Click on Download Button to Download 22564 Elements of Machine Design Unit 3 Notes PDF
Certainly! Shafts, keys, and couplings are fundamental
components in mechanical systems, particularly in transmitting power from one
point to another. Here's an overview:
1. Shaft:
A shaft is a rotating machine element, usually circular in
cross-section, used to transmit power and motion.
Design Considerations:
- Material
Selection:
Common materials include mild steel because of its good tensile strength
and ability to handle torsion.
- Size
and Geometry:
Based on bending moments and torsional equations.
- Load
Type: Constant
or variable loads.
- Rigidity: Must be rigid enough to avoid
excessive bending or deflection.
- Bearings
and Supports:
The location and type affect the distribution of loads and moments.
- Assembly: Ease of attaching gears,
pulleys, etc.
2. Keys:
A key is a piece of metal used to connect the rotating
machine element to the shaft, preventing relative rotation.
Types:
- Square
and Rectangular (flat) keys: Common and used for positive drive without slipping.
- Woodruff
keys:
Semi-circular in shape and fit into a semi-circular keyway.
- Splines: A series of parallel keys
built integrally with the shaft.
- Tapered
keys:
Wedge-shaped from side to side and used where the hub is thin.
Design Considerations:
- Shear
and Compressive Stresses: Keys should withstand these stresses.
- Material
Selection:
Generally, keys are made from carbon steel.
- Length: Typically, the key length is
designed to be the same as the hub length.
3. Coupling:
A coupling is a device used to connect two shafts together
for the purpose of transmitting power.
Types:
- Rigid
Couplings: Used
when precise alignment is needed. Types include sleeve and flange
couplings.
- Flexible
Couplings: Can
tolerate some misalignment between shafts. Examples include universal
joints, gear couplings, and elastomeric couplings.
Design Considerations:
- Alignment: The capability of the coupling
to handle shaft misalignment (axial, radial, or angular).
- Torque
Transmission:
The coupling should handle the torque without failure.
- Ease
of Assembly/Disassembly: Especially important for maintenance.
- Protection: Some couplings provide
fail-safe operation, preventing damage to other equipment.
- Vibration
and Noise: The
coupling should not amplify vibrations or produce excessive noise.
General Design Considerations for All Components:
- Stress
Analysis:
Components should be designed to handle stresses without failure.
- Material
Selection:
Materials should match the purpose. For instance, coupling for a drive in
a corrosive environment might require corrosion-resistant material.
- Lubrication
and Maintenance:
Design for ease of maintenance and lubrication, especially for moving
parts.
- Environmental
Factors:
Consideration for elements like temperature, moisture, and corrosive
environments.
- Manufacturability: Considerations for ease and
cost-effectiveness of manufacturing.
- Safety
Factors: Always
include a factor of safety to account for unforeseen conditions or
inaccuracies in calculations.
Conclusion: