Abstract
This work assesses the Crack Compliance Method (CCM), which has been extensively used for the experimental evaluation of residual stresses, by the Finite Element Method (FEM) to validate its experimental applicability through numerical evaluation. The CCM is a very powerful method that is based on Fracture Mechanics theory, but its experimental application and set up has not been totally scientifically validated. In this paper, a numerical evaluation is presented on the basic applications of the CCM. The assessment of the CCM is performed on bending beams with and without prior straining history. To determine the best position and orientation of the strain gages, as well as the optimum number of readings, a number of numerical simulations where also performed for the correct performance of the experimental evaluation of the CCM. The prior straining history condition, in the analyzed components, is induced by an axial pulling before the beam is bent. Three levels of preloading are considered: low, medium and high (which are related to the yield strain of the simulated material); Isotropic and Kinematic hardening rules are also considered. After the residual stress field is induced by bending, a slot cutting is simulated and the strain relaxation produced is captured, which is used later in the CCM program for the quantification of the original residual stress field. The results obtained in this work, provide a quantitative demonstration of the effect of hardening strain on the distribution of the residual stress in beams. In the same manner, the theoretical formulation of the CCM has been evaluated validating the application of this method for the determination of residual stress fields in mechanical components.
Highlights
The Crack Compliance Method (CCM) is based on the cutting of a thin slot of increasing depth into a specimen and measuring the nearby distortion produced using strain gauges [1]
Care was taken to produce small elements (1 mm by 0.5 mm) in the middle section of the beam, where the slot was simulated by deleting elements and the relaxed strain data was obtained for the numerical evaluation of the CCM
Finite Element Method (FEM) could be the best option for the evaluation of the CCM, because there are not external factors that can affect the recalled strain data needed to perform it
Summary
The Crack Compliance Method (CCM) is based on the cutting of a thin slot of increasing depth into a specimen and measuring the nearby distortion produced using strain gauges [1]. The numerical evaluation of the CCM presented in this work is based on the residual stress induction applying pure bending. Care was taken to produce small elements (1 mm by 0.5 mm) in the middle section of the beam, where the slot was simulated by deleting elements and the relaxed strain data was obtained for the numerical evaluation of the CCM. For the cases where prior history was considered, a homogenous pre-strain of the beam was applied before conducting the operation of bending.
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