The Experts below are selected from a list of 14961 Experts worldwide ranked by ideXlab platform
Wenbin Wang - One of the best experts on this subject based on the ideXlab platform.
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a preventive maintenance model with a two level inspection policy based on a three stage Failure Process
Reliability Engineering & System Safety, 2014Co-Authors: Wenbin Wang, Fei Zhao, Rui PengAbstract:Abstract Inspection is always an important preventive maintenance (PM) activity and can have different depths and cover all or part of plant systems. This paper introduces a two-level inspection policy model for a single component plant system based on a three-stage Failure Process. Such a Failure Process divides the system′s life into three stages: good, minor defective and severe defective stages. The first level of inspection, the minor inspection, can only identify the minor defective stage with a certain probability, but can always reveal the severe defective stage. The major inspection can however identify both defective stages perfectly. Once the system is found to be in the minor defective stage, a shortened inspection interval is adopted. If however the system is found to be in the severe defective stage, we may delay the maintenance action if the time to the next planned PM window is less than a threshold level, but otherwise, replace immediately. This corresponds to the well adopted maintenance policy in practice such as periodic inspections with planned PMs. A numerical example is presented to demonstrate the proposed model by comparing with other models.
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An inspection and replacement model based on a three-stage Failure Process
Proceedings of the IEEE 2012 Prognostics and System Health Management Conference (PHM-2012 Beijing), 2012Co-Authors: Fei Zhao, Rui Peng, Wenbin WangAbstract:This paper proposes an inspection and replacement model based on a three-stage Failure Process for a single-unit system to minimize the expected cost per unit time. The models using the two-stage Failure Process for optimizing the inspection interval of the system have been addressed by many others. However, a three-stage Failure Process provides more modeling options and is closer to reality since a binary description of the system's state is restrictive. It is assumed that the system needs to be repaired immediately in case in a severe defective stage being identified at an inspection or at a Failure, and replaced once it reaches a certain age, however, two different kinds of maintenance decisions are made if the system is identified to be in a minor defective stage at an inspection. Both repair and replacement renew the system. Various cost models are studied under different maintenance policies and a numerical example is presented to illustrate the applicability of the model.
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an inspection model based on a three stage Failure Process
Reliability Engineering & System Safety, 2011Co-Authors: Wenbin WangAbstract:Inspection or condition monitoring is increasingly used in industry to identify the plant item's state and to make maintenance decisions. This paper discusses an inspection model that is established under an assumption that the plant item's state can be classified into four states corresponding to a three-stage Failure Process. The failed state is always observed immediately, but the other three states, namely normal, minor defective and severe defective, can only be identified by an inspection. The durations of the normal, minor defective and severe defective states constitute a three-stage Failure Process. This assumption is actually motivated by real world observations where the plant state is often classified by a three colour scheme, e.g., green, yellow and red corresponding to the three states before Failure. The three-stage Failure concept proposed is an extension to the delay time concept where the plant Failure Process is divided into a two-stage Process. However such extension provides more modelling options than the two-stage model and is a step closer to reality since a binary description of the plat item's state is restrictive. By formulating the probabilities of defective state identification and Failure, we are able to establish a model to optimise the inspection interval with respect to a criterion function of interest. A real world example is presented to show the applicability of the model.
Wenli Lin - One of the best experts on this subject based on the ideXlab platform.
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An acoustic emission characterization of the Failure Process of shallow foundation resting on sandy soils.
Ultrasonics, 2018Co-Authors: Wuwei Mao, Yang Yang, Wenli LinAbstract:Shallow foundation is a common foundation type that is usually used for small to medium size structures. The bearing ability and the Failure mechanism of shallow foundation are the fundamental concerns for geotechnical engineers, and the demand for new insights into the relevant issue is still increasing. This paper presents an acoustic emission (AE) characterization of the Failure Process of shallow foundation, with the aim of revealing the fundamental information on AE signals associated with shallow foundation loading as well as its connection with the ground bearing behavior. Experiments were carried out to model the Failure Process of shallow foundation resting on sandy ground with different densities (i.e. loose and dense) and subjected to different loading conditions (i.e. monotonic and cyclic loading). Comparisons between AE activities and ground bearing behavior are presented. The feasibility of using AE for stability monitoring of shallow foundation is revealed and discussed.
