The simultaneous hot/cold forging is an innovative production process, taking advantage of the high accuracy for cold forming and low forces for hot forming. However, the choice of a suitable material model for such a large temperature range is a difficult issue and insufficiently regarded. Hence, the aim of this contribution is a critical review and assessment of the prediction capability and accuracy of three already existing thermo-viscoplasticity models. Therefore, the simulation results of the Bammann, Chiesa and Johnson (BCJ) model, the Evolving Microstructural M odel of I nelasticity (EMMI) and a recently proposed user defined constitutive model by Bröcker and Matzenmiller, based on an enhanced concept of rheological elements, are compared to test data considering a large range from room temperature up to approximately 1400 K (1127 ^∘C). All three material models may represent the thermo-viscoplastic characteristics of metals, whereby each investigated material model comprises different approaches for the temperature dependency of the initial yield stress, nonlinear isotropic hardening, and strain rate sensitivity. All material parameters are identified with the test data of the low alloy steel 50CrV4/51CrV4, the case hardening steel 16MnCr5, the low carbon steel C15 and the aluminium alloy AlMgSi1 by using the commercial optimisation software LS-OPT. The prediction capability and accuracy of each model is evaluated on the basis of the mean squared error by means of a comparsion of real and predicted stress-strain curves for the four different metals. Finally, an industrial oriented hot/cold forging process for the production of a gear shaft made of the low alloy steel 51CrV4 is simulated with LS-DYNA using the three material models and, subsequently, their performance is discussed. As achievement of this model assessment, suitable as well as inappropriate temperature dependent approaches are identified for this large temperature range providing new insights into suitable material models for the analysis of a simultaneous hot/cold forging process.

热/冷同时锻造是一种创新的生产工艺，利用了冷成形的高精度和热成形的低力。然而，对于如此大的温度范围选择合适的材料模型是一个难题，并且没有得到充分考虑。因此，该贡献的目的是对三个已经存在的热粘塑性模型的预测能力和准确性进行严格的审查和评估。因此，进行模拟的结果乙阿曼，Ç hiesa和Ĵ ohnson（BCJ）模型中，ê volving中号icrostructural中号的Odel等我弹性（EMMI）和最近由Bröcker和Matzenmiller提出的用户定义的本构模型，基于流变元素的增强概念，考虑了从室温到大约1400 K（^1127∘C）。所有这三种材料模型都可以代表金属的热粘塑性特征，因此，每种研究的材料模型都包含不同的方法来解决初始屈服应力，非线性各向同性硬化和应变率敏感性的温度依赖性。使用商业优化软件LS-OPT，通过低合金钢50CrV4 / 51CrV4，表面硬化钢16MnCr5，低碳钢C15和铝合金AlMgSi1的测试数据确定所有材料参数。通过比较四种不同金属的实际和预测应力-应变曲线，在均方误差的基础上评估每个模型的预测能力和准确性。最后，使用这三种材料模型，使用LS-DYNA对以低合金钢51CrV4制成的齿轮轴进行生产的工业取向热/冷锻工艺进行了仿真，然后讨论了它们的性能。随着该模型评估的完成，在此大温度范围内确定了合适的方法以及与温度有关的方法，这些方法为对同时进行热/冷锻工艺分析的合适材料模型提供了新的见解。