l. Frank-Read mechanism or F-R source 1. F-R mechanism: L- shaped dislocation 2. F-R source d =2T sm2 cbdl-tbode T aGb aGb T=tbp tb Tb aGb When T≤ dislocation is in quasi-static equilibrium When t> eGb dislocation will spontaneously slip◆ Ⅲ.Frank-Read mechanism or F-R source. 1. F-R mechanism: L- shaped dislocation. 2. F-R source.              G b b G b b T T b f r T b l b  =  = = = = = = 2 d d 2 d 2 sin When dislocation is in quasi-static equilibrium When dislocation will spontaneously slip ) 2 ( L Gb   ) 2 ( L Gb  