Hot stamping also known as press hardening is one of the most important processes for manufacturing components with strengths exceeding 1500 MPa. The process combines heat treatment and forming in a single operation. Heating is typically carried out in gas-fired roller hearth furnaces and, due to the AlSi coating, requires slow heating times of 6-10 min. For alternative heating methods such as resistance heating, only uncoated sheet material can be used. However, during rapid heating rates of more than 100 K/s, the sheets suffer from scaling, which makes costly postprocessing necessary. This study demonstrates that by using a protective atmosphere of nitrogen and monosilane, a process environment can be created that corresponds to the oxygen concentration of an extreme high vacuum. At the same time, this process atmosphere enables the in-situ coating of uncoated sheets with the process heat required for hot stamping. Furthermore, it is shown that coating materials can be applied which form intermetallic phases.

Hydrogen-based energy systems are considered a key pillar of the energy transition, yet the cost-efficient, mass production of metallic bipolar plates (BPPs) for proton exchange membrane fuel cells (PEMFCs) remains challenging, as conventional processes are limited by comparatively long cycle times and forming-related instabilities. This paper investigates the rubber drawing process as a cost-efficient manufacturing method for metallic bipolar plates, proposed as an alternative to the commonly applied hydroforming process, analysing the influence of pressing force, rubber hardness and thickness, tool modifications for varying pressure distribution, and the suitability of additively manufactured tool dies made from Maraging Steel 1 (X3NiCoMoTi 18-9-5) or ceramic-filled UV resin. The results show that precise and stable tool guidance, as well as a well-adapted tool setup, are required to achieve reproducible component quality; targeted adjustments of process and rubber parameters improved channel dimensional accuracy, but revealed limited forming capability in certain areas. Furthermore, concavely and convexly modified rubber dies reduced component warping in specific directions, and steel dies exhibited higher precision and less distortion compared to ceramic-filled UV resin dies. These findings highlight the potential of the rubber drawing process for cost-effective production of bipolar plates, while identifying key parameters for further optimization toward industrial-scale manufacturing.

Hot stamping of manganese–boron steels is widely used in automotive manufacturing to produce ultra-high-strength components with tensile strengths exceeding 1500 MPa . Conventional industrial heating relies on gas-fired roller hearth furnaces, which require 5 – 10 min to reach austenitization and exhibit low energy efficiency . Resistance heating offers a compact and energy-efficient alternative, enabling heating rates above 100 K/s and full austenitization within seconds. However, rapid heating of uncoated steels leads to severe oxidation, and established coating systems such as AlSi are not designed for diffusion-controlled bonding within such short times . This study demonstrates that resistance heating in an XHV-adequate atmosphere – consisting of nitrogen and monosilane – suppresses oxidation while simultaneously enabling adhesion of a pre-laminated aluminum foil to the steel substrate. For coating preparation, 22MnB5 sheets were roughened by corundum blasting, cleaned, and laminated with an aluminum foil using a flat-die pressing tool. The pre-coated blanks were heated in a self-developed resistance-heating chamber, in which the oxygen concentration was reduced to an XHV-adequate level. Several heating profiles were investigated to determine suitable process windows for coating formation. The results show that resistance heating achieves austenitization within a few seconds, reducing heating times by more than an order of magnitude compared to furnace heating. The XHV-adequate atmosphere reliably prevents scale formation, enabling completely oxidation-free surfaces during rapid heating. Under these conditions, the laminated aluminum foil bonds uniformly to the substrate, forming a continuous coating layer. Metallographic cross-sections and SEM analyses confirm the formation of Al–Fe intermetallic phases at the interface, demonstrating robust metallurgical bonding suitable for subsequent hot stamping operations. Overall, the combination of resistance rapid heating and an XHV-adequate atmosphere provides a highly energy-efficient process route for hot stamping while offering an opportunity to integrate aluminum-based protective coatings directly into the heating step. This approach addresses the limitations of current furnace-based heating and coating technologies and opens a promising pathway toward more flexible, sustainable, and functionally integrated hot-stamping process chains.

In hot stamping, manganese-boron steel is heated above the austenitisation temperature and subsequently cooled at a rate of 27 K/s using a water-cooled process, resulting in lightweight components with ultra-high strength that enhance passenger safety, such as A- or B-pillars. Industrial heating takes place in roller hearth furnaces, where the sheet metal is heated up to 950 °C within 6 to 10 minutes and the AlSi coating bonds with the base material to protect it from scaling. Resistance heating is an alternative heating method. The direct current flow through the sheet enables heating rates of more than 100 K/s and heats the sheet in less than 10 seconds. This rapid heating also improves the mechanical properties by reducing the growth of coarse grains. However, the AlSi coating is not designed for such rapid heating, as there is not enough time for the diffusion layer to form. However, an XHV (extreme high vacuum)-adequate protective atmosphere with nitrogen and silane offers an alternative for scale-free heating without coatings. This process atmosphere binds oxygen, effectively preventing scale formation.

