多层凹模在变薄拉深模具中的应用

针对壳体零件壁厚和底厚不相等的特点,进行了工艺分析和计算.提出了在1次变薄拉深过程中,采用多层变薄拉深凹模的措施,不仅使模具结构简单,装配方便,而且提高了生产效率,降低了零件的生产成本.同时,对同类型零件的变薄拉深提供了借鉴.     

多道次变薄拉深尺寸精度研究与优化

为了探究多道次变薄拉深工艺参数与筒形件壁厚偏差之间的关系,选取C15-c低碳钢为试验材料进行多道次变薄拉深试验,采用单因素试验设计方案,探究多道次变薄拉深过程中工艺参数(减薄率、凹模锥角和摩擦系数)对工件壁厚偏差的影响规律。采用中心组合旋转设计方法设计试验,采用BBD响应曲面法建立筒形件在多道次变薄拉深过程中工艺参数与壁厚偏差的预测模型,采用Design-Expert10软件对筒形件壁厚偏差进行回归系数及方差分析,并验证回归方程的准确性,对多道次变薄拉深工艺参数进行优化。试验结果表明:经多道次变薄拉深后,工件的实际壁厚均小于理论值,随着减薄率与凹模锥角的增大,工件壁厚偏差整体上呈现增大趋势;随着摩擦系数的增大,工件壁厚偏差整体上呈现先减小后增大趋势;多道次变薄拉深最优参数组合为减薄率45%、凹模锥角9°、摩擦系数0. 14,多道次变薄拉深成形件的壁厚偏差为-0. 0461 mm,达到最小值。     

浮动凹模在变薄拉深模中的应用

针对传统固定式变薄拉深凹模在拉深时工件的壁厚差往往达不到设计要求的缺陷,分析了工件壁厚超差的原因,提出了采用浮动式变薄拉深凹模的措施,通过使用,工件的壁厚差完全达到设计要求。介绍了变薄拉深模结构及工作过程,并给出了变薄拉深凹模浮动量的确定方法。     

对变薄拉深变形特点的探讨

变薄拉深是制造厚底、薄壁、变壁厚、大高度的带底空心件的冲压方法。变薄拉深件一般要经过多次拉深完成,每拉深一次都要退火和表面处理,这似乎成了一个规定。此规定是否正确尚少论述。另外多模变薄拉深的一次变薄率比单模大一倍以上,具有良好的经济效益。但目前对变形原理及提高变薄率的原因还不清楚。本文将通过对变形特点的研究回答以上两个问题。     

多道次变薄拉深速度对筒形件尺寸精度的影响

多道次变薄拉深过程中,拉深速度对整个筒形件的成形质量有着重要影响。为了探究多道次变薄拉深时拉深速度对工件成形后尺寸精度的影响,针对多道次变薄拉深过程中不同的拉深速度,采用有限元数值模拟的方法进行研究,以多道次变薄拉深过程中工件的实际外径与壁厚偏差作为性能指标,探究多道次变薄拉深时拉深速度对筒形件成形后尺寸精度的影响。结果表明:经多道次变薄拉深后,工件的实际外径与壁厚偏差皆小于理论值,随着拉深速度的增大,工件外径呈现先增大后减小的趋势,壁厚偏差呈现先减小后增大的趋势,当拉深速度为15 mm·s-1时,工件实际外径最接近理论外径,壁厚偏差最小。     

不等壁厚锥形件冲压工艺及模具设计

通过不等壁厚锥形件冲压工艺编制,介绍了有色金属变薄拉深毛坯直径的计算方法。经过拉深、多次变薄拉深,合理确定模具间隙,采用合适的润滑剂及润滑方法,拉深出表面质量理想的不等壁厚锥形件。采用该冲压工艺生产壳体,提高了金属材料利用率,降低了生产成本,满足了大批量生产的要求。     

