Analysis of the oscillation behavior during ultrasonic welding of EN AW-1070 wire strands and EN CW004A terminals

For fulfilling the demand of durable yet lightweight electrical connections in transportation industries, ultrasonic metal welding (USMW) sees widespread use in these branches. As the ultrasound oscillations utilized in the welding procedure occur at a range of only a few micrometers at frequencies of 20–100 kHz for an overall duration of only 50–1500 ms, it is not possible to observe the compaction behavior with the bare eye. This paper focusses on investigating the oscillation behavior of the horn, the anvil, and the joining partners during the welding procedure by utilizing an array of synchronized laser vibrometers and performing welds with incrementing time stages. The oscillation data is correlated with temperature measurements in the welding zone as well as tensile testing results. Inter alia the formation of sidebands at the fundamental frequency as well as 2nd- and 3rd-order harmonics has been observed for the anvil, terminal, and wire front face when exceeding optimal weld time which would lead to maximum joint strength. Following the assumption of other research groups, the cause of these sidebands could be a change in relative motion of these components. As the terminal is slipping with increasing weld time, it could be assumed that the reason for the sidebands is low-frequency movement of the anvil, modulated onto the fundamental frequency, additionally indicating successful bonding of the stranded wire and the terminal. Furthermore, this slipping of the terminal on the anvil could lead to increased wear of the anvil knurls.

Dynamic Compression Properties of the Resistance Spot Welding of High Strength Steels under Varying Temperature Conditions

In this paper, we have studied the dynamic compression performance of the RSW of QP980 steel and TRIP800 steel by using a split Hopkinson pressure bar (SHPB), and we have also examined the fracture mode of the two research objects. It is found that the spot welding zone is primarily composed of the martensite structure, and there is a sparse defect of crystal structure adjacent to the center of nugget. In addition, there are evident gaps between the plates on both sides of the spot welding zone. Through the measurement of the microhardness of the two grade steel, it is found that the average hardness of the RSW of QP980 steel is higher than that of TRIP800 steel. There is a softening region in the interface of the heat affected zone and the substrate zone. The dynamic compression experiments are carried out on the RSW of QP980 steel and TRIP800 steel under 200°C and 300°C conditions, and it is found that the strain rate would increase with the rising temperature, but the compressive strength would experience declines. Furthermore, the sparse defects of crystal structure adjacent to the center of nugget would lead to stress rebound when the specimen is compressed. Moreover, through the observation of the fracture surface of the recovered specimens, it is found that the fracture of the nugget is brittle, whereas the fracture mode of the sample is more complicated. In addition, the fracture surface features a number of “river pattern” cleavage facets, and there are very few dimples of ductile tearing. This study is expected to have huge implications to the safety of vehicle body under high-speed impact.

Ultrasonic welding of folding boxboards

Today’s environmental concerns are pressuring industries to substitute paper-based materials in place of plastics in many sectors including packaging. However, assembling papers and paperboards using environmentally friendly solutions remains a technological challenge. In this context, ultrasonic (US) welding is an alternative to adhesives. In this work, the potential of US welding to assemble folding boxboards was investigated. Folding boxboards are commonly coated to enhance printability. This coating is generally composed of mineral pigments (85 to 90%) and polymer binders (10 to 12%). This study evaluated whether the presence of the coating layer allows the assembly of paperboards by US welding. Results indicated that welding coated folding boxboards is possible provided that coating weight and binder content are high enough. The mechanical performances of the welded boards met the requirements of most packaging applications. Adhesion in the welded joint resulted from a combination of thermoplastic (melting and flowing of the binder) and thermoset (degradation reactions) effects. However, it was not possible to assemble coated folding boxboards without degrading the welding zone. While the materials and process need to be optimized, this work represents a big step forward toward the adhesive-free assembling of paper-based materials.

