Improving Accuracy and Performance of Meshfree Methods

• Process Simulation for Selective Laser Melting

  A phase change model for solution with the meshfree Galerkin OTM method is developed.

  Leaders: Christian Weißenfels, Peter Wriggers

  Team: M.Sc. Henning Wessels

  Year: 2016
• ISPH-based Simulation of the Selective Laser Melting Process

  Development of a thermo-mechanical model for the simulation of the SLM process.

  Leaders: Christian Weißenfels, Peter Wriggers

  Team: M.Sc. Jan-Philipp Fürstenau

  Year: 2017
• Using Machine Learning to Improve the Modelling of Machining and Cutting Processes

  Metal cutting is a fundamental process in industrial production. The fast and accurate on-line prediction of metal cutting processes is crucial for the Intelligent Manufacturing (IM). With the advent of high-speed computing, robust numerical algorithms and machine learning technology, computational modelling serves as a tool for not only accurate but also fast predicting the complex machining processes and understanding the complex physics. In this work, the machine learning based numerical model is developed for simulation of metal cutting processes.

  Leaders: C. Weißenfels, P. Wriggers

  Team: M.Sc. Dengpeng Huang

  Year: 2018

  Sponsors: China Scholarship Council (CSC)
• Peridynamic Galerkin Methods

  Simulation-driven product development is nowadays an essential part in the industrial digitalization. Notably, there is an increasing interest in realistic high-fidelity simulation methods in the fast-growing field of additive and ablative manufacturing processes. Thanks to their flexibility, meshfree solution methods are particularly suitable for simulating the stated processes, often accompanied by large deformations, variable discontinuities, or phase changes. Furthermore, in the industrial domain, the meshing of complex geometries represents a significant workload, which is usually minor for meshfree methods. Over the years, several meshfree schemes have been developed. Nevertheless, along with their flexibility in discretization, meshfree methods often endure a decrease in accuracy, efficiency and stability or suffer from a significantly increased computation time. Peridynamics is an alternative theory to local continuum mechanics for describing partial differential equations in a non-local integro-differential form. The combination of the so-called peridynamic correspondence formulation with a particle discretization yields a flexible meshfree simulation method, though does not lead to reliable results without further treatment. In order to develop a reliable, robust and still flexible meshfree simulation method, the classical correspondence formulation is generalized into the Peridynamic Galerkin (PG) methods in this project. On this basis, conditions on the meshfree shape functions of virtual and actual displacement are presented, which allow an accurate imposition of force and displacement boundary conditions and lead to stability and optimal convergence rates. Based on Taylor expansions moving with the evaluation point, special shape functions are introduced that satisfy all the previously mentioned requirements employing correction schemes. In addition to displacement-based formulations, a variety of stabilized, mixed and enriched variants are developed, which are tailored in their application to the nearly incompressible and elasto-plastic finite deformation of solids, highlighting the broad design scope within the PG methods. Compared to related Finite Element formulations, the PG methods exhibit similar convergence properties. Furthermore, an increased computation time due to non-locality is counterbalanced by a considerably improved robustness against poorly meshed discretizations.

  Leaders: Christian Weißenfels, Peter Wriggers

  Team: M.Sc. Tobias Bode

  Year: 2019
• Numerical simulation of pile installation in a hypoplastic framework using an SPH based Method

  In this project, a 3D computational tool using smoothed particle hydrodynamics (SPH) is developed which based on a hypoplastic constitutive approach for the mechanical behavior of the soil. The numerical code is firstly validated against a benchmark problem. Then several test cases are simulated including monotonic and vibratory penetration of piles into the soil. A good agreement with the experimental observation is found. Additionally, the impact of pile running in the presence of sheetpiles (retainers) are investigated to see how pile running can alter the applied forces on the sheet piles. The simulation of such complex geotechnical problems which involve large deformation, material nonlinearity and moving boundary conditions demonstrates the applicability and versatility of the proposed numerical tool in this field.

  Leaders: Peter Wriggers

  Team: Meisam Soleimani, Christian Weißenfels

  Year: 2020

In Silicio Analyses

• Interfacial effects and ingrowing behaviour of magnesium-based foams as bioresorbable bone substitute material

  Leaders: P. Wriggers

  Team: A. Krüger

  Year: 2016

  Sponsors: DFG
• Smart hydrogels for drug-delivery and bioprinting applications

  Leaders: Peter Wriggers

  Team: Aidin Hajikhani

  Year: 2017
• In-stent restenosis

  Leaders: Michele Marino, Peter Wriggers

  Team: Meike Gierig

  Year: 2018

Virtual Elements For Engineering Appications

• 2D VEM for crack-propagation

  Leaders: F. Aldakheel, B. Hudobivnik, P. Wriggers

  Team: A. Hussein

  Year: 2018

  Sponsors: IRTG 1627
• Virtual element method (VEM) for phase-field modeling of brittle and ductile fracture

