this is equivalent to the load of conveying a picture by a verbal description. According to Ullman, current CAD tools aid the designer in four ways: by serving as an advanced drafting tool; through assisting in the visualization of hardware and data; by improving data organization and communication; and by pre- and post-processing data for engineering tools such as finite elements or kinematic analysis. In this sense, the „D? in „CAD? really stands for drafting or modeling rather than design, albeit today the drafting is three-dimensional. Clearly, the lack of a true design capacity in CAD systems and their inability to perceive fluent and loose form of communication severely impedes their ability to support the initial, problem-solving conceptual design phase. Tomiyama et al propose the concept of an integrated designer?s workbench to assist the designer throughout the design process. Among their proposals is “a

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system for processing rough sketches or notes” (Tomiyama and Yoshikawa, 1985). Walderon et al (1988) put forward strong arguments for the development of tools to assist the engineer during the conceptual design phase and note that with current CAD systems “it is the computer that is driving the conceptual designer rather than the other way round”. In practice, conceptual designers rarely approach a CAD system before they have a well-defined idea of what they intend to do.

4.6.2 Design by sketching

In this section we put forward and demonstrate the main design approach proposed in this thesis. It starts by highlighting current drawbacks of computer aided engineering (CAE) tools, particularly at the conceptual design stage, and proposes several directions for improvement (Kimura, Lipson and Shpitalni, 1998). The key concepts of the proposed approach are demonstrated with a working implementation of a system for conceptual design of sheet metal parts (Shpitalni and Lipson, 1998). This chapter provides an overview of the thesis results without going into technical details of the implementation. Subsequent chapters provide the concepts, technical details, developed algorithms and detailed reviews of relevant work.

Over the past decade, changes in product development processes and increased consumer demands have dramatically influenced engineering working practices and targets. Development cycles for products have been reduced from several years to several months. Marketing deadlines have become crucial, as most profits are earned within a short period after product release. Among other consequences, the demand for shortened cycles has narrowed the leeway allowed for exploration, as engineers need to converge earlier to a particular design concept. Still, however, CAD tools are geared primarily towards later stages of detailed design, and so they cannot provide the support needed for critical early decisions. Typically, the short design cycles do not warrant the investment of time and effort required for preparation of a detailed model for analysis. This work puts forward the thesis that one of the reasons for this situation is the lack of communication (interface) and analysis means appropriate for the type of information and for the mode of thought at the conceptual design stage. Information at these preliminary

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stages is vague and not well defined; specification may be implicit, avoiding 22 a clear definition of design parameters. Information transfer, both from the user to the computer and back, must be fast, fluent and flexible, in order not to impede the creative flow of ideas. Moreover, analysis programs typically require too much information – more than is really needed to produce the kind of key analysis required for crucial decisions at the conceptual exploration stage. This creates an unnecessary information overload and further limits the leeway for exploration. This chapter demonstrates a system for conceptual design of sheet metal products based on these principles. The system employs a sketch-based interface, capable of “understanding” the sketched input rather than just accumulating graphic entities. The understanding is in the sense that the flat sketch is perceived, by the computer, as a three dimensional object; that object is analyzed in rough form and its properties are predicted. The output of the system is overlaid back onto the sketch in rough format, to minimize the cognitive load for interpretation of the results.

4.6.3 Levels of sketch interpreters

User interfaces based on on-line sketching are implemented on several levels and can generally be divided into three categories, according to the level of information they intend to gather from the input sketch:

1. Drawing Pads: These sketchers allow basic sketching for general-purpose drawings, especially in the graphic design arts. They smooth the input strokes and provide many 38 other graphic tools but do not attempt to interpret the drawing in any way.

2. 2D sketching systems: In 2D sketching systems, sketch strokes are smoothed and classified into 2D primitives, such as lines, arcs and splines. Some automatically infer constraints and relationships among the entities, such as parallelism or orthogonality, thus further refining the sketch (Jenkins and Martin, 1992; Kato et al, 1982; Pavlidis and Van Wyk, 1985; Bengi and Ozguc, 1990; Eggli et al, 1995).

