A numerical method for reference stress in the evaluation of structure integrity

Chen, Haofeng and Cen, Z.Z. and Xu, B.Y. and Zhan, S.G. (1997) A numerical method for reference stress in the evaluation of structure integrity. International Journal of Pressure Vessels and Piping, 71 (1). pp. 47-53. ISSN 0308-0161 (https://doi.org/10.1016/S0308-0161(96)00040-3)

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The important concepts of reference stress has been widely used in structural component integrity assessments, both below and within the creep range of temperatures, mainly in Nuclear Electric's (fomerly CEGB) R5 an R6 procedures. The reference-stress method (RSM) has been proven to be successful in problems pertaining to creep growth, rupture damage, creep buckling, and, more recently, elastic-plastic fracture toughness. However, determination of the reference stress is not always a simple task. In the present paper, some existing methods for reference stress in evaluation of structure integrity are investigated in detail. In accordance with the relationship between the reference stress and limit load under certain applied loads or moments, a direct iterative algorithm used to determine the reference stress is proposed which depends on the solution of limit load. The penalty-function method is used to deal with the plastic-incompressibility condition. The numerical difficulties caused by the nonlinearity and nonsmoothness of the goal function are overcome. Numerical examples are given to demonstrate the applicability of the procedure.