V. N. Shlyannikov - One of the best experts on this subject based on the ideXlab platform.
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Strain-energy density and Failure-Process zone report 2. Experimental confirmation
Strength of Materials, 1995Co-Authors: V. N. ShlyannikovAbstract:Experimental confirmation is presented for a previously obtained, theoretical relationship between the size of the Failure-Process zone and the total strain-energy density (SED) in dimensionless form for conditions of mixed Failure modes under static and cyclic deformation. Characteristic features of subcritical crack growth are delineated for static deformation as a function of type of steel structure. Familiar literature data on the ductile-brittle transition are described, and an equation proposed for calculation of fracture toughness on the basis of standard mechanical properties of materials. Both constraint and scale effects are analyzed for Failure under plane stress and plane strain within the framework of the theory under development. Characteristics of cyclic crack growth are compared with fractography data on the fatigue-stria step. It is demonstrated that the results of static and fatigue experiments for steel in different structural compositions lie on one curve common for a given specimen geometry .
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Strain-energy density and Failure-Process zone report 2. Experimental confirmation
Strength of Materials, 1995Co-Authors: V. N. ShlyannikovAbstract:Experimental confirmation is presented for a previously obtained, theoretical relationship between the size of the Failure-Process zone and the total strain-energy density (SED) in dimensionless form for conditions of mixed Failure modes under static and cyclic deformation. Characteristic features of subcritical crack growth are delineated for static deformation as a function of type of steel structure. Familiar literature data on the ductile-brittle transition are described, and an equation proposed for calculation of fracture toughness on the basis of standard mechanical properties of materials. Both constraint and scale effects are analyzed for Failure under plane stress and plane strain within the framework of the theory under development. Characteristics of cyclic crack growth are compared with fractography data on the fatigue-stria step. It is demonstrated that the results of static and fatigue experiments for steel in different structural compositions lie on one curve common for a given specimen geometry .
Wuwei Mao - One of the best experts on this subject based on the ideXlab platform.
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An acoustic emission characterization of the Failure Process of shallow foundation resting on sandy soils.
Ultrasonics, 2018Co-Authors: Wuwei Mao, Yang Yang, Wenli LinAbstract:Shallow foundation is a common foundation type that is usually used for small to medium size structures. The bearing ability and the Failure mechanism of shallow foundation are the fundamental concerns for geotechnical engineers, and the demand for new insights into the relevant issue is still increasing. This paper presents an acoustic emission (AE) characterization of the Failure Process of shallow foundation, with the aim of revealing the fundamental information on AE signals associated with shallow foundation loading as well as its connection with the ground bearing behavior. Experiments were carried out to model the Failure Process of shallow foundation resting on sandy ground with different densities (i.e. loose and dense) and subjected to different loading conditions (i.e. monotonic and cyclic loading). Comparisons between AE activities and ground bearing behavior are presented. The feasibility of using AE for stability monitoring of shallow foundation is revealed and discussed.
Chun An Tang - One of the best experts on this subject based on the ideXlab platform.
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a statistical meso damage mechanical method for modeling trans scale progressive Failure Process of rock
International Journal of Rock Mechanics and Mining Sciences, 2015Co-Authors: Chun An TangAbstract:Abstract Starting from the concept of Representative Volume Element (RVE) at the mesoscopic scale, a statistical meso-damage mechanical method (SMDMM) is developed to model the trans-scale progressive Failure Process of rock, based on the statistical and continuum damage mechanics theory and the finite element method (FEM). The proposed mesoscopic constitutive law of RVE is established within the framework of elastic–brittle-damage theory in which the double damage functions correspond to a tensile and compressive damage surface. A statistical approach is employed to describe the mesoscopic heterogeneity of rock material. The damage evolution and accumulation of mesoscopic RVEs is used to reflect the macroscopic Failure characteristics of rock. The global stress and strain fields are solved by the FEM. An element represents a RVE, the initiation and propagation of meso-macroscopic trans-scale cracks and their interaction are manifested by removing the failed elements. Numerical analyses are carried out on a few groups of laboratory-scale rock specimens and the effects of RVE size, material homogeneity and quasi-static loading step length are investigated. Finally, a full-scale Atomic Energy of Canada Limited (AECL) Mine-by test tunnel is simulated. The proposed SMDMM is calibrated and validated for its trans-scale modeling capability to reproduce the shape and size of excavation damage zone profile around the tunnel. Accordingly, the simulation results are compared with experimental observations and numerical results predicted by other models. It is shown that the SMDMM has good performance for modeling the rock Failure Process from meso- to engineering/field-scale.
