Direct Stress 1

[colar]

Does anybody have a good definition for "Direct Stress"? I have been asked as part of an upcoming job interview to prepare a short 10 minute lecture aimed at first year students regarding the principles of direct stress. Direct stress to me is simply tensile or compressive stress created by Tension, compression or bending loads (i.e. not shear stresses) but I wonder if I am missing something in my simplified definition.

 

[metengr]

"The Stress Tensor (or Stress Matrix)


Surface tractions, or stresses acting on an internal datum plane, are typically decomposed into three mutually orthogonal components. One component is normal to the surface and represents direct stress. The other two components are tangential to the surface and represent shear stresses."

http://www.efunda.com/formulae/solid_mechanics/mat_mechanics/stress.cfm