180 research outputs found
Identification of impact damage in CRRP laminates using the NDT approach
No full textThe motivation for this work is to identify impact damage in structures made from composite material. The composite material chosen for this research was Carbon Fibre Reinforced Polymer (CFRP) prepreg with a MTM57 epoxy resin system with CF2900 fabric. This material was fabricated to produce laminated plate specimens of 250 mm × 150 mm with 11, 12 and 13 layers of thickness. PZT sensors were placed at three different points on each of the plate specimens to record the responses from impact events. The impact test was performed using an instrumented drop test rig and the impact energies were set to range from 2.61 J to 41.72 J. All the signals captured from the impact test were recorded using a LMS data acquisition system and the impacted plate specimens were later examined using X-rays to evaluate the damage area. The correlation between the damage area in terms of the impact energy and the force detected is presented and discussed
Impact damage detection and quantification in CFRP laminates; a precursor to machine learning
No full textThe main objective of this research is to detect and classify impact damage in structures made from composite materials. The material chosen for this research is a Carbon Fiber Reinforced Polymer (CFRP) composite with a MTM57 epoxy resin system. This material was fabricated to produce laminated plate specimens of 250 mm × 150 mm, each with three PZT sensors placed at different points in order to record the responses from impact events. An impact hammer was used to produce FRF and time data corresponding to undamaging impacts. To perform the damaging impact tests, an instrumented drop test machine was used and the impact energy was set to range from 2.6J to 41.72J. The signals captured from each specimen were recorded in a data acquisition system for evaluation and the impacted specimens were X-rayed to evaluate the damage areas. As a precursor to the application of machine learning, a number of univariate features for damage identification were investigated
On impact damage detection and quantification for CFRP laminates using structural response data only
No full textThe overall purpose of the research is to detect and attempt to quantify impact damage in structures made from composite materials. A study that uses simplified coupon specimens made from a Carbon Fibre Reinforced Polymer (CFRP) prepreg with 11, 12 and 13 plies is presented. PZT sensors were placed at three separate locations in each test specimen to record the responses from impact events. To perform damaging impact tests, an instrumented drop test machine was used and the impact energy was set to cover a range from 0.37 J to 41.72 J. The response signals captured from each sensor were recorded by a data acquisition system for subsequent evaluation. The impacted specimens were examined with an X-ray technique to determine the extent of the damaged areas and it was found that the apparent damaged area grew monotonically with impact energy. A number of simple univariate and multivariate features were extracted from the sensor signals recorded during impact by computing their spectra and calculating frequency centroids. The concept of discordancy from the statistical discipline of outlier analysis is employed in order to separate the responses from non-damaging and damaging impacts. The results show that the potential damage indices introduced here provide a means of identifying damaging impacts from the response data alone
On the need for bump event correction in vibration test profiles representing road excitations in automobiles
No full textThis paper presents an approach to the synthesis of compressed vibration test profiles
representing much longer time histories obtained in road testing of ground vehicles. Vibration test
profiles are defined as those related directly to operational testing on specific road surfaces and
which summarise the input to the vehicle in the given conditions. The method extends classical
Fourier transform technique by means of bump event correction in the background Fourier signal
where the bump event term implies a high-amplitude transient event of the shock type. The
orthogonal wavelet decomposition was used as a specific filtering tool facilitating bump event
identification. Examples of seat guide vertical acceleration have been considered. Calculated
probability density functions suggest the ability of the bump correction method to improve the
statistical accuracy of the final vibration test profile with respect to the original road data. Test
profiles obtained by means of Fourier transform synthesis with subsequent reinsertion of bump
events from separated frequency bands were more accurate than those obtained by Fourier synthesis
alone. Further developments led to advanced bump reinsertion with synchronisation of events
occurring in different frequency bands at the same moment of time. Test profiles generated in this
way have provided better accuracy compared to the non-synchronised algorithm
Damage imaging in composites using nonlinear vibro‐acoustic wave modulations
No full textThe paper deals with the application of nonlinear vibro‐acoustic modulation technique for detection and localization of impact damage in a laminated composite plate. An imaging procedure—based on the nonlinear vibro‐acoustic modulation sidebands—is proposed. The procedure relies on simultaneous low‐frequency modal and high‐frequency ultrasonic excitations. Laser scanning vibrometry is used to analyze the amplitude of modulation sidebands in vibro‐acoustic responses. This analysis is performed for different positions on monitored structure to reveal the location and shape of damage. The method is illustrated using a simple example of impact damage detection in a composite plate. The experimental damage detection results are compared with the results obtained from the previously used approach on the basis of higher harmonic generation. The proposed method demonstrates better ability to locate damage in these comparative tests without the need to increase the measurement bandwidth to the higher harmonics regime. The work shows that the local defect resonance analysis can improve damage detection results of both compared approaches
Millimeter-wave digitally intensive frequency generation in CMOS / Wanghua Wu, Robert Bogdan Staszewski, John R. Long.
No full textIncludes bibliographical references and index.xi, 188 p.
Non-contact ultrasonic guided wave inspection of rails
No full textThe University of California at San Diego (UCSD), under a Federal Railroad Administration (FRA) Office of Research and Development (R&D) grant, is developing a system for high-speed and non-contact rail integrity evaluation. A prototype using an ultrasonic air-coupled guided wave signal generation and aircoupled signal detection has been tested at the UCSD Rail Defect Farm. In addition to a real-time statistical analysis algorithm, the prototype uses a specialized filtering approach due to the inherently poor signal-to-noise ratio of the air-coupled ultrasonic measurements in rail steel. The laboratory results indicate that the prototype is able to detect internal rail defects with a high reliability. Extensions of the system are planned to add rail surface characterization to the internal rail defect detection. In addition to the description of the prototype and test results, numerical analyses of ultrasonic guided wave propagation in rails have been performed using a LISA algorithm and some of these results are shown. The numerical analysis has helped designing various aspects of the prototype for maximizing its sensitivity to defects
Non-Contact Ultrasonic Guided Wave Inspection of Rails
No full textThe University of California at San Diego (UCSD), under a Federal Railroad Administration (FRA) Office of Research and Development (R&D) grant, is developing a system for high-speed and non-contact rail integrity evaluation. A prototype using an ultrasonic air-coupled guided wave signal generation and air-coupled signal detection, in pair with a real-time statistical analysis algorithm, is being developed. This solution presents an improvement over the previously considered laser/air-coupled hybrid system because it replaces the costly and hard-to-maintain laser with a much cheaper, faster, and easier-to-maintain air-coupled transmitter. This system requires a specialized filtering approach due to the inherently poor signal-to-noise ratio of the air-coupled ultrasonic measurements in rail steel. Various aspects of the prototype have been designed with the aid of numerical analyses. In particular, simulations of ultrasonic guided wave propagation in rails have been performed using a Local Interaction Simulation Approach (LISA) algorithm. Many of the system operating parameters were selected based on Receiver Operating Characteristic (ROC) curves, which provide a quantitative manner to evaluate different detection performances based on the trade-off between detection rate and false positive rate. Experimental tests have been carried out at the UCSD Rail Defect Farm. The laboratory results indicate that the prototype is able to detect internal rail defects with a high reliability. A field test will be planned later in the year to further validate these results. Extensions of the system are planned to add rail surface characterization to the internal rail defect detection
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