LECTURE LINES

Lecture line physical modeling

Module 1.1 - Innovative Finite Element Simulations

This module combines a theoretical with a hands-on approach. It contains theoretical input on continuum mechanics and the Finite Element Method. In several hands-on sessions the students jointly work on the implementation, analysis, and visualization of different example problems from continuum and fracture mechanics as well as materials science and manufacturing. For the hands-on sessions, the doctoral students are provided with a VirtualBox environment containing a basic version of the FORTRAN based Finite Element code FEAP (Finite Element Analysis Program), a noncommercial Finite Element tool, which is developed at UC Berkeley. The open-source visualization tool Paraview is used for the visualization and analysis of simulation results during the hands-on sessions. The files provided for the hands-on sessions include input and batch files to define the finite element models and execute the simulations. The files are completed and modified during the hands-on sessions.

The lecture starts with an introduction to linear continuum mechanics. The basic concepts of the Finite Element Method – reformulation of the boundary value problem in terms of weak forms, interpolation of field quantities by means of Finite Element shape functions and isoparametric approximation of displacements and the geometry – are introduced. In the first hands-on session the doctoral students get acquainted with the structure of the Finite Element code and the necessary steps to perform simulations.

Finite deformation nonlinear continuum mechanical problems render a nonlinear set of equations after discretization with Finite Elements. The solution of such nonlinear systems of equation requires iterative solution strategies like Newton’s method, which is based on subsequent linearizations of the original set of equations. The implementation of these linearization techniques within the Finite Element setting are discussed in the lecture and illustrated by examples in the corresponding hands-on session.

The phase field method is an elegant approach to model and simulate fracture processes. The core of the approach is to model cracks by means of an order parameter which transitions smoothly between 0 in broken and 1 in undamaged material. In the Finite Element implementation, the phase field order parameter serves as an additional nodal degree of freedom complementing the nodal displacements. Within the hands-on part of the session, the students explore and discuss different features of the model and the implementation.

Module 1.2 - Molecular Modeling

The lecture starts with a discussion of the basic concepts of modeling and simulation. The relation between mathematical models and their evaluation by computer simulation on the one side and the real world and its investigation by classical experiments on the other and the role of testing in the model development is clarified. This includes aspects from philosophy of science. An overview of molecular simulation techniques is given, ranging from quantum chemical simulations over atomistic simulations based on classical force fields to coarse grained simulations. This lecture focusses on the atomistic simulation.

Basics of interatomic interactions and force fields used in atomistic modeling are explained as well as the challenges in force field development. The course also contains a short primer in statistical mechanics that enables the students to understand how the atomistic level is linked to the macroscopic level. The particular challenges of atomistic simulations are addressed, and it is clarified why methods from high-performance computing are generally needed to tackle the simulation tasks in that field. An overview of established codes for atomistic simulations is given. Simulation errors are discussed as well. The amount of data generated in atomistic simulations is extremely large. Techniques for the handling of this data, its interpretation and visualization are presented.

This theoretical knowledge is combined with case studies on problems which are relevant for the research in IRTG 2057. The lecture closes with hands-on computer experiments which are carried out by the students. Hence, a bridge is built from basic theoretical knowledge to its practical application.

Module 1.3 - Applied Concepts in Modeling Tribological Systems

This module provides students with fundamental knowledge and practical skills in physical modeling of tribological systems. The course combines theoretical understanding with practical experience and covers rheological material modelling, and friction and wear of tribological systems. At the beginning of each topic, an overview of existing, fundamental models will be given, which will be transferred into applications during practical exercises.

The hands-on sessions will take place in the CAD-Pool of the faculty at TU Kaiserslautern, such that the doctoral students are provided with Matlab. The practical part of this module aims to give an introduction to Matlab based on special problems but provides skills with which the students are able to solve also new problems related to their special research work. For the hands-on session, a teacher’s guide will be allocated with the most important Matlab functions used for the exercises. Additionally, files with the basic program’s structure are provided for support. Nevertheless, the goal of the exercises is that the doctoral students develop small Matlab routines by themselves to simulate selected case problems.

The module starts with an overview of rheological models and basic concepts for elastic, viscous and plastic material behavior. For a more realistic material behavior, these concepts will be enhanced, and combined rheological models evaluated. To close the gap between theory and practical application, parameterization strategies of these models by measurements will be discussed. In the practical part, the performance of several rheological models will be implemented in Matlab and studied for varying applied stress or strain functions.

Closely related to the material characteristics is the tribological behavior. Based on general tribological systems, the kinematic and friction characteristic will be covered in the second section. Furthermore, types and mechanisms of friction will be discussed. Based on the Stribeck curve, the influence of the friction characteristic on the system dynamics will be studied, such as increasing or decreasing coefficients of friction as a function of the relative velocity. In the hands-on session, the equation of motion of a friction oscillator will be solved for different friction characteristics and the dynamic response analyzed.

The third section covers material removal and wear phenomena, which takes place e.g. in manufacturing processes or tribological systems with moving bodies relative to each other. In the theoretical part, wear mechanisms, types of wear, wear measured variables, and wear progression will be covered. The impact of wear and material removal on real applications will be studied and standardized tests to evaluate the wear resistance will be discussed. In the hands-on session, a system with wear will be modeled. Therefore, previously developed Matlab sub-routines of rheological models and the friction oscillator will be combined and complemented with wear models to analyze the material removal based on calculated local stresses.

