Mechanical Shock Testing and Shock Measurement Systems

What is mechanical shock testing?

Mechanical shock testing subjects a product to a controlled transient acceleration and measures how it responds. The goal is qualification: proving a component survives the shocks it will meet in service, or finding the level at which it stops surviving.

It is the counterpart to vibration testing rather than a variant of it. Vibration is sustained and repetitive, and damage accumulates over hours of exposure. Shock is a single transient event, and damage happens in milliseconds. Shock and vibration testing programmes normally run both, because a product can pass one and fail the other — but the measurement demands are different. Vibration asks for dynamic range over long records; shock asks for bandwidth and headroom in a window a few milliseconds wide.

Classical shock pulses

The simplest shock tests use a defined pulse shape: a half-sine, haversine, terminal-peak sawtooth or trapezoidal pulse, specified as a peak g level over a given duration in milliseconds. A classical shock pulse is repeatable, easy to specify and easy to verify, which is why most equipment-level standards are written around them. A half-sine shock pulse at 50 g for 11 ms is a typical transit-drop requirement.

Complex transients

Pyroshock, ballistic shock and underwater explosion are not describable as a pulse shape. They are dominated by high-frequency structural response, they differ every time, and two events with the same peak g can do entirely different damage. These are specified as a shock response spectrum instead — a curve of damage potential against frequency, rather than a single number.

What you measure in a shock test

• Acceleration is the primary measurement, taken with accelerometers mounted at the points where the shock enters the structure and at the components you care about. Mounting matters more here than anywhere else in dynamic testing: a resonance in the mount shows up as signal, and once it is in the data it cannot be separated out.

• Pressure is measured alongside acceleration in blast, ballistic and underwater shock, where the loading mechanism is the pressure wave rather than a mechanical contact.

• Strain and force show how the shock is transmitted into the structure, and are what connect a measured event to a fatigue or failure analysis.

• High-speed video, synchronized to the data, is what turns an unexpected result into an explanation — a fixture slipping, a cable whipping, a component contacting something it should not.

All of these record on one time base in Dewesoft systems, which is what makes it possible to say that a strain peak and a video frame and an acceleration spike belong to the same instant.

Shock testing hardware

High-speed DAQ for high-frequency shock

SIRIUS® XHS covers the fastest transients — pyroshock, ballistic events, blast — where the energy sits far above conventional DAQ bandwidth. It samples at up to 15 MS/s per channel with bandwidth to 5 MHz, and its HybridADC gives you a choice per measurement: a high-bandwidth mode when the peak is what matters, or alias-free acquisition up to 2 MS/s when you need the dynamic range to resolve a small response riding on a large event.

SIRIUS® XR is the same front end at scale. Large shock programmes rarely need extreme bandwidth on every channel — a few points sit directly on the shock path and need everything XHS can give, while strain, pressure and secondary accelerometers are well served at lower rates. XR combines XHS and SIRIUS® X modules in a single 19-inch rack: up to 288 analog channels in the XR9, of which up to 72 can be high-speed XHS channels, and up to 160 in the XR5. Both kinds of channel share one time base instead of running as two systems you have to align afterwards, and racks daisy-chain or star-connect when one is not enough.

The XR chassis is itself rated to 75 g shock — worth knowing when the DAQ is mounted on or near the structure being tested rather than safely across the room.

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Modular systems for mixed shock programmes

SIRIUS® Modular and SIRIUS® Mini handle the drop, impact and transit testing that makes up most shock work, with charge and IEPE conditioning on the same chassis as strain, pressure and voltage. Channel counts scale from a handful to several hundred without changing software.

Distributed systems for large structures

Shock on a large structure — a full-scale airframe, a ship section, a bridge, a launch vehicle — happens across tens of metres. Running analog cable from every accelerometer back to a central rack means long runs, noise pickup over those runs, and a lot of copper.

SIRIUS® X and IOLITE® X put the digitizer next to the sensor instead. Units daisy-chain over a single Ethernet cable that carries power, data and synchronization together, using PoE and PTPv2 timing, so one cable leaves the measurement area rather than hundreds. SIRIUS X takes up to 32 analog inputs per device, with a 24-bit delta-sigma converter and an anti-aliasing filter on every input. IOLITE X is fanless and rated from −40 °C to +70 °C.

Because synchronization travels with the data, channels at opposite ends of the structure stay on one time base — which is what makes it possible to track a shock wave propagating through a structure rather than just recording its arrival at each point separately.

Rugged and distributed measurement

KRYPTON® modules are IP67-rated and sit at the test article rather than in a rack — on a vehicle, on a range, outdoors in weather.

SIRIUS® Waterproof goes further for the harshest shock environments: IP67, an operating range of −40 °C to +60 °C, and rated to withstand 100 g shock and 100 g vibration itself, sampling at 200 kHz per channel. Voltage, IEPE, bridge, RTD and resistance are native, with charge, thermocouple, current and LVDT available through DSI adapters. When the measurement happens in cold, dust, mud or rain — or when the DAQ is going to take a share of the shock it is measuring — this is the one that survives it.

Synchronized video for shock testing

A shock measurement tells you what happened. Video tells you why — a fixture slipping, a cable whipping, a component contacting something it should not. Dewesoft integrates cameras into the same acquisition as the data, so frames and samples share one time base and you can scrub the video and the SRS curve together.

High-speed video

DS-CAM, Dewesoft's own GigE Vision camera range, records at 2048 × 1536 px at 37 FPS, with frame rates up to 6400 FPS at reduced resolution. Colour and monochrome versions are available, both with global shutters. Multiple DS-CAM cameras synchronize to each other through a PTP-enabled switch.

For the fastest events, Photron and Phantom ultra-high-speed cameras connect through dedicated plugins, reaching thousands to millions of frames per second depending on resolution, and stay fully synchronized with the analog and digital channels in DewesoftX.

Standard video

For context rather than event analysis, DS-CAM at standard frame rates or almost any DirectX-compatible webcam will record alongside the data. Webcam synchronization is software-based and accurate to roughly 10 ms — fine for documenting a test setup or an operator action, but not for resolving an event that lasts a few milliseconds.

Thermal imaging

OPTRIS infrared thermal cameras integrate into the same acquisition, adding surface temperature to the record. Synchronization is software-based at around 100 ms, so thermal video documents the thermal state around a test rather than the shock event itself — useful where shock testing is combined with thermal conditioning, or where a component heats under repeated impact.

Picking a camera for shock: a shock event lasts milliseconds, so only the hardware-synchronized options — DS-CAM, Photron, Phantom — resolve it frame-accurately against the data. Webcam and thermal sync, at ~10 ms and ~100 ms, are for context around the test.

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Where Dewesoft fits in a shock test

Dewesoft provides the measurement and analysis side of shock testing: acquiring the event, computing the SRS and reporting the result. Dewesoft does not supply shock machines, drop towers or shaker controllers, and does not control a shaker to reproduce a synthesized shock profile.

In practice that means Dewesoft systems are used alongside whatever shock machine, drop tower or test rig you already have — measuring what actually happened on the test article, independently of the controller driving the table. For drop shock, pyroshock, ballistic shock, blast and transportation shock, where there is no controller at all, the Dewesoft system is the whole measurement chain.