Potential Oxidative Stress in the Bodies of Electric Arc Welding Operators: Effect of Photochemical Smog

Objective To investigate whether photochemical smog emitted during the process of electric arc welding might cause oxidative stress and potential oxidative damage in the bodies of welding operators. Methods Seventy electric arc welding operators (WOs) and 70 healthy volunteers (HVs) were enrolled in a randomized controlled study design, in which the levels of vitamin C (VC) and vitamin E (VE) in plasma as well as the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX), and the level of lipoperoxide (LPO) in erythrocytes were determined by spectrophotometry. Results Compared with the average values of the above experimental parameters in the HVs group, the average values of VC and VE in plasma as well as those of SOD, CAT and GPX in erythrocytes in the WOs group were significantly decreased (P<0.005-0.0001), while the average value of LPO in erythrocytes in the WOs group was significantly increased (P<0.0001). The findings from the partial correlation analysis on the controlling of age suggested that with a prolonged duration of exposure to photochemical smog the values of VC, VE, SOD, and GPX, except for CAT, in the WOs were decreased gradually (P<0.05-0.005), the value of LPO in the WOs was increased gradually (P<0.001), and that with the ozone dose increased in the air in each worksite VC, VE, SOD, CAT and GPX decreased (P<0.005-0.001), but LPO increased (P<0.001). The findings from the reliability analysis for the VC, VE, SOD, CAT, GPX, and LPO values which were used to reflect oxidative stress and potential oxidative damage in the WOs showed that the reliability coefficients?alpha (6 items) was 0.8021, P<0.0001, and that the standardized item alpha was 0.9577, P<0.0001. Conclusion Findings in the present study suggest that there exists an oxidative stress induced by long-term exposure to photochemical smog in the bodies of WOs, thereby causing potential oxidative and lipoperoxidative damages in their bodies.

A novel wavelet method for electric signals analysis in underwater arc welding

Electric signals are acquired and analyzed in order to monitor the underwater arc welding process. Voltage break point and magnitude are extracted by detecting arc voltage singularity through the modulus maximum wavelet （MMW） method. A novel threshold algorithm, which compromises the hard-threshold wavelet （HTW） and soft-threshold wavelet （STW） methods, is investigated to eliminate welding current noise. Finally, advantages over traditional wavelet methods are verified by both simulation and experimental results.

Analysis of Aluminum Alloy Double-Pulse MIG Welding Arc Signal Characteristics Based on Broadband Mode Decomposition

Welding voltage and current in arc signals are directly related to arc stability and welding quality.Process experiments with different parameters were organized according to the orthogonal experimental design method by constructing an aluminum alloy double-pulse metal inert gas(MIG)welding arc electric signal test platform.The data acquisition system of the aluminum alloy MIG welding process was established to obtain real-time arc signal information reflecting the welding process.The aluminum alloy’s collected double-pulse arc current signals are decomposed adaptively by broadband mode decomposition(BMD).The direct current(DC)signal,pulse signal,distortion signal,ripple signal,and noise signal are separated and extracted,and the composite multiscale fuzzy entropy(CMFE)is calculated for the component set of the electrical signal.The experimental results show that the current waveform obtained by the double-pulse MIG welding current signal is consistent with the corresponding weld forming diagram.Simultaneously,the composite multiscale fuzzy entropy is calculated for the arc characteristic parameters.The rationality of matching process parameters and arc stability of aluminum alloy’s double-pulse MIG welding were evaluated.

Challenge to Welding and Joining Technology for Applying Multi-material in Electric Vehicle Production

Advanced high strength steel,aluminum alloy and plastic materials are used in the right places for the purpose of reducing the weight of EV(electric vehicle)bodies and in-vehicle parts,and multi-material structures are advancing.Therefore,it is difficult to handle the welding and joining processes of automobile structures by the conventional arc welding and resistance spot welding,which have been applied to steel joining,and various joining processes are being applied depending on the material.Under above mentioned background,the authors have developed some unique joining processes for multi-materials that are used in the right place.This paper introduces the dissimilar metal joining between the galvanized steel and aluminum alloy by laser arc hybrid process,the metal/thermoplastic dissimilar material joining using laser process and the solid-state resistance spot joining process of advanced high strength steel for EV body structural parts.Moreover,the authors describe the high-speed plasma jet GTA(Gas Tungusten Arc)welding process of copper applied to electrical components such as motors.

