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Grätzel, Michael; Sieber, Felix; Schick-Witte, Konstantin; Bergmann, Jean Pierre;
Advances in friction stir welding by separate control of shoulder and probe. - In: Welding in the world : the international journal of materials joining.. - Berlin : Springer, ISSN 1878-6669, Bd. 65 (2021), 10, S. 1931-1941

Friction stir welding (FSW) has developed into a reliable and increasing used industrial joining technology. Various tool configurations can be used for FSW, each of which has advantages and challenges. State-of-the-art FSW employs various tool configurations, including the conventional, the stationary shoulder, and the dual-rotational configuration which is characterized by separate control of shoulder and probe. In this study, an innovative method to combine various tool configurations was developed by a novel FSW spindle stack construction. With an additional servomotor, existing FSW systems can be extended by separate control of shoulder and probe so that varying rotational speeds and rotational directions can be set. This allows enhanced possibilities (a) to adjust frictional heat generation and (b) to apply several tool configurations. The main advantages of this enhanced type of FSW are demonstrated in three ways: increased weld penetration depth, reduction of undesirable machine vibrations, and the combination of varying tool configurations such as stationary shoulder and conventional FSW. The investigations were carried out with 2-mm EN AA 5754 H22 sheets and performed on a robotized FSW setup.



https://doi.org/10.1007/s40194-021-01136-w
Günther, Karsten; Bergmann, Jean Pierre;
Experimental approach to determine the impact of the droplet transfer mode on the degradation of fused tungsten carbides during GMAW. - In: International journal of refractory metals & hard materials. - Amsterdam [u.a.] : Elsevier Science, ISSN 0263-4368, Bd. 101 (2021)

The application of fused tungsten carbides (FTCs) in nickel-based alloys is important for improving the wear resistance of tooling equipment in the mining industry. However, FTCs are thermally unstable and will dilute under excessive energy input during welding. The parameters affecting dilution in this context are diverse and not yet completely understood. To date, the existing scientific literature focuses on the impact of the melt bead characteristics to explain the degradation during gas metal arc welding (GMAW). The degradation-promoting influence of the droplet transfer mode has not yet been considered. A methodology was developed to experimentally quantify the dependence of the degradation kinetics of FTCs on the droplet transfer mode. The established experimental model demonstrated that the globular transfer mode leads to increased degradation of FTCs in comparison to that of the short-arc mode, which can be attributed to the higher process power and hence higher droplet temperature. In this context, the quantifiable impact of the droplet transfer mode was determined.



https://doi.org/10.1016/j.ijrmhm.2021.105692
Reimann, Jan; Hammer, Stefan; Henckell, Philipp; Rohe, Maximilian; Ali, Yarop; Rauch, Alexander; Hildebrand, Jörg; Bergmann, Jean Pierre;
Directed energy deposition-arc (DED-Arc) and numerical welding simulation as a hybrid data source for future machine learning applications. - In: Applied Sciences : open access journal.. - Basel : MDPI, ISSN 2076-3417, Bd. 11 (2021), 15, S. 1-16

This research presents a hybrid approach to generate sample data for future machine learning applications for the prediction of mechanical properties in directed energy deposition-arc (DED-Arc) using the GMAW process. DED-Arc is an additive manufacturing process which offers a cost-effective way to generate 3D metal parts, due to its high deposition rate of up to 8 kg/h. The mechanical properties additively manufactured wall structures made of the filler material G4Si1 (ER70 S-6) are shown in dependency of the t8/5 cooling time. The numerical simulation is used to link the process parameters and geometrical features to a specific t8/5 cooling time. With an input of average welding power, welding speed and geometrical features such as wall thickness, layer height and heat source size a specific temperature field can be calculated for each iteration in the simulated welding process. This novel approach allows to generate large, artificial data sets as training data for machine learning methods by combining experimental results to generate a regression equation based on the experimentally measured t8/5 cooling time. Therefore, using the regression equations in combination with numerically calculated t8/5 cooling times an accurate prediction of the mechanical properties was possible in this research with an error of only 2.6%. Thus, a small set of experimentally generated data set allows to achieve regression equations which enable a precise prediction of mechanical properties. Moreover, the validated numerical welding simulation model was suitable to achieve an accurate calculation of the t8/5 cooling time, with an error of only 0.3%.



