Abstract
A modified J-integral calculation method is adopted to fix the problem of the quantitative evaluation of the crack propagation of shot-peened structures. Considering the residual stress, residual strain, and residual strain energy, the effect of shot peening on the J-integral parameters of semi-elliptic surface crack fronts is quantitatively calculated and a method is provided for the performance evaluation of the shot peening layer. First, the shot peening process is simulated, then the fatigue crack is generated by changing the constraint condition and a far-field load is applied to calculate the J-integral parameters, crack propagation rate, and crack kinking angle. The effects of different crack depths and shot velocities on the fracture parameters are analyzed. The results show that the reduction in the J-integral value after shot peening decreases with the increase in the crack depth when the shot velocity is a certain value, which indicates that shot peening is more beneficial for suppressing the fatigue crack propagation. When the crack depth is greater than the depth of the compressive stress layer, shot peening accelerates the crack propagation. The reduction in the J-integral value decreases with the increase in shot velocity when the crack depth is a certain value; therefore, increasing shot velocity is more beneficial for retarding fatigue crack propagation.
Highlights
Shot peening is a strengthening process that uses a large number of shots to impact surface materials to cause circulating plastic deformation [1,2]
There is a lack of effective methods for quantitatively assessing the effect of shot peening on fatigue crack propagation life, as assessing crack extension life requires the calculation or measurement of fracture mechanical parameters, such as the J-integral or stress intensity factor at the crack front
The above methods only fit the residual stress distribution after shot peening, based on linear elastic fracture mechanic parameters that do not take into account the effects of work hardening and residual strain energy formed by shot peening and reduce it to a two-dimensional problem, ignoring the complexity of shot peening residual stresses, which inevitably leads to errors in the calculation of fracture parameters at the crack front
Summary
Shot peening is a strengthening process that uses a large number of shots to impact surface materials to cause circulating plastic deformation [1,2]. There is a lack of effective methods for quantitatively assessing the effect of shot peening on fatigue crack propagation life, as assessing crack extension life requires the calculation or measurement of fracture mechanical parameters, such as the J-integral or stress intensity factor at the crack front. The above methods only fit the residual stress distribution after shot peening, based on linear elastic fracture mechanic parameters (stress intensity factors) that do not take into account the effects of work hardening (plastic deformation) and residual strain energy formed by shot peening and reduce it to a two-dimensional problem, ignoring the complexity of shot peening residual stresses, which inevitably leads to errors in the calculation of fracture parameters at the crack front. The effects of the shot peening process and crack depth on the above fracture parameters were investigated to provide a computational method for quantitatively assessing the fatigue crack propagation life of shot-peened layers
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