Full-field measurement techniques and local mechanical properties identification

Full-field measurement techniques and local mechanical properties identification


Imaging technology and numerical techniques allow us for tracking the deformation fields of a heterogeneous material under mechanical loading based on its stage-by-stage images. In contrast to a classical measurement of displacement, full-field measurement based on image correlation technology provides a greater insight into detailed, local material properties (in a certain observation area or volume, utilizing selected inverse techniques) as well as failure mechanism. This measurement enables one to build a more accurate material model that possesses an excellent predictive capability. COHMAS Laboratory focuses on the development of robust identification techniques that can efficiently process 3-D full-field data. Here, tools necessary for image correlation are designed for complex microstructures. 

Full-field deformation measurements and mechanical properties identification of biological tissue
Optical methods (such as digital image correlation) for 3D shape, displacement and deformation measurements of materials and structures under various loadings allow for the visualization of surface profile change and quantification of surface deformation evolution, which significantly advance our knowledge of material properties and their failure mechanism. We are currently developing field-portable and cost-effective tools for full-field deformation measurements of composites, complex microstructures and biological tissues. Recently, researches have been devoted to characterize mechanical properties in primary cell wall of plant organs, such as in stems/hypocotyl, petioles, cuticles, shoot apical meristem. However, in-vivo studies in root systems have not been found, therefore it is of the utmost importance to establish an attractive platform to allow these studies. We expect to establish a technique that can perform quick assessments (elastic and viscoelastic properties) of how a plant is going to respond to rapid changes in the environment. Using a surrogate model with our proposed system, we aim to acquire the gradient mapping of stiffness along the root, which can be correlated with turgor pressure.

This research is part of collaboration with Prof. Ikram Blilou of Plant Cell and Developmental Biology (PCDB) Laboratory. 
Identification of local mechanical properties of heterogeneous materials
We have developed a novel identification method for estimating material properties using full-field measurement where a large volume of 3D data can be processed. Correlation of material images obtained during in-situ mechanical testing within X-ray micro-computed tomograph has been established. An example of 3D identification technique with reference Young’s modulus distribution (Fig. a) and estimated Young’s modulus distribution (Fig. b) is shown below.

An evolution of full-field vertical strains in 2D woven composite

An evolution of u-displacement fields (unit: mm) in the balloon surface taken real-time during the inflation process

  • Vinicius Lube (PhD student)
  • Dr Liping Yu (Postdoctoral fellow)
  • Prof Gilles Lubineau (PI)