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Modelling edge cracks

Posted May 7, 2011, 9:06 a.m. EDT Materials, Studies & Solvers, Structural Mechanics 4 Replies

Hamechan Madhoo
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Hi, I am new to Comsol. I am trying to model stress intensity factors around a crack. All the variables I have set up thus far works, such as strain energy density, traction vectors and the so called J-integral. However, when I try setting up the function for stress intensity factor:

sqrt(Young's modulus*J-integral)

which should be in units of Pa*m^1/2, I keep getting a 'unit syntax error' response, and the function does not seem to work properly. I have re-checked my input parameters and I am sure they are correct, so I am not sure why it is not allowing me to derive the stress intensity factor in units of stress times the root of a distance, which is the standard method for this type of calculation.

Any suggestions on how best to handle such calculations will be appreciated.

Thanks,
Amrit
4 Replies Last Post Feb 4, 2016, 2:39 a.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago May 7, 2011, 9:37 a.m. EDT
Hi

In which version are you ? in 3.5 there is an issue with sqrt() of units or units in fractional power, partly (only) solved in v4.
To override the unit warning you can make them "unitless" first before you call the value in a formula with fractional powers.

Orange unit warning issues does not change the results, provided your values are coherent (then the user is 100% responsible for the units check, that all the difference) so the results should be valid

--
Good luck
Ivar
Hi In which version are you ? in 3.5 there is an issue with sqrt() of units or units in fractional power, partly (only) solved in v4. To override the unit warning you can make them "unitless" first before you call the value in a formula with fractional powers. Orange unit warning issues does not change the results, provided your values are coherent (then the user is 100% responsible for the units check, that all the difference) so the results should be valid -- Good luck Ivar
Hamechan Madhoo
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Posted: 1 decade ago May 11, 2011, 8:31 a.m. EDT
Hi,

Thank you for the response.

I am using version 4.0, so I guess it should recognise the units. However, you are right orange unit warning issues does not change the results. I checked the results and they are indeed correct, so I will just make them 'unitless.'

Cheers,
Amrit
Hi, Thank you for the response. I am using version 4.0, so I guess it should recognise the units. However, you are right orange unit warning issues does not change the results. I checked the results and they are indeed correct, so I will just make them 'unitless.' Cheers, Amrit
Ismail Isa Danfillo
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Posted: 9 years ago Jul 7, 2015, 2:05 p.m. EDT
Hi,

I am also trying to determine SIF for 3D geometry (see attached model). The idea is to compare the line (1D), surface (2D) and volume (3D) J-integral methods. But my results do not seem to be consistent so far. Any ideas s to why????

I have used the contour equation:- 2*((solid.Ws)+(-((solid.sx+solid.sxy)*uX*Nx+(solid.sxy+solid.sy)*vX*Ny))) for all cases only difference is the type of integral and edges, boundary, and domains used in derrived value node respectively.

Thanks so much in advance.
Kind regards
ISA D.
Hi, I am also trying to determine SIF for 3D geometry (see attached model). The idea is to compare the line (1D), surface (2D) and volume (3D) J-integral methods. But my results do not seem to be consistent so far. Any ideas s to why???? I have used the contour equation:- 2*((solid.Ws)+(-((solid.sx+solid.sxy)*uX*Nx+(solid.sxy+solid.sy)*vX*Ny))) for all cases only difference is the type of integral and edges, boundary, and domains used in derrived value node respectively. Thanks so much in advance. Kind regards ISA D.
Maizuar Maizuar
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Posted: 9 years ago Feb 4, 2016, 2:39 a.m. EST
Hi Ismail

I am new with comsol and use comsol 5.0. I am trying to model the cracks at concrete beam. I believe you have solved the problem with your previous crack model, So could you please share me how to model the crack with comsol in detail explanation.

Many thanks for your helps and kindness.


Regards


Maizuar
Hi Ismail I am new with comsol and use comsol 5.0. I am trying to model the cracks at concrete beam. I believe you have solved the problem with your previous crack model, So could you please share me how to model the crack with comsol in detail explanation. Many thanks for your helps and kindness. Regards Maizuar

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