چكيده به لاتين
With the development in material engineering and the increase in the strength of various materials used in engineering structures, brittle fracture as one of the dominant fracture modes has been studied by many researchers. Therefore, from engineers and designers point of view, it is important to accurately assess the fracture toughness as a material resistance to the crack extension in materials due to critical conditions in the bodies containing cracks, notches, cavities, material porosity, or a combination of them. Because, the occurrence of faults and errors is common at all phases, including the pre-production, manufacturing, even when using components. In this thesis, the fracture toughness of PMMA and carbon steel materials are experimentally and numerically examined. The tensile testing machine has been employed for experimental tests, and Abaqus software has been utilized for finite element analysis. In order to perform the experimental test, the SENT specimen has been considered under two different boundary conditions, including clamped and pinned. The effect of various specimen lengths and supports on the results has been investigated. The results show that, while the specimen is under the pin condition, it does not have much effect on the test and modeling results by increasing the sample length, because in this support type the rotation constraint is free, and the sample can rotate freely on both sides from the beginning of the tensile test and therefore lead to more accurate results. However, in the event that the clamp connetion had been considered for the specimen, different results could be achieved due to the constrained rotation in various sample lengths. This is because there is no rotation in the upper grip during tension testing, and the smaller the sample length, the shorter the distance from the upper grip to the crack which leads to less opening of the crack mouth, and as the length of the sample increases, more rotation occurs in the specimen, and the crack mouth opens growingly, resulting in different values of stress intensity factors as well as different fracture loads. As a result, designing based on the fracture toughness obtained from the sample, which has pin connetion, will be more accurate.
