Steffen Wackenrohr

Mr. Steffen Wackenrohr

Leibniz Universität Hannover, Institut für Werkstoffkunde
orcid

Research Focus & Metrics

Academic Career Length

7Years (2020-Present)

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

Representative Publications

View All Publications
30 March 2021 in Sensors
Verified
Journal Article
Open access
PDF file
LHLennart Hinz
Lennart Hinz
SMSebastian Metzner
Sebastian Metzner
PMPhilipp Müller
Philipp Müller
RSRobert Schulte
Robert Schulte
HBHans-Bernward Besserer
Hans-Bernward Besserer
EREduard Reithmeier
Eduard Reithmeier
Fringe projection profilometry in combination with other optical measuring technologies has established itself over the last decades as an essential complement to conventional, tactile measuring devices. The non-contact, holistic reconstruction of complex geometries within fractions of a second in conjunction with the lightweight and transportable sensor design open up many fields of application in production metrology. Furthermore, triangulation-based measuring principles feature good scalability, which has led to 3D scanners for various scale ranges. Innovative and modern production processes, such as sheet-bulk metal forming, thus, utilize fringe projection profilometry in many respects to monitor the process, quantify possible wear and improve production technology. Therefore, it is essential to identify the appropriate 3D scanner for each application and to properly evaluate the acquired data. Through precise knowledge of the measurement volume and the relative uncertainty with respect to the specimen and scanner position, adapted measurement strategies and integrated production concepts can be realized. Although there are extensive industrial standards and guidelines for the quantification of sensor performance, evaluation and tolerancing is mainly global and can, therefore, neither provide assistance in the correct, application-specific positioning and alignment of the sensor nor reflect the local characteristics within the measuring volume. Therefore, this article compares fringe projection systems across various scale ranges by positioning and scanning a calibrated sphere in a high resolution grid.

10 March 2021 in Advanced Engineering Materials
Verified
Journal Article
Open access
PDF file
CTChristof Johannes Jaime Torrent
Christof Johannes Jaime Torrent
SWSteffen Wackenrohr
Steffen Wackenrohr
JRJulia Richter
Julia Richter
CSCésar Sobrero
César Sobrero
SDSebastian Degener
Sebastian Degener
Thomas NiendorfThomas Niendorf
Thomas Niendorf
Additive manufacturing (AM) processes such as electron beam melting (EBM) are characterized by unprecedented design freedom. Topology optimization and design of the microstructure of metallic materials are enabled by rapid progress in this field. The latter is of highest importance as many applications demand appropriate mechanical as well as functional material properties. For instance, biodegradable implants have to meet mechanical properties of human bone and at the same time guarantee adequate cytocompatibility and degradation rate. In this field, pure iron has come into focus in recent studies due to its low toxicity. Hierarchical microstructures resulting from the EBM solidification processes and intrinsic heat treatment, respectively, allow for an adjustment of the degradation behavior and may promote enhanced fatigue strength. Herein, commercially pure iron (cp‐Fe) is processed by EBM. Microstructural analysis as well as an evaluation of the cyclic mechanical material properties are conducted. The results are compared to a hot‐rolled (HR) reference material. A contradiction observed as the EBM‐processed cp‐Fe (EBM Fe) shows lower ultimate tensile strength under monotonic loading but improved fatigue properties compared to the HR Fe. It is revealed that such a unique behavior originates from prevailing microstructural features in the EBM as‐built condition.

