1. Chapter 2
Properties of Metals

2. Stress-Strain Curve
Figure 2.2 A typical stress- strain curve obtained from a tension test, showing various features.

3. Strain-
The unit deformation of a material when stress is applied.

4. Stress-
The load per unit of area on a stress-strain diagram.

5. Tensile-Test Specimen and Machine
(b)
Figure 2.1 (a) A standard tensile-test specimen before and after pulling, showing original and final gage lengths. (b) A typical tensile-testing machine.

6. Tensile stress-
Refers to an object loaded in tension, denoting the longitudinal force that causes the fibers of a material to elongate.

7. Temperature Effects on Stress-Strain Curves
Figure 2.7 Typical effects of temperature on stress-strain curves. Note that temperature affects the modulus of elasticity, the yield stress, the ultimate tensile strength, and the toughness (area under the curve) of materials.

8. Proportional limit-
On the stress-strain diagram, the point where the ratio of stress to strain (i.e., the modulus of elasticity) is no longer a constant, or where that line is no longer straight.

9. Stress-Strain Curve
Figure 2.2 A typical stress- strain curve obtained from a tension test, showing various features.

10. Yield strength-
The stress at which a material deviates by a specified amount of strain from the region where stress and strain are proportional.

11. Ultimate tensile strength or UTS-
The stress equal to the maximum load achieved in a tensile test divided by the original area of the specimen.

12. Modulus of elasticity-
The ratio of the unit stress to the unit deformation (strain) of a structural material; a constant as long as the unit stress is below the elastic limit.
Also known as Young’s Modulus
Shearing modulus of elasticity is often called the modulus of rigidity.

13. Creep-
Slow plastic deformation in steel and most structural metals caused by prolonged stress under the yield point at elevated temperatures.

14. Compressive stress-
Refers to a member loaded in compression, which gives rise to either a given reduction in volume

15. Shear load-
A load that tends to force materials apart by application of side-slip action.

16. Tensile load-
A load applied to a part or parts that attempts to pull apart by a stretching action.

17. Ductility-
The property of a material that allows it to fail permanently, or to exhibit plasticity without rupture while under tension.

18. Impact test-
A test that applies an impact load (by a swinging hammer) to a small notched specimen.
The data from the test are in energy units, joules or inch- pounds.
The test is performed with the specimens at different temperatures; the results determine the notch toughness of the metals at the temperature tested.
There are two types of specimens-
Izod
Charpy, with Charpy the one primarily used in the United States.

19. Impact Test Specimens
Figure Impact test specimens: (a) Charpy; (b) Izod.

20. Malleability-
The ability of a metal to deform permanently without rupture when loaded in compression.

21. Fatigue in metals-
The tendency of a metal to fail by breaking or cracking under conditions of repeated cyclical stressing that takes place well below the ultimate tensile strength.

22. Hardening-
The process of increasing the hardness of a ferrous alloy by austenitizing and quenching; also, the process of increasing the hardness of some stainless steels and nonferrous alloys by solution heat treatment and precipitation.

23. Hardness-
The property of a metal that allows it to resist being permanently deformed.
This property is divided into three categories:
the resistance to penetration
the resistance to abrasion
elastic hardness.

24. Hardness Tests
Figure General characteristics of hardness-testing methods and formulas for calculating hardness. The quantity P is the load applied. Source: H. W. Hayden, et al., The Structure and Properties of Materials, Vol. III (John Wiley & Sons, 1965).

25. Plasticity-
The quality of material such that it can be deformed without breaking.
Clay is a completely plastic material.
Metals exhibit plasticity in varying amounts.