1. Machine Design

2. PR352: Machine Design (Teaching Load: Theory – 4 hrs, Practical – 2 hrs. 5 Credit) INTRODUCTION Mechanical Engineering design, Traditional design methods, Design synthesis, Aesthetic considerations in design, Ergonomic considerations in design, Use of standard in design, Selection of preferred sizes, value analysis, Engineering materials, Selection of materials, manufacturing considerations in design, statistical considerations in design DESIGN OF MACHINE PART SUBJECTED TO STATIC LOAD Modes of failure, F.O.S., Stress due to B.M., stress due to torsional moment, Eccentric axial loading, combined stress: Direct and bending e.g. C- clamp, frame, screw press, frame etc. DESIGN OF MACHINE PARTS SUBJECTED TO FLUCTUATING LOAD Stress concentration, stress concentration factors, methods to reduce stress concentration effects, fluctuating stresses, fatigue failure, notch sensitivity, endurance limit, Rotating beam test. Fatigue strength, factor affecting fatigue strength, Soderburg, and Goodman diagram, S.N. diagram, cumulative damage in fatigue: - Miner’s equation. POWER SCREWS Forms of threads, force analysis of square threads and trapezoidal threads, self locking in power screws, collar friction, stresses in screw, Differential and compound screws, Recirculating type ball screws.

3. SHAFTS, KEYS AND COUPLINGS: Transmission shafting, Design against static load and torsional rigidity, keys: Design of various types of keys, couplings: design of rigidity and flexible couplings. FRICTION CLUTCHES: Torque transmitting capacity, single disc and multiple disc clutches, fraction materials, cone clutches, centrifugal clutches. GEARS: Types of gears, V.R. for each type, selection of types of gear, modes of failure, gear design for maximum power transmitting capacity, Design of spur and helical gear, Lewis equation, Buckinghum’s Equation, Wear strength of spur & helical gears, gear lubrication. BELT DRIVES : Flat and V- belts, belt conformations, geometrical relationships, ration of belt tension, stress in belt, selection of V. belt and flat belts, condition for maximum power transmission.

4. Course Outcome:
At the end of course students will able to Appreciate basic design procedure, and various design considerations.
Define, describe and distinguish static and fluctuating loads/stresses.
Solve numerical problems for safe design under static and fluctuating loads/stresses.
Design gears, clutches, power screws etc. for real life applications.

5. Introduction to Machine Design

6. Machine Design:
“ 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”

7. Design Process

8. Basic Requirements of Machine Element:
Strength
Rigidity
Wear Resistance
Min. Dimensions and weight
Manufacturability
Safety
Conformance of standards
Reliability
Maintainability
Min. Life cycle cost

9. Basic Procedure of Design of Machine Element
Specify Functions of Element
Determine Forces Acting on Element
Select Suitable Material for Element
Determine the failure mode of Element
Determine Geo. Dimensions of Element
Modify the dimensions for Assembly and manufacture and
Check Design at critical Cross sections
Prepare Working Drawing of Element

10. Design synthesis
Defined as the process of creating or selecting configurations, materials, shape and dimensions for a product.
Decision making process with objective of optimization.
Difference between design analysis and design synthesis.

11. Design synthesis In design synthesis the designer has fix objective.
Objective can be min. cost, min. weight, or volume, max. reliability or max. life.
Mathematical formulation of these objectives and requirements.
Final step is mathematical analysis for optimization and interpretations of these result.

12. Concurrent Engineering:
Conventional Design Process.

13. Concurrent Engineering:
“ Concurrent Engineering is defined as the design process that brings both design and manufacturing engineers together during the early phases of the design process.”

14. Aesthetic Considerations in Design
Each product has definite purpose.
It has to perform specific functions to the satisfaction of customer.
The contact between product and people is arises due to sheer necessity of this functional requirement.
E.g. Automobile Car, domestic refrigerator.

15. Aesthetic Considerations in Design
When there are a number of products in the market having same qualities of efficiency, durability and cost, customer attracted towards the most appealing product.
External appearance is an important feature.
The growing realization of the need of the aesthetic considerations in product design has given rise to a separate disciple known as ‘Industrial design’.

16. Aesthetic Considerations in Design
The job of an industrial designer has to create new forms and shapes, which are aesthetically pleasing.
There are five basic forms;
Step form
Stream or stream line form
Taper form
Shear form
Sculpture form

17. Aesthetic Considerations in Design
The ‘step form’ is similar to the shape of ‘skyscraper’ or multistory building.
This involves shapes with a vertical accent rather than a horizontal.
The ‘stream or streamline form’ is seen in automobiles and aeroplane structure.
The ‘taper form’ consists of tapered blocks interlocked with tapered plinth or cylinders.
The ‘shear form’ has a square outlook, which is suitable for free standing engineering product.

