Experimental And Numerical Analysis OfBoundary Effects In Uniaxial Tensile Tests

Results are presented of experiments and simulations of cylindrical specimens loaded in tension under different boundary conditions. It is shown that the global softening behaviour of a specimen is affected substantially by changing the boundary conditions. Experiments were performed using four different geometries and two different boundary conditions. One set-up was already available in which the loading platens were not allowed to rotate. A new testing machine was build for loading the specimens between freely rotating boundaries. Next to the experiments on sandstone and concrete, simulations were carried out with a numerical lattice model. The effects on the crack patterns when changing the boundary conditions are simulated quite realistically with the lattice model.