This document provides an introduction to machine design concepts and principles. It defines machine design as using scientific principles and imagination to design machines to perform specific functions efficiently. The document outlines the machine design process, including defining the problem, analyzing requirements, selecting appropriate mechanisms and materials, and preliminary design. It also discusses important machine elements, mechanical properties of materials, stress-strain diagrams, and industry codes and standards relevant to machine design. Key definitions are provided for terms like load, stress, strain, and stress systems.

1. UNIT 1
INTRODUCTION
CONTENTS
• Definitions: Normal, Shear, Biaxial and Tri axial stresses,
stress tensor, principal stresses.
• Engineering Materials and their mechanical properties
•Stress – strain diagrams
• Stress analysis
•Design considerations: codes and standards

2. Machine design
• Decision making process.
Ex: Design of a chair: Factors to be considered
1. Purpose
2.Material selection
3.Aesthetics
4.Ergonomics
“Bad decision leads to bad design and
ultimately bad product”.

3. MACHINE DESIGN
• Definitions:
1. 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.
2. Machine design is the art of developing new ideas for the
construction of machines and expressing those ideas in the form of
plans and drawings.

4. 1. Statement of the problem: writing down all the data and also what
is required. This information will indicate the nature of the problem
and purpose of the design.
2. Analysis of the problem: analysis of all internal and external forces
acting on machine part.
Analysis can be done by making assumptions, sketches, direction of
forces, magnitude, point of application of forces etc.
3. Selection of mechanism, material and stresses:
Mechanism: Strength, accuracy of motion, efficiency and cost.
Material: Consideration of Life of various parts, availability, application
and cost.
Stress: selection of proper allowable stress
4. Preparation of preliminary design: probable dimensions of the part is
decided( considering strength, rigidity and resistance to wear)

5. Machine Elements
• Springs
• Fasteners
• Bearings
• Shafts
• Gears

6. Mechanical properties of
Materials

7. Examples

8. Stress strain diagram
• Tensile test: To study/calculate the properties of different
materials.
• Stress-Strain diagram of mild steel.

9. 9

10. Stress strain diagram for different
materials

11. Codes and standards
Code: set of specifications for the analysis, design, manufacture and
construction.
Ex: 1. ASME Y 14.5- used in specifying GD&T symbols and values in drawing.
2. ASME/ANSI B4.1 and B4.2- while designing or specifying the diameters of
mating shafts and holes you will need these standards to select the correct
standard deviation symbols based on fits you want.
3. JIS D1601: describes the various vibration testing methods required to
validate the automobile components.
Standards: Set of Specifications for the parts, materials or processes.
The organizations and societies listed below have established specifications for
standards
ANSI B4.1

12. • Aluminum Association(AA)
• American Gear Manufacturers Association(AGMA)
• American Institute of Steel Construction(AISC).
• American Iron and Steel Institute(AISI)
• Society of Automotive Engineers(SAE).
• Industrial Fasteners Institute(IFI)
• American Society of Mechanical Engineers(ASME)- Leading
organization .
– Rules for safety for design, fabrication and inspection of boiler and
pressure vessel
• National Bureau of Standards(NBS)
• American National Standards Institute(ANSI)

13. Important definitions:
• Load :
• Types of load : Dead/ Steady Load , Live or variable load, shock load, impact
load
• Stress:
• Types of stress:
• Strain
• Types of strain: tensile, compressive, shear strain, volumetric stain, superficial
strain.
• Hooke's law:
• Poisson's ratio:
• % elongation and % reduction in area

14. Stresses due to normal and shear load
• Stresses on oblique section: calculation of normal and shear
stress
–Uniaxial stress system :member subjected to direct stress on one plane.
–Biaxial stress system: member subjected to direct stresses on two mutually
perpendicular directions.
–Member subjected to two perpendicular stresses accompanied by a state of
simple shear: Member subjected to General 2 Dimensional stress system.
–Calculation of principal stresses