  Leaders: F. Aldakheel, B. Hudobivnik, P. Wriggers

  Year: 2018

  Sponsors: DFG SPP 1748
• Virtual Element Method for Dynamic Applications

  The Virtual Element Method is a recent developed discretization method, which can be seen as an extension of the classical Galerkin finite element method. It has been applied to various engineering fields, such as elasto-plasticity, multiphysics, damage and fracture mechanics. This project focuses on the extension of VEM towards dynamic applications. In the first part the appropriate computation of the Massmatrix regarding the vitual element ansatzspace will be done. In future works, VEM will be applied to engineering problems, considering the dynamic behavior.

  Leaders: F. Aldakheel, B. Hudobivnik, P. Wriggers

  Team: M. Cihan

  Year: 2019
• Virtual Element Method for 3D Contact

  Contact plays a very important role in engineering problems, where two or more bodies interact with each other through their surfaces. Many techniques were developed in the past, to formulate the contact constraint at the contact interface between two bodies. Nevertheless, VEM provides efficient and robust properties to enforce the contact constraint through the contact interface. Investigations in 2D have been done so far. This work aims an extensions of VEM to 3D contact problems.

  Leaders: F. Aldakheel, B. Hudobivnik, P. Wriggers

  Team: M. Cihan

  Year: 2020

Phase Field Modeling of Fracture in Multi-Field Environments

• Water-induced damage mechanisms of cyclic loaded high-performance concretes

  Leaders: P. Wriggers

  Team: F. Aldakheel

  Year: 2017

  Sponsors: DFG SPP 2020, erste Förderperiode

  Lifespan: 3 Jahre
• Virtual element method (VEM) for phase-field modeling of brittle and ductile fracture

  Leaders: F. Aldakheel, B. Hudobivnik, P. Wriggers

  Year: 2018

  Sponsors: DFG SPP 1748

Multiscale and Multifield problems

• Multiscale Method for Hydro-Chemo-Thermo-Mechanics Coupling due to Alkali Silica Reaction in Concrete

  Alkali Silica Reaction(ASR) is one of most determinant reasons leading to the deterioration of concrete structures, which can be ascribed to the expansion of gel produced by ASR in the microstructural level of concrete. The challenge in the modeling of ASR is due to the necessity to take into account the presence of heterogeneities and physical processes distributed over multiple length scales. With increasing computation power and the tomography scan technology, it can be implemented by numerical simulation . In this contribution, 3D multiscale hydro-chemo-thermal-mechanical coupling based on a staggered method is demonstrated, which explicitly describes the damage evolution originating from the chemical reaction in the microscale and the dependence on environmental factors.

  Leaders: P. Wriggers

  Team: T. Wu

  Year: 2009
• MULTIPHYSICS COMPUTATIONAL HOMOGENIZATION METHODOLOGIES

  Computational homogenization techniques that are amenable to a multiscale implementation are being developed for multiphysics problems at the finite deformation regime. Applications include the estimation of the contact conductance for rough interfaces and the modeling of the coupled thermomechanical response of heterogeneous materials.

  Leaders: P. Wriggers, I. Temizer

  Year: 2009
• Direct Numerical Simulation of Multiphase Flows

  Multiphase flows consisting of a continuous fluid phase and a dispersed phase of macroscopic particles are present in many engineering applications. In general, a main task in the study of the particle-laden fluid flow of an application is to make predictions about the system's nature for various boundary conditions, since, depending on the volume fraction and mass concentration of the dispersed phase a fluid-particle system shows quite different flow properties. Unfortunately, often it is impossible to investigate such a system experimentally in detail or even at all. An option to capture and to predict its properties is performing a direct numerical simulation of the particulate fluid. For this purpose, an efficient approach is developed in this project by coupling the discrete element method and finite element method.

  Leaders: P. Wriggers

  Team: B. Avci

  Year: 2009
• Numerical modeling of electrical contacts

  The focus of this work is the investigation of the behavior in electrical contacts, where electrical, thermal and mechanical fields are coupled. Specifically, theoretical constitutive models for the electrical conductance and electrical wear phenomena are developed and implemented in a three dimensional finite element setting. Also a new relation for wear is proposed, where the amount of wear is coupled to the dissipation arising at the contact interface. </a></p>

  Leaders: P. Wriggers

  Team: C. Weißenfels

  Year: 2009
• RAMWASS - Integrated Decision Support System for Risk Assessment and Management

  The objective of the EU-project RAMWASS is to develop and validate a new decision support system (DSS) for the risk assessment and management for the prevention and/or reduction of the negative impacts caused by human activities on the water/sediment/soil system at river basin scale in fluvial ecosystems.

