Podcast
Questions and Answers
What type of vibrations occur when the particles of the shaft move parallel to the axis of the shaft?
What type of vibrations occur when the particles of the shaft move parallel to the axis of the shaft?
- Torsional vibrations
- Radial vibrations
- Longitudinal vibrations (correct)
- Transverse vibrations
In which type of vibrations does the shaft experience bending stresses?
In which type of vibrations does the shaft experience bending stresses?
- Lateral vibrations
- Transverse vibrations (correct)
- Torsional vibrations
- Longitudinal vibrations
What type of stresses are induced in the shaft during torsional vibrations?
What type of stresses are induced in the shaft during torsional vibrations?
- Torsional shear stresses (correct)
- Radial stresses
- Bending stresses
- Tensile and compressive stresses
When the particles of the shaft move in a circle about the axis of the shaft, what type of vibrations occur?
When the particles of the shaft move in a circle about the axis of the shaft, what type of vibrations occur?
Which type of vibrations involve the shaft being elongated and shortened alternately?
Which type of vibrations involve the shaft being elongated and shortened alternately?
What happens to the shaft during transverse vibrations?
What happens to the shaft during transverse vibrations?
What is the term used to describe the speed at which the shaft runs so that the additional deflection of the shaft from the axis of rotation becomes infinite?
What is the term used to describe the speed at which the shaft runs so that the additional deflection of the shaft from the axis of rotation becomes infinite?
What causes the bending of the shaft with mountings such as gears or pulleys?
What causes the bending of the shaft with mountings such as gears or pulleys?
When does the additional deflection y of the shaft from the axis of rotation become infinite?
When does the additional deflection y of the shaft from the axis of rotation become infinite?
What is the unit of critical or whirling speed?
What is the unit of critical or whirling speed?
Which parameter determines both the value of eccentricity and the speed at which the shaft rotates?
Which parameter determines both the value of eccentricity and the speed at which the shaft rotates?
What happens to the shaft deflection if the circular frequency n is greater than the critical speed c?
What happens to the shaft deflection if the circular frequency n is greater than the critical speed c?
In a two-rotor system, when do torsional vibrations occur?
In a two-rotor system, when do torsional vibrations occur?
What point can be safely assumed as the fixed end of a shaft in a three-rotor system?
What point can be safely assumed as the fixed end of a shaft in a three-rotor system?
What does C represent in a three-rotor system's natural frequency equation?
What does C represent in a three-rotor system's natural frequency equation?
'The shaft behaves like a spring.' What resists the deflection of the shaft?
'The shaft behaves like a spring.' What resists the deflection of the shaft?
Study Notes
Types of Vibrations in Shafts
- Longitudinal vibrations occur when shaft particles move parallel to the axis.
- Bending vibrations cause the shaft to experience bending stresses.
- Torsional vibrations induce shear stresses in the shaft.
Circular and Alternating Vibrations
- Circular vibrations arise when shaft particles move in a circle about the axis of rotation.
- Axial vibrations involve the shaft being elongated and shortened alternately.
Effects of Transverse Vibrations
- During transverse vibrations, the shaft undergoes lateral oscillations, affecting its stability and performance.
Critical Speed and Eccentricity
- Critical or whirling speed is the term for the speed at which additional deflection from the axis of rotation becomes infinite.
- Eccentricity and the speed of rotation are determined by the same parameter, affecting the shaft's dynamic behavior.
Deflection Dynamics
- When the circular frequency (n) exceeds the critical speed (c), the shaft deflection increases significantly.
- Torsional vibrations in a two-rotor system occur when there is a relative motion between rotors.
Fixed Points and Natural Frequency
- In a three-rotor system, one end of the shaft can usually be assumed as fixed.
- In the natural frequency equation of a three-rotor system, C typically represents a constant related to system parameters.
Resistance to Shaft Deflection
- The resistance to deflection in a shaft is analogous to a spring's behavior, indicating elasticity and return to the original position.
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Description
Explore the three important types of free vibrations: Longitudinal, Transverse, and Torsional vibrations. Learn about vibrations in weightless constraints such as springs or shafts carrying heavy discs.
