电阻点焊质量Hopfield神经网络在线评估方法

目的 电阻点焊广泛应用于汽车、家电等领域,但目前少有准确的无损质量评价方法。为此,研究一种基于低碳钢板焊接功率信号的焊接质量在线评估方法,并探索利用该信号来评价电阻点焊焊点质量的可能性。方法 对焊接电流、电压信号进行测量和分析,研究功率信号表征焊接质量的可靠性,提出一种有效的模式特征提取方法,将动态功率信号转换为二值图像并用二值矩阵表征,该方法避免特征提取和选择,且尽可能保留焊点质量信息。通过拉剪试验将焊接样本分为6种不同的焊接等级,利用Hopfield关联记忆神经网络建立焊接质量分类器,将具有不同焊接质量水平的焊接样本模式特征矩阵记忆为稳定状态。结果 将焊接样本的模式特征矩阵输入分类器,通过Hopfield网络关联记忆将其收敛到最相似的稳定状态,最终锁定了稳定状态对应的焊接质量。60个测试样本中59个样本都可以被正确分类,该分类器的分类准确率达到98%。结论 分类性能试验结果表明,所提出的模式特征提取方法快速、有效,并能可靠地在线评估低碳钢板的焊接质量。     

焊接动态位移场的激光电子散斑法测量

为提供一种能够全场测量整个焊接过程动态位移场的工具,建立了激光电子散斑法测量系统.应用于实际TIG焊接过程中,获得了焊接位移场的散斑原始图像.利用自开发软件,对图像进行灰度变换和直方图均衡化处理后,采用频域同态滤波的方法对图像进行降噪滤波处理.经降噪、二值化、细化、平整、拟合、标定等一系列处理后,即可自动生成相对动态位移场.结果表明,激光电子散斑法能够胜任焊接动态位移场的测量,且具有非接触、测量精度高、对环境的防震要求低、可在明光下操作、能进行全场测量的特点.     

On-line monitoring method for electrode invalidation during spot welding of zinc-coated steel

In the process of spot welding of zinc-coated steel, because of the existence of zinc coat, the electrode invalidation is accelerated greatly, which causes unacceptable welding quality. A collecting system is developed with a C8051F020 microcomputer as the controlling core, which is used to collect such parameters as welding current, supply voltage, dynamic resistance, etc. Through the comprehensive processing, the whole variety trends of those parameters are obtained. Finally, an on-line monitoring method is given through the relationship between electrode wear and welding parameters, which is valuable for the industrial production.     

A prototype fuzzy resistance spot welding system

In assembly automation, the need to perform on-line quality monitoring and to provide near real-lime inspection of resistance spot welds, has attained unsurpassed importance in industries. This paper describes the development of a prototype fuzzy control system for a two-stage resistance spot welding machine with potential of being incorporated into an automation line. It encompasses a new approach aimed at providing simultaneous control of more than two major welding parameters for achieving consistent quality spot welds by assessing the condition of the heat affected zone created. The prototype system, developed in C language, comes with a decision making mechanism and a quick search mechanism. Its rule-base contains a total of 125 heuristic control rules derived from literature reviews and interviews with experts and through experiments. The various factors affecting the quality of spot welds are outlined in the paper. The correlation between spot weld quality and welding parameters were examined using the Taguchi technique. Details of the prototype system are described and the results of the experiments conducted on the system are discussed.     

船体结构钢及焊接材料数据库应用系统设计开发

为了解决结构钢及焊接材料数据的有效存储及高效利用问题,使用SQL Server作为后台数据仓库,VB作系统开发,ODBC数据源作为连接技术,设计开发了船体结构钢及焊接材料数据库应用系统.系统具有结构钢及焊接材料信息查询、标准及报告查询等四大功能模块,并以结构钢配套焊条为例,通过性能预测智慧框架和神经网络模型构建、神经网...     

MODELLING AND OPTIMIZING OF A MIG WELDING PROCESS—A CASE STUDY USING EXPERIMENTAL DESIGNS AND NEURAL NETWORKS

This paper describes an application of an integrated method using experimental designs and neural network technologies for modelling and optimizing a metal inert gas (MIG) welding process. To achieve optimization, the process parameters must be adjusted in such a way that the deviations from target are minimized while the robustness to noise and to process fluctuations are maximized. This new method consists of an experiment reference template for designing and collecting training data samples, and a parallel distributed computational adaptive neural network system to provide a powerful tool for data modelling and empirical investigations. The relevant data is established using experimental design methods and highlighted in the case study. An adaptive GaRBF neural network is used to approximate the stochastically non-linear dynamics of the welding process to optimize the basic welding parameters. The neural network is trained with welding experimental data, tested and compared in an actual welding environment in terms of its ability to determine weld quality. The results show that the proposed adaptive neural network is capable of mapping the complex relationships between the welding parameters and the corresponding output weld quality. The implementation for this case study was carried out using a ‘semi-automatic’ welding facility, to mass weld a 20″ × 0.438″ pin/box onto a 20″ × 0.5″ × 37′ pipe (tubular drilling products), in an actual workshop which makes oilfield equipment. The entire range of welding combinations that might be experienced during actual welding operations is included to study the weld quality. © 1997 by John Wiley & Sons, Ltd.     

