FEA- Influnce of Quad4 and Quad 8 in Stress Intensity factor

[Huini]

Hi,

I have no idea what is the difference in Quad 4 and Quad 8 usage when analyzing stress intensity factor. Can anyone help?

Thanks

 

[rb1957]

not knowing what a quad4 or a quad8 is (possibly NASTRAN plate elements), and guessing that you're calculating stress intensity from a path integral, I'd guess that the difference is the stress shape function (quad8 is parabolic and quad4 linear). and this would also be affected by mesh density (i'd expect that quad4 elements would have a denser mesh than quad8, to offset the element stress assumption).

 

[xerf]

It depends on the method used to compute the stress intensity factors. In some cases you might need to use singular elements to mesh the crack-tip. You must check the software documetation.