基于数值模拟的厚板精冲凸模磨损研究

以5 mm厚的AISI1010板料为研究对象,利用DEFORM-2D有限元软件对其精冲过程进行数值模拟,分析了精冲凸模的磨损过程,研究了模具间隙、冲裁速度以及凸模圆角半径与精冲凸模磨损深度之间的关系,研究发现:精冲凸模的磨损深度随着模具间隙的增大而逐渐减小,而随着冲裁速度以及凸模刃口圆角半径的增加,精冲凸模的磨损深度呈现逐渐增大的趋势。数值模拟的结果对于精冲模具的设计与优化具有重要的指导意义。     

冲裁模刃口尺寸的计算原则及方法

冲裁件的尺寸精度取决于凸、凹模的刃口尺寸及公差。为了获得合格的冲裁件，在模具设计中应根据冲裁件的尺寸和公差等级、冲裁间隙、模具磨损规律、模具制造方法和成本等来确定凸、凹模的刃口尺寸和公差。     

基于Deform应用下的冲裁模具变量对凸模应力的影响分析

冲裁模具的冲裁间隙、刃口圆角半径、冲裁速度、摩擦因数是模具设计的几个重要参数,基于Deform软件对不同间隙、刃口圆角、冲裁速度以及摩擦因数模拟出对冲压模应力的影响,并对冲压模具的应力影响参数进行正交仿真试验设计,通过正交仿真实验分析寻找规律并选出最优的组合。     

凹模刃口后角与模具寿命关系的探讨

凹模刃口后角对冲裁力、胀力及模具寿命都有很大影响。它可以减小冲裁力和胀力,甚至使胀力为零。增大凹模有效刃口高度,甚至为全刃口,从而可以大大提高模具的刃磨次数,达到延长模具使用寿命的目的,并能使壁厚小于1.5δ的复合模具有正常的使用寿命。一、凹模刃口型式与冲裁力的关系一般假设冲裁过程为纯剪切,则冲裁力P=L·δ_(cp)·δ。在不考虑其它因素的前提下,凸模工作端面压应力σ_压=P/F(F-凸模工作端面积)。此时凹模如果为直刃口,间隙又小,那么当冲裁件脱离材料后,由于材料内部     

聚氨酯橡胶在冲裁模中的应用

图1所示的片状弹簧零件,材料为0.1mm厚的锡磷青铜。按一般的冲裁模具制造时,其凸凹模均由线切割机床加工而成。在零件宽0.5mm的凹模处留下了由钱切割机床加工的走丝微小圆角,在凸模处则形成清角。而在其根部的凸模处留下了走丝微小圆角,在凹模处则形成清角(如图2)。在零件外形复杂,间隙值很小的情况下,修配间隙并使其值保证均匀分布     

合理大间隙冲裁模的应用

冲裁模的应用量大面广,它约占冲模总数的50％～60％,而冲裁间隙是冲裁模设计与制造中最重要的技术参数,它直接关系到冲件的断面质量、尺寸精度、模具寿命和力能消耗。实际生产表明,冲裁间隙的合理选用,对冲压生产的技术和经济效果有很大影响。 50年代我国一直沿用原苏联的冲裁间隙值,由于其数值过小,在生产中产生不少问题:如产品质量差,模具制造困难,使用寿命低,凹模易胀裂,小凸模易折断等。过去在应用原苏联间隙采用斜刃口凹模冲裁时,冲压工人在生产实践中,常有这样一个感觉,新制冲裁模的刃磨寿命往往不如经过几次修磨刃     

冲裁模导向装置的精度

在冲裁模设计时,规定凹模与凸模之间有一定的间隙值。从凸模切入毛坯到推出零件,在整个使用过程中,凸、凹模的配合情况应保持不变。而实现这种正确的配合,通常采用两种结构型式的模具:即导板模和带导柱冲     

冲裁间隙对模具寿命的影响

在冲压加工中,模具的间隙直接关系到产品的质量和模具的寿命。通过生产实践的观察,冲裁零件上毛刺的大小,与模具刃口的钝角有关,刃口变钝与冲裁间隙有密切的关系。本文介绍模具变钝的原因及模具最隹间隙值。一、模具刃口受力分析与变钝的原因 1.模具刃口受力分析在冲裁加工中,把被冲材料分为三个区域,如图1所示。Ⅰ区域为凹模上的材料,Ⅱ区域为凸模与凹模间隙中的材料,Ⅲ区域为凸模下的材料。     

