The forecasting of crack propagation and fracture processes requires a high-level simulation software and precise definition of boundary conditions. With its high lateral measuring resolution, the ARAMIS system gives an excellent possibility of verifying numerical calculations of fracture processes.

Fig. 1: Set up
(cameras, CT specimen W=20 mm)

Tests on small specimens (fig. 1), where grains influence crack propagation, are as applicable as tests with large specimens (CT, SENB, etc.), or furthermore with the inspection of real cracked components.

The measuring results are the three dimensional displacements x,y,z (fig. 3) and the strain tensor. Out of it the distributions epsilon X and epsilon Y can be calculated and graphically shown or exported in an user specific ASCII-format. Fig. 3 shows the displacement distribution in z direction. Direct beneath the crack there is a thinning of material, above the punch the specimen gets thicker.

Fig. 4 and 5 describe the strain distribution in x perpendicular to ligament. In front of the crack tip a strain maximum occurs. The strain distribution suit to the shear fracture while crack propagation. According to this the strain in y (parallel to ligament) concentrates in front of the tips of crack. Along the ligament compression strain appears in y direction.

Furthermore not only the strain distribution also crack propagation on the specimen surface and macro specific values as crack opening displacement (CTOD, CMOD, COD) (fig.8) can be calculated.

The lateral resolution of the results allows for the assessment of the mesh used for simulation. In addition, tests for linear and non-linear processes are possible because of the high measuring resolution.