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Static break-down tests were carried out with samples made of carbon fiber plastics. Testing for defects was performed using acoustic emission and strain gaging methods. Four wire strain gages were ...glued to each sample in the aperture area, and four piezoelectric sensors were installed along aperture edges to form a working testing zone. Recording the signals associated with the failure of the composite material of the samples and their location were carried out by an acoustic emission system. During the tests, a strain gage system recorded loads and deformations that lead to the initiation of destruction process in carbon fiber plastics. The destruction type was determined based on analyzing the microsections made from the signal location zone in the sample. The main informative parameters of acoustic emission signals were associated with the destruction type of carbon fiber plastics.
Comparative tests related to locating acoustic emission (AE) signals due to shock impacts on a T700 carbon fiber sample were carried out. Piezoelectric acoustic emission transducers (AETs) and ...fiber-optic sensors (FOSs) were installed on the sample, forming rectangular location antennas measuring
mm. Strikes were delivered with balls weighing 10 and 18.5 g. Antennas consisting of four AET sensors and four FOS sensors and an antenna consisting of two AET sensors and two FOS sensors were organized. When using the antenna containing four FOS sensors, the impact on the sample was produced by a load weighing 530 g dropped from a height of 400 mm. AE signals were recorded by the SCAD-16.10 system with “floating” selection thresholds when the ball was dropped and during its repeated bounces. Then AE signal clusters were formed and recorded during the impact of loads. The arrival times of AE signals to the antenna sensors were calculated using the threshold method, the root mean square (RMS) deviation method and the two-interval method. It is shown that the maximum error in locating AE signals is observed when a steel ball with a diameter of 16 mm is dropped from a height of 300 mm and the minimum error is when using an electronic simulator.
—The propagation time of longitudinal, transverse, and transformed ultrasonic waves in three R65 rail segments is estimated as a function of temperature using a high-speed acoustoelasticity-based ...microprocessor system. The obtained time dependences and the results of estimating the errors of measuring the time parameters made it possible to calculate the longitudinal stresses over the entire sonic test rail volume in an operating railway track segment at an error of at most 10%.
Static tests of a two-spar
T
800 CFRP wing box have been carried out. The object was tested when loaded using the methods of acoustic emission (AE) and strain gaging. Strain in the material was ...determined in real time in the areas where strain gages were bonded (the panels of wing box, the walls of side members, and the shelves of stringers). The elements of the wing box have been established in which nonlinear strain change is observed and residual deformations are recorded after unloading. The AE method has been used to localize the sources of signals. The coordinates of the sources corresponded to the location of the third rib. Clustering recorded AE signals based on their digitized form has made it possible to group the signals and assign them to sources that correspond to structure failure. It is shown that in the process of loading the wing box, an increase in the structural coefficient of AE signals corresponding to CFRP delamination in the location zone is observed.
Near-IR spectroscopy is a promising analytical method in pharmacy. It was shown that it can be used as a rapid method for confirming the identity and analyzing the purity of kemantane ...(5-hydroxyadamantan-2-one) drug substance.
The article is devoted to the urgent and poorly known problem of the place and role of women in the English gentry’s community of the first half of the XV century. Using the information from the ...correspondence of the Armburghs (The Armburgh Papers), the author traces the main stages of Joan Armburgh's life and varieties of her fortune and that of her nieces and finds out how typical they were in accordance with generally accepted ideas about the place and mission of a woman from the gentry’s family. The article shows that the status of a woman was determined by the family and her well-being depended on the relatives - her father and husband. However, this did not exclude the active role of the woman in asserting her rights and interests of the family. The biography of Joan Armburgh and the facts from the life of her nieces, who belonged to the gentry, contradict the idea of weakness and humility of wives in noble families. Difficulties that they had to deal with forced these women to show a surprising for noblewomen activity and persistent desire to defend their interests, relying on their own connections in society and knowledge of law, and on men’s support.
Results of the strength tests of an aircraft wing spar made of Toray T1000 carbon fiber-reinforced plastic are presented. Construction failure zones have been inspected by the methods of acoustic ...emission (AE) and tensometry. Loading-induced changes in the stress-strain state (SSS) of wing-spar material have been analyzed. The coordinates of AE signal sources that correspond to the separation of the upper spar cap from the spar web have been determined. Algorithms for AE-data processing using wavelet transforms are considered. Connections have been established between changes in stresses emerging in CFRP material, AE signal structure, and the occurrence and propagation of spar fracture.
A procedure is proposed for rejecting girth welds based on an analysis of the main parameters of acoustic emission (AE) signals recorded during multiple-pass welding. The accuracy of locating AE ...signals recorded from defects and their filtering from noise and interference were ensured by the use of a modified tabular method and rejection grid. Normalized coefficients were calculated from the energy and amplitude of localized AE signals and used for in-process assessment of weld quality. Threshold values were determined for the normalized coefficients above which the weld is rejected. Defects in girth welds were identified using this procedure, and the possibility of determining defect hazardousness in real time was demonstrated.
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