  Leaders: P. Wriggers

  Team: B. Avci

  Year: 2009
• Homogenization procedures for coupled thermo-chemo-mechanical problems

  In order to understand processes of continuum damage mechanics it is necessary to investigate thermo-chemo-mechanical coupled processes at micro scale. However for engineering purposes it is still necessary to be able to model these processes at macro scale, especially when large structures have to be designed. Thus a homogenization procedure or a FE^2 framework is necessary to transform the relation, describing the coupled thermo-chemo-mechanical response at micro scale to the macro scale. The related equations and procedures have to be developed and implemented in a finite element software system.

  Leaders: P. Wriggers, E. Baranger

  Team: Jin Man Mok

  Year: 2013
• Multi-Fluid Simulations for High Density Ratios

  Although the contact between fluids or gases of different densities is a common event in nature, like the interaction of water and air, the simulation of multiple fluids often comes along with numerous problems. With the Lagrangian description of continuous fluids in terms of the Smoothed Particle Hydrodynamics (SPH) method multi-fluid interactions within the particle scale can simulated. Nevertheless with the standard SPH algorithms multi-fluid problems can not be solved because of the density jumps at the interfaces. Within the project the state of the art of current multi-fluid approaches are compared and evaluated to develop appropriate methods for the simulation of multi-fluid systems with high density ratios.

  Leaders: P. Wriggers, B. Avci

  Team: J.-P. Fürstenau

  Year: 2014
• Towards multiscale modeling of Abrasive wear

  The work is motivated towards understanding wear as a multiscale-multiphysics approach. A 3D framework is developed to simulate cracks propagation in a microstructure due to contact loading to eventually predict wear trends in filled elastomeric compounds.

  Leaders: P. Wriggers

  Team: A. B. Harish

  Year: 2015
• Entropic approach to modeling Mullins effect in non-crystallizing filled elastomers

  The work was done in collaboration with Mrs. Aarohi B. Shah and Dr. Julian J Rimoli of School of Aerospace Engineering, Georgia Tech, USA. In this work, we investigate non-crystallizing nanoparticle-reinforced polymers. The effects of the interface rubber between elastomeric matrix and filler particles and its alteration are investigated as a primary cause of Mullins and Payne effect.

  Leaders: P. Wriggers, J. J. Rimoli

  Team: A. B. Harish, A. B. Shah

  Year: 2016

Life time prediction and failure of modern complex materials and structures

• Fatigue lifetime prediction using Wavelet transformation induced multi-time scaling (WATMUS)

  A fast and accurate numerical method for fatigue lifetime prediction using eXtended Finite Element Method(XFEM) and WATMUS

  Leaders: S. Löhnert, P. Wriggers

  Team: Tengfei Lyu

  Year: 2017
• Creep deformation of nickel based superalloys

  Modeling of nickel based superalloys on two scales using crystal plasticity and XFEM methods.

  Leaders: P. Wriggers

  Team: Lukas Munk

  Year: 2018

Material modeling

• DEVELOPMENT OF A MATERIAL MODEL FOR METAL SHEETS AT FINITE DEFORMATION

  [Translate to Englisch:] Technical procedures claim an improved material model for the simulation of metal forming processes. An effective, anisotropic elastoplastic material model for the macroscopic material behaviour for sheet metals is developed for further usage in commercial finite element programs.

  Leaders: P. Wriggers, S. Löhnert

  Team: E. Lehmann, S. Zeller

  Year: 2009
• Multiscale modeling and extended finite element analysis of fracture processes in ceramics

  The extended finite element method (XFEM) enables the modelling and calculation of cracks independent of mesh topologies. Due to this advantage it has become the most widely used method for computations of fracture processes. In the vicinity of a macrocrack front the microstructure of the material can have a significant influence and needs to be considered in detail. Especially microcracks can affect crack propagation drastically. This leads to the necessity of multiscale methods like the multiscale projection method to capture microstructural details where necessary. Even though the XFEM is known to be a comparably accurate method to calculate cracks, discretisation errors occur. Therefore, the discretisation error on the finescale is estimated via a stress smoothing technique. The realtive error of stresses enables adaptive mesh refinement on the microscale leading to more accurate results also on the macroscale. The computational model is validated by comparison of the results to experimental data.

