基于神经网络的316L不锈钢激光焊焊缝形貌预测

在316L不锈钢的激光焊接过程中,其焊接工艺参数直接影响焊缝的形貌,建立焊接工艺参数与焊缝几何形状之间的关系对于优化焊接工艺参数,降低焊接成本非常重要. 根据316L不锈钢焊缝二维不光滑轮廓形貌特点,采用分段函数思想,分别使用Hermite插值和最小二乘拟合的方法描述焊缝轮廓,构建广义回归神经网络焊缝二维形貌预测模型. 结果表明,采用Hermite插值的方法能够获得更准确的焊缝形貌,其平均相对误差为?3.49%. 该模型为316L不锈钢激光焊焊缝预测提供一种有效方法.     

Selection of optimal welding condition for GTA pulse welding in root-pass of V-groove butt joint

In the manufacture of high-quality welds or pipeline, a full-penetration weld has to be made along the weld joint. Therefore, root-pass welding is very important, and its conditions have to be selected carefully. In this study, an experimental method for the selection of optimal welding conditions is proposed for gas tungsten arc (GTA) pulse welding in the root pass which is done along the V-grooved butt-weld joint. This method uses response surface analysis in which the width and height of back bead are chosen as quality variables of the weld. The overall desirability function, which is the combined desirability function for the two quality variables, is used as the objective function to obtain the optimal welding conditions. In our experiments, the target values of back bead width and height are 4 mm and zero, respectively, for a V-grooved butt-weld joint of a 7-mm-thick steel plate. The optimal welding conditions could determine the back bead profile (bead width and height) as 4.012 mm and 0.02 mm. From a series of welding tests, it was revealed that a uniform and full-penetration weld bead can be obtained by adopting the optimal welding conditions determined according to the proposed method.     

Study of Laser Lap Welding of SUS301L Austenitic Stainless Steel Using Optimal Design Method

This paper presents an experimental design approach to process parameter optimization for the laser lap welding of SUS301L austenitic stainless steels using Nd:YAG laser in order to reduce the welding deformations of the back of the welding seams while ensuring mechanical properties of welding joints.To determine the optimal laser-welding parameters,a set of mathematical models were developed relating welding parameters to each of the weld characteristics.These were validated both statistically and experimentally.In order to reduce experimental error and the number of specimens,the part of orthogonal experiments were used in this study.The quality criteria set for the weld to determine optimal parameters were the maximization of weld width and the minimization of weld depth.Laser power,welding speed,the laser irradiation angle,the focused distance and shield gas of 3.5kW,7.0m/min,70°,0mm and N2 with the flow of 30L/min,respectively,with a fiber diameter of 600μm were identified as the optimal set of process parameters.     

U型钢机器人快速MAG焊接工艺研究

采用机器人对U型钢试件进行快速MAG焊接工艺试验,通过对立缝焊接过程电流、电压、速度等工艺参数及摆动幅度、摆动频率、两侧壁停留时间等机器人运动参数对焊接过程及焊后结果的影响进行分析,结合立角焊接过程熔池受力特性对焊接过程的影响,配合平角及立向弯角焊接,形成一套连贯有效的U型钢快速MAG焊接工艺并能用应用于实际产品。结果表明,在保证焊接稳定性的前提下,焊接电流、电弧电压适当减小,焊接速度适当增加,摆动参数适当减小,有利于焊后焊缝良好成形及效率提高;最终工艺应用在产品上,降本增效,满足生产质效需求。     

Numerical study of fillet weld leg height of sleeve repair welding for in-service pipeline

This paper presents a mechanical calculation and numerical simulation of the fillet weld of sleeve repair.The mechanical analysis based on the yield criteria is performed to obtain the minimum value of the fillet weld leg height to ensure the strength and loadbearing capacity of the weld. Within the framework of numerical simulation,the parameters of double ellipsoid heat source are determined by fitting method and the simulated molten pool morphology agrees well with the practical weld. Finite element models with various weld leg height are performed to predict the distribution and magnitude of the deformation and stress. The simulation takes into account thermal,metallurgical and mechanical factors,and the maximum value of the fillet weld leg height is obtained based on the magnitude of the deformation and stress.The mechanical calculation and numerical simulation results show that 1.2-2 times wall thickness is an optimal range of fillet weld leg height. And reasonable parameters of sleeve repair for in-service welding are provided for engineering field,which can improve the service life of the weld and production efficiency.     