光纤电焊电流测量技术研究

针对直流逆变电阻焊机焊接电流精确测量的需求,提出基于光纤电流传感技术的焊接电流测量方法。建立了光纤电流传感器闭环检测系统动态模型,通过优化系统的前向增益,提升了传感器响应速度和带宽。仿真和实验结果表明:传感器的上升时间约为4.1 μs,在DC~30kHz范围内幅频特性衰减小于0.3%。基于该动态模型计算传感器对焊接电流纹波分量的响应,仿真结果表明:系统的动态跟踪能力可满足对纹波电流的测量需求。利用等安匝法对光纤电流传感器进行校准,在直流5~50kA范围内,传感器的测量误差优于±0.05%。现场实验结果证明了光纤电流传感器用于直流逆变焊接电流测量及电焊电流测试仪现场校准的可行性。     

Pattern Recognition of Weld Defects in Preprocessed TOFD Signals Using Linear Classifiers

The TOFD (Time of Flight Diffraction) technique is being widely used for automatic weld inspection, especially in the petrochemical industry, where welding quality is essential to avoid productivity losses. Although it provides high speed inspection, high sizing reliability and low rate of false defect indications, the classification of defects using ultrasound signals generated by the TOFD technique is still frequently questioned, because it depends heavily on the knowledge and experience of the operator. However, the use of computational tools for signal preprocessing and pattern recognition, such as the artificial neural networks, improves the classification reliability of defects detected by this technique. In this present work, three kinds of defects: lack of fusion (LF), lack of penetration (LP) and porosity (PO) were inserted into the specimens durin the welding process, generating pattern defects. The position, type and dimension of each inserted defect were recorded using conventional ultrasonic and radiographic techniques. The Fourier Transform and Wavelet Transform were used for preprocessing A-scan signals acquired during weld inspection by TOFD technique. This study was able to show the versatility of Wavelet Transform to preprocess these kinds of signals, since the correct scale in Continuous Wavelet Transform had been selected to supply a neural network. Hierarchical linear classifiers were implemented into the neural network in order to distinguish the main defects in welded joints detected by the TOFD technique. The results show the good success rate of welding defect recognition in preprocessed TOFD signals, mainly using Wavelet Transform. On the whole, the results obtained were very promising and could give relevant contributions to the development of an automatic system of detection and classification of welding defects inspected by the TOFD technique.     

电阻点焊质量检测技术研究现状

电阻点焊过程由于受到各种因素的影响,熔核区域容易出现裂纹、缩孔、未熔合等缺陷,焊点质量直接影响焊接部件的使用寿命,因此对焊点的缺陷检测与质量评定非常重要.对电阻点焊原理进行概述,总结了电阻点焊质量检测技术最新研究成果及应用,分析了焊接过程参数监控方法、焊后无损检测方法的检测机理、质量评定方法及其在实际应用中的优缺点,对...     

Resistance Element Welding of 6061 Aluminum Alloy to Uncoated 22MnMoB Boron Steel

A novel resistance element welding technology was applied to join 6061 Al alloy and uncoated 22MnMoB boron steel. To conduct the resistance element welding process, a technological hole was drilled in the Al sheet into which a Q235 steel rivet was inserted. Resistance spot welding was carried out at the rivet. The mechanical properties, fracture morphology, nugget formation process, dynamic resistance, microstructure, and hardness distribution of the resistance element welding were investigated. Traditional resistance spot weld joints were also prepared for comparison. Resistance spot welding could barely join Al 6061 and boron steel, and had a maximum tensile shear force of less than 1000 N. Novel resistance element welding could join the metals reliably with a maximum tensile shear force of over 7000 N and a relatively high toughness. Nugget formed at the interface of rivet and steel acted as loading position, and IMC interlayer connected rivet and aluminum.     

