RESEARCH OF GLASS BEAMS FOR FOUR-POINT BENDING USING THE METHOD OF DIGITAL IMAGE CORRELATION

Abstract

The main elements of glassstructures commonly used in construction arebending elements. The use of glass beams with alarge ratio of cross-sectional height to width is mostoften encountered in practical use. This type ofstructure is characterized by the phenomenon of lossof stability from the plane.Optical research methods are becoming moreand more popular due to the convenience and lackof direct contact with the test specimen. Such aresearch method is the method of digital imagecorrelation. In general, the method requiresspecialized hardware and for a single experimentwithout the need to record images at high speed, itis also promising to use a publicly available user'smirrorless camera as a recording device.The subject of the study was glass beamssubjected to four-point bending. Six double-layerglass beams were manufactured for the study. Thebeams were tested with a stepwise increase in loadon a special test rig made for the study of glassbeams. The relative deformations were recordedusing the method of correlation of digital imagesand mechanical strain gauges.The paper describes the method of usingmirrorless cameras with a colour matrix to studyglass beams in four-point bending. Themethodology consisted of selecting the rightequipment and determining the characteristics ofthe camera to obtain more information from theimages and prepare them for analysis. The imageswere de-colorized and the white balance wasadjusted using a photo editor. The images ready foranalysis were transferred to the specialized softwareGOM Correlate Pro.The glass beams were tested for four-pointbending. The values of the maximum stresses wereobtained using the equilibrium equation of thesection, the relative deformations obtainedaccording to the readings of mechanical devices,and the method of correlation of digital images.Failure of the glass beams occurred in layerswith the initial crack formation in the lowe mosttensile zone, then the crack propagated with a tuliplike pattern to the upper zone.The study confirmed the disadvantage of glassbeams with a large height-to-width ratio, namely theloss of in-plane stability.The method of digital image correlation usingpublicly available user hardware performed well,often showing values of destructive stresses close tothe theoretical values obtained by calculation. It isrecommended to use this method for furtherresearch