1. GENERAL CONSIDERATION IN DESIGN OF MACHINE ELEMENTS
DR.S&S.S GHANDHY GOVT. ENGINEERING COLLAGE ,SURAT
GENERAL CONSIDERATION IN DESIGN OF MACHINE ELEMENTS
PATEL SAVAN M ( )
CHAUHAN MO.SARIK S. . ( )
Nair Mrinal ( )
TANK PRADIP K ( )
PATEL TUSHAR M ( )
Vaishnav Niket ( )
PRIYAKANT GOGHARI ( )
GUIDE BY:
PROF. VIKAS SINHA

2. GENERAL CONSIDERATION IN DESIGN OF MACHINE ELEMENTS
CHAPTER 1
GENERAL CONSIDERATION IN DESIGN OF MACHINE ELEMENTS

3. Introduction To Machine Design
Definition of Machine Design
Machine design is defined as the use of scientific principles, technical information & imagination in the description of a machine or a mechanical system to perform specific functions with maximum economy & efficiency.
Machine Design is defined as the creation of new design or improving the exist one.

4. Design Process:

5. Introduction To Machine Design
Basic Requirement of Machine Elements
Strength and Rigidity
Wear Resistance
Minimum Dimensions & Weight
Manufacturability
Safety
Conformance to standards
Reliability
Maintainability
Minimum Life-cycle Cost

6. Basic Procedure of Design of Machine Elements
Introduction To Machine Design
Basic Procedure of Design of Machine Elements

7. Engineering Materials and their Properties
Material Selection
Selection of proper material for the machine components is one of the most important steps in process of machine design
The best material is one which will serve the desired purpose at minimum costs
Factors Considered while selecting the material:
Availability: Material should be readily available in market in large enough quantities to meet the requirement

8. Material Selection ii) Cost: iii) Mechanical properties:
Manufacturing Considerations:
In some applications machinability of material is an important consideration in selection
Where the product is of complex shape, castability or ability of the molten metal to flow into intricate passages is the criterion of material selection
In fabricated assemblies of plates & rods, weldability becomes the governing factor

9. Properties of Material
Strength: Ability of the material to resist, without rupture, external forces causing various types of stresses
Elasticity: Ability to regain its original shape & size after deformation, when the external forces are removed
Plasticity: Ability to retain the deformation produced under the load on a permanent basis
Stiffness or Rigidity: Ability to resist deformation under the action of an external load

10. Properties of Material
Toughness: Ability to absorb energy before fracture takes place
Malleability: Ability to deform to a greater extent before the sign of crack, when it is subjected to compressive force
Ductility: Ability to deform to a greater extent before the sign of crack, when subjected to tensile force
Brittleness: Property of the material which shows negligible plastic deformation fracture takes place
Hardness: Resistance to penetration or permanent deformation

11. Engineering Material Cast Iron
Cast iron is an alloy of iron & carbon, containing more than 2% of carbon
- Typical composition of ordinary cast iron is:
Carbon = 3-4%
Silicon = 1-3%
Manganese = 0.5-1%
Sulphur = up to 0.1%
Phosphorous = up to 0.1%
Iron = Remainder

12. Engineering Material Cast Iron Advantages:
Available in large quantities,
higher compressive strength,
components can be given any complex shape without involving costly machining operations,
excellent ability to damp vibrations,
more resistance to wear even under the conditions of boundary lubrication,
mechanical properties of parts do not change between room temperature and 350 degree centigrade

13. Engineering Material Plain Carbon Steel
Depending upon the percentage of carbon, plain carbon steels are classified as:
Low carbon steel – Less than 0.3% carbon, popularly known as mild steel, its soft & ductile, easily machined & welded, however due to low carbon content unresponsive to heat treatment
ii) Medium carbon steel – carbon content in the range of 0.3% to 0.5%, popularly known as machinery steel, easily hardened by heat treatment , stronger & tougher than low carbon steel, well machined, respond readily to heat treatment

14. Engineering Material Plain Carbon Steel
iii) High carbon steel – more than 0.5% carbon, popularly known as hard steels or tool steels, respond readily to heat treatment, when heat treated attain high strength combined with hardness, less ductile than low carbon steels & medium carbon steels, difficult to weld, excessive hardness accompanied by excessive brittleness
In applications like automobile bodies & hoods, the ability of the material to deform to a greater extent or ‘ductility’ is the most important consideration so a plain carbon is preferred

15. Engineering Material Plain Carbon Steel
In applications like gears, machine tool spindles & transmission shaft, strength toughness & response to heat treatment are important considerations, medium & high carbon steels are preferred
Spring wires are subjected to severe stress & strength is the most important consideration so high carbon steel is selected for helical & leaf springs

16. Engineering Material Alloy Steel
Carbon steel to which one or more alloying elements are added to obtain certain beneficial effects
The commonly added elements include silicon, manganese, nickel, chromium, molybdenum and tungsten
The term ‘alloy steels’ usually refers to ‘low’ alloy steels containing from 1-4% of alloying elements
Alloy steels have higher strength, hardness & toughness, higher hardenability, retain their strength & hardness at elevated temperatures, higher resistance to corrosion and oxidation

17. Engineering Material Alloy Steel
- Silicon increases strength & hardness without lowering the ductility. Silicon is added in spring steel to increase its toughness - Manganese increases hardness and toughness and also increases the depth of hardening - Nickel increases strength, hardness and toughness without sacrificing ductility - Chromium increases hardness & wear resistance, steel containing more than 4% chromium have excellent corrosion resistance - Molybdenum increases hardness & wear resistance, resists softening of steel during tempering and heating

18. Introduction To Machine Design
Standardization
Standardization is the 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 marketing, packing and storing of the product.
Following standards are used in Mechanical Engineering Design
Standards for materials, their chemical compositions, Mechanical properties & heat treatment

19. Introduction To Machine Design
Standardization
Standards for shapes and dimensions of commonly used machine elements
Standards for fits, tolerances and surface finish of component
Standards for testing of products
Standards for engineering drawing of components

20. Introduction To Machine Design
Preferred Numbers
The system is based on the use geometric progression to develop a set of numbers
There are five basic series denoted as R5, R10, R20, R40, and R80 series which increases in steps of 56%, 26%, 12%, 6% and 3% respectively
Each series has its own series factor as shown below

21. Thank you