图像处理在自动焊接中的应用和展望

图像处理技术在自动焊接领域的应用已引起国内外学者的广泛重视。通过图像传感技术获取焊接熔池直观丰富的图像信息，使用高效的图像处理算法，提取焊接熔池的特征信息，用以实现自动焊接过程质量实时传感与控制。本文综合论述了图像处理技术在自动焊接中的应用原理、数字图像的采集方法、数字图像的特征信息定义、广义数字图像处理技术及其对自动化焊接理论研究和实践应用的推动作用。通过总结图像处理技术的研究和应用现状，综合分析了图像处理技术在现代焊接技术中发展和应用的前景。     

Explosion of a combustion chamber shell

This paper describes an investigation of the explosion of a combustion chamber shell in an aeroengine. Metallographic analysis, mechanical calculation and fatigue life estimation have been performed to determine failure causes and to make a proposal for preventive measure. The analytical results show that the poor quality of the roll welding seam is the fundamental cause of failure added to which a crack in the seam had not been discovered during a second overhaul. The effective design improvement is argon arc welding instead of roll welding in fabricating new shells. The effective preventive measures for old shells are to raise the strength of the seam by additional melt welding at overhaul, and to perform rigorous nondestruction inspection.     

Robot arc welding task sequencing using genetic algorithms

This paper addresses welding task sequencing for robot arc welding process planning. Although welding task sequencing is an essential step in welding process planning, it has been considered through empirical knowledge, rather than a systematic approach. Thus, an effective task sequencing method for robot arc welding is required. Welding operations can be classified by the number of weldlines and layers. Genetic algorithms are applied to tackle those welding task sequencing problems in productivity and welding quality aspects. A genetic algorithm for the Traveling Salesman Problem (TSP) is utilized to determine welding task sequencing for a multiweldline-singlepass problem. Further, welding task sequencing for multiweldline-multipass welding is investigated and appropriate genetic algorithms are introduced. A random key genetic algorithm is presented to solve multi-robot welding task sequencing: mutliweldline with multiple robots. Finally, the genetic algorithms are implemented for the welding task sequencing of three-dimensional weld plate assemblies. Various simulation tests for a welded structure are performed to find the combination of genetic algorithm parameters suitable to weld sequencing problems and to verify the quality of genetic algorithm solutions. Robot operations for weld sequences are simulated graphically using the robot simulation software IGRIP.     

Yield management with downward substitution and uncertainty demand in semiconductor manufacturing

Motivated by the high yield variability in the semiconductor industry where the quality of the end products is uncertain and is graded into one of several quality levels according to performance before being shipped. We consider a dynamic multi-period yield management problem of a two-stage make-to-stock system faced by a semiconductor manufacturing firm. In the first stage, the firm invests in raw material before any actual demand is known, and produces multiple types of products with random yield rates because of the presence of randomness in the process. In the second stage, products are classified into different classes by quality, and allocated in a number of sequential periods. Demand is also random and can be classified into multiple classes corresponding to product levels. Demands can be upgraded when one type of product has been depleted. This paper presents a multi-period, multi-product, downward substitution model to determine the optimal production input and allocation of the different products to satisfy demands. The production and allocation problem is modelled as a stochastic dynamic program in which the objective is to maximise the profit of the firm. We show that the simple one step upgrade substitution policy is optimal, and the objective function is concave in production input. An iterative algorithm is designed to find the optimal production input and numerical experiments are used to illustrate its effectiveness.     

汽车门框上条角焊焊接质量研究及工艺参数优化

目的对汽车门框上条角焊进行质量研究,得到最优的工艺参数。方法通过对门框上条角焊过程工艺参数进行分析,设计了三因素四水平的16组正交试验方案;提出了焊缝尺寸数据获取的方法,获得焊接试验余高和熔深数据。利用Matlab建立了焊缝余高和熔深的BP神经网络预测模型,结合响应面优化算法实现工艺参数的优化。结果得到了焊接最优工艺参数,焊接效果满足汽车门框上条的要求。结论通过质量研究及工艺参数优化,得到了焊接工艺参数对焊接质量的影响规律及最优工艺参数,为汽车门框上条角焊质量提高和工艺优化提供了理论基础。     

An Experimental Study of Resistance Welding of Carbon Fibre Fabric Reinforced Polyetherimide (CF Fabric/PEI) Composite Material

This paper presents an experimental investigation of resistance welding of carbon fibre fabric reinforced polyetherimide composites (CF fabric/PEI). The heating elements were made from a single CF fabric/PEI prepreg sheet with neat PEI films co-moulded to both surfaces. Welding was conducted on a welding area of 25 mm × 12 mm. The quality of the welded specimens was studied using a non-destructive evaluation technique (C-scan) as well as a mechanical test (lap shear strength). The relationships between input power, input energy, welding time and consolidation pressure were studied. Experimental results indicated that sufficient joining was obtained at a power level from 80 to 160 kW/m2, under an initial welding pressure of 0.15 to 0.40 MPa. The maximum lap shear strength achieved through resistance welding was equivalent to that of the compression moulded benchmark. The fracture surfaces of welded specimens showed mostly cohesive-failure or intralaminar failure. An optimum processing window is proposed for the resistance welding of CF fabric/PEI composite system.     

