【作者】 王凯峰；

【导师】 王华昌；

【作者基本信息】 武汉理工大学 ， 材料加工工程， 2004， 硕士

【摘要】 金属塑性加工的变形过程是一个非常复杂的弹塑性大变形过程。这时既有材料非线性，又有几何非线性，再加上复杂的边界接触条件的非线性，这些因素使其变形机理非常复杂，难以用准确的数学关系式来进行描述。随着金属塑性成形技术的日益发展，人们对其在成形过程中的变形规律、变形力学的分析越来越重视。有限元法作为一种有效的数值计算方法已经被广泛应用于金属成形过程的数值模拟方面，但是有限元分析软件在使用过程中也存在许多问题，例如数值模拟解的精度问题，直接优化设计技术参数的问题。本文针对这类问题提出模型元分析法及其基本原理和应用，创建定量描述开式模锻变形过程的基本理论体系。本文来源于国家自然科学基金项目——工程塑性理论模型元方法及开式模锻新技术的研究，为定量分析金属塑性变形过程提供了一条新的途径和方法，对丰富和完善工程塑性理论、开式模锻理论及其工程设计方法具有重要的意义。 本文详细阐述了工程塑性理论模型元方法的原理及特点、模型元方法的求解过程、模型单元的划分、时域区段的划分、变形力分布曲线的建立、运用模型元方法求解并优化金属塑性成形问题的变形参数及优化整体变形过程的方法。划分模型单元的方法是首先将研究对象在其时域过程上划分为若干个特征时段，然后对每个特征时段在空间域上用一些特定的物理表面，如分模面、分流面、塑性区与非塑性区的分界面、模腔工作面等，将研究对象划分为若干个模型单元。然后对单个模型单元进行定量描述，包括变形过程中每一瞬时的变形力及变形力分布函数，变形过程中每一瞬时的模型单元的形状及尺寸，变形过程中每一瞬时模型单元的变形场，变形过程中每一瞬时模型单元的应力场，变形过程中每一瞬时的变形力分布与变形体几何形状尺寸间的定量对应关系。 本文根据模型元方法对四种不同情况即毛边宽度b=O或b#O时h_o≤2h_c+h_f和h_o＞2h_c+h_f时的锻靠阶段模型单元运用图解法建立滑移线场，并利用数值分析软件Origin和Matlab进行曲线拟合得到该阶段模型单元的定量描述：该单元在空间中的几何形状及尺寸，该单元的应力场表达式，变形力沿水平对称轴上的分布函数。经研究发现，h_o≤2h_c+h_f时的滑移线场不受接触摩擦条件的影响，仅与滑移线场张角φ或锻件宽度d与毛边高度h_f之比L有武汉理工大学硕士学位论文关，滑移线场内任意一点的应力可用俨或L的函数表示;气>2气+勺时滑移线场受接触摩擦条件的影响，不仅与尹或L有关，而且与接触摩擦:和摩擦角必有关。本文对于不同的毛边宽度b及锻件宽度d与毛边高度hf之比进行定量描述，得到了尺寸与应力、变形力的定量关系。另外通过具体算例进行了验证，结果较为符合实际。更多还原

【Abstract】 Metal plastic deforming process is a kind of quite complex and large elastic-plastic deformation process. The complexity of deformation mechanism contributed by the material and geometric nonlinearity, the nonlinearity of the complex boundary contact condition make the exact mathematic description of plastic deformation impossible. With the lasting development of metal plastic deforming technology the deformation mechanism and mechanical analysis of deformation process begin to attract more and more attention. As an effective method of numerical computation, FEM is widely applied in numerical simulation of metal deformation process. However FE softwares still cannot solve some problems such as accuracy of numerical simulation and optimum design. In this paper MEM (model element method) and its application are presented and fundamentals architecture is created for quantitative describing the deformation process of open die forging. This paper is part of a project sponsored by NSFC, which opens a new path or method for describing metal plastic deformation process and has its significance in theory and practice.This paper stated the fundamentals, features and solving process of MEM which includes the division of model elements and time domain, the creation of strain force distribution curve and the optimum design of deformation process parameters. In model element method to obtain model elements of a deforming body is to determine the feature stages in time domain of a deforming process and then divide the deforming body in different feature stages into several model elements in spatial domain along with some special physical surfaces such as die parting face, flow diversion face, interface of plastic and nonplastic zone, die cavity working face. The quantitative description of a model element includes: 1. the instant deforming force and its distribution function in deforming process; 2. the instant shape and dimension of model element in deforming process; 3. the deformation field of the instant model element; 4. the stress field of the instant model element; 5. the correspondent relationship of instant deforming force distribution and the geometry of subject.By using MEM slip line fields of model element of finish forging phase are studied in four cases: 1. b=0 and h0 2hc+hf, 2. b=0 and h0>2hc + hf, 3. b 0 and h0 2hc + hf, 4. b 0 and h0>2hc + hf. According to slip line fields the quantitative descriptions of them are obtained by curve fitting in numerical analysis software Origin 5.0 and Matlab 6.1. The results include geometry, strain force field expression and deformation force of model elements. In addition, an example is given to compare the results of theory and experience which are in good accordance with each other. It is shown that MEM is a good way to describe the metal plastic deformation.更多还原