A modified Johnson–Cook model for tensile flow behaviors of 7050-T7451 aluminum alloy at high strain rates

Abstract:Isothermal uniaxial compressions of a Ti-6Al-4V alloy were carried out in the temperature range of 800-1050 • C and strain rate range of 0.001-1 s −1 . The effects of friction between the specimen and anvils as well as the increase in temperature caused by the high strain rate deformation were considered, and flow curves were corrected as a result. Constitutive models were discussed based on the corrected flow curves. The correlation coefficient and average absolute relative error for the strain compensated Arrhenius-type constitutive model are 0.986 and 9.168%, respectively, while the values for a modified Johnson-Cook constitutive model are 0.924 and 22.673%, respectively. Therefore, the strain compensated Arrhenius-type constitutive model has a better prediction capability than a modified Johnson-Cook constitutive model.

Section: Modified Johnson-cook Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Correction of Flow Curves and Constitutive Modelling of a Ti-6Al-4V Alloy

Dong

Zhang

et al. 2018

“…Compared with Arrhenius equation, JC constitutive equation has the characteristic of simple parameters. It is used to predict the rheological behavior of the material with little change in the flow stress after the peak stress, but the prediction effect is not ideal for the complex rheological behavior of those materials [35,47,48]. It is found that the second order polynomial can more accurately describe the relationship between flow stress and strain, rather than the original exponential expression.…”

Section: The Original Jc Model and Its Modified Equationmentioning

confidence: 99%

A Modified Johnson-Cook Model for Hot Deformation Behavior of 35CrMo Steel

Wang

Huang

Xiao

et al. 2017

Abstract:In this work, a compression experiment of 35CrMo steel is carried out over a wide range of temperatures (1123-1423 K) and strain rates (0.1-10 s −1 ) to obtain further understandings of the flow behaviors. The results show that the strain hardening effect of 35CrMo steel is stronger than that of dynamic recrystallization at low temperature and high strain rate; on the contrary, the rheological curves show typical dynamic recrystallization characteristics at high temperature and low strain rate. This indicates that the strain hardening and recrystallization behavior of 35CrMo steel is affected by temperature, strain and strain rate, and its true stress-strain curves can be observed typical work hardening and dynamic softening features. A modified Johnson-Cook (JC) model is developed to predict the flow stress of the alloy. The results of the comparison show that the predicted values of the modified JC model are in good agreement with the experimental values.

“…With EMF, the strain rate effect must be considered [26], and so the stress-strain data at various strain rates via quasi-static tests and Hopkinson bar tests are provided here. The quasi-static experiments were measured by SANS ® CMT5205 (Shenzhen, China) electronic universal testing machine at room temperature under a fixed strain rate of 10 −3 s −1 .…”

Section: Materials and Blankmentioning

confidence: 99%

Guideline for Forming Stiffened Panels by Using the Electromagnetic Forces

Tan

Zhan

Liu

2016

Self Cite

Electromagnetic forming (EMF), as a high-speed forming technology by applying the electromagnetic forces to manufacture sheet or tube metal parts, has many potential advantages, such as contact-free and resistance to buckling and springback. In this study, EMF is applied to form several panels with stiffened ribs. The distributions and variations of the electromagnetic force, the velocity and the forming height during the EMF process of the bi-directional panel with gird ribs are obtained by numerical simulations, and are analyzed via the comparison to those with the flat panel (non-stiffened) and two uni-directional panels (only with X-direction or Y-direction ribs). It is found that the electromagnetic body force loads simultaneously in the ribs and the webs, and the deformation of the panels is mainly driven by the force in the ribs. The distribution of force in the grid-rib panel can be found as the superposition of the two uni-directional stiffened panels. The velocity distribution for the grid-rib panel is primarily affected by the X-directional ribs, then the Y-directional ribs, and the variation of the velocity are influenced by the force distribution primarily and secondly the inertial effect. Mutual influence of deformation exists between the region undergoing deformation and the deformed or underformed free ends. It is useful to improve forming uniformity via a second discharge at the same position. Comparison between EMF and the brake forming with a stiffened panel shows that the former has more advantages in reducing the defects of springback and buckling.