Are the Newmark-beta parameters and mass and stiffness parameters of Rayleigh damping same? 3

[kumara123]

Hi, I have a confusion Newmark-beta parameters and mass and stiffness parameters. The literature says that Newmark-beta parameters used for the numerical attenuation while Rayleigh damping (stiffness and mass damping parameters) used for material damping in Numerical simulations. I'm not sure where to add Rayleigh damping parameters when modelling in Abaqus. When defining the material, damping can be added as α and β. Does mass damping parameter ([ɳ][1]) equal to α of Newmark -beta parameter and stiffness damping parameter ([ɳ][2])equal to β?

Thanks.

 

[rickfischer51]

They are not the same thing. Rayleigh damping represents actual damping in a structure. The beta in Newmark-beta is a convergence parameter that controlls stability of the solution.

Rick Fischer
Principal Engineer
Argonne National Laboratory

 

[IceBreakerSours]

Abaqus uses a generalization of the Newmark-beta method known as the Hilber-Hughes-Taylor method. These are implicit numerical schemes that allow, with the help of parameters, a user to vary the numerical damping - which can be very useful, if used appropriately/carefully. As an example, if you are trying to capture a sharp discontinuity in the solution (say, a shock wave in a high speed flow in front or on the sides of a bullet), regardless of what the material damping is, the shock wave will be dispersed over a finite region of space and that dispersion is because of the numerical damping, not material damping. Sharp discontinuities in the solution can arise in structural problems as well (e.g., models with interactions or cracks).

In HHT, you have three parameters to work with - alpha, beta, and gamma. Read this for more.

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[IceBreakerSours]

Edit:

..because of the numerical damping, not material damping.

The following statement is more accurate:

.. because of numerical damping, not material or structural damping.

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