Effect of bend angle on plastic loads of pipe bends under internal pressure and in-plane bending

This paper quantifies the effect of a bend angle of a pipe bend on plastic loads, via small strain and large strain FE limit analyses using elastic-perfectly plastic materials. To consider the effect of the attached straight pipe, two limiting cases are considered. One case corresponds to the pipe bend without the attached straight pipe, and the other to that with a sufficiently long attached straight pipe. For the former case, the FE results suggest that the limit load is not affected by the bend angle for both in-plane bending and internal pressure. For the latter case, however, the bend angle affects plastic loads. An interesting finding is that the plastic load smoothly changes from the limit load of the straight pipe when the bend angle approaches zero to the plastic load of the 90° pipe bend when the bend angle approaches 90 degree. Based on such observations, closed-form plastic load solutions are proposed for the pipe bend with an arbitrary bend angle under in-plane bending and internal pressure.