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Publication Access status: Open Access , Konzeptionierung und kinematische Optimierung einer Mehrlenkertorsionsachse für den Einsatz in einem batterieelektrischen Fahrzeug(2026)In this thesis, the concept of a new type of rear axle, the so-called multi-link torsion axle, is developed. By integrating a reversed twist-beam structure into a longitudinally orientated Watt’s linkage, the position of the space-limiting cross beam is decoupled from the original longitudinal instant centre. This opens up an increased, homogenous package space in the vehicle underbody, which can be allocated to the traction battery when used in a battery electric vehicle. At the same time, a longitudinal instant centre in front of the wheel, and thus also positive anti-lift, can be ensured by the alignment of longitudinal links in side view. Once the basic topology of the mechanism has been defined, it is optimised regarding the hardpoints. For this purpose, multiple analytical calculation approaches of the motion are presented and then integrated into an optimisation algorithm. The hardpoints are optimised with respect to global and local package boundary conditions, as well as kinematic and elastic requirements and target values. These refer to typical suspension characteristics found in literature, as well as characteristics that can occur specifically with the given mechanism. The resulting properties are then compared with a conventional twist-beam axle at both the suspension and full-vehicle level. For this purpose, this new type of rear axle is installed in a demonstrator vehicle loaded with ballast masses and tested on a proving ground. Full-vehicle simulations are also used for better interpretation. These experiments focus particularly on the vertical dynamic properties of the new axle with respect to comfort for different road excitations as well as pitching under braking. The results obtained also allow conclusions to be drawn about the previously defined suspension characteristics. With the results of this test series, it is possible to conclude whether the new axle concept is within a tuneable range in terms of driving dynamics.Source Type:Doctoral ThesisSeries:Siegener Schriftenreihe AutomobiltechnikVolume number:133 2 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , Mehrlenker-Torsionsachse – Modellierung, Entwicklung und Erprobung einer bauraumsparenden Verbundhinterachse für eine verbesserte Batterieintegration in BEVs der Kleinwagenklasse(2025)The integration of large battery packs into battery electric vehicles poses a particular challenge in the compact vehicle class, as available packagespace is limited by conventional axle designs such as the twist beam axle. To address this issue, the Multi-Link Torsion Axle (MLTA) was developed at the Institute of Automotive Lightweight Design. Its novel kinematic behavior enables optimized vehicle integration and creates additional space for the battery package. This work deals with the modeling, development, and experimental evaluation of the MLTA, with a focus on its elastokinematic behavior. For this purpose, an MBS solver was developed that is capable of modeling and analyzing both the kinematics and elastokinematics of suspension systems. Based on this solver, an MBS model of the MLTA was created. In the next step, a prototype axle was designed, built, and integrated into a test vehicle. The experimental evaluation included KnC-measurements, objective driving tests, and subjective evaluation by experienced test drivers and untrained everyday drivers. For comparison, a production vehicle equipped with additional masses was used to emulate the characteristic mass and center-of-gravity properties of a BEV. The KnC results confirm the potential of the MLTA. Kinematic advantages were observed particularly in wheel-center recession and anti-lift behavior. Weaknesses were found in camber compliance due to deviations of the prototype bushings from the target specifications. However, simulation results show that the desired compliance behavior can be achieved if the specified bushing characteristics are met. Objective driving tests show high agility and a significantly reduced longitudinal acceleration during obstacle crossing