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Go to Editorial ManagerThe ultimate objective of this study was to compare the performance of repaired edge cracks in steel plates before and after repair with patches made of steel patch and glass fiber-reinforced polymer composite patches (GFRP) in different shapes: circular, rectangular, and trapezoidal, under two conditions: unsymmetric patch (one patch) and symmetric patch (two patches). A three-dimensional finite element model of the one-sided and two-sided repaired examples is used to study how the steel and composite patch affect the stress intensity factor (SIF). Under uniaxial tensile loads, the use of steel patches and GFRP composite patches to repair cracks was studied. The results showed that the steel patch performs better than the GFRP patch because it significantly lowers the stress intensity factor (SIF). The symmetric patch arrangement (two patches) is better than the un-symmetric patch arrangement (one patch) because it significantly reduces the stress intensity factor (SIF).
This paper presents the effect of fiber orientation angle on the stress intensity factor SIF for carbon epoxy composite plates with single-edge, center, and inclined cracks of varying lengths under tensile load. The stress intensity factor and shape factor were calculated individually for each case, with nine different fiber orientation angles computed using the extended finite element method XFEM concepts. It is found the stress intensity factor increases with increasing crack lengths while the shape factor decreases. In the case of single edge cracks, the SIF increases in the average value reached (173 %) for composite plates with different fiber orientation angles, while in the case of the center crack, the average value of SIF reaches (81 %). It was observed in this study that the increases in stress intensity factor and the decreases in the shape factor with different crack lengths were more stable in the composite plate with a fiber orientation angle of 75°. The higher values of SIF at an angle of 75° are because of the high probability of fiber slippage at 75° due to induced shear stresses in addition to the tensile stresses at the fiber-matrix interface. As a result, the crack tip has a high-stress intensity factor.
In this paper, the Weibull uni-axial and multi-axial distribution function for polyethylene pips under pressure loading were developed and analyzed taking account of residual stress. Tensile test was achieved to determine mechanical properties and the Weibull parameters. Experimental method using the hole- drilling strain-gage method was used to measure the residual stresses in PE pipe and compare with that obtained from numerical finite element method (FEM). The obtained results show that there is a convergence between uni-axial and multi-axial distribution function, but multi-axial distribution function give large values compared to uni-axial distribution function. It was observed that the residual stresses have influence on failure assessment diagram and causes translation from elastic-plastic failure to brittle failure.
The principle aim of this research is concentrated to analyze the effect of cracks and their propagations on the mechanical behavior of a quasi-brittle material such as concrete. The singularity (stress concentration to infinity at the tip of crack) is avoided by using the principal of fracture energy with the fictitious crack approach. The concrete crack is divided into two major zones; the first one is the fracture zone (a combination of bridging effect and the cohesive microscopic cracking) which obeys a special law permitting the transmission of stress across the two faces of crack, this zone is considered as partially cracked concrete. When the opening of the crack exceeds a specific value, this zone is converted to a real crack (an open crack) and cannot transmit any stress across the two faces of a crack. The program of finite element used in this research is prepared by the researcher using discrete-crack approach with the experimental data obtained from the flexural test on notched beam loaded under three-point bending, where fracture mode I is dominated. The response of the applied load-crack mouth opening displacement (CMOD) with appropriate fracture energy is selected. The results show that the cohesive microscopic cracking zone for the plain concrete is very wide. The cohesive stress distributions across the microcracks with the corresponding crack openings are drawn from the first crack appearance till the beam failure.
The main objective of this study is to investigate the effect of repeated load on the strength and behavior of the spandrel beam by considering eight specimens divided into four groups based on the design methods; type of cross-section of the spandrel beam and the type of loading. Two design methods, two types of loading and two types of cross sel.1ions for spandrel beam are considered, the first is a solid rectangular section, while the other is a hollow rectangular section. The effect of repeated loads on the crack's width, deflections, torque, and angle of twist is studied using two stages of loading, the first stage is at the soft-cracking stage after the occurring of cracks in the spandrel beam and the second stage is the yielding of the bottom longitudinal reinforcement of the floor beam.
Fracture mechanics approach is important for all mechanical and civil projects that might involve cracks in metallic materials the purpose of this paper is to determine a crack tip opening displacement fracture toughness experimentally, also study the effect of thickness on CTOD fracture toughness of low carbon steel and study the effect of Wire Electrical Discharge Machine (WEDM) to have a pre-crack, instead of fatigue pre-crack by using a CT specimen of low carbon steel with a thickness of (8,10, and15 mm), a width of 30mm, crack length of 15mm, and pre-crack of 1.3mm for all samples, this dimension according to ASTM-E399-13, by pulling the specimen in a 100 KN universal testing machine at a slow speed rate of 0.5 mm/min, the load applied on the specimen is generally a tension load. The crack tip plastically deforms until a critical point P C at this moment a crack is initiated. The computer-controlled universal testing machine gives the value of the load and the displacement transducer gives a crack mouth opening displacement. Critical crack tip opening displacement CTOD is found with the plastic hinge model (PHM) method. The result showed the stress intensity factor K I increases with increased loading in the elastic region and t he thickness effect refers to the effect of the plastic zone at the crack tip on the stress intensity factor, In a thin specimen, a plastic zone is large at the fracture tip leads to a high-stress intensity factor at the fracture tip but in the thick specimen, on the other hand, has a small a plastic zone and a low-stress intensity factor around the crack tip. The fracture toughness is found to increase with an increase in the thickness of specimens.