18. Aesthetic Considerations in Design
The ‘ Sculpture form’ consists of ellipsoids, paraboloids and hyperboloids.
The sculpture and stream forms are suitable for mobile products like vehicles.
Step and shear forms suitable for stationary products.

19. Aesthetic Considerations in Design
There is relationship between functional requirement and appearance of the product.
Selection of proper colour is an important consideration in product aesthetics.
The choice of colour should be compatible with the conventional ideas of the operator.
Many colours are associated with different moods and conditions.

20. Aesthetic Considerations in Design
Meaning of colours:
Colour
Meaning
Red
Danger- Hazard-Hot
Orange
Possible danger
Yellow
Caution
Green
Safety
Blue
Caution-Cold
Grey
Dull

21. Aesthetic Considerations in Design
The external appearance of the product does not depend upon only the two factors of form and colour.
It is cumulative effect of a number of factors such as,
Rigidity and resilience, tolerance and surface finish, motion of individual components, materials, manufacturing methods and noise.

22. Aesthetic Considerations in Design
The industrial designer should select form which is in harmony with the functional requirements of the product.
The economics and availability of surface-treating processes like anodizing, plating, blackening and painting should be taken into account before finalizing the external appearance of the product.

23. Standards and Standardization:
Standard is a set of specifications, defined by a certain body or an organization, to which various characteristics of a component, a system, or a product should conform.
The characteristics may include: dimensions, shapes, tolerances, surface finish etc.

24. Standards and Standardization:
Types of Standards Used In Machine Design:
Based on the defining bodies or organization, the standards used in the machine design can be divided into following three categories:
Company Standards: These standards are defined or set by a company or a group of companies for their use.
National Standards: These standards are defined or set by a national apex body and are normally followed throughout the country. Like BIS, AWS.
International Standards: These standards are defined or set by international apex body and are normally followed throughout the world. Like ISO, IBWM

25. Standards and Standardization:
Selection of Preferred Sizes French balloonist and Engineer Charles Renard suggested the method to specify the sizes of the product to satisfy the needs of the customers with the minimum number of sizes in the given range by using the G.P. He gave the five basic series having their specific series factor as follows:
Series
Series Factor
R–5
5 10
R-10
10 10
R–20
20 10
R-40
40 10
R-80
80 10

26. Standards and Standardization:
ADVANTAGES OF SELECTION OF PREFERRED SERIES:
1. The differences in two successive terms have a fixed percentage.
2. Provides small steps for small quantities and large steps for the large quantities. It is in conformance with the mode of variation found in nature.
3. The product range is covered with minimum number of sizes without restricting the choices of the customers.
4. It helps the designer to avoid the selection of sizes arbitrarily.

27. B.I.S DESIGNATIONS OF THE PLAIN CARBON STEEL:
Plain carbon steel is designated according to BIS as follows:
1. The first one or two digits indicate the 100 times of the average percentage content of carbon.
2. Followed by letter “C”
3. Followed by digits indicates 10 times the average percentage content of Manganese “Mn”.

28. B.I.S DESIGNATIONS OF ALLOY STEEL:
Alloy carbon steel is designated according to BIS as follows:
1. The first one or two digits indicate the 100 times of the average percentage content of carbon.
2. Followed by the chemical symbol of chief alloying element.
3. Followed by the rounded off the average percentage content of alloying element as per international standards.
4. Followed by the chemical symbol of alloying elements followed by their average percentage content rounded off as per international standards in the descending order.
5. If the average percentage content of any alloying element is less than 1%, it should be written with the digits up to two decimal places and underlined.

29. Ergonomics Considerations
Ergonomics is defined as the relationship between man and machine and the application of anatomical, physiological and psychological principles to solve the problems arising from man machine relationship.
Ergonomics means natural laws of work

30. Ergonomics Considerations
From design considerations, the topic of topics of ergonomic studies are as follows:
Anatomical factors in the design of drivers seat.
Layout of instrument dials and display panels for accurate perception by the operators
Design of hand levers and hand wheels.
Energy expenditure in hand and foot operations.
Lighting, noise and climatic conditions in machine environment.

31. Ergonomics Considerations
The ergonomics considerations in the design of controls are as:
The control should be easily accessible and logically positioned.
The control operation should involve min. motions and avoid awkward movements.
The shape of control component, which comes in contact with hands, should be in conformity with anatomy of human hands
Proper colour produces beneficial psychological effects.