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3. 3D sketching systems: Sketches are analyzed as representing rough projections of 3D scenes. The sketcher is still required to identify the sketch strokes as basic geometrical shapes, such as lines, arcs and corners. However, since the analyzed sketch represents a rough projection of a three-dimensional scene, some of the sketch strokes do not necessarily represent what they appear to be. For instance, a circular arc in a three-dimensional scene is most likely to appear as an ellipse in a projection. In addition, crossing curves in the sketch do not necessarily represent curves that actually meet. Systems for interpreting sketches as 3D scenes must confront greater problems and are less common (Lamb and Bandopadhay, 1990; Marti et al, 1993).

4.7 CAD Modeling of Components

4.7.1. Different Views of the Frame/Table

Length = 24 in

Width = 18 in

Height =36 in

Hole for disk = 8.3 in

Figure: 4.7.1

4.7.2. Different Views of force plunger:

Length = 2 in

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Width = 2.3 in

Figure: 4.7.2

4.7.3. Different Views of bending beam load cell:

Length = 4 in

Width = 1.7 in

Figure: 4.7.3

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4.7.4. Different Views of S-beam load cell:

Length = 3 in

Width = 3 in

Thickness = 0.7 in

Figure 4.7.4

4.7.5. Different Views of specimen holder and specimen:

Length of specimen holder = 2 in

Diameter of specimen = 2 in

Length of specimen = 3 in

Diameter of specimen = 0.5

Figure: 4.5.5

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4.7.6. Different Views of Invertor:

Length = 4 in

Width = 3 in

Thickness = 2.5 in

Figure 4.7.6

4.7.7. Different Views of motor-shaft-vessel:

Diameter of vessel= 8.3 in

Shaft length = 4 in

Diameter = 0.8 in

Figure: 4.7.7

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4.7.8. Bolt and Nut:

Figure: 4.7.8

4.7.9 Final Assembled model:

Figure: 4.7.9

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Chapter-5

FABRICATION

5.1 Introduction

Fabrication is the raw of stock material and turning it into a part use in an assembly process. Cutting, Machining, Shearing, Welding etc are the most common fabrications.

The fabrication of wear testing machine involves the manufacturing processes. Each part needs different processes which are to be carried out stepwise and brief description of each process is follow.

5.2 Manufacturing

Manufacturing process are the steps through which raw materials are transformed into a final product. The manufacturing process begins with the product design, and materials specification from which the product is made. These materials are then modified through manufacturing processes to become the required part.

Manufacturing is the production of for use or sale using labour and
machines, tools, chemical and biological processing, or formulation. The term
may refer to a range of human activity, from handicraft to high tech, but is most
commonly applied to industrial production, in which raw materials are
transformed into finished goods on a large scale. The manufacturing sector is

closely connected with engineering and industrial design.

5.2.1 Metal Fabrication

Metal fabrication is the building of metal structures by cutting, bending, and assembling processes. It is a value added process that involves the construction of machines and structures from various raw materials. A fab shop will bid on a job, usually based on the engineering drawings, and if awarded the contract will build the product. Large fab shops will employ a multitude of value added processes in one plant or facility including welding, cutting, forming and machining. These large fab shops offer additional value to their customers by limiting the need for

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purchasing personnel to locate multiple vendors for different services. Metal fabrication jobs usually start with shop drawings including precise measurements then move to the fabrication stage and finally to the installation of the final project.

5.2.2 Machining
Machining is any of various processes in which a piece of raw material is cut into
a desired final shape and size by a controlled material-removal process.
Machining is a part of the manufacture of many metal products, but it can also be
used on materials such as wood, plastic, ceramic, and composites. A room,
building, or company where machining is done is called a machine shop.

