step:
  - mech:
      dot_F: [1.0e-3,0,0,  0,x,0,  0,0,x]
      P:     [     x,x,x,  x,0,x,  x,x,0]
    discretization:
      t: 10
      N: 40
      f_out: 4
  - mech:
      dot_F: [1.0e-3,0,0,  0,x,0,  0,0,x]
      P:     [     x,x,x,  x,0,x,  x,x,0]
    discretization:
      t: 60
      N: 60
      f_out: 4