2060铝锂合金扫描填丝焊接工艺

针对铝锂合金焊后易产生气孔、抗拉强度低的缺点,提出“∞”形激光扫描填丝焊接工艺方法,以2 mm厚2060铝锂合金为研究对象开展对接焊接试验研究,探究激光扫描填丝焊接方法对铝锂合金焊接缺陷抑制作用. 借助高速相机摄像系统,探究了激光扫描填丝焊接工艺下熔池的动态演变过程,同时探究了扫描参数对焊缝气孔的影响规律及扫描填丝工艺对气孔的抑制机理. 采用曲面响应统计方法探究工艺参数对抗拉强度的影响,并给出工艺参数组合与抗拉强度的定量关系及最优参数组合,焊接接头最大抗拉强度可达382 MPa,为母材的76.4%. 结果表明,“∞”形激光扫描填丝焊接工艺下熔池流动平稳,小孔喷发强度较弱且呈现出周期性;“∞”形激光扫描填丝焊接工艺可以有效抑制焊缝气孔,提高铝锂合金焊接质量.     

镀锌钢GMAW焊缝成形特征与焊枪方向同步实时检测

针对基于激光视觉传感的镀锌钢薄板搭接GMAW特点,提出了一种搭接接头焊缝成形全位置特征与焊枪方向同步实时检测方法. 该方法利用激光视觉系统同步检测焊缝与焊丝信息,采用尺度不变特征变换与方向特征检测算法,同步实时获取焊缝轮廓与焊丝方向;采用Harris角点检测算法实现焊缝轮廓特征点识别;针对接头焊缝面积偏小的特点,采用线性插值方法实现了焊缝高度与宽度的全位置、焊缝面积的亚像素级测量,并基于零、一阶矩实现了焊缝重心检测. 结果表明,该算法适应性强、测精度高,为基于焊枪姿态和焊接过程参数优化在线控制焊缝成形提供了依据.     

Correlation between laser-wire distance and Nd：YAG laser ＋ P-GMA hybrid welding heat input parameters

In laser+P-GMA hybrid welding,laser-wire distance is an important parameter to describe the distance from laser spot to the center of the pulsed gas metal arc.The experiments results show that the optimal laser-wire distance with the deepest weld penetration increases with welding current and laser power being increased and decreases with welding speed being increased.Welding current,laser power and welding speed determine the hybrid welding heat input in laser+arc hybrid welding process,so there is a correlation between the optimal laser-wire distance and the hybrid heat input welding parameters for the deepest weld penetration: the optimal laser-wire distance increases with the heat input being increased.The positive correlation between the optimal laser-wire distance and the hybrid welding heat input is induced by the characteristics of the limited influence of P-GMA welding process on laser transmission and the dependence of weld penetration of hybrid welding on laser power.     

Effect of Ti content on TiN morphology,microstructure and toughness in coarse‐grained heat affected zone of Ti‐containing steels

It is well known that weld distortion, which has a negative influence on material properties, structural fabricability and structural integrity, should be controlled appropriately. There are many methods to control or reduce weld distortion, but most of them involve some costly process in addition to welding. In-process control of weld distortion becomes more preferable than post-welding process or other methods, when manufacturing efficiency is considered. In recent years, in-process control welding by additional cooling has been proposed as one of techniques for reducing weld distortion and partially applied for thin-plate structure in industries. However, the effectiveness of additional cooling method has not yet been fully clarified. In this study, the effectiveness of additional cooling method and appropriate cooling condition for effective reduction in weld distortion are investigated by three-dimensional thermal elastic–plastic analysis. In addition, the effect of locally cooled temperature distribution on generation behaviour of plastic strain is discussed. As a result, it is concluded that the effectiveness of additional cooling and appropriate cooling condition for reduction in weld distortion are dependent on weld distortion under consideration and welding conditions. Especially, it is necessary for reduction in weld distortion to set the cooling torch at the appropriate position. For example, in order to reduce angular distortion effectively, the appropriate cooling position is dependent on the mechanical melting length during welding.     

