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Walther, Dominik; Junger, Christina; Schmidt, Leander; Schricker, Klaus; Notni, Gunther; Bergmann, Jean Pierre; Mäder, Patrick
Recurrent autoencoder for weld discontinuity prediction. - In: Journal of advanced joining processes, ISSN 2666-3309, Bd. 9 (2024), 100203, S. 1-12

Laser beam butt welding is often the technique of choice for a wide range of industrial tasks. To achieve high quality welds, manufacturers often rely on heavy and expensive clamping systems to limit the sheet movement during the welding process, which can affect quality. Jiggless welding offers a cost-effective and highly flexible alternative to common clamping systems. In laser butt welding, the process-induced joint gap has to be monitored in order to counteract the effect by means of an active position control of the sheet metal. Various studies have shown that sheet metal displacement can be detected using inductive probes, allowing the prediction of weld quality by ML-based data analysis. The probes are dependent on the sheet metal geometry and are limited in their applicability to complex geometric structures. Camera systems such as long-wave infrared (LWIR) cameras can instead be mounted directly behind the laser to overcome a geometry dependent limitation of the jiggles system. In this study we will propose a deep learning approach that utilizes LWIR camera recordings to predict the remaining welding process to enable an early detection of weld interruptions. Our approach reaches 93.33% accuracy for time-wise prediction of the point of failure during the weld.



https://doi.org/10.1016/j.jajp.2024.100203
Girkes, Florian; Günther, M.; Rüger, Carolin; Bergmann, Jean Pierre; Töpfer-Kerst, Christian B.
An integrated approach to developing modular product families in the engineer-to-order sector. - In: Production at the leading edge of technology, (2024), S. 737-746

Nowadays, companies face challenges such as globalization, individualization and shorter product lifecycles, resulting in a constant stream of new product development processes (PDP). Modularized product families represent a powerful concept for reducing complexity and increasing resource efficiency in the PDP and beyond. Despite existing approaches and methods in the development of modular product families, there are deficits in the state of the art regarding their transfer and application to the engineer-to-order (ETO) sector, as well as for neutral indicator-based evaluation. Therefore, this paper derives a generic modularization procedure for the ETO sector and verifies it in an industrial use case. For this purpose, a heuristic swapping algorithm has been developed for grouping the components of a product family into clusters and enabling an objective mathematical evaluation. By integrating modular product structures into organizational processes, ETO manufacturers can strengthen their competitive position as well as increase their resource efficiency.



https://doi.org/10.1007/978-3-031-47394-4_72
Labus Zlatanovic, Danka; Bergmann, Jean Pierre; Baloš, Sebastian; Janjatoviâc, Petar; Rajnoviâc, Dragan; Šidjanin, Leposava
Influence of strain rate on metallurgical and mechanical properties of friction stir spot welded aluminium joints. - In: Advanced technologies and materials, ISSN 2620-147X, Bd. 48 (2023), 2, S. 37-43

Nowadays, the substitution of copper with aluminium is widely pursued in order to save weight and material costs, for battery components and wire connectors. Additionally, cost reductions can be further enhanced with effective reduction of energy consumption through efficient manufacturing. Therefore, friction stir spot welding as a solid-state welding technique is a potential choice with low energy demands and high joining performances. However, the joining of aluminium and its alloys with solid-state welding techniques is still a challenging task due to a persistent and chemically stable aluminium oxide layer formed at the sheets prior to the welding, due to the reaction between aluminium and atmospheric oxygen. In this paper, the influence of strain rate induced during friction stir spot welding process on the metallurgical, mechanical and electrical properties of friction stir spot welding of AA 5754-H111 was studied. The strain rate was calculated according to the rotational speed of the tool and the effective (average) radius and depth of the stir zone. It was observed that the specimens welded with a lower strain rate endured a 15 % higher average strain failure load compared to the specimens welded at a higher share rate. The microhardness profiles of the specimens obtained at low strain rates imply strain hardening mechanisms in the weld zone, while the microhardness of specimens welded at high strain rates expressed thermal softening. It was also found that the friction welded sheets, regardless of the strain rate, show increased electrical resistance compared to the base material, however, it decreases with an increase in strain rate. Microstructural analysis reveals a stress-induced metallurgical transformation in the narrow zone around the weld-faying interface.



https://doi.org/10.24867/ATM-2023-2-001
Matos Scotti, Fernando; Pudenz, Maximilian; Perrin, Sarah; Siewert, Erwan; Bergmann, Jean Pierre
Heat input control in horizontal lap joint welding through active wire preheating in GMAW-P. - In: Welding in the world, ISSN 1878-6669, Bd. 0 (2023), insges. 12 S.

