Dear all,

          I did a three point bending test on a brittle rod. I observed an oblique fracture (slant approx 45 degrees). It can be an easy conclusion that this 45 deg crack is due to shear failure. But i have the following questions

1. Can a shear band  occur in  bending mode? as in literature very frequently shear bands are reported in pure tension and compression.

2. What is the state of hydrostatic stress or the principal stresses along line of shear band (whether the hydrostatic or principal stresses increase or decrease with bending)? as it is well known that even in max shear state there exists normal stresses.

3. When i simulated the setup in LS Dyna using hydrostatic cut off stress (element fails on reaching a critical hydrostatic tensile stress) as failure criterion the results matches well with the experiment however  i still dont clearly understand how hydrostatic cut off stress predicts the slant crack very well.

Experts in the field please throw some light on the answers of the above questions. Thanks in advance.