Josef Spachtholz

Dr. Josef Spachtholz

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Research Focus & Metrics

Academic Career Length

9Years (2018-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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15 July 2024 in Modelling
Verified
Journal Article
Open access
PDF file
DGDominik Goetz
Dominik Goetz
HPHannes Panzer
Hannes Panzer
DWDaniel Wolf
Daniel Wolf
FBFabian Bayerlein
Fabian Bayerlein
JSJosef Spachtholz
Josef Spachtholz
MZMichael Zaeh
Michael Zaeh
Due to the tool-less fabrication of parts and the high degree of geometric design freedom, additive manufacturing is experiencing increasing relevance for various industrial applications. In particular, the powder bed fusion of metals using a laser beam (PBF-LB/M) process allows for the metal-based manufacturing of complex parts with high mechanical properties. However, residual stresses form during PBF-LB/M due to high thermal gradients and a non-uniform cooling. These lead to a distortion of the parts, which reduces the dimensional accuracy and increases the amount of post-processing necessary to meet the defined requirements. To predict the resulting residual stress state and distortion prior to the actual PBF-LB/M process, this paper presents the finite-element-based simulation tool AscentAM with its core module and several sub-modules. The tool is based on open-source programs and utilizes a sequentially coupled thermo-mechanical simulation, in which the significant influences of the manufacturing process are considered by their physical relations. The simulation entirely emulates the PBF-LB/M process chain including the heat treatment. In addition, algorithms for the part pre-deformation and the export of a machine-specific file format were implemented. The simulation results were verified, and an experimental validation was performed for two benchmark geometries with regard to their distortion. The application of the optimization sub-module significantly minimized the form deviation from the nominal geometry. A high level of accuracy was observed for the prediction of the distortion at different manufacturing states. The process simulation provides an important contribution to the first-time-right manufacturing of parts fabricated by the PBF-LB/M process.


4 May 2018 in Materials at High Temperatures
Verified
Journal Article
Closed access
JSJosef Spachtholz
Josef Spachtholz
EAE. E. Affeldt
E. E. Affeldt
HMH. J. Maier
H. J. Maier
JHJ. Hammer
J. Hammer
The focus of this paper is the characterization of the influence of the temperature rates on the TMF lives. Therefore static and the dynamic calibrations of the temperature measurement devices were compared by a custom-built calibration specimen, which included five internal mantle thermocouples. Additionally the temperatures were measured on the specimens’ surface. The experimental setups used were compared by executing TMF pre-test with the identical single-crystalline specimen. Subsequently TMF tests on coated single-crystalline Nickel-based superalloy PWA 1484 were carried out with temperature rates of and . Finally the deviations of the determined TMF lives were evaluated.