A single fracture-mechanics based method is described for assessing a part-through crack in the wall of a pipe subjected to internal pressure of liquid and/or gas. The method utilizes simple approximate expressions for determining the fracture parameters K, J, and employs these parameters to determine critical dimensions of crack on the basis of equality between the J-integral and the J-based fracture toughness of the pipe steel. The crack tip constraint is accounted by the so-called plastic constraint factor C, by which the uniaxial yield stress in the J. integral equation is multiplied. The results of the prediction of the fracture condition are verified by burst tests on test pipes. and Obsahuje seznam literatury
This article describes a theoretical study of non-linear fracture behavior of the Double Cantilever Beam (DCB) configuration. The fracture is analyzed using the J-integral approach. A stress-strain curve with power-law hardening is used for describing the mechanical response of the DCB. It is assumed that the material has the same properties in tension and compression. A model based on Mechanics of materials is applied to find solutions of the J-integral at different levels of the external load. The effect of the exponent of the power law on the non-linear fracture behavior is evaluated. It is found that if higher values of the exponent of the power law are used, the J-integral value increases. The analytical approach developed here is very useful for parametric investigations, since it captures by relatively simple formulae the essential of the non-linear fracture. and Obsahuje seznam literatury
The contribution deals with finite element analysis of stress state in sub-sized pre-cracked three-point bend specimen (KLST). A studied material was Eurofer ‘97 steel. The true stress-true strain curve was obtained from tensile test. The three-point-bend tests were carried out on pre-cracked plain and side-grooved specimens at ambient temperature. Performed tests were simulated using FEA software ABAQUS 6.10. The stress state in KLST specimen was compared with the stress state of pre-cracked Charpy and 1T SENB. The analysis confirmed the stress state of standard fracture toughness determination because loss of crack-tip and out-of-plane constraint. and Obsahuje seznam literatury