Tobias Ehlers

Mr. Tobias Ehlers

orcid

Research Focus & Metrics

Academic Career Length

8Years (2019-Present)

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

Representative Publications

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25 July 2023 in Heliyon
Verified
Journal Article
Open access
IMIna Meyer
Ina Meyer
MOMarcus Oel
Marcus Oel
TETobias Ehlers
Tobias Ehlers
RLRoland Lachmayer
Roland Lachmayer
Additive manufacturing (AM) can be used to produce multi-material parts in which the material can be varied voxel-wise in all three spatial directions. This means that the paradigm of the homogeneous material can be abandoned and local effects such as heat conduction or damping can be selectively adjusted in the part. Recently, continuous development of machine technology has allowed the production of multi-metal materials in laser powder bed fusion (PBF-LB/MM). Compared to other additive manufacturing processes for multi-material production, this allows greater design freedom and detail accuracy to be realized. However, due to the novel character of multi-material manufacturing in PBF-LB, the process knowledge for successful and reproducible fabrication is currently lacking. This paper focuses on establishing design guidelines for manufacturing the material pairing of stainless steel 316L (1.4404) and copper alloy CuCrZr (CW106C). The article is accompanied by the development of a specific process chain. As a result of this work, design guidelines for multi-material parts are available for the first time, in regard to arrangement, size, overhangs, economy, powder quality and laser scanning.

21 February 2022 in Applied Sciences
Verified
Journal Article
Open access
PDF file
TETobias Ehlers
Tobias Ehlers
RLRoland Lachmayer
Roland Lachmayer
Additively manufactured particle dampers can significantly improve component damping. However, if designed incorrectly, the damping can be worsened. For the design of additively manufactured particle dampers, there are not yet sufficient design rules and models to describe the effect due to numerous design parameters. The research question answered in this paper describes how the effect of particle damping can be characterised as a function of excitation force and excitation frequency for different cavity sizes. To characterise the effect of particle damping, a 33 full factorial test plan is constructed, and the damping is determined experimentally. It is shown that the damping can be reliably evaluated with the circle-fit method. The effect of particle damping is investigated for beams made of AlSi10Mg, 1.2709 and Ti6Al4V. As a result, a positive effect of the particle damping in a frequency range from 500 to 30,000 Hz and partly up to the 9th bending mode can be proven. It is shown that, for the first bending mode, there is an optimum at approx. 2000 Hz. For the optimum, the increase of the damping for the tool steel 1.2709 to 28 and for the aluminium alloy AlSi10Mg to 18 can be proven.

Verified
Journal Article
Open access
PDF file
RLRoland Lachmayer
Roland Lachmayer
Bernd-Arno BehrensBernd-Arno Behrens
Bernd-Arno Behrens
TETobias Ehlers
Tobias Ehlers
PMPhilipp Müller
Philipp Müller
PAPhilipp Althaus
Philipp Althaus
SHSven Hübner
Sven Hübner
The deep-drawability of a sheet metal blank is strongly influenced by the tribological conditions prevailing in a deep-drawing process. Therefore, new methods to influence the tribology represent an important research topic. In this work, the application of a process-integrated lubrication in a deep-drawing process is investigated. Most promising geometries of the lubrication channels and outlet openings are first identified by means of numerical simulation at the example of a demonstrator process. Cylindrical test specimens with the specified channel geometries are additively manufactured and installed in a strip drawing test stand. Additive manufacturing enables the possibility of manufacturing complex channel geometries which cannot be manufactured by conventional methods. A hydraulic metering device for conveying lubricant is connected to the cylindrical test specimens. Thus, hydraulically lubricated strip drawing tests are performed. The tests are evaluated according to the force curves and the fluid mechanical buildup of pressure cushion. The performance of process-integrated lubrication is thus analyzed and evaluated. By means of a coupled forming and SPH simulation, the lubrication channels could be optimally designed. From the practical tests, it could be achieved that the drawing force decreases up to 27% with pressure cushion build up. In this research, a hydraulic lubrication in the area of highest contact normal stresses is the most optimal process parameter regarding friction reduction.

13 November 2022
Verified
Book Chapter
Closed access
PDF file
TETobias Ehlers
Tobias Ehlers
IMIna Meyer
Ina Meyer
MOMarcus Oel
Marcus Oel
BBBehrend Bode
Behrend Bode
PGPaul Christoph Gembarski
Paul Christoph Gembarski
RLRoland Lachmayer
Roland Lachmayer

26 June 2020
Verified
Book Chapter
Closed access
PDF file
TETobias Ehlers
Tobias Ehlers
JWJohanna Wurst
Johanna Wurst
RLRoland Lachmayer
Roland Lachmayer

26 August 2020
Verified
Book Chapter
Closed access
PDF file
TETobias Ehlers
Tobias Ehlers
RLR. Lachmayer
R. Lachmayer
SVS. Vajna
S. Vajna
Thorsten HalleThorsten Halle
Thorsten Halle