Numerical-experimental Method for the Analysis of Residual Stresses in Cold-expanded Holes

Abstract

Hole cold expansion is a technique widely used to improve the fatigue life of components with holes, e.g. bolted or riveted joints. As it has been demonstrated in literature by analytical, numerical and experimental analyses carried out by several authors, the compressive residual stresses introduced by the hole cold expansion have a beneficial influence on both the static and the fatigue strength of the treated component, because they reduce significantly the typical stress peaks around the hole due to stress concentration. In the literature, various analyses of the residual stresses introduced by the hole cold expansion have been performed by using several methods such as X-ray diffraction, neutron diffraction and the modified Sachs method. Unfortunately, all these method are affected by some limitations: low measurement depth (X-ray method), complex measurement procedure (neutron diffraction method) and approximate formulation (Sachs method). In order to overcome such drawbacks, in this study a new mechanical method, based on an innovative extension of the "rectilinear groove method" associated with the classical "integral method" calculation procedure, is proposed. Experimental assessment of the proposed method has been performed by using aluminum 5083 H321 specimens with holes subjected to various levels of cold expansion.

Residual stress/strain evolution due to low‐cycle fatigue by removing local material volume and optical interferometric data

“…It was shown in many works that maximum compressive residual stress is located at the distance equals to 0.5 mm from the edge of the cold-expanded hole. [22][23][24][25][26][27][28] This fact is valid for a wide range of hole diameter values and interference levels. That is why the secondary hole diameter 2R 0 = 4.9 mm was chosen.…”

“…In order to overcome these drawbacks, a new hybrid numerical-experimental mechanical method was developed and implemented. 28 This technique is based both on the machining of a through-thickness rectilinear groove obtained by successive cuts and feeds and on the simple use of strain gauges array. The proposed method is capable of the accurate analysis of the variation of residual stresses along the Quantifying the evolution of residual stress due to cyclic loading contributes to more accurate prediction of the lifetime of cold-expanded holes.…”

The effect of low-cycle fatigue on evolution of fracture mechanics parameters in residual stress field caused by cold hole expansion

“…Non-destructive experimental techniques are mainly related to X-ray diffraction [2]. Destructive (mechanical) methods of residual stress determination are based on local material removing [13][14][15][16]. Several experimental studies have considered the improvement in fatigue performance due to the presence of compressive residual stresses [17][18][19].…”

First-order correction to counter the effect of eccentricity on the hole-drilling integral method with strain-gage rosettes

“…1 There are several experimental techniques for measuring residual stresses. 2 These include mechanical methods (destructive or semi-destructive) based on cuttings or local material removals to relieve the embedded residual stresses, such as the contour method, 3 the ring core method [4][5][6] and other specific approaches adapted to the geometry of the components investigated, [7][8][9][10][11] or also combining the hole-drilling method with the indentation. 12 After the material has been removed, a back calculation is required to obtain the residual stress distribution that has been relaxed.…”