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Fatigue Analysis of Beams

Question asked by Kevin Eichler on Nov 29, 2014
Latest reply on Mar 24, 2015 by Matthew Jackson

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Hello,

I am trying to perform a simple fatigue analysis on a bike frame I have modeled using structural members. I performed a static analysis with all members being treated as beams and everything worked out fine. I then attempted to perform a fatigue analysis but after trying to add an event, I received the following error message; You need one or more static, nonlinear or linear dynamic to perform Fatigue Analysis. From reading I understand that apparently fatigue analysis doesn't support beams but I also want to avoid treating everything as a solid or converting to trusses as this would make the results less accurate.

I have looked through other posts and have found the similar problem but no good explanation for the solution as can be seen in the following link;

Re: Fatigue Study Error

Can anyone explain how to perform a fatigue analysis of a frame made from beams?

Things to note:

4 of the structural members do not have the required slenderness ratio to be considered beams, not sure if this affects the results at all, any input on this would be appreciated

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Jared Conway Nov 30, 2014 8:45 PM

as per the other forum post Fatigue Study Error

check the solidworks kb (customerportal.solidworks.com) to see if that enhancement request has been implemented. i'm not aware that it has. so you would need to switch to solid or shells (check on shells, not sure if they are valid for fatigue either).

normally I would recommend also checking the help but it doesn't say specifically what element types are supported

2015 SOLIDWORKS Help - Definitions for Fatigue

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Kevin Eichler @ Jared Conway on Nov 30, 2014 8:57 PM

Jared,

thank you for your input, unfortunately when I switched everything to solids the model failed to mesh at all, neither a coarse mesh or control meshes were possible. It seems I have hit a dead end. I have to perform this analysis for three different frames and do not have time to really alter the design.

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Jared Conway @ Kevin Eichler on Nov 30, 2014 9:55 PM

not much you can do when there is a software limitation. you'll need to do the geometry repair and idealization the old fashioned way.

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Mandar Parkhi @ Kevin Eichler on Mar 19, 2015 3:44 AM

try reducing the size of elements. After creating mesh, hide mesh display for better performance

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Matthew Jackson Mar 24, 2015 12:18 PM

Hi Kevin,

I would mesh the model using beam elements and either:

1. Use the stresses in the members to carry out the fatigue calculations by hand using the appropriate fatigue category from a relevant standard.

2. If your interested in the joint fatigue, for example, a weld then extract the forces and moments at the joints and calculate the stress in the weld and carryout the fatigue calculations by hand using the appropriate fatigue category from a relevant standard.

This is not as difficult as it seems.

Thanks.

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Jared Conway Nov 30, 2014 8:45 PM
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as per the other forum post Fatigue Study Error

check the solidworks kb (customerportal.solidworks.com) to see if that enhancement request has been implemented. i'm not aware that it has. so you would need to switch to solid or shells (check on shells, not sure if they are valid for fatigue either).

normally I would recommend also checking the help but it doesn't say specifically what element types are supported

2015 SOLIDWORKS Help - Definitions for Fatigue
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- Kevin Eichler @ Jared Conway on Nov 30, 2014 8:57 PM
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  Jared,
  
  thank you for your input, unfortunately when I switched everything to solids the model failed to mesh at all, neither a coarse mesh or control meshes were possible. It seems I have hit a dead end. I have to perform this analysis for three different frames and do not have time to really alter the design.
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  - Jared Conway @ Kevin Eichler on Nov 30, 2014 9:55 PM
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    not much you can do when there is a software limitation. you'll need to do the geometry repair and idealization the old fashioned way.
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  - Mandar Parkhi @ Kevin Eichler on Mar 19, 2015 3:44 AM
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    try reducing the size of elements. After creating mesh, hide mesh display for better performance
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Matthew Jackson Mar 24, 2015 12:18 PM
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Hi Kevin,

I would mesh the model using beam elements and either:

1. Use the stresses in the members to carry out the fatigue calculations by hand using the appropriate fatigue category from a relevant standard.

2. If your interested in the joint fatigue, for example, a weld then extract the forces and moments at the joints and calculate the stress in the weld and carryout the fatigue calculations by hand using the appropriate fatigue category from a relevant standard.

This is not as difficult as it seems.

Thanks.
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Fatigue Analysis of Beams

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