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PROPERTY 
Formula 
Units 
Example 
DENSITY: Mass per unit volume 
= Mass (kg) / Volume (m^{3}) 
kg / m^{3} 
Steel = 7800 
STRENGTH: How much Stress it can
'take' 
= Force (N) / Area (mm^{2}) 
MPa 

HARDNESS: Resistance to indentation or abrasion 
Size or depth of indent 
varies 
HRC55 (Rockwell) etc 
STIFFNESS: How much Stress for a
certain Strain 
= Stress (MPa) / Strain 
MPa 
1020 Steel E = 205GPa 
TOUGHNESS: Energy to break 
= Area under StressStrain curve 
J / m^{2} 
Charpy Test (Joules) 
ELASTICITY: Ability to Stretch with plasticity 
= Strain at yield 
% 
1020 Steel: 0.01% @ yield 
PLASTICITY: Permanent deformation: 
= (L2  L1) / L1 
% 
1020 Steel: 25% 
POISSON'S RATIO: side strain to axial strain 
v = ex / ey 
 
1020 Steel v = 0.29 
DEFINE > 
Formula> 
Units> 
Diagram> 
Axial Stress (Tension or Compression) 
Stress = Force / Area 
MPa 

Axial Strain (Tension or Compression) 
Strain = extension / original Length 
 

Shear Stress 
Stress = Force / Area 
MPa 

Modulus of Elasticity (Young's Mod) 
E = Stress / Strain 
GPa 
Slope of Stress:Strain diagram 
Modulus of Rigidity (Shear Mod.) =~ 0.4E 
G = S. Stress / S. Strain 
GPa 
Slope of S.Stress:S.Strain diagram 
Shear Strain 
Strain = movement / original Depth 
 

Shear in Detail: Shear Strain is usually small enough to ignore the changes in L with angle. Angle is in radians. Area is the zone that would slide apart assuming it broke in shear. 
Find Force for the 3 modes of failure  lowest force is critical
Typically, electrode 41** are 410MPa. Take 410 / 3 = 136.7MPa
Hint: Pipes are simply cylinders with pure hoop stress.
Find M and I, the rest is a simple equation...