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Aufsatz
A framework for the computer-aided planning and optimisation of manufacturing processes for components with functional graded properties
(2015-02-17)
In this contribution a framework for the computer-aided planning and optimisation of functional graded components is presented. The framework is divided into three modules - the "Component Description", the "Expert System" for the synthetisation of several process chains and the "Modelling and Process Chain Optimisation". The Component Description module enhances a standard computer-aided design (CAD) model by a voxel-based representation of the graded properties. The Expert System synthesises process steps stored ...
Dissertation
Simulationen und Experimente im Schwellenwertbereich zur Aufklärung der Risswachstumsmechanismen in einer Aluminiumlegierung
(2020)
Lange Risse, die bei Belastungen nahe des Schwellenwerts wachsen, können Ausbreitungscharakteristika zeigen, welche denen kurzer Stadium I-Risse ähneln. Neben einer lokalen Blockade der Rissfront durch Teilchen einer zweiten Phase ist ein schubspannungsgesteuerter Rissfortschritt ein interessanter Effekt, der bei diesen Belastungsbedingungen auftritt. Das berichtete Verhalten wird im Rahmen dieser Arbeit auf das Rissspitzenfeld zurückgeführt. Zu diesem Zweck wurden Risswachstumsexperimente mit angerissenen Flachproben ...
Aufsatz
Quenching of High Entropy Alloys after Annealing
(2020)
The effect of cooling rate after annealing at 900 °C on the microstructure and hardness of high entropy alloys was investigated using two typical samples with the chemical composition of Co₁₆Cr₁₄.₅Fe₂₉Mn₁₁.₅Ni₂₉ and Co₁₁.₅Cr₇Fe₂₇Mn₂₇Ni₂₇(Nb₀.₀₈C₀.₅) (at%). The microstructural characterisation and hardness measurements were carried out by optical microscopy, scanning electron microscopy, wavelength-dispersive X-ray spectroscopy, electron back scattered diffraction, X-ray diffraction technique and Vickers hardness ...
Aufsatz
Comparative investigation of two-dimensional imaging methods and X-ray tomography in the characterization of microstructure
(2017-10-02)
The microstructural features of three different materials have been quantified by means of 2D image analysis and X-ray micro-computer tomography (CT) and the results were compared to determine the reliability of the 2D analysis in the material characterization. The 3D quantification of shrinkage pores and Fe-rich inclusions of an Al-Si-Cu alloy by X-ray tomography was compared with the statistical analysis of the 2D metallographic pictures and a significant difference in the results was found due to the complex ...
Aufsatz
Effect of Grain Statistics on Micromechanical Modeling: The Example of Additively Manufactured Materials Examined by Electron Backscatter Diffraction
(2020-02-21)
Micromechanical modeling is one of the prominent numerical tools for the prediction of mechanical properties and the understanding of deformation mechanisms of metals. As input parameters, it uses data obtained from microstructure characterization techniques, among which the electron backscatter diffraction (EBSD) technique allows us to understand the nature of microstructural features, that are usually described by statistics. Because of these advantages, the EBSD dataset is widely used for synthetic microstructure ...
Aufsatz
Effect of Friction Stir Processing on Microstructural, Mechanical, and Corrosion Properties of Al-Si12 Additive Manufactured Components
(2020-01-03)
Additive manufacturing (AM) is an advanced manufacturing process that provides the opportunity to build geometrically complex and highly individualized lightweight structures. Despite its many advantages, additively manufactured components suffer from poor surface quality. To
locally improve the surface quality and homogenize the microstructure, friction stir processing (FSP) technique was applied on Al-Si12 components produced by selective laser melting (SLM) using two different working media. The effect of FSP on ...
Aufsatz
Influence of complex geometries on the properties of laser-hardened surfaces
(2020-04-25)
Laser surface hardening provides for many advantages in terms of flexible production due to very localized and controlled energy input into the material. Laser processing offers the possibility to treat surfaces in order to locally strengthen the areas that are prone to fatigue cracking. It is well known that laser energy absorption depends on many parameters, e.g., the surface structure and the surface orientation. The incident angle of the laser beam plays a key role in this regard. When complex geometries like ...
Aufsatz
Effect of Post-Process Machining on Surface Properties of Additively Manufactured H13 Tool Steel
(2018-08-28)
Der Werkzeugstahl AISI H13 zeichnet sich durch einen hohen Verschleißwiderstand und eine gute Temperaturwechselbeständigkeit aus. Hauptanwendungsbereiche des H13 sind Druckguss- und Schmiedewerkzeuge. Die Verarbeitung von H13 durch additive Fertigungsverfahren, wie z. B. dem selektiven Laserschmelzen (selective laser melting, SLM), eröffnet neue Gestaltungsmöglichkeiten, wie z. B. die Integration interner Kühlkanäle, die es erlauben, das Einsatzverhalten der Werkzeuge zu verbessern. Aufgrund hoher Oberflächenrauheiten ...
Aufsatz
A Screening Approach for Rapid Qualitative Evaluation of Residual-Stress States – Application to Laser-Hardened Microalloyed Steel
(2019-06-11)
Surface hardening and compressive residual stresses are keys to superior part performance in numerous applications. In this context the development of advanced laser surface treatments for new materials and complex sample shapes is a time con-suming process. Eventually, determination of residual stress states by means of X-ray diffraction in the whole surface and subsurface region, respectively, is one of the main time consuming facors in terms of characterization. In many applications the provision of an adequate ...