Ok Sorry, It is a question. What is it Max3DShear stress , is a criterion? because i know a many programme how work with a Von Misse Stress(4 Theory-Energy of distorsion).

Hello Alin10,

Maximum shear stress failure theory is also know as the Tresca criteria. In the stress equations in the B31 codes (with exception) we combine stresses using Tresca theory. The exception is that for B31.3, Chapter IX, High Pressure Piping, K304.1.2 we provide equations for determining the required minimum wall thickness of straight pipe and this is based upon the von Mises theory of failure.

For more on this topic look through this site:

http://feaservices.com/fund_struct/fund_struct.html#General%203-D%20Stress%20State

and here:

http://documents.wolfram.com/applications/structural/AnalysisofStress.html

Regards, John.

The term stress intensity comes from the Nuclear code Sec III and B & PV code SEC VIII DIV 2 APPENDIX 4.

It means twice the max. shear stress. As you know that max. shear stress is the algebraic difference between the maximum and minimum principal stresses and the Tresca ( see John's reply above)criteria calls for failure when max. shear stress equals max. shear stress in simple tension test at yield point, which effectively makes it half y.p. value in tension , so we have an equation where the left hand side and the right hand side has a factor 0.5 . So to keep things simple it is better to divide both sides by a factor 0.5 is what we get as "stress intensity".

CAESAR II also allows the user the Von Mises criteria which is also essentially the max. Octahedral shear stress criteria ( max. shear stress on a plane which is equally oriented to the three principal directions).

Regards