Vibration Test Fixture

If you are the same poster as this one then I think you may have answered your own question.

i dont understand, whats wrong in being honest?

i am not representing my country but bunch of few people who are new to this industry and really confused. they want help and they are not afraid to ask for it.

if you cant help, please dont reply.

Proper design of a vibration test fixture for something as large as a car bumper is a VERY complicated issue that will require you to strongly understand physics, material properties of the fixture material and then the ability to design a fixture with zero weight (inertia) for use on the shaker system.

vibration testing of that particular item has been a challenge for years. Understanding the necessary energy involved in accelerating, decelerating and "shaking" not only the part, but also the fixture alone is a life challenge.

Understanding then how to reduce the weight of the fixtures without compromising the stiffness necessary is a science of itself.

Finding a shaker with adequate capacity will be a challenge, even in your home country.

I've seen huge sums spent on fixtures 1% of the size you will be dealing with.

I've seen fixtures disintegrate during test, since they have to support parts through multiple repetitions of the testing regiem as test item 1, then 2, then 3 up to 200 are tested. Those rigs cop a battering.

What acceleration profile are you to follow?

Is it random vibration or sinusoidal sweep?

Yes, a literature study is warranted, yes you will need to design the fixture (and probably re-design it many times) before even cutting material.

This is a real challenge.

Have fun.

thank you very much! you may not understand or you may find it silly but your reply was really a booster for me.

thank you very much again.

A few years ago I researched design for vibration testing for our products. Unfortunately the cost and time far outweighed the end result required so it was 'canned'. The field of vibration testing is very complex engineering project. Things to consider are weight, size, fixture, method of securing the object to the vibrator (especially difficult when considering using the same vibrator for different size, weight etc products), how will the vibrator machine be fixed to the ground without it drifting out the door or breaking the floor surface. Noise is also a huge factor. What length of time the test will undergo for the given product to prove it's design? Is the vibration to be in the x plane (one direction), x-y plane (two directions) or x-y-z plane (three directions). Add to is the complexity of the vibration in an elliptical motion.

This project will take months just to get an understanding of what's involved let alone the design, proof of design, building and even worse...the report writing of the results. You will need to show proof of why something passed or failed.

If i find some material (or links) i will post it...it's somewhere buried in my past position.

Thank you very much. I need to carry out test in x-y-z direction. we have only one common shaker bed. we will need to take sweep between 0 - 66 Hz.

but i l investigate more on the points you just gave me.

we are carrying out test according to AIS-006 standards.

we are trying to make a modular fixture if possible.

or at least a generalised procedure for making a fixture for bumper (of passenger cars of interest). this will help worker understand a drawing and it will save worker- engineer interaction time for manufacturing a fixture (which is very high in our company)

Industry relies more and more on modal analysis at the design stage to verify operation of components like bumpers. Yet, some contracts require test verification of the analysis. A vibration fixture is generally a large block of aluminum/magnesium alloy. It is made large to avoid modal response of its own, yet light to avoid having to use a giant shaker. It must accept the vehicle's bumper mounting hardware and be capable of being driven in all the specified test directions. If your shaker has a slip plate or can be tilted, the test procedure may be simplified. Check your test specifications carefully. Random vibration is generally a much better test for items such as bumpers that could have modes that interfere with each other. You are in for a treat.

start your literature search here. June/July 2010 issue of "TEST Engineering & Management" magazine. It has a very complete and comprehensive 2 page article detailing how to design vibration fixtures.

It is written by Danial L. Baughn of Baughn Engineering. I have personally purchased a vibration fixture from his company and I was very impressed.

It is a reprint of the same article from 2004. They said they have had so many requests for it they put it out again.

I can scan and deliver if you need.

Baughn Engineering is in La Verne, California, USA. I found them very helpful over the phone.

Thanks a lot! I got its link on internet, but not that article yet. But i will find it. It is available on sale.

Thanks a lot again.

If i don't get it here, in India, can you scan and email the copy of that article for me?