塑料超声波焊接过程及质量研究 Ⅱ焊接接头熔化膜厚度计算模型

利用流变学基本理论 ,对焊接过程平衡阶段熔化膜的流动形态进行了理论分析 ,分别导出了工艺参数对熔化膜厚度和熔体剪切速率影响的计算公式 ,测量结果表明 ,理论计算结果和实际结果一致性较好 .     

塑料超声波焊接过程及质量研究 III焊接接头质量影响因素分析

从焊接工艺参数对焊件熔化状态及焊件熔化状态对接头质量的影响两个方面对塑料超声波焊接质量影响因素进行了研究 ,揭示了焊件熔化状态是影响接头质量的直接因素 .利用光学显微镜研究了接头的组织形貌 ,发现接头熔合区组织具有明显的取向 .对接头剪切和弯曲强度进行测试 ,发现接头力学性能具有各向异性 ,熔和区厚度和组织取向程度对接头有重要的影响 .     

超声波塑料焊接新技术与新工艺

本文概述了超声波塑料焊接的基本原理、特点和焊接工艺.     

超声波塑料焊接温度测量系统

建立了基于惠普可视化工程环境(HP VEE)的实时温度测量系统来测量超声波塑料焊接的温度;并介绍了 HP VEE 的功能、该温度测量系统的组成和采用该系统进行的超声波焊接 PVC 塑料的温度测量试验. 试验结果表明超声波塑料焊接的焊接区温度具有快速升温和快速降温的特点, 在降温过程中由于焊接压力的作用会出现短暂的温度平台, 也说明该测温系统适用于超声波塑料焊接温度测量.     

塑料超声波焊接技术(中)

(上接《塑料包装》2014年第6期)4.各种塑料的超声波焊接性塑料的性能影响超声波的成功焊接。塑料的超声波焊接性取决于塑料对超声振动的衰减能力和熔化温度的高低以及物理性能如弹性模量、抗冲击性、摩擦系数及导热系数等等。实验证明,塑料的焊接性G正比于弹性模量E、导热系数λ、摩擦系数μ,反比于塑料的密度ρ、比热C、熔点t,如     

振动熔接焊状态的超声波在线检测方法研究

本文讨论了利用超声脉冲反射探伤技术对振动熔焊接的过程中焊合面的状态进行实时在线监测的方法，并检测了焊接件的机械强度，最后用大量实验验证了超声波检测方法的可行性和正确性。     

异型焊接接头超声波探伤方法设计及验证

研究了斜面对接接头异形焊接接头超声波探伤,提出了切实可用的异型焊接接头超声波探伤方法,并通过对试样解剖验证了本探伤方法的可行性。     

塑料薄膜超声波焊接研究

利用4种不同厚度的PP薄膜进行超声热合实验,分别得到热合强度最高时相应的超声时间。对封合处的剖面进行显微观测,并对纸板进行同样的超声封合,发现在超声波作用时,材料间摩擦产生的热量是熔融材料实现焊接的主要原因。     

塑料超声波焊接技术(下)

(上接《塑料包装》2015年第1期)5.超声波焊接接头设计接头设计是超声波焊接的最重要方面。接头设计应在待焊零件还处于设计阶段时就加以考虑,并成为模制件的一部分。有各种各样的接头设计,每一种都有其具体的特点和优点。接头设计的选择由塑料种类、零件几何形状、焊接要求、机加工和模塑能力、表面外观等因素决定。为了获得合格的、可重复的焊接接头,必须遵循以下三条通用设计准则:1.配合表面之间的初始接触面积应足够小以     

塑料和聚合物的超声焊接

从塑料和聚合物的特性、塑料焊接方法分类、焊接的基本步骤、焊接特点方面介绍了塑料和聚合物的超声焊接。一般认为,超声焊接的研究内容主要是研究与超声有关的焊接声参数方面的问题。其实,在国外更多地是从材料方面研究焊件在焊接过程中物理性能的变化,对此做了较详尽的介绍。超声波在热塑性粘弹性介质中传播相对于金属介质来说有较大耗损,文中也介绍了测定粘弹性介质复杨氏模量的基本方法。     

Application and exploration of friction stir welding/processing in plastics industry

Friction stir welding (FSW) is a green, pollution-free, low-energy technology with high manoeuvrability. Thermoplastic plastics have extensive applications in the present industry because they offer excellent physical and corrosion properties, high degree freedom of processing and design. In this paper, the current state of FSW/P in plastics industry, including tool improvement, welding methods, process parameters optimisation, metal and polymer joining as well as composites fabrication, has been addressed. Although it presents a major challenge, FSW/P has a great potential to produce defect-free joint and fabricate composites in polymer materials.     

