【摘要】：海洋平臺通常承受較為惡劣的海洋環(huán)境,其中腐蝕是影響其結(jié)構(gòu)安全性極其重要的一個因素,而結(jié)構(gòu)最大極限載荷是評價海洋平臺安全性的重要指標(biāo)。目前,彈塑性大變形的非線性有限元法,是計算結(jié)構(gòu)最大極限載荷的有效方法�？紤]海洋平臺鋼結(jié)構(gòu)中腐蝕的隨機(jī)性,將蒙特卡洛法和隨機(jī)有限元法相結(jié)合,成為研究海洋平臺最大極限載荷的發(fā)展方向之一。因此,對隨機(jī)分布多孔板拉伸最大極限載荷的蒙特卡洛有限元分析具有重要的理論和實際意義。用隨機(jī)分布的多孔板近似替代腐蝕環(huán)境下海洋平臺使用的鋼板,這種近似雖然與真實的腐蝕相差較遠(yuǎn),但是屬于偏保守的估計。由于采用隨機(jī)分布的蒙特卡洛法,可以讓模擬的腐蝕位置和尺寸與真實情況很接近。以981海洋平臺工程項目為背景,以武鋼生產(chǎn)的WDH370鋼板為研究對象,計算隨機(jī)分布多孔板的最大拉伸極限載荷,得出大量樣本數(shù)據(jù)并進(jìn)行數(shù)理統(tǒng)計,研究最大拉伸極限載荷的影響因素,從而獲得具有較高參考價值的數(shù)值仿真結(jié)果和統(tǒng)計規(guī)律。本論文的主要工作包括:采用參數(shù)化建模,協(xié)同計算的方法,實現(xiàn)了從有限元前處理、計算和后處理全過程的完全自動化計算。在MATLAB環(huán)境中,建立隨機(jī)分布多孔板的模型,自動生成腐蝕孔、自動劃分網(wǎng)格;在ABAQUS環(huán)境中,定制了WDH370的雙線性彈塑性應(yīng)力應(yīng)變曲線,開啟了ABAQUS彈塑性和大變形計算選項;在ABAQUS/Python環(huán)境下,實現(xiàn)了ABAQUS計算結(jié)果的自動調(diào)用和有效數(shù)據(jù)導(dǎo)入指定EXCEL電子表格;最終以MATLAB主程序?qū)崿F(xiàn)了彈塑性大變形有限元的完全自動化計算。在沒有人工干預(yù)條件下,一次命令執(zhí)行完成了數(shù)百次預(yù)定的模特卡洛有限元模型的自動計算。數(shù)值計算結(jié)果表明:所建立的計算方法合理、有效而且具有較高的精度。對不同孔洞率(可視為名義腐蝕率DOP)、不同屈強(qiáng)比的隨機(jī)多孔板進(jìn)行計算,提取載荷-位移曲線以及最大極限載荷、位移、彈性剛度等數(shù)據(jù)并進(jìn)行統(tǒng)計分析,發(fā)現(xiàn)結(jié)構(gòu)的剩余極限載荷比值、彈性剛度折減都符合正態(tài)分布并通過檢驗,最終獲得了腐蝕率與屈強(qiáng)比、腐蝕率與屈強(qiáng)比與彈性剛度折減之間的定量統(tǒng)計關(guān)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.
【學(xué)位授予單位】：華中科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：P755.3

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本文編號：2175102