NDT versus LDV

Non destructive testing procedures such as X-ray imaging, ultrasonic scans, infrared thermograph and eddy current methods are commonly used for damage detection. These techniques have their own limitations. They are time consuming and difficult to implement in field conditions. Most of the above techniques require the vicinity of damage known a priori and readily accessible. In many complex structures even if the detection of defect is accurate, its location and characterization may be difficult and require expert opinion.

The use of advanced and precise optical measurement systems such as Laser Doppler Vibrometer is gaining in extracting vibration signatures for the purpose of damage detection as mass loading of the specimen due to sensors and actuators in embedded systems may be avoided and repeatability and reproducibility of measurements may be ensured. A Polytec Scanning Vibrometer (PSV-3D) [Polytech Gmbh, Germany] has been used in this study for experimental modal analysis.