Determination of fracture parameters of the cracked plate with stress concentrators in the process of elastic-plastic deformation
Background. Defects divided into two classes according to the effect on the stress-strain state of structures: classic defects are defects with a finite radius of curvature at the top, and cracks or crack-like defects. Crack-like defects are the most dangerous. Crack-like defects have a sharp apex with almost zero radii. The main parameter characterizing the level of stress concentration of such defects is the stress intensity factor. Assessment of the impact of defects on the mechanical and operational properties of the object of control by conducting destructive tests is not always profitable from the economic point of view. Therefore, currently at the stage of engineering product design methods of linear fracture mechanics widely used to assess the performance and period of operation of the most important parts with crack-like defects. Materials and/or methods. The methodological importance of this study is to develop an algorithm for solving the problem of calculating the stress-strain state of parts with a defect, including the study of fracture characteristics depending on the defect. Practical interest is the question of assessing the stress changes in the parts with unloading holes. The calculation of fracture toughness based on the force fracture criterion by Irvine used when building an algorithm. Calculation of the maximum stress intensity factor along the crack front carried out using the method of finite elements in the ANSYS software package. 8-node plane elements used to create a finite element model with a crack, and special singular finite elements used to describe the features along the crack front, Results. The given algorithm allows calculating such strength characteristics of the control object as the values of the J-integral. The addition of unloading holes and patches close to the crack top allowed assessing their impact on the crack not leading to significant stabilization but reducing the value of the J-integral. Conclusion. Thus, the obstacles in the form of stiffer patches reduce the values and allow increasing the limit load, and as a result, the crack remains stable in a larger range of loads.