An advanced finite-element model for the complete failure process of a double notched specimen with crack tip blunting caused by yielding and subsequent crack propagation is used for the simulation of realistic specimens. Cracks in a homogeneous material and bimaterial cracks are studied. The calculated load-displacement curves show generally the shape known from experiments and theoretical considerations. The simulation allows determination of a working range of set up parameters like geometry, test speed or clamping conditions. The numerical model simulates crack propagation on the basis of a criterion which is similar to the energy release rate. The essential work of interfacial fracture method provides a method to determine the fracture toughness from load-displacement curves. This method is well suited to check the numerical simulation because both use an energy based failure criterion. If applied to simulated load-displacement curves the resulting essential work of interfacial fracture should directly match the fracture criterion used as input for the simulation. In fact, the data reduction of the simulated curves results in values for the fracture toughness that almost perfectly match the input values of the simulation. This agreement is a strong argument for the consistency of the simulation and the data reduction scheme.