Any experience with this fatigue method?

[trainguy]

All,

Have any of you used this method?

http://www.sdas.battelle.org/verity/technicalrefs/SS&fatigue.pdf

Any comments?

tg

 

[ESPcomposites]

The "your challenge" logic section seems a bit circular and perhaps misleading.

If you have a known geometry, you can find the stress concentration. They are saying their solution is mesh independent, but you can solve this via FEM if the mesh is fine enough.

If the stress concentration is very high, similar to a crack, then FEM will have a hard time converting (unless it is a p-element solver). But all of that is academic since you should use fracture mechanics.

To sum up: you can do this with a high density mesh, p-element solver, or perhaps that software.

Brian

http://www.espcomposites.com

 

[TGS4]

Yes - it was recently introduced to the ASME boiler & Pressure Vessel Code. We have used it extensively for fatigue calculations of weldments. Because it is based on actual test data, rather than guesstimates on SCFs, and the data-reduction method uses a fracture mechanics approach, we have found that it is relatively accurate in failure investigations.

Let me know if you have any questions on its application.

 

[bxtsafe]

I have quickly read some sections of some Journal Papers about this method, which was developed by Mr. P Dong (who work at Battelle) and I can say it really works.

P. Dong has developed a method which the stresses on an finite element is calculated using directly the nodal loads (forces and moments). In other words, the stresses are not either calculated using the strain-displacement matrix nor the displacement vector. I think this is one of the reasons that makes this method mesh-insensitive. This method looks like a modification of the FEM and guess I saw the method explanation in the following article:

Dong, P., 2001, "A Structural Stress Definition and Numerical Implementation for Fatigue Evaluation of Welded Joints,’’ Int. J. Fatigue, 23/10, pp. 865–876.


I attatched a PowerPoint file that has more information about the Battelle Mesh-Insensitive Method: "Fatigue Assessment of Weld Joints Using ANSYS, Verity & FE-Safe"

There is just 1 book that deals with the subject: "Modern Metal Fatigue Analysis" ( here:

http://www.emas.co.uk/structural_integrity-Fatigue_Modern_Metal_Fatigue_Analysis.html

)

There is another thread in this forum that is related with this subject, called "FE-Weld Fatigue mesh insensitive- Battelle" ( here:

http://www.eng-tips.com/viewthread.cfm?qid=210683

)


The following articles also have information of this Fatigue Assessment Mesh-Insensitive Method:

Dong, P., Hong, J.K., Cao, Z., “A Mesh-Insensitive Structural Stress Procedure for Fatigue Evaluation of Welded Structures", International Institute of Welding, IIW Doc. XIII-1902-01/XV-1089-01, July, 2001.

Hong Tae Kang, Pingsha Dong, J.K. Hong, "Fatigue analysis of spot welds using a mesh-insensitive structural stress approach", International Journal of Fatigue, October, 2006

Dong, P., 2005, "A Robust Structural Stress Method for Fatigue Analysis of Offshore/Marine Structures’’, Journal of Offshore Mechanics and Arctic Engineering , Vol. 127, pp. 68-74.

Myung Hyun Kim, Seong Min Kim, Young Nam Kim, Sung Geun Kim, Kyoung Eon Lee, Gyeong Rae Kim, "A comparative study for the fatigue assessment of a ship structure by use of hot spot stress and structural stress approaches", Ocean Engineering, July, 2009.

 

[3BSD]

You can use the Verity method if you like but one can also use the Effective Notch Stress method that is recommended by commission XII of IIW.