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

Abstract

Three experimental methods, based on optical interferometric measurements of deformation response to local material removing, have been implemented for residual stresses determination. Two first techniques are employed to characterize initial residual stress values and their evolution near welded joints of aluminium plates under low‐cycle fatigue. The hole‐drilling method gives high‐accurate dependencies between residual stress components and number of cycles. The second approach comprises cracks modelling by narrow notches to describe residual stress distributions in more wide spatial range near the weld. The results demonstrate residual stress evolution is of complex character and cannot be uniquely qualified as a gradual relaxation. Besides, the secondary hole drilling method is developed and used as a fast and reliable tool to quantify the redistribution of residual strains near cold‐expanded holes due to low‐cycle fatigue. Dependencies of circumferential residual strains along the secondary hole edge versus number of cycles are constructed.

Influence of stress ratio on residual stress evolution near cold-expanded hole due to low-cycle fatigue by crack compliance data

“…The essence of the methodology involved resides in comparison of real interference fringe patterns and analogous artificial images. This approach is a powerful instrument for fine verification of measurement results when initial experimental information is presented in the form of interference fringe patterns [20,21,23,24]. Interference fringe pattern obtained for specimen T5_08 with symmetrical crack for tensile load value P = 7.96 kN are shown in Fig.…”

“…A set of both numerical and experimental methods has been developed and realized to consider the first from above problems [8][9][10][11][12][13][14][15][16][17]. But only few experimental works concern an evolution of deformation parameters and residual stresses [18][19][20]. One of them employs non-contact full-field strain measurements using both digital image correlation (DIC) and thermoelastic stress analysis (TSA) [18].…”

“…The main drawback resides in the fact that that the initial point of a cut sequence, which is used for residual stress evaluation, is located at the external edge of the specimen, but not at the hole edge. The technique, which employs the secondary hole drilling and further measurements of hole diameter increments in principal stress directions by electronic speckle-pattern interferometry (ESPI), has been implemented to quantify residual strain evolution caused by low-cycle fatigue [20]. The cycles parameters are: R= -0.4;   = 350 MPa.…”

“…Present paper has common features with all three above-mentioned works. The first of them resides in implementing fullfield measurement techniques as in works [18,20]. The crack compliance method is the base of this paper and work [19].…”

Residual stresses near cold-expanded hole at different stages of high-cycle fatigue by crack compliance data

“…Numerous numerical and experimental methods have been developed and implemented to solve the first from above problems [3][4][5][6][7][8][9][10]. A set of both experimental and numerical works concerns residual stress evolution [11][12][13][14][15][16][17][18]. Required data are available for restricted spectrum of loading cycle parameters.…”