Classical shock profile

Measuring equipment, communications-electronic equipment and other products that are exposed to single and multiple shocks in the course of usage and transportation should undergo tests for shock load resistance.

Shock loads resistance tests can be used to estimate sample product quality as well as its structural strength. The tests are performed by exposing the sample to single or multiple shocks with pre-set duration and peak velocity. Below you can see shock pulses shapes produced by the Software VCS-Classical shock as well as the parameters set in the course of program setting.

Shock signals can be produced with pre- and post-shock pulses or without them. In the figure below T stands for shock duration and A for its amplitude. Duration as well as amplitude of pre- and post-pulses exceeds duration of shock puslses in 10 times. Trapezoidal signal has additional parameters such as rise and fall time of the signal (T1 and T2). Sawtooth signal has fall time option (T2).

Half-sine pulse is used to reproduce a shock occuring in the case of collision or hard deceleration of a linear mobile system (for instance, in the case of elastic shock).

Полусинусоидальный импульс

Трапецеидальный импульс

Trapezoidal pulse causes higher response in broad band frequencies range if compared to a half-sine pulse.  It is used to reproduce shock impacts similar to those occuring during hook jettison of a space ship.

Terminal peak sawtooth pulse  has more even spectrum if compared to half-sine or trapezoidal pulse.

Пилообразный импульс

Прямоугольный импульс

Rectangular pulse is a particular case of trapezoidal pulse.

Triangular pulse is a particular case of sawtooth pulse.

Треугольный импульс

Setting tests profile

in VCS-Classical shock Program

Shock load test parameters are set in the Menu “Vibration tests’ profile editing” available from the main menu “Testing profile”. 

График сейсмического синусоидального удара

VCS Classical shock Software enables setting of the following parameters:

  • Duration of the shock (ms) —duration of the pulse, T.
  • Shock amplitude, g — peak vibroiacceleration value, A.
  • Shock frequency per minute— number of shocks per minute (1 – 120).
  • Total shocks number — total vibration test shock number.
  • Rise time (ms) — time required to achieve trapezoidal signal maximum value, T1.
  • Fall time (ms) — time required to achieve trapezoidal and sawtooth signal minimum value, T2.
  • Voltage at FR measuring (mV) — RMS noise signal value used to measure FR prior to tests.
  • FR measuring duration, s – duration of time interval prior to tests during which FR is measured using noise signal.
  • Check box “Pre-shocks” allows to introduce additional shocks with an amplitude of 10% from the main shocks amplitude or the pourpose of required voltage precise measurement.
  • «Pre-shocks amplitude, g» — is an amplitude of pre-shocks used for the purpose of required voltage precise measurement (maximum 10% from the main shocks amplitude)
  • Check box «Pre-post-pulses» enables presence of preliminary signals for balancing of shaker velocity and displacement.
  • Check box «Seismic shock»enables seismic shock simulation. Unlike ordinary shock, seismic one has velocity both in positive and negative directions. Seismic sinusoidal signal shape is shown in the figure below

Сейсмический удар
Seismic sinusoidal shock diagram 

Drop down list “Control channel” depicts lists of available channels for vibration tests control (channels measuring velocity in «g» or «m/s2».

“Shock direction” option allows to set modulus sign of acceleration amplitude: up (+) and down (-).