Hybrid Stereocorrelation Using Infrared and Visible Light Cameras

Charbal, Ali; Dufour, John-Eric; Hild, François; Poncelet, Martin; Vincent, L.; Roux, Stéphane

doi:10.1007/s11340-016-0127-4

Cited by 19 publications

(21 citation statements)

References 36 publications

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“…With the predictions of finite element analyses, it is deduced that the largest strain variations during cyclic loading are in the out-of-plane direction resulting in several micrometer out-of-plane displacements [6]. The 3D displacement fields are then measured by a hybrid multiview system composed of two visible light cameras and the infrared camera that also gives access to the Lagrangian temperature fields [7,8]. Last, the equivalent Tresca strain variation obtained from finite element analyses is extracted in the region of crack initiation.…”

Section: Introductionmentioning

confidence: 99%

High cycle thermal fatigue of austenitic stainless steel

et al. 2018

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Abstract.A new experimental setup called FLASH (THErmal Fatigue by LASer or Helium pulses) has been developed to perform thermal fatigue tests on materials used in structures of Sodium-cooled Fast Reactors (SFRs). A set of thermal loadings ranging from 150°C to 200°C prescribed by a high energy laser has been applied to A316L(N) stainless steel samples. Thermal fatigue tests are performed until a macrocrack is formed. The 3D displacement fields of the surface impacted by the laser beam are measured by a hybrid multiview system. A thermomechanical model is used to compute displacement fields that are compared with correlation measurements. These results are compared in terms of strain levels to the fatigue curve determined from standardized isothermal uniaxial mechanical fatigue tests.

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Section: Introductionmentioning

confidence: 99%

High cycle thermal fatigue of austenitic stainless steel

et al. 2018

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“…The ultrahigh speed experiment [66], and then used for the calibration of the stereovision system of the first configuration of the FLASH facility [67]. The size of both plates that constitute the open-book target was 30 x 30 x 14 mm 3 , and the opening angle between these two plates was 132°.…”

Section: Resultsmentioning

confidence: 99%

Crack initiation and propagation under thermal fatigue of austenitic stainless steel

Wang

Charbal

Hild

et al. 2019

International Journal of Fatigue

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Thermal fatigue tests on AISI 316L(N) austenitic stainless steel samples are performed through pulsed laser on specimen that can be subjected to an additional static mechanical load. These tests are carried out in Helium environment with a dedicated and heavily instrumented setup , FLASH. The fatigued surface is monitored by a hybrid multiview system composed of two visible light and one infrared cameras that, through 3D-registration, provides in-situ access to the 3D surface displacement fields and 2D temperature fields. At a fatigue frequency of 1 Hz, the surface temperature range covered per cycle can be varied from 150°C to 250°C, conditions that allow surface damage to be reproduced. The multiview system reveals the time-resolved mechanisms of surface damage, from significant cyclic plasticity with persistent slip bands to micro-crack initiation and growth, leading to their quantitative characterization (micro-crack density, length of major crack, orientation) all along the test. These observations are confirmed at a few check points where the test is interrupted for optical microscopy inspection of the surface. Finally, the thermal fatigue data are compared to purely mechanical isothermal uniaxial fatigue data through the use of an equivalent strain, and an excellent (and conservative) agreement is obtained.

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“…Both cameras are synchronized and triggered with the laser signal. () These acquisitions can be combined for so‐called hybrid stereocorrelation . However, in the following, only data sets from 1 camera will be discussed for the 2 considered test cases.…”

Section: Experimental Cases: Laser Shock Assessmentmentioning

confidence: 99%

Spatiotemporal regularization for digital image correlation: Application to infrared camera frames

Charbal

Roux

Hild

et al. 2018

Numerical Meth Engineering

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The spatiotemporal response of a stainless steel plate undergoing cyclic laser shock is recorded with an infrared camera, and Digital Image Correlation (DIC) is used to analyze both displacement and temperature fields. Two very challenging difficulties are addressed: i) large gray level variations (due to temperature changes) and ii) convection effects affecting images. To this aim, a spatiotemporal regularization is designed exploiting a numerical model of the test. The thermomechanical space-time predictions are first processed through Karhunen-Loève decomposition to extract dominant temporal and spatial modes. The temporal modes are then inserted in a spatiotemporal DIC framework to estimate the experimental spatial modes that account for both gray level variations (and hence temperature) and displacement fields. It is shown that with only three modes, the full thermomechanical response of the material is captured. The temporal regularization issued from the model also allows the spurious effect of convection to be filtered out. Because of the drastic decrease in the number of degrees of freedom due to data reduction, the number of analyzed frames can be reduced from 50 down to 6 to capture the thermomechanical response, thereby leading to an enhanced efficiency.

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Hybrid Stereocorrelation Using Infrared and Visible Light Cameras

Cited by 19 publications

References 36 publications

High cycle thermal fatigue of austenitic stainless steel

High cycle thermal fatigue of austenitic stainless steel

Crack initiation and propagation under thermal fatigue of austenitic stainless steel

Spatiotemporal regularization for digital image correlation: Application to infrared camera frames

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