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Can the heating of the spring in oscillator be modeled by a velocity dependent force?

Physics Asked by Chegon on January 27, 2021

In a damped oscillator, the damping term is represented by a velocity dependent force $b dot{x}$. This makes sense if the damping is due to viscosity of the medium.

Is this modeling correct for the energy dissipation due to heating of the spring? I understand that this heating also comes from friction but I can’t visualize if it can also be modeled as velocity dependent.

2 Answers

You can do it in an indirect way.

For example, consider a heating model where the energy being dissipated into heat at a given moment in time is proportional to the kinetic energy of the spring at that time, multiplied by some “dissipation constant”. In that way, the amount of energy going into heating the spring becomes implicitly dependent on the velocity of the spring thanks to $KE = frac{1}{2}mv^2$.

Answered by aghostinthefigures on January 27, 2021

The standard way to model the internal energy dissipation (i.e. hysteretic damping, or in viscoelastic materials) for oscillatory motion is to make the stiffness term a complex number. The imaginary part of the number represents the energy dissipation.

The energy dissipation depends on the amplitude of vibration, but unlike viscous damping, if the amplitude is constant the same amount of energy is dissipated in each cycle of the vibration, independent of the frequency. This is consistent with experiments.

Answered by alephzero on January 27, 2021

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