8 March 2022 in npj Materials Degradation
Verified
Journal Article
Open access
PDF file
SWSteffen Wackenrohr
Steffen Wackenrohr
CTChristof Johannes Jaime Torrent
Christof Johannes Jaime Torrent
SHSebastian Herbst
Sebastian Herbst
FNFlorian Nürnberger
Florian Nürnberger
Philipp KrooßPhilipp Krooß
Philipp Krooß
HMHans Maier
Hans Maier
Pure iron is very attractive as a biodegradable implant material due to its high biocompatibility. In combination with additive manufacturing, which facilitates great flexibility of the implant design, it is possible to selectively adjust the microstructure of the material in the process, thereby control the corrosion and fatigue behavior. In the present study, conventional hot-rolled (HR) pure iron is compared to pure iron manufactured by electron beam melting (EBM). The microstructure, the corrosion behavior and the fatigue properties were studied comprehensively. The investigated sample conditions showed significant differences in the microstructures that led to changes in corrosion and fatigue properties. The EBM iron showed significantly lower fatigue strength compared to the HR iron. These different fatigue responses were observed under purely mechanical loading as well as with superimposed corrosion influence and are summarized in a model that describes the underlying failure mechanisms.

5 July 2025 in International Journal of Fatigue
Verified
Journal Article
Open access
FOFelix Oppermann
Felix Oppermann
CHChristian Hinte
Christian Hinte
SWSteffen Wackenrohr
Steffen Wackenrohr
UKUlrich Krupp
Ulrich Krupp
HMHans Maier
Hans Maier
Christian HaaseChristian Haase
Christian Haase

8 May 2024 in npj Materials Degradation
Verified
Journal Article
Open access
PDF file
SWSteffen Wackenrohr
Steffen Wackenrohr
CTChristof Johannes Jaime Torrent
Christof Johannes Jaime Torrent
SHSebastian Herbst
Sebastian Herbst
FNFlorian Nürnberger
Florian Nürnberger
Philipp KrooßPhilipp Krooß
Philipp Krooß
HMHans Maier
Hans Maier
Due to its excellent biocompatibility, pure iron is a very promising implant material, but often features corrosion rates that are too low. Using additive manufacturing and modified powders the microstructure and, thus, the material properties, e.g., the corrosion properties, can be tailored for specific applications. Within the scope of this study, pure iron powder was modified with different amounts of CeO2 or Fe2O3 nanoparticles and subsequently processed by Electron Beam Powder Bed Fusion (PBF-EB/M). The corrosion-fatigue behavior of CeO2 and Fe2O3 modified iron was investigated using rotation bending tests under the influence of simulated body fluid (m-SBF). While the modification using Fe2O3 showed reduced fatigue and corrosion-fatigue strengths, it could be demonstrated that the modification with CeO2 is characterized by improved fatigue properties. The superior fatigue properties in air are attributed to the positive impact of dispersion strengthening. Additionally, an increased degradation rate compared to pure iron could be observed, eventually promoting an earlier failure of the specimens in the corrosion fatigue tests.

23 December 2024 in Journal of Engineering for Gas Turbines and Power
Verified
Journal Article
Closed access
PDF file
DRDirk Wilhelm Reker
Dirk Wilhelm Reker
RSRoman Sowa
Roman Sowa
CSCaspar Schwalbe
Caspar Schwalbe
FSFrank Seidel
Frank Seidel
KMKai Moehwald
Kai Moehwald
WTWolfgang Tillmann
Wolfgang Tillmann
The continuous improvement of high potential repair technologies is an essential driver for cost-effective and sustainable aviation. To withstand extreme forces and temperatures, the turbine section of aircraft engines is made from Nickel-based superalloys. This class of materials routinely develops cracks and geometrical deviations in service, which require a brazing repair, thus making brazing an indispensable key technology. This study seeks to improve brazing properties on Nickel-based superalloys for aircraft applications. Facilitated by materials simulation, a novel alloying strategy is outlined to design the braze alloy chemistry. The design criteria are established on the optimization of major microstructural properties influencing the mechanical properties known for repair brazed joints. The proposed design criteria were applied to the development of two new braze alloys. The new alloy design approach is validated experimentally by using the developed alloys. Mechanical properties of brazed samples made from Nickel-based superalloys were investigated at a service equivalent temperature of 871 °C. Results indicate that the ultimate tensile strength at 871 °C is 20.5% higher than that published for legacy braze alloys. This study provides a basis for the development of repair technologies applicable to further superalloys.