联合上限法和主应力法确定模具表面压力分布的研究（I）

提出了一种联合上限法和主应力法确定模具与金属接触表面压力分布的方法。这是一种基于利用上限法确定金属流动和变形区，然后根据主应力法原理计算接触面压力分布的方法，简称ＵＢＭ／ＳＭ联合法。这种方法较其它方法简便，而且能给出计算压力分布的解析式。本文阐述该法的基本原理，并用它计算杯形件反挤时凸凹模表面的压力分布。     

联合上限法和主应力法（UBM／SM法）确定模具表面压力分布的研究（Ⅱ）

本文根据前文＾「１」所提联合上限法和主应力法确定模具表面压力分布的基础原理，计算了圆柱坯料正料正挤压和十字头锻件镦挤时模具表面的压力分布，所得结果与测定很吻合，进一步证明了ＵＢＭ／ＳＭ法实际应用的可靠性。     

功平衡法求解不同型线凹模管材挤压力

在柱坐标系下,建立了功平衡法求解不同型线凹模管材挤压力模型,并推导了不同型线凹模挤压管材挤压力的理论计算公式。经生产反复实验验证,不同型线凹模中锥模挤压管材挤压力公式的计算结果与实测值基本相吻合,平均相对误差为9.6%左右;而相关教材所给主应力法求解的锥模管材挤压力公式计算结果的平均相对误差为14.8%左右。这表明本文推导的不同型线凹模管材挤压力理论计算公式是可行的,具有一定的工程实用性。     

确定挤压凹模模孔位置的强度法

提出了以应力作为目标函数，优化模孔位置的方法，以此设计的挤压凹模，能提高其强度安全系数和使用寿命，以叉车内门架的模拟试件挤压凹模为例，进行了分析计算，结果表明，该方法简明易行。     

塑料异型材挤出模模头熔体压力分析

根据U-PVC的熔体特性,确定U-PVC熔体为非牛顿流体,引入拉比诺维茨修正的哈根-伯肃叶公式,介绍了塑料异型材挤出模模头的熔体压力理论分析方法和模头流道压力计算方式,对熔体压力在模头中流道的分布和影响压力分布的要素进行分析,通过与生产过程中所测熔体压力数据进行对比,确定该压力计算方法的准确性,为U-PVC塑料异型材挤出模头的熔体流道压力的设计提供理论依据。     

注射成型中冷却阶段的研究

采用ＰＳ塑料研究注射成型中冷却阶段的模腔压力变化行为与模腔内制品的温度分布，同时还讨论了熔体温度、模温及浇口封闭压力等参数对模腔压力和温度分布的影响，首次提出了计算出现零模腔压力的公式和确定开模顶出时间（即冷却时间）的条件。     

齿腔分流法冷精锻大模数圆柱直齿轮

为推动大模数圆柱直齿轮冷锻技术的实用化研究,提出了齿腔分流法,即在凹模齿腔深处设置分流型腔。并结合浮动凹模技术,通过数值模拟与物理实验相结合的方法,对齿腔分流法进行分析研究。与传统封闭式冷锻方案进行对比结果表明,该工艺不仅能很好地提高充填性能,而且能很大程度地降低载荷及单位压强。矩形分流型腔优于圆弧形分流型腔。齿形外围部分变形量大,质量好。锻件只需车削或磨削外圆即可得到合格零件,而且齿面纤维分布不受影响。     

基于MARC的混模法冲压回弹分析

针对有模法在成形后需再次计算接触、无模法添加的弹性地基约束无法限制工件纵向刚性位移的问题,提出在MARC中利用混模法对厚板回弹进行分析。首先分析了薄厚板成形的差异性,总结出厚板数值模拟的控制要点,梳理出基于MARC的厚板回弹模拟分析的一般流程;并依据相应分析流程和控制要点设置厚板成形过程。获得成形结果后,以有模法释放凸模与工件之间接触,降低凹模与工件之间的接触反力;其次,再以无模法并附加定位约束释放凹模。最后以某纵梁为例,对混模法进行验证,结果表明,混模法在降低计算成本的同时能够最大限度地降低人为分离拉应力的产生,且回弹值模拟结果与实测结果最为接近。     

