Shibendu S. Roy Dept. of Mechanical Engineering
www.geocities.com/ssroy99/homepage.html
Reference Books 1.
V.B. Bhandari, “ Design of Machine Elements ”, , >, Tata McGraw Hill.
2.
J.E. Shigley, C.R. Mischke, “ Mechanical Engineering Design ”, ”, Tata McGraw Hill.
Machine Design Handbook 1.
“Design Data”, Compiled by Faculty of Mechanical Engineering, PSG College, Coimbatore
2.
“CMTI Hand Book”, Compiled by Scientists of Central Manufacturing technology Institute, Bangalore
Topics to be Covered Chapter
Introduction
Topics - Review of Stress, Strain and Complex stresses in machine members - Basic procedure of machine design & machine element design - Manufacturing & other consideration in machine design - Modern Computational Tools for Machine Design
- Role of CAD/CAE in Machine Design
Engineering Materials
- Mechanical properties of Engineering materials - B.I.S system of designation of commonly used Engineering Materials - Selection of Materials
Rod Joints
- Cotter Joint - Knuckle Joint
Plate Joints
- Threaded Joints - Welded Joints
Design against Static Load
- Elastic failure theories, Factor of safety, Service factor - General principles & procedures of design of machine elements
Design against Dynamic Load
- Stress Concentration factor, Fatigue failure, Endurance limit etc. - Reversed stresses- design for finite & infinite life, Impact stresses etc.
Design of Shafts, Keys, Splines
- Design of Shaft under Torsion, Bending, Axial & Combined loads - Design of keys like square & flat, saddle, sunk, woodruff keys etc.
Statistical Considerations in Design
- Reliability, Probabilistic approach to Design etc..
Design of Machine Element Gear Drive
Pressure vessel
Clutch IC engine parts
C-frame
Brake
Coupling Spring
Bearing
Belt, Rope, chain Drive
Connecting rod Power Screw
Cam
Shaft & Axle
Key Cotter & Knuckle Joint
Riveted Joint
Welded Joint
Bolted Joint
Machine Design transfers
Kinematic Link
transforms
Kinematic Pair Kinematic Chain
Motion
Mechanism
One link fixed
transfers
Mechanism Machine
Machine Tool
Machine
Energy
transforms
Machine tool is a contrivance having a combination of mechanisms/machines whereby a cutting tool is enabled to operate in a pre-conceived manner in order to produce a surface of desired shape, size or a degree of finish by removing metal from workpiece in the form of chips. All Machines are Mechanism but all Mechanisms are not Machine All Machine Tools are Machine but all Machines are not Machine Tool
Machine Design Design Design Analysis
Inputs
Mechanism
Design Synthesis
Outputs
decision –making process
process of creating new configuration/ mechanism
Selecting optimum/best configuration from no. of existing mechanism
Selecting materials from no. of alternative materials
Determination of optimum shape & dimensions of the component on the basis of design analysis
is given
Given Configuration, material & assume mode of failure
determines the dimension
Manufacture r
General Procedure in Machine Design
Custome r
Identification of Need Problem definition, Design specification Collecting relevant design information & feasibility study Design Conceptualization/ Preliminary design i.e. Mechanism synthesis
Design Synthesis
Modeling & Simulation Engineering Analysis CAD/CAE Design Analysis
Design Optimization Design Evaluation Detail Design of Components Design Communication & Documentation
Basic Procedure of Design of Machine Element Specify functions of element Determine forces acting on element Select suitable material for element Determine failure mode (s) of element Determine geometric dimensions of element based on above failure mode Check & modify dimensions for assembly & manufacture Check design at critical cross-sections Prepare detail engineering drawing of element
Basic Requirements of Machine Elements Broad objective of designing a machine element is to ensure that it preserves its operating capacity during the stipulated service life with minimum manufacturing & operating costs Strength Rigidity Wear Resistance Minimum Dimensions & Weight Manufacturability Safety Reliability Maintainability Conformance to Standards Minimum Life Cycle cost
“Standards” in Machine Design Standardization
Standardization is defined as obligatory norms, to which various characteristics of a product should conform. The characteristics include materials, dimensions and shape of the component, method of testing and method of marking, packing and storing of the product.
Standard Standard is defined as a set of specifications for parts, materials or processes Purpose of Standard
to reduce the variety & limit the no. of items to a reasonable level
Code Code is defined as a set of specifications for the analysis, design, manufacture, testing and erection of the product
Purpose of Code
to achieve a specified level of safety
“Standards” in Machine Design Advantages of Standardization The
reduction in types & dimensions of identical components, to a rational number, makes it possible to manufacture the standard component on mass scale in a centralized process.
Standard
parts are easy to replace when worn out due to interchangeability.
