Prof. Dr. Paul Steinmann

Institute of Applied Mechanics

Based on the theory of nonlinear continuum mechanics we model and simulate the complex mechanical behaviour of materials as well as transient processes such as growth, diffusion, or damage, to tackle open challenges in biomedical applications.

Research projects

  • Biomechanics
  • Biopolymers
  • Hydrogels
  • Brain mechanics across scales: Linking microstructure, mechanics and pathology (BRAINIACS)
  • Novel Biopolymer Hydrogels for Understanding Complex Soft Tissue Biomechanics
  • Microscale characterization methods for the calibration of substance laws for biomaterials and plastics
  • Modelling and computation of growth in soft biological matter

Current Projects

  • Mehrskalen Modellierung und Simulation von Osteoporose (OP): Kopplung der Mechanik auf Gewebeebene

    (Third Party Funds Single)

    Term: 1. January 2022 - 31. December 2022
    Funding source: Bayerische Forschungsallianz (BayFOR)

    Knochen ist ein lebendes Material, das auf mechanische und nicht-mechanische Reize reagiert. OP ist die häufigste Altersknochenerkrankung und stellt eine Bedrohung für unsere alternde Gesellschaft dar. OP ist eine Knochenstoffwechselstörung, die zu einer erhöhten Knochenporosität führt und das Frakturrisiko erhöht. Die damit einhergehende Abnahme der Knochendichte ist charakteristisch für den Knochenverlust.
    Wir schlagen ein Multiskalenmodell zur prädiktiven numerischen Simulation der OP vor. Dies wird es Klinikern ermöglichen, patientenspezifische Behandlungs- und Medikamentenoptionen virtuell zu analysieren und so z.B. eine schädliche 0berexposition des Patienten durch Röntgenbestrahlung zu vermeiden.
    Wir beschreiben Knochenumbau simultan auf der Gewebeskala und auf der Zellskala. Knochenumbau verändert die Knochendichte mit der Möglichkeit ihrer stimulusinduzierten Zu- oder Abnahme. Die Gewebeskala ermöglicht patientenspezifische Simulationen der OP und ihres Verlaufs. Wir erfassen die Knochendichte durch ein Kontinuumsfeld und modellieren ihre Entwicklung durch einen Stimulus und einen Attraktor. Der Stimulus ist mechanischen und nicht-mechanischen Ursprungs, letzterer z.B. durch die Verfügbarkeit von Nahrung und/oder Medikamenten. Auf der Zellskala werden biochemische Signale und ihre Auswirkungen auf die Genese und Mortalität von Knochenzellen betrachtet.
    Knochenzellen nehmen ihre mechanische Umgebung wahr und reagieren darauf. Daher koppelt PP 2 (FAU+QUT) die makroskopische mechanische Reaktion direkt mit dem Gleichungssatz, der die zelluläre Knochenenlwicklung auf der Zellskala erfasst. Komplementär koppelt PP 1 (THN+QUT) die Modellierung auf der Zellskala an die Gewebeskala, indem es ein 'zelluläres Knochenbildungs-Resorptionsmodell in den Stimulus und Attraktor der makroskopischen Knochendichteentwicklung einbezieht. So wird die Dynamik der zellulären Knochenenlwicklung auf der Zellskala direkt den Knochenumbauprozess auf der Gewebeskala diktieren.

  • Micro-resolved finite element modeling and simulation of nonwovens

    (Third Party Funds Single)

    Term: 1. June 2021 - 31. May 2023
    Funding source: Deutscher Akademischer Austauschdienst (DAAD)

    The goal of this project is to develop a modelling and simulation technique enabling:
    (i) the generation of nonwoven unit cell models according to a given set of structure parameters (size, density/grammage, orientation distribution function, fiber properties, …) and relying on a sophisticated beam discretization and formulation extended to contact treatment
    (ii) the simulation of the relevant processing steps, i.e. the densification and bond point genera-tion, whereby, for simplicity, only isothermal processes are initially considered and the newly formed bond points are introduced via Dirichlet boundary conditions confining the nonwoven unit cell
    (iii) deformation simulations (uniaxial, biaxial, bending,…) under due consideration of fiber proper-ties and contact behavior, validation against experimental data

