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Modeling, analysis and optimization of cylindrical stiffened panels for reusable launch vehicle structures.

機(jī)譯：用于可重復(fù)使用運(yùn)載火箭結(jié)構(gòu)的圓柱形加勁板的建模，分析和優(yōu)化。

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The design of reusable launch vehicles is driven by the need for minimum weight structures. Preliminary design of reusable launch vehicles requires many optimizations to select among competing structural concepts. Accurate models and analysis methods are required for such structural optimizations. Model, analysis, and optimization complexities have to be compromised to meet constraints on design cycle time and computational resources.; Stiffened panels used in reusable launch vehicle tanks exhibit complex buckling failure modes. Using detailed finite element models for buckling analysis is too expensive for optimization. Many approximate models and analysis methods have been developed for design of stiffened panels.; This dissertation investigates the use of approximate models and analysis methods implemented in PANDA2 software for preliminary design of stiffened panels. PANDA2 is also used for a trade study to compare weight efficiencies of stiffened panel concepts for a liquid hydrogen tank of a reusable launch vehicle. Optimum weights of stiffened panels are obtained for different materials, constructions and stiffener geometry. The study investigates the influence of modeling and analysis choices in PANDA2 on optimum designs.; Complex structures usually require finite element analysis models to capture the details of their response. Design of complex structures must account for failure modes that are both global and local in nature. Often, different analysis models or computer programs are employed to calculate global and local structural response. Integration of different analysis programs is cumbersome and computationally expensive.; Response surface approximation provides a global polynomial approximation that filters numerical noise present in discretized analysis models. The computational costs are transferred from optimization to development of approximate models. Using this process, the analyst can create structural response models that can be used by designers in optimization. It allows easy integration of analysis models in optimization.; The dissertation investigates use of response surface approximations for integrating structural response obtained from a global analysis in the local optimization of stiffened panels. In addition, response surfaces are used for correcting structural response predictions from a low fidelity model with a few expensive detailed finite element analyses.
機(jī)譯：可重復(fù)使用的運(yùn)載火箭的設(shè)計(jì)受到對最小重量結(jié)構(gòu)的需求的驅(qū)動(dòng)。可重復(fù)使用運(yùn)載火箭的初步設(shè)計(jì)需要許多優(yōu)化，以便在競爭性結(jié)構(gòu)概念中進(jìn)行選擇。這種結(jié)構(gòu)優(yōu)化需要精確的模型和分析方法。必須犧牲模型，分析和優(yōu)化的復(fù)雜性，以滿足設(shè)計(jì)周期和計(jì)算資源的約束?？芍貜?fù)使用的運(yùn)載火箭油箱中使用的加勁板表現(xiàn)出復(fù)雜的屈曲破壞模式。使用詳細(xì)的有限元模型進(jìn)行屈曲分析對于優(yōu)化而言過于昂貴。已經(jīng)開發(fā)出許多用于加筋板設(shè)計(jì)的近似模型和分析方法。本文研究了在PANDA2軟件中實(shí)現(xiàn)的近似模型和分析方法在加筋板的初步設(shè)計(jì)中的應(yīng)用。 PANDA2還用于貿(mào)易研究，以比較可重復(fù)使用運(yùn)載火箭的液態(tài)氫儲(chǔ)罐的加強(qiáng)板概念的重量效率。對于不同的材料，構(gòu)造和加勁肋幾何形狀，可以獲得最佳的加勁板重量。該研究調(diào)查了PANDA2中的建模和分析選擇對最佳設(shè)計(jì)的影響。復(fù)雜結(jié)構(gòu)通常需要有限元分析模型來捕獲其響應(yīng)的詳細(xì)信息。復(fù)雜結(jié)構(gòu)的設(shè)計(jì)必須考慮到本質(zhì)上是全局和局部的故障模式。通常，使用不同的分析模型或計(jì)算機(jī)程序來計(jì)算全局和局部結(jié)構(gòu)響應(yīng)。不同分析程序的集成麻煩且計(jì)算量大。響應(yīng)面近似提供了一個(gè)全局多項(xiàng)式近似，可以過濾離散化分析模型中存在的數(shù)值噪聲。計(jì)算成本從優(yōu)化轉(zhuǎn)移到近似模型的開發(fā)。使用此過程，分析師可以創(chuàng)建結(jié)構(gòu)響應(yīng)模型，設(shè)計(jì)人員可以在優(yōu)化過程中使用該模型。它允許在優(yōu)化中輕松集成分析模型。本文研究了響應(yīng)面近似的使用，以整合從整體分析中獲得的結(jié)構(gòu)響應(yīng)，以對加筋板進(jìn)行局部優(yōu)化。此外，響應(yīng)面用于通過一些昂貴的詳細(xì)有限元分析來校正來自低保真度模型的結(jié)構(gòu)響應(yīng)預(yù)測。

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