The
application of standard machine elements & especially the standard units reduce the time & effort needed to design a new machine.
Standardization results in substantial saving in Designer’s effort The
standards of specifications & testing procedures of machine elements improve their quality & reliability.
In designing, the aim is to use as many standard components as possible for a given machine Company Standards
Types of Standards
National Standards
International Standards
I.S / B.I.S B.S A.I.S.I / S.A.E D.I.N
India UK USA German
“Standards” in Machine Design Indian Standards in Mechanical Engineering Design SP 46
Bureau of Indian Standards on “Engineering Drawing Practice for Schools & Colleges
I.S. 210
Seven grades of grey cast iron
I.S. 1570 :
Chemical composition of various grades of alloy steel
I.S. 733 : 1983
Mechanical Properties of wrought Al. & Al alloy Bars, Rods for general purposes
I.S. 736 : 1986
Mechanical Properties of wrought Al. & Al alloy Plates for general purposes
I.S. 919
Recommendations for Limits & Fits for Engineering
I.S. 2709
Guide for selection of fits
I.S. 8000
Geometrical tolerancing on technical drawings
I.S. 4218 : 1996
Designation & Dimension of screw threads, bolts & nuts
Preferred Numbers When
a machine is to be made in several sizes with different powers or capacities, it is necessary to decide what capacities will cover a certain range efficiently with minimum number of sizes.
For
example, a company want to manufacture seven different models of electric motors ranging from 0.25 HP to 5 HP to cater to the need of different customers.
Preferred
numbers are used to specify the ‘sizes’ of the product in these cases.
French Engineer Charles Renard first introduced Preferred Numbers in the 19th century.
The system is based on the use of geometric progression to develop a set of numbers.
Basic series
Common Ratio
% increase in steps
Preferred Numbers [in between 1 to 10 ]
R 5 series
101/5
1.58
58%
1.0, 1.6, 2.5, 4.0, 6.3, 10.0
R 10 series
101/10
1.26
26%
1.0, 1.25, 1.6, 2.0, 2.5, 3.15, 4.0, 5.0, 6.3, 8.0,10.0
R 20 series
101/20
1.12
12%
1.0,1.12,1.25,1.4,1.6,1.8,2.0,2.24,2.5,2.8,3.15,3.55,4.0,4.5,5.0,5.6,6.3,7.1,8.0,9.0,10.0
R 40 series
101/40
1.06
6%
1.0,1.06,1.12,1.18,1.25,1.32,1.4,1.5,1.6, ……………………………………, 10.0
R 80 series
101/80
1.03
3%
1.0,1.03, 1.06,1.09, 1.12,1.16, 1.18, 1.21,1.25,1.29,1.32,1.36,1.4,…..1.6, ………, 10.0
Aesthetic Considerations in Machine Design When there are a number of products in the market, having the same qualities of efficiency, durability and cost, the customer will naturally attracted towards the most appealing product. The external appearance is an important feature, which not only gives grace and luster to the product but also dominates the sale in market.
Automobiles
Industrial Design
Household Appliances
Audio Visual Equipments
The job of an Industrial Designer is to create new forms & shapes, which are aesthetically pleasing.
The external appearance of the products is a cumulative effects of number of factors : Form
Step Stream
Colour
Surface finish & Tolerances
Materials
Manufacturing Methods
Taper Shear Sculpture
Relationship between Functional requirement & Appearance of the Product
In many cases, functional requirements result in shapes, which are aesthetically pleasing. The evolution of the streamlined shape of the boeing is the result of studies in aerodynamics for effortless speed. Chromium plating on the household appliances is for corrosion resistance rather than for pleasing appearance
Ergonomic Considerations in Machine Design Ergonomics is defined as the relationship between Man & Machine and the application of anatomical, physiological and psychological principles to solve the problems arising from Man-Machine relationship.
Topics of Ergonomic studies in machine design Anatomical factors in design of driver’s
seat.
Layout of instrument dials & display panels for accurate perception by the operators
Design of hand levers & hand wheels.
Ergonomists have carried out experiments to determine the best dimensions of driver’s seat, the most convenient hand or foot pressure or dimensions of levers and hand wheels.
Concurrent Engineering : S imultaneous Design P rocess Sequential Design Process Marketing Department
Concurrent Engineering Concurrent Engineering is defined as the design process that brings both design & manufacturing engineers together during the early phases of the design process.