  • Methodenentwicklung zur Simulation von hyperelastischen Klebverbindungen unter Crashbelastung

    (Third Party Funds Single)

    Term: 1. April 2021 - 30. September 2023
    Funding source: Bundesministerium für Wirtschaft und Technologie (BMWi)
  • Eine nahtlose VE-basierte Mehrskalen-Kopplungsmethode für Meso-Heterogene Materialien

    (Third Party Funds Single)

    Term: 15. March 2021 - 14. March 2024
    Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)
    The overarching objective of our proposal is to develop a revolutionary seamless horizontally coupled multiscale method for meso-heterogeneous materials. For capturing the macroscopic mechanical behaviour of meso-heterogeneous materials by modelling and simulation, which is of utmost importance from an engineering perspective, computational challenges arise from the overwhelming geometric complexity and detail of the meso-structure. This urgently asks for multiscale coupling methods that enable to reduce the computational cost of simulations at the engineering scale, however without sacrificing accuracy when capturing the influence of the meso-structure on the macroscopic mechanical response. Our approach will not rely on scale-separation in order to be suited for problems involving singularities, e.g. at crack tips, and it will use a sole and uniform description of the underlying mesoscopic material behaviour in terms of its material properties and meso-structure in macro- and mesoscopically resolved sub-domains. To achieve this goal, we take inspiration from the quasi continuum (QC) method for crystalline materials that seamlessly bridges fully resolved atomistic domains with quasi continuum domains in which the majority of the atoms are enslaved to follow the motion of only a few representative atoms (Rep-Atoms). We thus propose to substitute the notion of atoms and Rep-Atoms as used in the QC method for the case of crystalline materials by the notion of nodes and Rep-Nodes for the case of meso-heterogeneous materials. Then, the underlying material meso-structure is fully represented everywhere within a macroscopic engineering structure. However, only a much smaller sub-set of the total amount of nodes and corresponding dofs is retained for the simulation of the engineering structure. We will distinguish between the underlying sub-discretization build on all nodes to capture the meso-structure and the overlaying Sup-Discretization build on only the much lesser number of Rep-Nodes used for the simulation of the macroscopic engineering structure. The assignment of sub-discretization nodes to Sup-Discretization Rep-Nodes and the definition of the corresponding Sup-Discretization follows adaptively. A versatile approach to mesh complex domains that allows for arbitrary polygons/polyhedra is the virtual element (VE) approach based on VE Ansatz functions. Noteworthy, VE Ansatz functions are not restricted to interpolate nodal dofs merely linearly along element edges/faces. This freedom in arbitrarily choosing the polynomial degree of the Ansatz functions makes VE conceptually also amenable to p-adaptivity. Of particular interest for our current proposal is moreover that the vertexes of the arbitrary polygons/polyhedra representing a VE and carrying the nodal dofs may also lay on straight lines/planar surfaces. Thus, VE elegantly and straightforwardly enables transition between sub-domains with strongly varying discretization densities.
  • Investigation of residual stress-related elementary processes for forged components in the manufacturing and operating phase

    (Third Party Funds Group – Sub project)

    Overall project: The utilization of residual stresses induced by metal forming
    Term: 1. January 2021 - 31. December 2022
    Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)
  • Symplectic Elasticity Theory and Formulation for Geometrically Nonlinear Structures

    (Third Party Funds Single)

    Term: 1. January 2021 - 31. December 2022
    Funding source: Deutscher Akademischer Austauschdienst (DAAD)

