Chapter 6 – Sheet-metal Forming

Stress state in deformation processes
• The geometry of the workpiece can be essentially three
dimensional (i.e., rod or bar stock) or two dimensional (i.e.,
thin sheets).
• The state of stress is described by three principal stresses,
which act along axes perpendicular to principal planes.
• The principal stresses are by convention called σσσσ 1 , σσσσ 2 and
σσσσ 3 where σσσσ 1 > σσσσ 2 > σσσσ 3
σσσσ 1
σσσσ 3
σσσσ 2
Principal stresses on an element in
a three-dimensional stress state • Hydrostatic stress state is when
σσσσ 1 = σσσσ 2 = σσσσ 3
Suranaree University of Technology Tapany Udomphol
Jan-Mar 2007