Page 1 • The various engineering and true stress-strain properties obtainable from a tension test are summarized by the categorized listing of Table 1.1. • Note that the engineering fracture strain e f and the % elongation are only different ways of stating the same quantity. Also, the %RA and e f can be calculated from each other. • Note that the strength coefficient H determines the magnitude of the true stress in the large strain region of the stress-strain curve, and so it is included as a measure of strength. • The strain hardening exponent n is a measure of the rate of strain hardening. Page 2 • The various engineering and true stress-strain properties obtainable from a tension test are summarized by the categorized listing of Table 1.1. • Note that the engineering fracture strain e f and the % elongation are only different ways of stating the same quantity. Also, the %RA and e f can be calculated from each other. • Note that the strength coefficient H determines the magnitude of the true stress in the large strain region of the stress-strain curve, and so it is included as a measure of strength. • The strain hardening exponent n is a measure of the rate of strain hardening. Table 1.1 Materials Properties Obtainable from Tension Tests Category Engineering Property True Stress-Strain Property Elastic Constants Elastic modulus, E Poisson's ratio, ? Strength Proportional limit, s p Yield strength, s y Ultimate tensile strength, s µ Engineering fracture strength, s ƒ True fracture strength, s f Strength coefficient, H or K Ductility Percent elongation, 100 ? ƒ Reduction in area, %RA True fracture strain, ?? ƒ Energy Capacity Resilience, ?u r Tensile toughness, u t True toughness, ?u ƒ Strain hardening Strain hardening Ratio, s µ / s ? Strain hardening exponent, ?n Page 3 • The various engineering and true stress-strain properties obtainable from a tension test are summarized by the categorized listing of Table 1.1. • Note that the engineering fracture strain e f and the % elongation are only different ways of stating the same quantity. Also, the %RA and e f can be calculated from each other. • Note that the strength coefficient H determines the magnitude of the true stress in the large strain region of the stress-strain curve, and so it is included as a measure of strength. • The strain hardening exponent n is a measure of the rate of strain hardening. Table 1.1 Materials Properties Obtainable from Tension Tests Category Engineering Property True Stress-Strain Property Elastic Constants Elastic modulus, E Poisson's ratio, ? Strength Proportional limit, s p Yield strength, s y Ultimate tensile strength, s µ Engineering fracture strength, s ƒ True fracture strength, s f Strength coefficient, H or K Ductility Percent elongation, 100 ? ƒ Reduction in area, %RA True fracture strain, ?? ƒ Energy Capacity Resilience, ?u r Tensile toughness, u t True toughness, ?u ƒ Strain hardening Strain hardening Ratio, s µ / s ? Strain hardening exponent, ?n Modulus of Elasticity •The slope of the initial portion of the stress-strain curve is the modulus of elasticity, or Young’s Modulus. The modulus of elasticity is a measure of the stiffness of the material. It is an important design value. •The modulus of elasticity is determined by the building forces between atoms. It is only slightly affected by alloying. Page 4 • The various engineering and true stress-strain properties obtainable from a tension test are summarized by the categorized listing of Table 1.1. • Note that the engineering fracture strain e f and the % elongation are only different ways of stating the same quantity. Also, the %RA and e f can be calculated from each other. • Note that the strength coefficient H determines the magnitude of the true stress in the large strain region of the stress-strain curve, and so it is included as a measure of strength. • The strain hardening exponent n is a measure of the rate of strain hardening. Table 1.1 Materials Properties Obtainable from Tension Tests Category Engineering Property True Stress-Strain Property Elastic Constants Elastic modulus, E Poisson's ratio, ? Strength Proportional limit, s p Yield strength, s y Ultimate tensile strength, s µ Engineering fracture strength, s ƒ True fracture strength, s f Strength coefficient, H or K Ductility Percent elongation, 100 ? ƒ Reduction in area, %RA True fracture strain, ?? ƒ Energy Capacity Resilience, ?u r Tensile toughness, u t True toughness, ?u ƒ Strain hardening Strain hardening Ratio, s µ / s ? Strain hardening exponent, ?n Modulus of Elasticity •The slope of the initial portion of the stress-strain curve is the modulus of elasticity, or Young’s Modulus. The modulus of elasticity is a measure of the stiffness of the material. It is an important design value. •The modulus of elasticity is determined by the building forces between atoms. It is only slightly affected by alloying. Measures of Yielding • Yielding defines the point at which plastic deformation begins. This point may be difficult to determine in some materials, which have gradual transition from elastic to plastic behavior. Therefore, various criteria (depends on the sensitivity of the strain measurements) are used to define yielding. 1. Proportional Limit - This is the highest stress at which stress is directly proportional to strain. 2. Elastic Limit - This is the greatest stress the material can withstand without any measurable permanent strain remaining on the complete release of the load. 3. Yield Strength - This is the stress required to produce a small (0.2% strain) specified amount of plastic deformation. Page 5 • The various engineering and true stress-strain properties obtainable from a tension test are summarized by the categorized listing of Table 1.1. • Note that the engineering fracture strain e f and the % elongation are only different ways of stating the same quantity. Also, the %RA and e f can be calculated from each other. • Note that the strength coefficient H determines the magnitude of the true stress in the large strain region of the stress-strain curve, and so it is included as a measure of strength. • The strain hardening exponent n is a measure of the rate of strain hardening. Table 1.1 Materials Properties Obtainable from Tension Tests Category Engineering Property True Stress-Strain Property Elastic Constants Elastic modulus, E Poisson's ratio, ? Strength Proportional limit, s p Yield strength, s y Ultimate tensile strength, s µ Engineering fracture strength, s ƒ True fracture strength, s f Strength coefficient, H or K Ductility Percent elongation, 100 ? ƒ Reduction in area, %RA True fracture strain, ?? ƒ Energy Capacity Resilience, ?u r Tensile toughness, u t True toughness, ?u ƒ Strain hardening Strain hardening Ratio, s µ / s ? Strain hardening exponent, ?n Modulus of Elasticity •The slope of the initial portion of the stress-strain curve is the modulus of elasticity, or Young’s Modulus. The modulus of elasticity is a measure of the stiffness of the material. It is an important design value. •The modulus of elasticity is determined by the building forces between atoms. It is only slightly affected by alloying. Measures of Yielding • Yielding defines the point at which plastic deformation begins. This point may be difficult to determine in some materials, which have gradual transition from elastic to plastic behavior. Therefore, various criteria (depends on the sensitivity of the strain measurements) are used to define yielding. 1. Proportional Limit - This is the highest stress at which stress is directly proportional to strain. 2. Elastic Limit - This is the greatest stress the material can withstand without any measurable permanent strain remaining on the complete release of the load. 3. Yield Strength - This is the stress required to produce a small (0.2% strain) specified amount of plastic deformation. (a) Figure 1-13. (a) Typical stress-strain (type II) behavior for a metal showing elastic and plastic deformations, the proportional limit P, and the yield strength s y , as determined using the 0.002 strain offset method. (b) Representative stress-strain (type IV) behavior found for some steels demonstrating the yield drop (point) phenomenon. (a) (b)Read More

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