Microstructures and Mechanical Properties of MIG Welded Al-Mg-Si-xCu Alloys

Welding properties of three alloys with different Cu contents (0.1, 0.4 and 0.9 wt.%) is studied by means of melt inert-gas welding (MIG). The results showed that, with the increase of Cu content from 0.1 wt.% to 0.9 wt.%, the strength and elongation increased obviously. When the Cu content was 0.9 wt.%, the strength and elongation reached 375MPa and 15%, respectively, which is a better match for bearing structure part of vehicles application. Besides, the adding of Cu element provided an increase limit for welding joint strength. Due to abundant coarse phases in fusion zone (FZ) and welding zone (WZ), the strength slightly increased and the failure fracture was different compared with that of 0.1Cu and 0.4Cu alloy. Present result was meaningful and valuable for pushing aluminum application automobile structural parts and other engineering components.

Technological properties of Al—Mg—Si alloys during manufacturing of thin-walled tubular products using welding and reduction

The reasons for the appearance of cracks during the reduction of filling nozzles made by using welding from the Al—Mg—Si alloy bars are studied. It is found that the cause of fracture is the embrittlement of the alloy and the deterioration of its deformability in the heat-affected zone of welding. Recommendations for eliminate the deterioration of the deformability of the alloy during the intensification of the cooling of the welding zone are developed, which makes it possible to preserve the zone-aged state in the heat-affected zone.

Dynamic recrystallization of friction welded AISI 316 stainless steel joints

The microstructural characteristics of friction welded AISI 316 stainless steel samples in a welding zone and a heat affected zone were investigated. Inhomogeneous plastic deformation occurred due to friction welding. Individual grains in the final microstructure underwent various evolution mechanisms. These were caused by the growth of the initially recrystallized grains or as a result of the dynamic recrystallization of the sub-grains formed. The grains within the welding zone and the heat affected zone exhibited different densities of dislocations and experienced various degrees of recovery. Using reasonable estimates of the strain, strain rate and temperature of the friction welding, the dependence of the dynamic recrystallization grain size was found to have the same dependence on the Zener-Hollomon parameter as material deformed via a conventional hot working process.

Computer Simulation of Thermal Processes in Arc Welding of Thick-Walled Aluminum Alloy Structures

This paper presents the results of computer simulation of the thermal processes occurring during welding of thick-walled structures made of the AMg6 aluminium-magnesium alloy, widely used in modern industry. The model takes into account features associated with intensive heat removal from the welding zone caused by the large overall dimensions of the welded structure and the high thermal conductivity of the material used. In practice, these features increase the probability of formation of such defects as non-fusion of the weld with the base metal of the connected elements. Modeling was performed using the finite element method in the ANSYS software package. A geometric model was developed, and the bodies were divided into finite elements. For the areas with expected high temperature gradients, the finite elements in the geometric model were chosen to be much smaller than those in the areas further away from the welding zone. This increased the accuracy of the solution and significantly reduced the calculation time. The model of the heat source was constructed taking into account the gradual deposition of the weld metal as the welding arc moved along the connected edges. The simulation results confirmed the possibility of applying the available welding modes for the studied conditions.

Methods for producing permanent joints of aluminum and titanium alloys

The results of the analysis of theoretical and experimental studies of methods for producing permanent joints of dissimilar metals and alloys are presented, as well as the advantages, implementation problems and prospects of using friction stir welding to join titanium and aluminum alloys. It is noted that most studies focus on friction stir welding of light metals such as aluminum, copper, magnesium and their alloys. Despite the great scientific and practical interest, the friction stir welding processes of alloys and metal-matrix composite materials based on aluminum and titanium have been studied less thoroughly and require additional attention.Given the variety and complexity of friction stir welding, the lack of a correct assessment of the reactivity, properties and design features of aluminum and titanium alloys can lead to a number of problems associated with a change in the structure of materials and defects in the welding zone, which is accompanied by the inevitable deterioration of the mechanical characteristics of the finished joints.