A wedge plastometer for hot multistage compression testing

Abstract

In many hot-forming processes, the workpiece is deformed in a number of stages, with a short time interval between each stages during which some recovery or recrystallization occurs and the subsequent yield-stress level is reduced. Multistage hot-forming processes include hammer forging, rotary forging, tandem rolling and ring rolling. For the prediction of forming forces under such conditions, appropriate yield data are needed. Laboratory testing equipment is not generally capable of accurately straining test specimens in increments at suitably high strain-rate levels and existing cam plastometers are not designed for multistage straining. A description is given of a plastometer actuated by a linear cam, the position of which is controlled hydraulically through timer circuits, enabling compression tests to be made with control strain rate, strain increment and dwell period. The strining accuracy of the machine is discussed and some preliminary tests on lead and low-carbon steel are described.