Ottmar Klaas

• PhD
• Developer at Simmetrix

The development of high-fidelity mechanical property prediction models for the design of polycrystalline materials relies on large volumes of microstructural feature data. Concurrently, at these same scales, the deformation fields that develop during mechanical loading can be highly heterogeneous. Spatially correlated measurements of 3D microstruct...

Geometric modeling techniques and automated volume meshing algorithms available in CAD/CAE technology can be used to close the gap efficiently between a 3D microstructure representation and a finite element simulation. 3D microstructure examples are presented to describe techniques to (i) prepare a 3D voxel dataset, (ii) create a valid geometric mo...

This presentation is about converting voxel level datasets from different sources (serial sectioning, computed tomography, synthetic representations) into discrete geometry suitable for volumetric meshing and FE simulations. Examples are provided.

Cell-generated tractions play an important role in various physiological and pathological processes such as stem-cell differentiation, cell migration, wound healing, and cancer metastasis. Traction force microscopy (TFM) is a technique for quantifying cellular tractions during cell-matrix interactions. Most applications of this technique have heret...

Tractions exerted by cells on extra-cellular matrices (ECM) play a crucial role in many biological processes such as wound healing, angiogenesis and metastasis, as well as in many basic cellular functions such as biochemical signaling, proliferation and differentiation. Traction forces are typically quantified through traction force microscopy (TFM...

Realistic simulation of electromagnetic wave propagation in the actual human body can expedite the investigation of the phenomenon of harvesting implanted devices using wireless powering coupled from external sources. The parallel electromagnetics code suite ACE3P developed at SLAC National Accelerator Laboratory is based on the finite element meth...

This chapter presents a set of procedures that start from image data to construct a non-manifold geometric model that supports the effective generation of meshes with the types of mesh configurations and gradations needed for efficient simulations. The types of operations needed to process the image information before and during the creation of the...

Small scale features and processes occurring at a nanometer and femtoseconds scales have a profound impact on what happens at a larger scale and over extensive period of time. The primary objective of this volume is to reflect the-state-of-the art in multiscale mathematics, modeling and simulations and to address the following barriers: What is the...

Building on a general abstraction of the steps and transformations of a multiscale analysis, this chapter considers an approach to the development of multiscale simulation in which interoperable components can be effectively combined to address a wide range of multiscale simulations. Key concerns in the development of these interoperable components...

Development of the next generation of RF devices is in progress with research on sheet beam and multiple beam devices on-going at several institutions. Analysis of inherently three dimensional devices requires a new set of analytical tools to model the electromagnetic fields and the behavior of electron and ion beams. Existing codes, such as HFSS a...

The Beam Optics Analysis (BOA) is a 3D, finite element, charged particle, trajectory code with adaptive meshing. The program operates within AutoCAD, which is used for geometric and attribute input. Post processing is performed using the graphics program Visualization ToolKit. The program is fully relativistic and includes electric and magnetic fie...

A modern 3D finite element charged particle code has been developed with adaptive meshing. The new code includes both electrostatic and magnetostatic field solvers and particle pusher. The magnetic field solver uses tangential vector finite elements to solve for the vector potential. Results of some simple examples are given to demonstrate the code...

This paper presents a higher order stabilized finite element formulation for hyperelastic large deformation problems involving incompressible or nearly incompressible materials. A Lagrangian finite element formulation is presented where mesh dependent terms are added element-wise to enhance the stability of the mixed finite element formulation. A r...

In this paper, we present a new point of view for e#ciently managing general parallel mesh representations. Taking as a starting point the Algorithm Oriented Mesh Database (AOMD) of [12] we extend the concepts to a parallel mesh representation. The important aspects of parallel adaptivity and dynamic load balancing are discussed. We finally show ho...

The Partition of Unity Method (PUM) can be used to numerically solve a set of differential equations on a domain W. The method is based on the definition of overlapping patches comprising a cover of the domain W. For an efficient implementation it is important that the interaction between the patches themselves, and between the patches and the boun...

A simulation environment to support engineering design embedded in an enterprise-wide information system is presented. The environment consists of a set of structures and managers housing the problem definition, tools for controlling the simulation model construction and execution, and the interaction of simulation processes with the product data m...

This paper presents a stabilized finite element formulation for steady-state viscoplastic flow and a simple strategy for solving the resulting non-linear equations with a Newton–Raphson algorithm. An Eulerian stabilized finite element formulation is presented, where mesh dependent terms are added element-wise to enhance the stability of the mixed f...

