Stability Research Of Cracked Shuttle Variable Cross Eccentric Compression Thin-walled Column

The structure of thin-walled pillars in modern engineering structure has been widely used because of its excellent mechanical properties and simple construction methods.Steel in the production,processing,transportation process will inevitably exist in a variety of defects,such as smelting due to the production of technical restrictions will be generated in the internal bubbles,slag,processing and transportation process will cause damage to the surface of the material.For thin-walled steel structures,these defects can cause breakage of the material when the cross-sectional stress is much less than the yield strength.The existing thin-walled steel structure design generally according to the strength theory to ensure the safety and durability of the structure,there is no deep consideration for the presence of defects-cracks that are widely present in the components,simply by designing the redundancy to consider the impact of the presence of cracks on the strength of the material,and can't accurately reflect the impact of cracks on the strength of the component.The safety of cracked thin-walled shell structures has been an important issue in the engineering community's general concern and research.In order to establish the safety evaluation method of the shell structure,it is necessary to study the fracture mechanics behavior of the cracked thin-walled shell structure.Based on this,the main contents of this paper are as follows:(1)Study on fracture mechanical behavior of thin-walled cylindrical shell structure under tension loading.In this paper,the finite element analysis software ANSYS was used to study the fracture behavior of thin-walled cylindrical shells with oblique cracks.Calculate the stress intensity factor value of the cracked thin-walled member under tension,The influence of the crack length ?,the tensile stress ?,the inclination angle ?of the crack on the stress intensity factor of the crack on the thin-walled cylindrical shell under tension is analyzed,and the calculated results are compared with the existing calculation results to verify the reliability.(2)Study on fracture mechanics behavior of thin-walled cylindrical shell structures with curved cracks under combined Load.The effects of crack length ?,crack inclination angle ?,bending moment M and other factors on the stress intensity factor of oblique cracks on thin-walled cylindrical shells under combined bending load are studied.The influence of bending load on the stress intensity factor is studied.Finally,the variation curve of stress intensity factor with ? and ? is fitted by numerical calculation to facilitate the engineering design.(3)Based on the theory of the maximum cyclic tensile stress of the composite crack,the number of the singular elements in the crack tip is changed to find the node of the unit with the largest circumferential tensile stress.The I-II compound crack is calculated by the unit node with the largest circumferential tensile stress of the initiation angle ?.The direction of crack initiation can be controlled by the inclination angle of the oblique crack by the finite element simulation and the theoretical analysis.The relationship between the direction of the crack and the crack propagation direction should be paid attention to in the structure with the crack.