Ti-6AI-超塑性行爲模式參數之測定程序

有限元素法在成形分析方面的應用已相當普遍，但影響模擬分析結果的因素甚多，其中材料機械性質，特別是材料行爲法則與相關常數的正確引用往往是決定分析結果是否可信的關鍵點。由於超塑性材料性質的取得不易，以往求取可靠的材料性質常數均是藉助拉伸試驗，但因超塑性成形在高溫下進行，而欽合金在高溫下極易氧化，實驗中必須能抽取真空後施加保護氣體，整個實驗所需要的設備相當昂貴且不易控制。本研究從半球吹製成形的簡單實例中出發，成功地發展出一套能更迅速、經濟地獲得應力一應變率關係的量測方法。由超塑性吹製半球的實驗結果配合解析的推導來獲得材料性質常數，並將所得常數與文獻載錄的法則與常數，藉助商用有限元素軟體ABAQUS來進行半球吹製成形的模擬分析，以比較所引用之材料常數的差異。本文所提之方法的可靠性則由模凝與實驗的結果相比較而獲得驗證。

關鍵字

超塑性成形；材料行爲法則；應變率敏感度；有限元素分析模擬； ABAQUS商用軟體

並列摘要

The application of finite element methods in forming simulation have become a common practice. Many factors affect the reliability of a finite element solution. Among them, the use of an appropriate material constitutive model is usually a decisive factor that governs the reliability of the solution. Obtaining suitable material data is in general not an easy task. Conventionally, material constants are often acquired from uniaxial tension tests. However, since the superplastic forming process is always carried out at high temperature, and the Ti alloys are prone to oxidize under this condition, during the experiment, the test chamber would have to be maintained with protective gas after being vaccumed. The eintire experimental setup is not only costly but also difficult to control properly. In this paper, we begin with a simple blow forming of a hemisphere, and successfully develop a procedure to rapidly and econdomically obtain stress and strain rate relations. By incorporating measured data into analytical1y derived equations, the associated constants for a chosen material model can be determined. The pressent results together with several frequently referred material models available in the literature are implemented as user's subroutines for the commercial finite element program, ABAQUS. The reliability of the current method is examined by comparing the numerical solutions with the experiments.

並列關鍵字

superplastic forming ； material constitutive law ； strain rate sensitivity ； finite element simulation ； ABAWUS software

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Ti-6AI-超塑性行爲模式參數之測定程序

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