Week - 1 - Consistency of Units

Introduction

A unit of measurement is a definite magnitude of a quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same kind of quantity. For example, a length is a physical quantity. A meter is a unit of length that represents a definite predetermined length. When we say 10 meters (or 10 m), we actually mean 10 times the definite predetermined length called "meter". In simulation software like ANSYS, ABAQUS units are predefined and hence users need to just select and use it. LS Dyna doesn't have a predefined unit system. Hence it is necessary for the users to provide units based upon the industrial standards and requirements. This study is mainly focused on the unit and its conversion.

Conversion of kg/m/s to gm/mm/ms

Mass

1kg=1000g

Length

1m=1000mm

Seconds

1s=1000ms

Force

1N= 1 kg.m/s2=(1000*1000)/(1000*1000)g.mm/ms2= 1 g.mm/ms2

Stress

Stress=force/area= N/m2=(g.mm/ms2)/(10^6mm2)=10^-6 (g/mm.ms2)

Energy

Energy= force*distance= (g.mm/ms2)*(1000mm)= 1000(g.mm2/ms2)

Density

Density=mass/volume= kg/m3= (1000g)/(10^9 mm3)=10^-6(g/mm3)

youngs modulus

The unit of youngs modulus is similar to stress which is 10^-6 (g/mm.ms2)

Given E=210*10^9 pa

hence 210*10^9*10^-6 (g/mm.ms2)=210*10^3(g/mm.ms2)

Velocity

Velocity(km/hr)=(1000/3600)m/s=0.278m/s

given V=56.33km/hr=(56.33*0.278*1000mm)/(1000ms)=15.65(mm/ms)

Gravity

Gravity=m/s2=(1000mm)/(10^6)ms2=10^-3(mm/ms2)

g=9.81m/s2=9.81*10^-3(mm/ms2)

The above table is created by using excel software

Conclusion:

This work is about different types of unit and its conversion