疲勞與斷裂 第五章 斷裂失效與斷裂控制設(shè)計(1)ppt課件

1、中心裂紋中心裂紋s sWBs s邊裂紋邊裂紋s ss s外表裂紋外表裂紋2cts ss s裂紋尺寸裂紋尺寸運用時間運用時間a) a) 裂紋擴展曲線裂紋擴展曲線剩余強度剩余強度裂紋尺寸裂紋尺寸b) b) 剩余強度曲線剩余強度曲線裂紋的裂紋的三種根三種根本受載本受載方式：方式：s szxy yz zxy yz zs ss sx xy y2adxdyrs ss sx xy y2adxdyrs s s sq qyar= =+ +221cos q qq q232sin sint ts sq qq qq qxyar= =22232sin cos coss s s sq qxar=-221cos q qq

2、q232sin sin(5-1)(5-1)s sp pf f q qijijKr= =12( )Ka1= =s sp ps ss sx xy y2adxdyrKa f a W1= =s s p p( ,.)作用作用( ( 、a)a)越大，抗力越大，抗力(K1C )(K1C )越低，越能夠斷裂越低，越能夠斷裂。s sp pf f q qijijKr= =12( )Ka1= =s sp p作用作用 K=f (s, a, .) 由力學(xué)分析得到；由力學(xué)分析得到； 彈性力學(xué)方法，有限元法，手冊等。彈性力學(xué)方法，有限元法，手冊等。L=4WWP三點彎曲三點彎曲B=W/2)( 7 .38)( 6 .37)(

3、8 .21)( 6 . 4)( 9 . 22/92/72/52/32/ 12/3WaWaWaWaWaBWPLK+-+-=)(639)(1017)( 7 .655)( 5 .185)( 6 .292/92/72/52/32/ 12/ 1WaWaWaWaWaBWPK+-+-=2孔f 0.25WPPW1.25W1.2W0.55W。PP實驗機實驗機引伸計輸出引伸計輸出V VPmaxP0VP500P5PmaxPmaxBWKBKc)(57.14)(18.14)(20. 8)(735. 1090. 1)(432WaWaWaWaWaf+ +- -+ +- -= =)(2321WafaBWPLKp p= = 將

4、將a/W=32/60=0.533， PQ= 56kN 代入，算得：代入，算得： KQ=90.5 MPa)(1x xp ps sFaK = =)2/sec()(pxpxx x= =F)(1x xp ps sFaK = =KKK + + = =PPKK WPP05. 1(6Pe2/Wap p= Wa/= =x x43239.3072.2155.10231. 012. 1)(x xx xx xx xx x+ +- -+ +- -= =F);(x xp ps sFa= =K tWaP/37. 1p p= =K )0.025/01. 03. 637. 1 (005. 014. 3025. 060)/3. 637. 1 (1+ += =+ += =WeaWKPccp ps sp pf f q qijijKr= =12( )Ka1= =s sp ps ss sx xy y2adxdyrs s s sq qyar= =+ +221cos q qq q232sin sint ts sq qq qq qxyar= =22232sin cos coss