文档介绍：材料科学基础 Fundamental of Materials Lesson twenty Lesson twenty § The Stress Around a Dislocation ?Ⅰ. Screw dislocation: Displacement: Strain: )(22 00 1x y tg bbuuu zyx ????????0d d0d d0d d??????z uy ux u zz yy xx??? 0)( 12????????x uy u yx xy??)(2 z 22 zyx yb ux u x xz????????????)(2 z 22 zyx xb uy u y yz??????????? Stresses: 0 z?????? yx)(2 )(2 0 22 z22 zyx x Gb yx y Gb y x xy????????????Ⅱ.Edge dislocation 222 22)( )3()1(2yx yxy Gb x???????? 222 22)( )()1(2yx yxy Gb y???????)( zyx??????0)( )()1(2 zz222 22?????? yx xyyx yxx Gb????? if y =0 , 0 z?????? yxr Gb x Gb xy)1(2)1(2????????? For either edge or screw dislocation shear stress on slip plane along . ??????????n dislocatio screw 2 n dislocatio edge )1(2 s??????G G r b ??§ Elastic Energy and Line Tension of Dislocation ?Ⅰ. W tot = W core + W elast = W misfit + W el P?? 1. W e e of an edge dislocation. of an edge dislocation. Model: see figure. consider an area element x→ x+ d x which displaced from b'→b '+d b '. then l Gb r R Glb bxx b lG bxlW Rr xy e2 2 b0) ln( )1(4 dd 1)1(2 d)d( o???????????????????? e of a screw dislocation: ) ln( 4 2e?r R Glb W?? 3. W e e of a mixed dislocation of a mixed dislocation : : l? cos b ? sin bb ??) ln( ]4 ) cos ()1(4 ) sin ([ 2 2 mix?r RlbGlbGW?????????Ⅱ.Line tension 2ed d tension line Gb l W T???Examples and Discussions