基于工时法和CBR技术的注射模报价系统设计与实现

针对注射模价格估算问题，通过设定基点工时和基点工价并确定影响制造工时的主要因素，建立基于工时法的注射模基本制造费用的模型；采用特征匹配法、最近相邻法、交互改写法和指数平滑法，构建了基于CBR技术的注射模生产成本估算模型。结合SQL Server数据库管理系统和Django框架开发了基于B/S架构的注射模报价系统，系统可自动按照报价方案中的公式计算注射模各部分成本、自动检索相似实例、预测生产成本，并实现了报价系统的网络化和可视化。     

冷挤压组合凹模的优化设计

用三维光弹实验研究了冷挤压凹模内壁压力分布规律。改进了约束随机方向法。用所得凹模内壁压力分布规律为有限元计算的载荷边界条件和改进了的约束随机方向法对冷挤压组合凹模进行优化设计。再用三维光弹实验进行验证优化设计与光弹实验结果。最后提出了工程上易于推广冷挤压组合凹模优化设计方法,并与工程界目前普遍采用拉梅公式解析优化设计方法作了比较。     

The Effects of Square and Circular Die-Orifices on the Performance of Combined Extrusion-Forging Process

The upper bound (UBM) and finite element methods (FEM) both coupled with experiments have been conducted to analyze forming performance, load prediction, and pressure analyses in a combined extrusion-forging process using square and circular die orifices. The forming load was predicted by the UBM and the pressure distribution was analyzed by FEM and the performance of both the methods was compared to each other. The required extrusion forging force for square die orifice was found to be higher than in the circular die orifice. The highest pressures occurred on the edges of the square and circular orifices and the pressures increased with increasing friction and deformation. Although extrusion force predictions were found to be slightly higher in UBM than FEM, they were in good agreement with experimental results. The present analyses showed that UBM can be used in rapid prediction of required extrusion-forging loads and material flow, and FEM is more suitable to use in pressure distribution analysis for production of square and cylindrical parts.     

Plastic metal flow under frictional boundary in forward extrusion die and stress distribution of the die

Cracks which progress across the vertical and horizontal plane section of forging dies appear to be caused by stress concentration. This paper reports an investigation into the relationship between the working pressure and the induced stresses distribution of the die during the process.In this paper, a simulation method is presented as a solution to the metal forming problem involving the plastic flow pattern of the metal and working pressure distribution along the tool surface. This method makes use of the Galerkin finite element formulation in conjunction with a special calculation procedure of stress boundary over metal deformation regions by axisymmetric analysis. Also, under the hypothesis of a fluid lubricant layer, the frictional condition between the deformed metal and tool surface is taken into consideration for the analysis.This simulation method is applied to some steady states of plastic deformation in axisymmetric forward extrusion die, and operating the working pressure distributions over the die surface obtained by above method, the stress distributions of the die are calculated by the usual axisymmetric finite element method. Then, the assumption of uniform working pressure usually used for a simplified calculation of the die design is confirmed by comparison with the stress distributions of the die above obtained.     

A MIXED METHOD OF SOLUTION FOR CONTACT STRESSES ON ROLLER

A mixed method of solution for contact stresses on rollers was suggested by the combina-tion of similitude principle.photoelastic method,Hertz's contact theory and numericalcalculation.Thus,not only the distribution regularity of axial contact pressure on rollerof limited length,but also the three-dimensional solution of stresses in the contact po-sitions may be obtained.An actual example is presented in the paper.It shows thatthe practical damaged phenomenon in real roller is in agreement with the result of theanalysis     

