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

Requirement

Model(Rough idea)

Creation

How a design is born

marketability

Availability ofFUNDS

Availablematerial

Manufacturingresources

Analysis

Market survey

Aesthetic

Ease ofhandling

Safety

Economical

Recyclability

Force/stressMaterial/s

usedSizes

What is the basic knowledge required for Machine Design?

•Mathematics

•Engineering Mechanics

•Strength of Materials

•Mathematics

•Engineering Mechanics

•Strength of Materials

•Workshop Processes

•Engineering Drawing

• Mathematics

• Engineering Mechanics

• Strength of Materials

• Workshop Processes

• Engineering Drawing

• Computing

• Finite Element Analysis, Computational Fluid Dynamics etc

• Mechanics of Machines• Mechanics of Materials• Fluid Mechanics & Thermodynamics

Important considerations in Machine Design

1. Type of LOAD and STRESSes caused by the load

Steady loads

• Dead loads

• Live loads

Variable loads

• Shock loads (suddenly)

• Impact loads (applied with some velocity)

• Stress and strain (Tensile, compressive, shear)

• Thermal stresses

• Torsional stresses

• Bending stress

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

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

Metal Non-metal

Ferrous Non-ferrous

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…..

Detailed drawing

Need or aim

Synthesis

Analysis of the FORCES

Material selection

Design of elements

Modification

Recognize and specify the problem

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

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

Modify sizes to ease construction & reduce overall cost

Production

WITH PROPER MACHINE DESIGN KNOWLEDGE

Syllabus and method of evaluation

MACHINE DESIGN II Subject code : ME603Number of Lecture Hrs per week : 03+01 Hrs. Question to be set : 3 from unit I & II and 2 from unit III.Question to be answered : 2 from unit I & II and 1 from unit III.UNIT ISpur Gears: Review of involute characteristics, standard systems of gear tooth, force analysis, gear tooth failures , loads on gear teeth- dynamic loads, beam strengths, Lewis equation, Lewis form factor, effective load on gear teeth, dynamic load, wear strength, Buckingham’s equation, gear design for maximum power transmitting capacity.Helical gears: Terminology, virtual number of teeth, tooth proportions, force analysis, beam strength, effective load, wear strength.Bevel Gears: Terminology, force analysis, beam strength, effective load, wear strength.Worm Gears: Terminology, proportions of worm and worm gears, force analysis, strength rating and wear rating of worm gears, thermal considerations. (14 L + 4T) 

UNIT II Springs: Types, materials, end connections fort helical springs, stresses and deflection of helical springs of circular wire, design of springs subjected to static and fluctuating load, springs in series and parallel, helical torsion springs, leaf springs, ripping of leaf springs, length of leaves.Pressure Vessels: Classification- thin cylinders and thick pressure vessels subjected to internal pressure, thick cylinder shells- Lami’s equation, Clavariono’s equation and Birni’s equation, compound cylindrical shells, cylinder heads and cover plates.Design of connecting rod and crank shaft

(14 L + 4T)UNIT IIIRolling contact bearings: Types, Stribeck’s equation, static and dynamic carrying capacity, equivalent bearing load, load- life relationship, selection of radial bearings, reliability of a bearing, lubrication of ball and roller bearings.Journal Bearing: Hydrodynamic lubrication and Reynold’s equation, wedge film and squeeze film journal bearing, bearing characteristic number and bearing module for journal bearing, co-efficient of friction, critical pressure, Sommerfield Number, Heat generated in journal bearing, Design procedure. (10 L + 3T)   

Textbooks:1. K.Mahadevan and K.Balaveera reddy- Design Data Handbook (SI Units), KREC, Surathkal2. R.S. Khurmi & J.K. Gupta- Machine Design, S Chand Publications 3. V B Bhandari- Design of machine elements, TMH Reference books:1. J.Shigley- Mechanical Engineering Design, McGraw Hill2. Siegel, Maleev & Hartman- Mechanical Design, International Textbook Co.3. Sadhu Singh- Machine Design, Khanna Publishers.4. Ghosh- Practical Machine Design, S. Bhattacharya Co.5. Spotts- Design Of Machine Elements, Prentice Hall (India)

 

Requirement:Design Data HandbookScientific Calculator

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