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In this research, the cohesive length of various rock types is measured using quantitative fractography alongside a recently developed multifractal analysis. This length is then utilized to gauge material cohesive stress through the theory of critical distances. Furthermore, the fracture process zone length of different rings sourced from identical rocks is assessed as a function of ring dimensions and experimental measurements of fracture toughness, in accordance with the energy criterion of the finite fracture mechanics theory. Subsequently, employing the stress criterion within coupled finite fracture mechanics, the failure stress corresponding to the fracture process zone is determined for various rings. Ultimately, through interpolation, the critical stress corresponding to the cohesive length, quantified via quantitative fractography, is approximated. Remarkably, the cohesive stress values derived from both methodologies exhibit perfect alignment, indicating the successful determination of cohesive length for the analyzed rock materials. The study also delves into the significant implications of these findings, including the quantification of intrinsic tensile strength in quasi-brittle materials and the understanding of tensile strength variations under diverse stress concentrations and loading conditions. [ABSTRACT FROM AUTHOR]

This research focuses on the numerical investigation of fracture loads of U‐notched specimens made of Al‐6061‐T6 and Al‐5083 under pure opening mode and mixed mode I/II loading conditions. A new methodology is introduced with the aid of the equivalent material concept (EMC) combined with the extended finite element method (XFEM) and linear cohesive zone model (CZM), and the outcomes are compared with a conventional elastic–plastic damage model. The combination of EMC and XFEM result in the numerical EMC‐XFEM model, which provides a fast and accurate method to assess the notch fracture loads and crack growth path. Considering the experimental results, a trial and error loop is performed to calibrate the ductile damage model, which is much more cumbersome than the proposed EMC‐XFEM model. Moreover, the computational cost of elastic–plastic model is much more than the EMC‐XFEM model, although both approaches provide appropriate predictions for fracture of ductile aluminum notches. Highlights: The EMC is combined with XFEM and CZM for fracture prediction of ductile U‐notched.The model is validated with the mixed mode fracture results of two ductile aluminums.The results are also compared with the numerical method of ductile damage.The accuracy and time‐efficiency of the EMC‐XFEM method is proven. [ABSTRACT FROM AUTHOR]

In this work, the application of the Average Strain Energy Density (ASED) criterion for the estimation of failure loads in materials with nonlinear behavior containing U-shaped notches is presented. The ASED criterion was originally defined to predict failure in the presence of notches in materials with linear-elastic behavior. However, most structural materials (e.g., ferritic-pearlitic steels) can develop non-linear behavior (e.g., elastoplastic). In this sense, this work proposes to extend the use of the ASED criterion to materials that exhibit plasticity by a thorough calibration of their characteristic parameters, and the subsequent extrapolation of the liner-elastic formulation of the ASED criterion to non-linear situations. To validate this methodology, a wide range of structural steels (S275JR, S355J2, S460M, and S690Q) were used operating in the ductile-to-brittle transition range, with six different notch radii (0 mm, 0.15 mm, 0.25 mm, 0.50 mm, 1.0 mm, and 2.0 mm). The results obtained demonstrate that the proposed calibration of the ASED criterion allows for accurate predictions of failure loads. Therefore, it is shown that, for the notch radii analyzed in this work and for testing temperatures within the material ductile-to-brittle transition range, it is possible to extrapolate the ASED criterion to obtain estimates of failure loads in materials with U-shaped notches that exhibit ductile behavior. [ABSTRACT FROM AUTHOR]

This article deals with the investigation of delamination effects on the flutter behavior of a composite wing subjected to unsteady aerodynamic loads by providing an integrated procedure using exact methods. For this purpose, an undamaged wing structure is modeled as a cantilevered Bernoulli–Euler beam with coupled bending–torsion and delaminated wing structure is modeled as three interconnected intact beams. The modal analysis of the intact and delaminated beams is performed and mode shapes are obtained based on the development of the dynamic stiffness matrix, a computer code and an iterative method. The fundamental modes of the intact and delaminated beam derived from the free vibration analysis are used in Galerkin's method and the flutter and divergence speeds are obtained with aerodynamic forces applied. In fact, modified shape functions were developed to reflect the delamination effect in the aeroelastic analysis. Also, for the unsteady aeroelastic analysis, an iterative algorithm is developed. It was found that the delamination location and its length can have a positive or a negative influence on the flutter behavior of the wing which depends on the fiber angle. [ABSTRACT FROM AUTHOR]

This paper examines the fracture of AA6061‐T6 specimens with ductile behavior having notches with keyhole geometry under combined loading of tension/torsion. The investigation is performed by theoretical and experimental methods. New fracture tests are performed using a loading fixture on the samples made of AA6061‐T6 weakened by keyhole notches with different notch tip radii. For theoretically estimating the onset of fracture in the tested notched specimens, a concept called "Fictitious Material Concept (FMC)" is used to equate the ductile material with a fictitious brittle material. Therefore, use of this concept allows use of the linear elastic brittle fracture criteria for ductile materials. The brittle fracture criteria utilized are the "mean stress (MS)" and "maximum tangential stress (MTS)" criteria. The small difference between the theoretical and experimental results confirms that use of the combination of FMC with the two criteria is successful in predicting failure of the keyhole notched AA6061‐T6 samples. [ABSTRACT FROM AUTHOR]

