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United Arab Emirates University College of Engineering Mechanical Engineering Department Graduation Project 1 . Tribology Testing Machine. Tribo-Testing Machine Design & Setup (Pin-On-Disk Tester). Presented by : Khalid Al-Ali200005048 Bader Al-Ali200000186

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Tribology testing machine l.jpg

United Arab Emirates University

College of Engineering

Mechanical Engineering Department

Graduation Project 1

Tribology Testing Machine

Tribo-Testing Machine Design & Setup (Pin-On-Disk Tester)

Presented by : Khalid Al-Ali200005048

Bader Al-Ali200000186

Fahed Araiqat 199900324

Date : 25th May 2005


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Executive Summary

  • The main objectives of this project are:

    • To establish a foundation for future experimental research in the UAE university.

    • Such a machine will provide the chance to investigate the followings:

      • Tribological performance of different coatings.

      • Wear mechanisms for different surfaces.

      • Impact of a surface roughness on friction and wear.

      • Study different lubricants tribological properties.

      • Scuffing characteristics of different surfaces


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Executive Summary

  • The major executed tasks could be categorized into;

    • searching tasks

    • designing tasks

    • analyzing or reporting tasks.

  • The major executed tasks during GP1 course were;

    • Problem definition, familiarization with tribology terminology and tribo-testing machines.

    • Develop a design layout, come up with at least two different designs, analyze them (in terms of cost, efficiency, etc), and decide on the best design.

    • Materials selections and getting price quotes for different machine components.

    • Preparation of Engineering CAD drawings.


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Time Table (Gantt Chart)


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What is Tribology

  • Tribology is defined as “the science of interacting surfaces in relative motion”.

  • It is the study of:

    • Friction

    • wear

    • Lubrication

  • In any machine there are lots of component parts that operate by rubbing together (bearings, gears, cams, tires, brakes, piston ring …etc)


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What is Tribology

  • Sometimes it is desirable to have low friction, to save energy, or high friction, as in the case of brakes.

  • Tribology finds applications in all industrial sectors including;

    • Aerospace

    • Automotive

    • Construction

    • Biomedical

    • Textile

    • Optical

    • Mining

    • Petrochemical

  • machinery & tools

  • paper, transport

  • power generation

  • Microelectronics

  • Military

  • Metallurgy

  • agriculture and food industries.


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When Two Surfaces Are Pressed Together

  • Surfaces may look smooth, but on a microscopic scale they are rough.

  • If we want to slide one surface over the other then we have to apply a force to break those junctions.


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Keeping the Surfaces Apart (Lubrication)

  • Definition:introduction of a substance between the contact surfaces of moving parts to reduce friction and to dissipate heat.

  • The selection of the best lubricant and understanding the mechanism by which it acts to separate surfaces in a bearing or other machine components is a major area for study in tribology.


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When Things Wear Out

  • Definition:If one surface is slid over another then the asperities come into contact and there is a possibility that wear can occur.

  • The breaking of the entire little junction can cause material removal

  • One of the main reasons for frequent change of car engine oil is that it becomes contaminated with hard debris particles that can wear out the engine components.


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Surface Engineering

  • Definition: "Changing the properties of the surface of a material to give performance which cannot be achieved by the surface layer or bulk alone"

  • Surface Engineering Processes

    • Mechanical treatment (e.g. peening, shot blasting)

    • Surface transformation (e.g. induction hardening, laser treatment)

    • Surface composition changes (e.g. thermo chemical treatment, ion implantation)

    • Chemical treatment (e.g. conversion coatings)

    • Coating (e.g. painting, spraying, plating, vapor deposition)

    • Surface activation (etching, plasma treatment of polymers)


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Tribo-Testing Machine

  • Tribology deals with engineering surfaces, so

    how can it be tested ?

  • Different types of Tribo-Testing Machines

    • Scratch testing machine

    • Abrasion testing machine

    • Grease noise tester

    • Multi-Specimen Test Machine

    • Tapping Torque Test Machine

    • Timken Test Machine

    • The pin & vee block tester


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Pin-On-Disc Tester

  • The Pin-On-Disk Tester is used to test the friction and wear characteristics.

  • It is used for a wide variety of materials including metals, polymers, composites, ceramics, lubricants, cutting fluids, abrasive slurries, coatings, and heat-treated samples.

  • The test is performed by rotating a counter-face test disk against a stationary test specimen pin.