https://doi.org/10.3390/app11157075
Reimann, Jan; Henckell, Philipp; Ali, Yarop; Hammer, Stefan; Rauch, Alexander; Hildebrand, Jörg; Bergmann, Jean Pierre;
Production of topology-optimised structural nodes using arc-based, additive manufacturing with GMAW welding process. - In: Journal of civil engineering and construction. - Reading : Tech Reviews Ltd, ISSN 2051-7777, Bd. 10 (2021), 2, S. 101-107

The desire to generate a stress optimised structural node with maximum stability is often coupled with the goal of low manufacturing costs and an adapted and minimal use of material. The complex, three-dimensional free-form structures, which are created by means of topology-optimisation, are only partially suitable for conventional manufacturing. The wire arc additive manufacturing (WAAM), by means of arc welding processes, offer a cost-effective and flexible possibility for the individual production of complex, metallic components. Gas metal arc welding (GMAW) is particularly suitable to produce large-volume, load-bearing structures due to build-up rates of up to 5 kg/h. The generation of strength and stiffness adapted support structures by means of the numerical simulation method of topology-optimisation was investigated in this study to generate topology-optimised structural nodes. The resulting node is transferred into a robot path using CAD/CAM software and manufactured from the filler material G4Si1 using WAAM with the GMAW process. Based on the boundary conditions of the WAAM process, the path planning and thus the manufacturability of the topology-optimised supporting structure nodes is evaluated and verified using a sample structure made of the welding filler material G4Si1. Depending on the path planning, an improvement of the mechanical properties could be achieved, due to changes in t8/5 times.



https://doi.org/10.32732/jcec.2021.10.2.101
Schmidt, Leander; Junger, Christina; Schricker, Klaus; Bergmann, Jean Pierre; Notni, Gunther;
Echtzeitfähige Ansätze zum Monitoring der dehnungsfeldbasierten Spaltentstehung und resultierender Nahtqualität beim Laserstrahlschweißen. - In: Innovative Verfahren der Lasermaterialbearbeitung. - Düsseldorf : DVS Media GmbH, (2021), S. 44-55

Seibold, Marc; Friedmann, Hannes; Schricker, Klaus; Bergmann, Jean Pierre;
Regelstrategien für die Echtzeit-Leistungsregelung beim gepulsten Laserstrahlschweißen von Aluminium-Kupfer-Mischverbindungen. - In: Innovative Verfahren der Lasermaterialbearbeitung. - Düsseldorf : DVS Media GmbH, (2021), S. 33-42

Balos, Sebastian; Howard, Daniel; Brezulianu, Adrian; Labus Zlatanovic, Danka;
Perforated plate for ballistic protection - a review. - In: Metals : open access journal.. - Basel : MDPI, ISSN 2075-4701, Bd. 11 (2021), 4, S. 1-18

In recent years, the interest of the scientific community in perforated plates for ballistic protection has increased. Perforated plates do not represent protection by themselves, rather, they are used in the armour systems of armoured vehicles, in conjunction with base armour, since they are intended to induce bend stresses, where a penetrating core fracture occurs. The fragments are subsequently stopped by base armoured vehicle armour. Although for the first time used several decades ago, perforated plates are found to be attractive even today. The main reason is the combination of very convenient properties. Besides high mass effectiveness, they possess a high multi-impact resistance, since their perforations arrest cracks. Therefore, a relatively wide array of materials is suitable for perforated plate fabrication, ranging from alloy steel to some types of cast iron. Being made of metallic materials, raw material costs are relatively low compared to ceramics or composite materials, making them very attractive for present and future armoured vehicles. Finally, armour system consisting of a perforated plate and base plate at some distance, reduce the effectiveness of both shaped charge jets and act as blast mitigators.



https://doi.org/10.3390/met11040526
Hellwig, Peter; Schricker, Klaus; Bergmann, Jean Pierre;
Investigations of the absorption front in high-speed laser processing up to 600 m/min. - In: Applied Sciences : open access journal.. - Basel : MDPI, ISSN 2076-3417, Bd. 11 (2021), 9, S. 1-16

