Lab Test: Torsion Test Essay Sample

MEMORIAL UNIVERSITY OF NEWFOUNDLAND
Faculty OF ENGINEERING AND APPLIED SCIENCE

Technology: 4312

Mechanicss of Solids I

Lab Test # 4 – Torsion Test
Aim:
To transport out a tortuosity trial to devastation in order to find for a 1020 C steel rod specimen: 1. The modulus of rigidness. 2. The shear emphasis at the bound of proportionality. 3. The general features of the torsion. angle of turn relationship.

Mentions:
1. Hibbeler. R. C. “Mechanics of Materials” . Prentice-Hall. 7th Edition. 2. Instruction Bulletin of Tecquipment Ltd.

Material:
Mild Steel rod 6 millimeters diameter over 3? length ( overall length including hexagon ends = 5?” ) .

Equipments:
1. Tortuosity proving Machine and Torsiometer of Tecquipment Ltd. 2. Steel regulation and micron.

Theory:
From the general tortuosity theory for round specimen:

T G? = J cubic decimeter

where. T = Applied Torque ; J = Polar Second Moment of Area ; G = Modulus of Rigidity ; ? = Angle of Twist ( over length cubic decimeter ) ; l = Gauge Length. ( Nm ) ( mm2 ) ( N / mm2 ) ( radians ) ( millimeter )

Procedure:
1. Measure the overall length and trial diameter of the specimen. 2. Pull a line down the length of the trial subdivision of the specimen with a pencil ; this serves as a ocular assistance to the grade of turn being put on the specimen during lading. 3. Mount the specimen steadfastly in the tortuosity proving machine as indicated in the operating instructions – see subsequently. ( If the Torsiometer is to be used the fixed process should be carried as prescribed in the last portion the bulletin ) . For each increase of strain record the followers: ( a ) Angle of turn of the specimen ( ? ) in grades. ( B ) Applied torsion ( T ) ( degree Celsius ) Angle of turn over the 50 millimeter ( or 2. 0 in ) gage length in radians. as recorded by dial gage index ( ? ) radians. ( vitamin D ) When the elastic bound has been passed. go on to prove devastation with increasing increases of strain. entering for each strain increase. I ) two ) Angle of turn in grades ; Applied torsion.

Measurement:
1. Record the undermentioned – Initial diameter of specimen. – Final diameter of the specimen. Gauge length of the specimen. – Intial overall length of the specimen. Final overall of specimen. 2. Table the consequences as follows: Angle of Twist ( ? in grades ) Applied Torque T Angle of Twist Over the 50 millimeter

Consequence REQUIRED:
a. A graph of applied torsion ‘T’ against angle of turn ? as a base for the elastic part. Use the incline of the graph to find the value of modulus of rigidness. Besides from this graph find the torsion. and so cipher the shear emphasis at the bound of proportionality. B. A graph of applied torsion against angle of turn of the specimen as base. for the complete trial devastation. c. Discussions of mistakes involved in finding the modulus of rigidness utilizing the angle of turn from the machine dial. and compare the consequence obtained with the value found by utilizing the Torsiometer.

Fig. 1 Typical torsion-test specimens ; it is mounted between The two caputs of a testing machine and distorted.

Shear Stress

Slope = G= Shear Modulus Shear Strain ( Radians )

Fig. 2 The Shear Modulus is the Slope of the Linear Part of the Relationship between the Shear Stress and Shear Strain

OPERATING INSTRUCTIONS FOR THE TORSION TESTING MACHINE AND TORSIOMETER ( In Instruction Form )

1. Let the spring balance to hang free of the torsion arm and zero the balance by seting the little knurled prison guard at the top right manus of the balance.

2. Skid the hook of the balance under knife border on ~ torsion arm with the hook. Hanging free its lowest place. 3. Clamp the specimen into the jaws of the Torsion Machine and suit the torsiometer onto the specimen – a full history of this is found in the bulletin under chief header “Use and Operation of Torsiometer” . It is indispensable when utilizing the Torsion Machine to do certain that the whole length of the hexagon ends of the specimen are contained to the full within the chow jaws. Besides when the striving caput. specimen and Torsiometer are pushed along the bed so that the terminal of the specimen enters the headstock chow. come in the specimen into the chow until the light compaction spring behind the headstock chow merely begins to compact. 4. When the specimen has been steadfastly fixed in toxicant clamp the striving caput to the bed. 5. Turn the grip on the striving caput until the torsion arm is in the horizontal as shown by the spirit degree. 6. Turn the spring balance manus wheel to raise the balance until the hook on the balance is merely reaching the knife border on the torsion arm. This will be seen by motion of the spirit degree bubble.

Care should be exercised to transport out this operation so that the torsion arm and spring balance are “zeroed” . Both the balance manus wheel and striving caput manus wheel may hold to be adjusted together to obtain this status. 7. Zero the all right and class angular supplanting dials on the input and end product shafts of the striving caput. A knurled nut is provided behind each dial to lock the dial in place. 8. Zero the revolution counter – by turning the wingnut clockwise. 9. Adjust the arm on the Torsiometer so that it merely contacts the dial gage speculator. A knurled nut is provided for this intent and full description is found under the chief header “Use and Operation of the Torsiometer” in the bulletin. 10. Zero the dial gage index by revolving the dial. 11. The setup is now ready for usage and the remainder specimen can be loaded. in coveted increases. by turning the grip on the striving caput until the specimen has been rotated the needed figure of grades as shown on the all right angular supplanting dial on the machine. BEFORE TAKING TORQUE AND DIA GAUGE READINDS BRING THE TORQUE ARM BACK INTO HORIZONTAL BY TUI BALANCE HANDWHEEL. 12. When proving the more elastic stuffs the Torsiometer dial demands to be reset sporadically to zero due to the restriction on the speculator travel. See “Use and Operation of the Torsiometer” in the bulletin

Note: Make all computations ( manus written or typed on a computing machine ) legible and professional looking with sufficient borders. rubrics and good sum of “white infinite. ” The study must be produced the same manner as you would a work term study. You may include exposure every bit good.