working of universal testing machine (utm

7/31/2019 Working of Universal Testing Machine (UTM

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MAHARASHTRA STATE BOARD OF TECHNICAL EDUCATION o 9

Strength of Materials (9024) Experiment No. 2

Experiment No. 2

1.0 TITLE :

To understand the working of Universal Testing Machine (UTM)

for various tests.

2.0 PRIOR CONCEPTS:

Force, Load, Tensile force, Compressive force, tangential force.

3.0 NEW CONCEPTS:

Proposition 1: Gradual Load

Load starting from zero and applied with constant increment up to required value.

Concept Structure :

Proposition 2 : Types of Loads

Axial Load : Load acting along longitudinal axis of the member. Tensile load causes elongationand Compressive load causes contraction of the member.

Transverse Load : Load acting perpendicular to longitudinal axis of the member and causes

bending of the member.

Shear Load : Load acting tangentially along a surface of the member and causes cutting likeeffect.


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10 o MAHARASHTRA STATE BOARD OF TECHNICAL EDUCATION

Experiment No. 2 Strength of Materials (9024)

Concept Structure :

Proposition No. 3 : Universal Testing Machine

The machine comprises of two basic units, one is the Control unit and other is loading unit.

Control unit : The load is applied and recorded by this unit. The load is applied with control

valve and released by release valve. The load is applied with the help of hydraulic pressure.

Loading unit : In this unit actual loading of the specimen takes place - consists of three

crossheads namely upper head, middle head and lower head. Using appropriate crossheads

tensile, compressive, shear, bending load with the help of different attachment can be applied.


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Concept Structure :

4.0 LEARNING OBJECTIVES:

Intellectual skills:

To study different parts of UTM & their function.

To know working principle of UTM.

To select proper crossheads for particular type of load application.

Motor skills:

Ability to handle different fixtures and attachments.

Ability to observe cross head movements.

Ability to measure loads on load dial gauges.

5.0 APPARATUS AND MATERIALS

Apparatus: Universal Testing Machine(UTM), tension grips, shear attachment, bending attachment,compression plates, hardness attachment.

Materials: Specimen of timber with standard dimensions.

Learning material : Brochure supplied with the machine.


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6.0 DESIGN OF EXPERIMENT:

Label the numbered parts and state their functions.


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7.0 STEPWISE PROCEDURE:

1. Ensure that all the switches and main switches are put on.

2. Ensure that release valve and the control valve mounted on control unit are closed.

3. Move the middle crosshead of loading unit up and down with the help of mechanical motors,there by the space from upper crosshead and middle crosshead decreases or increases.This helps us to adjust the gap between crossheads as per length of the specimen.

4. Now put the machine on and open the control valve slowly. Observe the upward movementof upper and lower crosshead. The middle crosshead will remain stationary. One can control

the movement speed of crosshead using control valve.


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5. As soon as the control valve is opened observe the changes on load dial/display along withdisplacement dial/display. The value for load will increase for some time and then remainstationary but the values for displacement will go on increasing. This load value is nothingbut the dead weight of lower crosshead.

6. Now make the load reading zero with the help of tare switch. Shut down the machine. Close

the control valve and open the release valve.7. Note the backflow of hydraulic oil and observe slow lowering of the crosshead. The value for

load will decrease for some time and then become negative and the values for displacementwill go on decreasing. This is termed as adjustment of dead weight of crosshead. Teachershall explain the disadvantages if this adjustment is not done properly.

8. Put the timber specimen between middle and lower crosshead. Ensure that there is a smallgap within crossheads and the specimen. After selecting suitable range on load dial gaugeclose the release valve and slowly open the control valve.

9. Note the readings of load at three different instants.

10. Apply the load till failure of the specimen takes place, this is the maximum load or failureload generally denoted by P.

11. Put off the machine. Close the control valve and open the release valve.

8.0 OBSERVATIONS :

Table for load and displacement

9.0 QUESTIONS:

Write answers to Q ......, Q ......, Q ......, Q ...... (Teacher shall allot the question)

1. Enlist the tests to be performed on the universal testing machine.

2. State the operational principle of UTM.

3. Why release valve is opened, after the machine is put off? Give reason.

4. How to adjust the dead weight of crosshead?

5. What will happen if the machine is put on keeping the release valve open?

6. Why is it necessary to adjust the dead weight of crossheads? Give reason.

7. State the type of oil used for UTM available in your lab.8. Can you perform Rockwell Hardness Test on UTM.

9. How wire ropes and LT stay wires are fixed in the jaws of UTM.

10. What will happen if dummy pointer of a UTM is missing?


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(Space for answer)

Signature of Teacher

working of universal testing machine (utm

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