Papers by Keyword: Stress Intensity Factor (SIF)

Abstract: This study investigates the stress intensity factors (SIFs) in cylindrical pressure vessels with nozzles, focusing on the effect of nozzle offset on crack behavior. Cracks are positioned on the inner wall of the cylinder at the nozzle intersection, and their location remains constant while the nozzle is systematically offset on the cylindrical surface. The analysis aims to determine how varying nozzle positions influence the SIFs, providing critical insights into structural integrity under different loading conditions. The study employs finite element analysis (FEA) to model the stress distribution and crack propagation behavior for various nozzle offset scenarios. Results highlight the sensitivity of SIFs to nozzle displacement and emphasize the importance of precise positioning in pressure vessel design to prevent crack propagation and failure. These findings offer practical implications for optimizing pressure vessel and nozzle designs in industrial applications, ensuring enhanced safety and reliability.

Abstract: The defects or micro-cracks that exist in a product mass from the elaboration phase, can extend controlled or not, because of a variable solicitation applied to a product or a sample. The Fracture Mechanics parameter that highlight the crack propagation in time is its rate growth marked as da/dN and represents the crack advancement length during a solicitation cycle. This can be studied based on some mathematical models obtained from some propose models, experimentally determined. In this paper, a propagation process analysis is made of a fracture crack by an axial-eccentric fatigue loading for a 10TiNiCr175 stainless steel. CT type flat samples were loaded with an asymmetry coefficient R= 0.3, for the solicitation temperatures: T= 293K (20°C), T= 253K (-20°C), respectively T= 213 K (-60°C). The crack growth increase was studied by three most used mathematical models: the polynomial method standardized according to ASTM E647, method proposed by Paris and method proposed by Walker.

Abstract: Bone fracture can occur in all parts of human skeletal cortical bone including phalanx bone of finger bone. Sometime, it leaves permanent damage and a long period of recovery. This situation can be prevented if we understand the mechanics and the process of the bone fracture. This study aims is to evaluate stress shielding induced by crack interaction using a simple model on Linear Elastic Fracture Mechanics (LEFM). Numerical simulation had been carried out in this study to understand the stress shielding induced by crack interaction. The results revealed that the interaction of two cracks is directly proportional to the stress intensity factor (SIF) magnitude at crack tips. Finally, as the crack-to-width ratio increase and the strain energy release rate also increased.

Abstract: Failure of weld joints under single and cyclic pulsating loading conditions is under consideration. A weld joint is modeled by three-layer composite. Stepwise propagation of the internal I mode crack under cyclic loading is investigated. Delamination of bimaterial composed of two structured materials is considered when a crack is located at the interface between two media. Loads under pulsating loading conditions are studied for elastic-plastic material. For analysis of this process, diagrams of quasi-brittle fracture of solids under cyclic loading conditions are proposed to be used. One of curves of the proposed diagram bears resemblance to the Kitagawa-Takahashi diagram. Estimates of average dimensionless velocity of stepwise crack propagation per loading cycle have been obtained in an explicit form for plain specimens of finite width. The relations derived for the average crack growth rate can be considered as structural expressions for plotting Paris’ curves.

Abstract: Using the method of complex analysis, the paper investigates the plane elasticity problem of circular orifices with four-cracks through conformal mapping, and provides an exact analytical solution for the crack-tip stress intensity factor (SIF). From this we have simulated circular orifices with three-cracks, symmetrical four-cracks, asymmetrical collinear double-cracks, and symmetrical collinear double-cracks; as well as the crack problems of asymmetrical cross-shaped cracks, symmetrical cross-shaped cracks, and T-shaped cracks.

Abstract: In this paper, the evaluation of the SIFof a macrocrack in interaction with one or several microcracks in a material containing a geometrical defect was investigated. Several configurations were considered in order to apprehend the mechanisms induced by the interaction effect and in particular the effects of reduction and/or amplification of the stress field between macro and single or multiple microcracks. The obtained results show that, macro–microcrack spacing is an important parameter if the microscopic crack is relatively close to the macrocrack-tip. The macrocrack has the tendency to accelerate as it propagates towards the microcrack. When the relative distance characterizing this spacing is higher than 0.3, the interaction effect can be neglected and the SIF remains unchanged for both defect types. When this ratio is lower than 0.3, the interaction between the two defects becomes significant and the stress intensity factor at the macrocrack tip strongly increases.

Abstract: 5XXX aircraft skin aluminum alloy needs relatively high fatigue performance to sustain complex pneumatic loading in service. Stress intensity factors are important parameters to compute fatigue crack propagation rate. XFEM was used to calculate the crack tip stress, as well as stress intensity factors (SIF) and fatigue crack propagation rate on the 5E62 alloy. Simulation results showed that the values of SIF calculated by XFEM were quite close to the theoretical values. Both the values of crack tip stress and SIF increase as crack length increasing in Paris region, resulting the increasing of fatigue crack growth rate. Fatigue crack propagation rate calculated by XFEM are consistent with the theoretical values and experimental values in Paris region.

Abstract: Using the method of complex analysis, the study investigates the circular orifice problem for 2^k periodic radial cracks through constructing conformal mapping, and provides an analytical solution for the crack-tip stress intensity factor (SIF). From this we have simulated the circular orifice problems of cross-shaped cracks, symmetrical eight-cracks, single cracks, symmetrical double-cracks, and symmetrical four-cracks.

Abstract: Using the method of complex analysis and by constructing conformal mapping, the study investigates the plane elasticity problem of star-shaped cracks and provides an analytical solution for the stress intensity factor (SIF) of crack-tip type I and II. Problems of the classic Griffith crack, the cross-shaped crack, concurrent uniformly distributed three-cracks and symmetrical eight-cracks are also simulated.

Abstract: The theory of linear elastic fracture mechanic (LEFM) has proven that we can evaluate the amount of stress located at the crack tip by determining the stress intensity factor (). The stress at the tip of a sharp crack has the highest stress which can lead to failure on the material. Thus, the cracks within human bones are quite complicated because of the bone microstructure. There are a few factors that can minimize the effect of the cracks so that patients can heal much faster. Hence, this paper focuses on how several crack distances, between two parallel edge cracks can affect the value of stress intensity factor (). Using the LEFM theory, the interaction between two neighboring crack tips was investigated.