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model aka hyperelastic_seal errors: non-integral power of negatic number
Posted 12.01.2012, 12:52 GMT-5 Structural Mechanics Version 4.1 1 Reply
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Hallo!
I am trying to model a 2D system similar to hyperelastic_seal. Unfortunatelly I get very often an error, especially when I want to make the mesh finer. If the mesh is coarse I got unsatisfactory results as two bodies are overlaping although there is a contact boundary. What should I change in the model. I attach both model file and a picture with plot of the any (but not ok) result. I got also similar error if I want compress the ring more than certain limit (both in case of predefined displacement or body load on the top body). What is the reason and solution/workaround?
Error log:
Segregated group 1
Attempt to evaluate non-integral power of negative number.
- Function: ^
Failed to evaluate temporary symbolic derivative variable.
- Variable: mod1.solid.J@VDN$mod1.solid.Cl22
- Defined as: ((mod1.solid.Cl33*mod1.solid.Cl11)*(0.5*((((mod1.solid.Cl11*mod1.solid.Cl22)-(mod1.solid.Cl12^2))*mod1.solid.Cl33)^(-0.5))))
Failed to evaluate temporary symbolic derivative variable.
- Variable: mod1.solid.Jel@VDN$mod1.solid.Cl22
- Defined as: (mod1.solid.FiiZZ*(mod1.solid.FiiYY*(mod1.solid.FiiXX*(((mod1.solid.Cl33*mod1.solid.Cl11)*(0.5*((((mod1.solid.Cl11*mod1.solid.Cl22)-(mod1.solid.Cl12^2))*mod1.solid.Cl33)^(-0.5))))))))
Failed to evaluate temporary symbolic derivative variable.
- Variable: mod1.solid.II1@VDN$mod1.solid.Cl22
- Defined as: ((mod1.solid.I1*(((mod1.solid.FiiZZ*(mod1.solid.FiiYY*(mod1.solid.FiiXX*(((mod1.solid.Cl33*mod1.solid.Cl11)*(0.5*((((mod1.solid.Cl11*mod1.solid.Cl22)-(mod1.solid.Cl12^2))*mod1.solid.Cl33)^(-0.5)))))))))*((-0.66666666666666663)*(mod1.solid.Jel^(-1.6666666666666665)))))+((mod1.solid.Jel^(-0.66666666666666663))*(((mod1.solid.FiiYY^2)))))
Failed to evaluate temporary symbolic derivative variable.
- Variable: mod1.solid.Ws@VDN$mod1.solid.Cl22
- Defined as: (mod1.solid.Ji*(((mod1.solid.C10*(((mod1.solid.I1*(((mod1.solid.FiiZZ*(mod1.solid.FiiYY*(mod1.solid.FiiXX*(((mod1.solid.Cl33*mod1.solid.Cl11)*(0.5*((((mod1.solid.Cl11*mod1.solid.Cl22)-(mod1.solid.Cl12^2))*mod1.solid.Cl33)^(-0.5)))))))))*((-0.66666666666666663)*(mod1.solid.Jel^(-1.6666666666666665)))))+((mod1.solid.Jel^(-0.66666666666666663))*(((mod1.solid.FiiYY^2)))))))+(mod1.solid.C01*((((mod1.solid.Jel^(-1.3333333333333333))*((0.5*(((((mod1.solid.FiiYY^2)))*(mod1.solid.I1*2))-((mod1.solid.Cel22*2)*((mod1.solid.FiiYY^2)))))))+(mod1.solid.I2*(((mod1.solid.FiiZZ*(mod1.solid.FiiYY*(mod1.solid.FiiXX*(((mod1.solid.Cl33*mod1.solid.Cl11)*(0.5*((((mod1.solid.Cl11*mod1.solid.Cl22)-(mod1.solid.Cl12^2))*mod1.solid.Cl33)^(-0.5)))))))))*((-1.3333333333333333)*(mod1.solid.Jel^(-2.333333333333333)))))))))+((0.5*mod1.solid.kappa)*(((mod1.solid.FiiZZ*(mod1.solid.FiiYY*(mod1.solid.FiiXX*(((mod1.solid.Cl33*mod1.solid.Cl11)*(0.5*((((mod1.solid.Cl11*mod1.solid.Cl22)-(mod1.solid.Cl12^2))*mod1.solid.Cl33)^(-0.5)))))))))*(((-1)+mod1.solid.Jel)*2)))))
Failed to evaluate variable.
- Variable: mod1.solid.SlY
- Defined as: (2*d(mod1.solid.Ws,mod1.solid.Cl22))
Failed to evaluate expression.
- Expression: d((-(mod1.solid.SlX*test(mod1.solid.elX)+2*mod1.solid.SlXY*test(mod1.solid.elXY)+mod1.solid.SlY*test(mod1.solid.elY)+mod1.solid.SlZ*test(mod1.solid.elZ))*mod1.solid.d)*(dvol),{test@3})
Thanks for replies.
Pawel
I am trying to model a 2D system similar to hyperelastic_seal. Unfortunatelly I get very often an error, especially when I want to make the mesh finer. If the mesh is coarse I got unsatisfactory results as two bodies are overlaping although there is a contact boundary. What should I change in the model. I attach both model file and a picture with plot of the any (but not ok) result. I got also similar error if I want compress the ring more than certain limit (both in case of predefined displacement or body load on the top body). What is the reason and solution/workaround?
