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基于垫片时效泄漏模型和应力强度干涉模型建立螺栓法兰连接的模糊可靠性模型。通过对极限状态方程进行模糊化处理,得到了螺栓法兰连接模糊可靠性计算模型,将Monte-Carlo法和有限元法相结合,提出基于有限元的螺栓法兰连接模糊可靠性计算方法,并对该方法进行验证。 相似文献
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采用ANSYS商用有限元分析软件,对常温条件下受内压的螺栓法兰连接膨胀石墨缠绕垫片进行了应力分析,并根据多孔介质模型的泄漏率方程计算出膨胀石墨缠绕垫片在常温条件下的泄漏率。运用有限元计算模型对不同带宽的膨胀石墨缠绕垫片进行了不同条件下的数值模拟,模拟结果与实验结果较好地吻合。模拟结果给出了常温条件下介质内压、螺栓预拉伸力和填料带宽对螺栓法兰连接膨胀石墨缠绕垫片泄漏率的影响。 相似文献
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提出一种通过端盖固定、活塞杆轴向移动,得到预压缩状态模型的Y形圈有限元建模方法,并与传统建模方法进行对比分析。按两种方法建模分析得到的形变位移近似,最大von Mises应力和接触压力的分布相差不大,说明该建模方法可行且更贴近实际安装过程,更合理。 相似文献
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为了研究超长桩在承受水平荷载下的桩侧水平位移和桩侧土压力的理论计算方法,根据有限杆单元的等效荷载求解原理得到与p-y曲线相适应的非线性弹簧的设置方法,建立了超长桩非线性有限杆单元的理论模型;以实际工程为建模背景,通过ABAQUS软件模拟受到水平荷载时的桩侧水平位移和桩侧土压力,并与实际测得的数据进行对比,以验证数值模拟计算结果的准确性。结果表明:当桩端受到水平荷载作用时,桩侧土压力呈“M”型分布;数值模拟结果与实际工程测量数值之间误差较小,通过数值模拟计算得到的桩侧水平位移和桩侧土压力与实测值之间的相对误差分别在5%和2%以内;通过p-y曲线模型计算得到的桩侧土压力曲线与桩侧水平位移曲线与数值模拟计算得到的各点之间的相关系数R2分别为0.97和0.92,两种方法得到的计算结果基本一致;且利用p-y曲线模型进行计算比通过ABAQUS三维有限元软件计算节约了将近60%的计算时间。在实际工程中,可考虑p-y曲线模型作为超长桩的分析计算模型或作为一种辅助验证方法用以验证通过其它方法计算的准确性。 相似文献
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利用有限元分析软件ANSYS对4000 m3大型球罐进行整体建模, 对其在不同操作工况下进行应力分析。同时研究球罐模型的建模方法、各种载荷的施加方法, 并采用ASME规范对球罐支柱和球壳连接处等多个部位进行应力评定, 总结出完整的应力分析方法, 从而为球罐的结构设计提供指导。经计算, 组合工况, 自重+设计压力+25%风载荷+地震载荷应力结果最大, 球壳上最大应力点发生在支柱与球壳连接处的最高点。球罐的最大应力值发生在支撑和球壳的连接部位, 说明支撑与球壳的连接处是薄弱点, 设计时应给予关注, 增加支柱与球壳连接长度能有效降低应力集中水平。 相似文献
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应用不同的理论模型预测了炭黑/橡胶复合材料的热导率,并与实验测试结果进行了对比分析.结果发现,发黑体积份数对炭黑填充胶热导率影响很大,随着炭黑用量的增加,炭黑/橡胶复合材料的热导率逐步增加;炭黑/橡胶复合材料的热导率与炭黑的结构性及形态有关;在低填充份数2%~25%范围内,用Maxwell模型预测N234发黑/橡胶及N134炭黑/橡胶两种复合材料的热导率与实验结果最为接近. 相似文献
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<正>由于气体的搅动,筛孔塔板上的流动是极其复杂的气液两相流。目前两相流理论尚不成熟,未见运用此理论对塔板流速场的研究报道,Zhang和Yu的研究虽考虑了气相对液相流动的影响,但由于利用单相流理论,计算结果与实际情况有较大偏差。本文利用Elghobashi等建立的两相流双流体模型,建立了塔板上气液两相流二维流速场计算模型。在此基础上,通过调整模型参数,考虑了液层高度对塔板上返流区二维流型的影响,建立了模型参数值与液层高度的关系,实现了考虑液层高度影响的二维流动——拟三维流动的模拟。计算结果与Porter的实验结果基本相符。 相似文献
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基于简单碰撞理论,建立了含有无机元素影响的焦炭气化反应动力学模型。建模过程中,考虑了七种无机元素含量、催化/抑制能力以及单一无机元素饱和催化倍率对焦炭反应性的影响。实验部分,选取四种生物质样品置于微型流化床反应器中测试了焦炭反应性,并与模型计算值进行了对比,结果表明模型能够较好预测焦炭反应性,同时表现出对不同样品的适应性。该模型能够通过输入样品特性参数和反应工况条件实现焦炭反应性的定量预测。该模型的建立表明固体燃料通用气化反应的规律是存在的,可以为进一步阐明气化反应规律提供理论参考。 相似文献
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传统水系统优化往往只考虑了新鲜水用量,而忽视了除盐水、除氧水、各等级蒸汽、蒸汽冷凝水、循环冷却水等类型的水,缺乏对各类型水量关联性的研究。针对这种局限性,提出了包含多种类型水的通用用水过程模型,以及通用炼油厂水系统优化的超结构和相应的数学模型,模型中集成了各装置及各种类型水之间关联的物料衡算方程。利用商业软件GAMS对某炼油厂的水系统进行建模求解,案例分析结果表明,除盐水用量有所下降,回用水用量增加,在优化前后雨水量保持469.36 t·h-1的情况下,系统的新鲜水用量从489.44 t·h-1减小到283.94 t·h-1,以系统新鲜水量和雨水量之和为基准,节水率达到21.4%。加工吨原油取水量从0.649 t减小至0.510 t,接近国内先进水平。案例研究表明,提出的优化模型能够有效地计算整个炼油厂水系统的新鲜水用量,验证了该模型的实用性。 相似文献
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提出了一种系统化的基于逻辑与启发性知识的MINLP过程优化综合方法 .该方法将超结构图的拓扑结构分解成特定的几种设备连接类型 ,通过组合形成基于逻辑的混合整数规划模型 ,克服了数学规划法在建模方面所存在的不直观、难于系统化地实现、复杂的超结构模型难于建立等缺点 .模型中还以硬逻辑或启发的形式引入工程经验 ,减小了搜索空间 ,加快了求解速度 .通过化工厂公用工程系统综合的实例 ,将本方法与传统的层次分解法、数学规划法进行了比较 ,证明了其实用性和优越性 相似文献
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Fiber bundle push-out test and image-based finite element simulation for 3D carbon/carbon composites