基于改进MULTIMOORA方法的PCCP焊接工艺参数优选

焊接作为预应力钢筒混凝土管(prestressed concrete cylinder pipe, PCCP)钢筒加工的主要技术,焊接工艺控制参数直接影响焊缝质量,进而影响PCCP应用性能. 故确定PCCP钢筒最优焊接工艺参数尤为重要,基于现场采集数据和改进MULTIMOORA方法,以焊缝特征指标为评价依据,对螺旋焊接工艺进行综合优选. 首先获取并整理各指标数据,将各指标转化为多属性决策问题,通过评价指标数据,定义权重因子用来分配优先级,量化指标,根据优化原则对方案进行排序,过程采用OWA算子和熵权法消除主观评价值中极端值影响,得到指标综合权重,进行决策排序优选,最后利用占优理论对焊接控制工艺技术参数进行最终评价. 结果表明,PCCP钢筒最优焊接工艺参数为焊接电流340 A、电弧电压为24 V、焊接速度为10.81 mm/s,以期为PCCP钢筒焊接工艺提供技术参考.     

Supervised descent method for weld pool boundary extraction during fiber laser welding process

In order to obtain a high-quality weld during the laser welding process, extracting the characteristic parameters of weld pool is an important issue for automated welding. In this paper, the type 304 austenitic stainless steel is welded by a 5kW high-power fiber laser and a high-speed camera is employed to capture the topside images of weld pools. Then we propose a robust visual-detection approach for the molten pool based on the supervised descent method. It provides an elegant framework for representing the outline of a weld pool and is especially efficient for weld pool detection in the presence of strong uncertainties and disturbances. Finally, welding experimental results verified that the proposed approach can extract the weld pool boundary accurately, which will lay a solid foundation for controlling the weld quality of fiber laser welding process.     

Neural network modeling for weld shape process of P-GMAW

Weld shape control is a fundamental issue in automatic welding. In this paper, a double side visual system is established for pulsed gas metal arc welding （ P-GMAW） , and both topside and backside weld pool images can be captured and stored continuously in real time. By analyzing the weld shape regulation with the molten metal volume, some topside weld pool characterized parameters （WPCPs） are proposed for determining penetration in butt welding of thin mild steel. Moreover, some BP network models are established to predict backside Weld pool width with welding parameters and WPCPs as inputs.     

薄板高强铝合金LY12CZ焊接工艺参数的优化

从力学角度出发，通过调整焊接温度场，控制焊缝及近缝区的应力应变发展，实现了高强铝合金LY12CZ薄板的低应力少变形无热裂焊接。运用正交试验设计来安排试验、筛选因子，并用一次回归正交设计调优运算优化因子的匹配，找到了影响铝合金薄板焊接变形的主要因子和最佳工艺参数匹配，揭示了主要工艺参数对减小变形效果的影响规律。     

Online quality inspection of resistance spot welded joint based on electrode indentation using servo gun

Abstract

Resistance spot welding is one of the major joining techniques widely used for car body assembly. Weld quality may significantly influence the durability and reliability of the automobile body. Automotive manufacturers often rely on destructive testing and monitoring variables which indirectly reflected weld quality to assess the weld quality and control the welding process. However, these approaches have inherent limitations and are difficult to be implemented in plant environments. Therefore, it is imperative to develop an online inspection method to evaluate weld quality. In the present study, a method of producing a series of substantially uniform spot welds between two metal parts using a servomotor driven movable electrode and an axially opposing fixed electrode is proposed. The indentation in the workpiece surface is suitably measured by the displacement of the movable electrode as it applies an electrode force and welding current is passed through the weld site of the workpiece. The optimal indentation range is determined by peel test and metallographic examinations with respect to various sheet gages and grades. Consequently, online weld quality inspection results are achieved based on developed optimal indentation range.     

