engleski

On the use LEFM, NLFM and CZM in the analysis of a DCB test

Double cantilever beam (DCB) is the standard specimen for determining fracture resistance in mode I. This is usually done by using simple data-reduction schemes that combine linear- elastic fracture mechanics (LEFM) and beam theory (either Euler-Bernoulli or Timoshenko). On the other hand, a richer modelling of the problem through the use of cohesive-zone models (CZMs) is also possible and widely used. In our recent work [1, 2], we have shown that, unlike what is often stated in the literature, LEFM can be accurately adopted for DCB problems even in cases with large damage process zone (DPZ). We have demonstrated that in a general case, neither the critical energy release rate (Gc) nor the critical value of the J integral (Jc) is equal to the area under the traction- separation law of CZM. Moreover, we have shown that the difference between Gc and Jc, and therefore the applicability of LEFM to problems with quasi-brittle failure, is not due to the size of the DPZ, but it is due to the change of the energy dissipated in front of the crack tip with crack propagation. We have also proposed a novel data-reduction scheme called 'Enhanced simple beam theory' (ESBT) that is based on Timoshenko beam theory and LEFM, and does not require the measurement of the crack length. Additionally, we have developed a closed-form solution for a DCB with arms modelled as Timoshenko beams and a bi-linear CZM at the interface [3]. This solution, that is completely free of any convergence problems or numerical errors, is also implemented in an open-source software.

tical solution ; Timoshenko beam thtificeory ; Linear-elastic fracture mechanics

nije evidentirano