compared to the reference suspension. Compared to the reference axle, the MLTA received lower ratings in the subjective evaluation, clearly indicating the need for series-level tuning in future development.Source Type:Doctoral ThesisSeries:Siegener Schriftenreihe AutomobiltechnikVolume number:119 8 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , Lightweight concept design of economical FRTP-metal multi-material vehicle doors(2021)The vehicle door, as a major steel-intensive closure, can achieve a certain degree of weight-saving potential by the use of lightweight materials and new design principles. Due to the different stiffness and strength requirements on different areas of vehicle doors under static and crash loading conditions, multi-material construction can be one of the most effective ways to achieve lightweight design with minimal additional cost. This work illustrates an approach for the design of economical lightweight multi-material vehicle door concepts based on a market-available steel reference, while considering typical static and crash loading cases. An innovative door structure is introduced that includes a major load-bearing ring structure and a highly function-integrated inner panel. The structure incorporates economical lightweight materials, such as aluminum, long-fiber thermoplastics, and unidirectional tapes, and corresponding mass-production-oriented manufacturing methods. Anisotropy analysis under different loadings guarantees an effective use of unidirectional tapes. Topology and parameter optimizations provide design suggestions for rib structures of long-fiber-reinforced thermoplastics. The final door concepts achieve ca. 20% weight reduction and comparable mechanical performance compared to the steel reference door. Especially for the crash loading case, an innovative component development method is used to validate the final door concepts, which rebuilds the crash behavior close to the full-vehicle scenario with limited surrounding components.Source Type:Doctoral ThesisSeries:Siegener Schriftenreihe AutomobiltechnikVolume number:84 4 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , Crash simulation of woven fabric thermoplastic composites(2021)Fiber composite materials are frequently being used in automotive industry to meet the growing demand for fuel efficient passenger cars. Woven fabric thermoplastic composites materials provide high stiffness-to-weight, strength-to-weight and energy absorption-to-weight ratio at affordable mass production cost. To use these materials in structural components of passenger cars, the crashworthiness requirements must be met. To fulfill the crashworthiness requirements, dynamic FEM simulations are carried out as part of the product development process. However, the composite material behavior under dynamics loads is not fully understood. Furthermore, the state-of-the-art material models fail to predict the crash behavior of woven fabric composite material accurately which leads to under-utilization of the weight-saving-potential of these materials. The goal of this work was to develop an improved material model for the dynamics simulation of woven fabric thermoplastic composites. The material model must be independent of non-physical parameters and all parameters could be determined experimentally. In the framework of this work, the mechanical material properties were measured experimentally. The test data was used to identify discrepancies in state-of-the-art continuum damage mechanics material models. The in-plane shear damage behavior was improved and effects of tensile and compression strain on the shear behavior were quantified. High-speed test data was used to incorporate the strain rate-dependency in material model. The improved material model was implemented as user-material subroutine and simulation results were validated with component level drop tower crash tests. The potential for further improvements was identified by proposing the method to implement the measured size effect on the strength of materials. Stress-strain transformation was used to determine the failure points under multiaxial stress state. Finally, the viability of cohesive zone modeling approach was investigated to model the quasi-static axial crushing.Source Type:Doctoral