The target time step is reduced to Δttarg = 0.001 increasing the natural frequency for the column and resulting in ca. 1000 steps for the ramp for load case 1.

 

 

The results are visualized by plotting the high definition history data for global energy and points output in files mech_001_2d_Case1c_000.hdh and mech_001_2d_Case1c_001.hdh respectively.   This data can be pasted into excel workbook mech_001.xls.

 

Increasing the number of time steps by decreasing the critical time step has two effects:

1The solution is much closer to the quasi static target of a linear ramp followed by constant displacement.

2The vibration frequency, which is dependent on the scaled mass, is increased.  This is clearly seen in the frequency of the oscillations between time t=1.0 and t=2.0 when the load is constant.

The stress at the base of the column (Point 1) now increases systematically with the stress at Point 2 and much smaller magnitude oscillations occur between time t=1.0 and t=2.0.

Similarly, the global energy exhibits oscillatory response with higher frequency and lower magnitude between time t=1.0 and t=2.0 than for Case 1B.