Дерусова Д.А., Вавилов В.П. «Неразрушающий контроль материалов методом резонансной ультразвуковой инфракрасной термографии» В мире неразрушающего контроля, 19, № 1, с. 21-23 (2016)

Описаны результаты исследований в области маломощной резонансной ультразвуковой инфракрасной дефектоскопии, основанной на использовании собственных резонансных частот дефектов и регистрации локальных температурных сигналов с помощью тепловизоров. Экспериментальные результаты приведены для дефектов в углепластике. Introduction. The paper contains new results on infrared thermographic nondestructive testing of composite materials by applying low-power ultrasonic stimulation. Method. A sample made of carbon fiber reinforced plastic was ultrasonically stimulated in the milliwatt to watt power range. The frequencies which corresponded to local defect resonances were determined by means of a laser vibrometer. Results. Images of both temperature and vibration amplitudes were obtained to demonstrate potentials of low-power ultrasonic infrared thermography. Practical application of this technique was in the inspection of impact damage in graphite epoxy composite. Conclusion. It was shown that defect stimulation at resonant frequencies ensures damage-free testing procedure where temperature signals in defect sites can be reliably detected by contemporary infrared imagers. In some cases, air-couple technology also provides reasonable results of defect detection due to the resonant character of material excitation.

Трифонова С.И., Генералов А.С., Далин М.А. «Современные технологии и средства теневого ультразвукового контроля полимерных композиционных материалов» В мире неразрушающего контроля, 19, № 1, с. 31-35 (2016)

Рассмотрены четыре способа создания акустического контакта при проведении ручного теневого ультразвукового контроля. Оценена возможность и эффективность их применения для контроля трехслойных конструкций с сотовым и вспененным заполнителями и клеевых соединений. Показана достигаемая при контроле чувствительность в зависимости от особенностей конструкций и используемого способа создания акустического контакта. Осуществлен обзор современного оборудования. Introduction. Typical aviation constructions of polymer composite materials, which can be inspected with Through Transmission Ultrasonic Technique (TTUT), include sandwich panels with fillers of different types and bonded constructions. Depending on the required sensitivity, material acoustic characteristics and available equipment, there are several ways of acoustic contact creation using different probes: contact probes with a silicone protector; wheel probes; air coupled probes; water coupled non-contact probes. The task of the research was to determine the most reliable type of the acoustic contact for defect detection in dependence on the type of a polymer composite construction.Method. A set of specimens was made for the research, which included 10 sandwich panels with polymer honeycomb fillers of different heights and comb sizes, 2 sandwich panels with foamed fillers of different heights and 2 bonded constructions with different adhesives. In every specimen were made artificial defects. The experiment included defect detection and measuring in all the specimens with TTUT for all types of acoustic contact creation. Results. The experiment enabled requirements for the TTUT parameters to be formulated; efficiency of each type of acoustic contact creation to be defined. The recommendations on TTUT usage for every type of the construction were given. Conclusion. The research results have confirmed the efficiency and good perspectives of TTUT usage for non-destructive testing of polymer composite constructions.

Бобров В.Т., Шевалдыкин В.Г. «Многократные ультразвуковые эхо-сигналы в пластине. анализ и применение» В мире неразрушающего контроля, 19, № 1, с. 36-39 (2016)

При контроле плоскопараллельных изделий прямыми ультразвуковыми преобразователями на экране дефектоскопа обычно присутствует множество эхо-сигналов, повторяющихся через равные промежутки времени. В то же время между ними можно наблюдать значительно меньшие по амплитуде импульсы с неодинаковыми интервалами повторения. В статье показано, как можно определить время появления любого их этих импульсов, исходя из того, что при возбуждении и каждом отражении ультразвуковой волны от поверхности изделия возникает также и трансформированная волна другого типа. По измеренным интервалам времени между парами первых импульсов можно вычислить скорости обоих объёмных волн в изделии. Introduction. Multiple echo signals arise within a plate being tested with a normal ultrasonic transducer. Besides some weaker pulses with unequal recurrence intervals are seen on the screen. Although their amplitude is rather small, they can prevent the device, for example a thickness gauge, from normal operation. The task was to ascertain the reasons and to determine the points of time when these weak pulses arise. Method. Any mechanical perturbation of the solid body’s surface generates a pair of ultrasound waves that propagate into its volume. The plate was tested with longitudinal and transversal ultrasonic waves originated by different normal transducers; the waves’ velocities in the plate material were known. Thus the time points when several initial pulses were to come to the oscillogram were calculated. Results. The coincidence of the measured time points with the calculated ones showed that each small pulse is a result of ultrasonic signal propagation within the plate thickness: one or more times as a longitudinal wave and one or more times as a transversal wave. Strict determinateness of pulse registration points for all the pulses, depending only on the plate thickness and the actual sound velocities within the plate, allows the both velocities and a Poisson ratio to be measured using any of a normal transducer, including a piezoelectric transducer of longitudinal waves. When the ratio «transversal wave velocity / longitudinal wave velocity» is equal or close to 0.5, some pairs of pulses or more arise at the same point of time. Conclusion. The given simple way to measure a velocity of both transversal and longitudinal waves makes it possible to evaluate physical and mechanical properties of the material.