  Leaders: P. Wriggers, S. Löhnert

  Team: C. Prange

  Year: 2009
• FAILURE ANALYSIS - ERROR ESTIMATION FOR MULTISCALE METHODS

  This project is concerned with the development of tools for error-estimation based adaptive multiscale failure analysis. In order to enable a more accurate mechanical analysis of composite aircraft substructures, existing discretisation error estimators will be improved to be used as indicators for mesh refinement. Additionally, physical error estimators will be developed to identify regions where higher-order material modelling is required.

  Leaders: P. Wriggers

  Team: N. Hajibeik

  Year: 2009
• ADAPTIVE MULTISCALE MODELING AND ANALYSIS OF HETEROGENEOUS MATERIALS

  Accurate computational analyses of a composite structure requires multiple levels of resolution: (i) a region where effective elastic properties are employed, (ii) a region where embedded micro-macro problems are solved, and (iii) a region where explicit microstructural evaluation is required. Development of such computational schemes for the adaptive multiscale analysis of heterogeneous materials is the main purpose of this project.

  Leaders: P. Wriggers, I. Temizer

  Year: 2009
• Crack propagation and crack coalescence in a multiscale framework

  In this project a numerical framework for propagating and intersecting cracks on micro and macro scales is set up. Modeling cracks using the eXtended Finite Element Method (XFEM) provides an accurate and efficient numerical framework to model propagating and intersecting cracks. Since cracks of different length scales are assumed, a multiscale method is applied in order to be numerical efficient.

  Leaders: S. Löhnert, P. Wriggers

  Team: M. Holl

  Year: 2010
• Multiscale Methods for Fracturing Solids

  In this project multiscale methods and homogenization techniques for the numerical simulation of three dimensional fracture processes are developed. These methods are important in aerospace and automotive industries and many other fields of mechanical and civil engineering as well as in bio-mechanics and material science. They will improve the prediction of the failure of structures.

  Leaders: P. Wriggers, S. Löhnert

  Team: D. Müller-Hoeppe

  Year: 2011
• Computational multiscale modelling of localized ductile failure

  Many phenomenological material models capture ductile damage. However, to flexibly incorporate the underlying the governing microstructural properties and damage mechanisms, a multiscale framework is needed. The few recent numerical multiscale works on localized failure are limited to brittle microdamage. Therefore, the goal of this project is to provide a computational multiscale framework for the modelling of localized failure stemming from a microstructure undergoing ductile damage.

  Leaders: P. Wriggers

  Team: H. Clasen

  Year: 2012

  Sponsors: DFG im Normalverfahren
• Computational homogenisation of elasto plastic material

  Particle-matrix materials are commonly used in different fields(aerospace components, bicycle frames and racing car bodies) for its mechanical and economical advantages,such as high strength, low weight and less expense.However,Because of the microstructural complexities,it is very time and labor consuming to determin the mechanical properties of composite materials. Hence,in order to reduce laboratory expense, numerical simulations via Homogenized techniques are performed on RVE to predict mechanical behavior of composite material.

  Leaders: P.Wriggers

  Team: Chao Zhang

  Year: 2012
• Constitutive modeling of large deformation behavior of filled elastomers

  In this work, a finite thickness cohesive zone model is used to study the large deformation & fracture behavior of filled elastomeric materials at the mesoscale. The study includes and has implications on filler cluster breakage, Mullins softening etc.

  Leaders: P.. Wriggers

  Team: A. B. Harish

  Year: 2015
• Process Simulation for Selective Laser Melting

  A phase change model for solution with the meshfree Galerkin OTM method is developed.

  Leaders: Christian Weißenfels, Peter Wriggers

  Team: M.Sc. Henning Wessels

  Year: 2016
• Nanoindentation for material property characterization

  In this work, techniques are developed for nanoindentation of soft polymers and brittle powdery materials and measurement of properties like modulus, hardness and fracture toughness.

  Leaders: P. Wriggers, S. Löhnert

  Team: A. B. Harish, V. Kruppernikova

  Year: 2016
• Hypoplastic material models for soil-structure interaction problems

  In this work, a hypoplastic material model is implemented using AceGen with an eventual goal to model soil-structure interaction.

  Leaders: P. Wriggers, C. Weissenfels

  Team: A. B. Harish

  Year: 2016
• Entropic approach to modeling Mullins effect in non-crystallizing filled elastomers

  The work was done in collaboration with Mrs. Aarohi B. Shah and Dr. Julian J Rimoli of School of Aerospace Engineering, Georgia Tech, USA. In this work, we investigate non-crystallizing nanoparticle-reinforced polymers. The effects of the interface rubber between elastomeric matrix and filler particles and its alteration are investigated as a primary cause of Mullins and Payne effect.

