Military Vehicle Body Mount Testing

Application Summary
A small test laboratory in Livonia, Mich. — a facility within the larger AM General operation that manufactures the HUMVEE^® military vehicle — has the primary mission to support its design and engineering departments. Among other activities, it supplies and maintains data acquisition systems used in new vehicle manufacturing, testing, and quality assurance. The lab also services continued-engineering projects assigned by various government agencies. Unlike the big three auto makers that have a separate laboratory for acoustics and another for vibration, or for that matter, one lab for each particular suite of measurements, AMG’s lab conducts all measurements required for all test functions. The wide range of parameters it measures includes load forces, strain gages, pressures, temperatures, accelerations, rpm, displacements, and a host of others.

Potential Solution
Before purchasing a data acquisition system, AM General engineers investigated two other large data acquisition system manufacturers that have been in business for many years. Units from both companies had a sufficient channel count to suit its needs, but their major drawback was their proprietary software. Says Mark Birecki, Development Test Supervisor, “You are tied to them forever because of it. We found other software suppliers that have a lot of good, flexible packages to offer, and we wanted the ability to try and use different ones when we felt we might have a special need.”

IOtech’s Solution
Birecki checked out the IOtech data acquisition system, the WaveBook^™ with a WBK14^™ dynamic signal conditioning module, WBK15^™ isolated signal conditioning modules, and a WBK16^™ strain gage module, and found the combination to be the best solution. “I like it because it’s small, compact, and you can use it to measure just about anything you can think of. The price is pretty reasonable, and best of all, IOtech is not software limited. We can use IOtech software or any one of the others currently on the market. These are the major reasons we purchased the IOtech WaveBook over the other two brands,” says Birecki. He uses a separate computer, a desktop or a laptop, and that gives him the ultimate flexibility he needs; it allows him to go with just about any kind of computer he prefers. Furthermore, Birecki was emphatic about his satisfaction with all the data he records, both the accuracy and the repeatability. He likes how easy the WaveBook is to use, and it’s portability, especially the fact that it runs on either ac in the lab or 12 VDC in the vehicle during road tests.

The real beauty of the instrument, claims Birecki, is that everything about it is fairly straightforward and simple to hook up, such as common types of connectors. And after learning the software, he was in business and ready to test in a couple of hours. The learning curve turned out to be quite minimal. The software Birecki uses is easy to load and he often monitors the data in real time, watching the waveforms change and stay within the intended range during the test. This lets him determine if the data right out of the box makes sense and it gives him a degree of confidence in the data before relegating it to automatic memory to study later.

For instance, the lab is now conducting a body mount study that includes measuring displacements. The LDVTs measure several displacement/strain levels on the frame, loads with a load cell, and accelerations with various types of accelerometers. It gathers and analyzes the data with an IOtech WaveBook, WBK14, WBK15 for rpm, WBK16, and signal conditioning modules over 24 analog channels.

Birecki runs tests in the desert and in frigid climates, so the test gear he uses must withstand these extreme temperature ranges. And he is satisfied with the ability of the WaveBook to withstand those extremes. Moreover, the WaveBook and modules are very durable; they withstand the shock, vibration, and the general all around bouncing experienced on road trips.

Conclusion
Two WaveBooks are used currently in AM General’s labs for testing HUMVEE military vehicles. The flexibility and number of channels they afford the test engineers rival the equipment capability of much larger, dedicated test labs that house separate acoustics and noise/vibration facilities. The WaveBook is less expensive than the dedicated software and hardware and provides the same or better accuracy and repeatability. Variables include load forces, strain gages, pressures, temperatures, accelerations, rpm, displacements, and numerous others that conveniently drive the signal conditioning modules interfaced to the WaveBook.