工程失效案例分析報告-展示頁
2025-04-25 22:57本頁面
【正文】 （２）、應(yīng)力集中的影響應(yīng)力集中越嚴重，就越易發(fā)生脆性破壞，原因是應(yīng)力集中是產(chǎn)生三向拉應(yīng)力的根源，這三向拉應(yīng)力來束縛著鋼材的塑性變形，而增加鋼材的脆性，極易造成高峰應(yīng)力處應(yīng)力集中使鋼材脆性增強。線彈件斷裂力學(xué)指出，當(dāng)一塊板處于甲面應(yīng)變狀態(tài)下如果應(yīng)力強度因子Ｋ１＝απaσ≥Ｋic裂紋將迅速擴展而造成斷裂。河南工業(yè)大學(xué)機電工程學(xué)院 工程失效案例分析報告一、疲勞計算 Solution:1. We can get three conclusions from the picture shown in Figure .a. the flaw shape is buried circular plate crackb. initial flaw size is milimeter .c. critical dimension of fatigue crack is about 1 milimeter .So a0= ac=1mma/2c= a/h= Look up the curves of Me shown in appendix D Me=As Q=(σ/σs)2 Calculate Q=2. Estimate the remaining life of the part As da/dN=1011 (Δk)4=1011[Me*σ*(*a/Q)1/2]4 The derivation of expression (1) is Nc is da/1011[Me*σ*(*a/Q)1/2]4Known:The maximum stress isσ, σ=300Mpa .Substitute Mc ,a0 ,ac ,and Q into expression (2) Integrate Nc.Nc=49 weeks.As the initiation stage of the flaw is 50 percent of the life of part , the total life time of the part is 49*2=98 .The above results are some larger ,because we uncondering stress frequency and other factors ,and it will be understood in Figure Obviously , σe is larger than 300 Mpa ,because
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