Sensitive Equipment Vibration and Shock Testing
At a glance
Military vehicles are operated in severe conditions, so experience vibration and shock events which could limit the safe transport of sensitive equipment. These inputs can be measured and assessed by Millbrook using an instrumented vehicle as per Def-Stan 00-35 Part 5.
By performing these assessments, the customer was able to understand and identify any required changes to the vehicle to improve the conditions of stowed items. Shock and vibration test data was collected using tri-axial accelerometers. Millbrook collected data from multiple vehicles on several special surfaces at its proving ground. Surfaces were used to generate repeatable inputs which were representative of severe vehicle usage.
Def Stan 00-35
Time history data was processed and assessed to illustrate the vibration environment experienced at multiple locations around the vehicles. Random vibration exposure was measured and shock assessments were made against definitions provided by Def Stan 00-35 Part 5. These were used to generate a comparable test specification for each of the vehicle location measured. Shock events were also identified.
10 different vehicles were tested and measurements for vibration and shock were taken at a number of stowage locations to calculate exposure severity. The number of channels required differed dependent on the vehicle, with up to 191 channels recorded simultaneously at a sampling rate of 50kHz.
“The reports were well written and easy to follow. It was good to see some alternative methods of presenting the data”
Vibration Data Collection and Analysis
During data collection, vehicles are driven following clearly defined test instructions to ensure repeatability. nCode Glyphworks was used to process and analyse the data. Visual analysis and statistical techniques were used to ensure assessments conformed to the methods provided in the standard.
The random vibration test specifications were generated through PSD plots derived from the vehicle data using Stationary and Gaussian time histories. The PSD levels were enveloped for each location and the equivalent test durations were calculated based on the Palmgren-Miners Rule, as described in the standard. Shock events were identified in the time history data and converted to an equivalent shock response spectrum.
Customers were provided with a full test report including environmental description, a Random Vibration test specification and shock severity data.