板条通过光滑楔形模具拉拔的精确上限解

对板条通过光滑楔形模具，截面缩减率为特定值的拉拔问题，利用上限法求解，首先采用和滑移线场接近的运动许可速度场，将中心扇形场分成n个相等的等腰三角形钢性块，推导出了含有n的上限解的通用表达式，然后令n→∞，便得到了该问题和滑移线解相同的精确上限解。     

基于主应力法和滑移线法求解圆棒料锥模拉拔力

针对圆棒料锥模拉拔,建立了拉拔力的计算模型,通过对微元体进行受力分析,建立了力的平衡微分方程,并引入屈服条件、摩擦条件和边界条件,采用主应力法,推导出单位拉拔力的计算公式;另外,利用滑移线理论,建立了变形区的滑移线场,依据屈服准则和汉基方程,求解出金属圆棒料拉拔时单位拉拔力的计算公式,进而求出总拉拔力。通过实例进行了验证,主应力法得到的拉拔力为4. 2 kN,滑移线法得到的拉拔力为2. 6 kN,经验公式法得到的拉拔力为4. 6 kN。结果表明,根据主应力法和滑移线法求解拉拔力符合工程要求,能够实现设备吨位的选择。     

用相似解析法求解平板抽拉问题

前言滑移线场理论在平面应变问题中已经得到了广泛的应用,但对于较复杂的塑性变形问题,如平板经过光滑模具的抽拉问题,过去一般都采用图解或数值方法求解,而无法用解析方法求解,因此难以分析结果,不易提高计算精度。本文利用作者提出的相似解析法,即根据塑性变形区内的速度场和滑移线场之间存在的几何相似性进行求解的方法,以及得出的由两条相等半径的圆弧滑移线所确定的滑移线场(简称等半径双圆弧滑移线场)的解析表达式,对上述问题进行求解,得到了满意的解析解答。     

基于滑移线理论的一种模型单元

特征单元是模型元法求解塑性加工问题的基础。本文应用滑移线理论的图解法提出并求解出一种特征单元 ,推导出该特征单元形状的确定方法及单元的应力表达式 ,并对单元滑移线场变化规律作出全面定量描述。本文丰富了特征单元库 ,求解同类问题可以直接套用这种单元 ,简化了计算过程     

半无限体压入问题的流函数解法

对平冲头压入半无限体问题建立了流函数速度场，证明该场散度为零，旋度不为零，采用上界定理对该速度场积分结果与滑移线结果一致，流线为一族曲线滑移线。     

柱坐标流函数解析半无限体压入

对平冲头压入半无限体问题建立了柱坐标流函数速度场，证明了该速度场散度为零，旋度为剪切应变速度的２倍。采用上界定理对该速度场积分，变形力与滑移线法结果相一致，证明了流线为一族同心圆（曲线族滑移线），柱坐标流函数的解法比直角坐标的简化。     

实例证明上限解的极值等于理论载荷

文章通过滑移线法和上限法两种方法求解光滑平冲头压入半无限体问题,以滑移线法求解结果作为问题的理论载荷,上限法采用简化滑移线场的刚性三角形上限模式。初始上限解大于理论载荷,但随着刚性块的增加,上限解向下逼近理论载荷。用多个三角形组合的多边形逼近滑移线场中的有心扇形,通过归纳法求得的上限解的极值恰好等于理论载荷。     

平板镦粗模型单元的研究分析

本文应用滑移线理论来求解平板镦粗模型,描述了在不同宽径比下的滑移线场,确立该模型单元的应力场表达式。描述其滑移线场的变化规律,最后运用ABAQUS软件对圆柱体镦粗进行数值模拟,将模拟值与理论值进行对比,对理论值进行验证。     

主剪应力法及其在锥模薄管拉拔与缩颈中的应用

提出了主剪应力法，对沿主剪应力迹线正应力的变化规律给出了数学描述，并将此法用于锥模薄壁管的典型成形工序的求解，其结果与用平衡方程和Ｍｉｓｅｓ屈服准则联立求解的解析解相一致。主剪应力法的实际质是在轴对称平面应力问题中将滑移线场理论仅考虑一对正交的最大剪应力迹线的思想扩展到考虑三对正交的主剪力迹线中的任一对，该方法的提出将扩大滑移线场理论的适应范围。     

剪切力的滑移线场解

本文介绍平冲模压厚板的滑移线场和实验得的滑移线场计算剪切力的方法,在和实验数据进行分析比较的基础上,提出了用直观塑性法所得滑移线场求解剪切力的公式计算。     

锥形凹模板料不起皱条件和极限拉深系数

本文通过分析锥形凹模拉深变形过程，利用试验数据，列出了板料不起皱的条件；并运用主应力法和板料弯曲的外力功等于内力功的原理以及摩擦理论，推导出加工硬化时变形区危险断面最大拉应力计算公式和无压边装置锥形凹模的圆筒件极限拉深系数计算公式；均由实例进行验证。拉深系数为０．３９的两种零件，从试制到生产，证明了锥形凹模是可以实现深拉深的模具。     

薄壁铜管游动芯头拉拔过程拉拔力影响因素分析

为准确把握薄壁铜管游动芯头拉拔过程的拉拔力,该文应用非线性有限元分析软件ABAQUS建立了薄壁铜管游动芯头拉拔过程的弹塑性有限元模型,分析了内外模具锥角、游动芯头定径段长度、延伸率、摩擦因素以及拉拔速度等工艺参数对薄壁铜管拉拔过程中拉拔力的影响规律。研究表明,芯头或外模的锥角存在一个最佳组合范围,芯头定径段长度和拉拔速度对拉拔力的影响作用非常小,延伸率和摩擦系数的增加将引起拉拔力的明显增加。研究结果为实际生产中的工艺改进提供了科学依据。     

