Statistical material selection uncertainty

In addition, the pipe lifetime in brittle fracture for various hoop stress can be predicted, when the maximum size of inelusion is controllable. A teehnique of the lifetime prediction for variable hoop stress with controllable inclusion size (in this ease, the size of inclusion is selected as 74.5 aw ) is illustrated in Figure 8. As reported by many authors, the failure time in brittle fracture exhibits a large scatter. It is mainly associated with the random size and location of the inelusions. This fact is also well known for other materials, such as high strength steel [10] and smface hardened steel [11]. For better prediction of the scatter of failure time, statistical approach is needed. Thus, the lower and upper bounds of failure time for plied hoop stress (see Figure 8) take into account the uncertainty of pipe hfetime. 

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