Machine Design Chap-1

April 8, 2023 Machine Design 1

www.geocities.com/ssroy99/homepage.html

Shibendu S. Roy

Dept. of Mechanical Engineering


Reference Books1. V.B. Bhandari, “Design of Machine Elements ”, <second edition>, Tata McGraw Hill.

2. J.E. Shigley, C.R. Mischke, “Mechanical Engineering Design”, Tata McGraw Hill.

Machine Design HandbookMachine 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


Chapter Topics

Introduction - 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

Topics to be Covered

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

Cam

C-frame

Spring

Brake

Connecting rod

GearDrive

Shaft & Axle

Welded Joint

Belt, Rope, chain Drive

Bearing

Key

IC engine parts

Pressure vessel

Cotter & KnuckleJoint Bolted Joint

RivetedJoint

Clutch

Coupling

Power Screw


Machine Design

Mechanism

Kinematic Link

MachineMachineMachine Tool

Kinematic Pair

One link fixed

All Machines are Mechanism but all Mechanisms are not Machine

All Machine Tools are Machine but all Machines are not Machine Tool

Mechanism

transfers

transforms

Motion

transfers

transforms

Energy

Kinematic Chain

MachineMachine

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.


Design

Design SynthesisDesign Analysis

Mechanismis given

Inputs Outputs

Machine Design

Given Configuration, material & assume mode of

failure

determines the dimension

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


Identification of Need

Engineering Analysis

Problem definition, Design specification

Collecting relevant design information & feasibility study

Design Conceptualization/ Preliminary design i.e. Mechanism synthesis

General Procedure in Machine DesignGeneral Procedure in Machine Design

Detail Design of Components

Design Optimization

Modeling & Simulation

Design Evaluation

Customer

Manufacturer

CAD/CAE

Design Synthesis

Design Analysis

Design Communication & Documentation


Basic Procedure of Design of Machine Element

Basic Procedure of Design of Machine Element

Specify functions of element

Determine forces acting on element

Check design at critical cross-sections

Determine failure mode (s) of element

Select suitable material for element

Check & modify dimensions for assembly & manufacture

Determine geometric dimensions of element based on above failure mode

Prepare detail engineering drawing of element


Strength

Manufacturability

Conformance to Standards

Minimum Dimensions & Weight

Rigidity

Minimum Life Cycle cost

Reliability

Safety

Wear Resistance

Maintainability

Basic Requirements of Machine ElementsBroad 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


“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

Code is defined as a set of specifications for the analysis, design, manufacture, testing and erection of the product

Purpose of Code Purpose of Code to achieve a specified level of safety

Purpose of Standard Purpose of Standard to reduce the variety & limit the no. of items to a reasonable level

Code


“Standards” in Machine DesignAdvantages of Standardization 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

International Standards

National Standards

Company Standards

Types of Standards Types of Standards

I.S / B.I.S India B.S UK A.I.S.I / S.A.E USA D.I.N German


“Standards” in Machine 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

Indian Standards in Mechanical Engineering Design


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 Audio Visual EquipmentsHousehold Appliances

Industrial DesignIndustrial DesignThe 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 :

ColourForm Surface finish & Tolerances Materials Manufacturing Methods

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

Relationship between Functional requirement & Appearance of the Product

Stream

Sculpture

Step

Taper Shear


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.

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.

Topics of Ergonomic studies in machine designTopics of Ergonomic studies in machine design

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: Simultaneous Design Process

Cost,Sales &

servicing

Customer’s requiremen

t

Ergonomics &

Appearance

Reliability, Maintainability

& safety

Manufacturability & Testability

Marketing Department

Design Office

Production Department

Sales & Service Department

Sequential Design ProcessSequential Design Process Concurrent Engineering 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 Engineering

: Concurrent Engineering Concept


RequirementsRequirements Most Productive

Most Economic

Improved Quality

Motivation

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 wide range of computer based tools that assist Engineers & other Design Professionals in their design activities.

is to design, develop and optimize the product.

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 Production Engineers & Tool and Die maker, CNC machinists, in the manufacture or prototyping of products.


RequirementsRequirements Most Productive

Most Economic

Improved Quality

MotivationSuccessful 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 PrototypingVP : 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

3-D modeling, analysis & simulation etc.NX (UniGraphics + IDEAS)

PRO-ENGINEER

SOLID WORKS

SOLID EDGE

INVENTOR

Mechanical DESKTOP

MasterCAM

3-D modeling & manufacturing simulationSolidCAM

SmartCAM


CAD-CAE SoftwareCAE 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 Purpose

MATLAB Design calculation, dynamic analysis & simulation, design optimization, control

MathematicaDesign calculationMathCAD

Maple

TK Solver

Excel


Design Phase Required CAD-CAE Tools Related Software (s)

Design 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…

CAD-CAE Tools


3-D CAD model3-D CAD model Pre-Processor Solver Post-Processor

CAD-CAE Tools

CAD

CAE

Define the model & environment factors to be

applied

Performed computation on

high end computer

Display results in graphical form using visualization tools


Assignment # 11. 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 : 08th February, 2008


Thank You

Machine Design Chap-1

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