Classical Shock Testing

Classical shock testing consists of the following shock impulses: half sine, haversine, sawtooth, and trapezoid.  Pyroshock and ballistic shock tests are specialized and are not considered classical shocks. Classical shocks can be performed on Electro Dynamic (ED) Shakers, Free Fall Drop Tower or Pneumatic Shock Machines. The parameters required to define a shock test are peak acceleration expressed in G’s or m/sec^2, shape of the impulse, and duration in milliseconds.  A classical shock impulse is created when the shock table changes direction abruptly.  This abrupt change in direction causes a rapid velocity change which creates the shock or acceleration impulse.

Figure 1.  Shock Test by DES

Figure 1. Shock Test by DES

Classical shocks are applied along one direction and one axis at a time.  Most specifications require the product to be shocked in both the positive and negative directions along each axis.  If shock tests are performed on an ED shaker, the shaker can reverse polarity and perform the shock along both directions of each axis without rotating the fixture and specimen.  When performing shock testing on a shock machine, the machine can only apply shock in one axis and one direction.  The fixture and specimen must be rotated to apply shocks along different directions and axes.

A typical shock test setup using a pneumatic shock machine is shown in Figure 1.  DES can also perform shock testing using an ED shaker and drop tower.

Continue Reading Classical Shock Testing