High "G" Shock Testing
Unholtz-Dickie announces a new family of “high g” shock test systems featuring the Model S092-UX Shaker rated up to 1500 g pulse output.
Why were S092 Systems developed by UD?
Prior to the introduction of S092 Systems, high g shock tests have been performed primarily with drop towers or pneumatically assisted shock tables which rely on mechanical impact to generate the necessary acceleration pulse. These impact shock test machines have several shortcomings, including:
- Poor repeatability of peak g amplitude from one pulse to another
- Mechanical "ringing" at the end of the test pulse
- Limited ability to produce short duration pulses (< 1 ms duration)
Moderate level shock pulse testing has been performed with electrodynamic shakers for many years. But until recently 100 - 150 g's was considered a fairly respectable shock pulse on a shaker. For many shakers, higher shock g levels meant broken armatures, expensive repairs and down time.
Unholtz-Dickie has made important advancements in shaker armature design which permit the use of substantially higher Power Amplifier drive levels without sacrificing armature durability. High output Power Amplifiers in combination with improved armature designs now permit major increases in peak g shock amplitudes previously reserved for drop towers or pneumatic shock tables. See below.
|Shaker||Power Amplifier||Max g 1/2 sine||Duration||Payload|
|350 g||0.5 ms||2.0 lbs|
Performance graphs showing the full range of rated acceleration (g-pk) for various pulse durations and payloads are available from UD.
Improved Pulse Characteristics
Because the shock pulse acceleration is generated electrodynamically (no mechanical impact), the test pulse waveform is readily controlled using acceleration feedback and digital signal processing techniques. The APEX SL Digital Controller was used to program the shock pulse in Figure 2.
Note the tightly controlled waveform and the lack of mechanical "ringing" at the pulse end point. Similar pulse quality can be achieved with sawtooth, trapezoidal and many other waveforms including captured time histories (field data).
The pulse amplitude (g pk) is controlled by varying the drive voltage applied to the electrodynamic shaker armature coil. Therefore, peak amplitude repeatability is extremely good using a closed-loop controller such as the APEX SL. Similarly, extremely small changes in pulse amplitude can be achieved, making threshold limits of the device under test easy to measure.
Fast Pulse Rates / Reduced Test Time
Pulse repetition rates using an electrodynamic shaker under closed-loop control are comparatively rapid since no mechanical "resetting" of the shaker is required between pulses.
Example: 500 test pulses can be produced in a few minutes. A similar series of pulses using a drop tower could easily take many hours or even days depending on test setup complexity such as attached cables, specimen geometry, etc.
2XSAI120-S092-UX Shock Test System
This all air-cooled system includes the Model S092-UX Shaker driven by the 2XSAI120 Power Amplifier rated at 240 KVA output. The 7" diameter armature is well suited for small payloads such as disk drives, airbag sensors, aerospace components and other devices that must operate in high shock environments.