Properties of Materials

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

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

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.

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

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

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

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

Engineering Materials Basic Categories Metals Plastics Ceramics Composites

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.

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.

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   1020 (plain carbon steel, hot-rolled or cold-drawn) 1040 (plain carbon steel, hot-rolled or cold-drawn) 4140 (heat-treated alloy steel, chromium-molybdenum) 4340 (heat-treated alloy steel, nickel-chromium-molybdenum) S30400 (stainless steel) S316 (stainless steel) O1 (tool steel) ASTM20-60 (gray cast iron) Ken Youssefi SJSU, ME dept.

Steel sheet and standard shapes

Working with steel

Cast Iron

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.

Aluminum

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

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

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.

PVC and ABS

Polystyrene

Nylon and Kevlar (related polymer)

Ceramics

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

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

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

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

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