The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
Yoshiaki Akiniwa - One of the best experts on this subject based on the ideXlab platform.
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Experimental and computational analyses on fatigue fracture and microstructure in dissimilar metal weldments with circular sharp Stress Raiser
International Journal of Fatigue, 2020Co-Authors: Takumi Sasaki, Yoshiaki AkiniwaAbstract:Abstract Fatigue strengths of dissimilar metal weldments with a circular sharp Stress Raiser, which were the inner peripheral side welded joints of flange pipes with tungsten inert gas (TIG) or metal inert gas (MIG) welding process, were defined through bending fatigue experiments. Fatigue strengths decreased according to Stress concentration factors in some cases but not in samples with a different welding process, and Stress intensity factors at the sharp weld notch were applied for analyses using the energy release rate method. The crack states corresponded to the fact that the fatigue cracks propagated at nearly right angles to the maximum Stress direction, and it is possible to predict their propagation direction. The local fatigue resistance of the martensite-ferrite structure with the TIG welding was higher than that of the austenite-ferrite structure with the MIG welding which has a largely different penetration rate. In the samples which have similar weld metal microstructure, the nominal fatigue strength declines according to the increase in the Stress concentration factor. The TIG samples and the MIG samples reach their fatigue failure in the same level of Stress intensity factors, except for a MIG sample which has a large excess metal shape and a different fracture mode. The Stress intensity factors can be used as the fatigue fracture threshold criterion in the weldments with a circular sharp Stress Raiser, where have the complex Stress effects.
Ever J. Barbero - One of the best experts on this subject based on the ideXlab platform.
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Analysis of damage localization in composite laminates using a discrete damage model
Composites Part B: Engineering, 2014Co-Authors: M.m. Moure, Sonia Sanchez-saez, Ever J. BarberoAbstract:Abstract Damage localization around Stress Raisers and material defects in laminated composites is studied using a discrete damage mechanics model augmented by a fiber damage model. The proposed formulation captures the damaging behavior of plates with initial defects and Stress Raisers such as holes, including damage initiation, evolution, and ultimate fracture of the specimen. It also helps explain the reduction of Stress concentration factor when matrix and fiber damage develop. The state variables are the crack density and the fiber failure damage. The formulation is implemented as a material model in Abaqus applicable to laminated composite plates and shells. Material defects are simulated by inserting an initial crack density in a small region of the specimen. Stress Raisers are simulated by an open hole. The predictions are shown to be insensitive to mesh density. Further, damage localizes near Stress Raiser and material defects, thus numerically demonstrating the objectivity of the proposed model. Qualitative and quantitative comparisons with experimental data are presented.
Wilfried Becker - One of the best experts on this subject based on the ideXlab platform.
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analysis of the effect of a Stress Raiser on the strength of a ud flax epoxy composite in off axis tension
Journal of Composite Materials, 2015Co-Authors: J Modniks, E. Spārniņš, Janis Andersons, Wilfried BeckerAbstract:The effect of Stress Raisers in the form of a slit-like notch and an open circular hole on the tensile strength of a quasi-UD flax-fiber-reinforced composite is studied experimentally. A finite fra...
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Analysis of the effect of a Stress Raiser on the strength of a UD flax/epoxy composite in off-axis tension
Journal of Composite Materials, 2014Co-Authors: J Modniks, E. Spārniņš, Janis Andersons, Wilfried BeckerAbstract:The effect of Stress Raisers in the form of a slit-like notch and an open circular hole on the tensile strength of a quasi-UD flax-fiber-reinforced composite is studied experimentally. A finite fra...
Vikram Deshpande - One of the best experts on this subject based on the ideXlab platform.
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notch sensitivity of orthotropic solids interaction of tensile and shear damage zones
International Journal of Fracture, 2018Co-Authors: Harika C. Tankasala, Vikram Deshpande, Norman A. FleckAbstract:© 2018, The Author(s). The macroscopic tensile strength of a panel containing a centre-crack or a centre-hole is predicted, assuming the simultaneous activation of multiple cohesive zones. The panel is made from an orthotropic elastic solid, and the Stress Raiser has both a tensile cohesive zone ahead of its tip, and shear cohesive zones in an orthogonal direction in order to represent two simultaneous damage mechanisms. These cohesive zones allow for two modes of fracture: (i) crack extension by penetration, and (ii) splitting in an orthogonal direction. The sensitivity of macroscopic tensile strength and failure mode to the degree of orthotropy is explored. The role of notch acuity and notch size are assessed by comparing the response of the pre-crack to that of the circular hole. This study reveals the role of the relative strength and relative toughness of competing damage modes in dictating the macroscopic strength of a notched panel made from an orthotropic elastic solid. Universal failure mechanism maps are constructed for the pre-crack and hole for a wide range of material orthotropies. The maps are useful for predicting whether failure is by penetration or kinking. Case studies are developed to compare the predictions with observations taken from the literature for selected orthotropic solids. It is found that synergistic strengthening occurs: when failure is by crack penetration ahead of the Stress Raiser, the presence of shear plastic zones leads to an enhancement of macroscopic strength. In contrast, when failure is by crack kinking, the presence of a tensile plastic zone ahead of the Stress Raiser has only a mild effect upon the macroscopic strength.
