Determination of the Crack Tip Position by Digital Image Correlation during Static and Cyclic Fracture Toughness Tests of Aluminum Alloys

Avtaev, V.V.; Yakovlev, N. O.; Erasov, V.S.; Podzhivotov, N. Yu.

doi:10.1134/s0036029519040025

Cited by 3 publications

(1 citation statement)

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“…When the displacement field obtained by DIC technology is used to measure the SIF, it is important to accurately determine the crack tip position. Avtaev et al [5] pointed out that it is difficult to directly identify the position of the crack tip from digital images, and scholars have proposed many methods for this problem. In the area near the crack tip, the growth rate of elastic and plastic strain will increase, and will reach the maximum at the crack tip.…”

Section: Introductionmentioning

confidence: 99%

Optimisation Method for Determination of Crack Tip Position Based on Gauss-Newton Iterative Technique

Yang

Wei

Liang

et al. 2021

Chin. J. Mech. Eng.

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In the digital image correlation research of fatigue crack growth rate, the accuracy of the crack tip position determines the accuracy of the calculation of the stress intensity factor, thereby affecting the life prediction. This paper proposes a Gauss-Newton iteration method for solving the crack tip position. The conventional linear fitting method provides an iterative initial solution for this method, and the preconditioned conjugate gradient method is used to solve the ill-conditioned matrix. A noise-added artificial displacement field is used to verify the feasibility of the method, which shows that all parameters can be solved with satisfactory results. The actual stress intensity factor solution case shows that the stress intensity factor value obtained by the method in this paper is very close to the finite element result, and the relative error between the two is only − 0.621%; The Williams coefficient obtained by this method can also better define the contour of the plastic zone at the crack tip, and the maximum relative error with the test plastic zone area is − 11.29%. The relative error between the contour of the plastic zone defined by the conventional method and the area of the experimental plastic zone reached a maximum of 26.05%. The crack tip coordinates, stress intensity factors, and plastic zone contour changes in the loading and unloading phases are explored. The results show that the crack tip change during the loading process is faster than the change during the unloading process; the stress intensity factor during the unloading process under the same load condition is larger than that during the loading process; under the same load, the theoretical plastic zone during the unloading process is higher than that during the loading process.

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Section: Introductionmentioning

confidence: 99%