【作者】 张思斯；

【导师】 王德禹；

【作者基本信息】 上海交通大学 ， 工程力学， 2009， 硕士

【摘要】 在实际工程中,热分析是一项重要的工作。许多设备都具有严格的变形要求,需要了解其在工作和加工过程中的温度和温度应力、温度变形情况。扫描辐射计是卫星上的空间系统,其精度要求达到10-6m。为了了解扫描辐射计光学系统在太空中恶劣的温度环境下,其变形量和应力值是否满足设计要求,使用有限元方法计算其危险时段(春分,秋分,8.8+,8.8-)的应力与变形情况。将危险时段的工作温度场局部加密后由Patran加载到光学相机上,需要加载的温度场是一批十分庞大的数据。为了实现庞大的多场条件加载,通过对Patran加载场数据过程的研究,提出从bdf文件入手,用第三方软件Matlab内置插值函数为核心、VC++为文件接口,直接生成相应的bdf文件中温度载荷卡片并写入bdf文件中,以实现加载过程的自动化。以Patran为参考标准,用简单算例比较Matlab插值程序生成的场与Patran自身生成的场在计算结果之间的差异,以说明Matlab生成场方法的计算精度与可行性。高密度聚乙烯是一种迅速发展的材料,具有良好的放水性能与保温性能,设计在近海区域采用注塑的方法制作海底抽水管道。为了对制管设备的设计和采购提供参考数据,用有限元软件Nastran对高密度聚乙烯的冷凝过程做数值模拟。但是由于高密度聚乙烯的密度随温度变化显著,因此其冷凝过程会由于热胀冷缩带来一个在空间上比较显著的非线性的过程。并且由于其热传导系数小,所以冷凝过程会是一个比较漫长的过程。而在有限元软件Nastran的热分析计算中,密度参数只提供了常量的设定方式,因此在计算长时间的冷凝过程时会带来较大的误差。为了模拟有限元网格的非线性变化过程,从两个思考角度,提出直接将时间分段、按照在每个计算时段中修正网格的计算方法;和固定网格、按照温度修正热传导系数后直接进行非线性计算两种计算方法。在分步修正网格计算中,不断增加步数,减少步长,以研究结果的收敛特点。再设置极端的热传导系数,判断结果的收敛区间。通过分析两种方法的计算结果,讨论方法的可行性、比较两种方法的优劣。更多还原

【Abstract】 Thermal analysis is an important mission in manufacture. Many kinds of devices are required strict precisions. So the temperature、thermal stress and displacement of the devices in their working environment and the manufacturing process should be known.Radiometer is a device working in the space. Analyzing the thermal stress and displacement is a crucial task for knowing whether the device can work in the terrible temperature condition. The thermal analysis can be a hard task because of the huge amount of the temperature multi-fields which can not be typed or imported to the FEA software easily. For inputting the data into the software, a new way is created. Doing the interpolation by Matlab then writing down the result into the bdf file in the bdf thermal load format can get a familiar thermal field with the Patran’s and make the data inputting automatic. Comparing the answer of Patran field with the Matlab’s to prove the feasibility of the Matlab field. Then the huge temperature data can be inputted into the bdf file.High Density Polyethylene (HDPE) is a material with excellent properties of water resisting and heat insulation. Analyzing thermal problems of HDPE can be helpful to choose or design the device of manufacturing HDPE pipe. But the materials like HDPE have a big coefficient of linear expansion, so when their temperature change in a huge range, the volume and the shape of the material may change in a big degree, too. And in the FEA work, the density of the material can only be fixed to one number, so especially in a long time process, the result can not be as accurate as it should be. Consider two ways to deal with this nonlinear problem. First, separate the whole time into several steps and adjust the FEA model in every step to simulate the change of the model. Second, fix the FEA model then adjust the conductivity of the material as if the model is changing before the analysis begin. Then increase the number of steps and decrease the length of steps to study the change of the result. And set a extreme conductivity to get the range of the result. Compare the results of the two methods to prove the feasibility of the methods and find the better way.更多还原