Abstract
AbstractA solution for the transient heat transfer during plane strain upsetting of a viscoplastic strip has been developed using a Lagrangian coordinate system and the Green's function available in the literature. A general approximate solution for stress and velocity found elsewhere has been used. In contrast to conventional viscoplastic models adopted in theoretical analyses of metal forming processes, the model considered in the present paper includes a saturation stress. This model used in the conjunction with the maximum friction law predicts the localization of plastic deformation in the vicinity of the friction surface. In turn, localized plastic deformation and temperature are responsible for the generation of a very narrow layer with drastically modified microstructure near the friction surface. The appearance of such layers is reported in numerous experimental works.
Highlights
Numerous experimental studies demonstrate that a very narrow layer with drastically modified microstructure is generated in the vicinity of frictional interfaces in machining and deformation processes
The interface between tool and workpiece in metal forming processes is crucial to both friction and heat transfer.[26]
A conventional method for increasing the accuracy of finite element predictions of the temperature field near friction interfaces is to use a fine mesh near the interface
Summary
Numerous experimental studies demonstrate that a very narrow layer with drastically modified microstructure is generated in the vicinity of frictional interfaces in machining and deformation processes (see [1,2,3,4] among many others). Plastic deformation is one of the main contributory mechanisms responsible for the generation of such layers.[5] There are several rigid plastic models that predict highly localized plastic deformation near maximum friction surfaces showing qualitative agreement with the aforementioned experimental results.[6,7,8,9] these models do not account for heat generation whereas temperature is another important contributory mechanism responsible for the generation of the narrow layer with drastically modified microstructure near frictional interfaces.[5] The capacity of the models[6,7,8,9] to predict highly localized plastic deformation comes at a cost: the solutions are singular (some components of the strain rate tensor approach infinity near the friction surface) A property of conventional viscoplastic models that are usually adopted in theoretical analyses of metal forming processes is that the equivalent stress approaches infinity when the equivalent strain rate approaches infinity (see, for example, [12]) In this case it is always possible to find a solution satisfying the sticking boundary condition at friction surfaces.[13] The behavior of.
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