UNIT CONSISTENCY IN NASTRAN
Have you ever wondered why your results look a bit odd sometimes: are those pound forces or pound masses?!... will I get Newtons if I input millimeters?! You complete your analysis only to determine your units were wrong. If so, then this table of consistent units might help you.
| Examples of Consistant Systems of Units for Structural Analysis | |||||||||||
| System of Units | Input | Output | |||||||||
| Length | Force | Elastic Modulus |
Mass | Mass Density |
WTMASS Param |
Acceleration (1 G) |
Disp | Force | Stress | ||
| 1 Metric meter-kg |
m | N | Pa | kg | Kg/m3 | 1.0 | 9.807 | m/sec2 | m | N | Pa |
| 2 Metric mm-ton | mm | N | MPa | t or Mg | t/mm3 or Mg/mm3 |
1.0 | 9807 | mm/sec2 | mm | N | MPa |
| 3 English ft-lb | ft | lbf | psf | slug | slug/ft3 | 1.0 | 32.17 | ft/sec2 | ft | lbf | psf |
| 4 English in-lb (mass) | in | lbf | psi | lbf -sec2/in | lbf -sec2/in4 | 1.0 | 386.1 | in/sec2 | in | lbf | psi |
| 5 English in-lb (force) | in | lbf | psi | lbf | lbf /in3 | 0.00259 | 386.1 | in/sec2 | in | lbf | psi |
NOTE:
t = Metric ton = 1000 kg = 1 Mega gram (Mg)
Jeff Bolognese
February 2008