    Die Kontinuumsmechanik ist eine wichtige Grundlagenwissenschaft in den Ingenieur- und Naturwissenschaften, die den Zusammenhang zwischen Kräften und Deformationen (und Bewegungen) in Materialien und Strukturen modelliert. Ihre numerische Umsetzung z.B. in der Finiten Element Methode ist aus dem Alltag von Berechnungsabteilungen von technologieorientierten Unternehmen aufgrund ihrer hervorgehobenen Relevanz heutzutage nicht mehr wegzudenken. Das hier beantragte Vorhaben zielt, motiviert durch Konzepte der Hamiltonschen Dynamik auf die erstmalige Etablierung eines völlig neuartigen, sogenannten symplektischen Zugangs zur geometrisch nichtlinearen Kontinuumsmechanik mit zunächst speziellem Fokus auf die nichtlineare Elastizität. Die symplektische Formulierung der geometrisch nichtlinearen Kontinuumsmechanik verspricht neben ihrer Eleganz dabei insbesondere zahlreiche Vorteile im Rahmen ihrer numerischen Umsetzung. Die nichtlineare Elastizität hat vielfältige bedeutende Modellierungsanwendungen im Bereich weicher und weichster Materialien mit größter aktueller Bedeutung beispielweise für die Mechanik biologischer Gewebe, die Soft-Robotik sowie zahlreicher derzeit entwickelter high-tech Metamaterialien. In Summe wird hier sehr vielversprechendes aber auch riskantes thematisches Neuland betreten, wobei die Erfolgsaussichten des Vorhabens aufgrund der komplementären Expertise der Projektpartner als sehr hoch einzuschätzen sind.

  • Eine hybride Fuzzy-Stochastische-Finite-Element-Methode für polymorphe, mikrostrukturelle Unsicherheiten in heterogenen Materialien

    (Third Party Funds Single)

    Term: 1. December 2020 - 30. November 2023
    Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)
    Computational homogenization requires two separate finite element models: a model at the macroscale and a model of the materials’ underlying structure at the microscale. Computational homogenization involves two main ingredients: the transfer of the macroscopic loading to the microscale and averaging the corresponding response of the microstructure to obtain the effective macroscopic properties. A challenging aspect for computational homogenization is the proper modelling of material with uncertainty in the microstructure, as considered in this project. Uncertainties in the macroscopic response of heterogeneous materials result from various sources: the natural variability in the microstructure’s geometry and its constituent’s material properties and the lack of sufficient knowledge regarding the microstructure. The first type of uncertainty is denoted as aleatoric uncertainty and may be characterized by probabilistic approaches. The second type of uncertainty is denoted as epistemic uncertainty and may be described using fuzzy arithmetic. Models considering both sources of uncertainty are denoted polymorphic, requiring some combination of stochastic and fuzzy methods.In Phase I we developed methods for the accurate and efficient propagation of polymorphic uncertainty through the material’s microstructure and applied all proposed approaches to a benchmark problem. The objectives of the Phase II are further development of modelling techniques and their application to the engineering design of structures. The outcome of Phase II will be an accomplished methodology allowing the uncertainty propagation from the lowest level of a material microstructure through the macroscopic structure simulation to the engineering design and decision making. More precisely in Phase II the following challenges are considered:- We continue the development of advanced fuzzy-stochastic benchmark RVE for the microstructure of heterogeneous materials, resulting thus in a more realistic and precise description of polymorphic uncertainty in the material’s microstructure. - Modelling techniques for spectral non-deterministic finite element analysis will be enriched to non-deterministic eXtended Isogeometric Analysis.- The computational cost of full-order large scale simulations of systems in the presence of uncertainty is unacceptably high, in particular considering many-query or real-time applications. Thus, reduced order modeling is an essential tool which allows a speed up microscale simulations. - Reduced order models and metamodels provide a necessary bridge to the final stage of the project, in which a suitable metamodel will be used on the macroscale to run large size simulations of engineering structures. - Finally, the influence of uncertainty in the macrostructure on the static and the dynamic behavior of engineering structures under random loading will be analyzed.
  • A hybrid Fuzzy-Stochastic-Finite-Element-Method for polymorphic, microstructural uncertainties in heterogeneous materials

    (Third Party Funds Group – Sub project)

