A Three-Dimensional Numerical Model for Predicting the Weld Bead Geometry Characteristics in Laser Overlap Welding of Low Carbon Galvanized Steel

Laser welding (LW) becomes one of the most economical high quality joining processes. LW offers the advantage of very controlled heat input resulting in low distortion and the ability to weld heat sensitive components. To exploit efficiently the benefits presented by LW, it is necessary to develop an integrated approach to identify and control the welding process variables in order to produce the desired weld characteristics without being forced to use the traditional and fastidious trial and error procedures. The paper presents a study of weld bead geometry characteristics prediction for laser overlap welding of low carbon galvanized steel using 3D numerical modelling and experimental validation. The temperature dependent material properties, metallurgical transformations and enthalpy method constitute the foundation of the proposed modelling approach. An adaptive 3D heat source is adopted to simulate both keyhole and conduction mode of the LW process. The simulations are performed using 3D finite element model on commercial software. The model is used to estimate the weld bead geometry characteristics for various LW parameters, such as laser power, welding speed and laser beam diameter. The calibration and validation of the 3D numerical model are based on experimental data achieved using a 3 kW Nd:Yag laser system, a structured experimental design and confirmed statistical analysis tools. The results reveal that the modelling approach can provide not only a consistent and accurate prediction of the weld characteristics under variable welding parameters and conditions but also a comprehensive and quantitative analysis of process parameters effects on the weld quality. The results show great concordance between predicted and measured values for weld bead geometry characteristics, such as depth of penetration, bead width at the top surface and bead width at the interface between sheets, with an average accuracy greater than 95%.

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。

Bead模型的不确定性范围查询与修剪算法

针对时空范围内,移动目标数据库中由于移动目标轨迹的不确定性导致的范围查询问题,在基于Bead/Necklace不确定性模型的基础上,将查询问题映射为2D平面的计算几何问题进行解决。针对时空中五种不同句法的不确定性范围查询类型确定了对应的定性查询算法,并通过查询多边形的偏置和轨迹点位置查询的方法实现新的修剪算法,其算法复杂度与查询区域边的数目呈线性关系。实验结果显示,提出的修剪策略更加有效地提高了系统的查询效率。

高温后再生保温混凝土损伤劣化数值分析

【目的】内部多孔且高温稳定的玻化微珠(glazed hollow beads,GHB)可在一定程度上减缓混凝土的高温损伤劣化,提升混凝土的抗火性能。为了进一步明确GHB改善混凝土抗火性能的机理,从细观尺度出发,提出一种可考虑初始缺陷和再生骨料(recycled coarse aggregate,RCA)取代率的再生保温混凝土(recycled aggregate concrete mixed with glazed hollow beads,RATIC)细观模型的建模方法。【方法】利用现阶段比较常用的塑性损伤模型,探究了RCA取代率(0,50%,100%)、GHB含量(0,70%,100%)和孔隙率(0,2%,4%)对于高温后RATIC力学性能的影响。【结果】结果表明:随着受火温度的提高,荷载作用下RATIC试件的损伤分布均呈现出逐渐加剧的趋势,且500℃后,试件的损伤分布较400℃之前严重。GHB的加入可在一定程度上缓减混凝土内部的损伤劣化,而RCA的加入会加剧此现象。此外,随着孔隙率增大,RATIC试件的强度逐渐变低。

秸秆/聚丙烯纤维-玻化微珠保温混凝土基本性能正交试验

应用正交试验法开展了16组秸秆/聚丙烯纤维-玻化微珠保温混凝土和3组玻化微珠保温混凝土基本性能试验。完成了秸秆粉末体积率VS、玻化微珠代砂率VG和聚丙烯纤维体积率VP这3种因素对秸秆/聚丙烯纤维-玻化微珠保温混凝土立方体抗压、劈裂抗拉强度极差和方差分析。结果表明:玻化微珠掺入可有效提高混凝土隔热保温性、工作性,但会造成强度损失。玻化微珠对混凝土抗压强度减小最为显著,最大损失幅度为24.64%,秸秆粉末和聚丙烯纤维对抗压强度影响可忽略;聚丙烯纤维对混凝土抗拉强度提高极为显著,最大提升幅度为16.72%,同时显著提高拉压比。基于试验数据建立了秸秆/聚丙烯纤维-玻化微珠保温混凝土抗压和抗拉强度预测模型,预测效果较好。

