Logo Leibniz Universität Hannover
Logo: Institute of Continuum Mechanics/Leibniz Universität Hannover
Logo Leibniz Universität Hannover
Logo: Institute of Continuum Mechanics/Leibniz Universität Hannover
  • Zielgruppen
  • Suche
 

Finished Research Projects

Contact Mechanics

Mutiscale FEM approach for rubber friction on rough surfaces

Bild zum Projekt Mutiscale FEM approach for rubber friction on rough surfaces

Supervisor:

P. Wriggers

Researcher:

P. Wagner

Brief description:

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.

 

| details |

 

Analysis of local friction between rubber and dry and wet surfaces

Bild zum Projekt Analysis of local friction between rubber and dry and wet surfaces

Supervisor:

P. Wriggers, R. A. Sauer

Researcher:

J. Dobberstein

Brief description:

A prediction of the friction behavior of a rubber compound sliding over a road surface is an important topic in tire industry. Within this project the parameters which mainly influence the friction between a single tread block and a rough surface are investigated. The relevant physical mechanism of contact between a tread block and a rough surface, both wet or dry has to be understood. To validate the model a large number of test rigs is investigated at the Institute of Dynamics and Vibration Research (IDS).

 

| details |

 

Coupled Contact of Lubricated Contact

 

Supervisor:

P. Wriggers

Researcher:

M. Budt

Brief description:

[Translate to Englisch:] In many engineering applications fluid lubricants are used to separate two solid bodies that rub against one another to minimize friction. Such devices are referred to as hydrodynamic bearings. There exist a large variety of bearings for translational and rotational movement. For engineers designing such bearing, computational methods can deliver useful information on its performance characteristics prior to its manufacturing. Within this project a three-dimensional finite element model is developed, that describes lubricated contact between two bodies with rough surfaces.

 

 

Contiuum Mechanical Modelling of Self-Cleaning Surface Mechanisms

 

Supervisor:

R. A. Sauer

Researcher:

M.Osman

Brief description:

Some biological surfaces, like several plant leaves, exhibit remarkable self cleaning mechanism. These are called hydrophobic surfaces, where the water does not coat the surface but rather forms small droplets which then roll-off easily on inclined surfaces and sweep foreign pollutants, like dirt or germ particles, away from the surface. A continuum mechanical model suitable for computational multiscale analysis is therefore required for describing the interaction between the water droplet, the pollutant particle and the substrate surface. This model provides better understanding of basic droplet-substrate interaction characteristics such as contact angle, roll off angle and droplet deformation due to the microstructure of the substrate. The surface self-cleaning capabilities can be therefore improved by optimizing the artificial surface microstructure.

 

| details |

 

Frictional contact of elastomer materials on rough rigid surfaces

 

Supervisor:

P. Wriggers

Researcher:

J. Reinelt

Brief description:

The purpose of this work is the derivation of a friction law for rubber materials on rough tracks by numerical investigations. Rubber friction includes a number of influences like hysteresis due to material damping, adhesional effects or thermomechanical coupling.

 

| details |

 

Constitutive Modelling of Materials

Dynamic crack propagation using the XFEM

 

Supervisor:

P. Wriggers, S. Löhnert

Researcher:

D. Nolte

Brief description:

Imperfections in composite materials can occur at interfaces but also within the matrix material, particles or fibers. These imperfections often lead to cracks and thus are responsible for degradation and failure of these heterogeneous materials. In this project the attention turns to the dynamic crack propagation. Therefore a numerical approach by using the eXtended Finite Element Method (XFEM) to describe the problem within heterogeneous materials will be developed. The XFEM has proven to be adequate to handle cracks and heterogeneities in a precise geometrical and numerical framework.

 

| details |

 

Micromechanical Modelling of inelastic grain boundary effects in polycrystalline materials

Bild zum Projekt Mikromechanische Modellierung von inelastischen Korngrenzeneffekten in polykristallinen Materialien

Supervisor:

Britta Hirschberger

Researcher:

H. Clasen

Duration:

1 year

Funded by:

Leibniz Universität Hannover via programme "Wege in die Forschung II"

Brief description:

The research project focuses on the computational materials modelling of metals microstructure. Within the project, polycrystalline materials shall be micromechanically investigated by means of dislocation-based crystal plasticity. The goal is to gain a clearer understanding in the nonlocal behaviour and to obtain useful models for the prediction of the inelastic response, which become relevant in applications such as micro-manufactured structures.

