Numerical simulation of dynamic thermal process during doublesided asymmetrical TIG backing welding of large thick plates

The dynamic thermal process during double-sided asymmetrical TIG backing welding of large thick plates （ 1 000 mm×700 mm×50 mm） is numerically simulated using MSC. MARC. The effect of arc distance on the thermal cycle in weld zone during double-sided asymmetrical T1G backing welding is investigated. The results show that the workpiece experiences double-peak thermal cycle in double-sided asymmetrical TIG backing welding. On the one hand, the fore arc has the pre- heating effect on the rear pass, and the pre-heating temperature depends on the distance between the double arcs, the heat input of fore arc, and the initial temperature of workpiece. On the other hand, the rear arc has the post-heating effect on the fore pass. The mutual effects of two heat sources decrease with the increase of arc distance.

Optimization of back bead geometry in the PMAG-TIG twin arc hybrid root welding process using grey based Taguchi method

This study investigated multi-response optimization of the pulse metal active gas-tungsten inert gas( PMAG-TIG) twin arc hybrid root welding process for an optimal parametric combination to yield favorable back bead geometry of welded joints using grey relational analysis and Taguchi method.Eighteen experimental runs based on an orthogonal array following the Taguchi method were performed to derive objective functions to be optimized within the experimental domain.The objective functions were selected in relation to parameters of PMAG-TIG twin arc root welding back bead geometry: back bead width to root reinforcement ratio and deposited metal height.The Taguchi approach was followed by grey relational analysis to solve the multi-response optimization problem.The significance of factors on overall quality characteristics of the weld joint was also evaluated quantitatively using analysis of variance.Optimal results were verified through additional experiments,and showed to feasibility of applying grey relation analysis in combination with Taguchi technique for continuous improvement of product quality in the manufacturing industry.

Mechanism analysis of free formation of backing weld by the pulsed MAG-TIG double arc tandem welding

Because of the presence of lower-level automation and efficiency in the backing welding of medium–thick plates,pulse-metalactive-gas–metal-inert-gas(MAG–MIG)dual-arc welding was applied to backing welding of 24-mm-thick Q235-B plate and the process and mechanism of root welding with back formation were investigated.The heating position of the MAG-arc at the front of the molten pool could be adjusted by using the electromagnetic force between the MAG-arc and the MIG-arc,and part of the arc energy could work on the root face directly.By combining the arc-discharge behaviour and analysis of flow in the molten pool,the shear stress of a tungsten inert gas(TIG)arc to the molten pool could make the liquid metal flow backwards.Thus,the quality of the front and bottom liquid metal were reduced,which favored the balance and stability.Continuous and stable back formation with uniform penetration could be achieved by using the pulse MAG–TIG dual-arc welding technology.

Study on the all position automatic pipeline backing weld machine

As a result of the lower backing weld efficiency, the applying of automatic welding is seriously limited. So a kind of special automatic welder is designed and manufactured for backing weld. This paper introduces the character of the assembled pulse CO2 arc welding machine which has strong penetrability. It specifies the technology of controlling the parameters of all position automatic welding by computer and multi-axis controller. Moreover typical welding procedure parameters are provided. It is proved by examination that the economical and practical equipment and technology are suitable for the long-distance transmission pipeline, and it has a good foreground of spreading and applying.

Effect of Weld Parameters on Effective Notch Stress at Weld Root and Toe of Load Carrying Cruciform Joints

Cruciform joints in ships are prone to fatigue damage and the determination of type of weld plays a significant role in thefatigue design of the joint. In this paper, the effect of weld geometry on fatigue failure of load carrying cruciform joints inships is investigated using Effective Notch Stress (ENS) approach. A fictitious notch of 1 mm radius is introduced at theweld root and toe and fatigue stress is evaluated. The effect of weld leg length (l) and weld penetration depth (p) on ENS atweld root and toe are determined. The critical weld leg length (lcr) at which fatigue failure transitions from weld root toweld toe is investigated. An approximation formula for determination of the critical weld leg length considering weldpenetration depth (p) is proposed.

A NEURAL NETWORK FOR WELD PENETRATION CONTROL IN GAS TUNGSTEN ARC WELDING

Realizing of weld penetration control in gas tungsten arc welding requires establishment of a model describing the relationship between the front-side geometrical parameters of weld pool and the back-side weld width with sufficient accuracy. A neural network model is developed to attain this aim. Welding experiments are conducted to obtain the training data set （including 973 groups of geometrical parameters of the weld pool and back-side weld width） and the verifying data set （108 groups）. Two data sets are used for training and verifying the neural network, respectively. The testing results show that the model has sufficient accuracy and can meet the requirements of weld penetration control.