5.2.3 Cutting
Cutting is the separation of a physical object, into two or more portions, through
the application of an acutely directed force. Implements commonly used for
cutting are the knife and saw. However, any sufficiently sharp object is capable of

cutting if it has a hardness sufficiently larger than the object being cut, and if it is applied with sufficient force. Even liquids can be used to cut things when applied

with sufficient force. Cutting is a compressive and shearing phenomenon, and
occurs only when the total stress generated by the cutting implement exceeds the
ultimate strength of the material of the object being cut. The simplest applicable
equation is stress = force/area: The stress generated by a cutting implement is
directly proportional to the force with which it is applied, and inversely

proportional to the area of contact. Hence, the smaller the area (i.e., the sharper the cutting implement), the less force is needed to cut something. It is generally seen that cutting edges are thinner for cutting soft materials and thicker for harder materials.

5.2.4 Drilling

Drilling is a cutting process that uses a drill bit to cut a hole of circular cross-section in solid materials. The drill bit is usually a rotary cutting tool, often multipoint. The bit is pressed against the work piece and rotated at rates from

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hundreds to thousands of revolutions per minute. This forces the cutting edge against the work piece, cutting off chips from the hole as it is drilled.

5.2.4.1 Drilling in Metals

Under normal usage, swarf is carried up and away from the tip of the drill bit by the fluting of the drill bit. The cutting edges produce more chips which continue the movement of the chips outwards from the hole. This is successful until the chips pack too tightly, either because of deeper than normal holes or insufficient backing off (removing the drill slightly or totally from the hole while drilling). Cutting fluid is sometimes used to ease this problem and to prolong the tool’s life by cooling and lubricating the tip and chip flow. Coolant may be introduced via holes through the drill shank, which is common when using a gun drill. When cutting aluminium in particular, cutting fluid helps ensure a smooth and accurate hole while preventing the metal from grabbing the drill bit in the process of drilling the hole.

Figure 5.2.4: Drilling in metals.

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5.2.5 Grinding

Grinding is an abrasive

machining process

that

uses

a grinding

wheel as

the cutting tool.

A wide variety of machines are used for grinding:

• Hand-cranked knife-sharpening stones (grindstones)

• Handheld power tools such as angle grinders and die grinders

• Various kinds of expensive industrial machine tools called grinding machines

• Bench grinders often found in residential garages and basements

Grinding practice is a large and diverse area of manufacturing and tool making. It can produce very fine finishes and very accurate dimensions; yet in mass production contexts it can also rough out large volumes of metal quite rapidly. It is usually better suited to the machining of very hard materials than is “regular” machining (that is, cutting larger chips with cutting tools such as tool bits or milling cutters), and until recent decades it was the only practical way to machine such materials as hardened steels. Compared to “regular” machining, it is usually better suited to taking very shallow cuts, such as reducing a shaft?s diameter by half a thousandth of an inch or 12.7 ?m.

Grinding is a subset of cutting, as grinding is a true metal-cutting process. Each grain of abrasive functions as a microscopic single-point cutting edge, and shears a tiny chip that is analogous to what would conventionally be called a “cut” chip (turning, milling, drilling, tapping, etc. However, among people who work in the machining fields, the term cutting is often understood to refer to the macroscopic cutting operations, and grinding is often mentally categorized as a “separate” process. Grinding is a subset of cutting.

5.2.6 Boring

Boring is the process of enlarging a hole that has already been drilled by means of a single-point cutting tool. Boring is used to achieve greater accuracy of the

diameter of a hole, and can be used to cut a tapered hole. Boring can be viewed as

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the internal-diameter counterpart to turning, which cuts external diameters.

Figure 5.2.6 Boring in mild steel disk

5.2.7 Welding

Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing fusion, which is distinct from lower temperature

metal-joining Welding is a hazardous undertaking and precautions are required to avoid burns, electric shock, vision damage, inhalation of poisonous gases and fumes, and exposure to intense ultraviolet radiation.

Until the end of the 19th century, the only welding process was forge welding, which blacksmiths had used for centuries to join iron and steel by heating and hammering. Arc welding and oxy fuel welding were among the first processes to develop late in the century, and electric resistance welding followed soon after. Welding technology advanced quickly during the early 20th century as the world wars drove the demand for reliable and inexpensive joining methods. Following the wars, several modern welding techniques were developed, including manual methods like SMAW (Shielded metal arc welding), now one of the most popular welding methods, as well as semi-automatic and automatic processes such as GMAW, SAW, FCAW and ESW. Developments continued with the invention of laser beam welding, electron beam welding, magnetic pulse welding (MPW),

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and friction stir welding in the latter half of the century. Today, the science continues to advance.