铂电阻传感器引线与不等直径异质多股导线连接新技术及焊接装置

目的开发一种能实现多股导线与微细丝稳定、可靠连接的新方法及相关装置。方法选用直径为0.2mm、材料为镍丝的铂电阻引线与直径约0.5 mm、材料为铜丝的多股导线进行实验,分别用常规电阻钎焊方法和本研究提出的精密电阻钎焊方法进行焊接。开展焊接工艺实验,研究工艺参数对焊接成形的影响,并获得优化工艺参数;用精密拉伸实验机对采用不同方法和不同工艺参数获得的焊接接头进行拉剪力测试,研究焊接方法和工艺条件对接头拉剪力的影响规律,对不同条件下获得的焊接接头的微观组织结构进行分析,研究其与工艺的相关性。结果采用常规焊接方法得到的焊接接头,平均抗拉力为21 N,强度系数为84%,但缺陷过多,成形差。采用精密电阻钎焊方法得到的焊接接头,平均抗拉力为23 N,强度系数为92%,表面成形及性能均达到要求。结论提出的精密电阻钎焊方法,操作简单,焊接质量稳定,焊接效率高,实现了铂电阻引线和多股导线的良好连接。     

含稀土1Cr18Ni9Ti不锈钢焊接接头耐腐蚀性能的电化学研究

通过焊条药皮向１Ｃｒ１８Ｎｉ９Ｔｉ不锈钢焊缝中过渡稀土,用高温电化学方法研究了稀土对焊缝耐内蒙古天然碱苛化烧碱腐蚀性能的影响。结果表明：采用适量的焊条药皮配方和焊接工艺可使稀土元素过渡到焊缝金属中,适量稀土元素改变了不锈钢焊接接头阳极极化曲线的极化度,从而改善了不锈钢材料焊接接头的耐蚀性。     

Effect of ultrasonic welding parameters on microstructure and mechanical properties of dissimilar joints

Ultrasonic spot welding has received significant attention during past few years due to their suitable applications in comparison to conventional fusion welding techniques. Fusion welding of dissimilar Aluminum and Stainless steel alloys is always a challenging task because of poor control on grain size and formation of undesirable brittle intermetallic compounds in the weld metal, which have deleterious effect on mechanical properties. In the past, welding of dissimilar alloys has been performed using electron beam welding, laser beam welding and friction stir spot welding, resistance spot welding, etc. However, little work has been reported on dissimilar welding of Aluminum and Stainless steel alloys using ultrasonic spot welding. The objective of the present work is to optimize ultrasonic spot welding parameters for joining 3003 Aluminum alloy with 304 Stainless steel. Welding was performed at various clamping pressures (i.e. 30, 40, 50 and 60 psi) and energy levels for investigating its effect on microstructure, mechanical properties and bond quality of the weld. Different levels of weld quality i.e. ‘under weld’, ‘good weld’ and ‘overweld’ were identified at various welding parameters using physical attributes. The weld specimens prepared with energy 125 and 150 J showed the maximum bond strength and were rated as “good” weld. It was also revealed that for a good quality weld, the maximum tensile strength is achieved once a reasonable amount of bond density and material thinning (required for the formation of metallurgical bonds) is attained.     

In-situ cracking for nondestructive inspection process validation

ork at the Idaho National Engineering and Environmental Laboratory (INEEL) includes efforts to weld steel storage containers. Producing repeatable high quality welds and assuring weld quality is paramount to this work. The nondestructive examination (NDE) method used to measure weld quality is the magnetic particle testing (MT) process since the containers are fabricated from mild steel. A paradox occurred during the initial mockup welding and inspection system demonstrations. Since the welding was flawless, the semi-automatic remote MT system had no defects to find. The MT system was calibrated, as per the welding code, with calibration blocks, but it never demonstrated that it worked during the demonstration because of the flawless welds. To validate the MT system during the mockup welding demonstration, in-situ defects were artificially generated. Two-in. (5.1-cm) long copper wire segments were placed into the weld groove joint and consumed into the weld metal during welding. This in-situ crack generation technique provided physical defects for the inspector/regulator to observe, which then validated the inspection system.