The Experts below are selected from a list of 44811 Experts worldwide ranked by ideXlab platform
Haim Waisman - One of the best experts on this subject based on the ideXlab platform.
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Progressive delamination analysis of composite materials using XFEM and a discrete Damage Zone model
Computational Mechanics, 2015Co-Authors: Yongxiang Wang, Haim WaismanAbstract:The modeling of progressive delamination by means of a discrete Damage Zone model within the extended finite element method is investigated. This framework allows for both bulk and interface Damages to be conveniently traced, regardless of the underlying mesh alignment. For discrete interfaces, a new mixed-mode force–separation relation, which accounts for the coupled interaction between opening and sliding modes, is proposed. The model is based on the concept of Continuum Damage Mechanics and is shown to be thermodynamically consistent. An integral-type nonlocal Damage is adopted in the bulk to regularize the softening material response. The resulting nonlinear equations are solved using a Newton scheme with a dissipation-based arc-length constraint, for which an analytical Jacobian is derived. Several benchmark delamination studies, as well as failure analyses of a fiber/epoxy unit cell, are presented and discussed in detail. The proposed model is validated against available analytical/experimental data and is found to be robust and mesh insensitive.
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A discrete Damage Zone model for mixed-mode delamination of composites under high-cycle fatigue
International Journal of Fracture, 2014Co-Authors: Stephen Jimenez, Xia Liu, Ravindra Duddu, Haim WaismanAbstract:A discrete Damage Zone model is developed to describe the mode-mix ratio and temperature dependent delamination of laminated composite materials under high cycle fatigue loading within the framework of the finite element method. In this approach, discrete nonlinear spring elements are placed at the finite element nodes of the laminate interface, and a combination of static and fatigue Damage growth laws is used to define its constitutive behavior. The model is implemented in the commercial software Abaqus using the user element subroutine. The static Damage model parameters are estimated from fracture mechanics principles, whereas the fatigue Damage model parameters are calibrated by fitting the numerical results to published experimental data. A quadratic relation is proposed to describe the non-monotonic variation of fatigue Damage model parameters with mode-mix ratio. Next, an Arrhenius relation is proposed for the temperature dependence of fatigue Damage, in addition to the incorporation of the temperature dependence of critical fracture energy. The model is convergent upon mesh refinement; however, for accurate prediction the mesh size used for model calibration should be sufficiently small. The model predicted fatigue crack growth rates are in agreement with those obtained from a quadratic relation for the Paris law parameters for variable mode mix conditions, thus verifying the approach. While the model captures the temperature effects on delamination for mode I and 50 % mode II, our prediction deviates from experiments for pure mode II, since the corresponding Damage mechanism entirely changes with temperature.
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discrete Damage Zone model for fracture initiation and propagation
Engineering Fracture Mechanics, 2012Co-Authors: Xia Liu, Ravindra Duddu, Haim WaismanAbstract:Abstract We propose a discrete Damage Zone model (DDZM) aimed at simulating fracture initiation and propagation within the framework of the finite element method. In this approach, rather than employing specific cohesive laws, we employ Damage laws to prescribe both interface spring softening and bulk material stiffness degradation to study crack propagation. For a homogeneous isotropic material the same Damage law is assumed to hold in both the continuum and the interface elements. The irreversibility of Damage naturally accounts for the reduction in material strength and stiffness if the material was previously loaded beyond the elastic limit. The model parameters for interface element are calculated from the principles of linear elastic fracture mechanics. The model is implemented in Abaqus and numerical results for single-mode as well as mixed-mode delamination are presented. The results are in good agreement with those obtained from the virtual crack closure technique (VCCT) and available analytical solutions, thus, illustrating the validity of this approach. Finally, the suitability of the method for studying fracture in fiber–matrix composites involving fiber debonding and matrix cracking is demonstrated.
Jin-hwe Kweon - One of the best experts on this subject based on the ideXlab platform.
