The effect of non-singular term (T-stress) on mode I/III cracking parameters of brittle materials, Numerical and experimental study using different beam and disc shape specimens made of marble rock
Amir Mousavi, M.R.M. Aliha, Hadi Khoramishad, Hamid Reza Karimi
Abstract
This study focuses on less-studied mode I/III fracture cracking behaviour. Seven specimens (ENDC, DNDC, SCB, ENDB, ATPB, TPB-IC, and SENB) were analyzed numerically and experimentally. Results show in pure mode-I, the specimens show identical K Ic values (1.22 to 1.54 MPa√m). Especially if the K Ic was measured by compressive specimens (ENDC and DNDC with K Ic of 1.22 and 1.30 MPa√m, respectively) and was neglected. In these cases, the difference in measured K Ic values directly relates to the T -stress value in pure mode-I. So, higher T-stress values increase the K Ic and vice versa. In pure mode-III, which can only simulated by ENDB, ENDC, and DNDC specimens, the difference in measured K IIIc values was enormous, as 0.99 MPa√m for ENDB, 2.0 MPa√m for ENDC and 2.53 MPa√m for DNDC. Comparing the trend of K IIIc for specimens shows the same as K Ic , K IIIc also has a direct relation with the T-stress. The affectability of fracture toughness from T -stress shows the importance of accounting for it in calculations. The trends show that the ENDB, ENDC, and DNDC specimens have considerably negative T -stress values, with different trends. Moving from pure mode-I to pure mode-III, the ENDB has a low-negative T-stress that becomes high-negative (about -0.32 to -2.5 MPa). Meanwhile, of DNDC, it is the opposite; the T-stress is high-negative for pure mode-I and becomes low-negative for pure mode-III (about -2.54 to -0.77 MPa). For ENDC, the T -stress is almost constant moderate-negative in all the mixed mode I/III conditions (about -2.1 MPa).