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Ultrasonic metal welding is a well-established solid state joining process for electrical applications. The process relies on the friction between workpieces and welding tools for joint formation. This friction is generated by the process force and the ultrasonic oscillation of the welding tools imposed on the workpieces. At such high frequencies, the occurrence of resonances in actual workpiece geometries is not surprising. It is known that critical dimensions in length and width lead to nearly no bond, depending on the welding frequency and the mechanical properties of the material. In real applications, this limits the possible designs of terminals and leads to extensive testing of clamping devices. It is also known that machine learning (ML) models for quality prediction based on power signals or tool oscillation can account for changes in welding position. In this study, we investigated the impact of part resonance and antiresonance on horn and anvil oscillation, power consumption and bond strength to identify typical behaviors induced by the workpieces. The influence of material thickness and roughness was considered, and numerical analysis of the natural frequencies of the workpieces was conducted. It can be shown that the results allow a distinction between the welding positions and workpiece geometries without directly measuring the oscillation patterns of the workpieces, allowing a simple validation of geometry weldability and clamping device in applications. Furthermore, the investigation allows the knowledge based specific deduction of signal parameters for future ML models, allowing a consideration of welding position and workpieces geometry with reduced test data. [ABSTRACT FROM AUTHOR]

One possible option for increasing the fatigue strength of welded joints is the use of so-called low transformation temperature (LTT) alloys. The aim is to introduce residual compressive stresses into the weld to counteract crack initiation and propagation. Until now, there has been no application of an LTT effect to high-performance welding processes such as the laser beam submerged arc hybrid welding process (LUPuS hybrid). First, the LUPuS hybrid single-wire process was further developed into the LUPuS tandem hybrid process. This makes it possible to equip the two submerged arc welding torches with different commercially available filler wires. The aim of the work is to further develop the LUPuS tandem hybrid welding process to enable the use of the LTT effect. The in situ alloying process for obtaining the LTT effect from commercially available material combinations was extended to the two-wire process. The alloy obtained was investigated by means of energy dispersive x-ray spectroscopy and hardness measurements and the influence on residual stresses was determined by the borehole method supported by electronic speckle pattern interferometry. [ABSTRACT FROM AUTHOR]

The transport and kinetic coefficients of copper plasma are studied. The temperature dependences of momentum transfer cross sections, collision frequencies (electron–atom, ion–atom), ionization and recombination rates, thermal diffusion, and thermal and electrical conductivity coefficients are calculated. Formulas are proposed that approximate the results of calculations with high accuracy. The temperature dependence of electrical and thermal conductivity is studied and compared with literature data. The obtained coefficients are necessary for the description of transfer processes in a copper non-equilibrium plasma. [ABSTRACT FROM AUTHOR]

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Copyright of Materialwissenschaft und Werkstoffechnik is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Due to its high energy intensity and the associated high welding depth, electron beam welding is particularly suitable for welding steel plates with high wall thicknesses. These are used, for example, in offshore wind power systems. However, due to the cooling conditions, the required cold toughness for offshore applications is often not achieved. The aim is to develop S355 ML steels – within the EN10025 4 standard – for welding monopiles for wind turbines. For this purpose, three parameters with different energy input are developed on three steels. The tests are carried out on plates with a wall thickness of 80 mm, whereby a full penetration weld must be achieved. The resulting top and bottom bead of the welds meet the standard DIN EN ISO 13919‐1. The parameters have an energy per unit length of 9.5 kJ mm−1 to 15.5 kJ mm−1. The resulting weld seams have an average width of 5.5 mm to 7.5 mm, and burn‐off of the manganese alloy element is observed, particularly on the top side of the seam. In addition, T8/5 times close to the weld seam of 11 s to 27 s are estimated using a simulation. [ABSTRACT FROM AUTHOR]