Fastener Vibration Testing

DES recently performed fastener vibration testing per MIL standard, MIL-F-25173A.  MIL-F-25173A is a military specification aimed at determining qualification criteria for aircraft fasteners and equipment.  In this case, DES focused on the vibration testing of a particular fastener to be used in aircraft applications.  Tests were conducted on DES’s Unholtz-Dickie Electrodynamic Shaker.  The MIL-F-25173A standard requires specimens to be subject to sinusoidal vibration testing, cycled between 10 and 55 Hz uniformly and with a constant 0.06 inDA displacement.  Tests shall span the course of 90 minutes over three perpendicular axes.

Cooling Fan Reliability Testing Case Study

Customer Challenge A customer approached DES looking to find an accelerated test solution for an AC powered cooling fan used in one of their products.  The product had been established in the marketplace and the company was now looking for ways to reduce cost by looking at different cooling fan suppliers.  Most fans, however, have a mean life rated for over 20,000 hours, so a typical accelerated life test would require a significant amount of time and money. 

ASTM D7386-12 Package Testing

DES recently performed package testing per ASTM standard, ASTM D7386-12. 

Choosing A Vibration Test Lab Part 2

Part 2 – Selecting a Lab and Performing Your Test If you have not done so yet, please check out Part 1 – Defining your project and  Obtaining a Quote. You obtained quotes from a couple of vibration test labs.  Your next task is to select a vibration test lab to perform your vibration test.  Your selection should not be based upon price alone.  Factors that should affect which lab you choose are capability, cost, timing, location, quality, and other special requirements.

Choosing A Vibration Test Lab Part 1

Part 1 – Defining your project and Obtaining a Quote Vibration testing is a very specialized field, not very well understood by many.  There are different types of vibration and there are an enormous number of vibration test specifications.  Vibration testing equipment is very expensive to purchase forcing many companies to hire a vibration test lab to fulfill their vibration testing requirements.  So what should you expect when Choosing A Vibration Test Lab?

Mixed Mode: Sine on Random Vibration Testing, RoR, SoRoR

Mixed Mode Vibration Testing is less common than Sinusoidal and Random Vibration Testing.  However, it does have a special purpose for simulating specialized helicopter vibration or vibration from tracked vehicles such as tanks. The three mixed modes of vibration testing are: Sine-on-Random (SoR) Random-on-Random (RoR) Sine-on-Random-on-Random (SoRoR) Some common test standards that have specifications for Mixed Mode Vibration Testing are: MIL-STD-810 Department of Defense Test Method Standard for Environmental Engineering Considerations and Laboratory Tests RTCA DO-160 Environmental Conditions and Test Procedures for Airborne Equipment

What is a Vibration Resonance?

A vibration resonance occurs when equipment or a product is exposed to an external forced vibration occurring at one or more of its natural frequencies.  The resulting product response vibration is amplified and can be huge!  Vibration resonances can cause severe damage to products and significantly shorten their life.  Examples of vibration resonances can be seen below and in our video page. A natural frequency is the frequency at which a system will oscillate after an external force is applied and then removed.  All objects have a natural frequency at which they vibrate.  Most products have many natural frequencies.

Vibration Response of Products

Vibration of a mechanical system can be descried as an oscillatory motion about an equilibrium point. Certain vibrations of mechanical systems can be considered desirable, such as in musical instruments like a tuning fork or guitar. However, often times vibrations of mechanical systems are undesirable, producing wasted energy, unwanted noise and catastrophic failures. Therefore it is critical during the product design phase that engineers are able to accurately characterize the vibration response of the system in order to ensure a safe and reliable product for their customers. We accomplish this through comprehensive vibration testing services.

Shock Testing: Long Duration Half Sine Shock

Shock testing with long durations can be a challenging endeavor. DES recently had to perform a 35G peak, half sine shock with a 50 millisecond duration. The video below shows this shock test being performed. This sounds like an easy shock to carry out because a peak of 35G is low compared to many shocks. However, this is a difficult shock to perform because 50 milliseconds is a long duration. Most typical shock durations are less than 20 milliseconds. A half sine shock impulse has the shape of a half sine wave. More details can be found elsewhere on our…

Altitude Testing: Low Pressure Vacuum Chamber

Altitude (Low Pressure) Testing makes use of a vacuum chamber to simulate the effects of high altitude conditions. The pressure inside the altitude chamber can be reduced to correspond to the air pressure at a specific altitude. Products can be placed inside the altitude chamber and tested to determine if they will still function after exposure to a given duration at a specified altitude. Components sealed with internal fluid such as batteries or capacitors may fail or leak during altitude testing because an internal pressure results at rising altitudes as the external pressure is reduced.  It is also possible to power a product during…