Frequency Analysis of a rotating shaft

AIM: Frequency Analysis of a Rotating Shaft

Objectives of the project:

1. To create a 3D model of given component in solidworks.
2. To find the critical frequency of a rotating shaft.

Introduction:

Critical Speed of the Shaft:

In the field of rotor dynamics, the critical speed is the theoretical angular velocity which excites the natural frequency of a rotating object, such as a shaft, propeller or gear. As the speed of rotation approaches the objects natural frequency, the object begins to resonate which dramatically increases system vibration. The resulting resonance occurs regardless of orientation. . When the rotational speed is equal to the numerical value of the natural vibration, then that speed is referred to as critical speed

Whirling speed is also called as Critical speed of a shaft. It is defined as the speed at which a rotating shaft will tend to vibrate violently in the transverse direction if the shaft rotates in horizontal direction. In other words, the whirling or critical speed is the speed at which resonance occurs. Whirling Speed is due to the unbalanced forces acting on a rotating shaft.

Resonance Frequency:

Resonance describes the phenomenon of increased amplitude that occurs when the frequency of a periodically applied force is equal or close to a natural frequency of the system on which it acts. When an oscillating force is applied at a resonant frequency of a dynamical system, the system will oscillate at a higher amplitude than when the same force is applied at other, non-resonant frequencies.

Resonant frequency is the oscillation of a system at its natural or unforced resonance. Resonance occurs when a system is able to store and easily transfer energy between different storage modes, such as Kinetic energy or Potential energy as you would find with a simple pendulum. Most systems have one resonant frequency and multiple harmonic frequencies that get progressively lower in amplitude as they move away from the center.

Geometry of the Model:

3D Part Model of Rotating Shaft:

Procedure:

• Create a 3D model of given component in solidworks.
• Then go to solidworks simulation and perform a new study on frequency analysis.
• Then apply the material as alloy steel to the component.

• Apply a bearing fixtures on the stepped face of the rod at the two ends.

• Now, apply a basic mesh and then run the simulation to perform analysis.

Results:

• Mode 1(Frequency Amplitude 1):

• Mode 2(Frequency Amplitude 2):

• Mode 3(Frequency Amplitude 3):

• Mode 4(Frequency Amplitude 4):

• Mode 5(Frequency Amplitude 5):

• The different resonance or critical frequencies obtained are as follows as: