变速冲压对板料拉深成形质量影响研究

发布时间：2018-05-30 21:34

本文选题：304不锈钢 + 盒形件　；参考：《合肥工业大学》2015年硕士论文

【摘要】：304奥氏体不锈钢兼顾了室温力学性能、加工性能和耐蚀性等多方面优良性能以及经济性,且304不锈钢具有应变速率敏感性,是非常优秀的冲压成形用钢板,在汽车等领域拥有广阔的应用前景。盒形件是金属薄板拉深成形中较为典型的冲压件,研究这类件的成形规律具有重要的理论与实际意义。充液拉深作为一种全新的软模成形方法,可简化模具结构、降低生产成本和提高零件成形质量,受到世界冲压行业的高度认可和广泛关注。另外一方面,根据冲压零件不同阶段的变形特点,采用变化的成形速度模式,通过控制板料流动和应变速率的大小,改变变形区的应力、应变状态,可以提高板料的成形性能和减少拉裂起皱等缺陷。因此,本文以304不锈钢板材为材料,研究变化的成形速度对典型冲压件盒形件充液拉深过程的影响,为该类零件冲压速度的选择提供参考。其主要研究内容包括：(1)对304不锈钢板材进行室温拉伸实验,深入研究应变速率对304不锈钢室温拉伸组织与性能的影响,研究结果表明应变速率变化引起304不锈钢中马氏体含量的改变,从而影响304不锈钢的最终力学性能。(2)对盒形件的拉深成形工艺进行分析,并从最大主应变(x1)、最大减薄率(x2)、最大等效应力(x3)、节点厚度变化量之和(x4)、安全节点比例相反数(x5)五方面综合考量,建立盒形件拉深成形质量评价标准y,y值越小,表明成形质量越好。(3)结合CAE技术和正交试验设计方法,通过极差分析得出拉深各阶段速度对成形质量影响大小依次为：V1V3V4V2V5 (V1-V5分别为拉深行程中5个阶段：0、1/4H、1/2H、3/4H、H对应的成形速度,H为拉深深度)。数值模拟结果表明采用正交试验优化后的成形速度曲线(即V1 (8mm/s)-V2(3mm/s)-V3 (3mm/s)-V4 (13mm/s)-V5 (3mm/s))进行盒形件的充液拉深,所获得盒形件的成形质量得到提高,综合指标y值减小到0.1203。(4)利用BP神经网络智能预测模型对不同成形速度对应的成形质量数据样本进行训练,保证最大误差不高于5%,再利用遗传算法进一步寻优,最终获得“最优”成形速度曲线,即V1 (3mm/s)-V2(7mm/s)-V3(11mm/s)-V4(14mm/s)-V5(8mm/s)。数值模拟结果表明相比于正交试验优化后的成形速度曲线,采用神经网络结合遗传算法优化后的成形速度曲线进行充液拉深所获得盒形件的成形质量得到进一步提高,综合指标y值进一步减小到0.0827。(5)对课题组现有100t充液拉深设备进行改进,实现变速拉深。在此基础上,对不同成形速度对盒形件充液拉深成形质量影响进行实验研究,验证BP神经网络和遗传算法获得“最优”成形速度曲线的可靠性。实验结果表明,在盒形件充液拉深的生产实际中,我们可采用先上升后下降型成形速度曲线,且保证速度变化平稳,进一步提高盒形件的成形质量。
[Abstract]:304 austenitic stainless steel has excellent mechanical properties at room temperature, processing property and corrosion resistance, and economy. 304 stainless steel is a very good sheet for stamping forming because of its strain rate sensitivity. In the automobile and other fields have a broad application prospects. Box is a typical stamping part in sheet metal drawing. It is of great theoretical and practical significance to study the forming law of this kind of parts. As a new soft die forming method, liquid filling drawing can simplify the die structure, reduce the production cost and improve the forming quality of parts. It has been highly recognized and widely concerned by the stamping industry all over the world. On the other hand, according to the deformation characteristics of different stages of stamping parts, by controlling the sheet metal flow and the size of strain rate, the stress and strain state in the deformation zone can be changed by adopting the variable forming speed mode. It can improve the formability of sheet metal and reduce the defects such as crack and wrinkle. Therefore, in this paper, 304 stainless steel sheet is used as the material to study the influence of different forming speed on the drawing process of typical punch box parts, which provides a reference for the selection of stamping speed of this kind of parts. The main research contents include: (1) tensile test at room temperature on 304 stainless steel sheet, and further study on the effect of strain rate on tensile structure and properties of 304 stainless steel at room temperature. The results show that the change of strain rate leads to the change of martensite content in 304 stainless steel, which affects the ultimate mechanical properties of 304 stainless steel. From the five aspects of the maximum principal strain (x 1), the maximum thinning rate (x 2), the maximum equivalent stress (x 3), the sum of the changes of the thickness of the joints (x 4) and the opposite ratio of the safe joints (x 5), the smaller the yy value of the evaluation standard for the quality of the box drawing forming is established. It shows that the better the forming quality is, the better is the combination of CAE technology and orthogonal design method. By means of range analysis, it is found that the influence of drawing speed on forming quality is in the order of: V1V3V3V4V2V5 / V1-V5, respectively. The forming speed corresponding to 5 stages in the drawing stroke: 1 / 0 / 4HU / 1 / 2H / 3 / 4H / H is the depth of drawing. The results of numerical simulation show that by using the optimized velocity curve (that is, V1 / 8mm / sn-V2N 3mm / s-V3 / 3mm / sr-V4 / 13mm / s-V5 / 3mm / s), the forming quality of the box-shaped parts has been improved by using the optimized forming velocity curve (V1 / 8mm / s-1 / -V2n / 3mm / v _ 3 / v _ 4 / 13 mm / v _ 5 / 3mm / s ~ (-1). The comprehensive index y value is reduced to 0.1203.4.) the BP neural network intelligent prediction model is used to train the sample of forming quality data corresponding to different forming speeds to ensure that the maximum error is not higher than 5, and then the genetic algorithm is used to further search for the best. The "optimal" forming speed curve was obtained, that is, V1 / 3mm / sm-1 / V2 + 7mm / V3 / V3 / 11mmsN / V4 / 14mm / V5 / 8mm / sg. The numerical simulation results show that compared with the optimized forming speed curve of orthogonal test, the forming quality of the box is further improved by the use of neural network and genetic algorithm to optimize the forming speed curve. The comprehensive index y value is further reduced to 0.0827.5) the existing 100 t hydraulic drawing equipment in our group is improved to realize variable speed drawing. On the basis of this, the effect of different forming speeds on the forming quality of liquid filled deep drawing of box-shaped parts is studied experimentally, and the reliability of the "optimal" forming speed curve obtained by BP neural network and genetic algorithm is verified. The experimental results show that in the production practice of liquid-filled drawing of box-shaped parts, we can use the curve of forming speed of rising first and then decreasing, and ensure that the change of velocity is stable, and further improve the forming quality of box-shaped parts.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG386

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