金属变形滞后回弹的本构模型UMAT二次开发及有限元分析

发布时间：2018-03-30 08:32

本文选题：滞后回弹　切入点：黏弹性　出处：《北京理工大学》2015年硕士论文

【摘要】：回弹是薄板冲压成形和管材弯曲成形过程中最难控制的缺陷。随着现代化工业技术的不断发展，高强板大量应用于汽车车身制造，管材弯曲加工技术也提出了更高要求，使回弹问题日益突出。长期以来，研究人员对回弹问题的研究局限于卸载后工件因宏观弹性应力释放导致的瞬时回弹，，忽略了工件形状随时间变化的滞后回弹现象。滞后回弹作为一个尚未被认知的现象，已引起国际塑性领域的关注。从目前研究看来，滞后回弹现象主要存在于汽车用高强板和航空航天用不锈钢管1Cr18Ni9Ti的弯曲变成形回弹中。本文以金属板材和管材弯曲成形回弹问题为背景，针对其滞后回弹行为，采用实验研究、理论建模以及数值分析相结合的手段展开了深入研究，主要工作包括以下几个方面：（1）根据各向同性空间的Wiechert机械模型假设和相关黏弹性理论，建立了金属变形滞后回弹的本构模型，基于有限元方法对本构模型进行离散化，获得了三维本构模型的应力-时间增量形式和能量更新形式，采用Fortran语言编制程序，在ABAQUS有限元软件中实现了本构模型的UMAT二次开发；（2）进行拉伸实验和不同应变水平下的松弛，获得了汽车用铝合金板材AC170PX、航空航天用不锈钢管1Cr18Ni9Ti的力学性能参数和黏弹性参数，为有限元模拟提供必需的材料常数；（3）针对实际AC170PX板材三点弯曲实验和1Cr18Ni9Ti管材回转牵引弯曲实验，建立了与之条件相符合的有限元模型进行有限元模拟，并在滞后回弹模拟中调用所编写的UMAT子程序进行数值计算，对比模拟结果和实验结果，验证了所建本构模型的准确性和可靠性，总结了板材、管材弯曲滞后回弹规律；（4）结合理论板材弯曲理论和有限元模拟结果，从残余应力的角度解释了板材弯曲滞后回弹现象的诱因。通过本文研究，建立了金属弯曲滞后回弹的本构模型及数值计算方法，探讨了金属变形滞后回弹规律及起因，为金属变形滞后回弹现象研究提供了有效手段。
[Abstract]:Springback is a sheet metal stamping and bending defect is the most difficult in the process of forming control. With the development of modern industrial technology, high-strength steel is widely applied in automobile body manufacturing, pipe bending processing technology also put forward higher requirements, the springback problem becomes increasingly prominent. For a long time, the research on Springback problem researchers confined to uninstall after the workpiece due to macroscopic elastic stress release caused by ignoring the instantaneous resilience, the workpiece shape changes with time lag rebound phenomenon.
As a rebound lag has not been a cognitive phenomenon, has attracted international attention in the field of plastic. It seems from the current study, lag rebound phenomenon mainly exists in the car with high strength into bending plate and aerospace 1Cr18Ni9Ti stainless steel pipe shape. The springback of sheet metal bending and springback problems as the background, according to the experimental study on the hysteretic rebound behavior, theoretical modeling and numerical analysis method of combining in-depth study, the main work includes the following aspects:
(1) under the assumption that the Wiechert mechanical model of isotropic space and viscoelastic theory, has established the metal deformation hysteresis springback constitutive model, finite element method based on the constitutive model of discrete, three-dimensional constitutive model of stress time and energy increment update form obtained by Fortran program in the ABAQUS finite element software, the constitutive model of UMAT to develop two times;
(2) relaxation and tensile experiments under different strain levels, obtained by AC170PX Aluminum Alloy 1Cr18Ni9Ti tube with stainless steel sheets for automotive, aerospace mechanical properties and viscoelastic parameters, provides the material constants required for finite element simulation;
(3) according to the actual AC170PX plate three point bending test and 1Cr18Ni9Ti rotary drawing tube bending experiments, the finite element model is established in accordance with the conditions of finite element simulation, numerical calculation and call a lag in the springback simulation written in the UMAT subroutine, comparing the simulation results and experimental results verified the constitutive the accuracy and reliability of the model, summed up the plate, tube bending springback lag;
(4) according to the theory of plate bending theory and finite element simulation results, the residual stress explained cause sheet bending springback lag.
Through this research, has established the metal bending hysteresis springback constitutive model and numerical calculation method of metal deformation hysteresis springback and causes, provides an effective method for springback research lags behind the metal to deform.

【学位授予单位】：北京理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG386

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