Thomas Niendorf

Bio: Thomas Niendorf is an academic researcher from University of Kassel. The author has contributed to research in topics: Microstructure & Materials science. The author has an hindex of 39, co-authored 249 publications receiving 5861 citations. Previous affiliations of Thomas Niendorf include University of Erlangen-Nuremberg & Freiberg University of Mining and Technology.

Highly Anisotropic Steel Processed by Selective Laser Melting

Abstract: For additive manufacturing of metals, selective laser melting can be employed. The microstructure evolution is directly influenced by processing parameters. Employing a high energy laser system, samples made from austenitic stainless steel were manufactured. The microstructure obtained is characterized by an extremely high degree of anisotropy featuring coarse elongated grains and a 〈001〉 texture alongside the build direction during processing. Eventually, the anisotropy of the microstructure drastically affects the monotonic properties of the current material.

On the fatigue properties of metals manufactured by selective laser melting — The role of ductility

Abstract: The selective-laser-melting (SLM) technique is an outstanding new production technology that allows for time-efficient fabrication of highly complex components from various metals. SLM processing leads to the evolution of numerous microstructural features strongly affecting the mechanical properties. For enabling application in envisaged fields the development of a robust production process for components subjected to different loadings is crucially needed. With regard to the behavior of SLM components subjected to cyclic loadings, the damage evolution can be significantly different depending on the raw material that is used, which is, in this case, highly ductile austenitic stainless steel 316L and high-strength titanium alloy TiAl6V4. By means of a thorough set of experiments, including postprocessing, mechanical testing focusing on high-cycle fatigue and microstructure analyses, it could be shown that the behavior of TiAl6V4 under cyclic loading is dominated by the process-induced pores. The fatigue behavior of 316L, in contrast, is strongly affected by its monotonic strength.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Additive manufacturing (3D printing): A review of materials, methods, applications and challenges

Abstract: Freedom of design, mass customisation, waste minimisation and the ability to manufacture complex structures, as well as fast prototyping, are the main benefits of additive manufacturing (AM) or 3D printing. A comprehensive review of the main 3D printing methods, materials and their development in trending applications was carried out. In particular, the revolutionary applications of AM in biomedical, aerospace, buildings and protective structures were discussed. The current state of materials development, including metal alloys, polymer composites, ceramics and concrete, was presented. In addition, this paper discussed the main processing challenges with void formation, anisotropic behaviour, the limitation of computer design and layer-by-layer appearance. Overall, this paper gives an overview of 3D printing, including a survey on its benefits and drawbacks as a benchmark for future research and development.