Combined Loading Processes in Technological Problems

The estimation of proximity of a modelled process to monotonic or other specific combined loading cases, which helps to predict rheological model imprecisions, is an important task. This paper describes combined loading processes in terms of maintaining their unique determination — proximity to the monotonic process determined by Smirnov-Alyaev. The authors developed an algorithm of selection of a rheological model (the stress-strain curve) based on the classification of combined loading processes according to the change of deformation type and rotation angle of the directing tensor of deformation. The emphasis is put on the practical use of this algorithm.  It is shown that quasi-simple loading in the general theory of plasticity can be described naturally in this classification. A scalar parameter is proposed, which helps to evaluate the proximity of an arbitrary combined loading process to a monotonic one. Based on this parameter, the concepts of weakly non-monotonic and strongly non-monotonic processes are introduced. An example of practical use of the proximity measure is given. For torsion deformation of a round rod, the authors carried out an evaluation of possible errors that may occur when the proposed algorithm of rheological model selection is used. The results of this research can be used to predict the adequacy of numerical models for metalworking technological processes.

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