基于Kano模型的潮州珠绣文创产品设计可行性研究

“艺术精品化”是潮州珠绣的特点之一,但过于“艺术精品化”就成了阻碍发展的缺点,高昂的价格极大地局限了潮州珠绣产品在市场上的流通。随着文化经济的不断发展,文化创意成为发展热点。因此,切实从用户角度出发,打造紧密贴合市场需求的文创产品,对于非遗文化继承传播、文创产品创新设计与流通,具有积极的意义。

Diagnostic model of saliva protein finger print analysis of patients with gastric cancer

AIM:To explore the method for early diagnosis of gastric cancer by screening the expression spectrum of saliva protein in gastric cancer patients using mass spectrometry for proteomics.METHODS:Proportional peptide mass fingerprints were obtained by analysis based on proteomics matrix-assisted laser desorption ionization time-of-flight/mass spectrometry.A diagnosis model was established using weak cation exchange magnetic beads to test saliva specimens from gastric cancer patients and healthy subjects.RESULTS:Significant differences were observed in the mass to charge ratio(m/z) peaks of four proteins(1472.78 Da,2936.49 Da,6556.81 Da and 7081.17 Da) between gastric cancer patients and healthy subjects.CONCLUSION:The finger print mass spectrum of saliva protein in patients with gastric cancer can be established using gastric cancer proteomics.A diagnostic model for distinguishing protein expression mass spectra of gastric cancer from non-gastric-cancer saliva can be established according to the different expression of proteins 1472.78 Da,2936.49 Da,6556.81 Da and 7081.17 Da.The method for early diagnosis of gastric cancer is of certain value for screening special biological markers.

Electron beam welding of precipitation hardened CuCrZr alloy:Modeling and experimentation

In order to maintain the structural consistency during the welding of precipitation hardened copperchromium-zirconium(PH-CuCrZr)alloy components,electron beam welding(EBW)process was employed.Experimental study and numerical modeling of EBW process during welding of PH-CuCrZr alloy components were carried out.A 3D finite element model was developed to predict the output responses(bead penetration and bead width)as a function of EBW input parameters(beam current,acceleration voltage and weld speed).A combined circular and conical source with Gaussian heat distribution was used to model the deep penetration characteristic of the EBW process.Numerical modeling was carried out by developing user defined function in Ansys software.Numerical predictions were compared with the experimental results which had a good agreement with each other.The developed model can be used for parametric study in wide range of problems involving complex geometries which are to be welded using EBW process.The present work illustrates that the input current with a contribution of 44.56%and 81.13%is the most significant input parameter for the bead penetration and bead width,respectively.

Preliminary Application of WCX Magnetic Bead-Based Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry in Analyzing the Urine of Renal Clear Cell Carcinoma

Objective To evaluate the application of weak cation exchange (WCX) magnetic bead-based Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) in detecting differentially expressed proteins in the urine of renal clear cell carcinoma (RCCC) and its value in the early diagnosis of RCCC.Methods Eleven newly diagnosed patients (10 males and 1 female, aged 46-78, mean 63 years) of renal clear cell carcinoma by biopsy and 10 healthy volunteers (all males, aged 25-32, mean 29.7 years) were enrolled in this study. Urine samples of the RCCC patients and healthy controls were collected in the morning.Weak cation exchange (WCX) bead-based MALDI-TOF MS technique was applied in detecting differential protein peaks in the urine of RCCC. ClinProTools2.2 software was utilized to determine the characteristic proteins in the urine of RCCC patients for the predictive model of RCCC.Results The technique identified 160 protein peaks in the urine that were different between RCCC patients and health controls; and among them, there was one peak (molecular weight of 2221.71 Da) with statistical significance (P=0.0304). With genetic algorithms and the support vector machine, we screened out 13 characteristic protein peaks for the predictive model.Conclusions The application of WCX magnetic bead-based MALDI-TOF MS in detecting differentiallyexpressed proteins in urine may have potential value for the early diagnosis of RCCC.

