DES successfully completed a challenging combined temperature and vibration test which involved high G levels coupled with extreme temperatures! The vibration conditions required for this test were 10 to 2000 Hz, 20G maximum sinusoidal acceleration. These sinusoidal vibration tests were conducted during temperatures of -54°C and 200°C.
This is part two of a series of blog posts concerning the MIL-STD 810 Vibration Section. This blog was written with reference to MIL-STD-810G w/Change 1 dated 15 April 2014. DES has the experience and expertise to help you determine what profiles are appropriate for your product and to run your MIL-STD-810 vibration test. For more information, please check out Part 1 – MIL-STD-810 Vibration Testing Overview blog and our Vibration Testing services page.
Category 4 of Method 514.7 Vibration testing details the transportation random vibration environmental conditions from cargo interaction with vehicle suspension and structures with road and surface discontinuities. “This environment may be divided into two phases, truck transportation over US highways, and mission/field transportation. Mission/field transportation is further broken down into two-wheeled trailer and wheeled vehicles categories.”
Truck Transportation over US Highways Vibration Testing
This vibration test method is used when products or equipment will be transported by large trucks tractor-trailers commonly seen on US highways. The truck transportation over US highways random vibration profile is designed to simulate 1609 km (1000 miles) on interstate highways. The random vibration profile along each axis can be seen in the plot below in Figure 1. The length of this profile is 60 minutes per axis for each 1000 miles of transportation. For example to simulate 2000 highway miles, the vibration test duration would be 2 hours per axis x 3 axes = 6 hours total.
This is part one of a series of blog posts discussing MIL-STD 810 Vibration Testing. This blog was written with reference to MIL-STD-810G w/Change 1 dated 15 April 2014. DES has the experience and expertise to help you determine what profiles are appropriate for your product and to run your MIL-STD-810 vibration test. Check out our vibration testing capabilities here.
MIL-STD-810 is a public military test standard that is designed to assist in the environmental engineering considerations for product design and testing. For the purposes of this blog series we will focus on Method 514.7, titled Vibration. This section defines the environmental vibration conditions a material or product may experience during the product life cycle and translates these conditions into replicable test procedures. Unfortunately, unless you’re familiar with this document, this section or any section for that matter may seem a little daunting. This blog will hopefully provide some guidance into navigating your way through it.
DES recently performed qualification testing on aerospace connectors which involved combined temperature and sinusoidal vibration testing, random vibration testing and shock testing. Combined temperature and sinusoidal vibration tests were performed per EIA 364-28F. EIA 364-28F required test conditions of 10-2000 Hz, 20G maximum acceleration sweeps at temperatures of -54°C and 200°C over the course of 4 hours per axis. Random vibration tests were also performed per EIA 364-28F. Random vibrations at 50-2000 Hz, 46.3 Grms were applied to the connectors for 8 hours per axis. The random vibrations were applied at room temperature. Finally, the connectors were subjected half sine shocks per EIA 364-27C. The shock requirements were three shocks per polarity, per axis at 300G over the duration of 3msec. A sample shock plot can be seen in Figure 1.
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. Continue Reading Fastener Vibration Testing
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. Continue Reading Choosing A Vibration Test Lab Part 2
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 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
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.