Intro To Mechanical Engineering

Intro to Mechanical Engineering

Mech. Eng. Top 10: ASME SurveyAutomobile: High-power lightweight engines, efficient massmanufacturingApollo: Saturn V launch vehicle (7.5 million pound thrust),command and service module, lunar excursion modulePower generation: Conversion of stored energy into electricity,manipulation of chemical-, kinetic, potential-, and nuclearenergy, large-scale power productionAgriculture mechanization: Powered tractors, mechanizedharvesting, high-capacity irrigation pumps, computerized cropsmanagementAirplane: Propulsion (jet engines), lightweight materials,electromechanical control systems

Mech. Eng. Top 10: ASME SurveyIntegrated circuit mass production: IC manufacturingmachines, alignment systems, temperature- and vibrationcontrol, motors, bearingsAir-conditioning and refrigeration: Compressors, refrigerants,heat exchangersComputer-aided engineering technology: Computer-aideddesign, analysis, manufacturing, virtual collaborativesBioengineering: Imaging, prosthetics, minimally invasivesurgery, tissue engineeringCodes and standards: Interchangeability, interoperability,interconnectivity

Mech. Eng.: Typical ProgramThermo-Fluids: Heat transfer, Energy Systems, HVAC,IC EnginesMechanical Systems: Vibrations, Feedback control,Mechatronics, MEMSDesign: Composites, Machine Design, FEMCore: Statics, Dynamics, Thermodynamics, Fluidmechanics, Solid mechanics

Types of Motion Linear motion– motion in a straight line (example: train on atrack) Reciprocating motion– linear motion that goes back and forth(example: pushing a slider-crank back andforth, such as the piston in an internalcombustion engine) Rotary motion– circular motion (example: the hands of aclock moving, or a wheel on an axle) Oscillating motion– circular or arc-motion back and forth(example: the swing of a pendulum or theturning and release of a doorknob)

Machine Components: Basic ElementsGear, rack, pinion, etc.Cam and FollowerChain and sprocketInclined plane wedgeLeverSlider-CrankLinkageWheel/AxleSprings

Inclined PlaneWedgeWood PlaneWorm GearScrew

LeverWeighing ScaleExcavatorScissorsPiano

Wheel and AxleWaterwheelWindmillTurbine

Belt and PulleyChain HoistCraneElevator

GearsBevel GearHelical GearSpur GearRack and Pinion

CamsCylindrical camTranslating CamEnd CamOscillating Cam

SpringsLeaf SpringWasher Spring

FrictionBrake SystemBearing

Forces in StructuresForces and ResultantsFFyθFxRectangular Form: F Fxi FyjPolar Form: F ׀ F ׀ θ Fx Fcos(θ), Fy Fsin(θ) ׀ F ( ׀ Fx2 Fy2), θ tan-1(Fy/Fx)

Moment of a Force―IThe moment of a force is a measure of its tendency torotate an object about some pointMoment of force W about pivot point: W d

Moment of a Force―IIBalancing Beams using moment of forces

Equilibrium of Forces & MomentsObject in equilibrium F 0 F 0 M 0xyo

BuoyancyForce produced by fluid pressureWhen an object is fully or partiallyimmersed in a fluid, due to the pressuredifference of the fluid between the topand bottom of the object, buoyant forceacts on the object causing it to floatThe net upward buoyancy force is equalto the magnitude of the weight of fluiddisplaced by the bodyBuoyancy is important for boats, ships,balloons, and airships

Drag ForceForce that resists the motion of an objectthrough a fluidDrag force arises from the motion of anobject through fluidDrag force arises from the flow of fluidpast an objectAn object moving through a fluidexperiences a force in directionopposite to its motion. Terminalvelocity is achieved when thedrag force is equal in magnitudebut opposite in direction to theforce propelling the object.

LiftLift forces arises as a fluid flows around a structureLift force acts perpendicular to the direction of flow

Mechanical EnergyGravitational Potential Energy: Energy stored by an object as itgains elevation within a gravitational field U mgh, m : mass of object, g sgravitational constant,h : elevation of objectElastic Potential Energy: Energy stored by an object when it isstretched or bent.1 2 U kx , k : spring constant, x spring stretch/compression2Kinetic Energy: Energy associated with an object’s motion.1 2 U mv , m : mass of object, v speed of object2

Work & PowerWhen a force F acting on an object displaces it by distance d, theforce F is said to have done work WW f dPower is the rate at which work is performed WP t

Newton’s Laws of Motion1st Law: Every body continues in its state of rest or ofuniform motion in a straight line unless it is compelled tochange that state by an external force2nd Law: The rate of change of momentum of an objectis proportional to the force acting on the object and is inthe same direction as that forceF m a3rd Law: To every action there is an equal and oppositereaction

Equations of MotionTranslational motionmx Fx, x F1Fn mRotational motion I MI M1Mn

Intro to Mechanical Engineering. Mech. Eng. Top 10: ASME Survey Automobile: High-power lightweight engines, efficient mass-manufacturing Apollo: Saturn V launch vehicle (7.5 million pound thrust), command and service module, lunar excursion module Power generation: Conversion of stored energy into electricity, manipulation of chemical-, kinetic, potential-, and nuclear-energy, large-scale .