Creep Strength and Rupture Strength

There is no limiting stress at which creep does not take place and for this reason it is not possible to define anything like creep limit. However, for practical purpose creep strength is defined as a stress at a given temperature which produces a minimum creep rate of a certain amount, usually 0.0001 percent/hour or 0.001 percent/hour. Yet another property of material is defined as rupture strength. Rupture strength refers to the stress at a given temperature to cause rupture after certain specified period, usually 100, 1000 or 10,000 hours. The creep strength and rupture strength plotted against temperature are greatly useful to designers in making selection of material.