Techniques such as brazing and soldering, which do not melt the base metal. In addition to melting the base metal, a filler material is typically added to the joint to form a pool of molten material (the weld pool) that cools to form a joint that is

usually stronger than the base material. Pressure may also be
used in conjunction
with heat,
or by itself, to produce a weld. Many different energy sources can be

used for welding, including a gas flame, an electric arc,
a laser,
an electron

beam, friction,
and ultrasound.
While often an industrial process, welding may be
performed in many different environments, including in open air, under
water, and

in outer space.

5.2.7.1 Electric ARC Welding
Arc welding is a process that is used to join metal to metal by using electricity to

create enough heat to melt metal, and the melted metals when cool result in a binding of the metals. It is a type of welding that uses a welding power supply to create an electric arc between an electrode and the base material to melt the metals

at the welding point. They can use either direct (DC) or alternating (AC) current,
and consumable or non-consumable electrodes. Arc welding processes may
be manual, semi-automatic, or fully automated. Arc welding is much important
tool for joining two or more metals.

5.2.7.2 Gas Metal ARC Welding

Gas metal arc welding is a welding process in which an electric arc forms between

a consumable wire electrode and the work piece metal(s), which heats the work piece metal(s), causing them to melt and join.

5.2.7.3 Gas Welding

The most common gas welding process is oxyacetylene welding. It is one of the oldest welding process, but in recent years it has become less popular in industrial applications. It is still widely used for welding pipes and tubes, as well as repair work.

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5.3 FABRICATION OF BASE FRAME

5.3.1 Materials Used

? Mild steel

? Stainless steel covering sheet

Mild Steel

Mild steel (steel containing a small percentage of carbon, strong and tough but not readily tempered (improve the hardness and elasticity of (steel or other metal) by reheating and then cooling it)), also known as plain-carbon steel and low-carbon

steel. Mild steel contains approximately 0.05–0.25%carbon making it malleable
and ductile. Mild steel has a relatively low tensile strength, but it is cheap and
easy to form. The density of mild steel is approximately
7.85 g/cm3 (7850 kg/m3 or 0.284 lb/in3) and the Young’s modulus is 200 GPa
(29,000,000 psi).
Stainless Steel
Stainless steel is a steel alloy with a minimum of 10.5% chromium content by
mass. Stainless steel does not readily corrode, rust or stain with water as ordinary
steel does. There are various grades and surface finishes of stainless steel to suit

the environment the alloy must endure. Stainless steel is used where both the properties of steel and corrosion resistance are required. Stainless steel differs from carbon steel by the amount of chromium present.

5.3.2 Stepwise Process

Step wise processes performed during the fabrication of frame:

? Cutting

? Welding

? Drilling

? Boring

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Cutting:

Cut 36 inches four mild steel rods for base frame legs. And two rods for motor arrangement whose displacement is 8.5 in. Also cut 24 inches in length and 18 inches in width mild steel for upper portion of base frame.

Welding:

Weld the different pieces of metal sheet to form a base frame.

Drilling:

Drill the holes for disk in upper portion of table, also drill the holes for shaft of motor and disk.

Boring:

Enlarge the existing holes of the frame.

Figure 5.3: Base frame.

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5.4 FABRICATION OF BASE FOR ROTATING DISK

5.4.1 Material Used

? Plastic

5.4.2 Stepwise Process

Step wise processes performed during the fabrication of base for rotating disk:

? Cutting

? Drilling

Cutting:

Cut a plastic of 8.3 inches for base of rotating disk.

Drlling:

Drill the hole for shaft of rotating disk.

Figure 5.4: Base for rotating disk.

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5.5 FABRICATION OF ROTATING DISK

5.5.1 Material Used

High speed mild steel.

5.5.2 Stepwise Process

Step wise processes performed during the fabrication of rotating disk:

? Cutting

? Welding

? Drilling

Cutting: Cut mild steel in circular disk form of 5.5 inches.

