Research on creation and application of material models in the rolling process of medium and heavy plate leveler
Mechanical properties model of moderate/high temperature material affects leveling parameters setting. This article establishes the model as well as self-studying in rolling process and simplex optimizes the formulation of material model's deformation resistance. The model is established through this process which has a higher application in the actual production.
Material Model Describing Cyclic Elastic‐Plastic Deformation of Roller Levelling and Straightening Processes
The presented material model describes the elastic‐plastic stress‐strain course of cyclic tension‐compression deformation with variable amplitudes. The result is a hysteresis curve. Each hysteresis curve consists at maximum of three parts. Part I starts on a linear course originating from elastic strain or elastic recovery and ends at a defined point N. When the strain runs past this point, part II then follows as a non‐linear function where the superposition of a logarithmic function with a parabola proved to be in good coincidence with the real material behaviour. When the strain reaches a point T, linear hardening begins as part III. For the application of the model in practice, a file of data from special tests with cyclic tension‐compression deformations is necessary. The material model can be applied as a subsystem in a roller straightening process model. It has been successfully used in practice. The detrimental residual stresses were significantly reduced as well as the straightness of the rails was improved.
Modeling the Bauschinger effect for sheet metals, part I: theory
Abstract It is essential to model the Bauschinger effect correctly for sheet metal forming process simulation and subsequent springback prediction when material points are subjected to cyclic loading conditions. The combined nonlinear hardening model for time independent cyclic plasticity, proposed by Chaboche and co-workers, is examined and a simple modification is suggested for the isotropic part of the hardening rule to utilize the conventional tensile test data directly. This modification is useful for the materials whose reverse loading curves saturate to the monotonic loading curve. In addition, an anisotropic nonlinear kinematic hardening model (ANK model) is proposed in an attempt to represent the Bauschinger effect more realistically. Possible offset in flow stress is modeled by treating the back stress evolution during reverse loading differently from the initial loading. This strategy coupled with the modified isotropic hardening rule seems to provide a way to model the Bauschinger effect consistently over multiple cycles. Two types of auto-body alloys are examined in this paper. Associated material parameters are determined by employing available tension-compression test data and multi-cycle bend test data. A developed finite element formulation is applied to analyze simple validation type of problems. The cyclic stress–strain curves generated from the proposed ANK model match remarkably well with measured data.