Low Cycle Fatigue Behavior of Ti-Alloy (II)

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Project title

Code/計畫編號

NSC90-2216-E019-007

Translated Name/計畫中文名

高性能材料之銲接與修補製程最佳化研究---子計畫III：鈦合金銲接構件之彎曲低週期疲勞(II)

Project Coordinator/計畫主持人

Shing-Hoa Wang

Funding Organization/主管機關

National Science and Technology Council

Department/Unit

Department of Mechanical and Mechatronic Engineering

Website

https://www.grb.gov.tw/search/planDetail?id=673378

Year

2001

Start date/計畫起

01-08-2001

Expected Completion/計畫迄

01-07-2002

Bugetid/研究經費

696千元

ResearchField/研究領域

材料科技

本計畫研究方向為二，其一探討三種不同微觀組織的鈦合金，於應用不同應變速率及應變振幅的情況下，其原素材及氣護鎢極電弧銲銲件對低週疲勞性質的比較，實驗結果顯示銲道溶融區硬度由高至低之順序為：Ti-64、Ti-153、CP-Ti。增加應變速率均會使CP-Ti、Ti-64和Ti-153的拉伸抗拉強度和降伏強度上升，且其伸長量會下降，銲件的趨勢與素材相同，但銲件的強度均較母材低。在疲勞試驗方面，應變速率升高會使Ti-64和Ti-153疲勞強度上升，高應變振幅呈循環應力軟化，低應變振幅則為循環應力硬化，但CP-Ti則顯示相反的趨勢，且Ti-153對應變速率的敏感性較CP-Ti和Ti-64高，CP-Ti和Ti-64銲件主要裂縫大都出現於母材區，其疲勞強度劣於原素材，Ti-153銲件裂縫位於銲道處，且其銲件疲勞強度優於.εdot.=5*10/sup -3/s/sup -1/時的素材疲勞強度，但劣於.εdot.=1*10/sup -2/s/sup -1/時素材疲勞的強度。另一方向著重於四點彎曲低週次疲勞實驗方法開發，探討雙向施加循環應變，模擬構件側向彎曲疲勞特性。 Three different titanium alloys (pure Ti, Ti-64 and Ti-153) with different microstructures and their welds were used to study the effect of strain rate and strain amplitude on the properties of low cycle fatigue. It shows that the ultimate tensile strength and the yield strength increase with increasing strain rate but the elongation decreases. Similarly, fatigue strength increases with strain rate. Alloys undergo cyclic strain hardening at the relative small strain amplitude. On the other hand, alloys undergo cyclic strain softening so that stress range decreases with increasing number of strain cycles. The ductile pure Ti and Ti-153 alloy exhibit more sensitive to strain range change than high strength Ti-64. The fatigue strength of Ti-64 welds is inferior to that of parent metal and the failure occurs at the base metal zone. However the fatigue failure of Ti-153 happens at the weld.

Keyword(s)

高性能材料
焊接
彎曲低週期疲勞
鈦合金
焊件
High performance material
Welding
Bending low cycle fatigue
Titanium alloy
Weldment

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Low Cycle Fatigue Behavior of Ti-Alloy (II)

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