叠层金属薄板材料的冲裁特性研究

在冲裁分离过程中,单层与叠层金属板材存在很大的差异。通过对比2者的不同特点,选取并分析微元体的应力应变状态,发现在叠层冲裁过程中,变形区内中间层的材料处在3向压应力状态,表现出很强的可塑性。分析冲裁中各因素对应力状态的影响发现,合理地减小凸模与凹模的间隙可以提高变形区的静水压,抑制裂纹的产生,使冲裁过程控制在塑剪变形阶段。以叠层母线冲孔为例来验证理论分析,试验结果与分析一致,叠层冲裁比同厚度单层冲裁所要求的模具间隙更小,其值取在普通冲裁间隙经验公式的基础上乘以0．4左右的修正系数为宜。     

聚乙烯薄膜在拉深中的应用

拉深是利用模具使冲裁后得到的平面毛坯变成开口的空心零件的冲压工艺方法。毛坯在拉深变形的全过程中,其所受的摩擦力有:毛坯与凹模圆角处的摩擦力F_1,毛坯与压边圈的摩擦力F_2,毛坯与凸,凹模间隙中的摩擦力F_3和毛坯与凸模间的摩擦力F_4。其中摩擦力F_4在拉深过程中是一个有利的因素,它能使底部以及与底部相连的圆角部分应力重新分布,     

一种新的冲裁间隙实验模具的设计

冲裁间隙是影响冲裁件质量、模具寿命、冲裁力的重要因素,而冲裁间隙实验又是材料加工专业中的基础实验,在专业课程的学习中具有非常重要的作用。在以往的教学中开设冲裁间隙实验时为了改变冲裁间隙的大小,需要多次更换模具,非常不方便。现开发的是一种新的冲裁间隙实验模具,能实现不拆卸模具的情况下快速更换冲裁凸模,从而为实验提供不同的冲裁间隙值,克服了传统实验中多次装卸模具、调试模具的缺点,节约了实验时间,提高了实验的可靠性和安全性。该模具已经申请了实用新型专利,并获授权。     

薄板微小齿轮落料模的试制与探讨

在薄板微小齿轮落料模的试制过程中 ,分析了凸、凹模的加工方法及其间隙确定、研配等工艺方案的可实施性。采用上、下冲裁法 ,提高变形区静水压力 ,解决了冲裁中出现的齿尖塌陷、毛刺等缺陷。指出适当提高相对变形速度、提高静水压力 ,可有利于改善微小型制件的冲裁质量。     

冲裁毛刺形成过程的有限元分析

采用弹塑性有限元法,运用有限元分析软件,对板料的冲裁过程进行了数值模拟,分析冲裁过程中毛刺的形成机理.设置了一系列的模具间隙、模具圆角参数,来分析模具间隙的增大和模具的磨损变化对毛刺形状的影响.模拟的结果与试验数据相对照,来预测冲裁断面的质量,优化工艺参数.     

Effects of process variables on V-die bending process of steel sheet

This investigation aims to clarify the process conditions of the V-die bending operation of steel sheet. It provides a model which predicts the correct punch load for bending and the precise final shape of products after unloading, in relation to the tensile properties of the material and the geometry of tools. The process variables are punch radius (R_p), die radius (R_d), punch width (W_p), punch speed (V_p), friction coefficient (μ), strain hardening exponent (n) and normal anisotropy (R).This investigation is carried out by performing some experiments and by finite-element simulation. Experiments determine the punch for bending for various process variables, such as punch radius, punch speed and lubrication, were carried out. As a result it was found that punch load increases as punch radius and punch speed increase or lubrication decreases.An elasto-plastic incremental finite-element computer code based on an updated Lagrangian formulation was developed to simulate the V-die bending process of sheet metal under the plane-strain condition. Isotropic and normal anisotropic material behavior was considered including nonlinear work hardening. A modified Coulomb’s friction law was introduced to treat the alternation of sliding–sticking state of friction at the contact interface. Simulation results, such as the punch load of bending and the bend angle of the bent part after unloading, are compared with experimental data; satisfactory agreement was observed. The simulation clearly demonstrates that the code to simulate V-die bending process was efficient.Simulations were made to evaluate the effects of die radius, punch width, strain hardening exponent and normal anisotropy on punch load of bending. The punch load for bending is smaller for materials with a larger strain hardening exponent. The effect of punch width on punch load is limited. The punch load decreases in the early stage and increases in the final stage of the bending process as the die radius increases. The influences of all of the process variables on the final bend angle of the bent parts of sheet after unloading were also evaluated. The effects of process variables except die radius on the bend angle after unloading are also limited. The angle of spring-back is greater for tools with larger die radius.     

