Do Ductile Materials Fail Due to Shear or Tensile Stress?

[Dell]

in general, do ductile matreials fail due to shear or tensile stress

i think that my lecturer said that brittle materials (such as concrete) will fail due to a low maximum shearing stress therefore breaking at 45 degrees in axial loading, and ductile materials have low tensile stress leaving a flat 180 degree break, but i read somewhere that it is the opposite, could someone clear this up for me

 

[Mapes]

You misremembered what your lecturer said, or that person was wrong. Ductile materials fail in shear.