Principles of Engineering

Properties of Materials

Metals Dense Conduct Electricity Lustrous Conducts Heat Ductility Malleability High Melting Point and Boiling Point	Non-Metals Does not conduct Electricity Low Melting Point and Boiling Point

Types of Properties

• Chemical -
• Magnetic - ferrous metals; ability to be attracted by magnets
• Electrical - Resistivity & Conductivity
• Physical -
  • Melting Point - solid to liquid
  • Density - Mass per unit volumn (m/V)
  • Specific Gravity - Ration of mass to mass of an equal volume of water
  • Curie Point - where magnetization by outside forces is no longer possible
  • Refractive Index - Ratio of velocity of light to velocity of light in a vacuum
  • Thermal Conductivity - Rate of heat flow
  • Thermal Resistivity
  • Thermal Expansion - Rate of elongation
  • Heta Distortion Temperature -
  • Water Absorption -
  • Dielectric Strength -
  • Specific Heat -
  • Poisson's Ratio -

Mechanical - describes material when a force is applied to it

Common Variable Names:

• ∆ = the change in

• d = total deformation

• σ = stress (force per unit area)

• Î = strain

• E = modulus of elasticity, Young’s Modulus

• P = axial force

• A = cross section area

• L = length

• r = radius of a circle

• d = diameter of a circle

• Press = Pressure

 Formulae:

• σ = P/A

• Î= d/L

• d= PL/AE

• E= σ/Î

• A=Pr² (area of circle when using the radius)

• A= .7854d² (area of circle when using the diameter)

• Press = P/A

• Hooke’s Law:  s/e=constant

Mechanical Properties:

• •Tensile Strength – Ratio of maximum load to original cross-sectional area
• Yield Strength – Stress at which a material deviates a specified amount from Hooke’s Law
• Compressive Strength – Maximum withstandable compressive stress
• Flexural Strength – Outer fiber stress when a beam is loaded and deflected to a certain strain value
• Shear Strength – Stress required to fracture
• Percent Elongation – Increase in gage length after fracture
• Percent Reduction in Area – Difference between original cross-sectional area and minimum cross-sectional area after fracture
• Hardness – Resistance to plastic deformation
• Impact Strength – Energy required to fracture a given volume
• Endurance Limit – Maximum stress below which a material maintains elasticity
• •Creep Strength – Constant stress that causes a set quantity of creep in a given time (temperature constant)

  Creep – Permanent strain
• Stress Rupture Strength – Nominal stress in a tension test at fracture