Sheet metal bending optimisation using response surface method, numerical simulation and design of experiments

Bending is one of the processes frequently applied during manufacturing of automotive safety parts that are obtained by successive sequences of blanking and bending. This paper describes a 3D finite element model used for the prediction of punch load and the stress distribution during the wiping-die bending process. The numerical simulation has been modelled by means of elastic plastic theory coupled with Lemaître's damage approach. Numerical simulations were carried out by using the ABAQUS/Standard FE code, for a sufficient number of process parameters combinations, particularly the die radius and the gap between the punch and die. An algorithmic loop, programmed in the Script Language of ABAQUS, was developed in order to investigate the mechanical response of parts bent on a mechanical press for each combination of process parameters. The punch load and stress distribution can be predicted in view of optimising the values of the main parameters involved in the process. Finally, a response surface methodology (RSM) based on design of experiments (DOE) was used in order to minimise the maximum punch load during the bending operation. Numerical results showed the suitability of the proposed model for analysing the bending process. Associated plots are shown to be very efficient for a quick choice of the optimum values of the bending process parameters.     

An experimental analysis of effects of various material tool’s wear on burr during generator sheets blanking

Blanking is one of the most frequently used processes in sheet metal forming. Unlike other forming processes, such as stamping, blanking not only deforms the metal plastically to give the appropriate size and shape, but also ruptures the sheet metal in the desired zones. Among the others, blanking enables manufacturing of electric motor components, such as rotor or stator parts. The parts of the low power commutator motor of rotor and stator are made of generator sheets, which are really difficult to do from the machining point of view. The shock loads and high reaction of the sheet metal of separation surface to the punch surface are presented during the blanking process. In this paper, an investigation has been made to study the effects of punch–die clearance, tool materials, and tool coatings on the wear of blanking tools. In the paper, the feasibility analysis for various materials used for production of the tools for punching the generator sheets is presented.     

The application of abductive networks and FEM to predict the limiting drawing ratio in sheet metal forming processes

The deep drawing process, one of the sheet metal forming methods, is very useful in the industrial field because of its efficiency. The limiting drawing ratio (LDR) is affected by many material and process parameters, such as the strain-hardening exponent, the plastic strain ratio, friction and lubrication, the blank holder force, the presence of drawbeads, the profile radius of the die and punch, etc. In order to verify the finite element method (FEM) simulation results of the LDR, the experimental data are compared with the results of the current simulation. The influences of the process parameters such as the blank holder force, the profile radius of the die, the clearance between the punch and the die, and the friction coefficient on the LDR are also examined. The abductive network was then applied to synthesize the data sets obtained from the numerical simulation. The predicted results of the LDR from the prediction model are in good agreement with the results obtained from the FEM simulation. By employing the predictive model, it can provide valuable references to the prediction of the LDR under a suitable range of process parameters.     

Optimization of springback for AZ31 magnesium alloy sheets in the L-bending process based on the Taguchi method

Springback is a primary issue which is encountered during most sheet metal bending processes. Using the Taguchi method, this study investigates the springback of L-bending with a step in the die through simulation and experiments for AZ31 magnesium alloy sheets at different temperatures. The process parameters for bending springback in this study include: lower punch radius, die clearance, step height, and step distance; we use a Taguchi L9 orthogonal array to design the combinations for the experiments. The results of ANOVA analysis show that, for each bending temperature, the process parameters that affect springback occur in the following order: step height (greatest), lower punch radius (next), die clearance (smaller), and step distance (smallest). In addition, with the increase of the bending temperature, the angle of springback decreases. The optimal parameter combinations at each bending temperature from the signal-to-noise response are all the same, namely, a die radius of 2?mm, die clearance of 0.5?mm, step height of 0.1?mm, and step distance of 2?mm. When the bending temperatures are 100°C, 150°C, and 200°C, the angles after springback of the optimal experimental parameter combination are 91.06°, 90.63°, and 89.84°, respectively.     

Prediction of bend force and bend angle in air bending of electrogalvanized steel using response surface methodology

This paper presents the development of predictive models for bend force and final bend angle (after springback) in air bending of electrogalvanized steel sheet employing response surface methodology. The models are developed based on five-level half factorial central composite design of experiments with strain hardening exponent, coating thickness, die opening, die radius, punch radius, punch travel, punch velocity as input parameters and bend force and final bend angle as responses. The results obtained from the models are in good accord with the experimental results. The effects of individual parameters and their interactions on the responses have also been analyzed in this study.