Prediction of Weld Bead Geometry in Plasma Arc Welding using Factorial Design Approach

The effect of various process parameters like welding current, torch height, welding speed and plasma gas flow rate on front melting width, back melting width and weld reinforcement of plasma arc welding on aluminum alloy is investigated by using factorial design approach. Variable polarity plasma arc welding is used for welding aluminum alloy. Trail experiments are conducted and the limits of the input process parameters are decided. Two levels and four input process parameters are chosen and experiments are conducted as per typical design matrix considering full factorial design. Total sixteen experiments are conducted and output responses are measured. The coefficients are calculated by using regression analysis and the mathematical models are constructed. By using the mathematical models the main and interaction effect of various process parameters on weld quality is studied.

Numerical simulation on the shape of liquid surface of TIG full-penetrated weld pool

Based on the analysis of the three-dimensional liquid surface behavior of TIG penetrated weld pool,the three-dimensional shape models of weld pool with different values of the back fusion zone radius RB were obtained.The effects of arc on the penetrated weld pool were studied by numerical simulation with finite elements analysis software Surface Evolver.The results show that the size and shape of the back weld pool are not affected obviously by the arc,and the top surface of the weld pool is lowered by arc.From pulse background to pulse peak,the increase of the arc voltage(or the arc light intensity) is due to two factors.One is the increase of the current,and the other is the lowering of the top weld pool surface.

Microstructure and pitting corrosion of shielded metal arc welded high nitrogen stainless steel

The present work is aimed at studying the microstructure and pitting corrosion behaviour of shielded metal arc welded high nitrogen steel made of Cromang-N electrode. Basis for selecting this electrode is to increase the solubility of nitrogen in weld metal due to high chromium and manganese content. Microscopic studies were carried out using optical microscopy(OM) and field emission scanning electron microscopy(FESEM). Energy back scattered diffraction(EBSD) method was used to determine the phase analysis, grain size and orientation image mapping. Potentio-dynamic polarization testing was carried out to study the pitting corrosion resistance in aerated 3.5% NaCl environment using a GillAC electrochemical system. The investigation results showed that the selected Cr-Mn-N type electrode resulted in a maximum reduction in delta-ferrite and improvement in pitting corrosion resistance of the weld zone was attributed to the coarse austenite grains owing to the reduction in active sites of the austenite/delta ferrite interface and the decrease in galvanic interaction between austenite and delta-ferrite.

根部加强的镁合金搅拌摩擦焊分析

常规搅拌摩擦焊中,不同厚度的材料所适配的最佳搅拌针长度也不相同,搅拌针过长或过短都会对焊接效果产生不利影响.为了解决这一局限性,提出了一种在焊缝背面添加适当厚度同种材料垫板的新型焊接工艺,在该工艺中,搅拌针长度大于被焊板材厚度,将垫板与母材焊接在一起,一方面,降低了对搅拌针长度的要求;另一方面,可消除焊缝减薄产生的不利影响.结果表明,采用该方法分析1.5 mm厚AZ31B镁合金的对接焊,接头抗拉强度最大可达母材的91.19%,此外,分析了焊缝横截面微观组织和显微硬度分布,通过所建立的卷积神经网络模型,对接头抗拉强度随参数变化的分布情况进行了预测,获取了最佳工艺参数.

摇动电弧窄间隙自由成形打底焊工艺研究

针对厚板坡口根部焊接难的问题,文中提出了一种采用摇动电弧的窄间隙坡口自由成形打底焊接方法,通过控制电弧做圆弧形轨迹摇动来调整电弧热分布,使焊接熔池自由凝固成形.进行了摇动电弧窄间隙自由成形打底焊接试验,研究了电弧摇动参数对打底焊缝自由成形的影响.结果表明:电弧摇动参数能显著影响打底焊缝自由成形,过小的摇动参数易使打底焊缝烧穿,适当增大电弧摇动参数可增强坡口侧壁与根部的熔透,过大的摇动参数会产生未焊透缺陷.

