1. Chapter 4. Mechanical Testing: Tension Test and Other Basic Tests
4.1 introduction
◦ Geometry & loading situation
Fig4.1 geometry and loading situations commoly emplonly employed in mechan-ical testing of materials: (a) tension, (b) compression, (c) indentation hardness, (d) cantilever bending, (e) three-point bending, (f) four-point bending, and (g) torsion.
Figure: 04-01a-g
Fig4.2 three classes of test specimen: (a) smooth or unnotched, (b) notched, and (c) precracked.

2. 4.1.1 Test equipment -Universal testing machines Figure: 04-03
Fig4.3 schematics of two relatively simple testing machine designs, called universal testing machines. The mechanical system (above) drives two large screws to apply the load, and the hydraulic system (below) uses the pres-sure of oil in a piston.

3. Sensors for load & displacement
Fig4.4 modern closed-loop servohydraulic testing system. Three sensors are em-ployed: (a) load cell, (b) extensometer, and (c) LVDT.
Figure: 04-04
Sensors for load & displacement
-LVDT, strain gage-based load cell, extensometer

4. 4.1.2 Standard Test Methods
- ASTM standards

5. 4.2 Introduction to Tension Test 응력과 변형률
Fig 4.5 tensile specimens of metals (left to right): untested specimen with 9mm diameter test section, and broken specimens of gray cast iron, aluminum alloy 7075-T651, and hot-rolled AISI 1020 steel.

6. 4.3 Engineering stress-strain properties
fig4.6 tensile specimens of polymers (left to right): untested specimen with a 7.6mm diameter test section, a partially tested specimen of high-density polyethylene (HDPE), and broken specimens of nylon 101 and Teflon (PTFE).
Figure: 04-06

7. 4.3.1 Elastic constants Figure: 04-07
Fig4.7 typical grips for a tension test in a universal testing machine.

8. Figure: 04-08
Fig4.8 stress-strain curve for gray cast iron in tension showing brittle behavior.

9. Figure: 04-09
Fig4.9 schematic of the engineering stress-strain curve of a typical ductile metal that exhibits necking behavior.

10. Figure: 04-10
Fig4.10 engineering stress-strain curve and geometry of deformation typical of some polymers.

11. 4.3.2 Engineering measures of strength
Figure: 04-11a-c
Fig4.11 initial portions of stress-strain curves: (a) many metals and alloys, (b) material with yield drop, and (c) material with no linear region

12. 4.3.4 discussion of necking behavior and ductility
Figure: 04-12a-b
Fig4.12 deformation in a tension test of a ductile metal: (a) unstrained, (b) after uniform elongation, and (c) during necking.

13. Figure: 04-13
Fig4.13 fractures from tension test on 9mm diameter specimens of hot-rolled AISI 1020 steel (left) and gray cast iron (right).

14. Figure: E4.1a-b
Fig E4.1

15. 4.4 Trends in tensile behavior
4.4.1 Trends for different materials

17. 4.4 Trends in tensile behavior 4.4.1 Trends for different materials
Figure: 04-14
Fig4.14 engineering stress-strain curves from tension tests on three steels.

18. Figure: 04-15
Fig4.15 engineering stress-strain curves from tension tests on three aluminum alloys.

19. Figure: 04-16
Fig4.16 engineering stress-strain curves from tension tests on three polymers.

20. 4.4.2 Effects of temperature and strain rate
Figure: 04-17
Fig4.17 effect of strain rate on the ultimate tensile tensile strength of copper for tests at various temperatures.

21. 4.5 True stress-strain interpretation of tension test
4.5.1 Definitions of true stress and strain
Figure: 04-18
Fig4.18 engineering and true stress-strain curves from a tension test on hot- rolled AISI 1020 steel.

22. 4.5.3 Limitations on true stress-strain equations
Figure: 04-19
Fig use and limitations of various equations for stresses and strains from a tension test.

23. 4.5.4 Bridgman correction for hoop stress
Figure: 04-20
Fig4.20 curve giving correction factors on true stress for the effect of hoop stress due to necking in steels. The curve of [Bridgman 44] is shown along with the curve from Eq approximating it.