超塑状态下拉深—胀形组合工艺研究

研究了在超塑状态下的拉深－胀形组合工艺，通过计算机合理控制压边力和气胀力，能有效地减少零件的变薄量，使零件壁厚变薄较均匀，从而实现了对变形量大的TC4钣件能够一次成形合乎要求的零件。     

304不锈钢壳级进模变薄拉深工艺及数值模拟

根据经验公式和理论数据对某304不锈钢壳进行直径减小、壁厚变薄的变薄拉深级进模设计,并运用Deform-3D对连续变薄拉深成形过程进行数值模拟,揭示了成形过程等效应力和行程载荷曲线的分布规律。模拟与试验结果表明:成形过程中,坯料的最大应力集中在与凹模圆角和凹模工作带相接触的区域;随着凸模圆角减小,凸模圆角与直壁连接处应力增大,出现危险区域;为防止最后一道拉深过程中凸模容易磨损及产品被拉伤,应合理设计拉深系数、变薄量及凹模圆角;直径减小壁厚变薄拉深件的直壁壁厚均匀。     

Vague集在C15不锈钢变薄拉深工艺参数优化中的应用

在Simufat.forming软件中进行C15不锈钢变薄拉深成形过程有限元仿真模拟,以变薄率、凹模锥角和拉深速度为工艺参数变量,设计3因素3水平L₉(3³)正交试验,以工件变薄拉深过程中的拉深力、残余应力与壁厚回弹量为成形质量评价指标,采用变异系数法对3个评价指标进行客观权重分配,引入Vague集对正交试验结果进行多目标优化,得到最优工艺参数组合以及各工艺参数对综合评价指标的影响顺序。结果表明：变薄率为42%、凹模锥角为9°、拉深速度为10 mm·s^-1时,C15不锈钢变薄拉深工件的成形质量较高。各工艺因素对变薄拉深件的综合成形质量的影响顺序为：拉深速度>变薄率>凹模锥角。对仿真结果进行试验验证,仿真和试验结果的最大相对误差(壁厚回弹量)不大于7.61%,仿真结果具有良好的可靠性,可对实际生产提供理论指导。     

基于Simufact的多道次变薄拉深尺寸精度研究

为了探究多道次变薄拉深中摩擦系数对工件成形后尺寸精度的影响,通过对多道次变薄拉深过程进行有限元仿真,在Simufact.forming有限元仿真软件中选取C15-c低碳钢为试验材料,以摩擦系数为试验参数,进行3道次变薄拉深数值模拟。以3道次变薄拉深成形后筒形件的实际外径与壁厚偏差为评价指标,探究多道次变薄拉深中摩擦系数对工件成形质量的影响。结果表明:经多道次变薄拉深后,工件的实际外径与壁厚皆小于理论值,随着摩擦系数的增大,工件外径呈现先增大后减小的趋势,壁厚偏差呈现先减小后增大的趋势,当摩擦系数取0.12时,工件实际外径最接近理论外径,壁厚偏差最小。     

不等壁厚带台阶锥形件冲压成形工艺与模具设计

分析了不等壁厚带台阶锥形件的冲压成形工艺,介绍了有色金属变薄拉深毛坯直径计算方法,采用合适的润滑剂及润滑方法和确定合理的模具间隙,经过多次拉深、变薄拉深和锥部拉深,成形出了表面质量理想的不等壁厚带台阶锥形件。     

多层凹模变薄拉伸中变形量的合理分配

针对壳体制件壁厚和底厚不等的特点,采用多层凹模变薄拉伸工艺,介绍了多层凹模变薄拉伸工艺的特点,并提出了多层凹模变薄拉伸中变形程度的分配方法,对为同类型制件的变薄拉伸提供了借鉴。     

