×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

#### Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
• Talk With Other Members
• Be Notified Of Responses
To Your Posts
• Keyword Search
• One-Click Access To Your
Favorite Forums
• Automated Signatures
On Your Posts
• Best Of All, It's Free!
• Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

#### Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

# Resonance in Balded Disk

 Forum Search FAQs Links MVPs

## Resonance in Balded Disk

(OP)
i would highly appreciate if someone could clear my doubt regarding resonance condition of a cyclic structure (say Bladed disk). Most of the articles mention two conditions to be respected:
matching frequency ( excitation force and natural frequency)
matching nodal diameter of the structure with force shape (m=k).
My question is linked with the second condition
i have found in some papers this condition more completely mentioned in the form
k = Nn + m and k = Nn- m.
where N is the number of blades and n = 0,1,2,3...

which shows that a positive work can be done on a bladed disk even when the shape of the force is larger than N/2 on a
lower nodal diameter.Can someone explain this?

Is this applicable to a particular kind of bladed disk (say packeted bladed disk) or it is applicable in general to any configuration of bladed disk?

Regards
Rajesh Kachroo
Alstom Power

### RE: Resonance in Balded Disk

I'm not familiar with the equations that you posted, maybe the referenced paper was specific to a particular kind of bladed disc.

My experience is that the nodal diameters are calculated using modal analysis (FEA), then plotted versus the forcing function (nozzle/vanes and operating speed) via a safe diagram to see which mode shapes align with the forcing function in the operating range. Even though the mode shapes/frequencies change with the blade count, they are not directly related to the modal frequencies to the point that a simple equation as listed above could be used.

Maybe you could link the paper referenced?

#### Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

#### Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

### Reply To This Thread

#### Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login

#### Resources

White Paper - Addressing Tooling and Casting Requirements at the Design Stage
Several of the tooling and casting requirements of a part can be addressed at the design stage. If these requirements are not addressed at the design stage, lot of time is spent in design iteration when the design reaches the die caster. These design issues lead to increase in time and cost of production leading to delay in time to market and reduced profits for the organization. Download Now
White Paper - The Other Side of Design for Assembly
Assembly level constraints need to be satisfied before the design can move downstream. This white paper will go through the various assembly level issues, which need to be tackled by various organizations on a regular basis. Know more about DFMPro, a design for assembly software. Download Now

Close Box

# Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

• Talk To Other Members
• Notification Of Responses To Questions
• Favorite Forums One Click Access
• Keyword Search Of All Posts, And More...

Register now while it's still free!

Already a member? Close this window and log in.