    Overall project: Polymorphic uncertainty modelling for the numerical design of structures
    Term: 1. December 2020 - 30. November 2023
    Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)
    Computational homogenization requires two separate finite element models: a model at the macroscale and a model of the materials’ underlying structure at the microscale. Computational homogenization involves two main ingredients: the transfer of the macroscopic loading to the microscale and averaging the corresponding response of the microstructure to obtain the effective macroscopic properties. A challenging aspect for computational homogenization is the proper modelling of material with uncertainty in the microstructure, as considered in this project. Uncertainties in the macroscopic response of heterogeneous materials result from various sources: the natural variability in the microstructure’s geometry and its constituent’s material properties and the lack of sufficient knowledge regarding the microstructure. The first type of uncertainty is denoted as aleatoric uncertainty and may be characterized by probabilistic approaches. The second type of uncertainty is denoted as epistemic uncertainty and may be described using fuzzy arithmetic. Models considering both sources of uncertainty are denoted polymorphic, requiring some combination of stochastic and fuzzy methods.In Phase I we developed methods for the accurate and efficient propagation of polymorphic uncertainty through the material’s microstructure and applied all proposed approaches to a benchmark problem. The objectives of the Phase II are further development of modelling techniques and their application to the engineering design of structures. The outcome of Phase II will be an accomplished methodology allowing the uncertainty propagation from the lowest level of a material microstructure through the macroscopic structure simulation to the engineering design and decision making. More precisely in Phase II the following challenges are considered:- We continue the development of advanced fuzzy-stochastic benchmark RVE for the microstructure of heterogeneous materials, resulting thus in a more realistic and precise description of polymorphic uncertainty in the material’s microstructure. - Modelling techniques for spectral non-deterministic finite element analysis will be enriched to non-deterministic eXtended Isogeometric Analysis.- The computational cost of full-order large scale simulations of systems in the presence of uncertainty is unacceptably high, in particular considering many-query or real-time applications. Thus, reduced order modeling is an essential tool which allows a speed up microscale simulations. - Reduced order models and metamodels provide a necessary bridge to the final stage of the project, in which a suitable metamodel will be used on the macroscale to run large size simulations of engineering structures. - Finally, the influence of uncertainty in the macrostructure on the static and the dynamic behavior of engineering structures under random loading will be analyzed.
  • Experimentelle und numerische Untersuchung des Einflusses variabler Betriebstemparaturen auf das Trag- und Versagensverhalten struktureller Klebverbindungen unter Crashbelastung

    (Third Party Funds Single)

    Term: 1. June 2020 - 30. November 2022
    Funding source: Bundesministerium für Wirtschaft und Technologie (BMWi)
  • Multiskalen Modellierung und Simulation ferroelektrischer Materialien

    (Third Party Funds Single)

    Term: 1. December 2019 - 30. November 2022
    Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)
  • Mesoscopic modelling and simulation of properties of additively manufactured metallic parts (C5)

    (Third Party Funds Group – Sub project)

    Overall project: CRC 814 - Additive Manufacturing
    Term: 1. July 2019 - 30. June 2023
    Funding source: DFG - Sonderforschungsbereiche
    URL: https://www.crc814.research.fau.eu/projekte/c-bauteile/teilprojekt-c5/

    Based on the gained knowledge of projects B4 and C5,the aim of this project is to account for the influence of part borders on theresulting material/part-mesostructure for powder- and beam-based additivemanufacturing technologies of metals and to model the resulting meso- andmacroscopic mechanical properties. The mechanical behavior of thesemesostructures and the influence of the inevitable process-based geometricaluncertainties is modelled, verified, quantified and validated especially forcellular grid-based structures.

  • Teilprojekt P5 - Compressive Failure in Porous Materials

    (Third Party Funds Group – Sub project)

    Overall project: Skalenübergreifende Bruchvorgänge: Integration von Mechanik, Materialwissenschaften, Mathematik, Chemie und Physik (FRASCAL)
    Term: 2. January 2019 - 30. June 2023
    Funding source: DFG / Graduiertenkolleg (GRK)
    URL: https://www.frascal.research.fau.eu/home/research/p-5-compressive-failure-in-porous-materials/

    Materials such as solid foams, highly-porous cohesive granulates, for aerogels possess a mode of failure not available to other solids. cracks may form and propagate even under compressive loads (‘anticracks’, ‘compaction bands’). This can lead to counter-intuitive modes of failure – for instance, brittle solid foams under compressive loading may deform in a quasi-plastic manner by gradual accumulation of damage (uncorrelated cell wall failure), but fail catastrophically under the same loading conditions once stress concentrations trigger anticrack propagation which destroys cohesion along a continuous fracture plane. Even more complex failure patterns may be observed in cohesive granulates if cohesion is restored over time by thermodynamically driven processes (sintering, adhesive aging of newly formed contacts), leading to repeated formation and propagation of zones of localized damage and complex spatio-temporal patterns as observed in sandstone, cereal packs, or snow.

