Ken Youssefi PDM I, SJSU 1 Materials - Metals
Dec 28, 2015
Ken Youssefi PDM I, SJSU 2
Material Selection
Function
Material Shape
Process
Material selection and process cannot be separated from the shape and the function of the product, two way interaction.
Function dictates the choice of material and shape.
Process interacts with shape.
Process is influenced by material
Shape restricts the choice of material and process.
Ken Youssefi PDM I, SJSU 3
Engineering Materials
Materials
Metals Plastics
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
Materials
Metals PlasticsCeramics
Glass
Carbides
Nitrides
Graphite
Diamond
Glasses
Glass ceramics
Composites
Reinforced plastics
Metal-Matrix
Ceramic-Matrix
Laminates
Ken Youssefi PDM I, SJSU 5
Properties of Materials
Properties of Materials
Mechanical Properties
Yield strength
Ultimate strength
Ductility
Hardness
Toughness
Fatigue (cyclic load)
Creep (temp / time)
Physical & chemicalProperties
Thermal conductivity
Thermal expansion
Electrical conductivity
Magnetic properties
Corrosion
Density
Melting point
Ken Youssefi PDM I, SJSU 6
Material StrengthStandard Tensile Test
Standard Specimen
Ductile Steel (low carbon)
Sy – yield strength
Su – fracture strength
σ (stress) = Load / Area
ε (strain) = (change in length) / (original length)
Ken Youssefi PDM I, SJSU 9
• - 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
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 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 12
Relative mechanical properties of various materials at room temp. in decreasing order.
Ken Youssefi PDM I, SJSU 13
MetalsThe most common material used in design, most of the elements in the periodic table are metals.
• Conduct electricity and heat.
• Have relatively high melting point, some metal alloys can withstand temp. up to 2200 oC.
• Metals can be joined in many different ways.
• Metals are ductile, they can be shaped by extrusion (hot or cold), rolling, forging and drawing.
• Metals are easy to machine with precision.
• Metals are strong, stiff, and tough.
• They can be made stronger by alloying and heat treatment.
• Metals are vulnerable to corrosion.
• Metals are heavy.