Murillo-Marrodán Alberto, García Eduardo, Barco Jon, Cortés Fernando
Department of Mechanics, Design and Industrial Management, University of Deusto, Avda Universidades 24, 48007 Bilbao, Spain.
R&D Department, Tubos Reunidos Industrial, Barrio Sagarribai 2, 01470 Amurrio, Spain.
Materials (Basel). 2020 Sep 25;13(19):4289. doi: 10.3390/ma13194289.
In the numerical simulation of hot forming processes, the correct description of material flow stress is very important for the accuracy of the results. For complex manufacturing processes, such as the rotary tube piercing (RTP), constitutive laws based on both power and exponential mathematical expressions are commonly used due to its inherent simplicity, despite the limitations that this approach involves, namely, the use of accumulated strain as a state parameter. In this paper, a constitutive model of the P91 steel derived from the evolution of dislocation density with strain, which takes into account the mechanisms of dynamic recovery (DRV) and dynamic recrystallization (DRX), is proposed for the finite element (FE) analysis of the RTP process. The material model is developed in an incremental manner to allow its implementation in the FE code FORGE. The success of this implementation is confirmed by the good correlation between results of the simulation and experimental measurements of the manufactured tube (elongation, twist angle, mean wall thickness and eccentricity). In addition, this incremental model allows addressing how the restoring mechanisms of DRV and DRV occur during the RTP process. The analysis puts into evidence that DRV and DRX prevail over each other cyclically, following an alternating sequence during the material processing, due mainly to the effect of the strain rate on the material.
在热成型过程的数值模拟中，材料流动应力的正确描述对于结果的准确性非常重要。对于复杂的制造工艺，如斜轧穿孔（RTP），基于幂函数和指数数学表达式的本构定律由于其固有的简单性而被普遍使用，尽管这种方法存在局限性，即使用累积应变作为状态参数。本文提出了一种基于位错密度随应变演化的P91钢本构模型，该模型考虑了动态回复（DRV）和动态再结晶（DRX）机制，用于RTP过程的有限元（FE）分析。材料模型以增量方式开发，以便在有限元代码FORGE中实现。模拟结果与制造管材的实验测量值（伸长率、扭转角、平均壁厚和偏心度）之间的良好相关性证实了这种实现的成功。此外，这种增量模型允许研究在RTP过程中DRV和DRX的恢复机制是如何发生的。分析表明，由于应变率对材料的影响，在材料加工过程中，DRV和DRX主要遵循交替序列周期性地相互占主导地位。
