Comparison of two full-field identification methods for the wedge splitting test on a refractory

Abstract

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.

Analysis of a castable refractory using the wedge splitting test and cohesive zone model

“…The mesh used for T3DIC and one displacement field (for image no. 263, i.e., the last of the envelope, see Figure 2) is shown in Figure 3 shown that no major side branches were formed and only a single macrocrack had propagated in the groove [19].…”

“…It is possible to see the sample and the loading devices (i.e., wedge, cylinders and blocks). Two grooves (i.e., vertical notches, evidenced in the right image in Figure 1) are machined on the two opposite faces of the sample to reduce the local thickness and guide the crack propagation vertically [19]. The Young's modulus (E) and Poisson's ratio (ν) used for the investigated methods are equal to 17 GPa (measured by the bar resonance method [39]), and 0.2, respectively.…”

“…The Young's modulus (E) and Poisson's ratio (ν) used for the investigated methods are equal to 17 GPa (measured by the bar resonance method [39]), and 0.2, respectively. The fracture energy calculated as the mean R-curve value (obtained by Integrated-DIC) is of the order of 68 J/m 2 [19]. The test was driven by setting the velocity of the machine actuator to 1.3 µm/s, and 313 pictures (reference + 312) were taken for both faces of the specimen at a rate of one picture each 8 s. The images were simultaneously acquired with two Canon T5 cameras with 28-135 mm lenses, with the illumination provided by LEDs.…”

“…The red circles mark the envelope of the curve that will be used by the identification routine with always increasing opening displacements. Let us note that since the test was interrupted before final failure of the sample, only a lower bound to the work of fracture, and to the fracture energy can be obtained [19]. Given the fact that the first picture was not acquired at zero load and a nonlinear model will be used, the displacement field accounting for this load offset is an additional unknown when calibrating constitutive parameters [40].…”

“…Recently, several studies have reported on how to treat such results and obtain further information from WSTs [14,15,16,17,18,19].…”