Deep drawing

Abstract

Deep drawing: definition and fundamentals. Stresses and deformation in a deep-drawn cup. Deep drawing load and its components and their variations with punch movement. Derivation of mathematical expression for load and its comparison with Sachs relation. Formability: properties of work metal for optimal formability. Strain distribution in a forming operation determined by strain-hardening exponent, strain rate sensitivity and plastic strain ratio. Allowable maximum deformation level represented graphically as forming limit diagram. Deep drawability and its relation with plastic strain ratio. Conditions for optimal drawability. Measurement of drawability by drawing ratio using Swift cup test. Limiting draw ratio to express deformation limit in deep drawing. Effects of process variables that include drawing ratio and redrawing operations, profile radii of die and punch, punch-to-die clearance, drawing speed, friction and lubrication, restraint of metal flow, such as use of a blank holder. Effects of material parameters that include sheet thickness and anisotropy. Evaluation of formability of sheet metal using different type tests, such as Marciniak biaxial stretching test, Swift cup test, Ericksen and Olsen cup tests, Fukui conical cup test, hole expansion test and forming limit diagram using hemispherical punch method. Defects in deep-drawn components. Problems and solutions.