Evaluation of residual post-bending stresses in pipe fittings

Abstract

Formulas are presented for calculation of residual post-bending stresses that develop in pipe fittings. The formulas are derived as a result of solution of the elasto-plastic problem of the bending of a straight pipe.Residual stresses σ res (axial stresses) that develop in fittings after bending are defined as the sum of the stresses that are manifested in the fittings during bending σ bend and unloading σ unl (see Fig. 1):(1)The stresses that develop in a fitting during bending σ bend are determined from the following formulas: in the region of elastic deformations:(2) in the convex (tension) region when 0 ≤ y < y y ,in the concave (compression) region when -y y < y ≤ 0; and in the region of plastic deformations:in the convex (tension) region when y y ≤ y ≤ r out ,in the concave (compression) region when -r out ≤ y ≤ -y y , where y is the distance from the neutral axis to the layer under consideration in the cross section of the fitting, y y is the distance from the neutral axis to the region of plastic deformations in the cross section of the fitting (the coordinate of the boundary between elastic and plastic deformations)ξ y is the deformation for which the stresses are equal to the yield point at 20°(R e/20 ) (7) ξ y / = R E e 20 20 ; y y max out y r = ξ ξ ; bend / σ = −R e 20 bend / σ = R e 20 σ bend = − y R E 20 σ bend = y R E 20

Finite Element Stress Analysis of the Welded Incline-Bent Pipe

“…They analyzed the stress of the overall stress and the internal pressure bending moment respectively. In abroad countries, the study of welded incline-bent pipe is relatively small, but there are still a lot of literature for reference, and other scholars made A summary and experimental investigation on their stress analysis [9][10][11]. Based on the research results of various scholars at domestic and abroad, this paper applies the three-dimensional finite element analysis software ANSYS to analyze the stress analysis of the welded incline-bent pipe [12].…”