Measuring damping using Abaqus and viscoelastic material
I am using Abaqus to simulate the damping response of a constrained layer damper made of rubber, which is a hyperelastic and viscoelastic material. The structure is a hollow cylindrical cantilever, and I am measuring damping by applying a static load to the free end of the structure and then deactivating the load for the implicit step. The Ogden model with instantaneous hyperelasticity was used to define the hyperelastic properties, and shear-relaxation test data was used to define the time-domain viscoelasticity. However, every time I run the simulation I get a non-damped response.
Is there another way to measure the damping of the material using Abaqus, or is it hard to achieve damping on such a structure? I would appreciate any input regarding this.
Your approach should work. I recommend that you make sure your FE mesh is refined enough, and that your material model dissipates energy at the strain levels and frequencies you are applying.
How do I make sure that the material model dissipates energy at the strain levels and frequencies I am applying?
I would create a single load-unload cycle with the appropriate strain rate (based on your eigenfrequency or known loading rate), and then simulate the stress-strain response for the selected material model. This can be done super fast using MCalibration.
If the load-unload cycle in stress-strain space contains some amount of hysteresis then your material model will clearly dissipate energy.
Thank you Jorgen, this is very helpful.
I have another question about defining viscoelasticity: how do I get the normalized shear modulus if I have relaxation test data and want to define gR(t) in Abaqus?