CuNiCrSi铜合金搅拌摩擦焊工艺参数与组织性能分析

为了探究CuNiCrSi铜合金搅拌摩擦焊工艺参数与组织性能，采用正交试验法对工艺参数进行优化，并研究了焊缝的组织性能及材料流动性. 结果表明，焊接速度是对焊接过程影响最为显著的因素，试验得到焊接最佳工艺参数组合，在最优参数组合下焊缝的抗拉强度为491.4 MPa，达到母材抗拉强度的84.7%. 当焊接速度过大时会在焊缝的前进侧出现隧道型缺陷；材料的流动可以分为四部分；前进侧材料流动情况比返回侧复杂；焊接速度过小时表面会出现毛刺；母材区粗大的粒子为铬和硅的偏聚物，而镍无偏聚均匀地分布在材料中；焊核区晶粒随着焊接速度的增加而变小. 最优参数下焊核区晶粒虽然细小均匀，但硬度却比母材区低.     

Modeling, optimization and classification of weld quality in tungsten inert gas welding

In this paper, a neural network is used to construct the relationships between welding process parameters and weld pool geometry in tungsten inert gas (TIG) welding. An optimization algorithm called simulated annealing (SA) is then applied to the network for searching the process parameters with an optimal weld pool geometry. Finally, the quality of aluminum welds based on the weld pool geometry is classified and verified by a fuzzy clustering technique. Experimental results are presented to explain the proposed approach.     

气体熔池耦合活性TIG焊方法

提出了一种新型活性TIG焊方法——气体熔池耦合活性TIG焊,即GPCA-TIG焊.该焊接方法将气体分两层流动,内层气体采用惰性气体起到保护熔池的作用;外层气体则为含活性元素O的气体,将活性元素O引入熔池金属,达到增加熔深的目的.文中以SUS304不锈钢为焊接母材,研究了GPCA-TIG焊接法对焊接电弧及焊缝成形的作用,以及该方法主要工艺参数对焊缝熔深和深宽比的影响.结果表明,在相同参数下,与常规TIG焊方法相比,GPCA-TIG焊可不开坡口一次性焊透8 mm不锈钢板,焊接效率明显提高.同时采用该方法,可以有效避免钨极的氧化烧损.     

坡口偏差厚板机器人多道焊接方法

厚板构件在工程机械及重工行业等领域应用广泛,但许多工况的坡口因为加工和组对等原因存在较大偏差. 针对工件加工和组对出现的坡口间隙不一致、坡口角度偏差和错边等三种典型问题,分别给出了应对方法和修正措施. 通过焊接摆动参数调整补偿坡口间隙不一致时造成的偏差,采用焊接参数和摆动参数调节实施联合补偿坡口角度偏差带来的影响,以焊道数量调整和焊接电流周期变化补偿坡口组对错边情况. 采用这些措施,利用焊接机器人进行坡口偏差工况焊接试验. 焊后接头填充饱满,焊缝外观无明显缺陷. 焊缝截面观察焊道排列整齐有序,未出现内部缺陷. 结果表明,采用坡口偏差修正方法拓宽了机器人厚板焊接对坡口偏差的适应性,为机器人厚板焊接现场施工提供基础数据.     

铸铁同质焊缝组织判据研究

本文通过实测多种条件下补焊灰口铸铁的热循环曲线,系统分析了各种焊接工艺条件采用同质铸铁焊条所焊铸铁焊缝及其半熔化区的白口组织的形成和分布的影响规律,首次提出了判断白口形成的冷速判据－ｔ和ｔ８／５,为实际焊接灰口铸铁防止白组织提供了简便可行的方法。     

基于神经网络的焊机参数预测方法

针对脉冲MIG焊参数众多，不易调节的特点，提出了一种基于神经网络的焊机参数预测方法. 该方法采用LM(levenberg-marquarlt)算法建立了焊机参数的BP(back propagation)神经网络模型，充分利用已知的理想数据对网络进行训练，实现了焊接过程中任一给定焊接电流状态下焊机输出参数的预测；利用焊接参数的预测值分别对单、双脉冲MIG焊进行了试焊. 结果表明，基于神经网络的焊机参数预测方法精度较高，焊接过程稳定，焊缝成形美观，能够实现良好的一元化调节.