Residual Ultimate Strength Analyses Of Cracked Thin-Walled Shell Structures

With the development of science and technology,thin shell structures are widely used in shopping malls,offshore platforms and so on.Its material is steel with high strength and good toughness.However,cracks and other defects will occur in the process of steel processing.Under the action of external loads,stress concentration occurs at the crack tip and plastic zone appears.With the expansion of plastic zone,the structure will yield in a large range or in an allround way,thus reducing its ultimate strength.In order to scientifically evaluate the safety performance of structures after cracks appear,it is necessary to systematically study the influence of crack characteristics on the residual ultimate strength of structures.Based on the literature on residual ultimate strength of cracked thin-walled plates and stiffened plates,and considering the economic and time cost of large-scale crack characteristics for residual ultimate strength test of cracked thin-walled shells,the influence of crack characteristics and initial geometric imperfections on residual ultimate strength of cracked structures is analyzed by numerical simulation.Combining with the research focus of this paper,the following aspects of work have been accomplished:1.The method of establishing crack characteristics in the finite element model of thin shell structures is described.In order to accurately analyze the effect of crack characteristics on the residual ultimate strength of structures with cracks,the relevant laws are found when the length of oblique cracks and circumferential cracks are equal.The specific data of relevant crack characteristics are listed.2.The residual ultimate strength of a cylindrical shell with a central penetrating crack is simulated by considering the material nonlinearity and the geometrical nonlinearity of the structure under axial tension load,and the variation of the residual ultimate strength of a cracked structure with the characteristics of the crack is analyzed.Through special data processing methods,the effects of relative crack length and crack inclination on the relative residual ultimate strength of cracked structures are studied,so as to provide some reference for subsequent accurate evaluation of the richness of residual ultimate strength of cracked structures and appropriate repair methods.3.The residual ultimate strength of thin-walled cylindrical shells with cracks is simulated by finite element method considering the cracks existing in the structure and the initial geometric imperfections in the structure under axial compression load.The influence of crack characteristics and initial geometric imperfections on the residual ultimate strength of thinwalled cylindrical shells with cracks is analyzed by controlling variables.