جستجوی مقالات مرتبط با کلیدواژه "digital image correlation (dic)" در نشریات گروه "فنی و مهندسی"

Rocks normally contain defects such as joints, cracks, and pre-existing flaws from small to large scales. The behavior of these defects is highly dependent on their geometrical characteristics and locations in the rock mass. In many cases, these cracks are located at the interface of two materials. Most of the investigations on interfacial cracks have been analytical and there are a few experimental studies available. In this study, crack initiation, growth, and coalescence of a pre-existing flaw in a rock-like material are investigated under uniaxial compressive loading. Specimens are made of two types of rock-like materials with different compressive and tensile strength. The flaw is placed at the center of specimens. Flaw width is equally distributed in both materials. To investigate the effect of geometrical parameters of the flaw on crack growth processes, rock-like specimens with different flaw angles were made. To show the repeatability of results, three identical specimens of each geometry were made. Digital image correlation technique was used for a detailed investigation of crack growth processes from initiation to failure. Nikon D7100 camera was used to take pictures of the specimen during loading. Ncorr software was used to analyze the pictures. The results showed that crack growth, coalescence, and failure pattern depended on pre-existing flaw geometry. By varying the angle of inclination from zero to 45°, the compressive strength decreased and then, increased with increasing the angle of inclination from 45 to 90°. Specimen with 45° flaw had the least compressive strength because theoretically maximum shear happens at this angle. For flaws with angles of 0 to 30 degrees, failures are caused by the growth of wing cracks. However, from 45 to 75 degrees, failures often occur with the propagation of the shear crack along the interface. At the angle of 90 degrees, a tensile crack is formed at the center of the sample along the interface. The results showed that crack growth and failure pattern depended on pre-existing flaw geometry.

The importance of understanding three-dimensional spacer fabrics properties, is a reason to the development of rapid and accurate methods for determining properties, due to their numerous applications in various industries. In most applications, spacer fabrics are affected by tension; therefore, knowing their behaviour in the encounter with tension is important. The purpose of this paper is to investigate on deformation of the spacer fabric and determine the local displacements in this fabric under tension. So, the digital image correlation method was used, that is a usual method of determining the displacements and deformation of a structure under external loading. Deformation behaviour of the diamond shape unit the of spacer fabrics structure at different tensile strains, based on experimental observations and theoretical analysis using video processing and digital image correlation method was investigated in the course and wale direction. The fabric unit deformation, the distribution of the local displacements and longitudinal and transverse strain of fabric were determined using video processing and compared with experimental method. Comparison of results showed that video processing method is able to calculate the local displacement in fabric and predict the longitudinal and transverse strain at different tensile strains with an error coefficient less than 10%.

This paper aims to calculate and compare normal anisotropy coefficients in 3D-printed and hot-compression molded micro ABS specimens. To achieve this goal, micro specimens of additively-printed and compression-molded ABS were fabricated and tested using a micro-tensile testing apparatus integrated with an optical microscope while the deformation of the specimens was recorded by a camera. Frames from this video were selected and strain distribution on a micron-sized area of interest was obtained using digital image correlation (DIC) analysis. It was shown that there exists a close agreement between DIC results and in situ optical observations. The plastic anisotropy coefficients (R-values) were then calculated from the surface strains as a function of applied strain. For this purpose, through-thickness strain component was obtained assuming plastic incompressibility condition. Results showed that both micro samples revealed an anisotropic response during plastic deformation. At low plastic strains, the printed micro specimen exhibits a more anisotropic behavior than the monolithic micro specimen. As the deformation proceeds, the normal anisotropy coefficient increases for the additively-manufactured micro specimen and decreases for the hot-pressed micro specimen.