發(fā)布時(shí)間：2018-02-23 20:23

  本文關(guān)鍵詞： 平板裂縫天線 ANSYS 真空釬焊 接觸 FloEFD　出處：《西安電子科技大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：作為一種應(yīng)用廣泛的天線,平板裂縫天線在釬焊過(guò)程中的變形對(duì)其電性能有著很大的影響,這也是天線制造精度的主要影響因素之一。為了能夠更加準(zhǔn)確的對(duì)其焊接后的變形進(jìn)行預(yù)測(cè),本文針對(duì)平板裂縫天線的真空釬焊過(guò)程進(jìn)行模擬,研究其熱變形的仿真技術(shù)。具體內(nèi)容如下:首先,利用有限元分析軟件ANSYS對(duì)試驗(yàn)?zāi)Ｐ褪┘訜峤高M(jìn)行熱結(jié)構(gòu)分析,得出網(wǎng)格劃分精度及不同的建模方式對(duì)其變形場(chǎng)的影響,從而找出相對(duì)合理的網(wǎng)格精度及建模方式(即水平釬料建模方式)并應(yīng)用到后續(xù)的研究中。在上述基礎(chǔ)上建立平板裂縫天線的有限元模型,并加載環(huán)境溫度曲線,得到模型的瞬態(tài)溫度場(chǎng),采用間接耦合方法對(duì)其結(jié)構(gòu)場(chǎng)進(jìn)行瞬態(tài)非線性分析,利用生死單元技術(shù)模擬釬料在釬焊中的相變過(guò)程,并把溫度場(chǎng)載荷作為體載荷施加到結(jié)構(gòu)場(chǎng)中,求解出平板裂縫天線的變形場(chǎng)和應(yīng)力場(chǎng),之后,把本文所提出的新的建模方式(水平釬料建模)與以往的建模方式(垂直釬料建模)相對(duì)比,充分說(shuō)明水平釬料建模方式的合理性。最后,利用接觸單元模擬天線與夾具之間的摩擦力,使得仿真的設(shè)置與實(shí)際情況更加接近,計(jì)算結(jié)果也更準(zhǔn)確。其次,在FloEFD軟件中利用試驗(yàn)?zāi)Ｐ蛯?duì)自然對(duì)流及強(qiáng)迫對(duì)流中換熱系數(shù)的理論公式進(jìn)行驗(yàn)證,并總結(jié)出強(qiáng)迫對(duì)流中的風(fēng)速和降溫時(shí)間之間的關(guān)系,進(jìn)一步可得出風(fēng)速與換熱系數(shù)間的聯(lián)系,為后續(xù)研究做好鋪墊。在ANSYS軟件中模擬平板裂縫天線的釬焊過(guò)程時(shí),利用所得出的換熱系數(shù)的公式對(duì)兩種冷卻方式下平板裂縫天線的變形場(chǎng)分別進(jìn)行了求解,最后結(jié)合實(shí)際情況進(jìn)行了分析,說(shuō)明施加換熱系數(shù)公式比常數(shù)更加接近實(shí)際情況。最后,針對(duì)影響平板裂縫天線釬焊變形的主要因素(釬料的熱膨脹系數(shù)、釬料的熔點(diǎn)及釬焊過(guò)程中不同的降溫曲線),對(duì)天線的真空釬焊過(guò)程進(jìn)行模擬,分別找出每種因素對(duì)天線最終的變形場(chǎng)及應(yīng)力場(chǎng)的影響規(guī)律,為工程實(shí)際中對(duì)釬料的選擇提供指導(dǎo)建議。
[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.
【學(xué)位授予單位】：西安電子科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TN823.24;TG454

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