Research On Stress And Strain Field And Plastic Zone At Tip Of Small Crack

In practical conditions, overall fracture accident of many components did not start fromthe expected length of cracks, but from small crack defect of some which people paid noattention to. However, the current research on the small crack defect is not many, so this paperfocuses on analyzing the fracture mechanics parameter of small crack tip, researchingcontents are as follows:(1) Based on size requirements of the crack defects component according toelastic-plastic fracture mechanics, the sample model, material model and finite element modelwere determined in this article;(2) For components containing defect crack, expansion characteristics have a certainrelationship with stress and strain fields near crack tip, so in order to accurately analyzeextended features of crack tip when the crack length changes,stress intensity factor KIof nearcrack tip is a constant loading condition; and stress and strain fields near the crack tip isanalyzed by numerical simulation;(3) For components containing defect crack, J-integral near crack tip is relatively stable,therefore, the changes of fracture mechanics parameter J-integral value near crack tip isdiscussed, and the impact of its changes to the propagation characteristics of the crack tip isanalyzed combined with theory;(4) Effect of small crack length on characteristics of crack tip plastic zone is discussedin detail, and using finite element calculations, amendments are proposed on small crack tipplastic zone for hardening material;(5) According to the related theory of elastic-plastic fracture mechanics and combinedwith the practical engineering problems, we know that changes of load, material yieldstrength and strain hardening exponent have a certain influence on the plastic zone of nearcrack tip, so the thesis discusses single parameter change on the impact of plastic zone of nearsmall crack tip, and corrects it. Changes and expansion characteristics of stress and strain fields at crack tip are analyzed.