Welding: Weld a shaft on the lower surface of disk.

Drilling: Drill a hole in the base of rotating disk for shat of disk.

Figure 5.5: Rotating disk

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5.6 FABRICATION OF SHAFT

5.6.1 Material

? Stainless steel-304

Table 5.6: Composition of SS (304)

Z Wt (%)

C 0.8

Cr 18

Fe 74

Ni 10

Si 1

5.6.2

Step wise processes performed during the fabrication of rotating disk:

? Facing

? Turning

? Cutting

? Threading

Length 8.5in
Diameter 0.8in

Threading Pitch: 0.1in
Depth of Cut:0.12in

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DIMENSIONS OF SHAFT:

Figure 5.6 Shaft.

5.7 FABRICATION OF COLOUMNS

5.7.1 Material Used

? Stainless steel

5.7.2 Stepwise Process

Step wise processes performed during the fabrication of columns:

? Cutting

? Drilling

? Milling

? Threading

Cutting: Cut stainless steel in circular column of 18 inches.

Drilling: Drill two holes in the base from for connecting columns with base frame.

Milling: Use milling process to remove extra material from columns.

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Threading:

We make 5 inches threads in the upper and lower part of the circular columns.

Which make the columns adjustable to our requirements.

Fig 5.7: Columns

5.8 FABRICATION OF WATER STORAGE TANK

5.8.1 Material Used

? MILD STEEL

5.8.2 Stepwise Process

Step wise processes performed during the fabrication of water storage tank:

? Cutting

? Welding

Cutting:

Cut mild steel in almost cubic form. Whose length is 12 inches and width and height of 06 inches.

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Welding:

Join all the parts which are cut for water storage tank through welding process.

Figure 5.8: Water storage tank

5.9 FABRICATION OF BEAM

5.9.1 Material Used

? Stainless steel

5.9.2 Stepwise Process

Step wise processes performed during the fabrication of beam:

? Cutting

? Grinding

? Drilling

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5.9.3 Dimensions of Beam

Table 5.9: Dimension of Beam

Thickness 0.5 inches

Width 2 inches

Length 24 inches

5.10 FABRICATION OF SUPPORTING GRIP FOR S BEAM AND BENDING BEAM SENSORS

5.10.1: Material

? Brass

5.10.2:

Step wise processes performed during the fabrication of beam:

? CUTTING

? MILLING

? FACING.

Cutting: Cut some portion from brass rod.

Milling: Perform milling operation on brass rod to get our required gripping tool.

Facing: Perform facing operation to plan the surface of the gripping tool.

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Figure 5.10: Grip for S Beam and Bending beam sensors

5.11 FABRICATION OF SPECIEMENS TO BE TESTED

5.11.1 Material

? Brass rod: (diameter=0.9 in)

? Aluminium rod:(diameter=0.97in)

? Copper rod:(diameter=0.9 in)

5.12 Final Assembly

The motor is mounted on the base frame through nuts and bolts. Assembly of all the components is mostly done with welding, nuts and bolts. In assembling all the components one thing is kept in mind that all the components must be aligned otherwise well face a lot of difficulties in motor running speed, motor power and readings from the Sensors. The motor shaft and disc shaft is connected through coupling device. The disc is mounted on the shaft by making threads on it and is fixed through nut. Put plunger on the beam through nuts. Then connect the plunger and bending beam sensor (to find bending force), and then connect bending beam sensor to S Beam sensor (to find normal force), and then connect S

58

Beam sensor to drill chuck and put specimen (which is to be tested) in drill chuck.

Which is now in touch with a rotating disk.

Figure 5.12: Final Assembly of wear testing machine

5.13 Summary

Manufacturing involves relatively less skill. It relies on a much fewer number of skilled workers to setup the operation (fixtures, Work instructions, standard times). So that a comparatively larger number of unskilled workers can produce parts in the same quantity and quality.