    We study failure processes associated with volumetric compaction in porous materials and develop micromechanical models of deformation and failure in the discrete, porous microstructures. We then make a scale transition to a continuum model which we parameterise using the discrete simulation results.

  • Teilprojekt P10 - Configurational Fracture/Surface Mechanics

    (Third Party Funds Group – Sub project)

    Overall project: Fracture across Scales: Integrating Mechanics, Materials Science, Mathematics, Chemistry, and Physics (FRASCAL)
    Term: 2. January 2019 - 30. June 2023
    Funding source: DFG / Graduiertenkolleg (GRK)
    URL: https://www.frascal.research.fau.eu/home/research/p-10-configurational-fracture-surface-mechanics/

    In a continuum the tendency of pre-existing cracks to propagate through the ambient material is assessed based on the established concept of configurational forces. In practise crack propagation is however prominently affected by the presence and properties of either surfaces and/or interfaces in the material. Here materials exposed to various surface treatments are mentioned, whereby effects of surface tension and crack extension can compete. Likewise, surface tension in inclusion-matrix interfaces can often not be neglected. In a continuum setting the energetics of surfaces/interfaces is captured by separate thermodynamic potentials. Surface potentials in general result in noticeable additions to configurational mechanics. This is particularly true in the realm of fracture mechanics, however its comprehensive theoretical/computational analysis is still lacking.

    The project aims in a systematic account of the pertinent surface/interface thermodynamics within the framework of geometrically nonlinear configurational fracture mechanics. The focus is especially on a finite element treatment, i.e. the Material Force Method [6]. The computational consideration of thermodynamic potentials, such as the free energy, that are distributed within surfaces/interfaces is at the same time scientifically challenging and technologically relevant when cracks and their kinetics are studied.

  • Fracture across Scales: Integrating Mechanics, Materials Science, Mathematics, Chemistry, and Physics (FRASCAL)

    (Third Party Funds Group – Overall project)

    Term: 1. January 2019 - 30. June 2023
    Funding source: DFG / Graduiertenkolleg (GRK)
    URL: https://www.frascal.research.fau.eu/

    The RTG aims to improve understanding of fracture in brittle heterogeneous materials by developing simulation methods able to capture the multiscale nature of failure. With i) its rooting in different scientific disciplines, ii) its focus on the influence of heterogeneities on fracture at different length and time scales as well as iii) its integration of highly specialised approaches into a “holistic” concept, the RTG addresses a truly challenging cross-sectional topic in mechanics of materials. Although various simulation approaches describing fracture exist for particular types of materials and specific time and length scales, an integrated and overarching approach that is able to capture fracture processes in different – and in particular heterogeneous – materials at various length and time resolutions is still lacking. Thus, we propose an RTG consisting of interdisciplinary experts from mechanics, materials science, mathematics, chemistry, and physics that will develop the necessary methodology to investigate the mechanisms underlying brittle fracture and how they are influenced by heterogeneities in various materials. The insights obtained together with the methodological framework will allow tailoring and optimising materials against fracture. The RTG will cover a representative spectrum of brittle materials and their composites, together with granular and porous materials. We will study these at length and time scales relevant to science and engineering, ranging from sub-atomic via atomic and molecular over mesoscale to macroscopic dimensions. Our modelling approaches and simulation tools are based on concepts from quantum mechanics, molecular mechanics, mesoscopic approaches, and continuum mechanics. These will be integrated into an overall framework which will represent an important step towards a virtual laboratory eventually complementing and minimising extensive and expensive experimental testing of materials and components. Within the RTG, young researchers under the supervision of experienced PAs will perform cutting-edge research on challenging scientific aspects of fracture. The RTG will foster synergies in research and advanced education and is intended to become a key element in FAU‘s interdisciplinary research areas “New Materials and Processes” and “Modelling–Simulation–Optimisation”.

