An oscillator with Duffing-type hardening restoring force is damped by dry friction. Compute the time history of the free motion by numerically
integrating the equations of motion. First use a linearized restoring force and
compare the results with those obtained in Example 20.1; then repeat the study
using the fully nonlinear equation.
Data mass m = 1 kg, linear stiffness k = 100 kN/m; nonlinear parameter
μ = 500 1/m2, friction force F = 40 N. Initial conditions: x0 = 100 mm, v0 = 0.