scholarly journals Determination of the Enhancement or Shielding Interaction between Two Parallel Cracks under Fatigue Loading

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1331 ◽  
Author(s):  
Zhichao Han ◽  
Caifu Qian ◽  
Lanqing Tang ◽  
Huifang Li
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Fatigue Loading ◽  
304 Stainless Steel ◽  
Shielding Effect ◽  
Stress Distributions ◽  
Intensity Factors ◽  
Parallel Cracks ◽  
Two Parallel Cracks

In this paper, the interactions between two parallel cracks are investigated experimentally and numerically. Finite element models have been established to obtain the stress intensity factors and stress distributions of the parallel cracks with different positions and sizes. Fatigue crack growth tests of 304 stainless steel specimens with the single crack and two parallel cracks have been conducted to confirm the numerical results. The numerical analysis results indicate that the interactions between the two parallel cracks have an enhancement or shielding effect on the stress intensity factors, depending on the relative positions of the cracks. The criterion diagram to determine the enhancement or shielding effect between two parallel cracks is obtained. The changes of the stress fields around the cracks have been studied to explain the mechanism of crack interactions.

scholarly journals Investigation of the Enhancement Interactions between Double Parallel Cracks on Fatigue Growth Behaviors

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 2952
Author(s):  
Zhichao Han ◽  
Caifu Qian ◽  
Huifang Li
Keyword(s):  
Stress Intensity ◽  
Crack Growth ◽  
Stress Intensity Factors ◽  
Growth Rates ◽  
Shielding Effect ◽  
Enhancement Effect ◽  
Intensity Factors ◽  
Single Crack ◽  
Parallel Cracks ◽  
Crack Growth Rates

In this paper, interactions of double parallel cracks were studied by performing experiments and numerical simulations. Fatigue crack propagation tests were carried out to measure crack growth rates in the specimens with double parallel cracks or a single crack. Finite element method was adopted to calculate stress intensity factors at the crack tips. Results show that the double parallel cracks at different positions present a shielding effect or enhancement effect on crack growth rates and stress intensity factors. When the double parallel cracks are offset, crack interactions mostly behave as enhancement effects. Empirical formulas were obtained to calculate the stress intensity factor at the “dangerous” crack tip of the double parallel cracks. By modifying the material parameters in Paris equation of the single crack, the double parallel cracks are simplified into a single crack with the same crack growth rates.

scholarly journals Effect of Couple Stresses on the Stress Intensity Factors for Two Parallel Cracks in an Infinite Elastic Medium under Tension

2012 ◽  
Vol 2012 ◽  
pp. 1-14 ◽  
Author(s):  
Shouetsu Itou
Keyword(s):  
Stress Intensity ◽  
Boundary Conditions ◽  
Elastic Medium ◽  
Stress Intensity Factors ◽  
Couple Stress Theory ◽  
Intensity Factors ◽  
Dual Integral Equations ◽  
Couple Stresses ◽  
Parallel Cracks ◽  
Two Parallel Cracks

Stresses around two parallel cracks of equal length in an infinite elastic medium are evaluated based on the linearized couple-stress theory under uniform tension normal to the cracks. Fourier transformations are used to reduce the boundary conditions with respect to the upper crack to dual integral equations. In order to solve these equations, the differences in the displacements and in the rotation at the upper crack are expanded through a series of functions that are zero valued outside the crack. The unknown coefficients in each series are solved in order to satisfy the boundary conditions inside the crack using the Schmidt method. The stresses are expressed in terms of infinite integrals, and the stress intensity factors can be determined using the characteristics of the integrands for an infinite value of the variable of integration. Numerical calculations are carried out for selected crack configurations, and the effect of the couple stresses on the stress intensity factors is revealed.

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