  Leaders: P. Wriggers, J. J. Rimoli

  Team: A. B. Harish, A. B. Shah

  Year: 2016
• In silico morphogenesis of collagen tissues for targeted drugs and bio-printing

  This project targets to understand the mechanisms behind the morphogenesis and the development of living tissues. To this aim, mechanical and biological actions that contribute to confer tissue desired topology and functionality will be modelled and analysed in silico. A computational framework for the modeling of tissue morphogenesis in natural and bio-printed systems will be developed. In particular, the project will address: the multiscale hierarchical and organized arrangement of tissue constituents; the chemo-mechanical interaction among tissue constituents and among cells; the chemo-mechano-biological mechanisms driving growth and remodeling; the extrusion and the curing of multicellular aggregates blended with bio-inks. Obtained results will target to elucidate mechanisms behind tissue functional/dysfunctional structure; conceive targeted drug systems for stimulating optimal molecular pathways promoting tissue healing; develop novel or optimize existing 3D bio-printing technologies.

  Leaders: M. Marino

  Year: 2017

  Sponsors: Masterplan SmartBiotecs, MWK (Lower Saxony, Germany)

Biomedical technology

• Numerical simulation and experimental validation of biofilm formation

  In this Reserch , a state-of-the-art 3D computational model has been developed to investigate biofilms in a multi-physics framework using smoothed particle hydrodynamics (SPH) based on a continuum approach. Biofilms are in fact aggregation of microorganisms such as bacteria. Biofilm formation is a complex process in the sense that several physical phenomena are coupled and consequently different time-scales are involved. On one hand, biofilm growth is driven by biological reaction and nutrient diffusion and on the other hand, it is influenced by the fluid flow causing biofilm deformation and interface erosion in the context of fluid and deformable solid interaction (FSI). The geometrical and numerical complexity arising from these phenomena poses serious complications and challenges in grid-based techniques such as finite element (FE). Such issues are generally referred to as mesh distortion. Here the solution is based on SPH as one of the powerful meshless methods. SPH based computational modeling is quite new in the biological community and the method is uniquely robust in capturing the interface-related processes of biofilm formation especially erosion. The fact is that SPH is a versatile tool owing to its adaptive Lagrangian nature in the problems whose geometry is temporarily varying (dynamic). Moreover, its mesh-less feature is considered to be favorable in interpreting the method as a particle based one. Hence, it is quite straight forward to incorporate complex interactions and ad-hoc rules at the particle level into the method. This is the case for the problems with coupled governing equations with different time and length scale. In this thesis all different physics which account for biofilm formation have been implemented in the framework of SPH and one can say that this tool is purely SPH based. Besides the numerical simulation, experiments were conducted by our partners in the medical school of Hannover. The obtained numerical results show a good agreement with experimental and published data which demonstrates that the model is capable of predicting overall spatial and temporal evolution of the biofilms. The developed tool can be employed in either controlling the detrimental biofilms or harnessing the beneficial ones.

  Leaders: Peter Wriggers

  Team: Meisam Soleimani, Peter Wriggers, Meike Stiesch

  Year: 2013
• Gekoppelte Simulation von Aerosolströmungen in asthmatischen Bronchien

  Das Ziel dieses Projektvorhabens ist es, auf Basis eines gekoppelten 3D Mehrfeldmodells die partikelbeladene Luftströmung in gesunden sowie in asthmatisch verengten Bronchien anhand von numerischen Simulationen zu studieren.

  Leaders: P. Wriggers, B. Avci

  Team: J. Stasch, J.-P. Fürstenau

  Year: 2014

  Sponsors: Leibniz Universität Hannover, Wege in die Forschung
• Advanced multiscale computational mechanics for physiopathological behavior analysis of tissues and organs

  The physiological functionalities of large biological structures are highly affected by the mechanics of living tissues which is, in turn, related to microstructural arrangement of histological constituents and biochemical environment at nanoscale. Present research activity aims to develop a novel tissue multiscale description, including also inelastic mechanisms, coupled with an advanced computational formulation under finite strain and large-displacement assumptions. As a result, an innovative in-silico tool for simulation of organs and large biological structures will be developed, allowing to predict pathology-related damage or pharmacological-related healing and providing novel diagnostic and clinical indications for highly patient-specific medical treatments.

  Leaders: P. Wriggers, M. Marino

  Year: 2015

  Sponsors: Alexander von Humboldt-Stiftung
• Patient-Specific FSI Analysis of the Blood Flow in the Thoracic Aorta

  The complexity of numerical modeling and simulation of blood flow in patient-specific thoracic aorta geometries leads to a number of major computational challenging issues. For instance, for an adequate simulation of the flow and pressure field, the incompressible Navier-Stokes equations have to be solved with the assumption that the relatively thin blood vessels suffer large displacements and undergo large elastic or visco-elastic deformations caused by the pulsatile blood flow. Subsequently, inaccurate predictions would be obtained for the hemodynamic quantities with the very simplifying rigid-wall assumption (CFD modeling). Moreover, when applying only the CFD modeling approach the essential phenomena of pressure wave propagation in cardiovascular systems are disregarded, however these phenomena are of major relevance for clinical practice. Accordingly, strongly coupled FSI schemes are inevitable for comprehensive blood flow simulations in arterial systems, and as blood and vascular walls have comparable densities, monolithic or at least partitioned strongly coupled FSI schemes are required for solving the multi-physics problem with its inherent significant added-mass effects.