Error log:
Segregated group 1
Attempt to evaluate non-integral power of negative number.
- Function: ^
Failed to evaluate temporary symbolic derivative variable.
- Variable: mod1.solid.J@VDN$mod1.solid.Cl22
- Defined as: ((mod1.solid.Cl33*mod1.solid.Cl11)*(0.5*((((mod1.solid.Cl11*mod1.solid.Cl22)-(mod1.solid.Cl12^2))*mod1.solid.Cl33)^(-0.5))))
Failed to evaluate temporary symbolic derivative variable.
- Variable: mod1.solid.Jel@VDN$mod1.solid.Cl22
- Defined as: (mod1.solid.FiiZZ*(mod1.solid.FiiYY*(mod1.solid.FiiXX*(((mod1.solid.Cl33*mod1.solid.Cl11)*(0.5*((((mod1.solid.Cl11*mod1.solid.Cl22)-(mod1.solid.Cl12^2))*mod1.solid.Cl33)^(-0.5))))))))
Failed to evaluate temporary symbolic derivative variable.
- Variable: mod1.solid.II1@VDN$mod1.solid.Cl22
- Defined as: ((mod1.solid.I1*(((mod1.solid.FiiZZ*(mod1.solid.FiiYY*(mod1.solid.FiiXX*(((mod1.solid.Cl33*mod1.solid.Cl11)*(0.5*((((mod1.solid.Cl11*mod1.solid.Cl22)-(mod1.solid.Cl12^2))*mod1.solid.Cl33)^(-0.5)))))))))*((-0.66666666666666663)*(mod1.solid.Jel^(-1.6666666666666665)))))+((mod1.solid.Jel^(-0.66666666666666663))*(((mod1.solid.FiiYY^2)))))
Failed to evaluate temporary symbolic derivative variable.
- Variable: mod1.solid.Ws@VDN$mod1.solid.Cl22
- Defined as: (mod1.solid.Ji*(((mod1.solid.C10*(((mod1.solid.I1*(((mod1.solid.FiiZZ*(mod1.solid.FiiYY*(mod1.solid.FiiXX*(((mod1.solid.Cl33*mod1.solid.Cl11)*(0.5*((((mod1.solid.Cl11*mod1.solid.Cl22)-(mod1.solid.Cl12^2))*mod1.solid.Cl33)^(-0.5)))))))))*((-0.66666666666666663)*(mod1.solid.Jel^(-1.6666666666666665)))))+((mod1.solid.Jel^(-0.66666666666666663))*(((mod1.solid.FiiYY^2)))))))+(mod1.solid.C01*((((mod1.solid.Jel^(-1.3333333333333333))*((0.5*(((((mod1.solid.FiiYY^2)))*(mod1.solid.I1*2))-((mod1.solid.Cel22*2)*((mod1.solid.FiiYY^2)))))))+(mod1.solid.I2*(((mod1.solid.FiiZZ*(mod1.solid.FiiYY*(mod1.solid.FiiXX*(((mod1.solid.Cl33*mod1.solid.Cl11)*(0.5*((((mod1.solid.Cl11*mod1.solid.Cl22)-(mod1.solid.Cl12^2))*mod1.solid.Cl33)^(-0.5)))))))))*((-1.3333333333333333)*(mod1.solid.Jel^(-2.333333333333333)))))))))+((0.5*mod1.solid.kappa)*(((mod1.solid.FiiZZ*(mod1.solid.FiiYY*(mod1.solid.FiiXX*(((mod1.solid.Cl33*mod1.solid.Cl11)*(0.5*((((mod1.solid.Cl11*mod1.solid.Cl22)-(mod1.solid.Cl12^2))*mod1.solid.Cl33)^(-0.5)))))))))*(((-1)+mod1.solid.Jel)*2)))))
Failed to evaluate variable.
- Variable: mod1.solid.SlY
- Defined as: (2*d(mod1.solid.Ws,mod1.solid.Cl22))
Failed to evaluate expression.
- Expression: d((-(mod1.solid.SlX*test(mod1.solid.elX)+2*mod1.solid.SlXY*test(mod1.solid.elXY)+mod1.solid.SlY*test(mod1.solid.elY)+mod1.solid.SlZ*test(mod1.solid.elZ))*mod1.solid.d)*(dvol),{test@3})
Thanks for replies.
Pawel
Attachments:
1 Reply Last Post 13.01.2012, 09:21 GMT-5
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Posted:
1 decade ago
I can see from the attached figure that the three parts are sticking together at two points along the symmetry line. That is because they are connected (cannot separate) at these points due to the default Form Union node at the end of the geometry. That would be fine if these points are expected to remain in contact throughout the simulation. If they can lift off however then you should either move the parts apart such that there is an initial gap or select “Form an Assembly” instead of “Form a Union”.
Also for stationary contact problems it is better to apply the load gradually so that contact can be gradually established. I usually do that by multiplying the prescribed load/displacement with a “para” variable that increases gradually from zero to one using a Parametric Sweep.
Nagi Elabbasi
Veryst Engineering
Also for stationary contact problems it is better to apply the load gradually so that contact can be gradually established. I usually do that by multiplying the prescribed load/displacement with a “para” variable that increases gradually from zero to one using a Parametric Sweep.
Nagi Elabbasi
Veryst Engineering