Frequency Analysis of a rotating shaft

AIM:

Frequency analysis on rotating shaft using Solidworks.

Objective:

Frequency analysis on rotating shaft by applying bearing fixture on stepped face of the rod at the two ends to find out critical frequencies of a rotating shaft for the 5 mode shapes on the following type of materials:

*Alloy Steel

*AISI 1018 Steel (Custom material).

Procedure:

*Obtain the required model by creating the two part geometries and then assemble it.

*Specifications of Part 1(Shaft):

Total length = 1000mm

Stepped length on both sides = 50 mm

Outer diameter of rod = 120mm

Smaller stepped diameter of rod = 60mm.

Part 1(Shaft)

*Specifications of Part 2(Disc):

Outer diameter = 600mm

Inner diameter = 120mm

Thickness = 100mm.

Part 2(Disc)

*In assembly by using profile center in advance mate, disc is assemble on shaft at the center of the shaft.

Assembly

*Now apply the frequency analysis on the model to obtain the critical frequncies.

*In fixture, fix the model by using bearing fixtue fixture on stepped face of the rod at the two ends and allow the self-alignment for the rotation of shaft about its original axis.

Rotating shaft with bearing fixture

*Select the Alloy Steel as material and create the mesh.

*Run the analysis for the 5 mode shapes.

*Repeat the same procedure in new simulation of frequency analysis for AISI 1018 Steel.

Mode Shape 1

*From mode shape 1 it is observed that, the vibration of the model is along its own axis and it is very much less due to two rigid nodes at the two end. Hence, stimulation of frequency is less.

Mode Shape 2

*In this, the vibration of the model is in X-axis direction which is held between the two nodes. This vibration is clearly understand by Animate the model and stimulation of frequency is more than the Mode shape 1.

Mode Shape 3

*In mode shape 3, the vibration of the model is in Y-axis direction which is held between the two nodes. The stimulation of frequency is identical to Mode shape 2.

Mode Shape 4

*Mode shape 4 has 3 nodes i.e. two at the end and one at the center along the Y-axis. Hence, the vibration of the model is in Z-axis direction and the stimulation of frequency is more than Mode shape 2 & 3.

Mode Shape 5

*Mode shape 4 has 3 nodes i.e. two at the end and one at the center along the X-axis. Hence, the vibration of the model is in Z-axis direction and the stimulation of frequency is identical to Mode shape 4.

*Results of Frequency analysis of the AISI 1018 Steel is similar in movement of model but the values of stimulation of frequencies are different.

Result & Conclusion:

*Frequency analysis on rotating shaft is done successfully & their results of resonant frequencies of 5 mode shapes for Alloy Steel & AISI 1018 Steel material are as follows:

Mode Shape	Alloy Steel			AISI 1018 Steel
	Frequency (Rad/sec)	Frequency (Hertz)	Period (Seconds)	Frequency (Rad/sec)	Frequency (Hertz)	Period (Seconds)
Mode 1	0.060588	0.0096429	103.7	0	0	1×1032
Mode 2	743.45	118.32	0.0084514	716.71	114.07	0.0087667
Mode 3	743.76	118.37	0.0084479	717.01	114.12	0.008763
Mode 4	2220.2	353.36	0.00283	2141.2	340.78	0.0029344
Mode 5	2221.4	353.55	0.0028285	2142.4	340.97	0.0029328

Graphical representation of Frequncy vs. Mode No(Alloy Steel)

Graphical representation of Frequncy vs. Mode No(AISI 1018 Steel)

*Frequency is the one of the factor which cannot be modified. Therefore, this parameter are very important while designing the structures because when body vibrates at thier natural frequency(resonant frequncy) it causes failure in structure of element.

*Natural frequency is depends upon the two factors stiffness & mass.

*Natural frequency increases by increasing stiffness or by decreasing the mass.

*From both the analysis it is observed that, the stimulation of frequency is more in Alloy Steel as compared to AISI 1018 Steel. Hence, Alloy Steel is suitable for designing the rotating shaft.