CONTROL AND CHARACTERIZATION OF MECHANICAL-PROPERTIES UNDER COLD-ROLLING CONDITIONS

Almost all of the models applied in the dimensional control systems? c ontrol of the mechanical properties and optimisation of cold rolling, rely extensively an embedded models of materials behaviour under cold rolling conditions. Prediction of flow stress under forming conditions , which is the most important parameter in this connection, is commonl y based on an explicit formulation of the flow stress model. The flow stress is in these models (simplified analytical models or ''flow curv es'') expressed as a function of the influencing parameters strain, st rain-rate, temperature and/or as a function of the governing parameter s dislocation density and microstructure. Incrementally-formulated flo w-stress models (strain-hardening models) allow better prediction of t he flow stress regarding the influence of the strain and temperature h istory. In such rolling processes, when flow competition is possible, i.e., when spread occurs during rolling as in, e.g., flat wire rolling , the anisotropy of the behaviour may play a significant role and has to be accounted for in the constitutive models. In cold processing as in cold pilger rolling of precision tubes and cold roller straightenin g of strip, the complex stress reversal patterns significantly influen ce the behaviour and the cyclic deformation mode must be regarded in t he constitutive models. This paper presents modelling and testing of m aterial behaviour pertinent to cold rolling of flat and long products undertaken in recent years at the Department of Metal Forming, KTH. So me examples of applications of the models, and also expected future de mands on testing of materials for cold rolling, are given. (C) Munksga ard, 1997.