Fabrications are usually not the end product being made. My company purchases many fabricated parts and then welds the parts together to make a chassis, cab, and loader arms. These parts are then assembled into a skid steer loader or a compact track loader. The loaders are the end product while the fabricated parts and the weldments are all considered fabricated components.

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Chapter-6

DATA ACQUISITION SYSTEM & SENSORS

CALIBRATION

The data acquisition system is the brain of the experiment and has the ability to convert the voltage output of the transducers into a usable unit such as force in grams or newton. This chapter will explain the selection of DAQ equipment used, as well as a brief guide to the initial installation, connecting, calibrating and general user interface for taking real-time measurements.

6.1 Selection of DAQ Equipment’s:

The data acquisition hardware/software provider chosen for this experiment was Arduino Pak. They were able to supply all of the components needed in order to extract information from a transducer and convert to a usable format for display and analysis. We design our own DAQ system by using Arduino and amplifiers because of their low cost and easiness in use. The items listed below are the products purchased that were used to produce the data found in this experiment:

6.1.1 Arduino Mega 2560:

Arduino is an open-source electronics platform based on easy-to-use hardware and software. Arduino boards are able to read inputs – light on a sensor, a finger on a button, or a Twitter message – and turn it into an output – activating a motor, turning on an LED, publishing something online. You can tell your board what to do by sending a set of instructions to the microcontroller on the board. To do so you use the Arduino programming language (based on Wiring), and the Arduino Software (IDE), based on Processing.

Arduino boards are relatively inexpensive compared to other microcontroller platforms. The least expensive version of the Arduino module can be assembled by hand, and even the pre-assembled Arduino modules cost less than Rs.2500. The Arduino Software (IDE) runs on Windows, Macintosh OSX, and Linux operating systems.

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The Arduino software is published as open source tools, available for extension by experienced programmers. The language can be expanded through C++ libraries. Arduino Mega 2560 is shown in the Figure 6.1.1

Figure 6.1.1: Arduino Mega 2560

6.1.2. Amplifier:

An amplifier, electronic amplifier is an electronic device that can increase the power of a signal (a time-varying voltage or current). An amplifier uses electric power from a power supply to increase the amplitude of a signal. The amplifier we select to use is HX711. Based on Avia Semiconductor?s patented Technology , HX711 is a precision 24-bit analog to-digital converter (ADC) designed for weight scale and industrial control applications to interface directly with a bridge sensor. An “HX711” amplifier is shown in the Figure: 6.1.3

Figure 6.1.3.: HX711 Amplifier

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6.1.2.1 Datasheet: HX711

Most Load cell have four wires red, black, green and white. On HX711 board you will find E+, E-, A+, A- and B+, B- connections. Connect load cell with it as follow:

Red wire to E+

Black wire to E-

Green wire to A-

White wire to A+

6.1.3. Wires:

We used special wires “male to male” and “male to female” to connect amplifier to Arduino. These wires are easy to use to connect Amplifier and Arduino. These are shown in the Figure: and Figure 6.1.3.:

Figure 6.1.3(a): Male to Male Wires Figure 6.1.3(b): Male to Female Wires

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6.2. Load Cell connections to HX711 and Arduino:

The load cell connection to HX711 and Arduino is shown in the Figure 6.2 :

Figure 6.2 : Load cell connections to HX711 and Arduino.

The Red wire from the load cell is connected to E+ of HX711.

The Black wire from the Load Cell is connected to E- of HX711.

Similarly Green with A- and White with A+.

The Amplifier is connected to Arduino through “Male to Male” wires.

Pin #3 of Arduino is connected to Pin DT and Pin #2 with Sck respectively.

The VCC of amplifier is provided with 5v and Grounds Pins (GND) are connected to each other.

In this connection we use Pins (3, 2) because we will use these 2 Pins later in Programming.

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6.3. Program Coding:

For the coding we need HX711 Library to compile and run the code. We must have the “HX711.h” and ” HX711.cpp” and Basic codes all in the same tabs Bar. As shown in the Figure 6.3.:

Figure 6.3. : Arduino Coding Program Setup.

The Setup shown in the figure is for S beam sensor, The Library Code for both S-Beam Sensor and Bending-Beam Sensor is same, only the Basic Code is different.

