Comprehensive guide to vibration testing

Introduction to vibration testing

Vibration testing is a critical process in the validation of products, components, systems, or structures that subjects the item under test to mechanical motion. This process is designed to evaluate the response of the equipment under test to specific applied conditions. Unlike the brief mechanical forces applied during shock testing, vibration testing offers a prolonged and varied exposure to the applied excitation.

Why is vibration testing important?

Have you ever wondered why some products last longer than others? Or why some electronics fail after a minor drop, or slight rough handling? Vibration testing helps manufacturers understand these behaviours and make changes to ensure that their product can withstand real world conditions. This leads to better quality, reliability, and durability.
 

The mechanics behind vibration testing

Electrodynamic Systems: The heart of vibration testing

Electrodynamic systems, commonly referred to as an EDS, or a shaker, are the primary tools used in vibration testing. These shakers are capable of producing a wide range of precisely controlled vibrations, including

• Sinusoidal Vibration Testing : These are smooth repetitive oscillations, often used to test a specific frequency as part of an endurance test.
   
• Swept Sine Vibration Testing: These are sinusoidal vibrations that vary in frequency over time. This test is often used to identify specific critical frequencies.
   
• Random Vibration Testing: As the name suggests these are unpredictable in nature and do not follow a set pattern. These are often used to approximate real world conditions.
   

The essential components of any vibration test setup
 

A typical vibration test setup is comprised of several critical components:

1. Controller: This device manages the entire testing process. It ensures, through feedback from control accelerometers, that the shaker produces the desired vibration at the correct magnitude. Often the controller also performs data acquisition, recording measurements from accelerometers attached to the product. The data from these accelerometers allow us to identify resonances and critical frequencies which would require further testing.
    
2. Power Amplifier: This takes the signals from the controller and amplifies it to a sufficient level to drive the shaker to achieve the desired test levels.
    
3. EDS (Shaker): This is the heart of any vibration test setup. The shaker itself is not too dissimilar to an audio speaker, only much more powerful. The shaker consists of a moving armature, which oscillates within a set of coils. Head expanders or slip tables are attached to the armature, allowing for equipment to be mounted for test.
    
4. Fixtures: A fixture is a clamp or mounting that is used for securing the equipment under test to theshaker. It is important to ensure that the method of mounting equipment to a shaker is as close as possible to its real-world mounting. This ensures that the results of vibration testing are translatable to in service conditions.

Simulating real-world conditions

One of the primary objectives of vibration testing is to replicate the conditions a product may face during its lifespan. However, instead of taking years, these tests can condense the simulation into significantly shorter durations.

• HALT (Highly Accelerated Life Testing): This test is a rigorous reliability test that is used to quickly identify weaknesses in a product. Whilst the amplitude of the test might exceed real-world scenarios, the shape of the signal remains representative.

• ESS (Environmental Stress Screening): This test is designed to test products before they reach the market, making sure only the most robust make it through. This is commonly used when equipment is to be installed in hard-to-reach locations such as the sea floor, or when reliability is critical.

Axial testing

Axial testing is simply the breaking down of vibration into X,Y,Z axes and testing and measuring these individually.  Many product test standards call for testing to be conducted in this manner, as it is common for different orientations to be subjected to different levels of vibration in real world applications.

As you can see, Vibration testing is an indispensable tool in the arsenal of product developers and manufacturers. It ensures that the products you put to market are robust, durable and can withstand the harsh environments of real-world conditions. Being able to simulate years of product life in sort durations offers invaluable insights into product reliability and highlights any potential weak points. Axis Test Laboratories can offer a wide range of vibration tests to suit various industries and applications. Get in touch to discuss your vibration testing needs.

Get a vibration testing quote today.
 

Vibration testing FAQ’s

1. What products undergo vibration testing?
   Almost any product you can think of, from consumer electronics, marine equipment, equipment on trains and aircraft, and even equipment for military and space applications!
    
2. How long does a vibration test typically last?
   
   This varies depending upon the product, test type and applied test standards. It can range from a few minutes to multiple hours.
    
3. My product has anti-vibration mounts, do I still need vibration testing?
   
   Anti-vibration mounts are designed to reduce vibrations over specific frequency ranges. Outside of these ranges the product can still be affected by vibration. That is why it is important not just to test, but to ensure that the vibration mounts you are using are designed to work at the correct frequencies.
    
4. How do I choose a vibration test for my product?
   
   Choosing vibration standards can be confusing. Factors like the expected environment where the product will be used, the product's lifespan, and specific industry standards should be considered when choosing the test levels
    

5. What can be done to protect against vibration?
   There are some simple steps that can be taken:
    

• Make sure that all fasteners either have locking washers or a locking fluid added to the threads during assembly. This helps to ensure that nothing works loose during testing.
   
•  Heavy and tall components on printed circuit boards should be well supported with either a mechanical fixing or additional support to improve the rigidity. Components that are heavy or unsupported such as large electrolytic capacitors, are a common issue if not properly secured.
   
• Electrical connectors should be checked to be tight before undergoing vibration testing, as the small screws found in some connectors can work loose.
   
• Ensure that all bolts etc are correctly torqued to the correct level.
   

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