This study investigates the stationary interacting of multiple cracks within both the interface and the embedded layer of a homogeneous half-plane coated with a functionally graded material (FGM) ...under elastodynamic in-plane loading. Leveraging the distributed dislocation technique, this research provides a novel framework for exploring the intricate fracture mechanics of this specific material configuration. To accurately quantify dynamic stress intensity factors (DSIFs) within this complex medium, the study employs the method of integral transformations. This approach involves strategically positioning Volterra-type climb and glide edge dislocations at the critical interface between the half-plane and the FG coating. To characterize the traction vector along the surfaces of multiple cracks, we construct systems of Cauchy singular integral equations using dislocation solutions. By numerically solving these equations, we precisely determine the dislocation density along the crack surfaces. This critical information then enables exceptionally accurate computation of DSIFs at the crack tips. This study's numerical findings reveal how material gradient characteristics, Poisson's ratio, excitation frequency, coating thickness, crack length and crack interactions collectively govern the DSIFs of graded coatings. These results clarify the complex mechanics of these materials under elastodynamic loading.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
A piezoelectric half-plane weakened by several horizontal cracks is investigated under anti-plane mechanical and in-plane electrical impacts. The distributed dislocation and integral transform ...techniques are employed to construct integral equations of the multiple dynamic cracks embedded in the piezoelectric half-plane. At first, the stress and the electric fields in the piezoelectric half-plane are calculated by using pattern. Then, by determining distributed dislocation density on the crack surface, a system of singular integral equations with Cauchy-type singularity is derived. The dynamic field stress intensity factors are determined by using the numerical Laplace inversion and dislocation densities. Finally, several examples are solved and the effects of the geometrical parameters and cracks configuration are graphically obtained upon the dynamic field intensity factors.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In this paper, the distributed dislocation technique (DDT) is used to calculate the stress intensity factors (SIFs) at the tip of several moving cracks which are located at the interface between two ...dissimilar non-homogeneous half-planes. In this study, in-plane loading is considered and it is assumed that the properties of the non-homogeneous material change exponentially. First, by employing Fourier and Galilean transforms, the problem of Volterra type climb and glide edge dislocation is solved at the interface of two dissimilar materials, and then the DDT is used to obtain the singular integral equations of Cauchy type. The resulting singular equations are numerically discretized and solved to obtain dislocation density on the crack surfaces to determine the SIFs. Finally, the effects of change in parameters such as gradient non-homogeneous constant, Poisson ratio, crack growth rate and interaction between cracks on SIFs are shown graphically.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
Three different types of nanofluids were prepared by dispersing γ-Al2O3, TiO2 and CuO nanoparticles in a 0.5wt% of carboxymethyl cellulose (CMC) aqueous solution. Thermal conductivity of the base ...fluid and nanofluids with various nanoparticle loadings at different temperatures were measured experimentally. Results show that the thermal conductivity of nanofluids is higher than the one of the base fluid and the increase in the thermal conductivity varies exponentially with the nanoparticle concentration. In addition to increase with the nanoparticle concentration, the thermal conductivity of nanofluids increases with the temperature. Neural network models were proposed to represent the thermal conductivity as a function of the temperature, nanoparticle concentration and the thermal conductivity of the nanoparticles. These models were in good agreement with the experimental data. On the other hand, the Hamilton Crosser model was only satisfactory for low nanoparticle concentrations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Epoxy resins have been used as structural materials since the late 1940s. Despite their desirable properties such as high strength, excellent creep resistance, and good adhesion, they suffer from low ...fracture energy. Rubber modification as a major toughening approach to overcome the inherent brittleness of epoxy polymers was introduced during the early 1970s. Since then, a large number of investigations have been conducted to elucidate different aspects of rubber-toughened epoxies. The present work is a critical review of the field focusing on the important parameters affecting rubber-toughening. The studies reviewed are classified in five categories including roles of matrix ductility, rubber concentration, blend morphology, particle cavitation, and particle/matrix interface. It has been tried to provide an in-depth view of the state-of-the-art knowledge in the field and to direct future studies towards exploring new approaches for toughening of epoxy polymers.
