12.1 Definitions

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12.1.1 Shock

Shock occurs when a force, a position, a velocity, or an acceleration is abruptly modified and creates a

transient state in the system considered. The modification is normally regarded as abrupt if it occurs in

a time period that is short compared with the natural period concerned (AFNOR, 1993). Shock is defined

as a vibratory excitation having a duration between the natural period of the excited mechanical system

and two times that period (Figure 12.1).

12.1.2 Simple (or Perfect) Shock

A shock whose signal can be represented exactly in simple mathematical terms is called a simple

(or perfect) shock. Standards generally specify one of the three following: half-sine (approached by a

versed sine waveform), terminal peak sawtooth, and rectangular shock (approached by a trapezoidal

waveform).

12-2 Vibration and Shock Handbook

© 2005 by Taylor & Francis Group, LLC

12.1.3 Half-Sine Shock

This is a simple shock for which the acceleration –

time curve has the form of a half-period (part

positive or negative) of a sinusoid.

12.1.4 Versed-Sine (or Haversine)

Shock

This is a simple shock for which the acceleration –

time curve has the form of one period of the curve

representative of the function ½1 2 cosð Þ􀀉; with this

period starting from the zero value of this function.

It is thus a signal ranging between two minima of a

sine wave.

12.1.5 Terminal Peak Sawtooth

Shock or Final Peak Sawtooth Shock

This is a simple shock for which the acceleration – time curve has the shape of a triangle, where

acceleration increases linearly up to a maximum value and then instantly decreases to zero.

12.1.6 Rectangular Shock

This is a simple shock for which the acceleration – time curve increases instantaneously up to a given

value, remains constant throughout the signal, and decreases instantaneously to zero. In practice, what is

carried out are trapezoidal shocks.

12.1.6.1 Trapezoidal Shock

This is a simple shock for which the acceleration – time curve grows linearly up to a given value, remains

constant during a certain time period, after which it decreases linearly to zero.

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