Tamil Nadu HSE Second Year Basic Mechanical Engineering flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Ferrous metal

Metal having iron as its principal constituent; includes steel and cast iron, usually magnetic and prone to rust unless protected.

Annealing

Heat treatment that heats metal then cools it slowly to soften it, relieve internal stresses, and improve machinability.

Ductility

Property that allows a metal to be drawn into thin wires without fracture; opposite of brittleness.

Grey cast iron

Cast iron with graphite flakes, giving good damping, machinability and compressive strength but low tensile strength.

First-angle projection

Orthographic method in which the object lies between observer and plane; front view appears above top view.

Representative fraction

Ratio of drawing length to actual length, written as 1:2, 1:1 or 2:1, used to express drawing scale.

Isometric scale

Scale used for isometric drawing, about 0.816 times true length, because isometric axes are foreshortened.

Hooke's law

Within elastic limit, stress is directly proportional to strain; the constant ratio is Young's modulus.

Factor of safety

Ratio of ultimate or yield stress to allowable working stress, allowing for uncertainty and overload.

Bending equation

M/I = σ/y = E/R relates bending moment, second moment of area, bending stress, distance from neutral axis and radius.

Shear stress

Force acting parallel to a surface divided by the area resisting it; symbol τ, unit N/mm².

Pattern allowance

Extra dimension added to pattern for shrinkage, machining, draft and distortion so casting meets final size.

Green sand mould

Mould made from silica sand, clay, water and additives in moist state; cheap but lower strength.

Arc welding

Fusion welding process using electric arc between electrode and work to melt and join metal.

Cutting speed

Surface speed of workpiece or cutter relative to cutting edge, usually expressed in metres per minute.

Up milling

Conventional milling where cutter rotation opposes feed; chip starts thin and ends thick, safer for roughing.

Tool signature

Standard sequence of angles and dimensions specifying a single-point lathe tool geometry for grinding and setting.

First law of thermodynamics

Energy conservation for a system: heat supplied equals change in internal energy plus work done by system.

Carnot efficiency

Maximum possible efficiency between two reservoirs, 1 − Tc/Th, using absolute temperatures; no real engine exceeds it.

Polytropic process

Process following PV^n = constant; n = 0 isobaric, n = 1 isothermal, n = γ adiabatic.

Dryness fraction

Ratio of mass of dry steam to total mass of wet steam; used to calculate enthalpy hf + xhfg.

Rankine cycle

Ideal steam power cycle with pump, boiler, turbine and condenser; efficiency depends on steam pressure and temperature.

Compression ratio

Ratio of total cylinder volume to clearance volume; higher ratio generally improves SI engine efficiency.

Valve overlap

Period when both inlet and exhaust valves are open near top dead centre to improve scavenging.

Bernoulli's equation

For steady ideal flow, pressure head plus velocity head plus elevation head remains constant along a streamline.

Reynolds number

Ratio ρVD/μ used to indicate laminar, transitional or turbulent flow; values below about 2000 are laminar.

Cavitation

Formation and collapse of vapour bubbles in low-pressure regions, causing noise, vibration and pump impeller damage.

Least count

Smallest measurement an instrument can read; vernier caliper often 0.02 mm and micrometer often 0.01 mm.

Sine bar

Precision tool using sin θ = h/L to set or measure angles with slip gauges and a surface plate.

Go gauge

Limit gauge that checks maximum material condition and must pass; does not measure actual size.

Preventive maintenance

Scheduled inspection, lubrication and servicing carried out before failure to reduce breakdowns and extend equipment life.

Lockout tagout

Safety procedure isolating energy sources, locking them off and tagging before maintenance to prevent accidental startup.