An approach of artificial neural network to robotic welding process modelling

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Modeling of welded bead profile for rapid prototyping by robotic MAG welding

As a deposition technology, robotic metal active gas(MAG) welding has shown new promise for rapid prototyping (RP) of metallic parts. During the process of metal forming using robotic MAG welding, sectional profile of single-pass welded bead is critical to formed accuracy and quality of metal pans. In this paper, the experiments of single-pass welded bead for rapid prototyping using robotic MAG welding were carried out. The effect of some edge detectors on the cross-sectional edge of welded bead was discussed and curve fitting was applied using leat square fitting. Consequently, the mathematical model of welded bead profile was developed. The experimental results show that good shape could be obtained under suitable welding parameters. Canny operawr is suitable to edge detection of welded bead profile, and the mathematical model of welded bead profile developed is approximately parabola.     

Sensitivity analysis for process parameters in GMA welding processes using a factorial design method

Generally, the quality of a weld joint is strongly influenced by process parameters during the welding process. In order to achieve high quality welds, mathematical models that can predict the bead geometry and shape to accomplish the desired mechanical properties of the weldment should be developed. This paper focuses on the development of mathematical models for the selection of process parameters and the prediction of bead geometry (bead width, bead height and penetration) in robotic GMA (Gas Metal Arc) welding. Factorial design can be employed as a guide for optimization of process parameters. Three factors were incorporated into the factorial model: arc current, welding voltage and welding speed. A sensitivity analysis has been conducted and compared the relative impact of three process parameters on bead geometry in order to verify the measurement errors on the values of the uncertainty in estimated parameters. The results obtained show that developed mathematical models can be applied to estimate the effectiveness of process parameters for a given bead geometry, and a change of process parameters affects the bead width and bead height more strongly than penetration relatively.     

Sensitivity model for prediction of bead geometry in underwater wet flux cored arc welding

To investigate influence of welding parameters on weld bead geometry in underwater wet flux cored arc welding (FCAW), orthogonal experiments of underwater wet FCAW were conducted in the hyperbaric chamber at water depth from 0.2 m to 60 m and mathematical models were developed by multiple curvilinear regression method from the experimental data. Sensitivity analysis was then performed to predict the bead geometry and evaluate the influence of welding parameters. The results reveal that water depth has a greater influence on bead geometry than other welding parameters when welding at a water depth less than 10 m. At a water depth deeper than 10 m, a change in travel speed affects the bead geometry more strongly than other welding parameters.     

Optimisation of hybrid tandem metal active gas welding using Gaussian process regression

In this paper, an additional filler wire with opposite polarity was inserted in tandem flux cored arc welding process to increase the welding speed and deposition rate. In this hybrid welding, the optimisation of welding parameters is required to improve the bead geometry which directly indicates the welding quality. However, the correlation between the parameters and the bead geometry is hard to identify, so the process parameters are usually selected intuitively by the experienced engineers. Therefore, welding process modelling is constructed with the Gaussian process regression model, and parameter optimisation is performed with sequential quadratic programming optimisation algorithm. The proposed modelling optimisation process is verified by performing the welding experiment using the parameters that are optimised by the proposed process.     

Sensitivity analysis of submerged arc welding process parameters

Selection of process parameters has great influence on the quality of a welded connection. Mathematical modelling can be utilized in the optimization and control procedure of parameters. Rather than the well-known effects of main process parameters, this study focuses on the sensitivity analysis of parameters and fine tuning requirements of the parameters for optimum weld bead geometry. Changeable process parameters such as welding current, welding voltage and welding speed are used as design variables. The objective function is formed using width, height and penetration of the weld bead. Experimental part of the study is based on three level factorial design of three process parameters. In order to investigate the effects of input (process) parameters on output parameters, which determine the weld bead geometry, a mathematical model is constructed by using multiple curvilinear regression analysis. After carrying out a sensitivity analysis using developed empirical equations, relative effects of input parameters on output parameters are obtained. Effects of all three design parameters on the bead width and bead height show that even small changes in these parameters play an important role in the quality of welding operation. The results also reveal that the penetration is almost non-sensitive to the variations in voltage and speed.     

回火焊道焊接技术中焊接接头几何尺寸影响因素的分析

试验针对核电压力容器用钢SA508-3钢进行,采用TGS-56焊丝和TIG焊,在100 mm厚SA508-3钢板进行单道次堆焊,通过对焊缝断面的宏观金相观察,分析不同焊接工艺参数对回火焊道焊接技术中焊接接头几何尺寸的影响.结果表明.回火焊道焊接技术的实现与焊接电流和送丝速度关系明显,焊接电流对热影响区深度d尺寸影响较大,送丝速度主要起改变焊道余高(b)的作用,焊接电流越小或送丝速度越大,b+h(焊缝熔深)与d的差值越小,越利于回火焊道焊接技术的实现;焊接速度对焊接接头各几何尺寸影响均较大,焊接速度变化不能明显地改变b+h与d的差值.     

