Amin Baghalian

Implementation of the Surface Response to Excitation Method for Pipes

The Surface response to excitation (SuRE) method was developed to detect the defects and loading condition changes on plates without using the impedance analyzer. The SuRE method excites the surface with a piezoelectric exciter. Generally, sweep sine wave is continuously applied and surface waves are monitored with (a) piezoelectric element(s) or noncontact sensor(s). The change of the spectral characteristics is quantified by using the sum of the squares of the differences (SSD) to detect the defects. In this study, the SuRE method was implemented for detection of the defects in pipes. The surface of a pipe was excited with a continuous sweep sine wave and the dynamic response of the pipe on selected points were monitored by using a scanning laser vibrometer. The study shows that the SuRE method can be used effectively for detection of damage and estimation of its severity in pipe like structures.

Implementation of the Surface Response to Excitation (SuRE) Method with DSP’s for Detection of the Damage of Thick Blocks

Surface Response to Excitation Method (SuRE) is an active structural health monitoring (SHM) method. SuRE method was implemented by exciting the surface of a plate with a piezoelectric element. The propagation of the created surface waves were monitored with one or more sensors. These sensors could be piezoelectric elements or noncontact sensors such as laser scanning vibrometer. During the experiments, one of the piezoelectric elements excited the block at the 20-400 KHz range while the signals of other piezoelectric elements were recorded and their spectrums were calculated. The reference spectrums of sensors were obtained when the block had no defect. However, in the presence of defect the spectrum deviates from reference response. SuRE method quantifies these changes by calculating sum of square of differences (SSD). It is shown that SuRE method is able to effectively detect the defects. doi: 10.12783/SHM2015/233

Inspection of the machined features created at the embedded sensor aluminum plates

Manufacturing the raw materials for aerospace structures with embedded sensors to be connected them to the central monitoring station of the structural health monitoring (SHM) systems has been considered by many researchers and industries. These structures can be inspected in very short time by connecting the sensors to a monitoring system. The quality of the part may be evaluated while geometric features such as holes and slots are created during the machining process. Surface response to excitation (SuRE) method is a low-cost alternative to the electromechanical impedance (EMI) method. The SuRE method uses one piezoelectric transducer to excite the surface of a structure with a sweep sine wave, and one or more piezoelectric sensors or scanning laser vibrometer monitor the dynamic response of the system. Once a change which may lead to a structural failure is introduced to the structure, some mechanical properties are altered. The frequency spectrum of the signal received by the sensors will change after the dimensions of the geometric features are modified. In this study, feasibility of the SuRE method was evaluated for inspection of the quality of the machined features on aluminum plates. The SuRE method was used to characterize different geometric features created by the milling operation on identical aluminum plates. One piezoelectric transducer was used as an exciter and propagation of the surface waves were monitored by a scanning laser vibrometer. The Fast Fourier Transformation (FFT) was used for the analysis of the sensory data after each data collection. By increasing the size of milling in two different dimensions, the sum of the squares of the differences (SSD) of the spectrums drastically changed. Also in order to get rid of the need for baseline (reference) data collected at the initial conditions, some advanced techniques such as Geometric mean, Harmonic mean and 5th momentum were introduced.

Internal defect detection in hollow cylindrical structures using the Surface Response to Excitation (SuRE) Method

Active structural health monitoring methods are becoming increasingly popular for defect detection in hollow cylindrical structures utilized in aerospace applications. Electro mechanical impedance (EMI) based methods are commonly used to study the health of hollow cylinders in broad frequency ranges. However, the EMI analyzers are bulky and costly. In addition, EMI based methods require high quantity of sensors for monitoring a large area. The Surface Response to Excitation (SuRE) method was developed to eliminate the need for EMI analyzers in broad frequency range inspections and to decrease the number of sensors in monitoring of large structures. In this study, the performance of the SuRE method in detection of internal defects is evaluated theoretically and experimentally. Different internal damages were created in an aluminum pipe specimen. The data collected from four bonded piezoelectric elements were used for damage detection and quantification. The test results showed the high sensitivity and robustness of the SuRE method in internal damage detection.

Load Monitoring Using Surface Response to Excitation Method

Surface response to excitation (SuRE) method is a low-cost alternative to the electromechanical impedance method developed for the structural health monitoring (SHM) applications. This method uses one piezoelectric transducer to excite the surface of a structure with a sweep sine wave. One or more piezoelectric sensors or scanning laser vibrometer monitors the dynamic response of the surface to the excitation. The spectrum of the dynamic response is collected at the optimal operating conditions. Any significant change of the spectral characteristics may indicate defects, improper loading or loose fasteners.

Composites Bond Inspection Using Heterodyne Effect and SuRE Methods

With increasing utilization of the composite materials in commercial and military applications, the longevity of composite bonds has become a crucial concern of the aerospace industry. In spite of the previous studies in the literature for characterization of bonding condition in composite materials, implementation of more advanced structural health monitoring (SHM) techniques are still required to ensure flight safety and quick inspections of structures. In this study, two different SHM methods were used to evaluate the strength of composite bonds by using two separate experimental setups. First, the heterodyne effect method was used for assessing the separation in the composite joint. Then, the surface response to excitation (SuRE) method was used for studying various simulated contamination levels. Results of the experimental studies showed that the proposed methods could be efficiently utilized for evaluating bonding strength of composite materials.