Theory and Design of Machine Elements
Course Objective:
After completion of this course, the students will be able to:
- Select proper mechanisms and analyze it for agricultural machines.
- Carry out simple design or modify the existing design for product development or repair and maintenance work.
- Know how the failure can take place on components of agricultural machines.
- Select the most appropriate machine elements by catalogue/data book references.
- Mechanism [4 hours]
- Introduction of mechanism
- Mechanism configuration, Link, pair and chain
- Degree of freedom of mechanism
- Inversion of mechanism – single slider crank mechanism
- Kinematic Analysis of Mechanism [8 hours]
- General plane motion representation
- Relative motion velocity analysis – Velocity polygons
- Velocity of any point on the link or outside the link [offset point]
- Velocity and angular velocity of different links
- Velocity and angular velocity diagrams of quadratic cycle chain and slider crank mechanism
- Velocity of rubbing at pin joints
- Instantaneous centers of velocity and Kennedy’s theorem
- Instantaneous center method to find out velocity of any link on quadratic cycle chain
- Acceleration diagrams of quadratic cycle chain and slider crank mechanism
- Centripetal, tangential and coriolis components of acceleration of a link
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Fundamentals of Machine Design [6 hours]
- Introduction to engineering design and design process
- Material properties and selection of material in m\ c design
- Theories of failures
- Endurance limit of materials
- Factors affecting fatigue strength
- Stress concentration effects
- Fatigue failure curves
- Factors of safety and basis for safety factor
- Use of data hand book for safety factor, design codes [ISI and ISO codes]
- Shaft, Axle, Keys and Shaft Couplings [5 hours]
- Functions application, type and material
- Combined bending and torsion effects
- Power and torque considerations
- Fatigue strength stress concentration and keyways effect
- Critical speed of shaft
- Design of keys
- Design of couplings
- Journal Bearing [6 hours]
- Types, application and material
- Journal bearing terminology
- Hydrodynamic theory of lubrication of rotating journal
- Viscosity, petroff’s law, bearing characteristic number
- Operating pressure load and heat balance of bearing
- Design procedure
- Ball and Roller Bearing [5 hours]
- Construction and types of ball bearing
- Design for variable loads and axial load
- Operating capacity of rolling element bearing
- Bearing load, life and reliability relationship
- Selection of bearings, lubrication, mounting and enclosure
- Gears [6 hours]
- Classification of gears and gear terminology
- Gear tooth profiles – Cycloidal and Involute
- Angle of obliquity
- Causes of gear tooth failure
- Design of spur gear considering static, dynamic and wear tooth load
- Helical, Bevel and Worm gear characteristic requirements for design
- Clutch and Brake [5 hours]
- Purpose, Type, Working principle and application of clutch
- Design steps for friction clutch – Multidisc and cone clutch
- Design basis of uniform wear and uniform pressure assumption
- Purpose, Type, Working principle and application of brake
- Design procedure for block brake
- Friction material and heat dissipation
- Operation system and control system
Practical:
- Pro-active learning approach: Each student will carry out a research project. S/he should write 4-8 pages summary on her/his topic and deliver it taking 10-15 minute time. The sample topic may be one of the following:
- Design for manufacturing
- Material selection for gear
- Design for assembly
- Optimal design
- Value engineering
- Patenting
- Bench marking
- Undertaking Design project: One team of the student will be 2 to 3 in number and it will complete a design project of a product on:
- A gravel conveyor
- A garage door opener
- A lifting device
- A maze planter
- A sprinkler
- A mechanical jack to lift and lower the load
- Live field project: Mechanical design related industrial problems as an assignment.
Tutorial:
- Problem solving on related topics.
- Old questions of TU examination will be the base for tutorial classes.
- Number of numerical examples in each chapter should be solved in the classes according to the weight-age given for TU final examination.
- Preference is to be given for applied type of questions that includes synthesis and analysis of real problem of machine design.
References:
- Theory of Machine and Mechanisms by J. E. Shigley and J. J. Uicker, Jr. McGraw Hill Publication, 1980.
- Mechanisms and Dynamics of Machinery, Fourth Edition by H. H. Mabie and C. F. Reinholtz, Wiley Publication.
Evaluation Scheme:
The questions will cover all the chapters of the syllabus. The evaluation scheme will be as indicated in the table below
Chapter |
Hours |
Mark Distribution* |
1 |
4 |
8 |
2 |
8 |
12 |
3 |
6 |
12 |
4 |
5 |
8 |
5 |
6 |
12 |
6 |
5 |
8 |
7 |
6 |
12 |
8 |
5 |
8 |
Total |
45 |
80 |
*Note: There may be minor deviation in marks distribution.
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