FRACTAL RESEARCH ON CRACKS PROPAGATION OF GAS PIPELINE X52 STEEL WELDING LINE UNDER HYDROGEN ENVIRONMENT

Based on the theory of hydrogen enhanced localized plasticity of the hydrogen induced cracking and the consideration of the effect of the residual stress produced by eliminated stress heat-treatment, a fractal model of hydrogen induced cracking was presented, and the relationships among the effective surface energy (H), fractal dimension D and stress intensity factor of hydrogen induced cracking, KIH, for welding pipeline under hydrogen environment was set up, from which the relationship of D and KISCC was obtained. The model has been verified experimentally to be correct.

Arc characteristics of submerged arc welding with stainless steel wire

The arc characteristics of submerged arc welding （SAW） with stainless steel wire were studied by using Analysator Hannover （AH）. The tests were carded out under the same preset arc voltage combined with different welding currents. By comparing the probability density distribution （PDD） curves of arc voltage and welding current, the changes were analyzed, the metal transfer mode in SAW was deduced, and the characteristics of a stable arc were summarized. The analysis results show that, with an increase of welding parameters, the short-circuiting peak in the PDD curves of arc voltage decreases gradually until it disappears, and the dominant metal transfer mode changes from flux-wall guided transfer to projected transfer and then to streaming transfer. Moreover, when the PDD curves of arc voltage are both unimodal and generally symmetrical, the greater the peak probability and the smaller the peak span, the more stable the arc becomes.

Arc Characteristic and Metal Transfer of Pulse Current Horizontal Flux-Cored Arc Welding

In this work, we utilized high-speed video photography to investigate the arc characteristics, metal transfer behavior, and welding spatter of the pulse-current flux-cored arc welding (P-FCAW) process in the horizontal position. The results indicate the presence of a stable “flux pole” during both the pulse-on and pulse-off periods when the mean current ranged from 140 to 170 A. The existence of this “flux pole” was beneficial for droplet transfer in the “axial droplet transfer” mode. With respect to welding spatter, with an increase in the welding current, we observed three kinds of spatter—explosive spatter, rebounded droplet spatter, and scattering spatter. With an increase in the pulse current from 310.6 to 345.6 A, the deflection of the arc reduced from 30.4° to 16.6°, which positively influenced the arc rigidity, particularly in the horizontal position. © 2017, Tianjin University and Springer-Verlag Berlin Heidelberg.

Stability of fiber laser-MIG hybrid welding of high strength aluminum alloy

The effect of fiber laser on MIG arc was investigated with 8 mm 7075-T6 high strength aluminum alloy as base material.The arc shape,droplet transfer form and electrical signal in the process of MIG welding and laser-MIG hybrid welding were analyzed.The stability of the hybrid welding process was evaluated by standard deviation analysis.The results show that with the increase of laser power,a large number of laser-induced plasma enters the arc column area,providing more conductive channels,which makes the heat of MIG arc more concentrated and the short circuit transition disappear.Due to the continuous effect of laser,the keyhole becomes a continuous electron emission source,and a stable cathode spot will be formed near the keyhole,which enhances the stability of MIG arc at the base current state.By using the method of standard deviation analysis,the voltage standard deviation of single MIG welding arc and laser-MIG hybrid arc within 4 seconds was calculated.The standard deviation of single MIG arc voltage was 1.05,and the standard deviation of MIG arc voltage in laser-MIG hybrid welding was 0.71–0.86,so the hybrid welding process was more stable.

Development of Welding Multi-Information Remote Wireless Monitoring System Based on STM32

A single sensor is used to obtain welding information in welding monitoring process, but this method has some shortcomings. In order to obtain more comprehensive and reliable welding information, this paper designed and built a welding multi-information wireless monitoring system with STM32-F407ZET6 as the control core and ALK8266 as the wireless transmission module. Real-time acquisition, transmission and display of electric arc signal and welding image information are realized in the monitoring system. This paper mainly introduces the hardware and software core of the monitoring system. At the same time, the signal collected by the monitoring system is compared with the original signal, and the accuracy of the remote monitoring system is tested. The monitoring system is used in welding test. The test results show that the accuracy of the monitoring system meets the requirements, and the on-line monitoring of electric arc signal and welding image can be realized in the welding process.

