Piping elbows with cracks Part 1: a parametric study of the influence of crack size on limit loads due to pressure and opening bending

Finite element analyses of cracked short-radius piping elbows are reported. Both axial and circumferential cracks, centred about the bend crown or int rados respectively, are considered. The defects are internal, with depth-th ickness ratios a/t in the range 0.25 less than or equal to a/t less than or equal to 1.0. Since the aim is to assess limit loads, the analysis assumes elastic-perfectly plastic material behaviour with no geometric non-lineari ties. The loadings considered are (a) opening bending moment, (b) internal pressure and (c) combined loading of steady pressure, set at the design val ue of the pipe elbow, with a superimposed monotonically increasing opening bending moment. For each type of loading, the general component behaviour, by consideration of the global deformation with increasing load is reported. Limit load val ues for each case are presented and the relative reductions in load-carryin g capacity, compared with that predicted for a defect free elbow of the sam e material and dimensions, are given.