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failure load prediction of laminates repaired with a scarf bonded patch using the Damage Zone method
Advanced Composite Materials, 2017Co-Authors: Viethoai Truong, Jinho Choi, Jaeseung Yoo, Choonghyun Kim, Minyoung Park, Jin-hwe KweonAbstract:The Damage Zone method (DZM) is an efficient way to predict the failure of composite structures with a minimum of real testing. Particularly, it is useful when the failure mechanism is too complicated to be accurately analyzed by a merely numerical method. The aim of this study was to use the Damage Zone model to predict the failure load of repaired laminates, in which scarf-bonded joints were used for repair. The model uses a test-based critical Damage Zone and stress-based failure criteria. A total of 45 carbon-epoxy composite (USN) laminate scarf-repaired specimens were first tested with two different defect sizes, four scarf angles, and three overlap layer sizes. The Tsai-Wu and Tsai-Hill criteria were used for the laminate, and the maximum shear stress criterion for the adhesive was adopted to predict failure onset. The predicted failure loads were compared to test results and a good agreement was obtained with a 9.2% maximum deviation for almost all parameters with the exception of a case with an un...
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relationship between the drilling condition and the Damage delamination Zone of glass fiber reinforced plastic composites
Advanced Composite Materials, 2015Co-Authors: Daekeon Ahn, Jinho Choi, Jin-hwe KweonAbstract:Delamination is one of the main defects observed from the drilling of composite materials, and can be an important limiting factor for the use of composite materials. In this study, the delamination area factor for GFRP (Glass Fiber Reinforced Plastic) drilling was proposed to quantify the practical delamination Zone via digital imaging of the Damage Zone around the hole and by calculating the Damage Zone by pixel. From the tests, it was concluded that a higher drill feed rate reduced the delamination Zone and the cutting speeds have no influence on the delamination Zone. Also, the proposed delamination area factor was more suitable and useful for delamination Zone evaluation than the existing delamination factor.
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failure load prediction by Damage Zone method for single lap bonded joints of carbon composite and aluminum
Journal of Composite Materials, 2009Co-Authors: Khanhhung Nguyen, Jin-hwe Kweon, Jinho ChoiAbstract:A Damage Zone method based on 3D finite element analysis was proposed to predict the failure loads of single-lap bonded joints with dissimilar composite-aluminum materials. To simulate delamination failure, interply resin layers between any two adjacent orthotropic laminas of composite adherend were assumed with a thickness of one-tenth of a composite lamina. Geometrically nonlinear effects due to the large rotation of the single-lap joint were included in the analysis. Analysis also considered the material nonlinearity of the aluminum adherend due to the stress exceeding yield level. Based on the experimental observation that the failure modes of the specimens were dominated by delamination and debonding, the Ye-criterion was applied to account for the out-of-plane failure of composite adherend and the Von Mises strain criterion was applied for the adhesive layer. The failure indices were multiplied to the predicted Damage Zone as a weight factor and the calculated Damage Zones were divided by an area or...
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strength prediction of adhesive joints using the modified Damage Zone theory
Composite Structures, 2008Co-Authors: Jinho Choi, Jin-hwe KweonAbstract:The composite joint has become an important research area because the structural efficiency of a structure with a joint is determined by its joints rather than by its basic structure since the joints are often the weakest areas in composite structures. In this paper, the strengths of adhesive joints consisting of metal and composites were predicted and tested by the modified Damage Zone theory. Nonlinear finite element analyses of adhesive joints considering the material nonlinearity of the adhesive layer were performed. From the tests and analyses, the strengths of the adhesive joints could be predicted to within 20.1% using the modified Damage Zone theory.
James Evans - One of the best experts on this subject based on the ideXlab platform.