凸凹模受力模型与有限元分析

通过对板料成形时的受力分析,建立了凸凹模在拉深过程中的受力模型,完成了对凸凹模的有限元数值分析,得到了凸凹模的应力和变形分布情况。对板料进行强度、刚度校核,得到了随板料厚度的变化凸凹模孔口所受的压力、凸凹模的最大应力和位移的变化规律。可为模具结构的设计、模具材料的选择提供依据。     

Some observations on contact stress measurement by pin load cell in bulk metal forming

The information on the intensity and distribution of the contact stresses in bulk metal forming operations is essential both for the die design and for the process analyst. As the theoretical and numerical methods for the contact stress determination have some analytical constraints a number of experimental methods have been developed. One of them is the pin load cell technique which has been applied in different metal forming operations. In this paper some problems related to the measurement of normal contact stress are presented. The focus is placed on the problem of initial pin position relative to the die surface. Experimental investigations were carried out in order to determine the influence of the axial pin position on the measured contact stress values. The process studied was that of simple upsetting of cylindrical specimens. It has been shown that the axial pin position 0.15mm above the die surface prior to the defonnation gives the most realistic results.     

Analysis of Dynamic Loads on the Dies in High Speed Sheet Metal Forming Processes

During high-speed sheet metal forming processes, the speed at which the work piece contacts the die tooling is on the order of hundreds of meters per second. When the impact is concentrated over a small contact area, the resulting contact stress can compromise the structural integrity of the die tooling. Therefore, it is not only important to model the behavior of the workpiece during the high-speed sheet metal forming process, but also important to predict accurately the associated workpiece/tooling interface loads so that engineers can more confidently propose robust die tooling designs. The foundation to accurate predictions of contact stress on die tooling is a reliable contact model within the context of a finite element simulation. In literature, however, there exists no comprehensive guideline for establishing a contact model for high-speed sheet metal forming processes using the finite element method. In this paper, mathematically justified contact model recommendations are offered for the electrohydraulic forming (EHF) process.     

Tooling-integrated sensing systems for stamping process monitoring

In-situ stamping process monitoring plays a critical role in enhancing productivity and ensuring part quality in sheet metal stamping. This paper investigates the realization of two sensing methods to create a tooling-integrated sensing system: mutual inductance-based displacement measurement for sheet draw-in, and distributed contact pressure measurement at the tool–workpiece interface. The two sensing systems are complementary in nature, and together, they significantly enhance the on-line observability of the stamping process. The performance of the draw-in sensor was evaluated using numerical simulations and experiments in a small-scale and a large-scale lab setup, and its effectiveness has been confirmed under the presence of wrinkled sheet. To study the spatial and temporal variations of the tool–workpiece contact pressure in a stamping operation, experiments were conducted on a customized panel stamping test-bed with an array of thin-film force sensors embedded below the die flange and die cavity. The force sensor data were then numerically interpolated to form the contact pressure distribution across the tool–workpiece interface, based on the thin plate spline (TPS) method. Comparison between the interpolated pressure obtained from the surface generation techniques and direct measurement using redundant sensors and a press mounted load cell confirms the validity of the new contact pressure sensing method. The integrated sensing technique provides insight into the stamping process by quantifying process variations and providing a reference base for process control to reduce product disparities. Additionally, new product and process designs can be created based on the quantified and referenced variations.     

模具寿命延长技术研究

在锻压力的大小与内在因素——材料屈服强度及加工硬化和外界因素——加压接触面积等有关的基础上,提出了局部成形、坯料形状改进、工序改进和塑性流动控制等4条提高模具寿命的设计方法,并提出了相应的延长模具寿命的工艺措施,这些措施已用于锻压工艺设计中,有效地延长了模具寿命,增加了企业效益。     

轧辊接触应力的混合解法

本文将相似理论,光弹性方法,Hertz接触理论和数值计算方法结合起来,提出了对轧辊接触应力的一种混合解法,此法不仅可以得到合理的轴向接触压力分布规律,而且也可以得到接触区内的应力场三维解,应用该法对某轧机工作辊进行的接触应力分析,所得结果与轧辊的实际破坏情况吻合,说明本文提出的方法是可靠的。