1. Materials - Metals
Ken Youssefi
PDM I, SJSU

2. Material Selection Function Material Shape Process
Function dictates the choice of material and shape.
Shape restricts the choice of material and process.
Function
Material
Shape
Process
Process is influenced by material
Process interacts with shape.
Material selection and process cannot be separated from the shape and the function of the product, two way interaction.
Ken Youssefi
PDM I, SJSU

3. 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
PDM I, SJSU

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

5. Properties of Materials
Mechanical Properties
Yield strength
Ultimate strength
Ductility
Hardness
Toughness
Fatigue (cyclic load)
Creep (temp / time)
Physical & chemical
Properties
Thermal conductivity
Thermal expansion
Electrical conductivity
Magnetic properties
Corrosion
Density
Melting point
Ken Youssefi
PDM I, SJSU

6. Material Strength Standard Tensile Test σ (stress) = Load / Area
Ductile Steel (low carbon)
Sy – yield strength
Su – fracture strength
Standard Specimen
σ (stress) = Load / Area
ε (strain) = (change in length) / (original length)
Ken Youssefi
PDM I, SJSU

7. Material Strength Different grade of steel Plastics Ken Youssefi
PDM I, SJSU

8. Website: www.ge.com/plastics
Ken Youssefi
PDM I, SJSU

9. Common Mechanical Properties
– the highest stress a material can withstand and still return exactly to its original size when unloaded.
Yield Strength (Sy)
- the greatest stress a material can withstand, fracture stress.
Ultimate Strength (Su)
- the slope of the straight portion of the stress-strain curve.
Modulus of elasticity (E)
- the extent of plastic deformation that a material undergoes before fracture, measured as a percent elongation of a material.
% elongation = (final length, at fracture – original length) / original length
Ductility
- the capacity of a material to absorb energy within the elastic zone (area under the stress-strain curve in the elastic zone)
Resilience
- the total capacity of a material to absorb energy without fracture (total area under the stress-strain curve in the elastic zone)
Toughness
Ken Youssefi
PDM I, SJSU

10. Mechanical Properties
Brittle material
Brittle material
Brittle material
Brittle material
Ken Youssefi
PDM I, SJSU

11. Mechanical properties of Various Materials at room Temp.
Ken Youssefi
PDM I, SJSU

12. Relative mechanical properties of various materials at room temp
Relative mechanical properties of various materials at room temp. in decreasing order.
Ken Youssefi
PDM I, SJSU

13. Metals Metals are strong, stiff, and tough.
The most common material used in design, most of the elements in the periodic table are metals.
Metals are strong, stiff, and tough.
They can be made stronger by alloying and heat treatment.
Metals are ductile, they can be shaped by extrusion (hot or cold), rolling, forging and drawing.
Metals are easy to machine with precision.
Have relatively high melting point, some metal alloys can withstand temp. up to 2200 oC.
Conduct electricity and heat.
Metals can be joined in many different ways.
Metals are vulnerable to corrosion.
Metals are heavy.
Ken Youssefi
PDM I, SJSU