Explain the Dynamic or Vibration Tests

Tests of this type, also known as sonic integrity test, involve sub- jecting the element to a single impulsive blow or cyclic load, and measur- ing the response of the element. This response is measured in terms of decaying response. All other things being equal, the response of the ele- ment will depend on the stillness of the element and the naturally inherent damping, both of which are changed by the presence of flaws. Therefore, if there was a change in response between two tests, a close investigation should be carried out to establish a cause.

The system generally employs accelerometers to detect the vi- bration signal. The accelerometers are mounted on the structure to a depth of 30 m below the surface, and the frequency analysis required to compare the vibration signature at various times is carried out by com- puter.