Page 52 - CITS - WCS - Mechanical

WORKSHOP SCIENCE - CITS

• Non ferrous metal: Do not possess iron as main Constituent. Ex: Copper, Tin, Zinc.
• Alloy is a mixture of two or more elements, with one being a metal. Ex. Bronze, Brass.
Polymers
• Organic compounds consist of carbon + one or more other element such as oxygen, hydrogen, nitrogen and
chlorine.
• Long chain molecules formed by polymerization
• Basic building unit monomer
• Light in weight, soft, poor conductors of heat and electricity, corrosion resistance, formability
• Ex: Plastics, Leather, Cotton, Rubber, etc.
Composites
• Consists of two or more phases whose combination produces properties that are superior to its constituents.
• Matrix + Reinforcement = composite
Ex: Cemented carbide, Reinforced cement concrete, Fiber glass reinforced plastic etc.
Factors in selection of Materials for
Engineering Application
• Availability of the material
• Ease of handling
• Cost of the material
• Cost of processing
• Aesthetic
• Recycling
• Easiness in fabrication such as machinability, weldability, castability, forgeability etc.
• Capacity to meet service demand Ex: proper strength, wear resistance, corrosion resistance etc.
• Hardness: Resistance to indentation (penetration), abrasion or scratching
• Desirable property for dies, punches, cutting tool
• Toughness: Ability of material to absorb energy during plastic deformation up to fracture (During impact or
shock load)
Mechanical Properties
• strength: Ability of material to withstand external load or force without failure

• Tensile strength: Ability of material to withstand tensile load (axial pull) without failure
• Tensile strength = Max.tensile load
original cr.sectional area
• Compressive strength : Ability of material to withstand compressive load (axial push) without failure
• Compressive strength = Max.compressive load
original cr.sectional area
• shear strength: Ability of material to withstand tangential load without failure across resisting section
• shear strength = Max.tangential load
original cr.sectional area
• Torsional strength: Ability of material to withstand twisting load without failure across resisting section

• Torsional strength = Max.twisting load
original cr.sectional area

• Bending strength: Ability of material to withstand breaking load by bending across resisting section
• Bending strength = Max.bending load
original cr.sectional area

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CITS : WCS - Mechanical - Exercise 2