Strain Measurement in Aluminium Alloy during the Solidification Process Using Embedded Fibre Bragg Gratings

Weraneck, Klaus; Heilmeier, Florian; Lindner, Markus; Graf, M.; Jakobi, Martin; Volk, Wolfram; Roths, Johannes; Koch, Alexander W.

doi:10.3390/s16111853

Cited by 17 publications

(5 citation statements)

References 29 publications

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“…Thus, a strain sensitive area is given along the fibre's axis, which is measured by an optical interrogator. For the internal strain measurements during tensile testing we used a 3 mm long femtosecond grating within an SMF28 glass fibre, which can be cast into aluminium alloys [2]. According to the findings of Heilmeier et al, the fibre has a force-locked connection to the surrounding casting [10].…”

Section: Fibre Bragg Gratingsmentioning

confidence: 99%

“…The use of advanced internal measurement methods now provides a means to obtain valid strain information in structural parts under operating conditions and is therefore a promising approach to address this problem. Fibre-optical strain sensors (Fibre Bragg Gratings, FBGs) are strain sensors which can be cast into aluminium parts, as already shown by Weraneck et al [2]. At the current state of development, structural parts are commonly monitored by the use of FBGs.…”

Section: Introductionmentioning

confidence: 99%

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

Heilmeier

Koos

Singer

et al. 2020

Sensors

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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.

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Section: Fibre Bragg Gratingsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Heilmeier

Koos

Singer

et al. 2020

Sensors

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“…In this study, we investigated optical FBG-based sensors that have been embedded in aluminum parts during the cast process without any additional metal layers. The first report on embedding FBGs during casting was given by some of the authors [ 54 ], were the strain development during the solidification process was studied. Heilmeier et al [ 55 ] demonstrated strain measurements with embedded FBGs in aluminum parts in the plastic deformation regime.…”

Section: Introductionmentioning

confidence: 99%

Fiber Bragg Sensors Embedded in Cast Aluminum Parts: Axial Strain and Temperature Response

Lindner

Stadler

Hamann

et al. 2021

Sensors

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In this study, the response of fiber Bragg gratings (FBGs) embedded in cast aluminum parts under thermal and mechanical load were investigated. Several types of FBGs in different types of fibers were used in order to verify general applicability. To monitor a temperature-induced strain, an embedded regenerated FBG (RFBG) in a cast part was placed in a climatic chamber and heated up to 120∘C within several cycles. The results show good agreement with a theoretical model, which consists of a shrink-fit model and temperature-dependent material parameters. Several cast parts with different types of FBGs were machined into tensile test specimens and tensile tests were executed. For the tensile tests, a cyclic procedure was chosen, which allowed us to distinguish between the elastic and plastic deformation of the specimen. An analytical model, which described the elastic part of the tensile test, was introduced and showed good agreement with the measurements. Embedded FBGs - integrated during the casting process - showed under all mechanical and thermal load conditions no hysteresis, a reproducible sensor response, and a high reliable operation, which is very important to create metallic smart structures and packaged fiber optic sensors for harsh environments.

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“…24,25 Embedded FBGs were used to monitor strain in aluminium alloys during production. 26 Multi-point strain measurement in an NbTi superconducting sample coil was carried out using FBG sensors at low temperature and in a high background magnetic field. 27 FBG sensors were used to measure strain and temperature induced during micro-turning operations.…”

Section: Introductionmentioning

confidence: 99%

Measurement of forces on multi-point forming tools using fibre Bragg grating sensors

Elghawail

Pham

Huang

et al. 2019

Proceedings of the Institution of Mechanical Engineers, Part B:

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Multi-point forming uses forces applied to a tool, comprising of multiple pins set at different heights, to form sheet metal for panelling in white goods, automotive bodywork, aircraft frames and so on. The use of multiple pins allows for rapid change over and flexibility in the tool making it suitable for small-batch and prototype component manufacture. To explore the relationship between ‘springback’ of the sheet metal on release from the tool, and the applied pin force, it is first necessary to understand and measure the forming forces. This article presents a novel method of measuring forming forces on individual pins in a multi-point forming tool using fibre Bragg grating sensors, monitoring the elastic strain on the selected pins during the forming process. The operating principles behind forming force measurements using fibre Bragg gratings are introduced and a relationship is developed between springback in the formed part after the final unloading and the forming force as measured on selected individual pins under different compression ratios (30%, 40%, 50% and 60%) of the elastic cushion between the tips of the pins and the workpiece. Experiments were performed to validate the proposed measuring method, and results indicate that forming forces detected by the proposed method correlated well with the results obtained by numerical simulation. This suggests the proposed method has good potential for real-time measurement and monitoring of forming force distribution in multi-point forming tools during the forming process.

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Strain Measurement in Aluminium Alloy during the Solidification Process Using Embedded Fibre Bragg Gratings

Cited by 17 publications

References 29 publications

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

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

Fiber Bragg Sensors Embedded in Cast Aluminum Parts: Axial Strain and Temperature Response

Measurement of forces on multi-point forming tools using fibre Bragg grating sensors

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