Introduction 上清充通大￥ SHEAMGRAI DUAD TONO UNTVEEETTY Assumption Basic assumptions of material in plastic theory 1)Continuity 2)Homogenous 3)Isotropy 4)No initial stress 5)No body force 6)Volume constant Institute of Forming Technology Equipment
Institute of Forming Technology & Equipment Introduction Assumption 7 Basic assumptions of material in plastic theory 1) Continuity 2) Homogenous 3) Isotropy 4) No initial stress 5) No body force 6) Volume constant
Introduction 国上海克通大米 SANCEAI JUO TO阳UY External force Forces distributed over the Gravitational force volume of a body Bulk force Inertia force External force Magnetic force Hydrostatic pressure Surface force Normal pressure Pressure exerted by Forces distributed over the one body on another surface of the body Friction force centrifugal forces thermal stress Institute of Forming Technology Equipment 8
Institute of Forming Technology & Equipment Introduction External force 8 External force Gravitational force Inertia force Magnetic force Hydrostatic pressure Pressure exerted by one body on another Bulk force Surface force Forces distributed over the volume of a body Forces distributed over the surface of the body centrifugal forces thermal stress Normal pressure Friction force
Introduction 上清充通大￥ SHEAMGRAI DUD TONO UHTVEREETTY External force N 2 H Institute of Forming Technology Equipment 9
Institute of Forming Technology & Equipment Introduction External force 9
Stress 上清充通大婆 DREANOIAI AO TONG UNIVEREITT Definition of stress Stress what's stress? Stress force per unit area.In general the force will not be uniformly distributed over any cross section of the body. lim △P =S △4-→0△A where A is the area on which the force acts. ② ② 9% (b1 a) Body inequibrium under action of external forces PP b)forces acting on parts Institute of Forming Technology Equipment 10
Institute of Forming Technology & Equipment Stress Definition of stress 10 Stress what’s stress? Stress : force per unit area. In general the force will not be uniformly distributed over any cross section of the body. where A is the area on which the force acts. a) Body in equilibrium under action of external forces P1, P2, ..., P5 ; b) forces acting on parts 0 lim A P s A
Stress 上清充通大￥ SHEAMGRAI DUD TONO UHTVEREETTY Definition of stress Stress The total stress can be resolved into two components,: > a normal stress o perpendicular to A, > a shearing stress(or shear stress)t lying in the plane mm of the area P P cos0 T=-sin0 A F A Institute of Forming Technology Equipment 11
Institute of Forming Technology & Equipment Stress Definition of stress 11 Stress The total stress can be resolved into two components,: a normal stress σ perpendicular to A, a shearing stress (or shear stress) τ lying in the plane mm of the area cos P A sin PA