High processing speeds enormously enlarge the number of possible fields of application for laser processes. For example, material removal for sheet cutting using multiple passes or precise mass corrections can be achieved by means of spatter formation. For a better understanding of spatter formation at processing speeds of several hundred meters per minute, characterizations of the processing zone are required. For this purpose, a 400 W single-mode fiber laser was used in this study to process stainless steel AISI 304 (1.4301/X5CrNi18-10) with speeds of up to 600 m/min. A setup was developed that enabled a lateral high-speed observation of the processing zone by means of a glass plate flanking. This approach allowed for the measurement of several dimensions, such as the penetration depth, spatter formation, and especially, the inclination angle of the absorption front. It was shown that the loss of mass started to significantly increase when the absorption front was inclined at about 60˚. In combination with precise weighings, metallographic examinations, and further external process observations, these findings provided an illustration of four empirical process models for different processing speeds.



https://doi.org/10.3390/app11094015
Middeldorf, Klaus; Aumüller, Dominik; Bergmann, Jean Pierre; Mann, Samuel; Sharma, Rahul; Reisgen, Uwe;
Schweißtechnik 4.0: digitalisierte vernetzte schweißtechnische Fertigung - Konzepte und Anwendungen, Teil 1. - In: Schweissen und Schneiden. - Düsseldorf : DVS-Media GmbH, ISSN 0036-7184, Bd. 73 (2021), 3, S. 146-149

Industrie 4.0" ist für kleine und mittelständische Unternehmen (KMU), die sich mit dem Fügen, Trennen und Beschichten auskennen, künftig von großer Bedeutung. Dabei geht es aber weniger darum, konkrete Produktions-, Fertigungs- oder Schweißprozesse zu beschreiben, sondern kritisch zu prüfen, wo in kleinen und mittelständischen Unternehmen Lücken hinsichtich Industrie 4.0 bestehen und wie sich diese schließen lassen. Denn nur so können Unternehmen langfristig den bestehenden, digitalen Vorsprung für sich nutzen. Aus diesem Grund beschäftigt sich die Arbeitsgruppe "Industrie 4.0" im DVS aktuell mit diesem Thema. Sie stößt die Diskussion über die Digitalisierung in der Schweißtechnik an und initiiert unter dem Titel "Vom Fortschritt profitieren: Industrie 4.0 in der Schweißtechnik" eine Serie von Fachbeiträgen, die - mit der vorliegenden Ausgabe beginnend - in dieser Zeitschrift veröffentlicht werden.



Middeldorf, Klaus; Aumüller, Dominik; Bergmann, Jean Pierre; Mann, Samuel; Sharma, Rahul; Reisgen, Uwe;
Schweißtechnik 4.0: digitalisierte vernetzte schweißtechnische Fertigung - Konzepte und Anwendungen, Teil 2. - In: Schweissen und Schneiden. - Düsseldorf : DVS-Media GmbH, ISSN 0036-7184, Bd. 73 (2021), 4, S. 235-238

"Industrie 4.0" ist für kleine und mittelständische Unternehmen (KMU), die sich mit dem Fügen, Trennen und Beschichten auskennen, künftig von großer Bedeutung. Dabei geht es aber weniger darum, konkrete Produktions-, Fertigungs- oder Schweißprozesse zu beschreiben, sondern kritisch zu prüfen, wo in kleinen und mittelständischen Unternehmen Lücken hinsichtlich Industrie 4.0 bestehen und wie sich diese schließen lassen. Denn nur so können Unternehmen langfristig den bestehenden, digitalen Vorsprung für sich nutzen. Aus diesem Grund beschäftigt sich die Abreitsgruppe "Industrie 4.0" im DVS aktuell mit diesem Thema. Sie stößt die Diskussion über die Digitalisierung in der Schweißtechnik an und initiiert unter dem Titel "Vom Fortschritt profitieren: Industrie 4.0 in der Schweißtechnik" eine Serie von Fachbeiträgen in dieser Zeitschrift, die mit dem zweiten Teil in der vorliegenden Ausgabe fortgesetzt wird.