Comparison of plastic loads for elbows with experimental data

Finding plastic (limit) loads for elbows under various loading conditions such as in-plane bending and out-of-plane bending is not an easy task due to complexities involved in plastic analyses. Considering complexities involved in plastic limit analysis of elbow, deriving analytical solutions of plastic loads for elbows would be extremely difficult. So, recently the limit analysis using finite element program has been widely adopted. Based on extensive and systematic FE limit analyses using elastic-perfectly plastic materials, closed-form solutions of plastic loads for defect-free elbows under in-plane closing, in-plane opening and out-of-plane bending were presented. This paper summarizes the well-known criteria for finding plastic(limit) loads proposed by ASME BPVC Sec.III [1], Zahoor [4], Chattopadhyay et al. [17] and Kim et al. [19] The purpose of this paper is to integrate and improve the proposed solutions by Kim et al. Also, comparison results with published experimental data are presented. From these results, the pros and cons of each criterion for finding plastic(limit) loads for elbows are discussed.