基于地震数值模拟的溶洞型储层地震特征分析

为了解不同溶洞的“串珠”响应特征,以实际地震资料解释为基础,建立了塔里木盆地塔河南地区全层系的碳酸盐岩缝洞体与走滑断裂三维模型,包括流体类型、溶洞大小、强反射轴干涉距离、纵向分辨距离、横向分辨距离、充填类型和孔隙度7种单因素变量控制模式。对所建模型进行地震数值模拟实验并对模拟结果进行逆时偏移成像。分别从分辨率、振幅能量与控制因素方面对7种单因素控制模式在偏移剖面中的“串珠”响应特征进行了详细比较分析,发现溶洞内的流体类型变化无法在叠后剖面的“串珠”响应形态上进行区分,其影响主要表现为振幅能量随等效弹性参数变化;溶洞大小的影响与“串珠”响应振幅能量呈正相关,溶洞越大“串珠”响应越强;剖面中的强轴与溶洞间的干涉距离会影响“串珠”响应振幅能量;溶洞间纵向距离不会影响单个溶洞的“串珠”响应形式,其主要影响表现为相连部分的振幅能量;而溶洞间横向距离过小,会使两个溶洞的“串珠”响应合并,形成大溶洞的“串珠”假象。溶洞内的泥质充填程度与孔隙度均会影响“串珠”响应振幅能量。通过总结不同因素变量控制模式下地震响应特征的变化规律,为缝洞型储层的有效预测提供参考依据。

串珠状溶洞影响下桩基竖向承载特性离心试验

为探明串珠状溶洞对桩基竖向承载特性的影响,采用离心模型试验,研究桩基穿越两层溶洞且置于下伏溶洞之上时,不同溶洞顶板厚径比下桩基荷载-沉降特征,竖向极限承载力变化规律,桩身轴力、桩侧阻力及分项荷载变化规律,与下伏无溶洞时进行对比,提出合理顶板厚径比取值方法。结果表明:桩基穿越溶洞后,下伏溶洞顶板厚径比对其竖向承载特性影响较大,与下伏无溶洞相比,厚径比由0.5增大到3.0时,桩基竖向极限承载力影响度由57.4%降至4.0%,厚径比大于2.5后,竖向极限承载力影响度小于5.0%;厚径比增大时,桩基所穿越的溶洞范围内桩身轴力几乎不衰减,上、中层溶洞顶板范围内桩身轴力衰减速度减慢,传递至溶洞顶的荷载较大;在溶洞内桩侧阻力几乎不发挥,随厚径比增大,在上层和中层溶洞顶板范围内桩侧阻力减小;厚径比增加时桩侧阻力和桩端阻力占比分别呈逐渐减小和增大的趋势,逐渐向摩擦端承桩转化,厚径比大于2后,与下伏无溶洞时相比,桩侧阻力减幅小于10%。建议串珠状溶洞区的桩基穿越两层溶洞且置于下伏溶洞之上时,顶板厚径比大于2.5即可忽略下伏溶洞对桩基竖向承载特性的影响,可根据桩基承载需求确定合理的顶板厚度。

经肝动脉灌注栓塞微球对比碘化油乳剂治疗VX2兔肝癌模型对VEGF、CTGF和HIFα-1的影响及疗效评估

目的:观察栓塞微球对比碘化油乳剂经肝动脉灌注化疗栓塞对VX2兔肝癌模型血管内皮生长因子(VEGF)、结缔组织生长因子(CTGF)和缺氧诱导因子(HIF)α-1的影响及疗效。方法:选取VX2兔肝癌模型24只,使用随机数字表法分为空白对照组、栓塞微球组、碘化油乳剂组,每组8只。经肝动脉分别灌注0.9%氯化钠溶液1 mL、栓塞微球0.5 mL+表柔比星溶液0.5 mL、碘化油乳剂0.5 mL+奥沙利铂0.5 mL,观察并比较各组VX2兔肝癌模型VEGF、CTGF和HIFα-1水平及病灶坏死情况。结果:行化疗药灌注及栓塞后,各组的VEGF、CTGF和HIFα-1水平均有不同程度升高。术后7、14 d,栓塞微球组、碘化油乳剂组的VEGF、CTGF和HIFα-1水平明显高于空白对照组,差异均有统计学意义(P<0.05)。术后28 d,栓塞微球组、碘化油乳剂组的Ⅱ—Ⅳ级病灶坏死率高于空白对照组。栓塞微球组与碘化油乳剂组病灶坏死率的差异无统计学意义(P>0.05)。结论:经肝动脉栓塞治疗后,因使用栓塞药物不同造成不同栓塞水平可能影响VEGF、CTGF和HIFα-1表达及病灶坏死率。

