Fatigue life prediction under mixed-mode loading using equivalent stress intensity factor models

Abstract

Damage tolerance principles are widely used to assess the structural integrity and failure of engineering components. The advances in numerical simulation techniques facilitate the prediction of fatigue life of engineering component, which is essential in damage tolerance design. For the components under mixed mode (I/II) loading, the fatigue crack growth and life is predicted by using a modified form of Paris' law along with the equivalent stress intensity factor (ΔKeq). Numerous ΔKeq models are available for correlating the equivalent stress intensity factor range and the fatigue crack growth rate. The knowledge of proper ΔKeq model is essential for the accurate fatigue life estimation. In this work, the authors numerically assess the performance of ΔKeq models in mixed mode fatigue life prediction with the help of published experimental mixed mode data.

Fatigue crack growth simulation using the moving mesh technique

“…Figure 6A shows the crack paths of the fatigue tests relative to the loading angles of 30 and 60 predicted by the proposed method and Sajith et al, 24,66 whereas Figure 6B compares the number of remeshing events as a T A B L E 1 Material properties of the plate and loading angles and loading levels assumed in the present study.…”

“…In the present study, for conciseness, the fatigue behavior of the CTS steel specimen is analyzed for the cases of Φ ¼ 30 and Φ ¼ 60 only. In particular, according to Ma et al, 65 The predictions of the proposed method are compared with experimental and numerical results provided by Ma et al 65 and also with numeric previsions achieved by Sajith et al 24,66 and Cheng et al 67 Concerning numerical results, it is worth noting that Ma et al 65 and Sajith et al 24,66 have used standard FEbased numerical models, which update the computational mesh of the numerical model for each increment of the crack length during the propagation process. In particular, for the case of Φ ¼ 30 , Sajith et al 24 report that the crack propagation process has been conducted by extending the crack through incremental steps of size Δa ¼ 0:5 mm starting from the initial crack length of 45 mm to the final length of 65 mm.…”

“…Poisson's ratio (ν) function of the crack length (a) executed by the proposed strategy and the numerical method used by Sajith et al 24,66 In particular, for the proposed method, it is specified when a geometry update takes place because of the occurrence of the condition θ ¼ Toll θ ð Þ. The results denote that the crack paths predicted by the proposed method are in good agreement with those achieved by Sajith et al 24,66 Nevertheless, the results of Figure 6B indicates that the proposed method involves fewer remeshing events than standard FEM procedures to perform the numerical simulations, thus notably reducing the computational honors and the possibility of computational issues when the numerical solution is mapped from the old to the new mesh arrangement.…”

An X-FEM based framework for 3D fatigue crack growth using a B-spline crack geometry description

“…A number of other equations for an equivalent mixed mode stress intensity factor found in literature have also been implemented. An overview and comparison of a number of these models can be found in [37]; a thorough review on mixed-mode fracture of metals can be found in [38]. The oscillating behaviour of the extracted SIF along the crack front can introduce difficulties when performing a FCG analysis; especially for a simulation that requires a large number of iterations.…”

Evolution of Crack Propagation Rate in Notched Specimens Using XFEM Method under Bending Load Condition

“…where,  is geometrical coefficient, 𝜎 𝑡𝑖𝑝 maximal stress at the notch tip. In this test, the specimen is subjected to a mixed mode I and II due to a deviation of crack by a low angle in which mode I appears a predominant mode with higher values compared to mode-II, the stress intensity factor used is the equivalent notch stress intensity factor described by Irwin et al [26,27].…”