大熔深K-PAW熔池及电弧视觉行为特征分析研究

穿孔等离子弧焊接(K-PAW)以其独特的优势,在中厚板的焊接制造中应用广泛,并逐渐向更大厚度的方向发展。然而,随工件厚度增加熔池穿孔出现不稳定等问题,制约了其在实际生产中的应用。分析了14 mm厚304不锈钢在“受控恒定穿孔”控制策略下的大熔深K-PAW熔池特征尺寸变化规律和焊接过程中的熔池行为。通过视觉检测与电信号同步采集系统,对大熔深K-PAW过程中熔池的形貌特征进行定量分析,探究在受控脉冲条件下的熔池特征参数变化情况,以及熔池特征与电信号的同步动态行为规律。以初始电流270 A进行焊接,在起弧的前14 s的盲孔阶段,随着电弧热量积累,熔池不稳定,尺寸出现震荡,最大震荡幅度超过10 mm,同时熔池长宽比也在1.0~1.6范围内变化;随着穿孔于第15 s发生,熔池达到平衡,且长宽比在19 s时达到峰值;维孔阶段,熔池保持稳定,形状未发生大变化。综上,可以通过熔池形状变化趋势来区分焊接阶段。比较了不同焊接电流(280 A、275 A、270 A)的盲孔阶段,发现采用较大的初始电流有利于缩短盲孔时间,由270 A时的22.9 s减小到了280 A时的19.8 s,并降低焊接气孔出现的可能性。最后,发现电弧中心与熔池前边缘的距离可以反映穿孔状态。结果验证了“受控恒定穿孔”控制策略的可行性,并验证了通过视觉特征判断焊接阶段及是否穿孔的可行性。

厚板窄间隙焊接技术研究现状与应用进展

窄间隙焊接技术已经成为现代工业生产中厚板结构的首选技术,其技术和经济优势决定了它是今后厚板焊接技术发展的主要方向之一,近年来随着科技工作者的不断探索和研发,相继涌现了多种窄间隙焊接方法,文中对电弧焊、激光焊和激光-电弧复合焊等窄间隙焊接制造技术进行了系统阐述,概述了不同热源窄间隙焊接制造过程中的焊接质量、焊接效率的影响因素,归纳了不同热源窄间隙焊的工艺特点及应用领域,结合国内外相关技术的发展现状,总结了窄间隙焊技术面临的问题,提出了后续的发展建议,为相关领域的科研工作者提供参考.

双眼电焊弧光黄斑损伤1例

电焊在日常工作中广泛使用,但操作工人常常会受到电焊弧光的照射,导致眼部损伤,影响视力。因此,工作中对眼部的保护非常重要。本院曾收治1例因焊接工作时未采取眼部防护措施而导致双眼黄斑光损伤的患者。在此患者就诊期间,使用了激光扫描检眼镜(SLO)、光学相干断层扫描血管成像(OCTA)和光学相干断层扫描成像(OCT)等设备,监测其视网膜黄斑的变化情况,及时了解病情发展并评估预后。根据检查结果和视网膜黄斑损伤的情况,积极调整治疗方案,实现了早发现和早治疗,避免了病情加重对视力的进一步损害。当发现患者的双眼黄斑区出现脉络膜新生血管后,及时采取了玻璃体腔内抗血管内皮生长因子(VEGF)药物注射的方法进行治疗,成功挽救了患者的视力。在治疗过程中,使用OCTA记录了注射后黄斑区脉络膜新生血管的密度、面积变化及波动情况,这些数据为治疗带来了明显的帮助和收益。因此,OCTA和OCT在视网膜黄斑病变类疾病的治疗中具有重要的指导意义。

MAG焊接过程电信号分析

针对MAG弧焊电信号时变非常迅速的非线性特点,以及采集信号过程中存在各种干扰的情况,采用小波分析去噪滤除噪声干扰。通过分析滤波后的电压电流对照曲线,总结了MAG焊在短路模式下的典型电压和电流历史原理,分析了焊接过程中实时电阻变化趋势。通过绘制弧焊电信号的概率密度图、电压-电流曲线图,分析弧焊过程中的熔滴转移周期与每个周期中的短路持续时间,得到了该弧焊条件下电压电流的最大概率密度值,发现短路持续时间与熔滴转移周期呈现出一定的相关性。

涡旋齿端等β角圆弧类型线修正理论的研究

对等 β角圆弧类涡旋修正齿型进行了深入研究 ,得到了这类修正齿型的齿端生成方法、齿型特点及齿端修正参数的通用表达形式 .采用控制容积法导出了工作腔容积随动盘转角变化的解析计算式 ,提出了动态的切向和径向气体力作用面积的精确及简化计算方法 ,通过算例对两种方法作了对比和分析 ,明确了其使用条件 ,而这些修正理论适用于等 β角圆弧类修正的所有齿型 .

