Особенности лазерно-виброметрического неразрушающего контроля полимерных композиционных материалов с использованием воздушно-связанных ультразвуковых преобразователей

Laser doppler vibrometry is being increasingly used in nondestructive testing (NDT) of polymer composites materials (PCM) and investigation of amplitude-frequency characteristics of acoustic transducers in a wide range of frequencies. The use of air-coupled transducers allows non- contact NDT thus expanding inspection potentials and simplifying, in some cases, test procedures, as well as reducing the environmental impact on test results, to compare to traditional techniques of acoustic NDT, which mainly implement contact stimulation of objects to be tested. In this study, the peculiarities of non-contact ultrasonic stimulation in application to NDT are analyzed by using scanning laser vibrometry. The results of NDT of impact damage in PCM are presented by using some types of air-coupled acoustic transducers, namely, magnetostrictive, piezoelectric and gas discharge.

Damage detection in a composite wind turbine blade using 3D scanning laser vibrometry

As worldwide wind energy generation capacity grows, there is an increasing demand to ensure structural integrity of the turbine blades to maintain efficient and safe energy generation. Currently, traditional non-destructive testing methods and visual inspections are employed which require the turbine to be out-of-operation during the inspection periods, resulting in costly and lengthy downtime. This study experimentally investigates the potential for using Lamb waves to monitor the structural integrity of a composite wind turbine blade that has been subject to an impact representative of damage which occurs in service. 3D scanning laser vibrometry was used to measure Lamb waves excited at three different frequencies both prior to, and after, impact to identify settings for an optimal system. Signal processing techniques were applied to the datasets to successfully locate the damage and highlight regions on the structure where the Lamb wave was significantly influenced by the presence of the impact damage. Damage size resulting from the impact was found to correlate well with the laser vibrometry results. The study concluded that acousto-ultrasonic-based structural health monitoring systems have great potential for monitoring the structural integrity of wind turbine blades.

Experimental and Finite Element Analysis of Natural Modes and Frequencies of Hollow Fan Blades

Natural modes and frequencies of gas turbine engine hollow fan blades were experimentally investigated. The blades were produced with the method of super-plastic molding and pressure welding combination. Two independent experimental methods were used: three-component scanning laser vibrometry and impact modal analysis. Natural frequencies and vibration modes of a hollow fan blade and stress fields corresponding to the natural modes were got. The finite element modal analysis was carried out. The hollow fan blade was stated to have particular natural vibration modes. The investigation results can be used to detune the resonance vibrations and to verify calculation models.