Method of damage mechanics to determine the p-S-N curve of material

High reliability is required in the structures of aero planes, it is necessary to determine the probability fatigue curves of materials. It is well known that it is very expensive and takes numerous time to obtain probability fatigue curves by fatigue tests. Due to this situation, by means of the method of damage mechanics, for the first time a p-S-N curve can be determined according to its median S-N curve and the corresponding fatigue data. The result shows that the fatigue strength and the fatigue life decrease greatly with the increase of the survival probability. This conclusion was obtained from the fatigue tests of metals, so this method can be used under this condition. However, it can be also extended to some new kinds of composite materials. In addition, it should be indicated that the confidence will be higher with a larger sample. The significance of this method is that median fatigue tests can be used to replace probabilistic fatigue tests in order to draw p-S-N curves. Thus the time and the cost of fatigue tests will be reduced greatly.