The equivalent material concept (EMC) assumes that the ductile material has a valid K‐based fracture toughness (KIc or Kc). For ductile materials with significant strain‐hardening, no valid KIc or Kc is determined by the standard experiments and, hence, EMC seems null. The modified EMC (MEMC) is proposed in this study by which a virtual Kc value is defined and computed for the ductile material with significant strain‐hardening. In this way, Mode I and mixed Mode I/II fracture behaviors of U‐notched aluminum alloy 5083 are assessed in the view points of experiments and theories. Several U‐notched rectangular samples are used for performing the experiments and obtaining the failure loads. Then, the MEMC is coupled with the maximum tangential stress and mean stress criteria and utilized to predict the failure loads theoretically. Finally, it is shown that both the MEMC‐stress‐based criteria can provide very good predictions of the test data. [ABSTRACT FROM AUTHOR]

The main purpose of the present research paper is to investigate applicability of a new energy‐based failure prediction model, called EMC‐J criterion, to predict the critical loads of U‐notched polymeric samples having a ductile behaviour and loaded under symmetric 3‐point bending. The evaluated polymeric single edge notch bending samples containing U‐notches failed by considerable plastic deformations around the notch border, making it inappropriate to directly use classic linear elastic‐based formulations. Due to the elastic‐plastic behaviour of the tested polymeric material, EMC‐J criterion is applied to avoid using complex and extremely time‐consuming nonlinear analysis for failure load predictions. Finally, it is shown that EMC‐J criterion can provide a good consistency between the experimental and theoretical results with an average discrepancy of about 10%. [ABSTRACT FROM AUTHOR]

The main goal of this paper is the application of the Strain Energy Density (SED) criterion and the Theory of Critical Distances (TCD), both of them in combination with the Equivalent Material Concept (EMC), to predict the fracture loads of aluminum alloy Al7075-T651 Compact Tension (CT) specimens containing U-shaped notches. For this purpose, 45 fracture tests were performed combining two rolling orientations (transverse and longitudinal) and 6 notch radii, which cover from crack-type defects (0 mm) up to 2 mm-notch radius. Crack-type specimens are used to define the fracture properties of the material and the rest of the tests are used to check and compare the experimental fracture loads with the loads predicted using the different aforementioned criteria: SED, EMC-SED and EMC-TCD. The theoretical results of the fracture load predictions for the virtual brittle material obtained employing the EMC are in good agreement with the experimental results reported for real samples. [ABSTRACT FROM AUTHOR]

Fracture investigation of U-notched E-glass/epoxy laminated composite specimens with various notch root radii is performed under mixed mode I/II loading conditions both experimentally and theoretically. Rectangular E-glass/epoxy composite laminates with two numbers of ply (8-ply and 16-ply) and the quasi-isotropic [0/90/+45/–45]s lay-up configuration are fabricated for conducting the fracture tests. To measure the damage initiation angles (DIAs) and the last-ply-failure (LPF) loads of the fabricated composite samples containing horizontal and inclined U-notches, as the main aim of this study, the specimens are loaded under tension by the universal testing machine. The experimental LPF loads are theoretically predicted with the aid of a novel concept, called the Virtual Isotropic Material Concept (VIMC). The proposed VIMC is linked to the two well-known stress-based fracture criteria, namely the maximum tangential stress (MTS) and the mean stress (MS) criteria, in the context of the linear elastic notch fracture mechanics (LENFM). It is proved that the two combined criteria, namely the VIMC-MTS and VIMC-MS criteria, can predict well the LPF loads of the U-notched laminated composite specimens tested under mixed mode I/II loading conditions. One of the important merits of these new criteria is that the predictions of the LPF loads of the U-notched composite specimens are performed without complicated and time-wasting ply-by-ply damage analyses. [ABSTRACT FROM AUTHOR]

We describe two patients with break point cluster region-Abelsen (BCR-ABL)-positive acute leukemia who had an isolated relapse in the central nervous system (CNS) while receiving a next-generation BCR-ABL inhibitor. The first had B-cell acute lymphoblastic leukemia which relapsed in the CNS while maintaining molecular remission in the bone marrow on nilotinib. The second patient had an isolated CNS myeloid blast crisis of chronic myeloid leukemia while maintaining complete cytogenetic remission in the bone marrow on dasatinib. Mutation analysis of the kinase domain revealed 35 base pair insertion (35INT) between exon 8 and 9 in both cases., (Copyright © 2014 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.)