鈦合金銲接結構具有質量輕、比強度高及耐腐蝕等優點，已被廣泛應用於航太、機械及化工等領域。真空硬銲為在真空中均勻加熱的高品質銲接製程，對於難以銲接的鈦合金零組件製作具有相當的重要性，其銲接件的性質及耐久分析值得探討。本計畫將以Ti-6Al-4V鈦合金真空硬銲為對象，分成兩部分探討。首先建立最佳製程參數組合，品質參數採用抗拉強度及破壞韌性，分別以單目標及多目標最佳化方法進行分析，以適用於不同設計需求。第二部分為建立疲勞裂縫成長速率及裂縫閉合應力資料，探討平均應力及超載負荷之影響，建立此銲接件在變動負荷振幅歷程作用下之最佳疲勞裂縫成長分析模式。並比較真空硬銲件(屬於擴散銲接類)與電子束銲接件(屬於熔融銲接類，在前一期計畫探討)疲勞裂縫成長性質及壽命評估模式之差異。本計畫預期可解決不同設計觀點時之鈦合金真空硬銲最佳製程參數選擇、解決真空硬銲鈦合金的疲勞設計問題、建構鈦合金銲接件的完整疲勞設計及分析方法，其成果將具學術及應用價值，並可提升鈦合金在工業上的應用層次。 ;Titanium alloy weldment has many advantages such as light weight, high strength and corrosion resistance, etc. It has been widely used in aerospace, machinery and chemical industries. Vacuum brazing is a high-quality welding process that the materials are uniformly heated in a vacuum environment. The welding process is of great importance for the production of titanium alloy parts that are difficult to weld. The mechanical properties and durability analysis of vacuum brazed weldments are worth studying. This project will be divided into two parts to explore vacuum brazed Ti-6Al-4V weldment. First of all, the optimal process parameters are set up. Ultimate tensile strength and fracture toughness are selected as targets. Single-objective and multi-objective optimization analyses are applied to meet with different design requirements. The second part is to obtain the fatigue crack growth rate and crack closure stress data, and to investigate the effects of stress ratio and overloading on crack growth. The optimal fatigue crack growth analysis model of this weldment is established under variable amplitude loading history. In addition, we will compare the difference between fatigue life assessment models of vacuum brazed components (belonging to diffusion welding) and electron beam welded components (belonging to fusion welding). The project is expected to solve the following problems: (1) the selection of optimal process parameter combination for vacuum brazed titanium alloy under different design concepts, (2) the fatigue design of vacuum brazed titanium alloy, (3) complete fatigue analysis methods for titanium alloy weldments both with and without cracks. The results of this project will have academic value and promote the industrial application of titanium alloy.