A stabilized, mixed finite element method for viscoplastic flow analysis is presented. Preliminary results show promise for modeling steady-state bulk forming processes. In this work, the Ladyzenskaya-Babuska-Brezzi (LBB) condition is circumvented by adding mesh dependent terms (stabilization terms), which are functions of the residual of the Euler...

A simulation environment to support engineering design embedded in an enterprise wide information system is presented. The environment consists of a set of structures and managers housing the problem definition, and tools controlling the construction of the simulation domain, the simulation itself, and the interaction with the product data manageme...

The Partition of Unity Method (PUM) can be used to numerically solve a set of differential equations on a domain Ω. The method is based on the definition of overlapping patches Ωi comprising a cover {Ωi } of the domain Ω. For an efficient implementation it is important that the interaction between the patches themselves, and between the patches and...

A stabilized, mixed finite element method for viscoplastic flow analysis is presented. Preliminary results show promise for modeling steady-state bulk forming processes. In this work, the Ladyzenskaya-Babuska-Brezzi (LBB) condition is circumvented by adding mesh dependent terms (stabilization terms), which are functions of the residual of the Euler...

A stabilized mixed finite element method for finite elasticity is presented. The method circumvents the fulfillment of the Ladyzenskaya–Babuska–Brezzi condition by adding mesh-dependent terms, which are functions of the residuals of the Euler–Lagrange equations, to the usual Galerkin method. The weak form and the linearized weak form are presented...

A stabilized mixed finite element method for finite elasticity is presented. The method circumvents the fulfillment of the Ladyzenskaya–Babuska–Brezzi condition by adding mesh-dependent terms, which are functions of the residuals of the Euler–Lagrange equations, to the usual Galerkin method. The weak form and the linearized weak form are presented...

A complete set of data structures and mesh modification tools for effectively defining unstructured threedimensional multigrids on general curved domains is presented. The mesh adaptive procedures can be used for generating hierarchies of unstructured grids by means of uniform or local refinement and coarsening, while a local retriangulation algori...

The computation of limit and bifurcation points in structural mechanics using iterative preconditioned Lanczos solvers is studied. Contrary to classical implementations of algorithms for the calculation of limit and bifurcation points, which depend in general strongly on observing the diagonal elements of the decomposed matrix – obtained by a Gauß-...

This paper presents the formulation and numerical implementation of a physically nonlinear BDM element for plane stress. The BDM element is based on the dual extended Prange-Hellinger-Reissner functional. We discuss in detail, the linearization of the extended functional needed for solving the system of nonlinear equations with a Newton procedure....

We investigate a coupling of mixed finite elements and Galerkin boundary elements which is stable and leads to symmetric matrices. In the FEM domain, a posteriori error estimates are employed to refine the mesh adaptively. Numerical results are given for plane strain problems.

We establish a posteriori error indicators for mixed finite elements in plane elasticity. The error estimators refer to residuals of the strong equations and to jumps of the displacements on interelement boundaries. For the BDM elements of lowest order, the error indicators are computed with displacement fields which are obtained by a postprocessin...

A parallel implementation of an adaptive finite element program is treated which is characterized by an underlying parallel dynamic data structure based on linked lists and tree structures. In conjunction with a conjugate gradient solver an efficient methodology for treating adaptive finite element systems is shown. This is achieved by precondition...

A parallel implementation of an adaptive finite element program is treated which is characterized by an underlying parallel dynamic data structure based on linked lists and tree structures. In conjunction with a conjugate gradient solver an efficient methodology for treating adaptive finite element systems is shown. This is achieved by precondition...

In the present work we consider aspects of the formulation and numerical implementation of the BDM element [1, 2]. This element is based on an extended dual Hellinger-Reissner principle which leads to optimal convergence rates for the stresses and displacements. The element is characterized by a non-symmetric approximation of the stress field [3],...

This paper presents the development of a parallel finite element algorithm for a MIMD parallel computer. The elements are distributed, onto the processors, in such a way that neighbouring elements are placed onto neighbouring processors. This guarantees a good load-balancing even in physically non-linear computations. The distribution of the column...

In der vorliegenden Arbeit wird die Parallelisierung der direkten Randelementmethode für zweidimensionale linearelastische Problemstellungen in der Strukturmechanik beschrieben. Nach einer kurzen Darstellung der verwendeten Randelementdiskretisierung gehen wir auf die Parallelisierung durch Datenverteilung ein. Die Effizienz dieser Parallelisierung...