Hello everybody,
I have characterized the material behavior of a viscoelastic material and found out that:
G is time and temperature dependent.
K is temperature dependent but time-independent.
(Characterization of E and v were not performed)
I am trying to implement the viscoelastic material behavior and have the following problems/questions:
1) ANSYS (ref: manual) allows one to input G and K via TB,PRONY and TB,SHIFT. In my case, I can use TB,PRONY and TB,SHIFT for G, but not for K since K is not time dependent. Is there a way to put only Temperature dependent K (MP command does not allow me to define K but allows to define EX, GXY, NUXY)?
Sheldon says in his memo (STI080807_Viscoelasticity.pdf) that:
a) If either bulk or shear relaxation terms are not specified, they will be assumed to be constant (i.e., no relaxation for that term).
My comment: I do not want to specify any relaxation term for K, but I do want to implement temperature dependency.
b) If a user wants only shear relaxation, for example, bulk relaxation need not be specified (4). 4:"One should keep in mind that if only shear relaxation is defined, the bulk modulus remains constant - in other words, the effective poisons ratio would increase towards the value of 0.5, i.e., nearly-incompressible behavior."
My question: In this case, is poisson's ratio (my input MP,NUXY, which are calculated from G0 and K0) changing to keep K constant? I am not able to understand what is meant by bulk modulus remains constant --> does it mean that K is independent from time and temperature as well? Or does it mean that: it does not relax, but it remains temperature dependent?
2) Assuming that there is no way to put temperature dependent K alone with T and t dependent G, I calculated the temperature dependent PRXY from G and K and implemented it with MP/MPDATA commands as temperature dependent. Would you suggest a better way of implementing material data from the experimental data that I have? I definitely do not have the possibility to measure T-t dependent poisons ratio. I can measure E as time and temperature dependent (for validation for instance).
I am looking forward to your comments.
Best Regards,
Berkan
Robert Bosch GmbH
I have characterized the material behavior of a viscoelastic material and found out that:
G is time and temperature dependent.
K is temperature dependent but time-independent.
(Characterization of E and v were not performed)
I am trying to implement the viscoelastic material behavior and have the following problems/questions:
1) ANSYS (ref: manual) allows one to input G and K via TB,PRONY and TB,SHIFT. In my case, I can use TB,PRONY and TB,SHIFT for G, but not for K since K is not time dependent. Is there a way to put only Temperature dependent K (MP command does not allow me to define K but allows to define EX, GXY, NUXY)?
Sheldon says in his memo (STI080807_Viscoelasticity.pdf) that:
a) If either bulk or shear relaxation terms are not specified, they will be assumed to be constant (i.e., no relaxation for that term).
My comment: I do not want to specify any relaxation term for K, but I do want to implement temperature dependency.
b) If a user wants only shear relaxation, for example, bulk relaxation need not be specified (4). 4:"One should keep in mind that if only shear relaxation is defined, the bulk modulus remains constant - in other words, the effective poisons ratio would increase towards the value of 0.5, i.e., nearly-incompressible behavior."
My question: In this case, is poisson's ratio (my input MP,NUXY, which are calculated from G0 and K0) changing to keep K constant? I am not able to understand what is meant by bulk modulus remains constant --> does it mean that K is independent from time and temperature as well? Or does it mean that: it does not relax, but it remains temperature dependent?
2) Assuming that there is no way to put temperature dependent K alone with T and t dependent G, I calculated the temperature dependent PRXY from G and K and implemented it with MP/MPDATA commands as temperature dependent. Would you suggest a better way of implementing material data from the experimental data that I have? I definitely do not have the possibility to measure T-t dependent poisons ratio. I can measure E as time and temperature dependent (for validation for instance).
I am looking forward to your comments.
Best Regards,
Berkan
Robert Bosch GmbH
