PSI - Issue 75

Arthur THIBAULT et al. / Procedia Structural Integrity 75 (2025) 509–518 Arthur THIBAULT / Structural Integrity Procedia (2025)

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Fig. 3. Samples taking: butt welded scooter’s deck (a), electric discharge machining (b), samples dimensions (c)

Prior to performing the micro-tensile tests, specimens were polished on both sides in order to eliminate geometric discontinuities due to the weld bead. Once polishing was completed, chemical etching was performed, followed by micrograph acquisition, in order to locate the weld bead within the gauge section of the specimens. Additionally, indentations were made on either side of the gauge section to identify the study area and to enable the plotting of the deformation fields on the microstructure later (Fig. 4). Finally, a speckle pattern was applied to the central part of the gauge section.

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Fig. 4. Central area of the sample before (a) and after speckle (b)

These tests were instrumented using Stereo Digital Image Correlation (Stereo DIC). With this method, two cameras are used and mounted on a Leaica stereo microscope. The test specimen is then placed in a microtensile machine, which is itself placed under the microscope. This instrumentation method consists of three phases. (i), the optical system is calibrated by capturing images of a calibration target at various positions within the field of view, in order to establish the link between the 3D spatial coordinates and those viewed by each camera. (ii), images are acquired during the test with the specimen placed in the calibrated volume (Fig. 5). (iii), the images taken during the test are reconstructed in 3D using stereo correlation and the previously determined calibration constants. The method used for these tests is precisely described by Caron et al. (2023).

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1) Stereo microscope 3) cameras 4) Micro-tensile machine 5) Sample 6) Controler 7) Image during test

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Fig. 5. Experimental setup with the micro tensile machine placed under the microscope equipped with 2 cameras and images taking during test