Design Office Customer’s requirement
Production Department
Sales & Service Department
Manufacturability & Testability Cost, Sales & servicing
Design Engineering : Concurrent Engineering Concept
Ergonomics & Appearance
Reliability, Maintainability & safety
Motivation Most Economic
Requirements
Most Productive Improved Quality
Successful entry of a product into the market can best occur if it can complete the above cycle in the shortest possible time & at the lowest cost while maintaining very high product quality & reliability
CAD
Computer Aided Design
CAE
Computer Aided Engineering
CAM
Computer Aided Manufacturing
VP & VR
Virtual Prototyping & Virtual Reality
is
the use of Information technology/ computer based tools for supporting Engineers in tasks such as Design, Analysis, Simulation, Optimization, Manufacturing, Planning etc.
is
to design, develop and optimize the product or process.
CAE areas: Stress
analysis, Vibration analysis using FEM
Thermal
& fluid flow analysis using CFD
Kinematic & Dynamic Analysis & Simulation
Analysis tools for manufacturing process simulation
Optimization
of the product or process
is
the use of wide range of computer based tools that assist Engineers & other Design Professionals in their design activities.
is is
to design, develop and optimize the product.
the use of wide range of computer based tools that assist Production Engineers & Tool and Die maker, CNC machinists, in the manufacture or prototyping of products.
Motivation Most Economic
Requirements
Most Productive Improved Quality
Successful entry of a product into the market can best occur if it can complete the above cycle in the shortest possible time & at the lowest cost while maintaining very high product quality & reliability
VP : Virtual Prototyping VP is about Presentation, Testing, & Analysis of 3-D CAD models prior to creating any physical prototype
Visualization Models : greater communication, productivity & efficiency through realistic graphical modelling based on full colour, natural texture & appearance, dynamic viewing of models from any user specified angle & orientation.
Fit & Interference checking of mechanical assemblies
Testing & Verification of functions & performance : Structural & Physical phenomena analysis [FEM, CFD], Motion analysis.
Manufacturing Evaluation
Assembly analysis
Human factor analysis
CAD-CAM-CAE Software CAD/CAM/CAE software
Purpose
CATIA NX (UniGraphics + IDEAS)
3-D modeling, analysis & simulation etc.
PRO-ENGINEER SOLID WORKS SOLID EDGE INVENTOR Mechanical DESKTOP MasterCAM SolidCAM SmartCAM
3-D modeling & manufacturing simulation
CAD-CAE Software CAE software
Purpose
ADAMS
Multi-body dynamic analysis & simulation
SimDESIGNER with CATIA
Multi-body dynamic analysis & simulation
Visual NASTRAN
Multi-body dynamic analysis & simulation
Working Model
Multi-body dynamic analysis & simulation
ANSYS
Finite Element Analysis
NASTRAN
Finite Element Analysis
ABAQUS
Finite Element Analysis
LS-DYNA
Finite Element Analysis, Crash simulation
DEFORM
Finite Element Analysis, Crash simulation
PAMCRASH
Finite Element Analysis, Crash simulation
FLUENT
Computational Fluid Dynamics
Altair Hyper Mesh
Meshing for Finite Element Analysis
Computational Tools Software MATLAB
Purpose Design calculation, dynamic analysis & simulation, design optimization, control
Mathematica MathCAD Maple TK Solver Excel
Design calculation
CAD-CAE Tools Design Phase
Required CAD-CAE Tools
Related Software (s)
conceptualization
Geometric modeling, Graphics aids, visualization
CATIA, NX, SolidWorks, Solid Edge, Pro-E, Inventor…
Modeling & Simulation
Geometric modeling, Graphics aids, visualization, Simulation Package
CATIA…, ADAMS….
Design Analysis
Geometric modeling, Analysis Package, visualization
CATIA…, NASTRAN, ANSYS…
Design Optimization
Geometric modeling, Optimization module
CATIA…, MATLAB…
Design Evaluation
Geometric modeling, Customized programs & Package
CATIA…
Design communication & documentation
Geometric modeling, Drafting package
CATIA…, AutoCAD…
Design
CAD-CAE Tools Performed computation on high end computer
CAD
3-D CAD model
Pre-Processor
Solver
Post-Processor
CAE
Define the model & environment factors to be applied
Display results in graphical form using visualization tools
Assignment # 1 1. Explain with example, the different steps involved in machine design process & in design of machine elements? What are the basic requirements of machine elements? 2. Distinguish between design synthesis and design analysis. 3. What is Standardization & what are the advantages of standardization? Give examples of Indian standards for commonly used engineering materials. 4. What are preferred numbers? How many basic series are used? What is R10 series? Develop R 10 series from 2 to 20. 5. What is an industrial design? What is the relationship between functional requirement and external appearance of the product. 6. Define ergonomics. What is the scope of ergonomics in machine design? 7. Distinguish between sequential design and concurrent engineering. 8. Explain the functional area of a basic CAD-CAE system & their applications & benefits in machine design process with examples. 9. Class Test Problem # 1. 10. Class Test Problem # 2.
Last date of submission : 08 th February, 2008
