Introduction of dislocation 上清充通大学 SANCEAI JUO TO阳UY Theoretical strengths of perfect crystal The shear modulus of metals is in the range 20-150 GPa G The theoretical shear stress will be in 2元 the range 3-30 GPa Actual shear stress is 0.5-10 MPa (experimentally determined) I.e.(Shear stress)theoretical>100x(Shear stress)experimental DISLOCATIONS Dislocations severely weaken the crystal Institute of Forming Technology Equipment 61Introduction of dislocation Institute of Forming Technology & Equipment 6 Theoretical strengths of perfect crystal 2 m G    • The shear modulus of metals is in the range 20 – 150 GPa DISLOCATIONS • Actual shear stress is 0.5 – 10 MPa (experimentally determined) • I.e. (Shear stress)theoretical > 100  (Shear stress)experimental !!!! Dislocations severely weaken the crystal • The theoretical shear stress will be in the range 3 – 30 GPa