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linking hematite u th he dating with the microtextural record of seismicity in the wasatch fault Damage Zone utah usa
Geology, 2015Co-Authors: Alexis K Ault, James Evans, Peter W Reiners, Stuart N ThomsonAbstract:Techniques directly dating fault slip are few, limiting the ability to interpret the rock record of seismicity. Hematite is commonly found in fault Zones, amenable to (U-Th)/He dating, and slip surface hematite may be reset by shear heating events and/or recrystallization. Glossy hematite-coated fault surfaces in the Wasatch fault footwall Damage Zone, Utah (USA), exhibit evidence of hematite cataclasis and preserve Pliocene hematite (U-Th)/He dates. Apatite (U-Th)/He and fission track data from the host gneiss indicate footwall unroofing through ∼2 km by ca. 4.5 Ma. Internally reproducible but disparate hematite (U-Th)/He dates 4.5 Ma and younger from isolated locations on a single fault surface do not reflect ambient cooling. We hypothesize that these dates, and associated iridescence and annealed crystal texture, document rapid cooling from friction-generated heat during small seismic slip events between ca. 4.5 and 2.5 Ma. Thus, hematite (U-Th)/He dating offers the potential to decipher thermal anomalies in the rock record associated with slip on 10 5 –10 6 yr time scales.
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identification of reactivation and increased permeability associated with a fault Damage Zone using a multidisciplinary approach
Journal of Structural Geology, 2014Co-Authors: Elizabeth S Petrie, R A Petrie, James EvansAbstract:Abstract We evaluate the fault Damage Zone associated with a reactivated long-strike length, small-offset normal fault in the Permian Cedar Mesa Sandstone, southeastern Utah. This fault is characterized by a single slip surface and a 9-m wide Damage Zone containing deformation bands and veins. Field observations include cross-cutting relationships, permeability increase, rock strength decrease, and ultraviolet-light-induced mineral fluorescence within the Damage Zone. These field observations, combined with the interpreted structural diagenetic sequence from petrographic analysis, suggest a deformation history of reactivation and several generations of mineralization. All deformation bands and calcite veins fluoresce under ultraviolet light, indicating fluid pathway connectivity and a shared mineralization history. Pre-existing structures act as loci for younger deformation and mineralization events, so this fault and its Damage Zone illustrate the importance of the fault Damage Zone to subsurface fluid flow. We model a simplified stress history to understand the importance rock properties and variations in differential and effective mean stress have on the structures within the Damage Zone. The moderate confining pressures, possible variations in pore pressure, and porous, fine-grained nature of the Cedar Mesa Sandstone produces a fault Damage Zone characterized by enhanced permeability and mineralization.
Stuart N Thomson - One of the best experts on this subject based on the ideXlab platform.
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linking hematite u th he dating with the microtextural record of seismicity in the wasatch fault Damage Zone utah usa
Geology, 2015Co-Authors: Alexis K Ault, James Evans, Peter W Reiners, Stuart N ThomsonAbstract:Techniques directly dating fault slip are few, limiting the ability to interpret the rock record of seismicity. Hematite is commonly found in fault Zones, amenable to (U-Th)/He dating, and slip surface hematite may be reset by shear heating events and/or recrystallization. Glossy hematite-coated fault surfaces in the Wasatch fault footwall Damage Zone, Utah (USA), exhibit evidence of hematite cataclasis and preserve Pliocene hematite (U-Th)/He dates. Apatite (U-Th)/He and fission track data from the host gneiss indicate footwall unroofing through ∼2 km by ca. 4.5 Ma. Internally reproducible but disparate hematite (U-Th)/He dates 4.5 Ma and younger from isolated locations on a single fault surface do not reflect ambient cooling. We hypothesize that these dates, and associated iridescence and annealed crystal texture, document rapid cooling from friction-generated heat during small seismic slip events between ca. 4.5 and 2.5 Ma. Thus, hematite (U-Th)/He dating offers the potential to decipher thermal anomalies in the rock record associated with slip on 10 5 –10 6 yr time scales.
Ming Chen - One of the best experts on this subject based on the ideXlab platform.