健听成年人全方向水平声源定位能力初步研究

目的利用360°全方向24和36声源测试设备,初步探讨健听中青年和健听老年前期-老年人水平声源定位特点。方法选取2021年4月至2021年9月中国人民解放军总医院耳鼻喉科收治的43例健听成年受试者为研究对象,其中男性22例,女性21例;根据年龄分为中青年组(21~49岁)20例和老年前期-老年组(50~72岁)23例。两组分别给予纯音听阈测试、全方向24声源(间隔15°)和36声源(间隔10°)水平声源定位(sound localization,SL)能力评估。给声强度60 dB HL,给声刺激为1 kHz啭音,通过计算均方根误差(root mean square,RMS)、平均绝对误差(mean absolutely error,MAE)等评估受试者的声源定位能力。结果24声源老年前期-老年组MAE、RMS均值高于中青年组的MAE、RMS均值,差异有统计学意义(P<0.05);36声源老年前期-老年组MAE、RMS高于中青年组的MAE、RMS,差异无统计学意义(P>0.05)。24声源和36声源前场MAE和RMS均高于后场的MAE和RMS,前后场的MAE和RMS比较,差异有统计学意义(P<0.01);左右场的MAE、RMS比较,差异无统计学意义(P>0.05)。24声源前后混淆比例为7.73%,36声源前后混淆比例为15.42%;24声源和36声源均为正前方的声源定位准确度最差;老年前期-老年组前后混淆的比例高于中青年组,差异无统计学意义(P>0.05)。结论健听老年前期-老年人全方向24声源和36声源水平定位能力,相比健听中青年组有所下降。左右场的定位准确度高,前后场的定位准确度低,正前方定位准确度最低。全方向水平声源定位能力的测试结果与扬声器数量有关,且反应趋势具有一致性。

基于改进麻雀搜索算法优化BPNN的电阻点焊质量预测

电阻点焊技术由于具有高效、自动化程度高等焊接特点,被广泛应用于汽车、航空航天和公共交通等制造领域,由于焊点在封闭状态下进行,焊接过程存在诸多影响因素且无法直接检测,因此,准确预测电阻点焊质量是生产过程中必不可少的环节.本文以2219/5A06铝合金为研究对象,在3种不同的装配条件(包括间隙和间距)下进行电阻点焊工艺信号的分析,并进行人工智能建模.为了提高电阻点焊质量评价的性能和效率,本文采用Logistic-Tent(LT)复合映射改进麻雀搜索算法(SSA)对反向传播神经网络(LT-SSA-BPNN)模型进行优化,模型的输入和输出分别为多信号融合后的变量和熔核直径.实验结果表明,与传统的标准反向传播神经网络(BPNN)模型相比,经过LT-SSA-BP模型优化后,预测结果的平均绝对误差(MAE)、均方误差(MSE)和均方根误差(RMSE)分别降低了36.17%、17.55%和51.75%.同时,LT-SSA-BP神经网络在添加了不同间隙和间距条件作为训练集后,其预测稳定性明显提高,可以成功预测电阻点焊质量.

基于BAS算法优化的电弧增材制造焊道尺寸预测

目的为提高实际应用中电弧增材制造对工艺参数的选取效率及成形形貌的控制效果,建立高效且精准的成形尺寸预测模型,实现对焊道尺寸的合理预测。方法在单层单道CMT电弧增材制造实验的基础上,建立基于天牛须搜索算法(Beetle Antennae Search,BAS)优化BP神经网络的焊道尺寸预测模型,利用BAS算法实现对BP神经网络初始权值和阈值的优化,可以实现预测不同工艺参数(焊接速度、送丝速度、干伸长)下焊道的成形尺寸(熔宽、余高)。利用试验验证BAS-BP预测模型的性能,与现有模型进行对比,结果结果表明该模型具有较高精度的预测效果,能够有效映射工艺参数与焊道尺寸之间的非线性关系,印证了该模型具有良好的拟合和泛化能力,同时其对焊道熔宽和余高的预测误差分别不超过0.2、0.12 mm,预测平均误差率均不超过6%,相对于其他预测模型表现出较好的准确性和稳定性。结论BAS-BP神经网络预测模型的输出误差较小,网络训练收敛速度加快,避免了过拟合及欠拟合的风险,有效提高了预测模型的泛化能力和预测精度,可以实现一定工艺参数范围内的焊道尺寸预测,为后续电弧增材的实时预测及控制参数应用提供了技术支持。

陈博来基于“肾为生痰之本”辨治肾虚痰阻型腰痛

肾主水,为先天之本,对于体内津液的运行输布具有重要作用,且肾与水腑膀胱互为表里,通过冲脉与“水谷之海”的胃有经络上的联系,故肾在痰的生成中起着关键作用。陈博来教授认为,肾虚痰阻型腰痛为本虚标实之证,“痰阻”为其标,“肾虚”为其本,临床以腰骶钝痛、痛处固定、腰部僵硬、肢体麻木或偏枯为主要特点,兼见腰膝酸软、喜按喜揉等表现。肾虚痰阻型腰痛的治疗可基于“肾为生痰之本”,以补肾祛痰为法,拟定理痰汤(主要组成药物为芡实、半夏、黑芝麻、柏子仁、白芍、陈皮、茯苓等)为基础方,针对不同兼症辅以健脾、宣肺等药进行加减治疗。其辨治思路可为临床中医治疗腰痛提供参考。

