平板裂缝天线钎焊热变形仿真技术的研究

发布时间：2018-02-23 20:23

本文关键词： 平板裂缝天线 ANSYS 真空钎焊接触 FloEFD　出处：《西安电子科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：作为一种应用广泛的天线,平板裂缝天线在钎焊过程中的变形对其电性能有着很大的影响,这也是天线制造精度的主要影响因素之一。为了能够更加准确的对其焊接后的变形进行预测,本文针对平板裂缝天线的真空钎焊过程进行模拟,研究其热变形的仿真技术。具体内容如下:首先,利用有限元分析软件ANSYS对试验模型施加热浸透进行热结构分析,得出网格划分精度及不同的建模方式对其变形场的影响,从而找出相对合理的网格精度及建模方式(即水平钎料建模方式)并应用到后续的研究中。在上述基础上建立平板裂缝天线的有限元模型,并加载环境温度曲线,得到模型的瞬态温度场,采用间接耦合方法对其结构场进行瞬态非线性分析,利用生死单元技术模拟钎料在钎焊中的相变过程,并把温度场载荷作为体载荷施加到结构场中,求解出平板裂缝天线的变形场和应力场,之后,把本文所提出的新的建模方式(水平钎料建模)与以往的建模方式(垂直钎料建模)相对比,充分说明水平钎料建模方式的合理性。最后,利用接触单元模拟天线与夹具之间的摩擦力,使得仿真的设置与实际情况更加接近,计算结果也更准确。其次,在FloEFD软件中利用试验模型对自然对流及强迫对流中换热系数的理论公式进行验证,并总结出强迫对流中的风速和降温时间之间的关系,进一步可得出风速与换热系数间的联系,为后续研究做好铺垫。在ANSYS软件中模拟平板裂缝天线的钎焊过程时,利用所得出的换热系数的公式对两种冷却方式下平板裂缝天线的变形场分别进行了求解,最后结合实际情况进行了分析,说明施加换热系数公式比常数更加接近实际情况。最后,针对影响平板裂缝天线钎焊变形的主要因素(钎料的热膨胀系数、钎料的熔点及钎焊过程中不同的降温曲线),对天线的真空钎焊过程进行模拟,分别找出每种因素对天线最终的变形场及应力场的影响规律,为工程实际中对钎料的选择提供指导建议。
[Abstract]:As a widely used antenna, the deformation of plate crack antenna in brazing process has a great influence on its electrical properties. This is also one of the main factors that affect the precision of antenna fabrication. In order to predict the welding deformation more accurately, this paper simulates the vacuum brazing process of planar slot antenna. The main contents of this paper are as follows: firstly, the thermal structure of the test model is analyzed by using the finite element analysis software ANSYS, and the effect of the mesh division precision and different modeling methods on the deformation field is obtained. Therefore, a relatively reasonable mesh precision and modeling method (i.e. horizontal brazing metal modeling) are found and applied to the subsequent research. On the basis of the above, the finite element model of the plate crack antenna is established, and the ambient temperature curve is loaded. The transient temperature field of the model is obtained. The transient nonlinear analysis of the structure field is carried out by indirect coupling method. The phase transition process of the solder during brazing is simulated by using the birth and death element technique, and the temperature field load is applied to the structure field as the bulk load. The deformation field and stress field of the plate crack antenna are solved. After that, the new modeling method (horizontal brazing metal modeling) proposed in this paper is compared with the previous modeling method (vertical brazing metal modeling). Finally, the contact element is used to simulate the friction between the antenna and the fixture, which makes the simulation more close to the actual situation, and the calculation results are more accurate. The theoretical formula of heat transfer coefficient in natural convection and forced convection is verified by using test model in FloEFD software, and the relationship between wind speed and cooling time in forced convection is summarized, and the relation between wind speed and heat transfer coefficient can be obtained. When simulating the brazing process of the plate crack antenna in ANSYS software, the deformation field of the plate crack antenna under two cooling modes is solved by using the formula of the heat transfer coefficient obtained. Finally, combined with the actual situation, it is shown that the formula of applying heat transfer coefficient is closer to the actual situation than the constant. Finally, the main factors affecting the brazing deformation of the plate crack antenna (the coefficient of thermal expansion of the solder) are discussed. The melting point of the filler metal and the different cooling curves during the brazing process are simulated, and the influence of each factor on the final deformation field and stress field of the antenna is found out respectively. To provide guidance for the selection of solder in engineering practice.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN823.24;TG454

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