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6.4. S-Beam Sensor Calibration

6.4.1. Basic Code For S-Beam Sensor:

#include “HX711.h”

HX711 cell (3, 2);

void setup()

{

Serial.begin(9600);

}

long val =0;

float count =0;

void loop ()

{

count = count +1;

//val = ((count – 1)/count)*val + (1/count)* cell.read(); val = 0.6*val + 0.4*cell.read();

Serial.println (( val – 8388869 )/10929.0f*500); //zero 8388869 }

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6.4.2. HX711 Library Setup:

a) HX711.h

#ifndef HX711_h

#define HX711_h

#if ARDUINO ;= 100

#include “Arduino.h”

#else

#include “WProgram.h”

#endif

class HX711

{

private:

byte PD_SCK; // Power Down and Serial Clock Input Pin

byte DOUT; // Serial Data Output Pin

byte GAIN; // amplification factor

long OFFSET; // used for tare weight

float SCALE; // used to return weight in grams, kg, ounces, whatever

public:

// define clock and data pin, channel, and gain factor

// channel selection is made by passing the appropriate gain: 128 or 64 for channel A, 32 for channel B

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// gain: 128 or 64 for channel A; channel B works with 32 gain factor only HX711(byte dout, byte pd_sck, byte gain = 128);

virtual ~HX711();

// check if HX711 is ready

// from the datasheet: When output data is not ready for retrieval, digital output pin DOUT is high. Serial clock

// input PD_SCK should be low. When DOUT goes to low, it indicates data is ready for retrieval.

// set the gain factor; takes effect only after a call to read()

// channel A can be set for a 128 or 64 gain; channel B has a fixed 32 gain

// depending on the parameter, the channel is also set to either A or B void set_gain(byte gain = 128);

// waits for the chip to be ready and returns a reading

long read();

// returns an average reading; times = how many times to read long read_average(byte times = 10);

// returns (read_average() – OFFSET), that is the current value without the tare weight; times = how many readings to do

double get_value(byte times = 1);

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// returns get_value() divided by SCALE, that is the raw value divided by a value obtained via calibration

// times = how many readings to do

float get_units(byte times = 1);

// set the OFFSET value for tare weight; times = how many times to read the tare value

void tare(byte times = 10);

// set the SCALE value; this value is used to convert the raw data to “human readable” data (measure units)

void set_scale(float scale = 1.f);

// set OFFSET, the value that’s subtracted from the actual reading (tare weight) void set_offset(long offset = 0);

// puts the chip into power down mode

void power_down();

// wakes up the chip after power down mode void power_up();

};

#endif /* HX711_h */

b) HX711.cpp:

#include

#include “HX711.h”

68

HX711::HX711(byte dout, byte pd_sck, byte gain) {

PD_SCK = pd_sck;

DOUT = dout;

pinMode(PD_SCK, OUTPUT);

pinMode(DOUT, INPUT);

set_gain(gain);

}

HX711::~HX711() {

}

bool HX711::is_ready() {

return digitalRead(DOUT) == LOW;

}

void HX711::set_gain(byte gain) {

switch (gain) {

case 128: // channel A, gain factor 128

GAIN = 1;

break;

case 64: // channel A, gain factor 64

GAIN = 3;

break;

69

case 32: // channel B, gain factor 32

GAIN = 2;

break;

}

digitalWrite(PD_SCK, LOW);

read();

}

long HX711::read() {

// wait for the chip to become ready while (!is_ready());

byte data3;

// pulse the clock pin 24 times to read the data for (byte j = 3; j–;) {

for (char i = 8; i–;) { digitalWrite(PD_SCK, HIGH); bitWrite(dataj, i, digitalRead(DOUT)); digitalWrite(PD_SCK, LOW);
}

}

70

// set the channel and the gain factor for the next reading using the clock pin for (int i = 0; i < GAIN; i++) {

digitalWrite(PD_SCK, HIGH); digitalWrite(PD_SCK, LOW);
}

data2 ^= 0x80;

return ((uint32_t) data2