A Theoretical study of the ironing process in sheet metal forming

Ironing is a very useful process when employed in combination with deep drawing to produce a uniform wall thickness and to increase the wall height. The analysis of the ironing process is conducted based on the general two-dimensional axisymmetrical shell theory incorporated with the Tresca maximum shear stress yield criterion for isotropic thin and thick sheets and the Hosford nonquadratic anisotropic yield criterion for anisotropic thin sheets. A complete plastic solution is obtained and the plastic stress field is found in closed form. A governing equation for a limit ironing ratio (LIR) is found and the total ironing force is also given in the closed form. The predicted maximum ironing reduction under some optimal conditions can reach up to 60%–70%, which is in good agreement with experimental observations. The results of the limit ironing ratio, stress field, and the total ironing force are given and compared with some results based on the finite element technique. The normal and tangential forces are compared with experimental results and it is shown that this prediction gives reasonable results. This study was done when the authors were with the Mechanical Engineering and Engineering Mechanics Department, Michigan Technological University, Houghton, MI 49931, USA.     

变薄拉深工艺与模具设计

以某零件的成形为例,探讨了深孔薄壁件变薄拉深成形的基本原理和方法,初步制定了其成形工艺方案,并对深孔薄壁件变薄拉深成形的模具进行了数值分析和研究,提出了较好的模具成形方案,验证了该方案的正确性。     

厚壁筒形件弧形缩口工艺设计研究

邓厚壁筒形件弧形缩口工艺设计进行讨论，认为采取等体积原则设计变薄引伸弧形模对壁厚进行预成形，完全可以保证最终产品缩口后的尺寸要求，从而取消铰内孔切削加工，该工艺方法在几个产品多年生产实践中应用，取得了较好的经济效益。     

Tool design in a multi-stage drawing and ironing process of a rectangular cup with a large aspect ratio using finite element analysis

Tool design is carried out for a multi-stage deep drawing and ironing process of a rectangular cup with the large aspect ratio using the result of the finite element analysis. The analysis incorporates three-dimensional continuum elements for an elasto-plastic finite element method with the explicit time integration scheme using LS-DYNA3D. The analysis simulates the five-stage deep drawing and ironing process with the thickness control of the cup wall. Simulation is performed in order to investigate the failure by tearing during the forming process at the initial state of tool design. The analysis reveals that the difference of the drawing ratio within the cross section induces non-uniform metal flow which causes severe local extension. The irregular contact condition between the blank and the die also induces non-uniform metal flow which causes local wrinkling. This paper identifies such unfavorable mechanism in the rectangular cup drawing with ironing and proposes a new tool design with the guideline for modification in the design of the process and the sequential tool shape. The finite element analysis result with the improved tool design confirms that the proposed design not only reduces the possibility of failure but also improves the quality of a deep-drawn product. The numerical result shows fair coincidence with the experimental result.     

深孔薄壁件变薄拉深工艺及模具设计

以某深孔薄壁件为例,制定其成形工艺方案。通过有限元模拟重点对反挤压、变薄拉深、双道次变薄拉深等关键工序进行分析,探讨工艺方案的可行性,完成了采用整体凹模结构的双道次变薄拉深模具设计。结果表明,通过工艺与模具设计方案的实施,获得了批量生产的合格深孔薄壁零件。     

Improvement of seizure resistance by roughening surface of stainless steel drawn cup in ironing using die having lubricant pockets

The seizure resistance in ironing of ferritic stainless steel drawn cups using a die having lubricant pockets was improved by roughening the sidewall of the cups. The effect of the surface roughness of the cup on the seizure resistance in ironing was investigated. The seizure resistance using the die having lubricant pockets was higher than that of a polished die, and was heightened by the surface roughness of the cup in the axial direction. To increase the surface roughness of the cup, deep drawing processes with a large clearance and a two-stage deep drawing process were developed. The ironing limits for the roughened cups by the two deep drawing processes were higher than that of the conventionally drawn cup. The thickness of the remaining lubricant film in the sidewall of the ironed cup increased with increasing surface roughness of the cup. It was found that the seizure resistance in ironing was improved by roughening the sidewall of the cup.