Effect of Internal Pressure on Elastic-Plastic Behavior of Pipe Elbows Under In-Plane Bending Moments

Abstract

The purpose of this study is to investigate the effect of pressure on the strain and stress analysis of pipe elbows subjected to in-plane bending moments. A finite element model for the bend was constructed and loaded with a pressure of 1200 psi and end moments taking geometric and material nonlinearities into account using (ABAQUS) nonlinear finite element code. The pressure changes the effective stress distribution and location of the initial yielding from the inside surface of the elbow crown to the outside surface for the closing moment case and increases the moment of yielding. For the opening moment case, yielding starts at the inside surface of the elbow crown with and without pressure. The pressure changes the location of the maximum axial strain at instability for the closing and opening cases, and it also changes the ovality of the cross section in both cases.

Determination of ovality and wall thinning effects on B2 stress indices for pipe bends under in-plane closing bending moment

“…Type 304 stainless steel was the material considered for the analysis with yield stress (σ y ) 271.93 MPa, Poisson’s ratio (ν) 0.2642, and Young’s modulus ( E ) 193 GPa. 9–17 The reference model is chosen to be bends having circular cross section and uniform wall thickness and the corresponding stress index is B 2 Ref while irregular models corresponds to the bends having shape irregularities and the corresponding stress indices are referred as B 2 Igr .…”

“…Type 304 stainless steel was the material considered for the analysis with yield stress (s y ) 271.93 MPa, Poisson's ratio (n) 0.2642, and Young's modulus (E) 193 GPa. [9][10][11][12][13][14][15][16][17] The reference model is chosen to be bends having circular cross section and uniform wall thickness and the corresponding stress index is B Ref…”

“…Twice-elastic-slope (TES) methodology was used to calculate the B 2 stress index from the critical collapse load. [7][8][9][10][11][12][13][14][15][16][17] The TES defines the plastic collapse moment from moment rotation curve. It plots a line twice the slope of the elastic part of the curve from the origin.…”

“…7,8 Shalaby and Younan performed a detailed study on elastic-perfectly plastic behavior of elbows under inplane opening and closing bending. [9][10][11] Veerappan et al investigated the acceptance of pipe bends having thinning and ovality by using FE method. 12 Christo et al analyzed the combined influence of ovality and thinning on plastic collapsing loads under a combination of internal pressure and in-plane closing moment and derived closed-form solutions to determine the critical collapsing load.…”

Using XFEM to Predict the Damage with Temperature of the Steel Pipe Elbows under Bending and Pressure loading

“…Others like Tan et al [15] recently studied the bending and opening flexion of an elbow and compared it with finite element analysis results. Shalaby and Younan [16] analyzed 90 degrees steel elbows for a wide range of diameter / thickness ratios under in-plane bending moment in opening and closing with internal pressure. Karamanos et al [17] studied the damage of non-pressurized buckling elbows numerically, a good comparison was found between the numerical results and the experimental tests.…”