Shock Response Spectrum (SRS) Test System

A shock response spectrum is a useful tool for estimating the damage potential of a shock pulse, as well as for test level specification.

The shock response spectrum is a calculated function based on the acceleration time history. It applies an acceleration time history as an excitation to an array of single-degree-of-freedom (SDOF) systems. Each system is assumed to have no mass-loading effect on the base input.

The Shock Response Spectrum (SRS) Test System is used to determine the damage potential of components and systems from transient events, such as pyroshocks, in order to ensure their survival in known environments.A single transient shock event such as a pyroshock or a structural impact can damage components in a structural system. Similarly, earthquakes can cause catastrophic failures in bridges and buildings. And with any motion input into a system, the response can be amplified by structural resonances, increasing the damage. 
By calculating the shock response spectrum (SRS) from transients in the time domain, it can be determined how shocks affect a structure.
Shock Response Spectrum Analysis software supports all five SRS models described in the ISO 18431-4:2007 standard. Combined with the nine ordinary criteria for amplitude calculations (shock instances), up to 45 response types can be calculated to match your requirements.
Special shock accelerometers for high-level and high-frequency measurements are part of our complete measurement and analysis chain.
SHOCK RESPONSE ANALYSIS

Application that computes the shock response spectrum (SRS) from transients in the time domain to determine the damage potential of transient events such as pyroshock application computes the shock response spectrum (SRS) of a test object from transient events in the time domain such as pyroshocks or structural impacts. It enables you to determine the damage potential of the transient events and to predict whether the structure will survive such shocks. The SRS calculation converts motion input into single degree of freedom (SDOF) damped oscillator responses. The response amplitudes of the oscillators are plotted as a function of SDOF frequencies to produce the SRS. The SRS is calculated in accordance with the ISO 18431–4:2007 standard for shock response analysis. 
USE SCENARIOS

Determining the structural damage potential from exposure to shock events such as pyroshocks during rocket stage separation.

Durability testing of shock-sensitive devices such as avionics and guidance equipment.

Accurately testing components when a vibration test system cannot generate the time signal of the original shock event due to dynamic limits. Instead shock response synthesis is used, where a new manageable shock pulse is generated with the same SRS as the original shock event.

Design studies comparing, for example, support structures before and after a weight reduction.

Earthquake engineering, to ensure that buildings, bridges and other infrastructures can survive earthquakes

CHARACTERISTICS

The software includes pre-processing of the shock event. The input data can be viewed before individual shock events are selected for analysis. Before the shock response spectrum calculations themselves, these individual shock events can be corrected for DC offset and drift. The end velocity of the input can be forced to zero as is required in some applications. There are potentially 45 different options for the user: five shock response spectrum models and nine amplitude calculation outputs (shock instances).

CAPABILITIES

Fulfils ISO 18431 - 4:2007 Mechanical vibration and shock - Signal processing - Part 4: 

Shock-response spectrum analysisShock response spectrum models: Absolute acceleration, Equivalent Static Acceleration, Pseudo Velocity, Relative Velocity and Relative DisplacementImports acceleration, velocity and displacement transients. Velocity and displacement data are automatically converted to acceleration data before the SRS calculation.

Ramp-invariant z-transform to reduce errors at high frequencies for pyroshock applications.

Dynamic oversampling, which reduces bias error and improves the accuracy of peak detection.

Determination of the velocity change during impact using the pseudo-velocity shock response spectrum model.

Revealing damage potential from impacts in a pseudo velocity spectrumThe amplitudes of the SRS are derived from these individual SDOF responses by taking the maximum response from the primary shock event (during forced motion), or during the residual response to the event (free response). Most commonly, the overall maximum response is used, which includes both primary and residual responses (maximax). 

SHOCK RESPONSE SPECTRUM (SRS) SOFTWARE

Application for calculating the shock response spectrum in order to determine how shocks will affect a structure. It can be used individually or in conjunction with other applications as part of tailored workflows.
SHOCK RESPONSE SPECTRUM SYNTHESIS

VIBRATION CONTROL

A vibration control feature used to synthesize a specified shock response spectrum (SRS) to measure a payload’s resistance to shock damage.

SRS synthesis is used to evaluate the shock resistance of the DUT (device under test). This is achieved by synthesizing, within a closed-looped test system, a user-specified SRS profile of acceleration versus frequency in order to create complex transient waveforms for driving an electrodynamic shaker. The desired SRS profile is sometimes referred to as RRS (required response spectrum).
The test system takes advantage of the fact that many different transient waveforms can produce the same SRS profile; hence, parameters can be selected to account for the shaker’s capabilities and for likely damage to the DUT.
USE SCENARIOS

Simulating shock transients, including pyrotechnic bursts and earthquake waveforms

Shock damage testing, or shock damage risk analysis (SDRA), by matching a specified SRS profile

Aerospace testing applications, such as reliability tests of electronic and mechanical components during explosive events

Earthquake simulation and seismic qualification testing of buildings and other structures

Packaging, shipping and transportation testing

Reliability and durability testing of computer equipment, including shock tests of hard drives

CHARACTERISTICS

An add-on function of the classic shock profile, SRS synthesis and control enables a more aggressive and sophisticated shock test. It synthesizes a complex transient waveform from sinusoidal components, or wavelets, based upon a table of sine beats (or damped sine), with a wavelet used for each of the Nth octave bands.

An iterative process is used to automatically adjust the amplitudes, half-cycles, and relative delays of the wavelets until the SRS of the synthesized pulse matches the profile SRS, within the required accuracy. The generated time-domain shock can then be manually adjusted within a specified SRS fitting error to create a pulse that matches the test criteria, typically pulse duration. The desired shock pulse is saved for future reference and can be applied repeatedly and consistently.
The user creates an SRS profile by either entering or importing a breakpoint table of frequencies and acceleration amplitudes, plus abort limits. Also specified are the Q-factor (or damping) and the synthesis method as either pyroshock, minimum acceleration or user-defined duration.
SRS analysis typically covers up to a 14-octave range using maxi-max, negative maximum, and positive maximum analysis techniques. The user specifies high and low frequencies, reference frequency, damping ratio or Q value and resolution (1/1, 1/3, 1/6, 1/12, 1/24, 1/48).