【作者】 薛玉雷；

【导师】 陈明和；

【作者基本信息】 南京航空航天大学 ， 材料加工工程， 2006， 硕士

【摘要】 有限元模拟是板料成形过程中预测板料失稳的重要手段,考虑到当前通用的有限元软件都是以存在应变路径相关性缺陷的基于应变的成形极限图为失稳判据,以致在研究复杂应变路径板成形时极为不便。本文基于板成形专用有限元分析软件DYNAFORM,以国内外板料成形领域认同的具有应变路径独立性优点的成形极限应力图为判据进行了应用软件的二次开发,以期为板成形有限元分析软件提供一个新的失稳判据。本文首先分析了板料成形的屈服准则和失稳准则,然后根据极限应变到极限应力的转换关系,分别采用Hill48屈服准则、Hill79屈服准则和Hosford屈服准则,建立了用于软件开发的成形极限应力图的数学计算模型。根据以上所建立的数学计算模型,基于板成形专用有限元分析软件DYNAFORM的环境,用Visual C++开发了以成形极限应力图作为判据的应用软件。所开发的应用软件,首先读取DYNAFORM的计算结果文件D3plot,输入材料的相关参数和试验所得到的板料的极限应变,软件即可生成用作板料失稳判据分析用的成形极限应力图和零件的应力云图。本文工作实现了以成形极限应力图作为判据来分析复杂板料成形失稳情况的目标。并用所开发的应用软件成功地对板成形零件的有限元计算结果进行了分析,分析结果表明,用该软件分析板成形零件的失稳情况的结果可以满足板成形工艺分析要求,所开发的应用软件模块达到了预期目的。同时,该模块也可以移植到以LS-DYNA为求解器的其他有限元分析软件中。更多还原

【Abstract】 The finite element numerical simulation analysis is an important method to predict sheet metal instability in the sheet metal forming process. And the current general-purpose finite element codes all choose the strain-based forming limit diagram as the instability criterion, which has the limitation of correlative to the strain path. Thus it is very inconvenient to study sheet metal forming under complex strain paths. In view of the above reason, this thesis adopts the forming limit stress diagram as the instability criterion due to its independence of strain paths, which is acknowledged at home and abroad in the field of sheet metal forming, and develops the applied software for the special purpose finite element analysis code DYNAFORM in order to provide it with a new instability criterion.This thesis briefly analyzes some yield criteria and instability criteria to the sheet metal forming first. Then according to the transformation rule from ultimate strain to ultimate stress, it establishes the mathematical calculation models of the forming limit stress diagram for the software development according to Hill48、Hill79 and Hosford yield criterion irrespectively.According to the former mathematical calculation models, the applied software, which uses the forming limit stress diagram as its instability criterion, is developed based on the sheet metal forming finite element code DYNAFORM using Visual C++. First read in the calculation result file i.e. D3plot, then input the correlative material parameters and ultimate strain from experiments, and the developed software will produce the forming limit stress diagram used as sheet metal instability criterion and the stress contour of the part. The goal of analyzing the instability in complex sheet metal forming is reached using the forming limit stress diagram as criterion in this thesis. Some different sheet metal forming parts are analyzed with the developed software, whose results show that the developed software is satisfying for technological analysis of sheet metal forming and the applied module attains the anticipated goal. At the same time, the module is applicable to other FEM codes that use LS-DYNA as solver.更多还原