基于热裂纹演化的玻化微珠保温混凝土渗透性能分析

为了改善火灾后混凝土结构耐久性退化问题,利用玻化微珠(GHB)的高热稳定性对混凝土耐高温性能进行提升,通过电通量法对高温后玻化微珠保温混凝土(GIC)的抗氯离子侵蚀性能进行测试,并结合混凝土试件热裂纹演化特征对其抗氯离子侵蚀性能劣化规律进行分析.结果表明:GHB的掺加显著改善了高温后混凝土抗氯离子渗透能力退化问题,与同强度等级的普通混凝土(NC)和硅灰混凝土(SFC)相比,掺加GHB后混凝土的电通量分别降低了约54.15%、32.69%.结合各试件热裂纹演化规律,认为这归因于GHB和硅灰对混凝土密实性的提高,以及GHB对混凝土抗高温损伤造成的积极影响.在此基础上,通过考虑热裂纹演化特征、GHB和硅灰的影响,建立了高温环境氯离子渗透性预测模型.

基于PSO-BP神经网络的双相不锈钢电弧增材制造焊道成形预测

Duplex stainless steel was formed through welding wire and arc additive manufacturing(WAAM)using tungsten inert gas.The effects of wire feeding speed(WFS),welding speed(WS),welding current,and their interaction on the weld bead width and height were discussed.Back-propagation(BP)neural network algorithm prediction model was established by taking the bead width and height as the output layer,and the network weight and threshold values were optimized using the particle swarm optimization(PSO)algorithm to obtain the prediction model of bead width and height.The predicted results were verified by experiments.Results show that the weld bead width increases with the increase in WFS and the welding current and decreases with WS.The smaller the WFS,the faster the WS,which is beneficial for the generation of equiaxed crystals.The smaller the welding current,the faster the cooling speed of the metal melt,which is conducive to the formation of dendrites.The interaction among WS,wire feed speed,and welding current has a significant effect on the bead width.The weld bead height is positively correlated with the wire feed speed and negatively correlated with the WS and current.The interaction between the wire feed speed and WS is significant.The optimized WAAM process parameters for duplex stainless steel are a wire feed speed of 200 cm/min,WS of 24 cm/min,and welding current of 160 A.The maximum error of the BP neural network in predicting the weld bead width and height is 7.74%,and the maximum error between the predicted and experimental values of the BP-PSO neural network is 4.27%.This finding indicates that the convergence speed is fast,improving the prediction accuracy.

焊缝高效精密磨抛智能技术研究进展

焊接表面的缺陷严重影响焊接结构件的后续加工和服役,焊缝的高效精密磨抛是获得焊缝高质量表面的关键技术之一,研究焊缝高效精密磨抛具有重大意义。聚焦于焊缝高效精密磨抛的智能技术,总结焊缝磨抛的特点,从基本磨抛原理和模型、智能磨抛设备以及力控算法和基于视觉技术的焊缝高效精密磨抛3个方面详细阐述了焊缝磨抛智能技术的发展现状;最后阐述智能技术给焊缝高效精密磨抛技术带来的机遇与挑战,提出该领域亟待解决的问题。

醋酸纤维包装缓冲力学性能仿真与试验研究

目的 探究醋纤包装样棒对爆珠的缓冲力学性能,减少样棒在高速输送时因受到冲击载荷导致爆珠破损。方法 采用超弹性模型的方法对爆珠材料的本构模型进行定义,通过仿真与程序迭代完成材料超弹性模型2个关键参数的确定;运用Abaqus软件对醋纤包装样棒进行轴向和径向挤压仿真,最后通过搭建试验台对样棒与爆珠分别进行拉伸试验和挤压试验。结果 超弹性材料参数为C10=5.2 MPa、D1=0.38 kPa时,仿真计算出压板下压力F与爆珠理论所承受的最大压力值的相对误差为3.4%,符合醋纤包装样棒缓冲力学性能的仿真要求。随着样棒径向和轴向挤压量的逐渐增大,压板的支反力也逐渐增大,醋纤包装样棒在承受轴向冲击时对爆珠的缓冲效果更优秀。结论 爆珠材料本构模型的建立及仿真试验分析为研究醋纤包装样棒的高速输送提供了理论基础。

