
#1
Jan208, 01:47 AM

P: 12

Hello All,
Can any one let me know the difference between Vonmises Stress criterion and Maximum Principle Stress criterion ?? And for what kind of materials " Brittle / Ductile " can they be used and why ?? Thanks in advance for your time. 



#2
Jan208, 07:38 AM

Sci Advisor
P: 2,283

Maximum Principle Stress Theory  According to this theory failure will occur when the maximum principal stress in a system reaches the value of the maximum stress at elastic limit in simple tension. This theory is approximately correct for cast iron and brittle materials generally.
Source: http://www.roymech.co.uk/Useful_Tabl...cs/stress.html Von Mises Stress (Distortion Energy Theory)  This theory proposes that the total strain energy can be separated into two components: the volumetric (hydrostatic) strain energy and the shape (distortion or shear) strain energy. It is proposed that yield occurs when the distortion component exceeds that at the yield point for a simple tensile test. Source: http://en.wikipedia.org/wiki/Yield_(engineering) More information on Von Mises Stress can be found here. General information on solid mechanics can be found here. CS 



#3
Jan208, 09:56 PM

P: 12

HI,
Thank you very much for very useful information and your precious time. Chandra. 



#4
Jul110, 05:24 AM

P: 1

Vonmises Stress Vs Maximum Principle Stresswith regards to the max. principal stress vs von mises stress, does a material yield or fail if the von mises is greater than the max. principal stress or visa versa? secondly, how is the von mises related to compressive strength (or minimun principal stress)? your help will be greatly appreciated regards Tach 



#5
Jul510, 04:38 PM

P: 61

You find Von Mises stress from the principle stresses by using a big ol gnarly equation or three. It is always a smaller value than maximum principle stress (by definition) BUT it is aligned in the direction that has to support the maximum shear load. This can be very helpful in design. hth (and i hope that I'm not too rusty on this subject) 



#6
Jul510, 06:06 PM

P: 5,462

This is an old thread.
What is the interest in revival? 



#7
Jul510, 06:10 PM

P: 61

A question was asked, I assumed it was cool to answer it. Silly me.
It would have been better to start a new thread? 


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