Hi all,
I am trying to figure out how to define a nearly incompressible hyperelastic material in ANSYS 12.1 and could use some advice. I have uniaxial experimental data which I can use to obtain coefficients for different strain energy functions.
I would like to define the material as nearly incompressible to avoid using the U/P formulation, however, I am not sure how to specify the compression coefficients d_i in any of these strain energy functions.
While browsing the ANSYS documentation I found the following APDL commands are used to define an "approximately incompressible" rubber material in verification Test Case 56 :
MP,NUXY,1,0.495 ! POISSON'S RATIO NU1 = 0.495
DD1 = 2*(1-2*NU1)/(40+10)
DD2 = 2*(1-2*NU1)/(120+30)
TB,HYPER,1,2,2,MOONEY
TBTEMP,20 ! MOONEY COEFFICIENTS AT TEMP = 20
TBDATA,1,40,10,DD1
TBTEMP,40 ! MOONEY COEFFICIENTS AT TEMP = 40
TBDATA,1,120,30,DD2
It appears to me that in this case the Poissons ratio is defined as 0.495 and the compression coefficients are calculated from 2*(1-2*NU1)/(C01+C02). As far as I can figure out, this calculation is derived from the bulk / shear modulus and the relation K=2/d.
I was wondering if anyone could briefly explain the calculation of compressive coefficients for nearly incompressible materials or point me in the direction of the relevant theory in the documentation. Any advice or insight would be greatly appreciated!
Many thanks,
Dave
I am trying to figure out how to define a nearly incompressible hyperelastic material in ANSYS 12.1 and could use some advice. I have uniaxial experimental data which I can use to obtain coefficients for different strain energy functions.
I would like to define the material as nearly incompressible to avoid using the U/P formulation, however, I am not sure how to specify the compression coefficients d_i in any of these strain energy functions.
While browsing the ANSYS documentation I found the following APDL commands are used to define an "approximately incompressible" rubber material in verification Test Case 56 :
MP,NUXY,1,0.495 ! POISSON'S RATIO NU1 = 0.495
DD1 = 2*(1-2*NU1)/(40+10)
DD2 = 2*(1-2*NU1)/(120+30)
TB,HYPER,1,2,2,MOONEY
TBTEMP,20 ! MOONEY COEFFICIENTS AT TEMP = 20
TBDATA,1,40,10,DD1
TBTEMP,40 ! MOONEY COEFFICIENTS AT TEMP = 40
TBDATA,1,120,30,DD2
It appears to me that in this case the Poissons ratio is defined as 0.495 and the compression coefficients are calculated from 2*(1-2*NU1)/(C01+C02). As far as I can figure out, this calculation is derived from the bulk / shear modulus and the relation K=2/d.
I was wondering if anyone could briefly explain the calculation of compressive coefficients for nearly incompressible materials or point me in the direction of the relevant theory in the documentation. Any advice or insight would be greatly appreciated!
Many thanks,
Dave
