Research fields

Applications of optical methods to materials mechanics

• State of the art
  

  Optical methods yielding to displacement fiels are now really emerging in the mechanical sciences.
  Important progress in digital image computing allows the automatisation of data acquisition and processing.
  The numerical simulation by finite elements methods needs the knowledge of 3-D behaviour constitutive models of the materials. Thanks to their good sensitivity and high resolution the optical extensometric systems are then powerful tools to analyse multiaxial mechanical sollicitations.
  The "Laboratory de Mécanique et de Métrologie" brings together optics and mechanics scientists and so is able to apply optical methods in many researchs fields as mechanical characterization of materials or surface metrology.
  The very first method (1992) developed in the laboratory was based on the interpretation of photographic speckle images. The applications field extension has been done thanks to digital images grabbing and digital processing. The product is now a whole digital system allowing applications from macro to microscopy.

  The projects are dealing with image correlation and interferometric techniques applied to displacement measurements and stress and strain computing. Some extends to optical metrology are under study.

  Many fields of applications are realized in collaborations with industries (automotive, materials, ...)

   

• Staff
  
• Work in progress
  
  • The developments of the 2-D extensometric optical method by images correlation relies on the automatisation of the images acquisition process :
    • computer-control of the CCD camera shift with a microdisplacement stage allowing the tracking of the interest zone
    • synchronisation of the tensile apparatus with the acquisition of the images.

• Specific testing machines manufacturing

• Breadboarding of the PSDSPI set-up.

 

• Scientific collaborations
  

  The main research field involve the caracterization of the materials mechanical behaviours :

  • in collaboration with the CDM (Ecole des Mines de Paris), a study about the large strain behaviour of elastomers has been done. The main interest of the developed methodology lies on the identification of the constitutive laws parameters thanks to experimental results only. Interesting results as much for scientists or industrial partners have been got from shear and tensile tests on rectangular sheets of rubber.
  • an other study about localization of deformation has been done on concrete materials.
  • in shape modelling of filled polymers recent works have shown that using treated particulate fillers yields to enhance the strenght of the composite material. In this case the mesoscopic approach done at the LMM has shown the growth of the plastic zone around particules. This study is realised in collaboration with the L3MO (Ecole des Mines d'Alès).
  • some materials under static test show thermal dissipation areas. This effect can be demonstrate using infrared thermography. This phenomena have been correlated with strength heterogeneities measured using photomecanics experiments at the surface of the material. This study is realised in collaboration with the Laboratoire de Mécanique et de Génie Civil (USTL Montpellier).
  • PSDSPI ( Phase Shifting Digital Speckle Pattern Interferometry) in collaboration with University of Liege ,HOLOLAB(,Belgium).

   

• Scientific publications
  

LUD 20/02/01