• 한국자동차공학회논문집
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• 제16권5호
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• pp.1-7
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• 2008

A study of new materials that are light-weight, high in strength has become vital to the machinery of auto industries. But then, there are a lot of problems with developing such materials that require expensive tools, and a great deal of time and effort. Therefore, the improvement of fatigue strength and fatigue life are mainly focused on by adopting residual stress. And Influence of corrosive condition for corrosion fatigue crack was investigated, after immersing in 3.5%NaCl, $10%HNO_3$+3.5%HF, $6%FeCl_3$. The immersion period was performed for 365days. The compressive residual stress was imposed on the surface according to each shot velocity based on shot peening, which is the method of improving fatigue life and strength. Fatigue life shows more improvement in the shot peened material than in the un peened material in corrosion conditions. The threshold stress intensity factor range was decreased in corrosion environments over ambient. Compressive residual stress of surface on the Shot-peen processed operate resistance force of fatigue crack propagation. The fatigue crack growth rate of the Shot-peened material was lower than that of the un peened material. Also m, fatigue crack growth exponent and number of cycle of the shot peened material was higher than that of the un peened material. That is concluded from effect of da/dN.

• 대한기계학회논문집A
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• 제41권3호
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• pp.193-198
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• 2017

Alloy 617은 초고온가스로(VHTR)의 중간열교환기(IHX)의 유력한 후보 재료 중의 하나이다. $850^{\circ}C$의 고온에서 Alloy 617 용접재의 저사이클 피로 거동을 고찰하기 위하여, 완전 양진 변형률제어 피로시험이 0.6에서 1.5%의 전변형률범위에서 수행되었다. 용접재 시험편은 V-그루브 형상의 가스텅그스텐아크 용접한 용접 패드로부터 가공되었다. 피로수명은 전변형률범위가 증가할수록 감소하였다. 모든 실험조건에서 Alloy 617 용접재 시험편의 반복 응력 반응 거동은 초기 수 사이클에서 반복 변형률 경화현상을 나타내었다. 또한 모든 피로 균열의 발생과 전파는 입내파괴의 파손 모드를 보였다.