  • Fractures across Scales: Integrating Mechanics, Materials Science, Mathematics, Chemistry, and Physics/ Skalenübergreifende Bruchvorgänge: Integration von Mechanik, Materialwissenschaften, Mathematik, Chemie und Physik

    (Third Party Funds Single)

    Term: 1. January 2019 - 30. June 2023
    Funding source: Deutsche Forschungsgemeinschaft (DFG)
    URL: https://www.frascal.research.fau.eu/
  • Identification of interphase properties in nanocomposites

    (Third Party Funds Single)

    Term: 15. October 2018 - 31. January 2024
    Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)

    In engineering applications, plastics play an important role and offer new possibilities to achieve and to adjust a specific material behaviour. They consist of long-chained polymers and possess, together with additives, an enormous potential for tailored properties.

    Recently, techniques have been established to produce and to disperse filler particles with typical dimensions in the range of nanometers. Even for low volume contents of filler particles, these socalled nanofillers may have significant impact on the properties of plastics. This can be most likely traced back to their very large volume-to-surface ratio. In this context, the polymer-particle interphase is of vital importance: as revealed by experiments, certain nanofillers may e.g. increase the fatigue lifetime of plastics by a factor of 15.

    The effective design of such nanocomposites quite frequently requires elaborated mechanical testing, which might - if available - be substituted or supplemented by simulations. For this purpose, however, continuum mechanics together with the Finite Element Method (FE) as the usual tool for engineering applications is not well-suited since it is not able to capture processes at the molecular level. Therefore, particle-based techniques such as molecular dynamics (MD) have to be employed. However, these typically allow only for extremely small system sizes and simulation times. Thus, a multiscale technique that couples both approaches is required to enable the simulation of so-called representative volume elements (RVE) under consideration of atomistic effects.

    The goal of this 4-year project is the development of a methodology which yields a continuum-based description of the material behaviour of the polymer-particle interphase of nanocomposites, whereby the required constitutive laws are derived from particle-based simulations. Due to their very small dimensions of some nanometers, the interphases cannot be accessed directly by experiments and particle-based simulations must substitute mechanical testing. The recently developed Capriccio method, designed as a simulation tool to couple MD and FE descriptions for amorphous systems, will be employed and refined accordingly in the course of the project.

    In the first step, the mechanical properties of the polymer-particle interphase shall be determined by means of inverse parameter identification for small systems with one and two nanoparticles. In the second step, these properties shall be transferred to large RVEs. With this methodology at hand, various properties as e.g. the particles’ size and shape as well as grafting densities shall be mapped from pure particle-based considerations to continuum-based descriptions. Further consideration will then offer prospects to transfer the material description to applications relevant in engineering and eventually suited for the simulation of parts.

  • Investigation of residual stress related elementary processes in cold forged components in the manufacturing and operating phase

    (Third Party Funds Single)

    Term: 1. February 2018 - 31. December 2022
    Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)

    Due to the potential of forming induced residual stresses to influence component properties, a deeper understanding of the mechanisms of residual stress generation and stability is required. Therefore, the approach to the research project is structured into the phases of component manufacturing (generation of residual stresses), component operation (residual stress stability) and process design (exploitation of residual stresses). As reference process the forward rod extrusion is used, which is established as standard process in industrial use. Due to the trend towards component materials with higher strength and corrosion resistance, two stainless steels are used in the project. The investigations include parallel experimental and numerical analyses of the process and its synthesis.

    During the first phase, the necessary experimental equipment for component manufacture and testing was set up, material and friction parameters were identified, components were formed under consideration of different parameter variants and their residual stresses were determined by X-ray diffraction. In a complementary approach, macroscopic finite element models with subroutines for an extended post-processing of residual stresses were developed on the simulation side and applied in the context of numerical parameter variations. Furthermore, differential geometric and continuum mechanical relationships of residual stresses were investigated and the material modelling was extended to crystal plasticity. The predictivity of the numerical results was quantified on the basis of experimental results.

    The second phase concentrates on the residual stress stability in component use and the process robustness during component manufacture. The knowledge gained will be used at the end of the second and in the third phase to specifically influence the operating behaviour and to control the cyclic strength.

