Power consumption and friction coefficient in the ultrasonic consolidation of aluminium alloys

Energy input and friction behaviour are two of the key phenomena related with the welding bond of ultrasonic consolidation (UC) process. In this study, the effects of welding parameters, such as the building height, travel speed, oscillation amplitude and applied force, on the power consumption of the horn and friction coefficient of the welding interface of UC are investigated for aluminium alloys 2024 and 7075. Multiple regression equations are developed to estimate the power consumption and friction coefficient using the welding parameters. A line-contact friction test is performed to examine the friction coefficient of UC under the various applied forces and preheating temperatures. The quantitative relationships among the welding parameters, friction coefficient and power consumption are derived.     

Chemical and Mechanical Characterization of AISI 304 and AISI 1010 Laser Welding

This paper addresses to the dissimilar laser welding of AISI 304 and AISI 1010 steel thin sheets. Cracks-free dissimilar edge fillet welds have been conducted using a Nd:YAG laser. Geometrical, microstructural, chemical, and mechanical proprieties of the welds were investigated using electron microscopy, EDS and tensile test assisted by digital image correlating. The proper results were achieved at an energy density of 88 J/mm² using a 0.4 mm laser spot diameter. An austenite-ferrite structure characterizes the weld bead and the precipitation of the chromium carbide at the grain limits was observed in the heat affected zone. Good tensile behavior was obtained; dissimilar joint was fractured on the carbon steel side at 482 MPa and 0.35 stain.     

An Investigation on Vibration Welding of Amorphous and Semicrystalline Polymers

Vibration welding technique has been used to study the weld zone of thermoplastic polymers using ABS (amorphous), PC (amorphous), PMMA (amorphous), and PBT (semicrystalline). Polymers were welded using alike components and combinations of semicrystalline polymer with different amorphous polymers. Mechanical testing of welded polymers has proved that the tensile strength, elongation at break, and deformation was highest for PC–PC weld and least for ABS–ABS weld, when alike polymers were welded. However, welding of semicrystalline and amorphous polymer shows enormous reduction in its tensile strength as well as other tensile properties. Also, the tensile fracture of PBT with other amorphous polymers always occurred at weld zone which was not always in case of alike polymer welds. The weld strength of these polymers was observed to be dependent on the mechanical interlocking among the layers and not on interfacial bonding. This phenomenon may be due to the difference in glass transition temperatures of semicrystalline and amorphous polymers. XRD, FESEM, and AFM have been used in this study to observe the morphology of welded surfaces.     

焊接电弧电压模糊模型的相关辨识

叙述了采用模糊集合理论,通过相关分析法,建立系统预测模型的原理、方法及步骤,设计了以电弧电压为控制对象的实验系统,获得了该系统的预测模型、控制规则及预测表。本研究为焊接电弧实现人工智能控制提供了理论根据,也为复杂系统的建模提供了一种简便易行的方法。     

La-W、Ce-w、Y-W电极材料热发射性能研究

研究了稀土元素Ｌａ．Ｃｅ．Ｙ对钨极材料热电子发射能力和稳定性的影响．利用粉末冶金和压力加工方法,制备了系列稀土钨电极材料,并对它们分别进行了引弧、静特性等焊接性能研究,借助于扫描电镜和Ｘ－ｒａｙ能谱仪对镧钨、钇钨、铈钨等燃弧后的４种电极（含用于参照的钍钨电极）进行显微观察,分析了稀土元素在钨电极热发射过程中的行为和作用机制．研究表明：在中小电流时ｗ（Ｌａ２Ｏ３）＝２．２％的Ｌａ２Ｏ３－Ｗ电极具有较好的电子发射能力和稳定性,钇钨和铈钨次之,在大电流工作时,钇钨电极热电子发射能力和稳定性最好．     

Semantic weldability prediction with RSW quality dataset and knowledge construction

This paper presents a semantic Resistance Spot Welding (RSW) weldability prediction framework. The framework constructs a shareable weldability knowledge database based on the regression rules from inconsistent RSW quality datasets. This research aims to effectively predict the weldability of RSW process for existing or new weldment design. A real welding test dataset collected from an automotive OEM is used to extract decision rules using a decision tree algorithm, Classification and Regression Trees (CART). The extracted decision rules are converted systematically into SWRL rules for capturing the semantics and to increase the shareability of the constructed knowledge. The experiments show that the RSW ontology, along with SWRL rules that contains weldability rules constructed from the datasets, successfully predicts the weldability (nugget width) values for RSW cases. The predicted nugget width values are found to be in-close proximity of the actual values. This paper shows that semantic prediction framework construes an intelligent way for constructing accurate and transparent predictive models for RSW weldability verification.     

基于支持向量机的激光焊接过程的非线性辨识

针对激光焊接过程非线性系统建模困难的问题,研究基于支持向量机的非线性系统回归建模方法.支持向量机由核函数与训练集完全刻画,进一步提高支持向量机性能的关键是针对给定的系统设计恰当的核函数.用改进的核函数,对具有典型非线性特性的焊接过程进行辨识.仿真结果验证了该方法的有效性.     

Grain size correction of welding residual stress measurement in a carbon steel plate using the critical refraction of longitudinal waves

In this, a method to measure welding residual stress in butt-welded joints of carbon steel plates using longitudinal critically refracted wave (L_cr wave) is proposed. Cross-correlation was employed to calculate the difference in time of flight between L_cr wave, and the optimal step length for the measurements is discussed. To determine L_cr wave acoustoelastic coefficient of the heat affected zone (HAZ), the relationship between the L_cr wave acoustoelastic coefficient and the grain size is established. The results show that one cycle is the optimal step length for the difference in the time-of-flight calculation, and with increasing grain size increase, L_cr wave acoustoelastic coefficient decreases in the form of a power function. In addition, grain size can be determined by using amplitude of the L_cr wave, so that the measured value of welding residual stress in HAZ can be corrected. The welding residual stress in melted zone (MZ) is corrected by calibrating acoustoelastic coefficient of the MZ. The acoustoelastic coefficient of the MZ is larger than that of parent material (PM). At last, welding residual stress in the butt-weld joint is measured and corrected with the L_cr wave technique. The results are verified by the hole drilling method.     

焊接机器人运动学分析

为了研究焊缝轨迹跟踪的方法,以实验室专用HP-6焊接机器人系统为对象,对该机器人焊接系统进行了运动学分析.通过建立机器人焊接系统坐标系,导出机器人本体运动学方程和焊丝端头工具矢量齐次变换矩阵.接着,分析了焊接系统闭环运动学,求出机器人本体运动学逆解,从而得到机器人末端空间位姿.最后,通过试验分析,给出了机器人焊接系统整体运动方程.该方程为后续的焊缝轨迹规划提供可依据的数学模型,也为开展更深层次的机器人焊接系统智能化研究提供了可靠的运动学依据.     

STPL380管道焊后不热处理的焊接

在张家港东华优尼科低温液化石油气 (LPG)工程中 ,采用STPL380低温钢管材。根据美国UNOCAL企业标准的要求 ,此种管材的焊接应采用“焊前预热 +焊接 +焊后热处理”方法。因施工工期紧 ,焊后热处理时间不够 ,经试验 ,可免去焊后热处理工序。介绍了STPL380低温钢管材焊后不进行热处理的焊接方法