随机分布多孔板拉伸极限强度的蒙特卡洛有限元分析

发布时间：2018-08-09 19:37

【摘要】：海洋平台通常承受较为恶劣的海洋环境,其中腐蚀是影响其结构安全性极其重要的一个因素,而结构最大极限载荷是评价海洋平台安全性的重要指标。目前,弹塑性大变形的非线性有限元法,是计算结构最大极限载荷的有效方法。考虑海洋平台钢结构中腐蚀的随机性,将蒙特卡洛法和随机有限元法相结合,成为研究海洋平台最大极限载荷的发展方向之一。因此,对随机分布多孔板拉伸最大极限载荷的蒙特卡洛有限元分析具有重要的理论和实际意义。用随机分布的多孔板近似替代腐蚀环境下海洋平台使用的钢板,这种近似虽然与真实的腐蚀相差较远,但是属于偏保守的估计。由于采用随机分布的蒙特卡洛法,可以让模拟的腐蚀位置和尺寸与真实情况很接近。以981海洋平台工程项目为背景,以武钢生产的WDH370钢板为研究对象,计算随机分布多孔板的最大拉伸极限载荷,得出大量样本数据并进行数理统计,研究最大拉伸极限载荷的影响因素,从而获得具有较高参考价值的数值仿真结果和统计规律。本论文的主要工作包括:采用参数化建模,协同计算的方法,实现了从有限元前处理、计算和后处理全过程的完全自动化计算。在MATLAB环境中,建立随机分布多孔板的模型,自动生成腐蚀孔、自动划分网格;在ABAQUS环境中,定制了WDH370的双线性弹塑性应力应变曲线,开启了ABAQUS弹塑性和大变形计算选项;在ABAQUS/Python环境下,实现了ABAQUS计算结果的自动调用和有效数据导入指定EXCEL电子表格;最终以MATLAB主程序实现了弹塑性大变形有限元的完全自动化计算。在没有人工干预条件下,一次命令执行完成了数百次预定的模特卡洛有限元模型的自动计算。数值计算结果表明:所建立的计算方法合理、有效而且具有较高的精度。对不同孔洞率(可视为名义腐蚀率DOP)、不同屈强比的随机多孔板进行计算,提取载荷-位移曲线以及最大极限载荷、位移、弹性刚度等数据并进行统计分析,发现结构的剩余极限载荷比值、弹性刚度折减都符合正态分布并通过检验,最终获得了腐蚀率与屈强比、腐蚀率与屈强比与弹性刚度折减之间的定量统计关系。
[Abstract]:Offshore platforms are usually subjected to a relatively bad marine environment, in which corrosion is an extremely important factor affecting the safety of offshore platforms, and the maximum limit load of structures is an important index to evaluate the safety of offshore platforms. At present, nonlinear finite element method for large elastic-plastic deformation is an effective method for calculating the maximum ultimate load of structures. Considering the randomness of corrosion in steel structures of offshore platforms, the combination of Monte Carlo method and stochastic finite element method has become one of the development directions to study the maximum limit loads of offshore platforms. Therefore, the Monte Carlo finite element analysis of the maximum tensile limit load of randomly distributed perforated plates is of great theoretical and practical significance. The stochastic distribution of perforated plates is used to replace the steel plates used in the corrosion environment. Although this approximation is far from the true corrosion, it is a conservative estimate. Because of the random distribution of Monte Carlo method, the simulated corrosion location and size can be very close to the real situation. Taking the 981 offshore platform project as the background, taking the WDH370 steel plate produced by WISCO as the research object, the maximum tensile limit load of the randomly distributed perforated plate is calculated, and a large number of sample data are obtained and the mathematical statistics are carried out. The influence factors of the maximum tensile limit load are studied, and the numerical simulation results and statistical laws with high reference value are obtained. The main work of this paper is as follows: the method of parametric modeling and collaborative computing is used to realize the complete automatic calculation from the whole process of finite element pre-processing, calculation and post-processing. In MATLAB environment, the model of randomly distributed perforated plates is established, the corrosion holes are generated automatically and the mesh is automatically divided. In the ABAQUS environment, the bilinear elastoplastic stress-strain curves of WDH370 are customized to open the calculation options of ABAQUS elastoplasticity and large deformation. In the ABAQUS/Python environment, the automatic transfer of the results of the ABAQUS calculation and the effective data import to specify the EXCEL spreadsheet are realized, and finally, the elastic-plastic large deformation finite element calculation is realized by the MATLAB main program. In the absence of human intervention, a single command was executed to complete the automatic calculation of a finite element model for several hundred scheduled models. The numerical results show that the proposed method is reasonable, effective and accurate. The random perforated plates with different porosity (nominal corrosion rate DOP),) and different yield ratio are calculated. The load-displacement curve and the data of maximum limit load, displacement, elastic stiffness and so on are extracted and analyzed statistically. It is found that the residual limit load ratio and elastic stiffness reduction of the structure all conform to the normal distribution and through the test, the quantitative statistical relationship between the corrosion rate and the flexural strength ratio, the corrosion rate and the flexural strength ratio and the elastic stiffness reduction is obtained.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P755.3

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