Unit consistency for finite element analysis Ditho Ardiansyah Pulungan December 4, 2014 Abstract In finite element analysis, units are not important in general. Numbers are just numbers. The finite element program does not care which unit you are using. They just simply use the number you input and calculate based on the value you entered. Therefore, we need to use consistent units for all the variables such as length, elastic constants E, density, etc. For example, when we create finite element geometry by assuming that all geometric dimensions that we input are in meter (m), the elasticity constant also need to be input as N/m 2 . Mass Length Time Stress Force Density Young’s modulus Velocity Gravity 1 kg 1m 1s Pa N kg m -3 1 μg 1 μm 1 ms 10 3 Pa 10 -9 N 10 9 kg m -3 1.7 × 10 6 (1.7 GPa) 1 mg 1 μm 1 ms 10 3 Pa 10 -9 N 10 9 kg m -3 1.7 × 10 6 (1.7 GPa) 1g 1 μm 1 ms 10 9 Pa 10 -3 N 10 15 kg m -3 1.7 (1.7 GPa) 1g 1 μm 1s 10 3 Pa 10 -9 N 10 15 kg m -3 1.7 × 10 6 (1.7 GPa) 1
How to convert units for FEM analysis consistently
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Unit consistency for finite element analysis
Ditho Ardiansyah Pulungan
December 4, 2014
AbstractIn finite element analysis, units are not important in
general. Numbers are just numbers. The finite element program does
not care
which unit you are using. They just simply use the number you
input and calculate based on the value you entered. Therefore,
weneed to use consistent units for all the variables such as
length, elastic constants E, density, etc. For example, when we
create finiteelement geometry by assuming that all geometric
dimensions that we input are in meter (m), the elasticity constant
also need to beinput as N/m2.
Mass Length Time Stress Force Density Youngs modulus Velocity
Gravity
1 kg 1 m 1 s Pa N kg m3
1 g 1 m 1 ms 103 Pa 109 N 109 kg m3 1.7 106 (1.7 GPa)
1 mg 1 m 1 ms 103 Pa 109 N 109 kg m3 1.7 106 (1.7 GPa)
1 g 1 m 1 ms 109 Pa 103 N 1015 kg m3 1.7 (1.7 GPa)
1 g 1 m 1 s 103 Pa 109 N 1015 kg m3 1.7 106 (1.7 GPa)
