On the identification of kinematic hardening material parameters for accurate springback predictions

Abstract

An experimental method that frequently has been used for the determination of material hardening parameters is the three-point bending test. The advantage of this test is that it is simple to perform, and standard test equipments can be used. The disadvantage is that the material parameters have to be determined by some kind of inverse approach. The test has then been simulated by means of the Finite Element Method, and the material parameters have been determined by finding a best fit to the experimental results by means of a Response Surface Methodology. An alternative method is the tensile/compression test of a sheet strip. In practice such a test is very difficult to perform, due to the tendency of the strip to buckle in compression. In spite of these difficulties some successful attempts to perform cyclic tension/compression tests have been reported in the literature. However, a few writers have reported that there are substantial differences between hardening parameters determined from bending tests and those determined from tensile/compression tests. The purpose of the present study is to try to understand the background of these differences, to find out the influence on predicted springback, and to determine which of the two methodologies for hardening parameter identification is the most suitable one.

Using the Hollomon Model to Predict Strain-Hardening in Metals

“…This is because, one of the most common mechanical stress-strain tests is performed in tension [21]. The stress-strain data are obtained directly during the course of the test and an inverse test is unnecessary, unlike in the bending test [22]. The tensile test can be used to ascertain several mechanical properties of materials that are important in design.…”

Comparison of the hardening behaviour of different steel families: From mild and stainless steel to advanced high strength steels

“…The tension-compression test proved to be an appropriate experimental test to characterize the Bauschinger Effect and the identification of the material parameters of the kinematic hardening laws [32]. The test provides suitable stress-strain curves under small strain ranges; however the maximum plastic strain achieved with this method is limited.…”

“…This is because the stress-strain data are obtained directly during the course of the test and an inverse method is not necessary, as occurs in pure and three point bending test [32]. This test only achieves a maximum deformation of approximately 3%; however it could be appropriate to characterize low deformation processes such as the roll levelling process, in which the maximum material deformation is usually lower than 2%.…”

Analytical Model of a Multi-Step Straightening Process for Linear Guideways Considering Neutral Axis Deviation

“…The theoretical modelling approaches of the cold-straightening process include the following three aspects: bending models based on straightening curvature, bending models based on load and deflection, and analytical models based on elasto-plastic theory [5][6][7]. The theories of predictive models are comprehensive and relatively mature, but the complex interaction between different procedures has not been considered in multi-step straightening processes, which limits the improvement of straightening accuracy.…”