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Weld Stress

Weld Stress

Weld Stress

Hello all, I am trying to analyze the stress in an attachment weld in order to determine the minimum allowable fillet weld leg length (w) by using the following formula:

w = f/fw

where f = actual force [lbs]
      fw = maximum allowable unit force on an equal-leg
           fillet weld equal to 1"  [lbs/linear inch]
          = .707*E*Sa
      E = joint efficiency based on throat area
      Sa = maximum allowable stress of the base metal

I am trying to find the correct value for the allowable stress of a weld (Sa).  I am using E70XX electrodes and welding A36 structural steel I beams and angles to a SA-516-70 presure vessel shell.  

My questions are as follows:

1) is the value of Sa = 21,000 psi
2) is it correct to assume an E of 1.0?

I have also seen the formula for fw written as follows:

fw = .707*w T

where fw = allowable force on the fillet weld, 1" long
      w = leg size of fillet weld
      T = allowable shear stress on throat of weld

any comments?

RE: Weld Stress

The base allowable stress in tension, Sa, is specified in BPVC and depends on the material and the temperature.  For specification SA-516 70 temperature range of -20F to 650F is 17,500 psi.

The joint efficiency (E) used in calculation for seamless shells is 1.  For weld joints subject to tension the values depend on the type of weld and testing processes.  The efficiency can vary from .45 to 1.

Hope this helps.


RE: Weld Stress

I have some information on the design of fillet welds you may find useful www.gowelding.com

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