Two full-field identification methods are applied to the Wedge Splitting Test (WST) to obtain crack tip positions, stress intensity factors (SIFs) and T -stress.The first method is based on Finite Element Model Updating (FEMU), and the second is integrated digital image correlation (IDIC). Both are applied to a simplified virtual experiment and then to a cyclic WST. The gray level residuals are used to assess which results are more trustworthy. Fracture energy analyses are performed to validate the estimated R-curves.

A cohesive zone approach is applied to the Wedge Splitting Test (WST) using the finite element code Abaqus to obtain the tensile strength, the fracture energy and insight about the crack wake region. A Finite Element Model Updating (FEMU) method, with a cost function based on the measured load (FEMU-F), is used to calibrate the sought parameters. Digital Image Correlation (DIC) provided the kinematic boundary conditions, and the images were also used to define the geometry for the finite element analysis. Besides the fracture energy analysis and the experimental load, gray level images and displacement fields are analyzed in order to validate the results. The cohesive region is active in the whole analyzed test as confirmed by estimates using the cohesive length.

International audienceOne of the key mechanical properties of refractories is their toughness. The latter can be evaluated via wedge splitting tests. One such test is analyzed herein with an integrated approach to digital image correlation. The position of the crack tip, stress intensity factors and T-stress are estimated on two faces of the tested sample made of a refractory castable during the whole cyclic test. It is shown that the change of energy release rate with the crack length can be determined at each time step of the experiment

The influence of the cooling rate after melting on the crystalline weight fraction of pure poly(tetrafluoroethylene) (PTFE) was derived from differential scanning calorimetry tests. Specimens made of pure or filled PTFE were manufactured by isostatic or constrained uniaxial cold pressing, up to different values of the porosity. Dilatometry tests were carried out on these specimens while imposing various heating–cooling treatments. The deformations recorded during these tests strongly depend on the mode and level of compaction. The original procedures presented, herein, made it possible to identify that these macroscopic deformations, which are strongly anisotropic for uniaxially pressed specimens, result from the combination of different independent mechanisms. The mechanisms that were distinguished are reversible thermal expansion, void closure, crystalline to amorphous and vice versa transformations, and recovery, which were not observed for isostatically pressed specimens. It was also shown that, after being subjected to a standard sintering treatment, anisotropically pressed specimens still exhibit anisotropic crystallization strains. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers