Results 1 - 10 of 3512
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[en] A calculation procedure for the deepest point of a semielliptical surface crack is presented. The effect of loading, varying in y-direction - e.g. peak stresses - on the stress intensity factor is investigated. The calculation is made in two steps: I. Evaluation of Ksub(I) for an embedded elliptical crack. II. Evaluation of Ksub(I) for the edge crack under arbitrary normal stresses by comparing the solutions for uniform loading on the edge and the embedded crack. The weight functions for variious elliptical geometries, ranging from a circular to a straight crack front, are calculated with the following results: the data are terminated by two threshold curvres. The upper bound curve is identical with the solution for the Griffith crack. The corresponding analytical weight function is well known. The lower bound curve corresponds to a circle. Here a new, exact solution has been found. Calculations for a specific case, a plate with a surface crack, show the significant influence of the type of loading, e.g. uniform, linear, parabolic or e-function, on the stress intensity factor. (orig.)
[en] This paper proposes a dislocation annihilation model for the formation of dislocation free zone at a crack tip which may be appropriate to explain more results on DFZ investigations. (author). 17 refs, 5 figs
[en] Stress intensity factors were calculated for complete circumferential surface cracks at the outer wall of a pipe by means of the weight functions method. The pipe with an inner radius to wall thickness ratio of 10 is loaded by axial tensile stress varying through the wall. The results are compared to stress intensity factors of circumferential cracks at the inner wall of a pipe. (orig.)
[en] In this work attention is focused in the derivation of variational formulations of the constutive relationship in the form of conjugate potential functionals from which stress and strain rates are derived as elements of the corresponding sub-differential sets. The main result obtained is a pair of potential functionals. (A.C.A.S.)
[pt]Apresenta-se neste trabalho a obtencao dos potenciais elasto-plasticos tais que as taxas de tensao e deformacao, ou seus incrementos finitos, sao elementos dos respectivos subdiferenciais. O resultado mais importante neste trabalho e a obtencao de um par de funcoes potenciais aplicaveis a numerosos materiais elasto-plasticos. (A.C.A.S.)
[en] An unsteadily propagating permeable crack in piezoelectric materials (PMs) under anti plane shear mechanical loading and in plane electric loading is studied. The equilibrium equations for a transiently propagating crack in a PM are developed, and the solutions on the stress and displacement fields for a permeable crack though an asymptotic analysis are obtained. The influences of piezoelectric constant, dielectric permittivity, time rate of change of the crack tip speed and time rate of change of stress intensity factor on the stress and displacement fields at the transiently propagating crack tip are explicitly clarified. By using the stress and displacements, the characteristics of the stress and displacement at a transiently propagating crack tip in a PM are discussed
[en] A hybrid method for photoelasticity is introduced and applied to the plane problems of isotropic polycarbonate plates with a central crack under uniaxial and equal biaxial tensile loads. Also, the influences of equal biaxial tensile loads on the isochromatic fringes, stress fields and stress intensity factors near the mixed mode crack-tip have been investigated. The results show that, when an equal lateral tensile load is added to the specimen under uniaxial tensile load, the asymmetric isochromatic fringes about the line of crack gradually become symmetric, and the slope of the isochromatic fringe loop near the crack-tip is inclined towards the crack surface according to the increasing of the inclined angle of crack. Furthermore, the shapes of distribution of all stress components are changed from asymmetric to symmetric. In the equal biaxial tensile load condition against the uniaxial tensile load condition, the values of stress intensity factors are changed little, and only the region of compressive stress of σx /σ0 is changed when β = 0 .deg., but the values of KI/K0 are increased and those of KII/K0 become almost zero, namely, we have the mode I condition when β =15 .deg.∼45 .deg.
[en] The optical method of reflected and transmitted caustics has been utilized in mechanics investigations. This relatively new experimental technique has been successfully applied on various fracture analysis such as static and dynamic crack propagation studies, some elasticity problems and contact stress, etc, In this study, the stress intensity factors in thin polycarbonate specimens, a kind of optically anisotropic material, under Mode I loading condition are estimated by the method of caustics. The values of stress intensity factors obtained from theoretical caustics shape are compared by the experiment. It is confirmed that the two stress intensity factors agree well with Srawley's solution
[en] The Simulation calculation module and the SolidWorks software package have helped to define the optimal shape and dimensions of single-welded joints which may serve the basis for calculating the process parameters of welding. Having compared the models with different weld cross-sections the authors have defined that the weld height and width do not significantly affect the stress concentration, and the stress concentration and value mainly depend on the shape of the root bead and the gap size between the welded parts.
[es]El módulo de cálculo de simulación y el paquete de software solidworks han ayudado a definir la forma y las dimensiones óptimas de uniones soldadas simples que pueden servir de base para calcular los parámetros de proceso de soldadura. Habiendo comparado los modelos con diferentes secciones transversales de soldadura, el autor ha determinado que la altura y el ancho de la soldadura no afectan significativamente la concentración de tensión, y la concentración y el valor de la tensión dependen principalmente de la forma del latido de la raíz y del punto de separación entre las partes soldadas.
[en] We determined the fracture toughness of aluminum curved thin sheets using tensile stress tests and finite element method. We applied Linear elastic fracture mechanics (LEFM) and Feddersen procedure to evaluate stress intensity factor of the samples with central wire-cut cracks and fatigue cracks with different lengths to investigate the notch radius effect. Special fixture design was utilized to establish uniform stress distribution at the crack zone. Less than 9 % difference was found between the wire-cut and the fatigue cracked samples. Since generating central fatigue crack with different lengths required so much effort, wire-cut cracked samples were used to determine critical stress intensity factor. Finite element analysis was also performed on one-quarter of the specimen using both the singular Borsum elements and the regular isoparametric elements to further investigate fracture toughness of the samples. It was observed that the singular elements presented better results than the isoparametric ones. A slight difference was also found between the results obtained from finite element method using singular elements and the experimental results.