1. Properties of Materials

2. Bulk mechanical properties
Stiffness
Strength
Elasticity
Ductility
Brittleness
Malleability
Toughness
Resilience
Hardness

3. Ductility
Characteristic of a material that undergoes considerable plastic deformation under tensile load before rupture
Ductility – characteristic of a material that undergoes considerable plastic deformation under tensile load before rupture
Can be drawn into a long thin wire by a tensile force without failure
Quantified by % elongation (gage length/original gage length) and % reduction in area (area/original area)
High %elongation is high ductile material

4. Brittleness Absence of any plastic deformation prior to failure
Fails suddenly without warning
No yield point or necking
Rupture strength = ultimate strength
Brittle materials typically weak in tension and thus, tested in compression
Do not confuse brittle and ductile with strength.

5. Malleability
Characteristic of a material that undergoes considerable plastic deformation under compressive load before rupture. It can be hammered into shapes.
characteristic of a material that undergoes considerable plastic deformation under compressive load before rupture
Ductile materials are often malleable

6. Resilience
Characteristic of a material that springs back into shape; elasticity.
Property of a material enabling it to endure high impact loads without inducing a stress in excess of the elastic limit
Energy is absorbed during blow is stored and recovered when body is unloaded
Measured by area under elastic portion of curve
Resilience – measure of energy absorbed by a material and returned when load is removed; materials that quickly return to their original shape are called resilient

7. Toughness
A combination of strength and ductility. Can absorb lots of punishment without breaking in two.
Toughness – property of a material enabling it to endure high-impact or shock loads; ability to absorb energy during plastic deformation; measure of the capacity of a material to sustain permanent deformation
If material can be highly stressed & greatly deformed without rupture, it is tough
Area under the curve (1 tougher than 2)
Brittle materials are not very tough (small plastic deformation before fracture occurs)
Fracture toughness – resistance to rapid propagation of crack because of available energy

8. Hardness Resistance of a material to scratching, wear, or penetration
Measured by a compression test
Not frequently used for biological tissues

10. Engineering Materials Basic Categories
Metals
Plastics
Ceramics
Composites

11. Engineering Materials
Plastics
Metals
Steel
Stainless steel
Die & tool steel
Cast iron
Ferrous
Non-ferrous
Aluminum
Copper
Zinc
Titanium
Tungsten
Thermoplastics
Acrylic
Nylon
ABS
Polyethylene
Polycarbonate
PVC
Thermosets
Phenolic
Polymide
Epoxies
Polyester
Elastomers
Rubber
Polyurethane
Silicone
Ken Youssefi
SJSU, ME dept.

12. Engineering Materials
Composites
Reinforced plastics
Metal-Matrix
Ceramic-Matrix
Laminates
Ceramics
Glass
Carbides
Nitrides
Graphite
Diamond
Glasses
Glass ceramics
Metals
Plastics
Ken Youssefi
SJSU, ME dept.

13. Most Commonly Used Materials
The following 25 materials are the most commonly used materials in the design of mechanical products; in themselves they represent the broad range of other materials.
Steel and Cast Iron
(plain carbon steel, hot-rolled or cold-drawn)
(plain carbon steel, hot-rolled or cold-drawn)
(heat-treated alloy steel, chromium-molybdenum)
(heat-treated alloy steel, nickel-chromium-molybdenum)
S (stainless steel)
S (stainless steel)
O1 (tool steel)
ASTM (gray cast iron)
Ken Youssefi
SJSU, ME dept.

14. Steel sheet and standard shapes

15. Working with steel

16. Cast Iron

17. Most Commonly Used Materials
Aluminum and Copper Alloys
2024 (aluminum, O, T3, T4 or T6)
3003 (aluminum, H12 or H16)
6061 (aluminum, T6)
7075 (aluminum, T6)
C268 (copper)
Other metals
Titanium 6-4
AZ63A (magnesium)
Ken Youssefi
SJSU, ME dept.

18. Aluminum

19. Working with Aluminum Inert gas welding TIG welding
TIG = tungsten inert gas
Non-consumable rod is tungsten
Inert gas is argon or helium
Filler rod depends on what you’re welding

20. MIG welding uses a continuous wire feed
MIG = metal inert gas

21. Most Commonly Used Materials
Plastics
ABS
Polycarbonate
Nylon 6/6
Polypropylene
Polystyrene
Ceramics
Alumina
Graphite
Composite materials
Douglas fir
Fiberglass
Graphite/epoxy
Ken Youssefi
SJSU, ME dept.

22. PVC and ABS

23. Polystyrene

24. Nylon
and Kevlar (related polymer)

25. Ceramics

26. Properties of Most Commonly Used Materials
Ultimate Strength in tension
Ken Youssefi
SJSU, ME dept.

27. Properties of Most Commonly used Materials
Yield strength
Ken Youssefi
SJSU, ME dept.

28. Properties of Most Commonly used Materials
Fatigue Limit (strength under cyclic loading)
Ken Youssefi
SJSU, ME dept.

29. Properties of Most Commonly used Materials
Density
Ken Youssefi
SJSU, ME dept.

30. Cost of Most Commonly used Materials
Ken Youssefi
SJSU, ME dept.