Research on characterizing the mode Ⅰ stress intensity factors using the finite element-based virtual fields method
The virtual fields method(VFM)is an important method for solving mechanical inverse problems.Recently,VFM has been rapidly developed and widely used for characterizing the constitutive parameters of materials.To improve the parameter characterization capability of VFM,a strategy for identifying the stress intensity factors(SIFs)based on the VFM was investigated in this study.For this method,the sector area was selected with the crack tip as the center for analysis,while the governing equations characterizing the stress intensity factor were established on this basis by Williams'series expansions in stress form and the principle of virtual work.Furthermore,the noise immunity under two different strategies for selecting the virtual fields was analyzed by numerical experiments.Based on the digital image correlation(DIC)and single edge notched tensile(SENT)tests,mode I SIFs of the laser-repaired GH4169 specimens were characterized using VFM,and the results were compared with those of the least-squares method(LSM)which was based on the Williams'series expansions in displacement form.The results of this study show that there is an obvious linear relationship between the SIFs by VFM and the external loads under the small-scale yielding(SCY)conditions.Moreover,the relative errors of VFM are smaller than those of LSM.The above research results demonstrate that the VFM has a promising development in the field of fracture mechanics.
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