Ken YoussefiPDM I, SJSU 1 Materials - Metals. Ken YoussefiPDM I, SJSU 2 Material Selection Function MaterialShape Process Material selection and process.

Ken Youssefi PDM I, SJSU 1

Materials - Metals

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 7

Material StrengthDifferent grade of steel Plastics

Ken Youssefi PDM I, SJSU 8

Website: www.ge.com/plastics

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 11

Mechanical properties of Various Materials at room Temp.

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.