In gas metal arc welding (GMAW) the arc power, in general, increases when the wire feed speed is increased. Thus, controlling heat input into the workpiece becomes a challenge, especially when trying to increase productivity. Metal transfer modes such as pulsed and controlled short circuit have been successfully applied to allow smooth metal transfer with relatively low energy. The effect of increasing the electrified length of the electrode or decreasing wire diameter in reducing current has been known for years. However, to some extent, this effect is limited to the physical conditions when using a large distance from contact tip to workpiece. To further increase melting efficiency and reduce arc power the torch presented in this paper includes a second electric circuit into GMAW to preheat the wire by ohmic heating before it reaches the main circuit. In this context, the objective of this work was to verify the effects of active wire preheating in GMAW in lap joint case in terms of electric signal behavior, thermal behavior in the plate, and weld bead formation. By increasing the preheating current, significant reduction in arc power was achieved. This reflects on the resulting weld by avoiding molten pool sagging, reducing fused area, silicate formation, and backside oxidation. The reduction in heat input resulted finally in a smaller heat affected zone which had a finer microstructure. In conclusion, the use of active wire preheating in GMAW expands the potential for increasing productivity and controlling heat input into the workpiece.



https://doi.org/10.1007/s40194-023-01654-9
Chen, Ting; Fu, Banglong; Shen, Junjun; Suhuddin, Uceu F. H. R.; Wiese, Björn; Huang, Yuanding; Wang, Min; Santos, Jorge F. dos; Bergmann, Jean Pierre; Klusemann, Benjamin
Application of novel constrained friction processing method to produce fine grained biomedical Mg-Zn-Ca alloy. - In: Journal of magnesium and alloys, ISSN 2213-9567, Bd. 0 (2023), 0, S. 1-14

In order to obtain Mg alloys with fine microstructures and high mechanical performances, a novel friction-based processing method, name as “constrained friction processing (CFP)”, was investigated. Via CFP, defect-free Mg-Zn-Ca rods with greatly refined grains and high mechanical properties were produced. Compared to the previous as-cast microstructure, the grain size was reduced from more than 1 mm to around 4 µm within 3 s by a single process cycle. The compressive yield strength was increased by 350% while the ultimate compressive strength by 53%. According to the established material flow behaviors by “tracer material”, the plastic material was transported by shear deformation. From the base material to the rod, the material experienced three stages, i.e. deformation by the tool, upward flow with additional tilt, followed by upward transportation. The microstructural evolution was revealed by “stop-action” technique. The microstructural development at regions adjacent to the rod is mainly controlled by twinning, dynamic recrystallization (DRX) as well as particle stimulated nucleation, while that within the rod is related to DRX combined with grain growth.



https://doi.org/10.1016/j.jma.2023.10.007
Girkes, Florian; Reimche, Maxim; Bergmann, Jean Pierre; Töpfer-Kerst, Christian B.; Berghof, Steffen
Aggregated production planning for engineer-to-order products using reference curves. - In: Production at the leading edge of technology, (2023), S. 642-651

The production of highly individualized engineer-to-order products has special characteristics that lead to a significant increase in the complexity of production planning and control. Therefore, aggregate resource planning is a dynamic and complex process that must always deliver reliable results. But without appropriate tools, these predictions can only be achieved with significant manual effort. Therefore, this paper presents a holistic method that predicts and schedules the required manufacturing resources for new customer orders based on a type representative by means of product modularization and data preparation of approximately identical historical manufacturing orders. This allows the actual processing status of the current customer project to be derived from the preplanning by means of a concurrent calculation in order to be able to initiate countermeasures at an early stage in the event of project delays and also to reduce the lead time of the customer order by preallocating the required production resources.