  Leaders: P. Wriggers, B. Avci

  Team: B. Avci

  Year: 2016
• Computational modeling of in-stent restenosis

  This project aims to develop a computational tool for the modeling of the long-term behaviour of stent deployment, with a special focus on both current and prospective approaches. A multiscale description of arterial constitutive behaviour will be employed, including possible damage due to the stenting procedure. Moreover, the chemo-biological mechanisms underlying the growth and remodelling due to wound healing in tissues will be introduced. Therefore, a multiphysics computational framework will be developed and applied for the analysis of both metal and drug-eluting stents. The project will allow to identify the dominant mechanisms driving in-stent restenosis, deciphering the role of the different molecular species in the pathological remodeling of arteries. The final target is to optimise the clinical outcome of current approaches and propose targeted therapeutic approaches.

  Leaders: M. Marino

  Year: 2017

  Sponsors: Masterplan SmartBiotecs, MWK (Lower Saxony, Germany)
• Red blood cell simulation using a coupled shell-fluid analysis purely based on the SPH method

  If the rheological behavior of a Red-Blood-Cell (RBC) changes, for example due to some infection, it is reflected in its deformability when it passes through the microvessels. It can severely affect its proper function which is providing the oxygen and nutrient to the living cells. In this research project, a novel 3D numerical method has been developed to simulate RBCs based on the interaction between a shell-like solid structure and a fluid. RBC is assumed to be a thin shell encapsulating an internal fluid (Cytoplasm) which is submerged in an external fluid (blood plasma). The approach is entirely based on the smoothed particle hydrodynamics (SPH) method for both fluid and the shell structure. The method was motivated by the goal to benefit from the Lagrangian and meshless features of SPH in order to handle several complexities in the problem due to the coupling between the RBC membrane as a deformable elastic shell and interior/exterior fluids.

  Leaders: Peter Wriggers

  Team: Meisam Soleimani

  Year: 2017

  Lifespan: 3 Jahre

High Performance Computing (HPC)

• In many cases, massive parallel large-scale computations are indispensable for solving problems of practical interest. The numerical treatment of such class problems requires not only highly efficient scalable parallel solvers, moreover, efficient parallel algorithms covering the whole simulation pipeline – also including pre- and post-processing, mesh generation and design solvers considering uncertainties – are essential to model and to simulate large-scale or exascale class problems. The specific goal of this project is therefore the development and implementation of new parallel algorithms and methods that will allow to solve large-scale class problems with high efficiency.

  Leaders: P. Wriggers, B. Avci

  Team: B. Avci

  Year: 2014

  Sponsors: FP7 of the EU
• ISPH-based Simulation of the Selective Laser Melting Process

  Development of a thermo-mechanical model for the simulation of the SLM process.

  Leaders: Christian Weißenfels, Peter Wriggers

  Team: M.Sc. Jan-Philipp Fürstenau

  Year: 2017

Fracture Mechanics/ XFEM

• Crack propagation and crack coalescence in a multiscale framework

  In this project a numerical framework for propagating and intersecting cracks on micro and macro scales is set up. Modeling cracks using the eXtended Finite Element Method (XFEM) provides an accurate and efficient numerical framework to model propagating and intersecting cracks. Since cracks of different length scales are assumed, a multiscale method is applied in order to be numerical efficient.

  Leaders: S. Löhnert, P. Wriggers

  Team: M. Holl

  Year: 2010
• Large Deformation Cohesive-Zone Element for Fracture in Rubbery Polymers

  In this work, a 3D cohesive zone element is developed considering material and geometric nonlinearities and suitable for modeling large deformations and rotations.

  Leaders: P. Wriggers

  Team: A. B. Harish

  Year: 2015
• Nanoindentation for material property characterization

  In this work, techniques are developed for nanoindentation of soft polymers and brittle powdery materials and measurement of properties like modulus, hardness and fracture toughness.

  Leaders: P. Wriggers, S. Löhnert

  Team: A. B. Harish, V. Kruppernikova

  Year: 2016

Multiscale and multiphysics material modelling of polycrystalline metals and forming processes

• Creep deformation of nickel based superalloys

  Modeling of nickel based superalloys on two scales using crystal plasticity and XFEM methods.