25. 4.5.6 True stress-strain properties

27. 4.5.5 True stress-strain curves
Figure: 04-21
Fig log-log plot of true stress versus true strain from the large strain portion of a tension test on AISI 1020 steel.

28. 4.6.1 Test methods for compression
4.6 COMPRESSION TEST
4.6.1 Test methods for compression
Figure: 04-22
Fig compression test in a universal testing machine using a spherical-seated bearing block.

29. 4.6.2 Materials properties in compression
Figure: 04-23
Fig compression specimens of metals (left to right): untested specimen, and tested specimens of gray cast iron, aluminum alloy 7075-T651, and hot-rolled AISI 1020 steel. Diameters before testing were approximately 25mm, and lengths were 76mm.

30. Figure: 04-24
Fig untested and tested 150mm diameter compression specimens of concrete with hokie limestone aggregate.

31. 4.6.3 Trends in compressive behavior
Figure: 04-25
Fig initial portions of stress-strain curves in tension and compression for 7075-T651 aluminum.

32. Figure: 04-26
Fig stress-strain curves for plexiglass (acrylic, PMMA) in both tension and compression.

33. Figure: 04-27
Fig systems for testing brittle materials such as concrete and stone in compression with lateral pressure.

34. Indentation .vs. Shore(or Scleroscope) or Mohs
4.7 HARDNESS TEST
Indentation .vs. Shore(or Scleroscope) or Mohs
Figure: 04-28
Fig plastic deformation under a brinell hardness indenter.

35. 4.7.1 Brinell hardness test
Figure: 04-29
Fig approximate relative hardness of various metals and ceramics.

36. Figure: 04-30
Fig brinell hardness tester, and indenter being applied to a sample.

37. Figure: 04-31
Fig Brinell and Rockwell hardness indentations. On the left, in hot-rolled AISI 1020 steel, the larger brinell indentation has a diameter of 5.4mm, giving HB = 121, and the smaller Rockwell B indentation gave HRB = 72. On the right, a higher strength steel has indentations corresponding to HB=241 and HRC=20.

38. 4.7.2 Vickers hardness test
Fig Vickers hardness indentation

39. Figure: 04-32

40. Figure: 04-33
Fig approximate relationship between ultimate tensile strength and Brinell and Vickers hardness of carbon and alloy steels.

41. 4.7.3 Rockwell hardness test

42. 4.7.3 Rockwell hardness test
Figure: 04-34a-b
Fig Rockwell hardness indentation made by application of (a) the minor load, and (b) the major load, on a diamond Brale indenter.

43. 4.7.4 Hardness correlations and conversions

44. 4.8 NOTCH-IMPACT TESTS 4.8.1 Types of test
Figure: 04-35a-b
Fig specimens and loading configurations for (a) Charpy V-notch and (b) Izod tests.

45. Figure: 04-36
Fig Charpy testing machine, shown with the pendulum in the raised position prior to its release to impact a specimen.

46. Figure: 04-37
Fig Broken Charpy specimens, left to right, of gray cast iron, AISI 4140 steel tempered to Mpa, and the Same steel at Mpa. The specimens are 10mm in both width and thickness.

47. 4.8.2 Trends in impact behavior and discussion
Figure: 04-38
Fig variation in charpy V-notch impact energy with temperature for normalized plain carbon steels of various carbon contents.

48. Figure: 04-39
Fig temperature dependence of Charpy V-notch impact resistance for different alloy steels of similar carbon content, all quenched and tempered to HRC 34.

49. 4.9 Bending and torsion tests 4.9.1 Bending (Flexure) tests
Figure: 04-40a-c
Fig loading configuration for (a) three-point bending and (b) four-point bending. The deflection of the centerline of either beam is similar to (c).

50. 4.9.3 Torsion test
Figure: 04-41
Fig A round bar in torsion and resulting state of stress. The equivalent normal stresses and strains for a 45o rotation of the coordinate axes are also shown.

51. Figure: 04-42
Fig typical torsion failures showing brittle behavior (above) in gray cast iron, and ductile behavior (below) in aluminum alloy 2024-T351/

52. Figure: 04-43
Fig Thin-walled tube in torsion (a). The approximately uniform shear stress on the cross section is shown in (b), and the geometry for an angle of twist in (c).