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Coulomb damping. (English) Zbl 1260.97008

Summary: Viscous damping is commonly discussed in beginning differential equations and physics texts but dry friction or Coulomb friction is not despite dry friction being encountered in many physical applications. One reason for avoiding this topic is that the equations involve a jump discontinuity in the damping term. In this article, we adopt an energy approach which permits a general discussion on how to investigate trajectories for second-order differential equations representing mechanical vibration models having dry friction. This approach is suitable for classroom discussion and computer laboratory investigation in beginning courses, hence introduction of dry friction need not be delayed for more advanced courses in mechanics or modelling. Our method is applied to a harmonic oscillator example and a pendulum model. One advantage of this method is that the values of the maximum deflections of a solution can be calculated without solving the differential equation either analytically or numerically, a technique that depends on only the initial conditions.

MSC:

97M50 Physics, astronomy, technology, engineering (aspects of mathematics education)
97I70 Functional equations (educational aspects)
34C15 Nonlinear oscillations and coupled oscillators for ordinary differential equations
70E18 Motion of a rigid body in contact with a solid surface
70E17 Motion of a rigid body with a fixed point

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Mathematica
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References:

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