  • Wear, friction force, and interface temperature can be monitored using TriboDATA (Data Acquisition System)


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Mission

  • The aim of the project is todesign, set up a pin-on-disktribo-testing machine and to study the tribological behavior for some engineering surfaces.

  • The experimental evaluation is done by rotating a counter-face flat against a stationary pin/ball.

  • Friction force can be monitored using Data Acquisition Software.

  • The normal load, rotational speed,

    and wear track diameter can be

    adjusted.


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Tribo-Testing Machine (TTM) Configuration

  • The basic TTM components are:

    • Geared DC motor or (DC motor + Gear box).

    • Pin holder.

    • Flat holder.

    • Strain Gauge (or Load Cell).

    • Disk.

    • Weight.

    • PC

    • Data Acquisition System.

  • Some other points should be considered like the way that the machine would work, which part is moving and which part is not.


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Tribo-Testing Machine (TTM) Configuration

  • The TTM consists of a base with a flat-holder mounted on it, and connected to a DC motor.

  • The base will be made of steel bars covered with Aluminum sheet.

  • The pin holder will be made of steel, and connected to a cylindrical steel piece that moves freely about a bearing.

  • The pin holder is pressing against a stationary load cell that will detect the frictional force in the form of electrical signal that will be amplified and sent to the computer via Data Acquisition system.


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S-type gauge

Pin Holder

Handle

Geared DC motor

Disk

Design Alternatives

Design No. 1

  • The design is focusing on moving the flat holder


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The gauge

Weight

Pin Holder

Handle

Disk

Geared DC Motor case

Design Alternatives

Design No. 2

  • The design is focusing on moving the pin holder


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Analyses of the two Different Designs


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Decide the Best Design

  • After the comparison between the two previous designs, it is evidently design No.2 is more suitable decision.

  • It has more advantages compared to design No.1


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Decide the Best Design

  • The foremost merits of design No.2 are;

    • More accurate and precise

    • Easy to fabricate

    • Easy to use

    • Easy to maintain

    • More attractive shape

  • While, the demerits of design No.2 are;

    • Larger in Size (twice design 1 in size)

    • Relatively high in cost

    • Heavier


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In order to Overcome the Demerits

  • The size and the materials have an influence affect on machine cost and weight.

  • Motor, DAQ, Load cell, and such these items are actually excluded from the comparison.

  • These items are considered to take the most of budget cost. Thus, assumed to be similar for both designs.


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In order to Overcome the Demerits

  • The cost of design No.2 is mainly affected by body components materials cost.

  • This means that;

    • Body components materials is less in cost compared with other items (motor, DAQ, load cell)

    • There are other alternatives of choosing materials. Such these approaches are followed to improve design No.2 in terms of cost and weight.


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Materials Selection

  • The specification of the material is one of the most important tasks for a designer

  • There are a lot of points the designer should takes on his mind before taking the decision like:

    • The functions of the component.

    • The component's shape.

    • The material from which the component is to be made.

    • The manufacturing process used to produce the component.


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Materials Selection

  • Some Factors are important for Materials Selection;

    • The component under which environment is operated.

    • The nature of the forces applied to the component.

    • The allowable deformation of the component at critical points.

    • Physical size and weight of the component.

    • The manufacturing process available.

    • Cost


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Component Materials

Component (Pin-On-Disc body)

  • The body of the Tribo-testing machine (which is consists of the base, pin holder, Flat holder, the handle and DC motor case) usually will be made of Aluminum and steel Alloys.

    Component (pin ball)

  • The pin ball which is subjected to the disk can be made of different kinds of steel like high speed steel (HSS), austenitic stainless steel (ASS), M50, 440C…etc.

    Component (disk)

  • The disk can be made of high speed steel (HSS), austenitic stainless steel (ASS), H13, Polymer…etc.


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Pin-On-Disc Specifications

  • Technical specification for pin on disk according to ASME

    • Rotational speed:10-200 rpm

    • Equivalent:20-420 mm/s

    • Track radius:20mm

    • Pin load range:up to 40 N

    • Friction sensing range:up to 50 N

    • Disk dimensions:50 mm diameter * 10 mm thick

    • Pin dimensions:4 mm diameter * 25 mm long (minimum)


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Description of Items & their Estimated Costs

1- Materials

  • All Dimensions in mm unless otherwised specified

  • t = thickness, Ф = diameter, L = Length


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Description of Items & their Estimated Costs

2- DC Motor

  • The advantages of direct current motor are summarized here:

    • The speed is adjusted by use of a simple rheostat.

    • The direction of rotation is reversible

    • Torque can be controlled by varying the current applied to the motor.