 

| details |

 

ADAPTIVE MULTISCALE MODELING AND ANALYSIS OF HETEROGENEOUS MATERIALS

Bild zum Projekt ADAPTIVE MULTISCALE MODELING AND ANALYSIS OF HETEROGENEOUS MATERIALS

Supervisor:

P. Wriggers, I. Temizer

Brief description:

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.

 

| details |

 

FAILURE ANALYSIS - ERROR ESTIMATION FOR MULTISCALE METHODS

Bild zum Projekt FAILURE ANALYSIS - ERROR ESTIMATION FOR MULTISCALE METHODS

Supervisor:

P. Wriggers

Researcher:

N. Hajibeik

Brief description:

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.

 

| details |

 

DEVELOPMENT OF A MATERIAL MODEL FOR METAL SHEETS AT FINITE DEFORMATION

Bild zum Projekt DEVELOPMENT OF A MATERIAL MODEL FOR METAL SHEETS AT FINITE DEFORMATION

Supervisor:

P. Wriggers, S. Löhnert

Researcher:

E. Lehmann, S. Zeller

Brief description:

[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.

 

| details |

 

Simulating the microstructure of cement-based construction materials

 

Supervisor:

P. Wriggers, S. Löhnert

Researcher:

N. Dabagh

Brief description:

In this thesis three-dimensional computational homogenization of hardened cement paste (HCP) including micro-structural damage due to frost is introduced. Based on a computer-tomography at a resolution of 1µm a finite-element model of HCP is developed with different elastic and inelastic constitutive equations for the three parts unhydrated residual clinker, pores, and hydration products.

 

| details |

 

Einfluss inelastischer Effekte auf die Reibung in zyklischen Prozessen

 

Supervisor:

D. Besdo

Brief description:

Bei der Modellierung der Polreibung von Reifen ist eine große Anzahl einzelner Effekte zu berücksichtigen, insbesondere, dass sich Gummi mit ursprünglich einheitlichem Ausgangszustand nach einiger Verformung von Ort zu Ort sehr unterschiedlich verhalten kann. Die Ursache ist, dass die so genannte Gummi-Elastizität sehr beträchtliche inelastische Anteile aufweist, die von den vorangegangenen Lastzyklen, insbesondere von früheren Verformungsmaxima signifikant abhängen (Mullins-Effekt). Somit ist bei einer genauen Modellierung des Rollkontaktes unbedingt die Heterogenität des Vor-Verformungszustandes und ihr Einfluss auf die inelastischen Effekte zu beachten.

 

| details |

 

Multiscalemodelling/ Multiphysics

RAMWASS - Integrated Decision Support System for Risk Assessment and Management

Bild zum Projekt RAMWASS - Integrated Decision Support System for Risk Assessment and Management

Supervisor:

P. Wriggers

Researcher:

B. Avci

Brief description:

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.

 

| details |

 

Numerical modeling of electrical contacts

Bild zum Projekt Numerical modeling of electrical contacts

Supervisor:

P. Wriggers

Researcher:

C. Weißenfels

Brief description:

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.

 

| details |

 

MULTIPHYSICS COMPUTATIONAL HOMOGENIZATION METHODOLOGIES

Bild zum Projekt MULTIPHYSICS COMPUTATIONAL HOMOGENIZATION METHODOLOGIES

Supervisor:

P. Wriggers, I. Temizer

Brief description:

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.

 

| details |

 

Biomechanics

Advanced multiscale computational mechanics for physiopathological behavior analysis of tissues and organs

Bild zum Projekt Advanced multiscale computational mechanics for physiopathological behavior analysis of tissues and organs

Supervisor:

P. Wriggers, M. Marino

Funded by:

Alexander von Humboldt-Stiftung

Brief description:

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.

