85. 8 The Stress Around a Dislocation I. Screw dis location D i sp l acement l=0un,=0 b 2丌2兀 d Strain:a =0 0 a dx§5.8 The Stress Around a Dislocation ◆ Ⅰ. Screw dislocation: Displacement: Strain: ( ) 2 2 0 0 1 x y t g b b u u u x y z − = = = =    0 d d 0 d d 0 d d = = = = = = z u y u x u z z y y x x   