Draw-bending technology enables the production of load-adapted parts for lightweight construction applications. Its flexibility is particularly advantageous for small series production. In this study, the feasibility of introducing additional secondary forming elements to increase bending stiffness is investigated using finite element simulation. For this purpose, different bead geometries are designed and analysed by a numerical model of the draw-bending process. The process is evaluated based on the drawing force, the equivalent plastic strain and sheet thickness reduction. Finally suitable bead geometries are selected for future experimental investigations. The analysis shows that the challenge in optimisation lies between achieving the desired highest possible bead, which increases the stiffness and dimensional accuracy of the resulting profile, and the technological limitations due to the formability of the material. Under the current process conditions, the choice is limited to beads with a height of less than 20 mm. This study provides a basis for future research to optimise the bead design and improve the process parameters in the manufacturing process.

Zur Reduktion von Reibung und Verschleiß bei der Umformung von Aluminiumblechen wurden Werkzeugoberflächen aus einem Gusswerkstoff (EN-GJS-700–2) chemisch oxidiert und elektrochemisch phosphatiert. Die phosphatierten Schichten reduzierten den Reibwert um bis zu 47,62 % im Vergleich zu unbeschichteten Oberflächen. Allerdings wurde eine hohe Adhäsion des Aluminiums an der Werkzeugoberfläche festgestellt.

The automotive industry has high demands for multi-material structures in achieving lightweight design, efficient body construction and enhanced functionality. These structures capitalize on the favorable mechanical properties and reduced weight of such combinations, especially when metal and plastic are integrated to create a synergistic effect. This research paper outlines the advancement of a hot-stamp and an compression tool to facilitate a thermally assisted compression process. This process enables the seamless joining of GMT (Glass Mat reinforced Thermoplastics) and 22MnB5 steel without the need for additional bonding agents.In the initial step of the process, a hot-stamping tool is utilized to fabricate cap profile components. Afterwards a combined compression and joining process of the GMT takes place. Through adhesion, the GMT material bonds to the rough surface of the AlSi-coated 22MnB5, enabling the removal of the final component.The influence of process parameters was assessed through static and dynamic tests conducted on demonstrator components. Overall, it was determined that the introduction of a GMT stiffening structure leads to improvements in both the static and dynamic properties of the component so a reduction of the steel thickness of the structure can be carried out. This reduction in thickness is accompanied by a decrease in the mass of the test structure, while maintaining or even enhancing its static and dynamic properties. Further weight savings are possible through additional component and process optimization.

Manufacturing deep drawing parts, e. g. car bodies, method planning as a step of development is used for designing and harmonising the forming operations. The result of method planning is a process which is as stable as possible to produce a part of a fix geometry. The ability to vary the drawing depth can be an advantage to develop a great number of variants at a small amount of time. However, different drawing depths make it difficult to set up a stable process. An AI model can be trained with process data and later be used for assisting the setup process for production. This paper deals with the method planning of a multistage process by means of a commercial simulation software to produce an exemplary part. A typical process of method planning serves as a template for the considerations in this paper. First, a preliminary sheet metal pre-cut and the number and sequence of operations are defined. Secondly, the arrangement of the active die surfaces, the design of the punch and the blank holder are determined. Finally, the process limits are determined as a function of various parameters.

Multi-material structures in the automotive industry offer significant potential for lightweight design, body construction and functional integration, thanks to their advantageous mechanical properties and lower structural weight. Specifically, combining metal and plastic is a widely employed approach to improve the overall performance of the final product compared to structures made from a single material. This paper describes an alternative approach to join metal and fibre-reinforced plastic (FRP) during the forming process (in-mould assembly). This enables the direct integration of metal structures into FRP components. To this end, a manufacturing method is being developed with which a metal insert is integrated into the FRP by means of extrusion moulding. This doubles the available joining surface compared to bonding the metal reinforcement. The project is based on the hypothesis that the integrated metal inserts both reinforces the component itself and improves the connection to surrounding structures and thus the maximum force transmission. In this regard, investigations into the adhesion behaviour between FRP and metal are shown and the tool concept is presented.

