Frequency Analysis of a rotating shaft

AIM

We have to find out the critical frequencies of a rotating shaft in Solidworks. We have to create the model in Solidworks according to dimensions that you see fit. Model it in Solidworks according to the image shown below

Conduct a frequency analysis and apply a bearing fixture on the stepped face of the rod at the two ends and perform the analysis.

Find out 5 mode shapes and list the resonant frequencies

INTRODUCTION

Natural frequency Analysis or modal analysis is carried out to understand the dynamic behaviour of a system

It helps to eliminate or reduce the vibration caused in a component / structure

Vibration are caused because of the dynamic loading and it leads to fatigue failure in a structure

Every component / structure have their own natural frequency when the excitation frequency created because of the load meets the natural frequency the system will fail

Natural frequency analysis

Component / structure will deform is a shape called mode shape when a excitation frequency meets the natural frequency

The process of calculating the natural frequency analysis and the modes shapes is called frequency analysis or modal analysis

Rotor dynamics is the part of modal analysis which is used to analyse the rotary system

Modes and Mode Shapes

Mode is a shape at which the structure absorbs energy supplied by an excitation

Mode shape depend on the geometry ,constraints and the material properties

There are two types of modes

• Rigid body modes

• Flexible modes

Types of Modal analysis

• Unconstrained Modal analysis

A unconstrained component will have 6 DOF in a 3D space .if a Nodal analysis is Carried on such types of component the first 6 mode frequency will be zero and are called as rigid body modes

These modes represent the three translation and rotation of a system

• Constrained modal analysis

A constrained modal analysis will have zeo DOF this analysis will have non zero value are called as flexible modes

If any zero frequency mode is obtained its source is identified and constrained

RESULTS

Some mode shape give same resonant frequency

From the analysis and the study we can conclude that rotating shaft is a flexible modes

During animation the first amplitude vibrates along y direction and second amplitude vibrates along x direction and so on.so due to this reason we obtain a flexible modes

From the most of the vibration taking place on the middle that is on the wheel or the circumference of the wheel as the rotation frequency of shaft increase which will increase in resonant frequency

As we know the resonant is addition of natural frequency and excitation frequency we leads to failure

So this is one type of application to determine the frequency analysis of mechanical body

Before use in the machinery