The effect of compression stresses, stress level and stress order on fatigue crack growth of multiple site damage

Abstract

Structural components are generally subjected to a wide stress spectrum over their lifetime. Service loads are accentuated at the areas of stress concentration, mainly at the connection of components. When there is a critical level of multiple site damage at connections, cracks link up to form a large crack which abruptly reduces the residual strength of the damaged structural member. Therefore, it is important to estimate the fatigue life before the cracks link up due to critical multiple site damage. In this study, the extended finite element method was applied to predict lifetime under constant amplitude cyclic loadings of fatigue tests on several multiple site damage specimens made of Al 2024‐T3. Then the multiple crack growths under service stress spectra are calculated to investigate the effects of compressive stress, stress orders and the effect of sequence cyclic loadings on stress levels by using Forman and NASGROW equations.

Fatigue surface crack propagation and intersecting cracks in connection with welding residual stresses

“…Special attention should be also paid to multiple crack problems in the field of welding residual stresses. The multiple fatigue crack growth in thin sheet plates is investigated under service loading conditions . Chen has presented a solution for the T‐stress in the case of 2 through‐thickness cracks in a finite plate under different tensile loading conditions.…”

“…The multiple fatigue crack growth in thin sheet plates is investigated under service loading conditions. 37 Chen 38 has presented a solution for the T-stress in the case of 2 through-thickness cracks in a finite plate under different tensile loading conditions. Perl and Steiner 39 have evaluated the stress intensity factor and the T-stress for inner radial or coplanar crack arrays and ring cracks in a spherical pressure vessel by means of 3-dimensional finite element method.…”

Effects of stress ratio on crack growth rate and fatigue strength for high cycle and very-high-cycle fatigue of metallic materials

“…Elber, 1970;Huang and Moan, 2007;Jones et al, 2008;Ostash et al, 2011;Baptista et al, 2012;Kim et al, 2012;Xiong and Hu, 2012;Zambrano et al, 2012). Among these, Elber (1970) introduced the concept of crack closure and used the effective stress intensity factor range DK eff instead of stress intensity factor range DK as the driving force for fatigue crack growth, namely da/dN = C(DK eff ) m , where DK eff = K max À K op , with K max being the maximum stress intensity factor and K op the value corresponding to crack opening stress.…”

Study on life and path of fatigue cracks in multiple site damage plates

“…Wu and Xu presented an analytical method based on the Dugdale strip yield model for MSD problems by using the weight function method [20]. The MSD problems are usually analyzed by using numerical methods rather than the theoretical ones because of the complicated interactions between multiple cracks [2]. Newman Jr. and Ramakrishnan demonstrated that the fatigue life prediction methods based on the fatigue crack growth alone can be used adequately to calculating the life of the fuselage riveted lap joints [21].…”

“…When there is a critical level of MSD at connections, the cracks link up to form a larger crack which abruptly reduces the residual strength of the damaged member. Therefore, it is important to estimate the fatigue life before the cracks link up due to critical MSD [2]. In order to assess the crack link-up with a leading crack which interacting with one or more MSD cracks, experimental tests have been performed on flat panels [1].…”