von mises stress or principal stress?
von mises stress or principal stress?
(OP)
Can anybody explain the difference between von mises stress and principal stress?
Any help would be great!
Any help would be great!
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von mises stress or principal stress?
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von mises stress or principal stress?von mises stress or principal stress?(OP)
Can anybody explain the difference between von mises stress and principal stress?
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RE: von mises stress or principal stress?
SI=max(|S1-S2|,|S1-S3|,|S2-S3|)
where Si are the principal stresses.
It also equals two times the maximum shear stress and it is used in the von Mises failure criterion for checking the acceptability of stress states.
You should consult a basic theory book on failure criteria to know more: it's a quite complex subject.
prex
motori@xcalcsREMOVE.com
http://www.xcalcs.com
Online tools for structural design
RE: von mises stress or principal stress?
The von Mises yield criterion uses stresses on octahedral planes.
This subject is complex, but well described in a variety of textbooks such as Mechanical Engineering Design by Shigley and Mischke or Mechanical Behavior of Materials by Dowling. Try the following website for an intro:
http://www.efunda.com/formulae/solid_mechanics/mat_mechanics/plane_stress_principal.cfm?search_string=principal%20stress
http://www.efunda.com/formulae/solid_mechanics/failure_criteria/failure_criteria_ductile.cfm#VonMises
RE: von mises stress or principal stress?
RE: von mises stress or principal stress?
The formula for the von Mises stress should be:
SvM=sqrt(S12+S22+S32-S1S2-S2S3-S3S1)
prex
motori@xcalcsREMOVE.com
http://www.xcalcs.com
Online tools for structural design
RE: von mises stress or principal stress?
Von Mises stress is a function of the stress state. Each state has only one value of the Von Mises stress. In continuum mechanics, you learn that any stress state can be broken down into the hydrostatic and deviatoric stress tensors. The hydrostatic stress is the stress which is trying to change the volume of an element of material. The deviatoric stress is trying to change the shape. The Von Mises is related to the deviatoric stress. The Von Mises theory of failure claims that failure of ductile materials is due to the change in shape (twist, pull, bending.)
Von Mises can not be used for predicting fatigue. (See Socie, Multiaxial Fatigue, page 418)
Just my few cents.
Doug
RE: von mises stress or principal stress?
RE: von mises stress or principal stress?
Doug