新型低能量输入电弧焊接系统的研制

研制了由焊接电源和送丝系统两部分组成的低能量电孤焊接系统.焊接电源采用IGBT逆变技术,以数字信号处理器(DSP)TMS320F2812为控制核心;送丝系统以交流伺服电机作为送丝电机,通过软件设计了焊丝运动曲线.提出了专门的送丝控制和电流波形控制方案'通过焊接参数配合焊丝运动,实现了稳定的低能量焊接过程.试验结果表明'设计的低能量电孤焊接系统取得了一致性好的理想焊接电流、电压波形,焊缝成形美观,满足低能量焊接的要求.     

一种用于碳化钨堆焊的管装电焊条的研究

提供一种用于碳化钨堆焊的管装电焊条。扫描电镜观察、能谱分析及显微硬度测试结果表明堆焊层中存在两种类型的硬质相 ,即 WC- W2 C共晶的原始碳化钨颗粒(硬度 HV2 0 12～ 2 34 1)和 M6C构成的 η相 (HV1817～ 2 2 14)。M6C相以粒状和团块状存在 ,与实芯焊条堆焊的金属中析出的鱼骨状共晶 M6C相比较 ,在不降低堆焊层硬度条件下 ,可提高堆焊层的强度和韧性指标。新型焊条中使用 D型热绝缘剂 ,减少了原始碳化钨颗粒的熔损 ,使焊缝金属组织中硬质相分布域直径 Dd 和面积分数 AC 分别提高2 5 %和 6 2 %。     

Influence of welding current in plasma–MIG weld process on the bead weld geometry and wire fusion rate

One of the versions of the plasma–metal inert gas (MIG) process is basically a combination of a plasma arc with a MIG/metal active gas (MAG) arc in a single torch. With this association, the advantages of each arc are combined. The main characteristic of this is the independence between the heat input by the process and the deposited material, resulting in greater facility to control bead weld geometry. In the current literature, there is a shortage of information related to the process, and most of this goes back to the 1970s and 1980s when the technology available was not able to make the process viable for industry. However, in recent years, the use of the diffusion of new electronic power sources used in welding has sparked up again the interest in plasma–MIG process. In this context, this paper aims to contribute to the studies related to the influence of the MIG and plasma current balance on the geometry of the bead weld and wire fusion rate. Bead-on-plate welds were carried out with plasma and MIG/MAG current combinations at three levels each, keeping, by welding speed corrections, the bead volume the same. It was observed that the introduction of the plasma current over the MIG/MAG current reduces penetration and dilution and leads to convex beads. On the other hand, the use of plasma current increases the MIG/MAG wire fusion rate. However, it seems that the intensity of the plasma current is not the governing parameter of those changes.     

Research on laser-arc hybrid welding of lap fillet joints of thin sheet

ABSTRACT

Laser welding is capable of welding at high speeds by high-density energy, while arc welding is an effective construction method from the viewpoint of tolerance of the gap and welding position. Laser-arc hybrid welding has both these features. The authors have researched suitable welding parameters and consumables for this hybrid welding process that couples laser beam with MAG arc for lap fillet weld joining of thin steel sheets. As a result, the following welding parameters have been proven to be the most appropriate for better bead shapes and root-gap tolerance, i.e. laser leading (kept at a right angle) and MAG trailing (kept at a push angle); the laser-arc distance was 3 mm and the laser beam focus size was 2 mm. In addition, it was proven that HT490-class welding wire of Si-Mn-Ti type (JIS YGW11) was the most appropriate for better bead shapes and root-gap tolerance. The bead shape was apt to be better in cases of higher surface tension of welding wire. The result of the tensile shear test of the joint by welding with HT490-class welding wire of Si-Mn-Ti type (JIS YGW11) under selected welding condition demonstrated that the value of the tensile strength of parent material was equal to that of lab fillet joints.     

基于视觉技术的铝合金TIG焊接过程自适应控制

将视觉传感技术与自适应控制技术相结合用于铝合金TIG焊接过程质量控制。分析了铝合金焊接过程的特点，将随机系统理论引入焊接过程，建立了焊接参数与熔池几何参数之间的随机系统模型，实现了对模型参数的在线辨识。设计了基于最小方差调节的自适应焊接电流调节器。试验结果表明，自适应控制方法可以实现对铝合金TIG焊缝成形的良好控制。     

Effect of welding current and speed on occurrence of humping bead in high-speed GMAW

The developed mathematical model of humping formation mechanism in high-speed gas metal arc welding (GMAW) is used to analyze the effects of welding current and welding speed on the occurrence of humping bead. It considers both the momentum and heat content of backward flowing molten jet inside weld pool. Three-dimensional geometry of weld pool, the spacing between two adjacent humps and hump height along humping weld bead are calculated under different levels of welding current and welding speed. It shows that wire feeding rate, power intensity and the moment of backward flowing molten jet are the major factors on humping bead formation.     