弧焊机器人工具参数标定

通过在末端安装不同的操作工具 ,可以利用机器人来完成各种作业任务。而工具参数的准确度直接影响着机器人末端的轨迹精度 ,因此研究一种准确、快速的工具参数TCF(ToolControlFrame)标定方法具有重要的意义。本文提出了一种标定工具参数的方法。该方法不仅可以标定工具参数的位置向量 ,还可以标定出姿态矩阵。利用该方法对本实验室的RHJD4- 1弧焊机器人的工具参数进行了标定 ,标定结果表明 ,该方法是一种简便、可靠的机器人工具参数标定方法。并设计制造了标准工具参数标定杆 ,可保证在更换钨极或误动作导致碰撞工具的情况下 ,不需要重复执行工具参数标定过程 ,就可以很方便、准确地实现工具校正。

双电极焊条单弧焊的电弧特性

针对双电极焊条单弧焊焊接新工艺 ,作者研究了其电弧静特性和双电极焊条的熔化特性 ,并用高速摄像机对双电极焊条单弧焊的电弧形态进行了研究。结果表明 ,双电极焊条单弧焊具有上升的电弧静特性 ,静特性曲线随两焊芯间距的增大而上移 ;在两焊芯间距合适的情况下 ,双电极焊条阴、阳极熔化速度可以保持一致 ,故双电极焊条单弧焊可使用交、直流电源 ,其熔化速度比单芯焊条的大并随焊接电流的增大和两焊芯间距的减小而增大 ;双电极焊条单弧焊电弧有多种形态。

焊接电弧的等离子流力

以试验为基础，分析了直流ＴＩＧ电弧阳极热斑表面等离子流力的径向分布、数学表达式、电弧长度及电流的影响，阐述了该力在整个电弧机械作用力中的地位。

镀锌薄钢板MIG/TIG电弧钎焊研究及应用现状

镀锌钢板MIG/TIG电弧钎焊与普通电弧焊相比,电弧钎焊电弧热量集中,对薄板及薄壁容器进行钎焊时变形量很小,焊接热影响区小,操作方便,节能高效又易于实现自动化,同时又因其电弧特有的“阴极雾化”去除氧化膜作用、带电离子和电子的冲击活化作用,以及克服钎剂对母材的腐蚀副作用,焊后不用清洗,在生产上,特别是汽车部件及电器制造上得到广泛应用。。

步进式电弧螺柱焊枪及控制系统的研究

在深入研究电弧螺柱焊过程及传统电弧螺柱焊枪的基础上,提出了一种全新的设计思想,以此研制开发了步进式电弧螺柱焊枪及其控制系统.焊枪的机械结构部分以步进电机为动力机构,以螺旋传动装置为运动机构主体,实现了电弧螺柱焊所需的螺柱运动过程;控制系统以MCS-51单片机为主控元件,实现了对焊枪及焊接过程的控制.螺柱提起高度、送下深度、提起和送下速度等焊接参数的设定由程序控制,减少了人工调整的随机误差;同传统电弧螺柱焊枪相比,此焊枪的参数调节具有相互独立的特性,送下深度可以在更大范围内调整.

焊接电参数对GTAW熔透状态的影响

针对非熔化极气体保护焊(gas tungsten arc welding,GTAW)过程中因焊接参数波动、热传导条件变化难以实时检测和控制熔透的难题,考虑304不锈钢相变潜热随温度的变化,建立了焊接电参数与熔池相变潜热、背面熔宽间的动态变化数学模型,仿真研究了改变焊接电流、电弧电压对焊缝熔透状态的动态影响规律,预测了恒定电参数下点焊熔透状态发生改变的时间.采集了同参数焊接过程中表征熔透状态变化的反射激光点阵视频图像,统计计算了实际熔透发生改变的时间.结果表明,所建立的动态数学模型能够反映焊缝熔透状态随电参数的动态变化过程,且焊接电流对熔透状态的影响更显著;熔透变化预测时间与实测时间一致.