Page 54 - ILLS Annual Report 2018

MATERIALS SCIENCE
Heiner Meyer. German
Leibniz-Institute for Materials Engineering – IWT, Bremen Germany
‘I am a physicist working on ex situ and in situ analysis using diffraction techniques. I conduct work on the connection between internal material loading state and the resulting material modifications in processes with mechanical influence.’
Measuring internal material load during metal processing
Strain analyser for engineering applications SALSA
Knowledge about the interdependence between process parameters and the resulting material state in industrial application of the deep rolling process on, e.g. crankshafts, can allow targeted manufacturing and improvements in the service properties of components. In situ analyses of the material state during various processes can give valuable insight into the material behaviour due to mechanical, thermal or chemical material load on the workpiece. In the present project, we designed and performed in situ neutron diffraction experiments during
a mechanical surface finishing process
called deep rolling, to determine the internal material load for specific contact parameters.
AUTHORS
H. Meyer, J. Epp and H.-W. Zoch (Leibniz-Institute for Materials Engineering – IWT, Bremen Germany)
T. Pirling (ILL)
ARTICLE FROM
Mater. Perform. Charact. (2018)—doi: 10.1520/MPC20170132
REFERENCES
[1] B. Scholtesand and E. Macherauch, Z. Metallk. 77 (1986 ) 322 [2] E. Brinksmeier, F. Klocke, D.A. Lucca, J. Sölter and D. Meyer,
Procedia CIRP 13 (2014) 429
[3] M. Young, Appl. Opt. 10 (1971) 2763
The deep rolling process is used in industrial production as a finishing step in order to improve the fatigue properties of high-performance components via the introduction of compressive residual stresses, increased surface hardness and reduced roughness [1]. For practical applications however, it is important to understand both the process and how the mechanical load propagates in the sample, leading to a specific material end-state. Using measured internal material loads and residual stresses to solve the inverse problem for process effects is a concept of process signatures, which allow a process-independent approach to final material state depending on internal material load conditions [2].
In the present study, we investigated a deep rolling process using neutron diffraction in order to generate new knowledge about internal material load and resulting residual stress state. Measuring in situ poses several challenges to the experimental set-up, both
for the measurement and for running the process. To overcome several of these problems, we developed a new strain-imaging approach based on optical methods to determine 2D- and 3D-strain fields in the material under the tool (during the process) and along the plastically deformed path.
In our experiment we used a primary neutron beam defined only by a horizontal collimator, producing a vertical line of 0.6 mm in width (FWHM) and 25 mm
Figure 1
Photo and sketch of the experimental set-up with deep rolling tool and sample in the frame on the hexapod diffractometer table, optical cadmium slit in front of
the detector and resulting detector image from the full exposure of the sample under the contact point.
ANNUAL REPORT 2018