Hi,

some time ago, there was a discussion about linear elastic behavior in multistep analyses. There's still one case I'd like to clarify, though. Specifically, the vibrating cable simulation from the "Introduction to Abaqus/Standard and Abaqus/Explicit" course:

The .inp syntax for this example is:

*STEP, NLGEOM
STEP 1: STRETCH CABLE
*STATIC
*CLOAD
13, 1, 500.
*RESTART, WRITE
*NODE FILE
U
*EL PRINT
S, MISES, E
*NODE PRINT
U, RF, CF
*END STEP
**
*STEP, NLGEOM
STEP 2: DEFLECT MIDPOINT
*STATIC
.1, 1.
*BOUNDARY, OP=MOD
7, 2, 2, -1.
*END STEP
**
*STEP, NLGEOM, INC=200
STEP 3:RELEASE & SEE VIBRATE
*DYNAMIC
.0002, .04
*BOUNDARY, OP=NEW
1, 1, 2
13, 2
*PRINT, FREQUENCY=100
*EL PRINT, FREQUENCY=0
*NODE PRINT, FREQUENCY=0
*END STEP

Here's how I interpret it:
- step 1 - the cable is stretched by force applied to its end
- step 2 - a separate static linear elastic problem is solved from scratch (from initial undeformed shape) with the stretching force still included (propagated by default from the previous step) and an additional prescribed BC deflecting the center node
- step 3 - a separate dynamic linear elastic problem is solved from scratch (from initial undeformed shape), taking into account the stretching force (still propagated) and the released BC at the center node (replaced by equivalent forces removed with the default amplitude for the *DYNAMIC step and thus immediately at the start of the step)

Is that correct, or does it work differently for dynamic analyses? If it's true, then solving each step separately with appropriate loads/BCs should provide the same result since there's no path dependence here, right?

Also, why do I still see the state from the previous step in the initial frame of the subsequent step then? Because that t=0 frame actually shows the result from the previous step, even though Abaqus will solve a separate elasticity problem?
 

Here's the complete input deck if someone wants to give it a try:

*NODE
1, 0.0, 0.0
3, 40.0, 0.0
5, 80.0, 0.0
6, 100.0, 0.0
7, 120.0, 0.0
9, 160.0, 0.0
11, 200.0, 0.0
*NSET, NSET=END
11,
*ELEMENT, TYPE=B21, ELSET=BEAMS
1, 1, 3
2, 3, 5
3, 5, 6
4, 6, 7
5, 7, 9
6, 9, 11
*BEAM SECTION, SECTION=CIRC, ELSET=BEAMS, MATERIAL=MAT1
1.0
*MATERIAL, NAME=MAT1
*DENSITY
8e-9
*ELASTIC
2.0E5, 0.3
*BOUNDARY
1, 1, 2
1, 6, 6
11, 2, 2
********************************************************
*STEP, NLGEOM
STEP 1: STRETCH CABLE
*STATIC
*CLOAD
11, 1, 5000.
*RESTART, WRITE
*NODE FILE
U
*EL PRINT
S, MISES, E
*NODE PRINT
U, RF, CF
*END STEP
****************************************
*STEP, NLGEOM
STEP 2: DEFLECT MIDPOINT
*STATIC
.1, 1.
*BOUNDARY, OP=MOD
6, 2, 2, -1.
*END STEP
****************************************
*STEP, NLGEOM, INC=200
STEP 3:RELEASE & SEE VIBRATE
*DYNAMIC
.0002, .04
*BOUNDARY, OP=NEW
1, 1, 2
11, 2
*PRINT, FREQUENCY=100
*EL PRINT, FREQUENCY=0
*NODE PRINT, FREQUENCY=0
*END STEP