ThesisSeries:Siegener Schriftenreihe AutomobiltechnikVolume number:71 1 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , Entwicklung eines neuen Widerstandsnietschweißverfahrens zur flexiblen und wirtschaftlichen Fertigung der Karosserie in der Al-Stahl-Mischbauweise(2020)Various vehicles are currently being designed modularly and manufactured on the same assembly line. The manufacturing facilities such as spot welding system and the associated robots are being reused across vehicle generations to reduce investment costs. A car body in Al-steel mixed construction is a promising solution to meet the lightweight requirements. However, the existing mechanical joining technologies, such as self-piercing riveting (SPR), punch rivet etc., due to their process restrictions, do not meet the flexibility and economy requirements for producing the car bodies with Al-steel-mixed and steel construction at the same time. Therefore, it is necessary to develop a new joining technique that will make it possible to reuse the existing spot welding equipment for manufacturing the Al-steel mixed body-in-white structure parallel to the pure steel body. Thus, a novel joining method “rivet resistance spot welding (RRSW)” was developed in this dissertation for producing an Al-steel mixed body-in-white structure. The RRSW works by using a steel rivet as a welding adapter in the Al sheet part. The steel rivet is pressed into the Al sheet part during its forming process and the rivet deformation makes a form-interlock between steel rivet and Al sheet part. The steel rivet is then welded to the adjacent steel parts by spot welding. The rivet geometry and the die shape were designed and optimized by the FEM-simulation. With the optimized rivet and the die, a good form-interlock between the Al sheet part and the steel rivet can be realized. The appropriate welding parameters, including the welding current, electrode force, and the shape of the electrode cap, with which the welding point between the steel sheet and rivet can be produced without Al melting, were determined by the welding test. The comparison of mechanical test results between RRSW- and SPR-joints has shown that the RRSW joints have a higher static strength than SPR in many material combinations. The contact corrosion can also be avoided by the gap between Al and steel set by RRSW. The RRSW process was tested in the production of an Al-steel-mixed partial roof structure to check its process capability. The pressing tools for forming Al partial roof and the compact punching heads for pressing the steel rivets into the roof were developed and built. With these tools, many steel rivets were inserted simultaneously into the Al partial roof in a single step, and thus the cost-effectiveness of RRSW was ensured. The Al partial roof with inserted steel rivets was then welded to the steel roof bow via a robot-guided welding gun under the real boundary conditions of the assembly line. The process capability of RRSW was thus successfully proven by testing with the Al-steel partial roof structure. Besides, the RRSW joint was modelled with a substitute model MAT_100_DA in LS-DYNA in the crash simulation and validated by tests, which enables the further application of RRSW in the car body. In summary, with the joining method “RRSW” described in the dissertation, the body in white structure in both Al-steel mixed and steel construction can be manufactured by using the existing spot welding equipment on the same assembly line without any additional changes of manufacturing facilities and the high investment costs for new joining equipment can be avoided.Source Type:Doctoral ThesisSeries:Siegener Schriftenreihe AutomobiltechnikVolume number:56 5 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , Leichtbaupotenziale im Fahrwerk – Multi-Material-Design durch simultane Umformung von Metallblechen und Urformung von langfaserverstärkten Thermoplasten (LFT)(2020)Modern vehicle construction follows two overriding goals with customer- and market-related requirements for comfort and safety on the one hand and the lowest possible fuel consumption and compliance with emission limits on the other hand. Accordingly, lightweight construction based on materials must, as a supporting pillar within