    The objective in the second phase is the experimental and numerical determination of the mechanical and thermal residual stress stability. As a requirement for the targeted influencing, relevant parameters will be identified. These cause-and-effect relationships are to be plausibilised by means of fundamental physical effects, whereby a recourse is made to effects described in the literature and numerical methods for the derivation of basic model ideas. Based on the experience gained so far, fluctuations of input variables and previously known disturbance variables are to be taken into account in all investigations. A further prerequisite for a systematic investigation of the fundamental mechanisms relevant to residual stresses is an increase in the numerical modeling and prediction accuracy of the deformation-induced residual stresses. In analogy to the generation phase, a constant comparison of simulation and experiment is therefore also carried out in the operating phase in the sense of an assessment of the prognosis quality of the numerical approaches and the plausibility of the experimental laboratory results.

    The Project is part of the DFG priority programm SPP2013 "Targeted Use of Forming Induced Internal Stresses in Metal Components". Within the priority program, the subproject takes part in the expert groups Production technology (thick-walled) and Mechanics and simulation.

  • Investigation of residual stress related elementary processes in cold forged components in the manufacturing and operating phase

    (Third Party Funds Single)

    Term: 1. January 2018 - 31. March 2024
    Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)

    The operational behavior of steel components is significantly influenced by their residual stress state. On the basis of forward rod extrusion of stainless steel, methods for the controlled generation of residual stresses are being investigated, their stability under typical operating conditions is being analyzed and their effects on the operating behavior are being identified in this research project. In the first phase, basic mechanisms of the generation of residual stresses were identified. In the current second phase, parameters for a robust adjustment of the residual stress state during forming were developed, whereby lubrication in particular was identified as relevant. Furthermore, the influence of thermal and mechanical loads on the stability of the residual stresses in the components is being investigated.

  • Fracture Across Scales and Materials, Processes and Disciplines

    (Third Party Funds Group – Sub project)

    Overall project: Fracture Across Scales and Materials, Processes and Disciplines
    Term: 1. September 2017 - 31. July 2022
    Funding source: EU - 8. Rahmenprogramm - Horizon 2020
  • Mikroskalige Charakterisierungsmethoden zur Kalibrierung von Stoffgesetzen für Biomaterialien und Kunststoffe

    (Own Funds)

    Term: 1. August 2014 - 31. December 2025

    Aussagefähige Bauteilsimulationen erfordern eine quantitativ exakte Kenntnis der Materialeigenschaften. Dabei sind klassische Charakterisierungsmethoden
    teilweise aufwendig, in der Variation und Kontrolle der Umgebungsbedingungen anspruchsvoll oder in der räumlichen Auflösung begrenzt. Das Projekt beschäftigt sich
    deshalb mit der Ertüchtigung hochauflösender Meßmethoden wie Nanoindentation oder Rastkraftmikroskopie und der komplementierenden Entwicklung numerischer
    Verfahren zur Kalibrierung (Parameteridentifikation) inelastischer Stoffgesetze aus den Meßdaten. Inhärent anspruchsvoll sind dabei die geeignete Gestaltung der
    Probekörper und ihrer Fixierung, die den gesuchten Eigenschaften angepaßte Versuchsführung und die hinreichend genaue Reproduktion derselben im Rahmen der zur
    Parameteridentifikation erforderlichen Finite-Elemente-Simulationen.
     

  • Kontinuumsmechanische Modellierung und Simulation der Aushärtung und Inelastizität von Polymeren sowie Interphasen in Klebverbunden

    (Own Funds)

    Term: 1. August 2008 - 31. December 2025

    Die mechanischen Eigenschaften von Polymerwerkstoffen hängen nicht nur von der chemischen Komposition und den Umgebungsbedingungen (Temperatur, Feuchte,...) ab,
    sondern sie variieren teilweise erheblich mit dem verwendeten Aushärteregime und der Temperaturhistorie. Sie sind darüber hinaus vor allem in Verbundsituationen
    u.U. sogar ortsabhängig von den Eigenschaften der Kontaktpartner beeinflußt, bilden also Eigenschaftgradienten (sog. Interphasen) aus.
    Um diese Effekte bei der Simulation von Bauteilen korrekt abbilden zu können werden im Rahmen des Projektes Modelle entwickelt und erweitert,
    die zeit-, orts- und umgebungsabhängige Materialeigenschaften wie Steifigkeitsevolutionen und -gradienten, Aushärteschrumpf und verschiedene Arten von
    Inelastizität (Viskoelastizität, Elastoplastizität, Viskoplastizität, Schädigung) berücksichtigen können.

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