# Equivalent stress in a welded part

1. Nov 17, 2009

### guideonl

Hi everyone,

The practical equivalent stress in a welded part, subjected to torque and bending stresses, is the square root of the sum of the two squared shear stresses (from torque & equal shear) squared, + the normal stress (from bending) squared. Is it accepted/common to use this way to get the equivalent stress, or it must be computed from the 2 dimensional equation for the equivalent stress = the squared root of normal stress squared + 3 times the shear stress squared?
By the way, I found somewhere a similar equation to that mentioned above, with 2 times the shear stress squared instead of 3 times the shear stress squared. Is it a mistake or just another method?
Also, I am new in this forum, and I would like to know if there is a simpler way to present questions using engineering known formulas & symbols? If positive - please advise how to do so.

Thank you, Guideon

2. Nov 18, 2009

### nvn

guideonl: The 2 might be a typographic mistake, or might be applicable to a specific material, if clearly described. If in doubt, assume the 2 is a typographic mistake, and use 3, instead.

The first equation you described, although it is hard to understand the way you wrote it, appears to be a simplistic approximation, and not too accurate. The second equation you described is more accurate and more correct.

Yes, there is a standard symbology for typing mathematical equations in plain text. Use caret (^) for exponentiation, asterisk (*) for multiplication, solidus (/) for division, plus sign (+) for addition, hyphen (-) for subtraction, and parentheses (( )), brackets ([ ]), and braces ({ }) for grouping. The precedence of the above arithmetic operators, in order of decreasing precedence from left to right, is:

- (unary) ( ) ^ * / + -​

Therefore, an example of an equation is y = pi*[2*x^3 - (5*x)^2]/(3*x^0.5). Notice square root of x is written x^0.5. And notice in 2*x^3, x^3 is performed before multiplying by 2, because exponentiation has higher precedence than multiplication (see the above precedence list). Also, pi means 3.141 593.

3. Nov 18, 2009

### guideonl

Thank you nvn,
I am familiar with the symbols you wrote in your answer, but in my question related to symbols, I meant symbols for the stresses (such as sigma & tau Greek letters for the normal & shear stresses). How can I use such symbols at this forum?

Guideon

4. Nov 18, 2009