Finite Element Analysis of Effects of Strain Hardening Rate on Cold Expansion of Fastener Holes

Residual stress is having a significant effect on fatigue lives of the structural engineering components, particularly in aerospace industry. Mandrelizing expands the hole diameter by means of a radial interference pressure to allow radial plastic flow of material and some elastic recovery after the removal of the mandrel. Thus, it produces a large residual compressive zone around the hole. This zone acts as a barrier to crack growth thereby enhancing the service life of the structural components. In this work, an attempt has been made to simulate a newly proposed CsSmPCx process by using ANSYS FEM code. The critical effects of material properties variation on the residual stress field are analyzed. The drawbacks of the presently used hole cold expansion mandrelizing methods are removed thereby giving nearly uniform residual stress distribution around the hole. This newly proposed method is more reliable and gives increased service life enhancement compared with the presently used mandrelizing methods, without any weight and risk penalty.

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