Analysis of piezomotor driver for laser beam deflection

A mechanical laser beam deflection using piezoactuator is analyzed in the paper. Wide angular range was required therefore mechanical mirror positioning using a multilayer piezoceramics friction drive configuration was chosen. The paper reports on research results of the deflection system parameters. Dynamic and static motion parameters such as angular speed, breaking displacement, positioning repeatability and angular resolution have been analyzed. For this purpose the measurement equipment have been designed and manufactured. Analysis of breaking characteristics has revealed that breaking angular displacement is dependant on driving voltage. Conducted positioning repeatability experiments indicate that the relative error between steps was about 1 %. Analysis of the complex electrical impedance of the piezoactuator over frequency range under varying load conditions was conducted. The equipment for measurement of electrical parameters has been described. Experimental research results of the actuator complex impedance are presente

Automatic simultaneous measurement of phase velocity and thickness in composite plates using iterative deconvolution

A new method for the automatic and simultaneous measurement of phase velocity and thickness for thin composite plates was developed based on Ping He's method, without any need of a priori knowledge of the material parameters. Two composites were analyzed: a block of clean epoxy and a thin specimen of glass-fiber reinforced plastic produced by resin transfer molding. The proposed method combines cross-correlation functions and iterative deconvolution for accurate measurement of times of flight and gating. The new method has demonstrated to be more accurate than conventional Ping He's method, and can be implemented automatically thus saving processing time and increasing accuracy.This research was funded by a Project IN-SMART, Grant no. VP1-3.1SMM-10-V-02-012 and by the Spanish Ministerio de Ciencia e Innovacion (TEC2011-23403).Rodriguez Martinez, A.; Svilainis, L.; Dumbrava, V.; Chaziachmetovas, A.; Salazar Afanador, A. (2014). Automatic simultaneous measurement of phase velocity and thickness in composite plates using iterative deconvolution. NDT and E International. 66:117-127. https://doi.org/10.1016/j.ndteint.2014.06.001S1171276

Comparison of spread spectrum and pulse signal excitation for split spectrum techniques composite imaging

[EN] Ultrasonic imaging of composites was investigated. Glass and carbon fiber reinforced plastic produced by resin transfer molding and prepreg forming were analyzed. In some of the samples air bubbles were trapped during RTM (resin transfer molding) process and interlayer gaps were present in prepreg technology samples. One of the most expected techniques to apply in such case is the Split Spectrum processing. On the other hand such signals require specific processing to reliably reconstruct the temporal position of the defect reflection. Correlation processing can be used for signal compression or Wiener filtering can be applied for spectral content equalisation. Pulse signals are simple to generate, but lack the possibility to alter the signal’s spectrum shape. Spread spectrum signals offer a powerful tool for signal energy over frequency band increase and resolution enhancement. CW (continuous wave) burst has high energy but lacks the bandwidth needed for SSP (spread spectrum processing). The aim of the investigation was to compare the performance of the above signals in case of composite imaging, when various Split Spectrum Processing techniques are used with preceding Wiener processing for spectral content compensation. Resulting composite signals and images obtained are presented. Structural noise removal performance was evaluated as Receiver Operating Characteristics (ROC).This research (acquisition system and spread spectrum signals) was funded by a grant (No. MIP058/2012) from the Research Council of Lithuania. SSP part was supported by PROMETEO 2010/40.Svilainis, L.; Kitov, S.; Rodriguez Martinez, A.; Vergara Domínguez, L.; Dumbrava, V.; Chaziachmetovas, A. (2012). Comparison of spread spectrum and pulse signal excitation for split spectrum techniques composite imaging. IOP Conference Series: Materials Science and Engineering. 42:5-9. https://doi.org/10.1088/1757-899X/42/1/012007S594