In order to assess the stress-state in a cracked shear
specimen and also to calculate the SIFs in Mode I and II,
Finite Element Analysis (FEA) was carried out using the
software FRANC2D from Cornell Fracture Group. The mesh
for the model is built up of six-node iso-parametric triangular
elements and from standard quarter-point elements
used in linear fracture mechanics which are designed to
capture the characteristic 1= ffiffi
r p singularity and the K-field.
Unit loading is exerted on the two outer pinholes and the two inner pinhole surfaces were modelled
as fixed yet able to rotate freely about their axis. Although
the fixation of the specimen on the four gripping pins is
tight in order to avoid backlash during load cycling and
therefore considerable friction opposing the free rotation
of the specimen around the pins is anticipated, the effect
of this phenomenon is not expected to play any role to
the accuracy and validity of the FEA results since the loading/fixing
points are far from the gauge area of the specimen
and therefore Saint Venant’s principle applies.