Duffing Forced Damped Harmonic Oscillator

Clear[x]
duffing = x''[t] + 2*g*x'[t] + x[t] + x[t]^3 - f*Cos[w*t]

                                3
     -(f Cos[t w]) + x[t] + x[t]  + 2 g x'[t] + x''[t]

ans = NDSolve[{duffing ==0/.{g->1/10,f->20,w->1.45},x[0]==0,x'[0]==4},x,{t,0,200},MaxSteps->3000]

NDSolve::mxst: Maximum number of 3000 steps reached at the point t == 82.0993.

     {{x -> InterpolatingFunction[{{0., 82.0993}}, <>]}}

Plot[x[t]/.ans,{t,0,60}];

x = x[t]/.ans
v = D[x[t]/.ans, t]

     {InterpolatingFunction[{{0., 82.0993}}, <>][t]}

     {InterpolatingFunction[{{0., 82.0993}}, <>][t]}

Plot[x,{t,0,60}];

Plot[v,{t,0,60}];

ParametricPlot[{x[[1]],v[[1]]}, {t,0,60}];