【作者】 曹源源；

【导师】 宋满仓； 吕晶；

【作者基本信息】 大连理工大学 ， 机械工程， 2012， 硕士

【摘要】 先进高强度钢板(Advanced High Strength Steels sheet, AHSSs)因汽车工业的高速发展而得到广泛使用。然而因其特有的性质(高强度、低塑性),在利用板料冲压成形技术生产先进高强度钢板汽车制件时,容易产生拉毛和回弹等缺陷,造成大量废品,并降低了模具的使用寿命。在冲压成形先进高强度钢板制件过程中,板料和模具(几何结构、材质、力学性能和表面形貌等),以及成形工艺(冲压力、冲压速度和润滑等)等因素,对成形件表面拉毛以及回弹的影响非常复杂。通过对拉毛和回弹的机理进行理论分析,建立合适的评价方法；采用有限元分析的方法,对影响拉毛和回弹现象的因素和发生位置进行了分析和预测。(1)对拉毛和回弹的发生机理及其影响因素进行了理论分析和研究,根据主要影响因素建立了相应的评价方法,最终模拟研究的结果表明所建立的评价方法是合理的。(2)利用对汽车覆盖件和结构件冲压成形所用的典型工艺进行分析,并参照国际板料成形数值模拟会议(NUMISHEET2011)所给的benchmark4模型,建立了一个U形通道成形模型,利用该模型对双相钢DP780在成形后的拉毛和回弹现象进行了研究。(3)对于成形件表面拉毛方面,采用了商用有限元软件Abaqus6.10中的动力显式程序Abaqus/Explicit,结合MATLAB数值计算方法,对得到的历史输出结果进行计算,得到冲压成形中的关键因素接触压力和滑动距离对拉毛的影响规律,发现拉毛多发生在凹模圆角起始位置,随着冲压行程的增加,接触压力趋于平缓；且对圆形凹模圆角,随着圆角半径增大,极限接触压力逐渐减小。根据分析结果对U行通道成形模具和成形工艺进行了优化,得到能减轻成形件表面拉毛的工艺方案。(4)U形通道成形回弹方面,使用DYNAFORM5.6对回弹量进行分析,对比了有无预应变对回弹的影响,同时对压边圈压边力和板料厚度对回弹的影响规律进行了研究；其中材料在施加预应变后,U形通道回弹量随之增加,且压边力增大后能显著减小回弹,而板料厚度对回弹的影响较小。更多还原

【Abstract】 Advanced High Strength Steels sheet(AHSSs) are widely used due to the rapid development of automobile industry. However, to produce automotive parts with advanced high strength steel by sheet metal forming technology, because of its unique properties (high strength, low ductility)many defects are observed, such as galling and spring-back, which resulted in a large number of discarded products, and reduced the life of the die.In the process of stamping of advanced high strength steel parts, sheet metal and die (geometric structure, materials, mechanical properties and surface morphology, etc.), and the forming process (stamping press, punch speed and lubrication, etc.) and other factors, the influence on galling of parts surface and spring-back is very complicated. To analyze the mechanism and control measures of galling and spring-back, theoretical analysis are used, and the establishment of appropriate evaluation criteria, using the method of finite element analysis, the factors and the location of the galling and spring-back phenomenon are analyzed and forecasted.(1) The mechanism and influence factors of the galling and spring-back are analyzed and researched, the evaluation criteria were also established according to the main factors, the final simulation results of the study shows that the evaluation criteria are reasonable.(2) The typical forming process of automobile panels and structural members are analyzed, the model of benchmark4in international conference and workshop on numerical simulation of3D sheet metal forming process (NUMISHEET2011)was set as a reference, a U-shaped channel forming model was built at last, to study the galling and spring-back of dual-phase steel DP780after stamping.(3) During investigating the galling on the surface of forming parts, the dynamic explicit elastic plastic program-Abaqus/Explicit in commercial finite element code Abaqus6.10had been used, and MATLAB numerical calculation method was used to analyze the history and field outputs of numerical simulation, got the key in stamping factors--contact pressure and sliding distance on the effects of galling,the results shows that galling always developed in the starting position of the die fillet, with the increase of the punching stroke, the contact pressure tend towards stability; towards circular fillet, with the radius increasing, limit contact pressure gradually decreases. U-shaped channel forming die and forming process had been optimized according to the results of the analysis, the process scheme which can reduce the galling on forming surface are got.(4) On the spring-back of U-shaped channel forming,DYNAFORM5.6was used to analyze spring-back quality, comparative analysis was made to check the spring-back with and without pre-strain applied to the blank. The law of blank holder force and sheet thickness on the spring-back were also researched; due to the pre-strain on the blank material, the spring-back on U-shaped channel increases. When the blank holder force increases,which can significantly reduce the spring-back amounts. The impacts of blank thickness on the spring-back are smaller than blank holder force.更多还原