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					 Machine Design

    What is the importance of Machine Design for
      engineers?


What is Machine Design?

      Creation of new and better machines AND

      Improving   existing ones

      So that it is economical in the cost of production and operation.
Machine Design
      How a design is born
                                                              Market
                                                              survey

                                                             Aesthetic
                                         marketability
                                                              Ease of
                Requirement                                  handling

                                                               Safety
                                          Availability of
Creation                                     FUNDS
                                                            Economical
                      Model                Available
                 (Rough idea)              material         Recyclability

                                         Manufacturing
                                           resources
                                               Material/s
           Analysis       Force/stress                         Sizes
                                                 used
What is the basic knowledge required for Machine
  Design?


    • Mathematics
    •Mathematics
                                  • Mechanics of Machines
    • Engineering Mechanics
    •Engineering Mechanics
                                  • Mechanics of Materials
    •Strength of Materials
    • Strength of Materials       • Fluid Mechanics & Thermodynamics

    •Workshop Processes
    • WorkshopProcesses

    •Engineering Drawing
    • EngineeringDrawing

    • Computing

    • Finite Element Analysis, Computational Fluid Dynamics etc
Important considerations in Machine Design

   1. Type of   LOAD        and   STRESSes      caused by the load


      • Dead loads                 • Stress and strain
                                    (Tensile, compressive, shear)
      • Live loads

           Steady loads            • Thermal stresses

           Variable loads
                                   • Torsional stresses


      • Shock loads (suddenly)     • Bending stress

      • Impact loads (applied
      with some velocity)
Important considerations in Machine Design…..

   2. KINEMATICS of the machine (Motion of the parts)


       Find the simplest arrangement that would give the most
       efficient motion that is required.



   3. Selection of MATERIALs


       Knowledge of the properties of the materials and their
       behaviour under working conditions is required.

       Strength, hardness, durability, flexibility, weight, resistance
       to heat and corrosion, electrical conductivity, machinability,
       etc.
Important considerations in Machine Design…..
     3. Selection of MATERIALs

                   Metal             Non-metal


         Ferrous       Non-ferrous

        Physical properties: Density, Melting point, Elec/thermal properties

        Mechanical properties:
        • STRENGTH     – resist externally applied loads without breaking
                                                                or yielding
        • STIFFNESS    – resist deformation under stress
        • ELASTICITY – regain original shape once the force is removed
        • PLASTICITY – property which retains deformation (required for
                                                               forging etc)
        • DUCTILITY    – ability to be drawn into a wire by a tensile force
        • BRITTLENESS – sudden breaking with minimum distortion
        • TOUGHNESS – resist fracture due to high impact load
        • CREEP        – deformation under stress and high temperature
        • FATIGUE      – ability to withstand cyclic stresses
        • HARDNESS – resistance to wear, scratching, deformation,
                                                          machinability etc
Important considerations in Machine Design…..

   4. Form and size of the parts

      Use I-beam or Angle-iron?

      The size will be determined by the forces/torques
      applied (stresses on the object) and the material used
      such that failure (fracture or deformation) would not
      occur
General procedure in Machine Design…..


      Need or aim        Recognize and specify the problem


        Synthesis        Select the mechanism that would give the desired
                         motion and form the basic model with a sketch etc

 Analysis of the FORCES


    Material selection


                                 Determine the stresses and thereby the
   Design of elements
                                 sizes of components s.t. failure or
                                 deformation does not occur

      Modification       Modify sizes to ease construction & reduce overall co


    Detailed drawing                                       Production
Syllabus and method of evaluation

                  Course content                                     Time allocated
                                                         Sessions
              ME209 MACHINE DESIGN 1                                 L    T   P    A
     Introduction to machine design: Principles and                  01       04
     methodology; a field visit.
                                                            3
     Dynamics of simple mechanism:                                   01       06
             Force analysis of a linkage mechanism
     Failure analysis of mechanical elements:               3        01       10
                            Design of a cottered joint
     Design of machine elements:                            6        01       16
                              Design of a flywheel
     Design of a simple mechanical device:                  4        01       12
                           Design of a screw clamp
     Design of steel structures:                           10        01       16
     Design Project                                         4                      14
                                                 Total     30        06       64 14

           Course                  Assignments            Coursework
         Evaluation
                                       20                       80

				
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posted:10/3/2012
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Jun Wang Jun Wang Dr
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