The interfacial properties such as debond strength, fracture energy release rate in Mode-II and coefficient of friction play important roles in determining the mechanical properties and strength of carbon/carbon (C/C) composites. Push-out tests were conducted on 3D C/C composites and the experimental results were fitted to the shear lag model to determine these interfacial properties. X-ray tomography was used to explore the internal material structure of the composite. The fiber bundle and matrix interfaces were observed as being partially damaged in the tomographic images and the crack network was explored in detail. The tomographic images were also used to reconstruct a finite element (FE) mesh for simulating push-out tests. The interface of the fiber bundle and matrix in the FE mesh was represented by cohesive surfaces with frictional contact. The cohesive surface properties were obtained by matching FE results with the experimental results. The simulations had a good agreement with experiments and values of 0.75 for coefficient of friction, 2–5 N/mm2 for debond stress, 1–4 N/mm2 for clamping stress and 3–6 N/m for fracture energy release rate were obtained as interfacial parameters for the composite. 相似文献
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Dietary control is known to influence diabetic processes. Therefore, the purpose of this work was to determine possible effects brought about by two different dietary protein levels on the nutritional diet utilization in alloxan-diabetic rats. Rats were divided in two groups: 1) One fed on 12% and 2) one a 4% protein diet. Each group was then divided into two subgroups: A) non diabetic and B) diabetic. Weight parameters, food intake, food efficiency (FE), digestive efficiency (DE), metabolic utilization (MU), retained N/ingested N ratio as well as initial and final glycemia were evaluated at the beginning and at the end of the experiment. A decrease in body weight, FE, DE and MU was observed in the control rats of group 2A, in comparison with the group 1A. Experimental diabetes led to increased FE in 1B group in relation to those of group 1A. Also decreased body weight and FE as well as increased food intake and DE were found in the control animals of 2B group. Glycemia increased in diabetic rats as compared with non-diabetic rats, in both groups, 1 and 2. The data suggest that under the experimental conditions cited, both the nutritional utilization of the diet and the diabetogenic status might be modulated by the dietary protein ingested level. 相似文献
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The present research program, based upon the experimental performance of a 20 mm counter-rotating, non-intermeshing twin screw devolatilizer with several polymer/solvent systems has developed theoretical approaches to modeling both the bubble growth dominated mass transfer regime as well as the essentially bubble free regime (1, 2). This work encompasses the area of transition from the bubbling to the non-bubbling areas. This transition to some degree, probably exists in nearly all real devolatilization processes. The work combines a foam simulation model, which integrates elementary bubble processes, with the mass transfer from single phase liquid films through a penetration theory based model. The modeling is successful at correlating the experimental data and shows realistic effects with regard to residence time, surface area, and average mass transfer coefficient as functions of vent loading. 相似文献