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the effect of laminate lay up on the multi axial notched strength of cfrp panels simulation versus experiment
European Journal of Mechanics A-solids, 2017Co-Authors: Vikram Deshpande, N A FleckAbstract:Abstract The effect of laminate lay-up upon the evolution of damage and upon the multi-axial failure locus of notched carbon fibre reinforced polymer (CFRP) panels is investigated experimentally and numerically. The proportion of 0° plies and ±45° plies is varied, and combined tensile and shear loading (and direct compression) is generated by a modified Arcan test rig. The failure surface is measured for panels containing a central hole or sharp notch, and the evolution of sub-critical damage is observed by X-ray CT and sectioning of the specimens. Three distinct damage modes are evident, depending upon the applied Stress state, lay-up and geometry of the Stress-Raiser. The open-hole and open-notch values of tensile and compressive strength increase with the proportion of 0° plies, whereas the shear strengths do not scale with the proportion of ±45° plies. Inter-fibre splitting of the main loading bearing plies reduces the Stress concentration, but the degree of splitting varies with loading direction and lay-up. The Finite Element (FE) method is used to predict not only damage development within each ply but also inter-ply delamination by the use of cohesive interfaces using a traction-separation law. The predicted failure envelopes and damage evolution are in good agreement with the observations, provided the mesh aligns with the fibre direction. This supports the adopted ply-by-ply FE strategy as a useful predictive tool for composite failure.
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failure mechanisms of a notched cfrp laminate under multi axial loading
Composites Part A-applied Science and Manufacturing, 2015Co-Authors: Jly Tan, Vikram Deshpande, N A FleckAbstract:Abstract A quasi-isotropic CFRP laminate, containing a notch or circular hole, is subjected to combined tension and shear, or compression. The measured failure strengths of the specimens are used to construct failure envelopes in Stress space. Three competing failure mechanisms are observed, and for each mechanism splitting within the critical ply reduces the Stress concentration from the hole or notch: (i) a tension-dominated mode, with laminate failure dictated by tensile failure of the 0° plies, (ii) a shear-dominated mode entailing microbuckling of the −45° plies, and (iii) microbuckling of the 0° plies under remote compression. The net section strength (for all Stress states investigated) is greater for specimens with a notch than a circular hole, and this is associated with greater split development in the load-bearing plies. The paper contributes to the literature by reporting sub-critical damage modes and failure envelopes under multi-axial loading for two types of Stress Raiser.
Norman A. Fleck - One of the best experts on this subject based on the ideXlab platform.
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Notch sensitivity of orthotropic solids: interaction of tensile and shear damage zones
International Journal of Fracture, 2018Co-Authors: Harika C. Tankasala, Vikram S. Deshpande, Norman A. FleckAbstract:The macroscopic tensile strength of a panel containing a centre-crack or a centre-hole is predicted, assuming the simultaneous activation of multiple cohesive zones. The panel is made from an orthotropic elastic solid, and the Stress Raiser has both a tensile cohesive zone ahead of its tip, and shear cohesive zones in an orthogonal direction in order to represent two simultaneous damage mechanisms. These cohesive zones allow for two modes of fracture: (i) crack extension by penetration, and (ii) splitting in an orthogonal direction. The sensitivity of macroscopic tensile strength and failure mode to the degree of orthotropy is explored. The role of notch acuity and notch size are assessed by comparing the response of the pre-crack to that of the circular hole. This study reveals the role of the relative strength and relative toughness of competing damage modes in dictating the macroscopic strength of a notched panel made from an orthotropic elastic solid. Universal failure mechanism maps are constructed for the pre-crack and hole for a wide range of material orthotropies. The maps are useful for predicting whether failure is by penetration or kinking. Case studies are developed to compare the predictions with observations taken from the literature for selected orthotropic solids. It is found that synergistic strengthening occurs: when failure is by crack penetration ahead of the Stress Raiser, the presence of shear plastic zones leads to an enhancement of macroscopic strength. In contrast, when failure is by crack kinking, the presence of a tensile plastic zone ahead of the Stress Raiser has only a mild effect upon the macroscopic strength.
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notch sensitivity of orthotropic solids interaction of tensile and shear damage zones
International Journal of Fracture, 2018Co-Authors: Harika C. Tankasala, Vikram Deshpande, Norman A. FleckAbstract:© 2018, The Author(s). The macroscopic tensile strength of a panel containing a centre-crack or a centre-hole is predicted, assuming the simultaneous activation of multiple cohesive zones. The panel is made from an orthotropic elastic solid, and the Stress Raiser has both a tensile cohesive zone ahead of its tip, and shear cohesive zones in an orthogonal direction in order to represent two simultaneous damage mechanisms. These cohesive zones allow for two modes of fracture: (i) crack extension by penetration, and (ii) splitting in an orthogonal direction. The sensitivity of macroscopic tensile strength and failure mode to the degree of orthotropy is explored. The role of notch acuity and notch size are assessed by comparing the response of the pre-crack to that of the circular hole. This study reveals the role of the relative strength and relative toughness of competing damage modes in dictating the macroscopic strength of a notched panel made from an orthotropic elastic solid. Universal failure mechanism maps are constructed for the pre-crack and hole for a wide range of material orthotropies. The maps are useful for predicting whether failure is by penetration or kinking. Case studies are developed to compare the predictions with observations taken from the literature for selected orthotropic solids. It is found that synergistic strengthening occurs: when failure is by crack penetration ahead of the Stress Raiser, the presence of shear plastic zones leads to an enhancement of macroscopic strength. In contrast, when failure is by crack kinking, the presence of a tensile plastic zone ahead of the Stress Raiser has only a mild effect upon the macroscopic strength.
