An applied method for fatigue life assessment of engineering components using rigid-insert crack closure model

The purpose of this paper is to provide a new method for analyzing and evaluating the fatigue crack closure load and estimating the life of engineering components using RICC (Rigid-Insert Crack Closure Model), non-destructive replica technique, and a new sample. For this purpose, first, the method of solving the RICC model has been changed from linear approximation to nonlinear state and therefore, a significant improvement in the accuracy of the model results has been achieved. Then, using the model, a new formulation for the influence line in the points of sample is obtained, which has a significant accuracy. The formulation of the RICC model results in a set of equations that can help to determine the closure load and the characteristics of the load-displacement diagram using the residual crack mouth opening displacement in zero load (residual CMOD), which is the only empirical input parameter of Model. The new formulation method has been applied to a standard sample that has the same conditions as a real instance. The amount of residual crack openness in zero load (crack residual displacement) was measured using the replica technique and COD-gage simultaneously on a standard sample and were investigated using the obtained relationships and the accuracy of the outcomes. To prove the reliability, model results have been investigated through doing the experimental tests on aluminum alloys. Finally, the results obtained from the proposed relationship for the analysis and evaluation of the crack closure load and fatigue life were compared with the experimental results, which showed acceptable results.