Tensile Strength
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Define the following terms and state them in a generic stress-strain curve given below in Fig.1.1: tensile strength, yield strength, proportional limit, elastic limit, modulus of elasticity in tension, ductility and percent elongation, shear strength, Poissons ratio, and modulus of elasticity in shear, etc.Tensile strengthTensile strength is known as the peak of the stress strain curve. After the peak of the curve, has been reached there is a rapid decrease in stress as the metal deforms and necks down. Formula for tensile strength:[pic 1]Yield strengthYield strength is determined by the offset method, in which a line is drawn parallel to the straight-line portion of the curve and is offset to the right by usually 0.2% strain. The yield is where the straight line intersects the stress strain curve. Once, the yield point has been reached, the elasticity of the material will exceeded and thus leading toward the beginning of plastic deformation.Proportional limitThe proportional limit is the point on the stress-strain curve where it deviates from the straight line. It usually lies close to the yield strength of the material. Below the proportional limit Hooke’s Law is applicable.Elastic limitElastic limit is a point at which a material experiences some plastic strain and will not return to its original shape beyond this point, the material experiences plastic deformation. However, below the elastic limit point, the material behaves elastically and can be returned to its original shape. This point also lies close to yield strength.Modulus of elasticity in tensionThe gradient of the straight line portion of the diagram.[pic 2]DuctilityDuctility is how much a material will deform before if ultimately fractures or fails.
Percent elongationPercentage elongation is used to measure ductility of material after fracture.[pic 3]Shear strengthKnown as yield strength and ultimate strength in shear.[pic 4][pic 5]Poisson’s ratioPoisson’s ratio is known as ratio of shortening (lateral) strain to tensile strain.[pic 6][pic 7][pic 8]Modulus of elasticity in shearThe modulus of elasticity in shear (G) is the ratio of shearing stress to shearing strain. In the elastic region, the relationship is defined as:[pic 9]G = shear modulus, or shear modulus of elasticityFor most materials,, where E = elastic Modulus, [pic 10][pic 11]Figure 1.1[pic 12]