The process used to produce components influences the microstructure of almost all materials – and thus has an impact on mechanical properties. Process conditions and material parameters affect the phase transitions and growth morphology of microstructures. The characteristic composition of resulting microstructures has a crucial influence on the quality of a material. Pace3D is a software package developed at the Steinbeis Transfer Center for Material Simulation and Process Optimization, which is based at Karlsruhe University of Applied Sciences. The software is a reflection of current material technology trends: It provides the means not only to save time and resources in the development of materials, but also to systematically investigate correlations between different compositions and properties, to predict durability, and to run checks on components.
Modern simulation processes, such as the technique used by Pace3D, make it possible not only to gain insights – in situ – into the final composition of a material, but also to examine the structure-forming process in 3D. It is frequently possible to change the quality of materials and processes by making small adjustments in the processing technique or by varying the composition. Pace3D simulates material microstructures, making it possible to determine in detail how materials react to external influences such as heat, magnetic fields, mechanical strain, or fluid-mechanical influences. In many production processes, the polycrystalline structure of grains and the distribution of grains of different sizes is pivotal to the hardness and breaking strength of a material. In use, materials are often subject to thermo-mechanical strain which systematically changes the structure and eventually wears down the component part. By delicately managing the process, the composition of the structure and subsequent changes in the microstructure can be carefully influenced and this software can be used to design a material and arrive at specific properties. Instead of experimenting and using metallographic and mechanical characterization, which typically damages the sample, calculations can be used. The material, the component and the future process can be planned on the computer using material simulation processes – thus conserving resources and saving energy. This reduces expensive testing and weak points can be avoided during the design stage on the computer. Pace3D supports this modern material development process and by focusing on the simulation of the composition of microstructures, it has become a core component of integrated computational materials engineering (ICME), an internationally recognized technology of the future. ICME is a new, shooting-star field of materials research. The vision is of a holistic system, centering on computationbased product and materials development and integrating scale-independent simulation methods of materials science.
These new microstructure simulation solutions, provided by Pace3D, analyze the impact of extreme strain on material properties. Computations make it possible to examine factors such as grain coarsening as a result of heat treatment (Fig. 1) or the formation of fissures under continuous or cyclical stress caused by external influences. The simulation in Fig. 2 shows a material sample under permanent tensile stress along the vertical axis. A fissure forms, usually along the grain boundaries. Another example of examining mechanical strain in applications involves material failure and analyzing strength or hardness. This involves experimenting with different nominal loadings and stress durations. In the microstructure simulations shown in Fig. 3, the actual timing of material failure can be ascertained with concentrated particle distributions under cyclical stress. The results can be plotted as a typical Wohler curve and predictions can be made about the structural strength of different microstructure samples. By planning precise processes, the formation of microstructures can be carefully controlled and software can be used to develop materials with specific properties.
Pace3D is a comprehensive software package for large-scale parallel 3D simulation on supercomputers. It offers an integrated data analysis module and high-quality images of the microstructure formation processes in metal alloys and other materials such as ceramics, polymers, and biological or geological systems. The package also includes tools for calculating phase transition processes in heterogeneous multiphase material systems, taking into consideration factors such as anisotropic properties, mass and heat diffusion, convection, elasticity, and plasticity. As well as providing a solver for determining thermo- and chemo-mechanical stress distribution, the software has modules for calculating multiphase flows based on Navier-Stokes equations or Lattice Boltzmann methods (LBMs). The flow solver makes it possible to simulate combined flow and heat transfer in porous materials, simultaneously taking phase transitions into account. Alternatively, flowing phase mixtures consisting of several liquid and solid phases can be calculated. In actual applications, it is possible to examine liquid propagation in channel structures and wetting behavior on topological or chemically structured surfaces. The computations allow to derive conclusions on reductions in susceptibility to corrosion. If fine-tuned to the specific requirements of the process being observed, different modules can be combined and used to describe different phase conditions, particle systems, and flow processes. Also, mechanical loads and tensile stress can be remedied.
Pace3D is programmed using C/C++ under Linux. Simulations can be conducted sequentially or in parallel on supercomputers using an MPI library. The software is broken down into modules to make it possible to adapt the configuration of simulation calculations to the special re quirements of material systems and processes. It is also possible to combine individual modules for specific applications such as multiphase materials, diffusion, mechanics, and flows.
Prof. Dr. Britta Nestler and Michael Selzer are joint-directors of the Steinbeis Transfer Center for Material Simulation and Process Optimization at Karlsruhe University of Applied Sciences. The center’s portfolio of services ranges from the development of models and software solutions, to the running of simulation studies for analyzing materials and processes, and for predicting external influences on changes in microstructures with the aim of optimizing process design and virtual reality-based material design.
Michael Selzer | Prof. Dr. Britta Nestler
Steinbeis Transfer Center Material Simulation and Process Optimization (Karlsruhe)
su1272@stw.de