DESIGN OF MACHINE ELEMENTS

1 NivishGeorgeDESIGN OF MACHINE ELEMENTSPoor DESIGN ??Ref: of mechanical Engineering2 Definition MACHINE DESIGN is defined as the use of scientific principles, technical information and imagination in the description of a MACHINE or a mechanical system to perform specific functions with maximum economy and efficiency DESIGN is an innovativeand highly iterativeprocessMachine DesignDepartment of mechanical Engineering3 The DESIGN ProcessDepartment of mechanical Engineering4 Market of mechanical Engineering5 Ref: : : of mechanical Engineering6 Selection of of mechanical Engineering7 Ref.

2 Automobile Engineering, Vol-1, of configuration and selection ofjoining of mechanical Engineering8 DESIGN of Individual of mechanical Engineering9 Prepare Assembly and detail drawing Modify drawings after testing prototypeRef: ContentsDepartment of mechanical Engineering10 Mod. 1 Mod. 2 Mod. 4 Mod. 5 Mod. 3 Mod. 6 Basic RequirementDepartment of mechanical Engineering11 MACHINE ElementsStrengthRigidityWear resistanceMin. Dim. And weightManufac-turabilitySafetyConformanc e to StandardsReliabilityMaintaina-bilityMin. Life cycle costTRADITIONAL DESIGN METHODSD epartment of mechanical Engineering12 DESIGN by craft evolution DESIGN by drawingRef: : IN DMED epartment of mechanical Engineering13 Failure Criterion Elastic deflection General yielding FractureGeometry & Dimensions Operating conditions Basis of failure criterionDesign Modifications Assembly & manufacturing considerationsSpecify functions Bearing Spring Screw fasteningForce determination Free body diagramSelection of Material Availability Man.

3 Considerations PropertiesWORKING DRAWINGDESIGN SYNTHESISD epartment of mechanical Engineering14 DESIGN Synthesis is defined as the process of creatingor selectingconfigurations, materials, shapes and dimensions for a FormulationOptimisationAESTHETIC CONSIDERATIONSD epartment of mechanical Engineering15 ERGONOMIC CONSIDERATIONSD epartment of mechanical Engineering16 Ergonomics is defined as the relationshipbetween man and machineand the application of anatomical, physiological and psychological principlesto solve the problems arising from man- MACHINE relationship DESIGN of driver s seat Layout of instrument dials and display panels DESIGN of hand levers and hand wheels Energy expenditure in hand and foot operations Lighting.

4 Noise and climatic conditions in MACHINE of mechanical Engineering17 Display instrumentsControlinstrumentsQuantitativ emeasurementEasily accessible and logically positionedState of affairsConform to the anatomy ofhuman partsPredeterminedsettingsProper colourOverviewDepartment of mechanical Engineering18 Need of .. Definition ?????Requirement Procedure Tradition Synthesis DESIGN considerationsStandardizationDepartment of mechanical Engineering19 The obligatory norms, to which various characteristics of a product should conform.

5 Standards: Set of specifications for parts, materials or processes Codes: Set of specifications for analysis, DESIGN , testingStandardsCompany StandardsEg: Service StandardsNational StandardsEg: IS, DINI nternational StandardsEg:ISOS tandardizationDepartment of mechanical Engineering20 The characteristics include materials, dimensions and shape of the component, method of testing and method of marking, packing and storing of the product. Standards for materials, their chemical compositions, mechanical properties and Heat Treatment FG 150, FG 200, FG 220-(IS 210): Strength 55Cr3-(IS 570 Part 4).

6 Chemical composition Standards for shapes and dimensions of commonly used MACHINE ELEMENTS Dimension and cross sectionof V belts (IS 2494)StandardizationDepartment of mechanical Engineering21 Standards for fits, tolerances and surface finish of component FitIS2709 (Guide for selection of fits) TolerancesIS 919 (Recommendations for limits and fits for engineering) Surface texture IS 10719 Standards for testing of products Testingof pressure vessels IS 2825 Standards for engineering drawing of components SP46by BISfor engineering drawingsStandardization.

7 AdvantagesDepartment of mechanical Engineering22 Reduction in types and dimensions of identical components Reduced manufacturing facilities required for individual organisation Easy replacement and availability Reduced designer tasks Improved quality and reliabilityPreferred SizesBasic SeriesDerived SeriesR5 of Preferred sizesDepartment of mechanical Engineering23 Size of the MACHINE element with preferred sizes5101010201040108010 ReducingIncreasingPreferred NumbersDepartment of mechanical Engineering24 Elasticity is defined as the ability of the material to regain its original shape and size after the deformation.

8 When the external forces are removed Steel is perfectly elastic within a certain limit Amount of deformation a metal undergoes is small Atomsare displaced from their original positions but they don t take up new positionsElasticity Department of mechanical Engineering25 Plasticity is defined as the ability of the material to retain the deformation produced under the load on permanent basis External force deforms the metal to such an extent it cannot fully recover Some metals take up extensive deformations without fracture Atomsare permanently displaced to take up new positionsPlasticityDepartment of mechanical Engineering26 Types of MaterialsDepartment of mechanical Engineering27 Cast ironPlain carbon steelsAlloy SteelsCeramicsCast SteelRubberPlasticsFactors for selectionDepartment of mechanical Engineering28 AvailabilityCostMechanical PropertiesManufacturing ConsiderationsWeighted Point MethodDepartment of mechanical Engineering291 Study of application and preparing a list of desirable properties2 Desirable properties are assigned values3

9 Go-no-go parameters Discriminating parameters4 Weightage is providedWeighted Point Method: EgDepartment of mechanical Engineering30S. alloy steelPlain carbonsteelsStainless steelChromium steels1 Ultimate tensile strength (N/mm2)85085012009502 Hardenability Index608030100 Points for ultimate tensile strength Sum=850+850+1200+950=3850 Rating strength= 850/3850= Weightage index= *5= Points for hardenability Sum=60+80+30+100=270 Rating hardenability index= 60/270= Weightage index= *3= ConcentrationDepartment of mechanical Engineering31 APt IyMbb JrMt The localization of highstresses due to the irregularitiespresent in the component and abrupt changesof cross-sectionCauses of stress concentrationDepartment of mechanical Engineering32 Variation in

10 Properties Load of mechanical Engineering33 Abrupt changes in of mechanical Engineering34 Discontinuities in the component Machining ScratchesStress Concentration Factor (Kt)Department of mechanical Engineering35 = = Mathematical methodExperimental methodsStress Concentration factorsDepartment of mechanical Engineering36 = = Stress Concentration factorsDepartment of mechanical Engineering37 = 4 2 = Stress Concentration factorsDepartment of mechanical Engineering38 Ductile materials under static load Ductile materials under fluctuating load Brittle materialsReduction of Stress ConcentrationDepartment of mechanical Engineering39 Additional Notches and Holes in Tension