An image-guided mobile robotic welding system for SMAW repair processes

Conventionally, shield metal arc welding (SMAW) has been performed by manual operator, and hence it is not easy to apply in hazardous areas such as in nuclear power plants. An image-guided mobile robotic welding system is developed in this study for the automation of the SMAW process. The position of cracks can also be determined by this image-guided mobile robotic welding system. We installed two CCD cameras, a five-axis SCORBOT-ER VII robot and SMAW equipment on a mobile vehicle. The cameras are installed in parallel and can be used to detect the position of any cracks beforehand; the robot is then driven at a constant welding speed along the welding path. Based on the binocular images captured by the CCD cameras, an on-line algorithm is used to compare the disparities between the two images and to obtain the welding paths for the cracks. Since the electrode is consumed during the SMAW process, the robotic joint trajectories need to be modified to keep the end of the electrode on tracking on the desired welding path. The control system determines the feeding velocity of the electrode from the measured welding current and joint positions and modifies the joint trajectories correspondingly. The experimental results show that our system can effectively perform SMAW operations resulting in good quality welding. Also, the variation of the welding current in our system is much smaller than that operated by even senior technicians.     

弧焊机器人轨迹规划及应用研究

机器人弧焊技术,因焊接质量稳定、生产效率高等优势,在汽车工业中得到广泛的应用。在建立机器人弧焊工作单元的基础上,本文分析研究了弧焊工作站运动仿真、离线编程的实际应用及影响焊接质量的因素。通过使用轨迹优化仿真软件,指导焊接工装设计,降低投资成本;进一步的离线编程的使用使得虚拟轨迹与真实机器人运动轨迹挂钩,提高了工作效率和可靠性。通过实验对比及弧焊工作站的调试,讨论了焊接电流、焊接电压、机器人焊接速度对焊接质量的影响。     

激光焊熔池图像三维形态恢复算法分析

利用熔池图像表面的明暗变化恢复熔池表面三维形态,分析熔高和熔宽等特征与焊接质量的关系.试验装置采用红外激光辅助光源和带有近红外窄带滤波组合系统的高速影像设备实时捕捉熔池动态图像,并根据统计学估计光源位置参数,采用基于单幅熔池灰度图像的明暗恢复形状技术(shape from shading,SFS)中的局部分析算法来恢复熔池三维表面形态,并通过中值滤波和三次样条插值对三维重建后熔池形状进行去噪和平滑处理.结果表明,所采用的方法能有效地恢复熔池表面信息,为大功率盘形激光焊接过程中根据熔池二维图像预测焊缝成形提供了一种方法.     

Prediction of bead geometry in pulsed GMA welding using back propagation neural network

This paper presents the development of a back propagation neural network model for the prediction of weld bead geometry in pulsed gas metal arc welding process. The model is based on experimental data. The thickness of the plate, pulse frequency, wire feed rate, wire feed rate/travel speed ratio, and peak current have been considered as the input parameters and the bead penetration depth and the convexity index of the bead as output parameters to develop the model. The developed model is then compared with experimental results and it is found that the results obtained from neural network model are accurate in predicting the weld bead geometry.     

电阻点焊质量监控技术的发展现状和趋势

随着计算机技术和智能控制技术的发展，数理统计、计算机模拟和人工智能等先进方法已引入点焊的质量监控中，如何采用精确的控制方法来监控电阻焊过程，已经成为电阻焊质量监控研究的重点。综述了电阻点焊质量监控的现状和发展，并提出可靠性是当前重要的研究方向。     

EXPERIMENTAL INVESTIGATION ON FORMING PROCESS OF HUMPING BEAD IN HIGH SPEEDMAG ARC WELDING

开展了高速活性气体保护( MAG)电弧焊接工艺实验, 确定出了不同焊接电流条件下形成驼峰焊道时的临界焊接速度、相邻驼峰之间的距离以及同一驼峰焊道“波峰”和“谷底”的断面形貌. 基于高速MAG电弧焊熔池的视觉检测图像, 分析了驼峰焊道的产生机理, 并利用上坡焊和下坡焊实验进行了验证. 同时, 也分析了保护气体成分对高速MAG电弧焊焊缝成形的影响.     

镁合金AZ31B的激光-TIG复合热源缝焊工艺

以AZ31B变形镁合金为主要对象,研究了其激光-TIG复合热源缝焊工艺特点,探讨了缝焊表面成形、缝焊熔深的影响因素以及缝焊缝的抗剪强度变化规律。结果表明,激光-TIG复合缝焊的焊缝为明显的“图钉型”形貌,上部分为TIG电弧焊接成形,下部分为典型的激光焊接成形。镁合金复合热源缝焊具有焊接速度高、焊缝成形美观、焊接参数范围较宽等特点,接头抗剪强度较高,是一种优良的焊接方式。