MECHANICAL ENGINEERING FUNDAMENTALS Course Code : ME-2112 By: Engr. Hassaan Bin Younis

Classification of Materials Materials used in the design and manufacture of products Plastics Wood Composites Ceramics Metals Fabrics Layers of polycarbonate, aluminium & acrylic Tungsten carbide tool bit Linen, cotton, nylon, Kevlar Steel, aluminium Balsa wood model Acrylic lens

Mechanical Properties Strength: The ability of a material to resist externally applied force Stiffness: The ability of a material to resist deformation under stress. The modulus of elasticity is the measure of stiffness Elasticity: It is the property of a material to regain its original shape after deformation when the external forces are removed Steel is more elastic than rubber. Plasticity: It is property of a material which retains the deformation produced under load permanently.

Mechanical Properties Ductility: Ability to deform under tensile stress It is the property of a material enabling it to be drawn into wire with the application of a tensile force The ductility is usually measured by the terms, percentage elongation and percentage reduction in area. Brittleness: It is the property of a material opposite to ductility It is the property of breaking of a material with little permanent distortion Toughness: It is the property of a material to resist fracture due to high impact loads like hammer blows. This property is desirable in parts subjected to shock and impact loads.

Mechanical Properties Resiliance: It is the property of a material to absorb energy and to resist shock and impact loads. This property is essential for spring materials. Creep: When a part is subjected to a constant stress at high temperature for a long period of time, it will undergo a slow and permanent deformation called creep Fatigue: When a material is subjected to repeated stresses, it fails at stresses below the yield point stresses The failure is caused by means of a progressive crack formation which are usually fine and of microscopic size Hardness: It is the ability of a metal to cut another metal.

Backelite, durite, plaskon Plastics 1.Synthetic materials 2. Mould into desired shape under pressure and heat 3.Can be cast, rolled, laminate, machined Thermosetting Backelite, durite, plaskon Plastics Thermoplastic PVC, Celluloid

Classification of Materials (Plastics) Plastics can be further classified as; Thermoplastic Thermoset Elastomers Thermoplastics Thermosets Elastomers Acrylics Epoxy resins Rubbers Nylons Phenolic Silicones PVC Polyesters Polyurethanes Polyethylene Phenol formaldehyde Urea formaldehyde PVC gutters Polyethylene Rubber Rubber

Classification of Materials (Composites) A composite is a combination of two or more chemically distinct materials whose physical characteristics are superior to its constituents acting independently. Because of their high strength/stiffness to weight ratio they are widely used in the; Aerospace industry Offshore structures Boats Sporting goods

Classification of Materials (Composites) Examples of composites include; Reinforced Plastics Ceramic-matrix Metal-Matrix Cylinder linings Outer skin panels & fuselage A380 Kevlar, taffeta polyester sails Cylinder linings Carbon reinforced plastic Combustion chamber of jet engine Glass reinforced plastic hull Thrust chamber for rocket

Classification of Materials (Ceramics) Oxides (alumina – insulation and abrasives, zirconia – dies for metal extrusion and abrasives) Carbides (tungsten-carbide tools) Nitrides (cubic boron nitride, 2nd in hardness to diamond)

Classification of Materials (Metals) Metals can be further classified as Ferrous & Non-Ferrous, some examples include; Ferrous Non-Ferrous Steels Aluminium Stainless Steels Copper High Speed Steels Brass Cast Irons Titanium High Speed steel Stainless Steel Aluminium Copper Brass

Cast Iron Carbon ------ 1.7 per cent to 4.5 percent small amounts of silicon, manganese, phosphorous and sulphur Brittle (can’t be used for machine parts subjected to shocks) Low cost Good casting Valuable material for Excellent machinability engineering purpose High compressive strength

Purest form of iron (contains up to 99.9%) Tough Malleable Ductile Wrought Iron Purest form of iron (contains up to 99.9%) Tough Malleable Ductile

Steel Alloy of iron and carbon (Carbon up to 1.5%) Carbon has the ability to increase hardness and strength 1. Dead mild steel — up to 0.15% carbon 2. Low carbon or mild steel — 0.15% to 0.45% carbon 3. Medium carbon steel — 0.45% to 0.8% carbon 4. High carbon steel — 0.8% to 1.5% carbon

Stainless Steel Correctly heat treated Finished Resist corrosive attack from corrosive media

Non-Ferrous metals Ease of fabrication (casting, rolling, welding, machining) Resistance to corrosion Electrical and thermal conductivity Weight

Aluminium Melting point 658 o C Weak and soft in pure form Good thermal conductivity (widely used in overhead cables) High resistance to corrosion and non toxic (Cooking utensils, thin coil used for wrapping food items) Light weight (used in aircraft and automobiles)

Copper Melting point 1083 o C One of the most widely used in industry Soft , malleable, ductile Good conductor of electricity (Electric Cables) Used in making coins, house hold utensils, electroplating

Lead Melting point 326 o C Bluish grey metal Soft enough to be cut by knife Extensively used for making solders Coting of electric cables

Tin Brightly shining white metal Soft, Malleable, Ductile Used for protective coating of iron and steel sheets Foil used as moisture proof packing

Low density Low cost Flexible Resistance to heat and electricity Non-Metallic Low density Low cost Flexible Resistance to heat and electricity

Rubber 1.Natural materials 2. Soft rubber is used for insulation 3.Used for Power transmission belts

Leather 1.It is very much flexible 2.Can withstand considerable wear under suitable conditions 3.Used in power transmission belts , washers, packing