Experimental investigations on the polypropylene behavior during ultrasonic welding

The polypropylene material meets the needs and requirements in automotive industry due to its features such as wide range of physical properties, ease of processing, and low cost. This research has focused on the investigation of the behavior of polypropylene during ultrasonic welding process. The lap welded samples were examined by modern methods such as Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), and Fourier Transform Infrared Spectroscopy (FTIR). Also, the morphology of the non-welded and welded regions of the polypropylene samples was analyzed by Scanning Electronic Microscopy (SEM) method. TGA and DSC results showed a negligible difference between the mass loss of the molded and the welded propylene materials. Furthermore, the SEM images revealed the formation of voids in close correlation with vibration amplitude. The weld strength and bond integrity appears to be higher for higher vibrations, emphasizing that the lap joint interface strength is higher when the tendency of voids formation is decreasing. The stress-strain curve of the material, plotted for three ultrasonic welding variants, illustrated that increasing the main process parameters (pressure, time, and vibration amplitude) makes the weld strength higher, but a decrease in plasticity was noticed in the welded polypropylene samples.     

Testing of explosive welding and welded joints. Wavy character of the process and joint quality

The basic defects occuring in explosive clad plates were properly systemized and the reasons of their formation were explained. Cases of cracks and delaminations in explosive clad plates were examined in this work. Various values of tensile stresses coming from loading and unloading waves were analysed, as they were the main reason of defects. The defects were connected with properties of welded materials in the joint area and beyond it. Some practical aspects of this process were shown as well.     

Friction welding of Al–12Si parts produced by selective laser melting

Al–12Si samples produced by selective laser melting (SLM) are welded using solid-state friction welding. The weld metal shows the presence of texture with excess Si diffusing out from the Al matrix. Microstructural investigations reveal a pronounced change in the shape and size of the Si phase in the weld metal compared to the base material, with the formation of extremely fine particles uniformly distributed in the Al matrix. This variation in the microstructure is expected to have significant changes in the mechanical properties of the welded material. The hardness measurements reveal a drop of hardness in the weld zone with respect to the base metal. Similarly, the room temperature tensile tests show a significant improvement of ductility in the welded SLM samples. However, the yield and the ultimate strength show only a marginal drop in the welded samples compared to the as-prepared SLM specimens. The present work demonstrates that solid-state friction welding not only permits to successfully join materials produced by SLM, but also helps to significantly improve their ductility.     

铝合金搅拌摩擦焊超声检测研究进展EI北大核心CSCD

铝合金搅拌摩擦焊(friction stir welding, FSW)焊接参数选择不当将会产生隧道孔、未焊透(lack of penetration, LOP)和吻接等取向复杂、细微紧贴的缺陷。首先,本文简述了FSW焊缝与典型缺陷特征,总结了超声检测时面临纵向分辨力低、缺陷表征不完整、材料与缺陷声阻抗接近和灵敏度不足等难点。随后,从常规超声、超声衍射时差法(time-of-flight diffraction, TOFD)、相控阵超声检测技术和其他超声检测技术等方面综述了现有的铝合金FSW超声检测研究工作。最后,结合超声信号处理方法和机器学习方法对研究前景进行展望:可以通过分析和提取信号特征,进一步提升超声检测分辨力和信噪比,并实现取向复杂缺陷和细微紧贴缺陷的精准辨识与定量。     

Microstructure and mechanical properties of Cr12MoV by ultrasonic vibration-assisted laser surface melting

The effects of laser surface melting assisted by ultrasonic vibration on the microstructure and mechanical properties of Cr12MoV were investigated. Results indicated that the original coarse columnar dendrite can be converted into a fine dendritic and equiaxed. The average microhardness increase from 389HV_0.2 to 427HV_0.2 resulted from the effect of grain refinement. The friction coefficient was lower than the melted layer without ultrasonic vibration and substrate. Under the same experimental conditions, the width and depth of wear scar were decreased by 19% and 25% than that of without ultrasonic vibration, respectively. The wear mechanism from severe adhesive wear into slight abrasive wear under the action of ultrasonic vibration. Experimental results revealed that melted layer fabricated by ultrasonic vibration exhibit finer and more uniform microstructure as well as superior tribological properties.     

Experimental investigation and process optimization of the ultrasonic welding applied to papers

Ultrasonic welding is a serious candidate in the development of methods to assemble papers and paperboards without using additional substances. However, the ultrasonic welding of papers remains a technological challenge considering the low weldability of lignocellulosic materials. This study aims to investigate on the ultrasonic welding process applied to papers in order to identify the processing conditions which favor the formation of strong welded joints. To reach such purpose, an experimental strategy was developed by combining the characterization of welded materials and the monitoring of process parameters. Experimentations were performed using a reference paper displaying a good weldability to specifically highlight the contribution of process parameters. Results indicate that the process is highly sensitive to vibration amplitude, power supplied by the high frequency generator, and sample thickness. Power seems to be a reliable indicator of the severity of the process. A strong decrease in the strength of the welded joints is observed when working with low thicknesses. It seems that the layers coated on top of papers are the main part of the material contributing in the development of adhesion at the welding joint. Overall, instrumenting the device has led to a better understanding of the ultrasonic welding of papers.