vehicle development, consider both the safety aspect and the reduction of vehicle mass and thus contribute to the reduction of fuel consumption and pollutant emissions. In addition to the development of new, high-strength steel grades produced by hot forming to reduce sheet thicknesses and mixed construction methods with aluminum and magnesium, fiber-reinforced plastics are also increasingly being used. The application of this so-called multi-material construction method down to the component level simultaneously results in a demand for economic and combined manufacturing processes for hybrid components made of plastics and metal. This work describes the development of such a production process called “hybrid forming”, which combines the cold forming of steel sheets with the compression molding of long fiber reinforced thermoplastics in a simultaneous process step and at the same time connects both materials by using an adhesion promoter. The required tool and sealing concepts for different geometries are developed, the joining properties are determined, and relevant process parameters are identified and optimized. With the aid of a developed design and optimization method based on the finite elements method (FEM), it will be possible to make steel components up to 20% lighter by reducing sheet thickness and simultaneously reinforcing them with a ribbed structure made of fiber-reinforced plastic without losing any of the components’ mechanical properties. The entire process, from the component and tool design to the manufacturing on series production lines, is demonstrated using a real front axle control arm.Source Type:Doctoral ThesisSeries:Siegener Schriftenreihe AutomobiltechnikVolume number:44 7 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , Abschlussbericht zum BMBF-Forschungsprojekt MultiForm - Entwicklung eines Hochleistungsverfahrens zur simultanen Umformung von faserverstärkten Kunststoffen mit Metallblechen : Projektzeitraum: 01.08.2014-31.07.2018(2019); ; Die Herstellung von Hybridbauteilen aus Metall und Kunststoff für automobile Leichtbauanwendungen erfolgt in der Regel in getrennten Fertigungsschritten und Werkzeugen. Für die Blechumformung ist das Tiefziehen ein etabliertes Fertigungsverfahren und Kunststoffbauteile können in Spritzgieß- oder Fließpress-Verfahren hergestellt werden. In einer nachfolgenden Fügeoperation können Metall und Kunststoff zu einem hybriden Bauteil zusammengeklebt werden. Im öffentlich geförderten Forschungsprojekt „MultiForm“ wird eine wirtschaftliche Verfahrenskombination („Hybridpressen“) des Tiefziehens von Metallblechen und dem Fließpressen von langfaserverstärkten Thermoplasten (LFT) entwickelt. Dabei wirkt die thermoplastische Kunststoffschmelze wie ein Wirkmedium in hydromechanischen Prozessen (z.B. Innenhochdruckumformung) und formt zusammen mit dem Werkzeugstempel hochfeste Stahlbleche. Durch Einsatz eines Haftvermittlers als Vorbeschichtung auf dem Metallblech wird gleichzeitig eine stoffschlüssige Verbindung zum Thermoplast hergestellt. Somit werden beim Hybridpressen drei Fertigungsschritte (Metall Tiefziehen, LFT-Fließpressen, Kleben) in einem Schritt vereint, sodass Hybridbauteile deutlich wirtschaftlicher gefertigt werden können. Das neuartige Verfahren „Hybridpressen“ wird im vorliegenden Projektbericht anhand zweier Bauteile aus dem Fahrwerksbereich demonstriert.Source Type:BookSeries:Siegener Schriftenreihe AutomobiltechnikVolume number:31 4 - Some of the metrics are blocked by yourconsent settings
Publication Entwicklung eines neuen Widerstandsnietschweißverfahrens zur flexiblen und wirtschaftlichen Fertigung der Karosserie in der Al-Stahl-Mischbauweise(2020-12-14)Fahrzeuge werden derzeit modular konzipiert und gemeinsam auf einer Rohbaulinie gefertigt. Die Fertigungsanlagen werden meist über Fahrzeuggenerationen wiederverwendet, um die Investitionskosten zu reduzieren. Eine Karosserie in Al-Stahl-Mischbauweise ist eine vielversprechende Lösung, um Leichtbauanforderungen zu erfüllen und zugleich die Rohbaulinien weiter zu nutzen. Allerdings erfüllen die üblichen mechanischen Fügeverfahren z.B. Halbhohl- und Vollstanznieten etc. aufgrund von Prozesseinschränkungen die Anforderungen an Flexibilität und Wirtschaftlichkeit nicht, die bei der Fertigung der