基于抛物线模型的V形坡口焊道规划排布

为了提高大型相贯构件机器人焊接的焊道规划准确性,提出了抛物线模型,结合等面积与等高法研究了多层多道焊道排布方法.首先,规划焊接工艺参数、焊道的横截面、焊接顺序以及焊枪位姿,进一步推导出焊道排布算法的公式,借助MATLAB软件进行多层多道焊道排布的仿真;最后通过机器人焊接试验验证多层多道排布的方法.结果表明,仿真的焊道排布结果与试验的V形坡口每层每道轮廓相吻合,说明提出的基于抛物线模型的多层多道排布算法是准确可行的.该研究成果为机器人焊接相贯构件的多层多道焊道排布提供了重要的理论基础.创新点:(1)提出了一种V形坡口焊道的抛物线轮廓假设模型.(2)提出了等面积法与等高法相结合的多层多道焊道排布方法.

间隙填充电弧增材制造成形质量及组织性能研究

目的传统多道焊缝搭接模型存在沉积环境不对称、热量累积严重及最终成形质量差的问题,针对以上情况,提出了间隙填充模型,并研究了该模型对成形质量及组织性能的影响。方法以4043铝合金为填充材料,探究了沉积顺序、沉积方向、道间冷却时间及CMT电弧模式对搭接质量的影响。确定了多层多道沉积策略,分别基于间隙填充模型和传统搭接模型进行了长方体式试样的沉积,对比分析了所成形试样的成形质量、微观组织及力学性能。结果当送丝速度为5 m/min、焊接速度为0.6 m/min时,在CMT+P的电弧模式下,采用由内而外的沉积顺序、道间反向的沉积方向及无道间冷却时间的工艺组合所成形试样的搭接质量最佳,所沉积试样的表面不平度低于0.004 mm2。结论由间隙填充模型和传统搭接模型所成形试样的微观组织和力学性能并无明显差异,但基于间隙填充模型的沉积策略所成形的试样的成形质量更好。其顶部微观组织主要由柱状晶组成,底部微观组织以细小的等轴晶为主,中部的热影响区主要为粗大的柱状晶,且晶粒尺寸分布不均匀,而焊缝区主要由细小的等轴晶和柱状晶组成。

焊接工艺参数对Q345厚板L形接头焊接温度场的影响

以Q345厚板L形接头焊接过程为研究对象,提取厚板的V形焊道结构进行分析,基于双椭球功率密度分布体热源模型为输入热源,利用Visual Environment有限元软件建立其网格模型,并建立焊接热过程的计算文件。通过数值模拟焊接一段直板结构的V形焊道焊接热过程,模拟并分析不同焊接工艺参数下的厚板温度场,研究了不同有效热功率和焊接速度对焊接温度场的影响;并结合V形板焊接试验的红外激光测试数据,对比仿真结果温度云图截面,证明了温度场数据的仿真效果与实际吻合,数值模拟的数据准确;同时分析了不同热效率和焊接速度下,焊接温度场的不同温度区间的尺寸变化。计算结果表明,低温区的尺寸变小,证明厚板的散热效果比薄板好;由仿真的几组数据表明,加大焊道的热输入量,高温区下移,证实V形焊道对热输入的要求比双V形焊道高;焊接速度越大,高温区和低温区的体积越小,对比不同焊接速度的焊道温度场截面,高温区宽度的减小比率大于深度减小比率,即焊接速度对低温区的影响效果比高温区明显。

碳酸盐岩储层垂向长串珠形成机制

针对塔中地区碳酸盐岩储层开展波动方程正演模拟,采用有限差分法求解波动方程,重点揭示垂向长串珠形成机理。结果表明,单个高度较大溶洞、垂向叠置溶洞和走滑断裂与地层复合均可形成绕射波,对这些绕射波进行偏移成像,即可在垂直方向上形成长串珠状反射。单个溶洞形成的双串珠中,顶底界面反射系数不同导致顶部串珠波形为两谷夹一峰,底部串珠波形为两峰夹一谷;双溶洞形成的双串珠为反射特征相同的两个串珠,由此可加以区分;层面与走滑断裂复合也会导致垂向上多个串珠的存在,前提是碳酸盐岩内幕分层现象明显,且沿走滑断裂有溶蚀现象存在。这些结论对于明确复杂地震响应的成因机制,进而认识其地质模式,指导勘探开发具有一定借鉴作用。