FINITE ELEMENT MODEL VALIDITY CHECKS 1.A and 1.B
1.A - Unit Enforced Displacement and Rotation
The Unit Enforced Displacement and Rotation check verifies that no illegal grounding (such as incorrect SPC or MPC)is present in the model. The model should move as a rigid body when it is translated one unit or rotated one radian. This check verifies displacements, element forces, and grid point forces. The check is performed in all three translational and all three rotational directions. This check outputs lots of data. In order to read all the output in an efficient manner, a program called PCHSCAN was written to scan through the punch files of displacement and force results created by NASTRAN. A description of How To Use PCHSCAN is included here for reference .
The displacements results from the three translational subcases should be 1.0 in the input direction and 0.0 in the other five directions. From the rotational subcases, the rotation in the input direction should be 1.0 and the other two rotations should be 0.0. The three translational displacements from the rotational subcases will not be zero. The element forces and grid point force balances should be zero with a maximum of 0.1 lb force and 1.0 in-lb moment. The grid point held should not have other SPC's, and, for best results, should be near the center of gravity of the model.
EXECUTIVE DECK must include the following information:
CASE CONTROL must include the following information:
SPCFORCES=ALL DISP=ALL GPFORCES=ALL ELFORCES=ALL SPC=100
(only for normal plate or solid rotations and the structure must be free at base)
SUBCASE 1 SUBTITLE=UNIT ENFORCED DISP IN X DIRECTION LOAD=100 SUBCASE 2 SUBTITLE=UNIT ENFORCED DISP IN Y DIRECTION LOAD=200 SUBCASE 3 SUBTITLE=UNIT ENFORCED DISP IN Z DIRECTION LOAD=300 SUBCASE 4 SUBTITLE=UNIT ENFORCED ROTA ABOUT X AXIS LOAD=400 SUBCASE 5 SUBTITLE=UNIT ENFORCED ROTA ABOUT Y AXIS LOAD=500 SUBCASE 6 SUBTITLE=UNIT ENFORCED ROTA ABOUT Z AXIS LOAD=600
BULK DATA must include the following information: (The displaced grid is grid point 17104 in this example.)
BEGIN BULK SPCD 100 17104 1 1.0 SPCD 200 17104 2 1.0 SPCD 300 17104 3 1.0 SPCD 400 17104 4 1.0 SPCD 500 17104 5 1.0 SPCD 600 17104 6 1.0 $ SPC FOR UNIT ENFORCED DISP CHECK $23456781234567812345678123456781234567812345678123456781234567812345678 SPC1 100 123456 17104 FORCE 100 17104 0 0.0 1.0 0.0 0.0 FORCE 200 17104 0 0.0 0.0 1.0 0.0 FORCE 300 17104 0 0.0 0.0 0.0 1.0 MOMENT 400 17104 0 0.0 1.0 0.0 0.0 MOMENT 500 17104 0 0.0 0.0 1.0 0.0 MOMENT 600 17104 0 0.0 0.0 0.0 1.0
1.B - Unit Enforced Displacement or Rotation
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