Short Info
DAMASK is a unified multi-physics crystal plasticity simulation package [1]. The solution of continuum mechanical boundary value problems requires a constitutive response that connects deformation and stress at each material point. This problem is solved in DAMASK on the basis of crystal plasticity using a variety of constitutive models and homogenization approaches. However, treating mechanics in isolation is no longer sufficient to study emergent advanced high-strength materials. In these materials, deformation happens interrelated with displacive phase transformation, significant heating, and potential damage evolution. Therefore, DAMASK is capable of handling multi-physics problems. Following a modular approach, additional field equations are solved in a fully coupled way using a staggered approach.
📅 11 June 2025 🕑 03:15 PM 📍 Seminar Room IC 03/754
Short Info
Prof. Weimann will give a broad overview on her research.
📅 19 May 2025 🕑 02:15 PM 📍 Seminar Room IC 03/752
Short Info
Physics-augmented neural network (PANN) constitutive models combine the flexibility of neural networks with a sound mechanical basis. In this presentation, different hyperelastic PANN constitutive models fulfilling the polyconvexity condition are discussed for purely mechanical, parametrized, and electro-mechanical material behavior. The models are applied to different material datasets, including synthetic data of homogenized microstructures and experimental data of 3D printing materials. Thereby, both the benefits and limits of polyconvex constitutive models are discussed.
📅 19 May 2025 🕑 02:15 PM 📍 Seminar Room IC 03/752
Short Info
Micromechanics seeks to provide constitutive models of heterogeneous materials based on the knowledge of the material behavior of the individual materials constituting the microstructure and the geometric arrangement of these materials within the microstructure. Modern computational micromechanics methods are used to compute the nonlinear response of materials with quite complex microstructure and permit to reduce the experimental effort necessary to characterize the relevant material behavior, in particular for long-term loading. Due to the complex microstructures characteristic for materials used in industry, computational methods based on regular, i.e., Cartesian, grids are frequently used. Computational strategies based on the fast Fourier transform (FFT) turn out to be particularly performing due to the excellent implementation of available FFT packages and the automatic preconditioning provided by the formulation. The talk is intended to give a gentle introduction to such FFT-based methods for micromechanics with a focus on ''modern'' developments, i.e., the use of finite element and finite difference discretizations. Moreover, we plan to discuss how to overcome the limitation to periodic boundary conditions traditionally associated with FFT-based methods for micromechanics.
📅 10 September 2024 🕑 02:00 PM 📍 Seminar Room IC03/604
Short Info
Cohesive zone models represent a well-established and powerful framework for non-linear fracture mechanics. In contrast to classic bulk material models, they are based on traction-separation laws. As far as the finite element method is concerned, cohesive zone models are most often implemented by means of zero-thickness interface elements. However, since the geometry of the material interfaces such as that of cracks is usually not known beforehand but part of the solution, tracking of the involved interfaces becomes very challenging for zero-thickness interface elements. By way of contrast, phase field models do not show this problem. In this talk, a phase field approximation of cohesive zone models is discussed. Starting from the underlying sharp interface cohesive model, the phase field method for brittle fracture is first revisited. Particularly, it is shown that different mathematical solution concepts (e.g., local energy minima vs. global energy minima) may lead to different solutions – sometimes they even violate physics observations. Within the second part of the talk, the framework for brittle fracture is extended to cohesive zone models. In contrast to previous works, the three-dimensional phase field models is shown to converge to its underlying sharp interface model.
📅 5 December 2023 🕑 02:00 PM 📍 Seminar Room of the Chair of Continuum Mechanics
Abstract
The GAMM student chapters from Hannover, Bochum and Hamburg are organising a pretty special event: a joint Science Slam in Hannover! The idea behind the event is to gather young researchers (PhD/ MSc) working in the areas of maths and mechanics for a more informal exchange of research ideas and experiences.
📅 30 June 2023 🕑 11:45 AM 📍 Leibniz University Hannover, Welfergarten 1, 30167 Hannover
Short Info
Least squares FEM is a special discretization technique with certain advantages and disadvantages. In this talk Prof. Schröder will cover those aspects with examples from fluid-structure interaction (FSI) problems. Stability and convergence properties as well as incorporation of the symmetry of the stress tensor will be discussed.
📅 23 May 2023 🕑 11:00 AM 📍 Seminar Room of the Chair of Continuum Mechanics
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Optimization and Machine Learning are closely intertwined fields. Machine learning is a rapidly growing field with excellent visibility due to many recent successes. Its underlying technology layer, optimization methods, does not enjoy the same public attention. Interestingly, in both fields, there exist nature-inspired methods: neural networks and evolutionary algorithms. In this talk, I will present current research going on in both fields within the research group Optimization of Adaptive Systems at the Institute for Neural Computation. Topics span a wide range from applied mathematical research all the way to real-world applications.
📅 24 March 2023 🕑 02:00 PM 📍 Seminar Room of the Chair of Continuum Mechanics
Short Info
In this talk I will review major convexity notions in nonlinear elasticity and its connection to various domains of applications. Topics include occurrence of microstructures, Morrey’s Problem, Quasiconvex relaxation but also generalized continuum models and plate and shells.
📅 20 December 2022 🕑 02:00 PM 📍 Seminar Room of the Chair of Continuum Mechanics
Short Info
Architected materials (or mechanical metamaterials) with well designed macroscale properties and performance based on a careful design of the microscale architecture have gained popularity for applications ranging from wave guides and cloaks to patient-specific implants to mechanical logic and ultralow-weight structural materials. While the forward homogenization challenge (i.e., the computation of effective material properties for a given microscale architecture) is well established with numerous modeling techniques available, the inverse homogenization challenge (i.e., the identification of microscale architectures that yield specific target properties on the macroscale) is still an open challenge for many properties and metamaterial designs. We here discuss new strategies based on machine learning to tackle this inverse problem, which can be applied equally to periodic truss architectures and non-periodic spinodoid designs, for which we highlight opportunities and applications.
📅 25 October 2022 🕑 01:00 PM 📍 Zoom
Short Info
Prof. Philipp Junker will talk, who used to work here, at our very own RUB, though now he holds a professorship at the Leibniz Universität in Hannover. His talk carries the very catchy title An extended Hamilton principle as unifying theory for coupled problems and dissipative microstructure evolution. Prof. Junker is going to cover aspects about extended hamiltion principle for deriving the evolution laws of material models.
📅 15 March 2022 🕑 05:00 PM 📍 Zoom
Short Info
Automatic Differentation is a powerful technique that solves a variety of problems of symbolic and numerical differentiation. In our day to day scientific work automatic differentiation can be helpful by providing exact derivatives of generic functions with minimal implementational cost.
📅 11 January 2022 🕑 04:00 PM 📍 Zoom