大坡度X70管线钢全自动焊内根焊接头组织与性能

【目的】国内山区管道焊接不可避免,目前内焊机仅用于坡度小于12°管道焊接。旨在为验证新开发的内焊机在坡度25°的适用性,为大坡度X70管线钢全自动内根焊工艺的制定提供理论指导。【方法】文中采用内焊机根焊,外焊机热焊、填充和盖面的全自动焊工艺对坡度25°X70管线钢进行焊接。焊后采用扫描电镜(SEM)和背散射电子衍射(EBSD)对母材、焊缝和热影响区组织进行观察,测试接头拉伸、弯曲、硬度、冲击、刻槽锤断等力学性能。【结果】平焊、立焊和仰焊的焊缝横截面成形一致。母材组织主要是针状铁素体和板条贝氏体。焊缝和热影响区组织主要是铁素体和贝氏体,但不同焊层的铁素体和贝氏体形态不同。母材和焊缝晶界之间以大角度晶界为主,应变主要集中在大角度晶界处。接头抗拉强度高于570 MPa;弯曲试样无裂纹出现;硬度小于400 HV10;冲击吸收能量较高,且熔合线>热影响区>焊缝;刻槽锤断断裂面无未焊透、气孔、夹渣、未熔合等缺陷。【结论】接头焊缝成形好、各项力学性能满足标准要求,新开发的内焊机可用于坡度25°X70管线钢焊接。

压力管道工程中有关焊接诸多认知误区和盲区浅析(二)——焊接工艺和焊接材料

结合国内工业压力管道焊接的现实情况,对焊接工艺评定、焊接方法、焊接材料、保护气体,预热和层间温度控制、焊后热处理以及焊补的补充规定。两大类异种金属焊接的特点和规律,以及P No.1~PNo.5与奥氏体不锈钢和镍基合金之间的异类异种钢坡口对接焊缝的焊接。

基于信号融合的镁合金激光焊接熔透状态监测

针对目前研究中缺乏镁合金激光焊接熔透状态监测的现状,提出了一种基于声图信号融合的镁合金激光焊接熔透状态监测方法;使用麦克风和高速相机监测激光焊接过程,将提取的声音、图像特征进行特征级融合,并输入反向传播神经网络中,实现镁合金熔透状态准确识别,准确率达100%。结果表明,与单独使用声音或图像特征进行监测相比,声音图像信号融合监测能获得更高的识别准确率;将声图融合特征输入经典机器学习方法中,均获得了较高的准确率;该方法准确识别了镁合金激光焊接熔透状态,有助于提高焊接质量。

430铁素体不锈钢薄板激光焊接背面飞溅和熔池动态的数值模拟

薄板的激光焊接对离焦量敏感,很小的离焦量偏差就会导致熔池不稳定。本文采用数值模拟的方法,研究了离焦量对0.6 mm厚430铁素体不锈钢薄板激光焊熔池动态行为的影响,分析了形成焊道背面飞溅的原因。结果表明,在目前所用的焊接工艺参数条件下,离焦量决定着激光热输入在熔池中的位置和分布。熔池中匙孔的深度随着离焦量的降低而增大,负离焦(-0.1 mm)形成穿透的匙孔,零离焦(0 mm)和正离焦(+0.1 mm)形成的匙孔尺寸较小。不同离焦量均形成具有束腰结构的熔透熔池,熔池表面和匙孔表面的流速最大。熔池高度方向上存在由中间束腰部位向上下表面流动的两个涡流,液体金属在熔池上表面由熔池后方向前方流动。匙孔中的蒸发作用力和表面的高流速使匙孔不断闭合,在底部形成封闭的气泡。背面飞溅只在负离焦条件下形成,零离焦和正离焦不产生背面飞溅。负离焦条件下,熔透熔池形成的初期在焊道背面形成小颗粒的滴落型飞溅,主要是由熔池重力和表面流动导致;在穿透匙孔形成的末期因为气泡破裂形成大颗粒的喷射型飞溅。正离焦条件下熔池的形态、流动较为稳定,预测的焊道横断面轮廓与实验结果吻合良好。

基于旋转电弧的窄间隙横焊打底工艺

【目的】J型铺设是最适合深水的海底管线铺设和海洋立管安装方法,常采用管道自动焊接装备完成横向环焊缝摆动焊接。针对摆动电弧P-GMAW横焊打底层焊缝成形不对称、背部成形一致性差等问题,提出了基于旋转电弧的窄间隙横焊表面张力过渡(Surface tension transfer,STT)打底工艺方法。【方法】以X65管线钢板材对接窄坡口为试验对象,模拟深水立管J型铺设焊接过程。【结果】基于Minitab的田口方法,建立了正交试验模型,通过焊接工艺试验,探究窄间隙横焊STT打底层焊接工艺规范及不同工艺参数组合对焊缝成形的影响规律。【结论】打底层焊缝背部成形一致性好,无未熔合、未焊透等缺陷。