管材拉拔模具定径区摩擦力的研究

比较精确地确定管材在拉拔时的拉拔力,对于制定合理的拉拔工艺,充分发挥拉拔机的能力,保证拉拔机在拉拔过程中安全可靠地运行均具有重要意义。研究了在空拉、固定芯头拉拔和游动芯头拉拔三种状况下拉拔模具定径区摩擦力对拉拔力的影响,并推导出合理的拉拔力计算公式。     

Effects of die surface patterning on lubrication in strip drawing

Strip-drawing tests with annealed stainless steel samples involving small strains were used to investigate the effect of surface texturing in tribological applications involving mixed lubrication and plastic deformation. Dies were prepared with surface patterns composed of circular pockets and parallel grooves, and comparison tests were performed with highly polished dies. The effects of surface texturing were detected by friction force measurements and examination of the deformed strip surfaces, under conditions of oil lubrication. Surface patterns consisting of circular pockets with very low area coverage did not improve the tribological performance. For grooves with larger area coverage (≈25%), significant effects were observed on the friction between the dies and the strip, which were reflected in the drawing force. The performance was strongly influenced by the relative orientation between the grooves and the drawing direction. For grooves perpendicular to the drawing direction, the friction was greatly reduced; the grooves were believed to act as lubricant reservoirs and to induce microplastohydrodynamic lubrication. On the other hand, when the grooves were oriented parallel to the drawing direction, the friction was much greater and the strip surface finish became poorer; these grooves were believed to allow the lubricant to escape from the contact.     

药芯焊丝的拉拔力计算模型

通过药芯焊丝拉拔应力分析,建立了冷轧钢带法制造药芯焊丝的拉拔力计算模型,分析了影响拉拔力的因素。影响药芯焊丝拉拔的因素很多,其中钢带的力学性质、焊丝的变形程度、拉丝模的内孔尺寸、拉拔速度、摩擦与润滑条件对拉拔应力影响较大。在低速拉拔时,拉拔应力随拉拔速度的增加而增大。中速拉拔时,拉拔应力随拉拔速度的增大而下降。继续增大拉拔速度,拉拔应力变化不大。     

可压缩材料轴对称和平面应变单位挤压力之间的关系

在轴对称子午面和平面应变变形平面几何尺寸相同、外摩擦一致的前提下，利用有限元法、滑移线法和实验方法探讨了可压缩材料轴对称正挤和平面应变正挤间单位挤压力的关系。结果表明，轴对称单位挤压力与平面应变单位挤压力间的比值是一个数值范围，Px＝(1．2—2．1)Pp；该比值与相对密度、挤压比、摩擦条件以及材料状态有关。     

Experimental characterization of disturbance force in a linear drive system with high-precision rolling guideways

This paper describes a characterization method of disturbance force in a linear drive system supported by high-precision rolling guideways. Disturbance force is divided into the friction component and other disturbance force. Experimental characterization method to analyze effect of global position, effect of micro-position and effect of table velocity is suggested. With stop-dwell-go and reversal motions, characterization experiment and analysis are conducted on a positioning system consists of a linear motor and rolling guideways. Firstly, global disturbance force depends on global position and stick and slip friction components are characterized. Secondly, stick friction force is separated from stick and slip friction force in the micro-region. Thirdly, influence of the velocity is analyzed. Finally, a modified single bristle model, which describes friction characteristics in the micro-regime, is shown to simulate the measured disturbance force.     

硬质合金拉丝模的几何形状与使用寿命的关系

从力学角度分析了硬质合金拉丝模最小变形功与拉丝模工作半角α的关系 ,模孔壁表面压力 Km与 α和减面率 γ的关系 ,拉拔力 P与 α的关系 ,研究了模孔壁压力对拉丝模寿命的影响 ,提出了拉拔力最小时的最小工作锥半角α。     

Friction analysis of thermally sprayed coatings finished by ball burnishing and grinding

Thermally sprayed coatings offer a promising approach as efficient method to increase the wear-resistance of sheet metal forming tools. However, the roughness of thermally sprayed surfaces is quite high. The use of these coatings for deep drawing tools results in poor sheet surface qualities and low drawing ratios. Because it is suspected that high friction is the reason for the low drawability, hard metal coatings (WC–12Co), deposited by high velocity oxygen fuel flame-spraying, were machined by grinding and ball burnishing to improve their friction behavior and the accuracy of the tool shape. The investigation was conducted by plane strip drawing tests. Strips of high strength steel were mated with these novel and effective coatings at different normal contact pressures and drawing velocities. Uncoated friction elements made of C60 steel were considered as reference during the analysis. The results revealed that coated but unmachined friction elements showed high friction values, which led to scratch marks on the sheet surface after drawing. Applying the finishing processes, the friction coefficient could be reduced significantly. Additionally, deep drawing tests were carried out to determine the drawing ratio for coated, unmachined as well as for processed, coated dies. Thermally sprayed and ball burnished as well as thermally sprayed and ground coatings are feasible for deep drawing. Due to the post treatment, the drawing ratio β = 1.8 was increased to 2.0. This is consistent to the results of the friction tests.     

铜管游动芯头拉拔模具角度优化的有限元模拟

采用二维轴对称弹塑性有限元法对比分析了不同外模模角和游动芯头锥角的配合对拉拔铜管的影响。模拟结果表明,最优外模模角和芯头锥角配合与拉拔应力、摩擦力和芯头稳定位置等因素有关,外模模角、芯头锥角以及两者之间的角度差过大或过小都对铜管的质量不利,这对于精密铜管游动芯头拉拔模具角度的选择,有着一定的参考价值。