Development Of The Axial Compression Buckling Test Platform For Cylindrical Shell

Elephant-foot buckling, as typical damage of oil tanks under earthquake action, always appears at the bottom of the oil tank wall. The instability of cylindrical shell under axial compression, which is closely related with its initial geometric deficiency, constitutes the inner characteristic of elephant-foot buckling. Numerical simulation method, which needs experimental verification, is mainly adopted in the research to study such kind of instability. A test platform, which considers the technology of mechanism, electricity and control, is developed for axial compression buckling on cylindrical shell components. The test platform can be used for the measurement of initial geometric deficiency and buckling critical load of the cylindrical shell. Through testing the impact of initial geometric deficiency on buckling critical load of cylindrical shell can be learned and numerical simulation method can be verified. The main works are concluded as follows:(1) Primarily, both the elastic buckling theory and plastic buckling theory are particularly introduced and theoretical value of buckling critical load of cylindrical shell can be achieved. Subsequently, three finite element analysis models are established, which are ideal cylindrical shell, cylindrical shell under weld distortion and cylinder simulate welds by inherent strain method, respectively, and three values of axial compression critical stress are calculated. The nominal axial pressure of test platform should be bigger than both the theatrical value and the calculated values of buckling critical load of cylindrical shell.(2) The test platform is studied and the mechanical structure of the platform, which composed of both the axial compression loading system and geometry measurement system, is designed for the mechatronics. To satisfy the requirements of plastic buckling experiment for the thick cylindrical shell, hydraulic system is proposed as the axial compression loading system, with its main purpose providing stable axial load for the cylindrical shell. Load cell is applied for the measurement of axial compression on cylindrical shell. Displacement sensor driven by stepping motor is conducted as geometry measurement system, and the precise geometry of the cylindrical shell can be achieved automatically by this system. Moreover, support system and cylindrical shell components are made to meet the standards and requirements of our experiment.(3) Electric control system of the platform for the control of axial compression loading system and geometry measurement system is developed. PLC (programmed logic controller) is adopted as the major component of the control system. The loading process can be stable and automatic through hydraulic valve controlling. The geometry measurement process can be automatic through stepping motor controlling.(4) The platform is debugged and the experimental specimens are processed to make sure the test platform is feasible and reliable. All the experimental data are achieved and treated automatically. The program is made out for the numerical simulation of cylindrical shell under axial compression using geometry data.