本研究旨在利用有限元素法模擬起重機吊環閃焊製程之暫態熱電固耦合分析，利用CAD軟體建立圓環模型並輸入至ABAQUS進行模擬。為確保有限元素分析結果與實際閃焊製程相符，本研究探討材料於不同溫度之熱性質、彈塑性變形及導電性質。閃焊製程分為預熱、閃光及頂鍛三階段，不同階段中治具與電極會對圓環施加位移及功率，本研究依照閃焊機台參數設定有限元素模型之邊界條件。藉由分析焊面溫度、焊面殘留應力、治具施力及焊面夾雜物擠出推論可能導致閃焊失敗之因素，並進行更改製程參數之有限元素分析，比較更改製程參數之分析結果是否改善。經由分析結果可得知，對模型A而言，將預熱位移之製程參數從2 mm更改為3.5 mm有效改善焊面加熱不均勻之問題，並降低治具施力，減少圓環內部產生裂痕之風險。將頂鍛位移從5 mm提升至7.5 mm可有效提升焊面夾雜物經由刮渣程序排除之刮渣比例，並減少正向殘留應力之生成，進而提升焊面之機械性質。對模型B而言，於閃焊前對母環進行加熱可在不更改製程參數的前提下提升預熱階段之焊面溫度，並解決模型B閃光階段時間過長之問題。

This study aims at the investigation of the transient thermo-electro-structural coupled analysis for lifting chain flash welding process. The analysis was concluded by finite element software ABAQUS. For the purpose of ensuring accuracy of simulation, this study investigates temperature-dependent material properties such as thermal conductivity, specific heat, Young’s modulus, stress-strain relation and electrical conductivity. To complete the flash welding, the process includes three steps: pre-flash, flash, and upset. In each step, the boundary conditions for clamping and applied voltages are input in the software according to experimental data acquired by the flash-welding machine. In this study, the finite element model is used to simulate temperatures of the welding surface, residual stresses on the welding surface, clamping forces, and extrusion displacements of the welding surface. Two models with different dimensions and configurations are considered. For model A, the single ring type of the lifting chain model is analyzed. The simulation results showed that the increase of pre-flash displacement from 2mm to 3.5mm can improve uniformity of temperatures on welding surface. It is also shown that the decrease of clamping forces can reduce the risk of crack initiation on welding surface. By increasing upset displacement from 5mm to 7.5mm, the extrusion from welding surface is also increased, avoiding tensile residual stresses occurrence. For model B, the double ring type of the lifting chain model is analyzed. It is found that by pre-heating full model before pre-flash process can increase power absorbed by welding surface and decrease flashing time. Based on the numerical results from finite element analysis, the main parameters that affect the flash-welding process can be identified. The optimum process parameters can be also investigated to insure the quality of the process.

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