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BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
•In-plane analysis is performed in two FGMs half-planes containing several cracks .•In mode I/II under normal/shear traction, the DSIFs are equal at the two crack tips.•In mode II/I under ...normal/shear load the DSIFs differ in two crack tips by a minus sign.•The interaction between the crack tips in several cracks is greater than the tip of a crack.•By increasing the crack length the DSIFs of the crack tips are increased.
In this study, the dynamic stress intensity factors (DSIFs) at the tip of several cracks located at the interface between two half-planes made of functionally graded materials (FGMs) are calculated using the Distributed Dislocation technique (DDT). In this paper, the in-plane time-harmonic loading is considered and it is assumed that the properties of the FGMs follow the law of exponential function. First, the problem of two dissimilar half-planes that are weakened by an interface Volterra type climb and glide edge dislocation is solved using the Fourier transform, and then, using the DDT, singular integral equations with a singularity of the Cauchy type are extracted. To calculate the DSIFs at the cracks tips, the resulting singular integral equations are numerically discretized and the dislocation densities on the crack surfaces are obtained. Second, the graphs are presented in the numerical results section to show the effects of change in the parameters such as non-homogeneous constant, Poisson ratio, crack length, frequency and interaction between the cracks on DSIFs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Fracture analysis is carried out in a half-plane containing a climb and glide edge dislocations.•The distributed dislocation technique is used to construct integral equations for a ...half-plane.•Dislocation densities are employed to determine fields intensity factors for multiple moving cracks.•Formulation is applicable for multiple cracks with arbitrary arrangement.
In this work, the steady state problem of multiple Yoffe-type cracks propagating in a piezoelectric half-plane within the framework of linear electroelasticity under in-plane electro-elastic loading is studied. At first, the closed-form solution of the moving electric and Volterra type climb and glide edge dislocations are derived using the complex Fourier transforms to achieve the integral equations of a piezoelectric half-plane with several moving cracks. Then, the integral equations with Cauchy-kind singularity are solved numerically to determine the mixed mode stress intensity factors and the electric displacement intensity factors in a piezoelectric medium. Finally, the effects of the loading conditions, crack moving speed, cracks lengths, cracks interactions and geometrical parameters on the field intensity factors are considered.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
γ-Al
2O
3, TiO
2 and CuO nanoparticles were dispersed in a 0.5
wt.%. aqueous solution of carboxymethyl cellulose (CMC) to prepare three types of non-Newtonian nanofluids. Rheological characteristics ...of the base fluid and nanofluids with various nanoparticle concentrations at different temperatures were measured. Results show that all nanofluids as well as the base fluid exhibit pseudoplastic (shear thinning) behavior. The rheological characteristics of nanofluids and those of the base fluid are functions of temperature and particle concentrations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
In this article, the transient response of a cylinder, with a piezoelectric coating, weakened by multiple radial cracks is investigated. The problem is under torsional transient loading. First, the ...solution of the problem, weakened by a Volterra-type screw dislocation, is achieved by using Laplace and the finite Fourier sine transform. The solution is obtained for displacement and stress fields in the bar with a piezoelectric layer. At the next step, the dislocation solution is used to derive a set of Cauchy singular integral equations for analysis of bars with a circular cross section containing some radial cracks. The solution of the singular integral equations is used to determine the torsional rigidity of the cross section and also the stress intensity factors of the crack tips. In addition, several examples are presented to show the effect of the piezoelectric coating and torsional transient loading on the stress intensity factors and torsional rigidity of the system.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
We show that the quadrature LC oscillator is best treated as two strongly coupled, nominally identical oscillators that are locked to the same frequency. Differential equations that extend Adler's ...description of locking to strong injection reveal the full dynamics of this circuit. With a simplifying insight, the analysis reveals all the modes of the oscillator, their stability, the effects of mismatch on quadrature phase accuracy, and through a novel use of the analysis, phase noise.
