Effect of welding current on strength and microstructure in resistance spot welding of AZ31 Mg alloy

In this paper, resistance spot welding were performed on lmm-thickness magnesium AZ31B plates. The effect of welding current on the microstructure and tensile shear force was investigated. It was found that the welding current governed the nugget growth, and the nugget could not form if current levels were insufficient. The nugget revealed a homogeneous, equiaxed, fine-grained structure, which consisted of non-equilibrium microstructure of α-phase dendrites surrounded by eutectic mixtures of α and β（ Mg17All2 ） in the grain boundaries. With increasing welding current, the size of grains in nugget would be more smaller and uniform, and the width of plastic rings would be larger. Tensile shear tests showed that tensile shear force of the joints increased with increasing welding current when the welding current was smaller than 17 000 A. The maximum tensile shear force was up to 1980 N.     

汽车焊装车间信息管理数据库的构建

在充分了解汽车焊装车间手工焊生产线工艺流程和特点的基础上,设计了生产过程信息管理系统的总体结构,确定了系统数据的模型和相互之间的关系.利用图形化编程语言LabView作为开发工具,开发了信息管理系统的操作界面,采用ODBC技术实现了操作界面与数据库之间的无缝链接.本系统的开发与实现能够提高企业的生产效率和产品质量,同时...     

Effects of modeling means on properties of monitoring models of spot welding quality

Analyzing and modeling the relation between monitoring information during welding and quality information of the joints is the foundation of monitoring resistance spot welding quality. According to the means of modeling, the known models can be divided into three large categories: single linear regression models, multiple linear regression models and multiple non-linear models. By modeling the relations between dynamic resistance information and welding quality parameters with different means, this paper analyzes effects of modeling means on performances of monitoring models of resistance spot welding quality. From the test results, the following conclusions can be drawn: By comparison with two other kinds of models, artificial neural network (ANN) model can describe non-linear and high coupling relationship between monitoring information and quality information more reasonably, improve performance of monitoring model remarkably, and make the estimated values of welding quality parameters more accurate and reliable.     

Effects of modeling means on properties of monitoring models o spot welding quality

Analyzing and modeling the relation between monitoring information during welding and quality information of the joints is the foundation of monitoring resistance spot welding quality.According to the means of modeling,the known models can be divided into three large categories:single linear regression models,multiple linear regression models and multiple nonlinear models.By modeling the relations between dynamic resistance information and welding quality parameters with different means,this paper analyzes effects of modeling means on performances of monitoring models of resistance spot welding quality. From the test results,the following conclustons can be drawn:By comparison with two other kinds of models,artificial neural network(ANN) model can describe non-linear and high coupling relationship between monitoring information and quality information more reasonably,improve performance of monitoring model remarkably,and make the estimated values of welding quality parameters more accurate and reliable.     

大规格电工触头柔性感应加热电源的设计

由于具有加热效率高、速度快、可控性好及易于实现自动化等众多优点,电磁感应加热已在低压电器大规格触头焊接行业得到了广泛的应用。但是目前国内生产使用的大规格触头感应加热电源大多采用连续加热模式,控制模式不够灵活,电流、功率靠电位器手动调节,时间控制只能精确到秒,电流和频率在加热过程中波动比较大,触头加热效果的可控性及重复性极差,焊接质量无法得到保证,不能满足自动化生产要求。针对目前存在的问题,设计了一种柔性感应加热电源,核心部分采用双32位单片机架构的控制器,电流和时间输出精度更高,能量输出可通过修改单片机程序任意调整,加热模式更加灵活。     

镁合金电阻点焊接头断裂行为的有限元分析

综合考虑熔核尺寸、工件翘曲变形、电极压痕等因素建立了三维弹塑性有限元模型,分析了镁合金电阻点焊接头的应力、应变场分布特点,以揭示焊点断裂产生的原因.结果显示,由于电阻点焊接头在受力时熔核是主要的承栽部位,在熔核边缘与板缝结合处由于几何非线性和材料的非线性将出现应力集中,这是点焊接头受力时最薄弱的环节,裂纹从这里萌生,沿熔核边缘高应力区扩展.镁合金点焊接头断裂均为沿焊点熔核的纽扣形撕裂,断裂属于韧性断裂.     

基于回归分析理论的点焊质量监测模型

以动态电阻与接头质量参数之间关系为例,用线性回归分析技术,系统地研究了点焊加热过程中的监测信息与点焊接头质量参数之间的一元和多元回归模型关系。结果表明：（1）各种回归模型总体线性关系经统计检验均为高显著,可以用于点焊接头质量监测;（2）一元回归模型的决定系数仅为0．15－0．33,多元回归模型的决定系数则可以提高到0．59－0．79,说明发展多参量综合监测技术是提高点焊质量监控精度的有效途径;（3）点焊过程监测信息与质量参数之间关系也含有较大的非线性,用线性模型去描述这样的关系导致模型误差的增加。     

人工神经元网络法估测点焊接头力学性能

采用一个神经网络估测器进行焊点力学性能无损在线分析。在此估测器中，经训练的神经元网络将用于描述动态电阻曲线与焊点力学性能的映射关系，试验结果证实了神经元网络用于这类应用场合的可行性和有效性。     

Optimization of parameters and study of joint microstructure of resistance spot welding of magnesium alloy

Experimental investigations on the DC spot welding of Mg alloy AZ31B are presented. Experiments are carried out to study the influence of spot welding parameters （ electrode force, welding heat input and welding time） on the tensile shear load and the diameter of nugget, based on an orthogonal test and analysis method. The optimum parameters are as follows： electrode force is 2 000 N, welding heat input is 80% and welding time is 6 cycles. The microstrueture of spot weld is single fine equiaxed crystals in the nugget, of which the structure is β-Mg17Al12 precipitated on α-Mg boundaries induced by nonequilibrium freezing. And the surface condition of the workpiece has great influence on the joint quality.     

An Artificial Neural Network for Estimating Sizes of Spot Welding Nuggets

0INTRoDUCTIONSizesofspotweldnuggetshaveadirectinfluenceonthestrengthandservicelifeofjoints,sothesizesofspotweldnuggetsareoftenusedtoevaluateweldingqualityinpro-duction.However,itisnoteasytomeasuresizesofspotweldnuggetsaccuratelyevenbyx-rayorothernon-destructivetests.Formassproduction,thesamplingdestructivetestisoftenusedtoobtaininformationofweldnuggets.Howeversamplingdestructivetestcannotguaranteethequalityofproductswhicharenotactuallytested,andalsoin-creasesthecostofproduction1'].Therefo…