Effect of local wall thinning on shakedown regimes of pressurized elbows subjected to cyclic in-plane and out-of-plane bending

• A direct non-cyclic technique generated shakedown boundaries of thinned elbows.
• Thinning reduces shakedown domains as compared to sound elbows.
• Out-of-plane bending exhibit quite larger shakedown domains than in-plane bending.
• Intrados/crown thinning is more damaging than extrados thinning.
• Proximity of critical points to thinning location affects shakedown load capacity.

The current research utilizes a direct non-cyclic technique to generate elastic shakedown domains for thinned-wall 90° elbows. The elbows are subjected to simultaneous steady internal pressures and cyclic in-plane and out-of-plane bending moments. Wall thinning is located at the intrados, extrados, and crown once at a time. Effects of thinning depth and thinning location under both cyclic in-plane and out-of-plane bending modes are investigated. Generated shakedown boundaries are compared to those corresponding to sound elbows. Elbows subjected to out-of-plane bending moments revealed relatively higher shakedown domains compared to corresponding elbows subjected to in-plane bending. It is generally noticed that thinning at the intrados or crown has more severe effect on reducing elbows shakedown domains as compared to thinning at the extrados for both in-plane and out-of-plane bending modes.