In hip arthroplasty, relative movements between the femoral stem and bone can lead to implant loosening, resulting in extensive bone loss. Acoustic emission (AE) analysis is a promising technique for a nondestructive and noninvasive detection of these relative movements. To develop such a detection method, in vitro investigations using piezoelectric AE sensors on implant stems in artificial or human femora are required to characterize the AE signals induced by loosening. This study aims to identify suitable coupling materials to bridge the gap between the planar AE-sensor surface and the exposed freeform surface of the femur. Four coupling materials, both synthetic and natural, with acoustic properties similar to human soft tissue were investigated for signal attenuation and repeatability between tests. The synthetic materials demonstrated better inter-sample repeatability. One synthetic material exhibited higher flexibility, enabling better adaptation to the sensor and resulting in significantly lower signal attenuation.

The following article is dedicated to the presentation of a developed filter algorithm for noise suppression in Acoustic Emission Analysis. The focus of the application is in the context of loosening diagnostics for hip endoprostheses. The aim of the study was to implement an algorithm capable of effectively filtering noise from acoustic signals in order to improve the detection of implant loosening. The algorithm is based on several filtering techniques, including the IIR notch filter. This ensures optimization of signal quality and accurate feature identification. The code was evaluated using experimental data on acoustic emission events. The results show that the code is successfully able to minimize the noise and to identify the relevant signals for loosening diagnostics. Further applications can be derived from the results of the applied algorithm, where quality control or real-time monitoring of processes is of crucial importance. The precise detection of weak signals opens up the possibility of transferring the filter algorithm to metal forming processes.

Abstract The automotive industry holds great promise for multi-material structures in achieving lightweight design, efficient body construction and enhanced functionality. These structures capitalize on the favorable mechanical properties and reduced weight of such combinations, especially when metal and plastic are integrated to create a synergistic effect. This research paper outlines the advancement of a hot-stamp and an extrusion tool to facilitate a thermally assisted extrusion process. This process enables the seamless joining of GMT (Glass Mat reinforced Thermoplastics) and 22MnB5 steel without the need for additional bonding agents. In the initial step of the process, a hot-stamping tool is utilized to fabricate cap profile components. Afterwards a combined extrusion and joining process of the GMT takes place. Through adhesion, the GMT material bonds to the rough surface of the AlSi-coated 22MnB5, enabling the removal of the final component. The influence of process parameters was assessed through static and dynamic tests conducted on demonstrator components. Overall, it was determined that the introduction of a GMT stiffening structure leads to improvements in both the static and dynamic properties of the component so a reduction of the steel thickness of the structure can be carried out. This reduction in thickness is accompanied by a decrease in the mass of the test structure, while maintaining or even enhancing its static and dynamic properties. Further weight savings are possible through additional component and process optimization.

In the aviation industry, a large number of processes are not digitalised. Simultaneously, many special processes are used in production, such as incremental bending. In order to model and efficiently design multi-stage processes with methods such as FEM, automation and linking of the individual simulations are necessary. This paper therefore presents a method for automatically simulating and evaluating a complete incremental bending process with 24 strokes in LS-Dyna using a Python framework with cfiles. The final validation of the force–displacement relationships and inner radii of the generated scaled fuselage shell show high prediction accuracies of about 90%. Thus, the presented methodology enables a FEM-based process design of incremental bending in the aviation industry.

Manufacturers like Airbus have strict specifications concerning the process sequence of fuselage shell forming. Coating may only take place after forming, because conventional processes induce large deformation which could cause coating failure. A novel incremental bending process known as Deharde Polygon Forming((R)) (DPF (R)), has the potential to challenge existing process sequence restrictions due to lower deformations. Thus, it is to be investigated if precoated sheets can be formed by DPF (R) with regard to the coating properties. Correspondingly, in the scope of this work, starting from the initial state of coated EN AW - 2024 - T351, the changes of the Seevenax-313-81 coating after preloading were analysed. Therefore, three different strain states were induced by Marciniak tests and scaled fuselage shells were produced by DPF (R) from which specimen were obtained. Afterwards, the evolution of coating properties such as hardness, Young's modulus, elastic and plastic behaviour and friction coefficient were investigated by scratch and indentation tests with a Triboindenter TI 950. In parallel, the formed specimens were analysed for coating failure by using integrated optics. It was found, that the pre-stretched specimens by Marciniak tests and scaled DPF (R) do not undergo significant changes in the application characteristics of the coating. However, the former was found to have cracks in the coating. In contrast, for scaled DPF (R) fuselage shells, where compressive stresses are induced by contact with the tool or spring steel package, no failure were detected in the surface of the coating. The results indicate potential for flexibilization of the process chain regarding forming and coating.

