539.3
4

механіка руйнування
тріщина
експеримент
відеозйомка
параметри навантаження
fracture mechanics
crack
experiment
videodgraphy
loading parameters

Цифрова відеозйомка, яка дозволяє здійснювати прямі вимірювання геометричних параметрів профілю тріщини широко застосовується в експериментальній механіці руйнування. Проте часто, особливо при вивченні швидкоплинних нестаціонарних процесів руйнування, за відсутності апаратного зв’язку відеокамери з випробувальною машиною виникає проблема встановлення значень, які мали параметри навантаження зразка у моменти фіксації відеокадрів профілю тріщини. Для вирішення цієї проблеми розроблено й перевірено відповідну методику.
Digital videography, which makes it possible to accomplish direct measurements of geometric parameters of the crack profile in real time, finds wide use in experimental fracture mechanics. Practical implementation of videography in conducting experiments frequently faced difficulties due to the lack of synchronization between the processes of recording of the specimen loading parameters and videography. To solve this problem, a procedure for synchronization between the recording of the specimen loading parameters with an extending crack and videography of the crack profile using the testing machine controller together with digital CMOS-videocamera has been developed and approved. For mutual compliance of the loading and videography processes it is required to use some process, which is simultaneously recorded by means of controller and videocamera, as a binding element. For two registration systems this process occurs at initial instants of time (t0)mach and (t0)video. For any video frame at the instant time tvideo time interval since the beginning of videography is determined as Δt = tvideo – (t0)video. The loading parameters at this instant time is determined as tmach = (t0)mach + Δt. The instant of turn-off time for laser marker governed by digital controller output is used as such process. Thin-sheet metallic specimens have been tested for verification of synchronization. Measurements of the crack length are concurrently performed using the procedures of digital optical macrovideography and digital microvideography. The results of measurements of the crack length in accordance with both procedures are in a good agreement with each other.

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