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391.
Based on the first order shear deformation theory(FSDT), the nonlinear dynamic equations involving transverse shear deformation and initial geometric imperfections were obtained by Hamilton's philosophy. Geometric deformation of the composite cylindrical shell was treated as the initial geometric imperfection in the dynamic equations, which were solved by the semi-analytical method in this paper. Stiffness reduction was employed for the damaged sub-layer, and the equivalent stiffness matrix was obtained for the delaminated area. By circumferential Fourier series expansions for shell displacements and loads and by using Galerkin technique, the nonlinear partial differential equations were transformed to ordinary differential equations which were finally solved by the finite difference method. The buckling was judged from shell responses by B-R criteria, and critical loads were then determined. The effect of the initial geometric deformation on the dynamic response and buckling of composite cylindrical shell was also discussed, as well as the effects of concomitant delamination and sub-layer matrix damages. 相似文献
392.
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394.
This research proposes a bi-level bi-objective model to regulate the usage of rail intermodal terminals for hazardous materials (hazmat) shipments, where government imposes tolls to deter carriers from using certain terminals. The complexity of the resulting mathematical program motivates the development of a hybrid speed-constrained multi-objective particle swarm optimization algorithm, which is then integrated with CPLEX, to solve the model. Through a real problem instance based on the intermodal service chain of Norfolk Southern in US, the toll-setting model is examined and further compared with a regular network design approach, in which certain terminals are closed to hazmat containers. The computational results show that the toll-setting policy is more practical and efficient, and the two models can be combined as a two-stage strategy in long-term hazmat transportation regulations. Additional managerial insights are derived for different stakeholders. 相似文献
395.
研究基于可靠度的方法,对深海复合材料悬链线立管进行优化设计分析。对于正交各向异性层合复合材料结构而言,叠层顺序不同、各层铺角变化以及层间厚度差异等都会影响到结构的承载能力,因此,有必要引进可靠度作为优化设计指标。首先,根据经典层合板理论计算整体模型的等效属性,建立悬链线立管整体分析模型,得到关键截面响应,以此作为局部分析模型的约束;然后,运用试验设计方法构建Kriging近似模型;最后,利用蒙特卡罗撒点方法对比分析确定性优化与可靠性优化的结果。研究表明:优化后的深海复合材料立管在满足应力强度设计的要求下可有效降低结构重量,所提出的基于可靠度的优化设计复合材料悬链线立管具有可行性。 相似文献
396.
文章针对多载荷工况的静强度计算结果,利用FEM软件的二次开发语言和混合编程技术,引入静强度全工况计算及可视化的图形显示,分析全部静强度载荷工况下的材料利用度和其它性能指标参数,对结构的整体静强度性能进行全面、高效、准确地评估,并以重载机车车体为例进行静强度全工况计算的应用研究。 相似文献
397.
With the rapid growth of the offshore engineering sector, studying the durability of offshore structures becomes primordial. Evaluating experimentally the coupling between mechanical and chemical degradation of the cement-based materials and structures is a challenging task because it requires tracking the evolution of the micro-mechanisms associated with the degradation in real time for long periods. To tackle this issue, a numerical approach is proposed, based on the micromechanics and the coupling between a creep-damage model and a chemical model at the microstructural scale. The seawater chemical effect on cement paste is simulated by considering the penetration fronts of the aggressive water and the attack by layers in the material. The aim of this study is to provide a tool for the rapid mechanical evaluation of the offshore structures and therefore a tool that can be used for the optimization and the development of durable marine constructions. The results highlight the competition between protective and damaged layers formed due to seawater attack, and that the global mechanical behaviour strongly depends on the chemically modified phases in the cement paste. 相似文献
398.
针对远海岛礁战储物资的战时供给问题,利用海空协同运输的优势,以系统总时间最短、物资保障成本最低为目标,构建两阶段优化模型(2E-MLRP),并利用解的结构特征改进拥挤度比较算子和精英保留策略,形成有针对性的改进遗传算法。算例分析结果表明:利用本文所建模型及算法求解得到的最优方案符合“性价比”的要求;相对于全海运模型,海空协同的系统总时间降低53.15%,而成本增幅仅为22.27%,且第一批物资送达时间也减少2.95 d。算法对比结果显示:改进后算法得到的SP指标值与MSP指标值均优于传统遗传算法,可知改进后算法求得的Pareto解集具有更好的分布性。本文运输方案与其他方案相比,成本大幅降低,运送时长增幅较小,可保证运输装备的高效利用,且单个航线内待补给岛数量合理,可满足战储物资运送的要求,为战时远海岛礁战储物资供给方案的制定提供参考。 相似文献
399.
The problem with fatigue lifetime estimation of explosive cladded transition joints under random loading conditions has been described. The paper presents the fatigue test results performed for the random state of tension-compression under a generated spectrum according to the Pierson-Moskowitz model. The obtained spectrum has a non-Gaussian characteristic. The tested material consists out of a transition joint clad with four layers of aluminium alloy A5083, A1050, Titanium Grade 1 and steel Grade D. The material has been tested for the existence of residual stresses after the welding process with the hole drilling method. The welding process has been also simulated with ANSYS and the residual stresses have been generated for the Goldak volumetric distribution. The obtained values of residual stresses comprise to the values of real tests performed for the hole drilling method. The information about the residual stress values have been taken into account in the process of fatigue lifetime estimation in the form of non-zero mean stresses compensation inside the clad. The fatigue life has been calculated with the use of the frequency domain method. The Goodman mean stress compensation model has been used in the process of residual stress compensation. The non-gaussianity has been compensated with the use of the Bracessi formula. The obtained fatigue life assessment results have been compared with stand test results. The calculated results are within the scatter area of 3, but individual scatter values have been calculated for calculated series. 相似文献
400.