Computer simulation of fatigue crack growth

• Main Authors: Huang Yu-Qing, 黃郁青
• Other Authors: Chiang Chun-Ron
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/96965593571277243920

碩士 === 國立清華大學 === 動力機械工程學系 === 87 === Fracture mechanics is the basic theorem , especially for the question of fatigue crack propagation .In fracture mechanics, Stress intensity factor is proof to be a good parameter which can be a good index for the stress and strain of the crack tip. Therefore , stress intensity factor is the basic fundamental for the research of fatigue crack propagation .In the same material,if two cracks have the same length ,they will have the same stress intensity factor. so the two crack will have the same stress in the tip and will have the same rate of fatigue crack growth. As mention above, there will be one relation between fatigue crack growth rate and stress intensity factor. In the early 1960s, Paris, et at. Demonstrated that fracture mechanics is a useful tool for characterizing crack growth by fatigue. Since that time, the application of fracture mechanics to fatigue problems have become almost routine. Because the relation between stress intensity factor ,K,and fatigue crack growth,da,is actually a distribution function which distribute in probable range. Dr.Chiang[2] use the method of statistic to calculate the relation between the expect value of K and da. From 1961 far as,the direction of fatigue crack tip propagation , for convenient , is solved by Mode I crack, but in actually, crack tip will propagation if different direction. The paper will actually describe the propagation of fatigue crack. Therefore, several discrete direction is supposed to describe such condition. Suppose the probability of crack propagation is in proportion to its axial stress. And the method of choose the direction is done by Monte-Carlo method . Once the direction is chosen,the next step is to calculate the propagation length in this direction. This paper use equation (3-7) in this paper to calculate this value.Therefore, we can describe the propagation process of fatigue crack from its initial step to final step from computer simulation.