Deformation behavior of clad pipe under uniform internal pressure has been analyzed with emphasis on the influence of clad metal on the burst strength of the clad pipe. The maximum pressure pmax and the critical circumferential strain(εθ)max at pmax can be estimated well by a model based on the rule of mixture. Clad metal contributes to the maximum pressure pmax of the clad pipe as an equivalent base metal of thickness bi⋅(δTC/δTB), where bi is the thickness of the clad metal, and δTB and δTc are the base metal strength and the clad metal strength, respectively. Design concept of the clad pipe has been discussed in the light of this finding. The most popular concept conventionally applied, in which the existence of the clad metal is not taken into account at all, gives too much conservative evaluation of the maximum pressure pmax in the case that the clad metal has apparently higher strength than the base metal. Alternative concept that all clad components are assumed to be constructed of homogeneous base metal results in unsafe estimation of pmax when the strength of the clad metal is lower compared to the base metal strength. ASME method seems to be a combination of the former concept and the following new concept proposed in this paper. The new design concept is a simple one which treats the clad metal as the equivalent base metal of thickness bi⋅(δTC/δTB) and gives more reasonable estimation of the burst strength of the clad pipe.
