Vibration Blog

Introduction

Like all companies, we get many enquiries.   And we get many questions too.

On this page we address:

  • FAQ (Frequently Asked Questions) from customers,
  • Lessons learnt (discovered after the project ended), and
  • Case studies of the work we've completed.

If you have any questions about your company challenge or about ours, please fill in the form by clicking Contact Form

Vibration Case Studies

Please click on the title in which you interested.

  • Test fixture, motor failure and analysis
  • Vibration and fatigue

  • Vibration and electronics, i.e. capacitors that fail, and why?

  • Resonance - and blade pass frequencies

  • Sterling engine

  • Rotating equipment vibration

  • Steering column: finite element updating using modal data

  • Engine transmits high vibration levels across the AV mount.

  • Vibration isolation without AV mounts

Test fixture, motor failure and analysis

A thrust reverser actuator electric motor was failing during the vibration test.

In this discussion we highlight a few key concerns on product design and test fixture design. As you read through this case study, you'll get a feel for what is overlooked in engineering and testing.

Test fixture

In this case study the test fixture was very bulky and unnecessarily large and heavy.

When it came to testing, smaller shakers could not handle to heavy fixture. And finding a shaker to accommodate the test was time consuming and limited.

So, from this experience we highlight the following:

  • the smaller and lighter the fixture, the more flexible you can be with where you want to test and

  • the more available the shaker will be, and

  • remember the cost is proportional to the size, i.e. the force rating, of the shaker, and you can save on the shaker cost

The motor design itself

But the most important aspect of this test was the design of the motor.

The motor had two main bearing housings at either end. Not very thick, as when one designs equipment for a plane. weight is against you. So the lighter, the better. if it’s overweight, there are financial penalties.

During testing, acceleration levels of over 2000m.s^2 were seen. This was short lived, as the accelerometers detached under these acceleration levels.

Comparing the response measurements, it was evident that the end housing was behaving like a spring.

Like the diaphragm in a loudspeaker. This caused high bending and flexing of the end housing, causing cracks in the aluminium.

The recommendation was to increase the draught angle of the end housing. And to include stiffener ribs on the out surface.

But what puzzled us was that this behaviour was not noticed in the analysis results. As conducting finite element analysis on this motor. would have flagged this behaviour.

Was this profile not given to the designers?

So, this demonstrates the importance of updating analytical models with actual measurement data.