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Year |
2001 |
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Question Number |
174. |
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Category |
Select |
Question
The linear relationship between an applied stress and the resultant deformation defines a material’s:
1- modulus of elasticity
2- brittleness
3- yield strength
4- ultimate strength
5- toughness
Figures
Answer (click for answer)
Preferred response: 1
Young’s modulus (of elasticity, E) is the measure of the stiffness of a material or its ability to resist deformation: E = stress/strain (in the elastic range of the stress-strain curve it is the slope. Modulus of elasticity is the critical factor in load-sharing capacity. A linearly perfect elastic material has a straight stress-strain curve to the point of failure (the modulus is calculated be dividing the stress at failure (the ultimate stress) by the strain at failure (the ultimate strain).
Brittleness refers to materials that undergo only fully recoverable (elastic) deformation prior to failure and have little or no capacity to undergo permanent (plastic) deformation prior to failure. Yield strength or point is the transition point from the elastic to the plastic range, usually 0.2% strain in most metals. Ultimate strength is the maximum strength obtained by the material. Toughness is measured by the strain energy and is the capacity of a material to absorb energy. On a stress-strain curve it is illustrated as the area under the curve.
Reference: Miller, MD (ed.): Review of Orthopedics, ed 3. Philadelphia, PA, WB Saunders, 2000, pp 119-135.