Verzinkte Bleche sind für den Korrosionsschutz von Bauteilen unverzichtbar. Die Temperierung mittels Rollenherdöfen kann hinsichtlich Qualität und Effizienz verbessert werden. Nachgeschaltete Oberflächenbehandlungen sind oft nötig, zum Beispiel für homogenen Lackauftrag. Das Institut für Umformtechnik und Umformmaschinen (IFUM) erforscht neue Temperierungsstrategien mittels Widerstandserwärmung, die schnelle Aufheizraten, hohe Wirkungsgrade und spezifische Rauheiten ermöglichen.

The challenge implementing magnesium sheets as a lightweight material is to manufacture sheets with an acceptable formability at room temperature and sheet components with a suitable strength. The aim of this work is qualifying suitable alloys and their manufacturing process in a way that precipitation hardening is enabled after the final forming process. The precipitation morphology and the rapid solidification obtained by twin roll casting process are used to find an optimum microstructure for deep drawing and to increase the strength of the formed component by heat treatment. The results show that magnesium sheets made from Mg-Zn-Al-Ca exhibit good forming properties even after rolling from the slab, as well as an increase in hardness after a suitable heat treatment. The production route of sheets via twin roll casting process exhibits higher increases in both ductility of the sheets and hardness after heat treatment compared to the production route via ingot-rolling. This paper presents results of rolling experiments with different feedstock of Mg-Zn-Al-Ca alloys, the microstructures and textures, as well as their mechanical properties and Erichsen values. In addition, various heat treatments were carried out to increase hardness. The second part of the paper deals with the development of a suitable heated deep-drawing tool and shows the heat distribution in the tool as well as first results of the deep-drawing tests.

The use of fiber-reinforced plastics (FRP) is essential to meet future lightweight construction requirements in the automotive industry. Therefore, resource- and cost-saving as well as innovative manufacturing processes are needed, which enable large-scale series production. One example is the manufacturing of such components from glass mat-reinforced thermoplastics (GMT) and unidirectional fiber tapes (UD tapes) by combined compression molding and thermoforming. It may be necessary to insert multiple GMT pieces into the mold to improve mold filling and extend the process limits. In the forming process, the different material fronts of the GMT blanks collide and are joined by fusing and consolidating the matrix material of the composite. This area is called the weld line. In this paper, the influence of the weld line on the tensile strength of the workpieces was investigated. First, two GMT blanks were placed next to each other and formed in a heated plate mold. On the basis of tensile specimens that were cut across the weld line, it was found that the weld line causes a marked decrease in tensile strength. In further investigations, the UD tapes were added into the process. Due to the reinforcement of the UD tapes, the decrease in tensile strength due to the weld line was significantly reduced.

The quality of deep-drawn parts is subject to uncontrollable fluctuations, triggered by material property variations and process deviations, which occur despite extensive quality controls along the entire process chain. Monitoring and controlling the draw-in of the sheet material—which is an indicator of a faultless deep drawing process—would allow for a significant increase in process robustness. However, this requires sensor systems suitable for the industrial environment, which so far do not exist. This paper presents a newly developed inductive sensor in thin-film technology for measuring the flange draw-in. The sensor was designed with the aid of finite-element-analysis and then manufactured using thin-film processes. After integration into a deep-drawing tool, the system was tested and validated. Afterwards, the detection of typical deep-drawing defects was investigated. It was demonstrated that the sensor system can reliably detect both cracks and wrinkles as well as the time at which they occur.

Industrial product development today is faced with the challenge of achieving shorter creation cycles to keep up with international competition. This causes constantly changing requirements for the geometry of the components and thus for the used forming tools. These tools must be designed much faster so that customer requirements are met quickly, which is feasible through a parametric CAD design. As part of a cooperative research project involving the GFaI and the IFUM, a fully parametric CAD model for a sheet-bulk metal forming process was developed. With this tool it is possible to produce cylindrical components with internal and external gearing by combined sheet and bulk forming operations. For this purpose, the CAD model of the tool system is divided into different assemblies. Each assembly consists of various components which relate to each other. Furthermore, the dependencies between the assemblies were built up parametrically via global constrains. An initial structure of the CAD model including constraints is described in this paper. In addition, various process limits are determined by means of experimental tests and calculations. In the first stage of the forming process, blanks are deep-drawn into cups. Due to the geometry of the gears, round cup forming tests were conducted to examine the drawing ratio for different materials (DC04, DP600 and HC260LA). The characteristic values are converted into parameter limits for the new CAD model. Thus, the forming tool can be designed depending on the material used and the required gear size, which can reduce the development time in the future.