CET345W_LAB#3

2. Procedure 1. With a micrometer caliper determine the mean diameter of the steel specimen near its mid-length. Assume the shearing proportional limit is 0.6 of the tensile proportional limit and the shearing modulus of rupture as equal to the tensile strength. Check with the instructor to ascertain tensile strength of the specimen. 2. Compute loading increments that will give at least 10 observations below the shearing proportional limit, several close together near the proportional limit, and at least 10 beyond the proportional limit. 3. Note the gage length and least reading of the troptometer. 4. Securely clamp the troptometer to the specimen. Note: Make certain that the axes of the troptometer and the test piece coincides and that the troptometer is in the proper position for ease of reading. Check to ensure that troptometer has a gage length of approximately 8", record L. 5. Insert the specimen into the two heads, and tighten the chuck grips. 6. Prior to turning the machine on apply a small amount of torque by the hand crank checking to ensure that the troptometer is properly indicating the angle of twist without slip. 7. Set troptometer dial to zero applied torque. 8. Apply torsional load using the hand crank taking readings of torque and twist simultaneously without stopping the machine, until indicated torque levels off to near constant value, then turn on motor continuing to take readings until fracture. 9. Find the angular rotation at every 300 pounds interval. All the way until the bar fractures. 10. After fracture, remove the steel specimen. ..................................................CONTINUED........................................