 

| details |

 

SFB 599 TP R6 – Degradable Osteosynthese

Bild zum Projekt SFB 599 TP R6 – Degradable Osteosynthese-Systeme

Supervisor:

P. Wriggers

Researcher:

S. Besdo

Funded by:

DFG im Rahmen des SFB 599

Brief description:

Within the framework of SFB 599 osteosynthesis systems for fracture stabilization out of magnesium alloys are being developed. The advantage of magnesium is that the body needs it for its metabolism and it degrades over time. Due to the mechanical properties and the degradation of magnesium alloys, it is necessary to adjust the implant design. First, the primary stability of implant-bone composite is investigated using finite element analysis, before the implants are tested on animals. In a second step, the degradation has to be integrated into the simulation. Therefore, different simulation methods have been developed and should be adapted to results from in vitro experiments. Furthermore, the magnesium degradation will be considered in the simulation of bone healing.

 

| details |

 

SFB 599 TP D1 – Functionalized middle ear prostheses

Bild zum Projekt SFB 599 TP D1 – Funktionalisierte Mittelohrprothesen

Supervisor:

P. Wriggers

Researcher:

S. Besdo, D. Doniga-Crivat

Funded by:

DFG im Rahmen des SFB 599

Brief description:

The participating institutions in the sub-project D1 of the SFB 599 (Institute of Inorganic Chemistry, LUH, Helmholtz Centre for Infection Research, Ear, Nose and Throat Clinic, Hannover Medical School, IKM) have the aim to develop an optimized middle ear prosthesis. This is done through the use of newly developed biomaterials on the one hand and by using simulation techniques to optimize the design on the other hand. During the last funding period, the focus of the simulation was on the healthy ossicular chain. In the third period the contact between the implant and the tympanic membrane should be simulated. Polymer cushions will be used to create a tissue-friendly interface that enables a uniform loading of the eardrum.

 

| details |

 

Improvement of cardiovascular Implants and a FE-Framework for Degradation of Mg-Alloys

Bild zum Projekt Weiterentwicklung von kardiovaskulären Implantaten und finite Element Modellierung der Degradation von Mg-Legierungen

Supervisor:

P. Wriggers, J. Lamon, S. Besdo

Researcher:

M. Weidling

Funded by:

DFG within IRTG 1627

Brief description:

A surgical option is to replace damaged myocardial tissue, e. g. after a heart attack, with tissue transplants. Problematic is the minor initial strength of these biological grafts to resist loads of the high pressure system. Therefore, scaffolds are developed to mechanically support these grafts. Until now, developed scaffolds do not achieve the required durability. With use of the finite element method, simulations are performed where the scaffolds are deformed according to the heart movement. This allows identifying highly strained regions within the implant that need design changes. Another approach to reduce stresses is preforming scaffolds according to the heart curvature preoperatively. Further, new scaffold designs are developed and tested.  Scaffolds are made from magnesium alloys, which can be resorbed by the body. This degradation affects the mechanical behavior of the implants under load. There are FE simulations developed in which the magnesium degradation is considered.

 

| details |

 

Investigation of the behavior of the crystalline lens accommodation by introducing femtosecond laser-induced (fs-laser) cut surfaces

Bild zum Projekt Untersuchung des Akkommodationsverhaltens der Augenlinse nach Einbringung Femtosekun-den-Laser-induzierter (fs-Laser) Schnittflächen

Supervisor:

S. Besdo

Funded by:

DFG im Normalverfahren

Brief description:

This project is conducted in cooperation with the Laser Zentrum Hannover eV. With age, the ability of the human eye lens to adjust from the distant view of the near vision increases. There is still no satisfactory method of treatment for the so called pres-byopie. However, it was shown that it is possible to influence the flexibility of the lens by introducing micro-cuts with a femtosecond laser (fs-Lentotomie). The aim of this project is to develop a method which makes it possible to predict the changes of accommodation behavior of ophthalmic lenses after cutting using finite element analyses.

 

| details |

 

Fracture Mechanics/ XFEM

Dynamic crack propagation using the XFEM

 

Supervisor:

P. Wriggers, S. Löhnert

Researcher:

D. Nolte

Brief description:

Imperfections in composite materials can occur at interfaces but also within the matrix material, particles or fibers. These imperfections often lead to cracks and thus are responsible for degradation and failure of these heterogeneous materials. In this project the attention turns to the dynamic crack propagation. Therefore a numerical approach by using the eXtended Finite Element Method (XFEM) to describe the problem within heterogeneous materials will be developed. The XFEM has proven to be adequate to handle cracks and heterogeneities in a precise geometrical and numerical framework.

 

| details |