Fillet Weld (Spatial Load) Calculator - Shear Stress from Torque Load

[Anonymous]

I'm trying to calculate the Resultant Stress for combined loading on a circular fillet weld using the fillet weld spatial load calculator. It's a 150lb axial load and a 150 ft-lb torque load. The weld height is .0625" and the beam diameter is 3.00".

I made an excel file to quickly do this for about 60 other cases. I followed the equations in the "Engineer's Handbook" to calculate the stresses (https://help.autodesk.com/view/INVNTOR/2020/ENU/?guid=GUID-D5462EC9-8D5D-4092-B69E-711E6301A9B8).

The Normal Stress from the Axial Load calculated from the excel file matches the output from Inventor but the Resultant Shear Stress from the Torque Load is low and high depending on the size of the weld height. The wrong Shear Stress also throws off the calculated Resultant Stress.

Something is either not explained in the Handbook or the Calculator is messed up. my guess is there's some type of relation or factor used for weld size and weld length that is not explained. Or I made a mistake. I attached the files. 

[johnsonshiue]

Hi! Please attach all the iam and ipt files (zipped). The iam file by itself is not enough for us to understand the issue.

Many thanks!

[Anonymous]

There are no .ipt files required, I'm only using the Design Accelerator which can be edited. Right click on "Fillet Weld (Spatial Load)" and select "Edit using Design Accelerator". That will bring you to the dialog box. 

[Anonymous]

I get what you're saying now, the .zip file is attached. There are no parts in the assembly as I noted above. 

[Anonymous]

Use the attached Excel calculator, it is updated because there were a couple mistakes on the original. It still follows the "Standard Calculation Procedure" and the answers still do not match the Inventor Calculations.

In the original post, I mentioned that it seemed like they were using factors somewhere in the calculation of the Shear Stress from the Torque Load. I added another calculation that gets very close to the Inventor Calculations. I used the factors on the "Conversion Factors for Weld Joints" page (https://help.autodesk.com/view/INVNTOR/2020/ENU/?guid=GUID-1569FB41-0D8D-46EC-9452-02840794B06F). I thought these were only for use in the "Method of Comparative Stresses". I think there is an explanation missing in the "Shear Stress caused by Torsion Moment T" section or the Inventor calculation is wrong. Either way, Inventor does not follow what is outlines in the Calculation procedure (https://help.autodesk.com/view/INVNTOR/2020/ENU/?guid=GUID-D5462EC9-8D5D-4092-B69E-711E6301A9B8).

Hopefully, this clears up what I'm looking for.

Thanks, Justin.

[jan.vonasek · Accepted solution]

Hi Justin,

your formulas are right except one. Help formulas are related to rectangular like profiles where is Total shear stress calculated from X and Y components. For circle weld is used directly Y component. This is the reason for different result.

Thanks to report it, we need to mention it in our help.
Regards,

Jan

[Anonymous]

Hi Jan,

That makes sense, thank you for the help!

Justin

[crcasper]

There are still massive issues with the calculation procedure Inventor is using, (in my opinion) it is not following the accepted methods laid out in the widely used Shigley text.

The fillet weld spatial calculator should be used with caution, and if you don't know how to do the calculations by hand then you shouldn't be using the calculator.

Incident ID: 90750