Mixed mode fatigue crack initiation and growth in a CT specimen repaired by stop hole technique

The present study aims to investigate the extent to which the fatigue behaviour of laser beam-welded AA6056-T6 butt joints with an already existing crack can be improved through the application of laser shock peening. Ultrasonic testing was utilized for in situ (nondestructive) measurement of fatigue crack growth during the fatigue test. This procedure allowed the preparation of welded specimens with surface fatigue cracks with a depth of approximately 1.2 mm. The precracked specimens showed a 20% reduction in the fatigue limit compared with specimens without cracks in the as-welded condition. Through the application of laser shock peening on the surfaces of the precracked specimens, it was possible to recover the fatigue life to the level of the specimens tested in the as-welded condition. The results of this study show that laser shock peening is a very promising technique to recover the fatigue life of welded joints with surface cracks, which can be detected by nondestructive testing. K E Y W O R D Saluminium alloys, fatigue crack, laser beam welding, laser shock peening, residual stress, ultrasonic crack tip diffraction

Section: Introductionmentioning

confidence: 99%

On the application of laser shock peening for retardation of surface fatigue cracks in laser beam‐welded AA6056

Kashaev

Ushmaev

Ventzke

et al. 2020

“…For instance, the U‐ and blunt V‐notches are utilized in the access panels and the O‐shaped notches in the riveted joints in aero‐structures. It should be noted that, although notches are useful in engineering components and structures, they are prone to the initiation of crack(s) due to the existence of significant stress concentration at their neighbourhood …”

Section: Introductionmentioning

confidence: 99%

“…It should be noted that, although notches are useful in engineering components and structures, they are prone to the initiation of crack(s) due to the existence of significant stress concentration at their neighbourhood. [1][2][3][4] Basically, the safety of notched components depends on 2 major factors, namely, the notch geometry and the material from the components are made. It is clear that higher level of the stress concentration in notched components may lead to more reduction of the structural safety.…”

Section: Introductionmentioning

confidence: 99%

On combination of the equivalent material concept and J‐integral criterion for ductile failure prediction of U‐notches subjected to tension

Majidi

Golmakani

Torabi

2018

The aim of the present research is to check the capability of the equivalent material concept (EMC) combined with the J‐integral failure criterion, called EMC‐J criterion, in predicting the load‐carrying capacity (LCC) of U‐notched ductile aluminium plates subjected to tension by considering the 2 moderate and large‐scale yielding regimes. For this purpose, first, a set of experimental results on LCC of 2 groups of thin U‐notched rectangular plates made of Al 7075‐T6 and Al 6061‐T6 are gathered from the recent literature. Then, because the Al 7075‐T6 and Al 6061‐T6 plates have ductile behaviour, EMC is employed to avoid performing elastic‐plastic failure analysis for LCC predictions. Up to now, different failure models in the context of the linear‐elastic notch fracture mechanics have been successfully utilized in combination with EMC for ductile failure prediction of notched members. However, this is the first time in this research that J‐integral, as a well‐known brittle failure criterion, is linked to EMC for predicting LCC of the U‐notched rectangular aluminium plates. Finally, it is shown that EMC‐J criterion can predict well the experimental results of tensile LCC.

“…[1][2][3][4] To accomplish this goal, it is vitally required to predict the crack initiation with high accuracy by utilizing proper fracture criteria. However, despite their useful applications, it is very likely that crack initiates from the notch because of the stress concentration located at the notch area.…”

Section: Introductionmentioning

confidence: 99%

Application of EMC‐J criterion to fracture prediction of U‐notched polymeric specimens with nonlinear behaviour

Majidi

Razavi

Torabi

2018

Self Cite

The main purpose of the present research paper is to investigate applicability of a new energy‐based failure prediction model, called EMC‐J criterion, to predict the critical loads of U‐notched polymeric samples having a ductile behaviour and loaded under symmetric 3‐point bending. The evaluated polymeric single edge notch bending samples containing U‐notches failed by considerable plastic deformations around the notch border, making it inappropriate to directly use classic linear elastic‐based formulations. Due to the elastic‐plastic behaviour of the tested polymeric material, EMC‐J criterion is applied to avoid using complex and extremely time‐consuming nonlinear analysis for failure load predictions. Finally, it is shown that EMC‐J criterion can provide a good consistency between the experimental and theoretical results with an average discrepancy of about 10%.