Lecture line virtual factories

Module 2.1 - Building Virtual Factories

This module combines a theoretical with a lab-based approach. It contains theoretical input on different aspects of virtual factories. In several case studies the students learn how to apply virtual reality and augmented reality to factory planning and optimization,

The lecture starts with the basics of factory planning including production systems and assembly. Methods and tools used in the different phases of factory planning are introduced and used in a case study about layout planning by the students. In the lecture, an overview of basic Virtual Reality (VR) and Augmented Reality (AR) tools is given as well. In the hands-on lab session, the students build a virtual factory model which they can visualize and interact with in different virtual reality environments (CAVE, Powerwall, 3D Screen). In addition, the students will visualize parts of the model via AR tools (glasses, tablets, etc.). The background for the AR applications will be provided in the manufacturing lab at TU Kaiserslautern.

Furthermore, an introduction on "virtual optical measuring instruments" namely into the concept of ray tracing and the use of the optical design software Zemax is given in the lecture. The module gives an overview about the fundamentals of optical imaging and the propagation of rays by matrices. As a case study, the behavior of an optical instrument is virtually investigated, and the results are verified using an optical bench in the lab.

Module 2.2 - Features in Virtual Manufacturing

This module is aimed at providing students with fundamental knowledge and practical skills in data visualization and provides core competence in designing, realizing, utilizing, and evaluating visualization. The approach is hybrid: while fundamentals (“theory”) are taught in the style of a lecture, practical exercise sessions aim at connecting these theoretical insights with practical problems and to further illustrate the possibilities and limitations of existing visualization software tools.

The lecture begins with an overview of data visualization techniques and provides necessary context and terminology. The key goal of visualization is to transform data into images to draw on the power of the human visual system and thus enable insight about the problem underlying the visualization from the depiction. The key areas of visualization are discussed: scientific visualization, which aims at (typically) visualizing simulation output or empirical data with a physical context, information visualization, which considers more abstract data types such as graphs, networks, or time series, and visual analytics, which studies visualization systems and user interaction from a systems and process perspective to facilitate data exploration (i.e. hypothesis generation). Furthermore, the role of visualization in the scientific computing pipeline, where it relates to virtual manufacturing, is discussed. Here, the course focuses on feature-based visualization, a paradigm to structure the process of visualization and focus it on aspects of the data relevant to the underlying problem. This paradigm is well-suited to problems in virtual manufacturing and easy to apply for beginners and non-experts. The theoretical material of the lecture concludes with an overview of current research directions in visualization.

The practical part of the lecture is introduced with an overview of typical visualization software on both the end-user and intermediate levels. The visualization pipeline as a central metaphor underlying the function and interface of most visualization software is introduced. Subsequently, students work in interdisciplinary teams on their own computers to solve various visualization tasks using existing tools in a provided software environment, increasing in complexity from very specific (such as extracting a level) to more abstract (visualize features in structural mechanics data). During this, they are also introduced to advanced methods including hardware acceleration and parallelization. Finally, students are asked to program their own visualization pipelines for problems where existing software does not provide adequate solutions. The results of each exercise are briefly presented by a team and discussed in the course.

Module 3.1 - Cutting Technologies: Manufacturing and Measurement

This module contains a theoretical and experimental part as well. Theoretical input on cutting technologies, specifically on the chip formation process, forces, friction and process thermodynamics is provided. Several cutting technologies are covered. In addition, the students learn how to measure and assess the resulting workpieces geometries and surfaces. In several experiments, small groups of participants perform and evaluate machining processes.

The module starts with the basics of metal cutting including the chip formation process, cutting force calculations, tribology of the cutting process, different machining processes (turning, milling, and grinding), and basics of cutting machine tools. Optical and tactile methods and tools to characterize the processes and the work results are introduced and applied in practical experiments.

The objective of the entire course is to enable the students to plan and analyze machining processes. Therefore, in the lab-based part of the lecture line the students handle several measurement methods and instruments as well as software tools. Here, the focus lies on the influence of different cutting parameters on the work result. To advance both their theoretical and practical knowledge in manufacturing technology, the participants work together in interdisciplinary groups and present their results afterwards to the whole group.

Module 3.2 - Additive Manufacturing Technologies

This module introduces the IRTG members to additive manufacturing technologies and processes. As in most modules, theory and hands-on work in the lab are combined. First, the students are introduced to the basics of additive manufacturing including various additive manufacturing methods. The focus will be broad covering additive manufacturing for metal parts, polymers, and soft matter. The participants will learn about the possibilities as well as current limitations of additive manufacturing technologies.

In part 2 of the lecture, methods for the simulation of additive manufacturing processes are covered. This will include finite element, discrete element, and particle simulation methods. As this part is close to the research in several of the doctoral research projects, particular emphasis will be placed on current research results in the area.

The third part of this lecture will be experimental. Students design their own parts and will be able to directly print them in polymer materials. The experimental part also includes group work on machines which manufacture metal parts (a powder-bed machine at TU Kaiserslautern and a laser-deposition welding machine at UC Davis).