Week - 1 - Consistency of Units
Abstract
LS-DYNA doesn't have a default system of units. User needs to input material properties and physical dimensions according to a consistent system of units as per their choice. This warrants that to use LS-DYNA in different circumstances, users have to be conversant with converting quantities from one system of units to another.
we see the different conversion unit
|
SI Unit System (kg,m,s) |
Conversion (g,mm,ms) |
|
MASS 1kg |
1000g |
|
LENGTH 1m |
1000mm |
|
TIME 1s |
1000ms |
|
FORCE 1N |
1N= 1Mass*1 acceleration =(1000g*1000mm)/(1000ms)^2 =1 g mm/ms^2 |
|
STRESS 1Pa |
1 pa =1N/1M^2 ((1000g*1000mm)/(1000ms)^2)/(1000 mm)^2 1000g/(1000)^2ms^2*1000mm =1*10^-6g/ms^2mm =Conversion factor is 10^-6 |
|
ENERGY 1Nm |
1 JOULE=1N*1M 1N=1g mm/ms^2 =10^9 mm2*10^-6ms^2 =10^3 g mm2/ms^2 =Conversion factor is 10^3 |
|
DENSITY 1Kg/m3 |
=1000g/(1000mm)^3 10^-6 g/(mm^2) =Conversion factor is 10^-6 |
|
YOUNG'S Modulus 210GPa |
1 Gpa=1*10^3g/ms^2mm 210*10^3 g/(mm*m s^2) =Conversion factor is 10^-3 |
|
Velocity 56.33KMPH |
velocity = Km/H 1km=10^6 mm 1 hrs=60 min 1 min=60 sec 56.33KMPH= 56.33*0.277 ans= 15.60 Mm/Ms Conversion factor is 1 |
|
GRAVITY 9.8m/s2 |
gravity=M/s^2 =1000 mm/(1000ms)^2 =9.8*10^-3 mm/ms^2 Conversion factor is 1 Conversion factors = 1 |
|
SI Unit System |
Kg,cm,ms |
Kg,cm,s |
gm mm ms |
kg m s |
g cm s |
g,cm,us |
g mm s |
ton mm s |
slug ft s |
kg mm s |
g cm ms |
kg mm ms |
|
MASS |
1kg |
1kg |
10^3 g |
1 kg |
10^3 g |
10^3 g |
10^3 g |
10^-3 Tony |
0.068 slug |
1kg |
10^3 g |
1kg |
|
LENGTH |
10^2 cm |
10^2 cm |
10^3 mm |
1m |
10^2 cm |
10^2 cm |
10^3 mm |
10^3 mm |
3.28 ft |
10^3 mm |
10^2mm |
10^3 mm |
|
TIME |
10^3 ms |
1s |
10^3 ms |
1s |
1s |
10^6 us |
1s |
1s |
1s |
1s |
10^3ms |
10^3ms |
|
FORCE |
10^-4 kg ms^2 |
10^2 kg*cm/s^2 |
1*g mm/ms^2 |
1*kg m/s^2 |
10^5*g cm/s^2 |
10^-7 g *cm/ us^2 |
10^6 g *mm/ s^2 |
1 ton*mm/s^2 |
0.2246 slug*ft/s^2 |
10^3 kg*mm/s^2 |
10^-1g*cm/ms^2 |
10^-3kg*mm/ms^2 |
|
STRESS |
10^-8 kg/(cm*ms^2) |
10^-2 kg/(cm*s^2) |
10^-6 g/(mm*ms^2) |
Kg/m*s^2 |
10*g cm/s^2 |
10^-11 g /(cm*us^2) |
1g /(mm* s^2) |
10^-6 Tonn/(mm*s^2) |
0.0208 slug/(ft*s^2) |
10^ -3 kg/mm *s^2 |
10^ -5 g/cm *ms^2 |
10^ -9 kg/(mm *ms^2) |
|
ENERGY |
10^-2 kg*cm^2/ms^2 |
10^4 kg*cm^2/s^2 |
10^3 g*mm^2/ms^2 |
Kg/m^2/s^2 |
10^7*g cm^2/s^2 |
10^-5 g*cm^2*/us^2 |
10^9 g*mm*/ s^2 |
10^3 ton*mm^2/s^2 |
0.7366 slug*ft^2*/s^2) |
10^ 6 kg*mm^2 /s^2 |
10 g*cm^2 /ms^2 |
1 kg*mm^2 /ms^2 |
|
DENSITY |
10^-6 kg/cm^3 |
10^-6 kg/cm^3 |
10^-6 g/mm^3 |
Kg/m^3 |
10^ -3*g cm^3 |
10^-3 g /(cm^3) |
10^-6 g /mm^3 |
10^ -12 ton*mm^3 |
1.93*10^-3 slug/ft^3 |
10^ -9 kg/mm^3 |
10^ -3 g/cm^3 |
10^ -9 kg/mm^3 |
|
YOUNG'S Modulus 210GPa |
2100kg/(cm*ms^3) |
210*e^7 kg/(cm*s^2) |
210*e^3 g/(mm*ms^2) |
210*e^9 kg/ms^2 |
210*e^10 g/(cm*s^2) |
2.10 g/cm*us^2 |
2.10e^11 g/mm*s^2 |
2.10e^3 ton/(mm*s^3) |
4.368e^9slug/(ft*s^2) |
2.10e^6 kg/(mm*s^2) |
2.10e^4 g/(cm*ms^2) |
210 kg/(mm*ms^2) |
|
Velocity 56.33KMPH |
1.5647 cm/ms |
1.5647 cm/s |
15.647 mm/ms |
15.647 m/s |
1564.7 m/s |
15.647*10^-4 cm/us |
15647 mm/s |
15647 mm/s |
51.322 ft/s |
15647 mm/s |
1.5647 cm/ms |
15.647 mm/ms |
|
GRAVITY |
9.8*10^-4 cm/ms^2 |
9.8*10^2 cm/s^2 |
9.8*10^-3 mm/ms^2 |
9.8*m/s^2 |
9.8*10^-3mm/ms^3 |
9.8*10^-10 cm/us^2 |
9.8*10^3 mm/s^2 |
9.8*10^3 mm/s^2 |
32.144 ft/s^2 |
9.8*10^3 mm/s^2 |
9.8*10^-4 cm/ms^2 |
9.8*10^3 mm/ms^2 |
conclusion
Different industries use different system of units as per their convenience. The units for the basic measurement quantities, mass distance and time - dictate how the other derived quantities will be expressed. For example, automotive industries use kg,mm,ms as their standard unit system. Construction industries are likely to use tonne,m,s as their unit system. Similarly, PCB simulation in electronic industry uses gm, micrometer,ms as their system of units.