유한요소해석에 기반한 다상 및 다중 물리 사례에 대한 연구

Abstract

Finite element analysis (FEA) is an effective problem-solving tool that enables predictive analysis of problems and simulates even complex physical deformation. In this study, two case studies will be conducted according to the strategy using the finite element analysis method, which can visualize flow and express thermal-mechanical characteristics. The first is the performance characterization of a liquid-solid cyclone using high viscosity oil. Cyclone separator are active filtering devices that recycles wastewater, oil and cleans air pollution. Because internal flow of cyclone by the vortex is highly complicated, the performance and flow patterns of these filters should be thoroughly researched. Generally, studies on gas-solid cyclones are conducted, numerical studies on cyclones that utilize higher-viscosity oil are limited. In this study, a liquid-solid cyclone injected with high-viscosity cutting-oil containing various sized-particles was comprehensively investigated. The reliability of the CFD (Computational Fluid Dynamics) method was verified through comparison with the experimental results. Three models with different geometries were considered for the analysis. One model was used for CFD verification; the remaining two models were added sockets of length extension and shape change to the bottom of the hopper to improve performance. The models that changed the shape of the hopper, thus directly affecting the cyclone performance, were investigated, and each model was qualitatively compared using a validated method. In addition, the particle separation efficiency was evaluated by focusing on the velocity distribution to quantitatively confirm the influence of changing the shape of the hopper. Consequently, the tangential velocity was determined to be similar, but the axial velocity was different, and the change in the velocity of transport for particles affected the filter function. The second is the prediction of thermal-mechanical fatigue life of BGA. The BGA is a package type that mechanically and electrically connects chips and substrates using solder balls. Since high density mounting is possible in a small area, it is used as a high-performance automotive semiconductor package. However, the semiconductor package consists of various materials with differences in coefficients of thermal expansion, it is exposed to fatigue under the condition of cyclic thermal load. In particular, it is important to ensure the reliability for solder joint of a fine pitch that is easily fractured when warpage occurs due to thermal deformation. If the material properties of the solder with viscoplasticity are not suitable, the simulation results may be different from the actual one. Therefore, an appropriate analysis method is required. In this study, thermal-mechanical fatigue analysis of solder was conducted using the Anand model, which representing the behavior of viscoplasticity. In addition, the fatigue life prediction of three materials was carried out, and each material is 63Sn37Pb, SAC 305 and 48Sn52Bi. The SAC305 is a material that is replacing by lead solder by environmental regulations, and 48Sn58Bi is low temperature solder used to compensate for the disadvantages of SAC305. As a result, it confirmed that the fatigue life was the best in 63Sn37Pb and that it was lower in 48Snn58Bi than other materials.