    • Dynamic braking can be obtained by reversing the polarity of the power while the motor is rotating.

    • DC motors typically have quick response, accelerated quickly when voltage is changed


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DC Motor Selection

  • There are three methods of selecting motor

    • DC motor; Both Gear box and Variable speed controller are missed.

    • Geared DC motor; Variable speed controller is missed.

    • Variable Speed Drive (VSD) Geared DC Motor.


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DC Motor Selection

How much is the DC motor power?

  • According to the technical specifications, the power could be calculated.


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Example: DC Motor Selection


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DC Motor Selection


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DC Motor Selection

  • The best choice for motor was entrapped between geared DC motor, and VSD DC


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DC Motor Control

  • DC Motor speed is adjustable by use of a simple rheostat to adjust the voltage applied to the motor.

Schematic diagram of DC motor control


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DC Power

  • Three approaches are used to provide DC power;

    • Batteries:

    • Generators

    • Rectifiers

  • For TTM, the PC desktop rectifier of 12V is used as a DC power supplier for the DC motor.

  • In local markets, it cost only 50 Dhs.


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Description of Items & their Estimated Costs

3- Tachometer

  • The Tachometer is an instrument used for measuring the speed of a moving body or substance (shaft) in terms of RPM.


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Tachometer Selection


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Description of Items & their Estimated Costs

4- Load Cell

  • The load cell is responsible to convert the load that coming from the arm and caused by the material friction to a voltage or ohm signal.


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Load Cell Selection


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Description of Items & their Estimated Costs

5- Data Acquisition System

  • The signal that comes from the load cell will be treated and processed by the Data Acquisition system.

  • The Data Acquisition system consists of two main parts;

    • Hardware (card or USB - DAQ)

    • Software for analyzing the signals and get the results.


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Data Acquisition System Selection


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Description of Items & their Estimated Costs

6- Bearings

  • The need of bearings in our design exist in the pin holder to give it the ability of free movement without friction.


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Description of Items & their Estimated Costs

7- Amplifier

  • Amplifier is one of the items that used in the geared DC motor. The amplifier is used to enlarge the signal (usually from mV to V)


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Items Specifications and Dimensions

  • After selecting the best DC motor, DAQ and the load cell, the next step was to come with materials and items specifications.

  • This task was accomplished by contacting with the items companies.

  • The specifications are so important such that they provide us with the technical information and dimensions which is necessary for preparing Engineering CAD Drawings.


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Items Specifications and dimensions

1- DC Motor


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Items Specifications and dimensions

2- Load Cell


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Key

  • A key is used to connect a drive member such as a belt pulley, chain sprocket, or gear to or from the shaft.

  • The Type of key used in motor shaft is Woodruff key.

  • The specified key dimensions is W = 4mm & B = 7.5mm


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Engineering CAD Drawings


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Pin holder parts


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Arm


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Ball hook


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Disk


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Shaft


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Steel pin holder 1


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Base column


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Plate column


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Base


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Flat holder plate


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Steel pin holder 2


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Side View


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Top View


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Isometric View


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Pin-On-Disc Budget

  • The total tribo-testing machine budget is 4624.00 Dhs.

  • The total cost was exceeded the budget. It reached firstly, over 8000 Dhs. But this problem had been solved by the following points:

    • Minimizing the items cost.

    • Minimizing the volume of the machine

    • Looking for material solution.


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Conclusion & Recommendation

Impact of this research

  • Experiences in a real life design problem from start-to-finish, that will expose us to:

    • Project Planning

    • Materials Selections

    • Design Specifications

    • Hand-on experiences

    • Cost Minimization


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Conclusion & Recommendation

  • The budget of the Tribo-testing machine at the beginning was over Dhs 8000 and then it was minimized to be Dhs 4600.

  • This minimization it might increase the error, and affect the results and the accuracy of the machine.

  • For example, the using DC motor instead of VSD motor it might increase errors since the first one has the lower in cost, but it needs experimental work to calibrate the voltage with the speed.

  • it is recommended to make the budget appropriate with the design.


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Conclusion & Recommendation

  • The available resources in the college would be implemented in order to minimize the budget cost as much as possible.

  • The college resources could be integrated with machine body components manufacturing. This could be accomplished in the college workshop, since, some materials needed to be cut, welded, bended, and drilled.

  • Through, our research we found DC motors that have fixed speed. Our interest is to have a variable speed motor. This can be accomplished at our Control Lab in the ME Department.


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