  Leaders: P. Wriggers

  Team: Lukas Munk

  Year: 2018
• Modelling and simulation of the joining zone during the tailored forming process

  [Translate to Englisch:] The topic of project C4 is the multiphysical modelling and simulation of the microstructural behaviour of the joining zone during the tailored forming process. The goal is the determination of the macroscopic, effective, thermomechanical properties of joining zones during and after forming.The model will be able to capture the contact and diffusion processes during joining, the thermal and mechanical properties during forming as well as the material behaviour during heat treatment which is responsible for calibrating material properties.

  Leaders: F. Aldakheel, P. Wriggers

  Team: C. Böhm, F. Töller

  Year: 2019

  Sponsors: DFG im Rahmen des SFB 1153
• Water-induced damage mechanisms of cyclic loaded high-performance concretes

  The use of offshore wind energy is expanding and fatigue-loaded concrete structures are built that are submerged in water. This currently already applies to so-called grouted joints, where high-strength fine-grained concrete (grout) is used in the steel support structures of offshore wind turbines. Such constructions are subjected to several hundred million load cycles within their service life. An increased water content in the concrete results from the offshore exposure which is principally different to onshore constructions,. Comparatively few investigations of fatigue-tested concrete specimens immersed in water are documented in the literature. Despite the fact, that considerably scatterings occur in these results a clear tendency can be observed. Specimens that are immersed in water have a significantly lower fatigue resistance compared with specimens tested in air. Some investigations also show that fatigue-loaded concrete specimens immersed in water have a significant change in their fracture behaviour compared with specimens tested in air. This can be seen, in tests, for example, by ascending air bubbles, wash-outs of fine particles and premature crack initiation.Water-induced damage mechanisms in fatigue-loaded concrete have indeed been recognised in the past, but they were not identified and described with sufficient precision. Consequently, they cannot be quantified reliably. Based on the existing knowledge gap, the vast majority of these mechanisms have currently escaped numerical modelling and simulation.The aim of this research project is to understand, analyse and quantify macroscopically water-induced damage mechanisms of fatigue-loaded high-performance concretes in the Experimental-Virtual-Lab (EVL) with complementary very latest state-of-the-art experimental methods. At the same time, models will be created and numerically implemented on a micromechanical basis that enables proving of hypotheses that will be derived from the experimental investigations. The structural data serve for the validation of these models; the data will be determined by µCT scans, NMR measurements and mercury intrusion porosimetry.After a first clarification of the origin of mechanisms by the EVL, modelling at the macroscopic level will be attempted on the basis of the micromechanical investigations. In this way it will be verified, how the water influences the degradation behaviour of fatigue-loaded high-performance concretes and which additional active, water-induced damage mechanisms are decisively involved in the degradation process. It will be possible for the first time to carry out a prediction of the degradation behaviour of fatigue-loaded high-performance concretes immersed in water based on microstructurally orientated parameters.

  Leaders: Fadi Aldakheel, Peter Wriggers

  Year: 2020

  Sponsors: DFG SPP 2020, zweite Förderperiode

  Lifespan: 3 Jahre

Contact mechanics

• MULTISCALE CONTACT HOMOGENIZATION OF GRANULAR INTERFACES

  Dry granular third bodies are frequently encountered at multiple scales of contact interfaces in contexts that range from mechanical problems of tire traction and semiconductor manufacturing to biological problems of wear debris generation and mobility in implant joints. The investigations that are envisaged within this proposal will provide further insight into the modeling and simulation of third body effects in a fully nonlinear three-dimensional virtual setting that accounts for inelastic phenomena.

  Leaders: P. Wriggers, I. Temizer

  Team: R. Weidlich

  Year: 2009
• Mutiscale FEM approach for rubber friction on rough surfaces

  Understanding the frictional behaviour of elastomers on rough surfaces is of high practical importance in many industrial applications. For example the traction of a tire is directly linked to the material properties of the considered elastomer and the surface conditions of the road track. One goal of our studies is to gain a deeper understanding of the underlying contact physics at all length scales. Another aim is to determine a macroscopic coefficient of friction for varying material and surface properties and to validate the results with experimental data.