modular konzipierten Karosserien sowohl in Stahlbauweise als auch in Al-Stahl- Mischbauweise bestehen. Daher ist die Entwicklung einer neuen Fügetechnik notwendig, mit der die Wiederverwendung der existierenden Punktschweißanlagen bei Herstellung der Al-Stahl- Mischstruktur parallel zur reinen Stahlkarosserie ermöglicht werden kann. In dieser Dissertation wurde daher ein neues Fügeverfahren „Widerstandsnietschweißen (WNS)“ für Al-Stahl-Mischbaustrukturen entwickelt. Karosserien in Al-Stahl-Mischbauweise und Stahlbauweise können mit dem in der Dissertation dargestellten Verfahren auf der gleichen Rohbaulinie mit herkömmlicher Punktschweißanlage ohne zusätzlichen Änderungen gefertigt werden und so Investitionskosten an neuen Rohbauanlagen vermieden werden.Source Type:DissertationSeries:Siegener Schriftenreihe Automobiltechnik1 6 - Some of the metrics are blocked by yourconsent settings
Publication Entwicklung einer Methode zur belastungsgerechten und masseoptimierten Initialauslegung von Multi-Material-Bauteilen aus isotrop-anisotropen Materialkombinationen(2024-02-26)Der Wandel in der Automobilindustrie vom Verbrennungsmotor auf Basis fossiler Brennstoffe hin zu batterieelektrisch angetriebenen Fahrzeugen impliziert einen nahezu ebenso großen Wandel im Fahrzeugbau. Die seit je ambivalenten Anforderungen an Karosserien werden durch die Integration von Traktionsbatterien erhöht - eine Herausforderung auch für den Fahrzeugleichtbau. Die vorliegende Arbeit beschreibt die Entwicklung, Implementierung und erste Validierung einer neuartigen Methode zur Initialauslegung von Multi-Material-Bauteilen aus einer isotropen Grundschicht und anisotropen FKV-Verstärkungen. Die Methodik soll dabei auf Basis einfacher und in der frühen Phase der Produktentwicklung existenter FE-Modelle und daraus abgeleiteter Belastungszustände einen Vorschlag für die Topographie (Verteilung von isotroper Metall- Grundschicht und anisotropen FKV-Verstärkungen) eines Multi-Material-Bauteils generieren. Um das zu realisieren, arbeitet die Methodik nach dem Input aller relevanter Daten mittels drei Programmblöcken. Zunächst wird der Belastungszustand pro finitem Element des Referenzbauteils analysiert, sodass Spannungshöhen und -richtungen bekannt sind. Im nächsten Schritt werden Bauteilbereiche mit homogenen Spannungsrichtungen zusammengefasst, da diese beim Einsatz von anisotropen FKV Leichtbaupotenzial aufweisen. Abschließend erfolgt eine Dickenoptimierung zwischen isotroper Grundschicht und anisotropen FKV-Verstärkungen, welche das Ziel einer minimalen Bauteilmasse hat. So kann ein erster Entwurf für belastungsgerechte und gewichtsoptimierte Multi-Material-Bauteile erstellt werden. Die neue Methodik wird abschließend auf Probenebene und anhand realer Karosseriebauteile eines Elektrofahrzeugs validiert.Source Type:DissertationSeries:Siegener Schriftenreihe Automobiltechnik1 3 - Some of the metrics are blocked by yourconsent settings
Publication Leichtbaupotenziale im Fahrwerk – Multi-Material-Design durch simultane Umformung von Metallblechen und Urformung von langfaserverstärkten Thermoplasten (LFT)(2020-04-15)Der werkstoffliche Leichtbau muss als tragende Säule innerhalb der Fahrzeugentwicklung sowohl den Sicherheitsaspekt berücksichtigen als auch zur Reduktion der Fahrzeugmasse und somit zur Verringerung des Kraftstoffverbrauchs bzw. des Schadstoffausstoßes beitragen. Neben der Entwicklung neuer, hochfester und mittels Warmumformung hergestellter Stahlgüten zur Verringerung von Blechdicken sowie Mischbauweisen mit Aluminium und Magnesium werden zunehmend auch faserverstärkte Kunststoffe im Fahrzeugbau eingesetzt. Bei Anwendung dieser sogenannten Multi-Material-Bauweise bis auf Bauteilebene resultiert gleichzeitig ein Bedarf nach wirtschaftlichen und kombinierten Herstellungsverfahren für Kunststoff-Metall- Hybridbauteile. Die vorliegende Arbeit beschreibt die Entwicklung eines solchen Fertigungsverfahrens namens „Hybridpressen“, welches die Kaltumformung von Stahlblechen mit dem Fließpressen von langfaserverstärkten Thermoplasten in einem simultanen Prozessschritt kombiniert und gleichzeitig beide Werkstoffe durch Einsatz eines Haftvermittlers stoffschlüssig miteinander verbindet.Source Type:DissertationSeries:Siegener Schriftenreihe Automobiltechnik1 10