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comparison of blast induced Damage between presplit and smooth blasting of high rock slope
Rock Mechanics and Rock Engineering, 2014Co-Authors: Ming Chen, Peng Yan, Jianhua YangAbstract:This paper focuses on the comparison of Damage induced by smooth blasting and presplit blasting based on the excavation of high rock slope. The whole Damage process of the smooth blasting and presplit blasting excavation method is studied by using a cumulative blasting Damage numerical simulation technology based on the secondary development of the dynamic finite element code LS-DYNA. The results demonstrate that, in the case of contour blasting with the method of smooth blasting, the total Damage of rock slope is a result of cumulated Damage induced by the production hole, buffering hole, and smooth hole. Among the total Damage, the blasting of the production hole is the main resource, followed by the smooth and buffering holes. For the presplit blasting, the final Damage of rock slope is mainly induced by presplit blasting itself. The spatial distribution characteristics of the final Damage Zone of two methods are compared. Two classes of Damage Zone could be found in smooth blasting excavation; one of them is the columnar high-degree Damage Zone around the slope surface and the other is the low-degree Damage Zone located in the middle of the slope. But in the case of presplit blasting, there is only the columnar high-degree Damage Zone around the slope surface. Finally, a Damage control suggestion for two blasting excavation methods is proposed and verified based on the excavation of the temporary shiplock slopes of the Three Gorges Project in China.
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Contributions of In-Situ Stress Transient Redistribution to Blasting Excavation Damage Zone of Deep Tunnels
Rock Mechanics and Rock Engineering, 2014Co-Authors: Wenbo Lu, Chuangbing Zhou, Yingguo Hu, Ming Chen, Xin-xia WuAbstract:With the background of construction of the headrace tunnels with the deepest buried depth in China at present, by means of carefully acoustic velocity detection and analysis of Excavation Damage Zone (EDZ), the contributions to Damage Zones made by the effect of in situ stress transient redistribution are studied and compared with the extent of Damage caused by the explosive load. Also, the numerical simulation was adopted to verify detecting the results. It turned out that the in situ stress transient redistribution during blasting has great influence on the development of EDZ of deep tunnels. The blasting excavation-induced Damage Zone of deep tunnels can be divided into the inner Damage Zone and the outer Damage Zone from the excavation surface into surrounding rocks. Although this Damage Zone dividing method is similar to the work of Martino and Chandler (2004), the consideration of developing a mechanism of the inner Damage Zone, especially the contribution of in situ stress transient redistribution, is totally different. The inner Damage Zone, which accounts for 29–57 % of the total Damage Zone, is mainly caused by explosive load and in situ stress transient adjustment, while the outer Damage Zone can be mostly attributed to the static redistribution of in situ stress. Field tests and numerical simulation indicate that the in situ stress transient redistribution effect during blasting contributes about 16–51 % to the inner Damage Zone in the 2# headrace tunnel of Jinping II Hydropower Station. For general cases, it can be concluded that the in situ stress transient redistribution is one of the main contributors of an excavation Damage Zone, and Damage caused by in situ stress transient redistribution effect may exceed the Damage caused by explosion load and become the main inducing factor for Damage with the rise of in situ stress levels.
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spatial distribution of excavation induced Damage Zone of high rock slope
International Journal of Rock Mechanics and Mining Sciences, 2013Co-Authors: Jianhua Yang, Ming Chen, Peng YanAbstract:Abstract The excavation induced Damage Zone (EDZ) can significantly influence the overall performance of an excavated slope. Determining the spatial distribution characteristics of the EDZ is very important to both design and construction of high rock slope. Based on the case study of the excavation of high rock slope at the Xiluodu Hydropower Station in Sichuan province of China, spatial distributions of EDZ of the slope surface and berm were determined using sonic logging and cross-hole sonic tests. The results showed that the vertical Damage depth increases non-linearly from the inner side to the outer flank of the berm, whereas the horizontal Damage scope increases non-linearly from the bottom to the top of the slope. The maximum horizontal Damage scope and the maximum vertical Damage depth are found to be at the outer flank of the berm. To reproduce and predict the EDZ for high rock slope excavation with Dynamic Finite Element Method, a modified tensile–compressive Damage model was introduced into the simulation of the EDZ of Xiluodu high rock slope. Four other frequently used Damage models were used as comparisons. The results demonstrate that the Damage Zone obtained by the modified tensile–compressive Damage model agreed with observations better than the other four existing blasting Damage models.
