Comparison of fatigue crack growth stress ratio effects under simple variable amplitude loading using fractographic and strain measurements

Kandwal

Proceedings of the Institution of Mechanical Engineers, Part C:

2022

Many engineering components are subjected to random nature of loading during their life period. In this work, the fatigue crack growth in friction stir welded dissimilar AA6061 and AA7075 was investigated under different stress ratio. AA6061 was kept on the advancing side due to having a higher solidus temperature and softer than AA7075 for smooth material flow. The microstructure characterization, tensile and crack growth behavior was studied. It was observed that the joint material exhibited lower strength and ductility as compared to the base material. About 41%, 34%, and 66% reduction in tensile strength, yield strength, and percentage of elongation as compared to AA6061 (base material) were observed. About 27% higher hardness in the HAZ of retreating side than the advancing side was noticed. The crack deflection and tortuosity features were observed in the fatigue fractured specimens. In this paper, a comparative study using different crack growth models has been studied and a simple crack growth rate equation has been proposed considering the crack closure effect.

Section: Crack Growthmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Stress ratio effect on crack growth behavior of dissimilar friction stir welded butt joint between AA6061 and AA7075 alloys

Kandwal

Proceedings of the Institution of Mechanical Engineers, Part C:

2022

“…As shown in Figure 8d, the ball bearing measured by the sensor are located in the spindle. The crack size variables used in the simulation of faulty bearings are the crack-outer ring thickness ratio a/t and the crack length-outer ring width ratio c/b; these two variables are important parameters to measure and calculate the crack size [26]. At the same time, the ratio of the crack depth a and the crack width c to the thickness t and the width b of the bearing outer ring can reflect the damage degree of the crack to the bearing outer ring more clearly.…”

Section: Analog Simulationmentioning

confidence: 99%

“…However, the bending stress exerted by the rolling elements on the outer ring during the process of passing through the spalling position of the outer ring was not taken into account in the study, and the bending stress may also be the reason for the initiation and propagation of the cracks. Researchers [23][24][25][26][27][28] have conducted deep analyses on the crack formation mechanism of the cracks under contact stress. On the basis of the principle of fracture mechanics, the influence of cracks caused by bending moment on stiffness can be analyzed by calculating the strain energy caused by cracks [29][30][31].…”

Section: Introductionmentioning

confidence: 99%

A Theoretical Model with the Effect of Cracks in the Local Spalling of Full Ceramic Ball Bearings

et al. 2019

For full ceramic ball bearings, cracks occur frequently in the spalling on the rings, which leads to impacts on the bearing dynamic characteristics. In this paper, the spalling is set on the outer ring, and the dynamic model considering the effect of crack is proposed. The crack is considered to be related to the strain energy, and the effect on the stiffness of the outer ring is also analyzed. Results show that the appearance of cracks leads to the reduction of the full ceramic bearing stiffness, and the vibration amplitude of bearing increases. The effect of a crack depends on its size, and the vibration of the bearing with cracks of different widths and depths vary greatly. This study provides theoretical basis for the calculation of full ceramic bearing and is of great significance for the state monitoring and fault diagnosis.

“…The load ratio is a factor that exerts a noteworthy influence on the growth of fatigue cracks and exhibits a distinct effect on the occurrence of threshold behavior [6][7][8][9][10][11]. Furthermore, the range of stress intensity factors represents the disparity between the maximum and minimum stress intensity factors experienced during each loading cycle.…”

Section: Introductionmentioning

confidence: 99%

Fatigue Crack Growth Analysis in Modified Compact Tension Specimen with Varying Stress Ratios: A Finite Element Study

Alshoaibi

2023

Applied Sciences

In this study, the primary objective is to analyze fatigue crack propagation in linear elastic fracture mechanics using the SMART crack growth module in the ANSYS Workbench, employing the finite element method. The investigation encompasses several crucial steps, including the computation of stress intensity factors (SIFs), determination of crack paths, and estimation of remaining fatigue life. To thoroughly understand crack behavior under various loading conditions, a wide range of stress ratios, ranging from R = 0.1 to R = 0.9, is considered. The research findings highlight the significant impact of the stress ratio on the equivalent range of SIFs, fatigue life cycles, and distribution of deformation. As the stress ratio increases, there is a consistent reduction in the magnitude of the equivalent range of stress intensity factor. Additionally, a reciprocal relationship is observed between the level of X-directional deformation and the number of cycles to failure. This indicates that components experiencing lower levels of deformation tend to exhibit longer fatigue life cycles, as evidenced by the specimens studied. To verify the findings, the computational results are matched with the crack paths and fatigue life data obtained from both experimental and numerical sources available in the open literature. The extensive comparison carried out reveals a remarkable level of agreement between the computed outcomes and both the experimental and numerical results.