共查询到19条相似文献,搜索用时 203 毫秒
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由于非对称截面的立边长度不同,辊弯成形过程中易出现扭曲缺陷。采用实验及有限元模拟相结合的方法,对非对称截面的辊弯成形进行研究。建立了超高强钢辊弯成形的有限元仿真模型,提出了通过倾斜前置轧辊来减轻V型非对称截面扭曲缺陷的方法,对前置轧辊倾斜角度的计算方法进行了探讨。结果表明:对于V型非对称截面的辊弯成形,倾斜前置轧辊改变了板材进入成形轧辊的状态,前置轧辊的倾斜角度φ=8.9°,扭曲角度减少40.9%,变形区纵向应变的峰值明显降低,且应变量减小;两侧立边所受的弯矩差值是引起扭曲缺陷的重要因素,倾斜前置轧辊使得板材两侧立边所受弯矩差值的大小和方向发生变化,合弯矩从0.18 N·m变为17.60 N·m,方向从转向短立边变为转向长立边,从而一定程度上抑制了扭曲缺陷。 相似文献
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大尺寸封闭截面铝型材拉弯工艺研究 总被引:11,自引:5,他引:11
本文以数值模拟为手段 ,利用大型商业化有限元软件Pam Stamp ,针对铝型材框架式车身生产中的关键技术———铝型材高精度弯曲成形进行了深入系统的研究 ,模拟了大尺寸封闭截面铝型材AA60 82 (T1状态 )在不同弯曲半径下的拉弯成形过程。研究结果表明 ,铝型材拉弯成形极限主要受脱模、起皱及壁厚减薄的限制 ,而成形精度主要受回弹和截面变形的影响。截面形状、弯曲半径和拉伸量是铝型材拉弯工艺中的 3个重要参数 ,确定正确的拉伸量是拉弯工艺成败的关键。文章通过对计算结果的分析 ,提出了上限拉伸量和下限拉伸量及相应的确定方法 ,并给出了铝型材拉弯工艺中拉伸量的取值原则 相似文献
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针对轿车用复杂截面PVC塑料包覆铝型材密封条的三维拉弯成形,采用控制拉伸量的方法,通过选择合理的预拉量、恰当的成形模具截面及型材间填充物,对该截面型材进行了平面和垂直拉弯成形实验,得到了该型材平面和垂直拉弯的半径回弹量。结果显示,垂直拉弯回弹量是平面回弹量的1倍多,实验结果为研制该型材及同类产品拉弯工装模具和工艺参数选择,提供了依据。 相似文献
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1 Introduction Thin-walled tube bending parts have been increasingly used in many industry fields such as aviation, aerospace and automobile for their easy satisfaction in light weight, high strength and low consuming. The numerical controlled(NC) rotar… 相似文献
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《Journal of Materials Processing Technology》2014,214(2):311-317
A traditional rotary draw bending die on the numerically controlled (NC) tube benders or other benders can bend tubes with only one kind of outer diameter. It is difficult for such a situation to meet the requirement of modern manufacturing with characters of much varieties and small batch. The present study proposed a new concept of rotary draw bending die called MDB-Die (Multiple-diameter Bending Die), on which tubes with different outer diameters within a definite range can be bent using the same die by only adjusting the pads inside the die set. Numerical and experimental approaches were employed to investigate the forming process of tubes with different outer diameters when bent on the MDB-Die, especially on the characters of force and elastic-plastic deformation of tube wall, and the effects of groove shapes and bending parameters on the cross-section distortion and wall thinning in the process. Analytical expressions in simple tube bending based on plastic theories given by Tang (2000) for calculating the magnitude of stresses, together with the wall thickness change, deviation of the neutral axis, and section flattening, were also used for comparison. The result proved that tubes with different outer diameters (from 18 to 25 mm in the study) can be bent successfully on MDB-Die without degrading the bending quality, i.e., the aspect ratios of section distortion of less than 5% and wall thinning of less than 7.8%. 相似文献
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起皱、局部壁厚过度减薄是封头冷拉深常见的缺陷,严重制约着拉深封头质量、成形极限的提高以及生产过程的正常进行。文章采用ABAQUS软件建立椭球封头拉深成形的三维有限元模型,并验证该模型的可靠性;发现了椭球封头拉深过程中易于出现的悬空区起皱和过度减薄两种缺陷,并分析了其形成机理,同时研究了工艺参数对缺陷产生的影响规律。研究发现,悬空区承受双向压应力区域的范围与周向压应力的大小对起皱影响明显,而切向拉应力对壁厚的减薄影响显著。增大压边力、摩擦系数和减小凹模圆角半径,可减小悬空区承受双向压应力区域的面积和周向压应力值,进而减小起皱的倾向,而过大的压边力、摩擦系数和过小的凹模圆角半径,则导致悬空区切向拉应力过大,可加剧壁厚的减薄。 相似文献
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发动机罩外板结构简单,表面平直,曲率半径大,整体高度低。如果对外板拉深成形时的毛坯形状与尺寸、冲压方向与速度、拉延筋布局与结构以及压边力大小、凸凹模间隙、摩擦润滑等工艺因素的选择或控制不当,则容易导致其卸载后的回弹量增大。文章以eta/DYNAFORM软件为计算平台,利用正交实验法,对某轿车发动机罩外板的拉深回弹现象进行了数值分析,并在此基础上确定了控制回弹的拉深工艺参数和模具结构参数。实验结果表明,该外板零件的拉深回弹呈扭曲倾向,即存在一部分区域上翘,而另一部分区域下陷,其中下陷趋势较上翘明显。根据数值模拟分析得到满足外板技术要求的最优拉深工艺参数和模具结构参数组合为:压边力900kN,虚拟冲压速度1000mm/s(相当于实际冲压速度的10倍),拉延筋高度6mm,凸凹模间隙0.8mm。 相似文献
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分析了压铸件气孔、缩松、夹杂、冷隔、尺寸超差及表面质量问题等缺陷特征,从模具设计、熔炼工艺及涂料使用等方面对缺陷产生的原因进行了探讨。结果发现,在合理的零件结构基础上,通过改进浇注系统,调整模具温度及金属液温度,并采用正确的喷涂方法,可有效防止压铸件缺陷的产生。 相似文献
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Air gap formation during solidification in cylindrical castings of pure aluminium and eutectic Al-Si
Casting of aluminium and eutectic Al-Si in a cylindrical mould has been performed. The air gap formed between the inner mould wall and the solidified shell was measured throughout the solidification process. Simultaneously the temperature distribution in the metal and the mould was measured. Calculations of the shrinkage of the metal were performed. The shrinkage due to thermal contraction was found to be too small to fit the measurements. A new model for the solidification process and the air gap formation was used, where the effect of the formation and condensation of lattice defects was considered. The condensation of lattice defects was used to explain the shrinkage and the air gap found experimentally. 相似文献
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分析讨论了汽车前托架零件的成形工艺及有限元分析前处理中工具体与板料的网格划分;探究了摩擦系数、压边力对板料成形的影响。结果表明,较小的摩擦系数增加了零件的起皱趋势,但对破裂缺陷有较大改善;基于模面破裂危险区的形变分析,对模面修改后进一步进行压边力优化,从而进行了符合实际工艺的多阶段前托架成形优化分析。采用优化后的工艺参数和模面形状进行实际试冲,得到了合格的零件,板料变薄率和增厚率分别在20%与5%的允许范围内。实际试冲与数值模拟的板料厚度应变误差在4%范围内,且板料轮廓收料情况相符。 相似文献