Improvement of Torsional Fatigue in Ni-Cr-Mo Armored Vehicle Torsion Bar

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Project title

Code/計畫編號

NSC93-2622-E019-001-CC3

Translated Name/計畫中文名

Ni-Cr-Mo鋼300M扭力桿扭轉疲勞之改善

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=1032854

Year

2004

Start date/計畫起

01-05-2004

Expected Completion/計畫迄

01-04-2005

Bugetid/研究經費

405千元

ResearchField/研究領域

材料科技

本研究乃對 300M 機械用鋼作一系列機械性質分析，探討引發扭轉疲勞破裂的原因，期能改善 300M 的扭轉疲勞壽命。結果顯示，拉伸試桿在表面經珠擊後較未珠擊的降伏強度會有明顯的下降，最大抗拉強度略增，延伸率則增加。拉伸破裂面，接近表面處的裂紋起始點為淺窩穴的延性破裂，往棒心處則為大小不一窩穴延性破裂，最後破斷處為窩穴孔徑均勻的 dimples。未珠擊與不同珠擊程度的試桿表面硬度，並無明顯的改變；不同回火溫度下，T2 的表面硬度高於 T1。素材高速率應變衝擊下，試件高度無明顯的改變，表面也呈光滑面；在應變速率 4000 s-1下，應變硬化僅有些微的增加。撞擊後，肥粒鐵的含量減少。扭力疲勞壽命隨著珠擊時間增長而增加。The purpose of this project is to study and improve the torsion fatigue life of 300M steel. The heat treated materials after shot peening shows the yield strength decreases with increasing shot peening time, but the ductility and the ultimate tensile strength increase. The fracture surface appears as ductile feature, the crack initiation site on the surface is characterized by a very shallow dimples which mirrors the grain size. The surface hardness of shot peened torsion fatigue bar exhibits a little higher hardness for the bar tempered at T2 than for that tempered at T1. The hardness value is independent of the shot peening time. The torsion fatigue life has been improved by the longer shot peening time. In the mean time, the normalized 300M has a better resistance to impact deformation.

Keyword(s)

300M
扭轉疲勞
珠擊
300M
torsion fatigue
shot peening

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Improvement of Torsional Fatigue in Ni-Cr-Mo Armored Vehicle Torsion Bar

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