PIPE RING TENSILE SPECIMENS STRAIN MEASUREMENT

Abstract

For various pipe manufacturing methods, data on the pipe's strain and stress state in the circumferential direction is necessary (e.g. in the oil industry, the process of manufacturing seamless pipes with a conical shaft). The purpose of this research is to create a method for determining the strain and stress behaviour of Pipe Ring Tensile Specimens (PRTS) in the hoop direction. The absence of official methods for assessing a PRTS suggests that it could be developed. The implementation of the digital image correlation approach for evaluating plastic PRTS is discussed in this research. A specially constructed steel instrument with two D blocks is used to test PRTS. Two D-shaped mandrels are fixed on the tensile tool and tensile testing equipment, and a 3D printed PRTS is placed over them. The three-dimensional Digital Image Correlation (3D DIC) approach was used to capture the strain evolution in the gage length of the specimens. All specimens are 3D scanned to evaluate the geometry of the PRTS cross-section following fracture. Six groups of PRTS were studied, with three different filling percentages (60, 90, and 100 percent) and two different geometric kinds (Single and Double PRTS). The results reveal that the kind and percentage of filling, as well as the printing method, affect material behaviour; however, the methodology using a DIC system, 3D printer, and scanner is an excellent tool for mapping entire strain fields in PRTS and thereby defining pipe mechanical properties.