Types of stresses: tensile, compressive, shear, biaxial tension compression, hydrostatic. Stress and strain are proportional to each other using. Es e= (e young"s modulus) or t g. , poisson"s ratio: u e e x z (bottom of ratio strain in direction of applied force) Deformation: metallic materials deform elastically (reversible) until strains of about . 005. Work hardening: after they yield, metals get harder to deform. Ductility: % elongation = ](lf l0) / l0] * 100, % area reduction = [(a0 af) / a0] * 100. 2 (p-load, d-diameter of steel ball: 10 mm, d-indent diameter), resilience: E ktg voltage is measured, a is the area perpendicular to the direction of the current. p. Metals: electron drift velocity (p probability, #of electrons excited (holes created)), if eg>2 ev, then p 0 (cid:222) e v d me= e. For semiconductors, as t , ne . n , but m.