Analysis of Material Flow in Plane-Strain Compression
The material flow in plane-strain compression depends strongly on friction. For test evaluation, the friction coefficient should be known accurately. In this paper the conventional methods to determine friction coefficients are discussed. A new method is proposed whereby the friction conditions can be evaluated by applying compression specimens with an incorporated hole. The hole dimensions vary, depending on the friction coefficient. The variation of the hole contour is determined by the lateral and longitudinal material flow. The total longitudinal elongation of the specimen and the lateral spread in the compressed area involve additional information about the friction conditions. The new approach provides a means of evaluating and verifying the friction coefficient for the actual test rather than relying on data from literature. Theoretical, experimental and results of finite element simulations are presented. Finally, a concept is introduced to determine flow curves and investigate volume and surface effects of ultrasonic vibrations superimposed to planestrain compression.
Joachim SCHÖCK, Bernd KRÖPLIN, Klaus PÖHLANDT
metal forming, flow curve, friction, ring compression, ultrasonic vibrations.