https://doi.org/10.1007/978-3-031-18318-8_64
Glaser, Marcus; Matthes, Sebastian; Riegler, Sascha Sebastian; Hildebrand, Jörg; Bergmann, Jean Pierre; Schaaf, Peter; Gallino, Isabella
Characterization of plastic-metal hybrid composites joined by means of reactive Al/Ni multilayers - evaluation of occurring thermal regime. - In: Engineering for a changing world, (2023), 4.3.056, S. 1-16

Present challenges in material science and joining technology are ever more subject to the desire for lightweight construction and engineering. Plastic-metal composites are suitable material combinations but also require the development and investigation of appropriate joining technologies. A particularly promising approach is the application of reactive multilayer foils. As an innovative method, these foils provide the possibility of flexible and low-distortion joining of dissimilar materials. The underlying reaction mechanism offers fast exothermic reaction propagation with well-known exothermic power output while the energy source is introduced directly into the joining zone. In this work, hybrid lap joints between semi-crystalline polyamide 6 and structured austenitic stainless steel X5CrNi18-10 were joined using reactive Al/Ni multilayer foils. The self-propagating reaction provides immediate temperatures that are well above the melting point of used plastic but decays rapidly after only a few milliseconds. To support ongoing investigations regarding composite formation, analysis of occurring thermal regime is in the focus of this work. Conducted experiments are supported by accompanying thermal simulation in ANSYS Workbench. Besides the estimation regarding sensitivity of thermal material parameters the evaluation of formed melting zone and resulting thermally influenced area is a central topic.



https://doi.org/10.22032/dbt.58913
Sennewald, Martin; Hasieber, Michael; Szallies, Konstantin; Bergmann, Jean Pierre
Influence of microstructure and microgeometry of the probe on friction stir welding of AA 6060 T66. - In: Engineering for a changing world, (2023), 2.1.114, S. 1-2

https://doi.org/10.22032/dbt.58854
Rohe, Maximilian; Hildebrand, Jörg; Bergmann, Jean Pierre
Investigation of a quantified sound probe for stud weld quality measurement with numerical simulation data. - In: Engineering for a changing world, (2023), 2.1.065, S. 1-8

Drawn arc stud welding with ceramic ferrules is a widely used joining process for joining sheet metal to studs, which can be threaded or sheared. During the welding process, various irregularities can occur which adversely affect the resulting mechanical properties. Arc blowing is one of the most common process defects. Arc blowing can result in an asymmetric weld bead which can increase the failure rate of the stud. An approach to stud testing is given in DIN ISO EN 14555. A sound probe carried out by an experienced welder provides qualitative information about the weld bead. The sound probe causes the stud to vibrate at its natural frequencies. If the eigenfrequencies can be calculated for each weld bead shape, the sound probe can be quantified. To this end, a new simulation approach is presented which allows the rapid calculation of the eigenfrequencies of the stud with different weld bead shapes. A data set is also generated and analyzed.



https://doi.org/10.22032/dbt.58853
Reimann, Jan; Rohe, Maximilian; Rauch, Alexander; Hildebrand, Jörg; Bergmann, Jean Pierre
Directed energy deposition-arc (DED-Arc) and numerical welding simulation as a method to determine the homogeneity. - In: Engineering for a changing world, (2023), 2.1.036, S. 1-17

This research presents a hybrid approach to for the prediction of the homogeneity of mechanical properties in 3D metal parts manufactured using directed energy deposition-arc (DED-Arc). DED-Arc is an additive manufacturing process which can offer a cost-effective way to manufacture 3D metal parts, due to high deposition rate of up to 8 kg/h. Regression equations developed in a previous study were used to predict the mechanical properties of a wall structure using only the cooling time t8/5 calculated in a numerical welding simulation. The new approach in this research paper contains the prediction of the homogeneity of the mechanical properties, especially hardness, in 3D metal parts, which can vary due to localized changes in t8/5 cooling time provoked by specific geometrical features or general changes in dimensions. In this study a method for the calculation of the hardness distribution on additively manufactured parts was developed and shown.



https://doi.org/10.22032/dbt.58852