Evaluation of collapse moment of pressurized 30°–180° bend pipes subjected to out-of-plane bending moment

Abstract

The present paper determines collapse moments of pressurized 30°–180° pipe bends incorporated with initial geometric imperfection under out-of-plane bending moment. Extensive finite element analyses are carried out considering material as well as geometric nonlinearity. The twice-elastic-slope method is used to determine collapse moment. The results show that initial imperfection produces significant change in collapse moment for unpressurized pipe bends and pipe bends applied to higher internal pressure. The application of internal pressure produces stiffening effect to pipe bends which increases collapse moment up to a certain limit and with further increase in pressure, collapse moment decreases. The bend angle effect on collapse moment reduces with the increase in internal pressure and bend radius. Based on finite element results, collapse moment equations are formed as a function of the pipe bend geometry parameters, initial geometric imperfection, bend angle, and internal pressure for elastic-perfectly plastic material models.

Development of an improved structural integrity assessment correlation for circumferential through-wall cracked 90° shape-distorted pipe bends subjected to in-plane opening bending moment

“…The straight pipes nullify the end effects produced by the boundary constraints and permit propagation of the effects of shape imperfections. [22][23][24][25][26] For a detailed analysis, a range of pipe bends was selected to include short to long-bend radii and thin walls to thick walls considering various combinations of the TWCC angle and shape distortions. Table 1 presents the dimensions chosen for the pipe bend 27 per the mandates of the ASME B&PV code, section II.…”

“…28,29 The material considered was Type 304 SS, generally used in the piping system, with a 0.26 Poisson's ratio 0.25em false( γ false), yield stress ( σ o false) of 271.93 MPa, and Young's modulus ( E ) of 193 GPa. 17,18,26,28 For the present analysis, the elastic-perfectly plastic (EPP) material model was used, which offers a conservative estimation of the FE results and thus is useful from the standpoint of the pipe bend's design. 28…”