Calibration of a modified Johnson-Cook model using the Virtual Fields Method and a heterogeneous thermo-mechanical tensile test

On the use of the Gleeble® test as a heterogeneous test: sensitivity analysis on temperature, strain and strain rate

“…Variations of temperature in the transversal direction (y direction) are not measured. However, according to the literature, for specimens of such small dimensions, those variations are usually not significant in quasi-static processes [4,9].…”

“…However, the heating by Joule effect and the heat loss that occurs due to the water cooling of the grips holding the specimen during the tensile tests may become IOP Publishing doi:10.1088/1757-899X/1238/1/012058 2 a limitation due to the generation of temperature gradients and non-homogeneous deformation in the specimen [4,10,5,6,7]. At the same time, even performing such tests at constant quasi-static applied strain rates, spatial variations on the strain rate along the specimen are also experimentally observed [8,9]. This means that the material properties characterisation may be affected as each part of the material deforms differently due to the variation of both temperature and strain rate dependent flow properties.…”

“…A number of works in the literature have reported the experimental flow stress sensitivity of metal alloys to both temperature and strain rate. Typically, for metallic materials such as aluminum alloys [10], magnesium alloys [11], boron steels [12,13,6] and dual-phase steels [9] a negative sensitivity to temperature and positive sensitivity to strain rate has been reported. However, the reported flow stress sensitivity of titanium alloys to temperature and strain rate does not follow the "traditional" behaviour due to the effect of PLC bands [1,14,7].…”

“…Considering the flow stress sensitivity to such variables may, however, not be enough to validate the numerical prediction of Gleeble ® tests. The heterogeneous spatial distribution of both temperature and strain rate may need to be taken into account [8,9]. Nonetheless, investigations measuring and quantifying the influence induced by both temperature and strain rate heterogeneities in the testing procedures and in their numerical modelling are still lacking.…”

Integrated Thermomechanical Characterization of Metals Using the Virtual Fields Method

“…In recent years, remarkable advances were obtained in plasticity, where, for instance, the Virtual Fields Method (VFM) [2,3] was used to identify advanced anisotropic plasticity models [4,5]. The application of VFM to thermomechanical models, however, has not been investigated yet and only very recently a work was published on this topic [6].…”