  Leaders: P. Wriggers

  Team: P. Wagner

  Year: 2012
• Contact models for soil mechanics

  The installation of foundations influences strongly the load bearing capacity of the soil. The large discrepancy between experimental and numerical results, using Coulomb friction law for modeling the soil structure interaction, points out that new strategies to solve this kind of problems are necessary. Experimental observations show that for rough surfaces of the structure the friction angle at the contact zone corresponds to the friction angle of the soil. This leads to the conclusion that the contact zone lies completely within the soil. A way to improve the friction laws for soil structure interactions is to project the soil models onto the contact surface which is the motivation of this work. </a></p>

  Leaders: P. Wriggers

  Team: C. Weißenfels

  Year: 2012
• Application of the Virtual Element Method to Non-Conforming Contact Interfaces

  When using standard Finite Elements the discretization is subject to limitations depending on the element geometry. In contrast to this the Virtual Element Method offers the possibility for elements with an arbitrary number of nodes and special geometries like non-convex polygons or hanging nodes. In this Project the application of the Virtual Elements to different problems is investigated. Here it is used to create an efficient contact discretization.

  Leaders: P. Wriggers

  Team: W. Rust

  Year: 2014
• Towards multiscale modeling of Abrasive wear

  The work is motivated towards understanding wear as a multiscale-multiphysics approach. A 3D framework is developed to simulate cracks propagation in a microstructure due to contact loading to eventually predict wear trends in filled elastomeric compounds.

  Leaders: P. Wriggers

  Team: A. B. Harish

  Year: 2015

Additive Manufacturing

• Process Simulation for Selective Laser Melting

  A phase change model for solution with the meshfree Galerkin OTM method is developed.

  Leaders: Christian Weißenfels, Peter Wriggers

  Team: M.Sc. Henning Wessels

  Year: 2016
• ISPH-based Simulation of the Selective Laser Melting Process

  Development of a thermo-mechanical model for the simulation of the SLM process.

  Leaders: Christian Weißenfels, Peter Wriggers

  Team: M.Sc. Jan-Philipp Fürstenau

  Year: 2017

Discrete Elements and Molecular Dynamics

• Discrete Element Method

  This project is concerned with the development of a discrete element method (DEM) code for the simulation of large particle systems in 3-D, where also complex moving boundary geometries can be taken into account. The DEM is a well established numerical method to simulate systems consisting of granular matter. Granular mixing, tumbling mills, transport of particles via conveyor belts or screw conveyors are just some examples of important particulate processes in industry sectors like mining, pharmaceutical and food industries. For such systems, the optimization of the design variables as well as the appropriate choice of the operating parameters is still a difficult and a challenging task.

  Leaders: P. Wriggers

  Team: B. Avci

  Year: 2011

Artificial Intelligence

• Using Machine Learning to Improve the Modelling of Machining and Cutting Processes

  Metal cutting is a fundamental process in industrial production. The fast and accurate on-line prediction of metal cutting processes is crucial for the Intelligent Manufacturing (IM). With the advent of high-speed computing, robust numerical algorithms and machine learning technology, computational modelling serves as a tool for not only accurate but also fast predicting the complex machining processes and understanding the complex physics. In this work, the machine learning based numerical model is developed for simulation of metal cutting processes.

  Leaders: C. Weißenfels, P. Wriggers

  Team: M.Sc. Dengpeng Huang

  Year: 2018

  Sponsors: China Scholarship Council (CSC)
• Physics-Informed Data-Driven Simulation

  This project investigates to what extent simulation with neural networks on the one hand and data-based empirical modeling on the other hand can be combined in a symbiotic manner. The ultimate goal is the generation of reliable models for complex dynamical systems known as digital twins.

  Leaders: H. Wessels, P. Wriggers

  Team: H. Wessels

  Year: 2020

Finite element technology

• Application of the Virtual Element Method to Non-Conforming Contact Interfaces

  When using standard Finite Elements the discretization is subject to limitations depending on the element geometry. In contrast to this the Virtual Element Method offers the possibility for elements with an arbitrary number of nodes and special geometries like non-convex polygons or hanging nodes. In this Project the application of the Virtual Elements to different problems is investigated. Here it is used to create an efficient contact discretization.

  Leaders: P. Wriggers

  Team: W. Rust

  Year: 2014
• Large Deformation Cohesive-Zone Element for Fracture in Rubbery Polymers

  In this work, a 3D cohesive zone element is developed considering material and geometric nonlinearities and suitable for modeling large deformations and rotations.

  Leaders: P. Wriggers

  Team: A. B. Harish

  Year: 2015
• The stress and fatigue analysis of the transportation line

  The conveyor of the production line in Salzgitter Flachstahl GmbH which carries the steel coils is going to be subjected to an extra load due to the bigger coil size. The objective is to do a structural analysis of the conveyor to see if the safety factor of structure is still in the allowable region. Since, the loading condition is naturally variable due to continuously feeding the moving conveyor with steel coils, a fatigue analysis is required in addition to an ordinary static analysis.

  Leaders: Peter Wriggers

  Team: Meisam Soleimani

  Year: 2018