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Article

Evaluation of Strain Transition Properties between Cast-In Fibre Bragg Gratings and Cast Aluminium during Uniaxial Straining

1
Chair of Metal Forming and Casting, Technical University of Munich (TUM), 85748 Garching, Germany
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Research Neutron Source Heinz Maier-Leibnitz, TUM, 85748 Garching, Germany
3
Application Center for CT in Metrology, Fraunhofer Institute for Integrated Circuits, IIS, 94469 Deggendorf, Germany
4
Department of Mechanical Engineering and Mechatronics, Deggendorf Institute of Technology, 94469 Deggendorf, Germany
*
Author to whom correspondence should be addressed.
Sensors 2020, 20(21), 6276; https://doi.org/10.3390/s20216276
Received: 30 September 2020 / Revised: 24 October 2020 / Accepted: 29 October 2020 / Published: 4 November 2020
(This article belongs to the Special Issue Fiber Bragg Grating Based Sensors and Systems)
Current testing methods are capable of measuring strain near the surface on structural parts, for example by using strain gauges. However, stress peaks often occur within the material and can only be approximated. An alternative strain measurement incorporates fibre-optical strain sensors (Fiber Bragg Gratings, FBG) which are able to determine strains within the material. The principle has already been verified by using embedded FBGs in tensile specimens. The transition area between fibre and aluminium, however, is not yet properly investigated. Therefore, strains in tensile specimens containing FBGs were measured by neutron diffraction in gauge volumes of two different sizes around the Bragg grating. As a result, it is possible to identify and decouple elastic and plastic strains affecting the FBGs and to transfer the findings into a fully descriptive FE-model of the strain transition area.We thus accomplished closing the gap between the external load and internal straining obtained from cast-in FBG and generating valuable information about the mechanisms within the strain transition area.It was found that the porosity within the casting has a significant impact on the stiffness of the tensile specimen, the generation of excess microscopic tensions and thus the formation of permanent plastic strains, which are well recognized by the FBG. The knowledge that FBG as internal strain sensors function just as well as common external strain sensors will now allow for the application of FBG in actual structural parts and measurements under real load conditions. In the future, applications for long-term monitoring of cast parts will also be enabled and are currently under development. View Full-Text
Keywords: Fibre Bragg Gratings; neutron diffraction; X-ray tomography; tensile test Fibre Bragg Gratings; neutron diffraction; X-ray tomography; tensile test
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MDPI and ACS Style

Heilmeier, F.; Koos, R.; Singer, M.; Bauer, C.; Hornberger, P.; Hiller, J.; Volk, W. Evaluation of Strain Transition Properties between Cast-In Fibre Bragg Gratings and Cast Aluminium during Uniaxial Straining. Sensors 2020, 20, 6276. https://doi.org/10.3390/s20216276

AMA Style

Heilmeier F, Koos R, Singer M, Bauer C, Hornberger P, Hiller J, Volk W. Evaluation of Strain Transition Properties between Cast-In Fibre Bragg Gratings and Cast Aluminium during Uniaxial Straining. Sensors. 2020; 20(21):6276. https://doi.org/10.3390/s20216276

Chicago/Turabian Style

Heilmeier, Florian, Robert Koos, Michael Singer, Constantin Bauer, Peter Hornberger, Jochen Hiller, and Wolfram Volk. 2020. "Evaluation of Strain Transition Properties between Cast-In Fibre Bragg Gratings and Cast Aluminium during Uniaxial Straining" Sensors 20, no. 21: 6276. https://doi.org/10.3390/s20216276

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