Chapter 3

2. Chapter 3 Mechanical Testing Mechanical Testing • Dynamic Mechanical Tests • Static Mechanical Tests • Hardness Testing

3. A mechanical force or load may be applied using five different methods.

4. Longitudinal and transverse test specimens taken from cold-rolled plate material exhibit different mechanical properties.

5. There are four classifications of cyclic stresses in fatigue. A cycle is each complete application of the stress.

6. The magnitude of the fatigue limit depends on the stress repetition pattern, which is plotted on an S-N curve.

7. Metal tested at a low strain rate is ductile compared with the same metal tested at a high strain rate.

8. A universal pendulum impact tester can perform both the Charpy and Izod impact tests.

9. The V-notch is the most common Charpy and Izod impact test specimen.

10. The swing of the pendulum after it strikes the test specimen indicates the energy absorbed on impact.

11. The main differences between the Charpy and Izod impact tests are the position of the notch and the method of support of the test specimen.

12. The sharper the inflection of the curve, the easier the estimation of the NDT temperature.

13. The drop weight test is more reliable than the Charpy when determining ductility.

14. A universal testing machine can be mechanical or hydraulic.

15. A fillet is used on the tensile test specimen to minimize stress concentrations, and the gauge marks are always an equal distance from the center of the length of the reduced section.

16. A variety of tensile test specimen ends are used to ensure secure and uniform gripping by the test machine.

17. An extensometer measures the extension of elongation of the tensile test specimen.

18. The load-extension curve shows load and extension limits for metals.

19. Increased gauge length and reduced diameter at the narrowest point are measured and used to calculate the percent elongation and percent reduction in area.

20. The yield strength, or 0.2% offset, is calculated by measuring the stress that causes a specific permanent strain (usually 0.2%).

21. Percent elongation is calculated from the gauge length.

22. The guided bend test is an inexpensive and rapid method to check the quality of a weld.

23. Cupping tests provide an indication of the formability of sheet metal.

24. A torsion testing machine is used for determining a metal’s resistance to shear.

25. A tropometer is used to measure the degree of twist during a torsion test.

26. The scleroscope hardness tester uses the height of rebound of a diamond-tipped hammer from the test specimen surface to determine hardness.

27. The Equotip metal hardness tester can be used in five positions.

28. The Brinell hardness tester applies a load for a specific period of time and causes an indentation that is used to calculate hardness.

29. Soft or hard metals require careful measurement of their indentations in the Brinell test.

30. The Rockwell test uses two loads, a minor and a major, that are applied sequentially to determine hardness.

31. The Rockwell designation system consists of the hardness number followed by HR, which is followed by the letter indicating the specific Rockwell scale.

32. The microhardness measured by a microhardness tester is always higher than the bulk surface hardness.