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Impact of rock microstructures on Failure Processes - Numerical study based on DIP technique
Geomechanics and Engineering, 2014Co-Authors: Wancheng Zhu, Chun An Tang, Tianhong YangAbstract:It is generally accepted that material heterogeneity has a great influence on the deformation, strength, damage and Failure modes of rock. This paper presents numerical simulation on rock Failure Process based on the characterization of rock heterogeneity by using a digital image Processing (DIP) technique. The actual heterogeneity of rock at mesoscopic scale (characterized as minerals) is retrieved by using a vectorization transformation method based on the digital image of rock surface, and it is imported into a well-established numerical code Rock Failure Process Analysis (RFPA), in order to examine the effect of rock heterogeneity on the rock Failure Process. In this regard, the numerical model of rock could be built based on the actual characterization of the heterogeneity of rock at the meso-scale. Then, the images of granite are taken as an example to illustrate the implementation of DIP technique in simulating the rock Failure Process. Three numerical examples are presented to demonstrate the impact of actual rock heterogeneity due to spatial distribution of constituent mineral grains (e.g., feldspar, quartz and mica) on the macro-scale mechanical response, and the associated rock Failure mechanism at the meso-scale level is clarified. The numerical results indicate that the shape and distribution of constituent mineral grains have a pronounced impact on stress distribution and concentration, which may further control the Failure Process of granite. The proposed method provides an efficient tool for studying the mechanical behaviors of heterogeneous rock and rock-like materials whose Failure Processes are strongly influenced by material heterogeneity.
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Numerical Simulation of 3-D Failure Process of Reinforced Concrete Specimen under Uniaxial Tension
Key Engineering Materials, 2007Co-Authors: Juan Xia Zhang, Chun An Tang, Xiu Yan Zhou, Xing Jie Hui, Zheng Zhao Liang, Shu Hong Wang, Xian Zhang GuoAbstract:The periodically distributed fracture spacing phenomenon exists in the Failure Process of the reinforced concrete prism under uniaxial tension. In this paper, A numerical code RFPA3D (3D Realistic Failure Process Analysis) is used to simulate the three-dimensional Failure Process of plain concrete prism specimen and reinforced concrete prism specimen under uniaxial tension. The reinforced concrete is represented by a set of elements with same size and different mechanical properties. They are uniform cubic elements and their mechanical properties, including elastic modulus and peak strength, are distributed through the specimens according to a certain statistical distribution. The elastic modulus and other mechanical properties are weakened gradually when the stresses in the elements meet the specific Failure criterion. The displacement-controlled loading scheme is used to simulate the complete Failure Process of reinforced concrete. The analyses focus on the Failure mechanisms of the concrete and reinforcement. The complete Process of the fracture for the plain concrete prism and the fracture initiation, infilling and saturation of the reinforced concrete prism is reproduced. It agrees well with the theoretical analysis. Through 3D numerical tests for the specimen, it can be investigated the interaction between the reinforcement and concrete mechanical properties in meso-level and the numerical code is proved to be an effective way to help thoroughly understand the rule of the reinforcement and concrete and also help the design of the structural concrete components and systems.
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Digital Image Based Simulation on Failure Process of Heterogeneous Brittle Materials
Key Engineering Materials, 2006Co-Authors: Wancheng Zhu, Jin Chao Duan, Chun An Tang, Shanyong WangAbstract:Rock and concrete are typical heterogeneous material that the meso-scale heterogeneity may have a significant effect on their macro-scale mechanical responses. In this work, a digital image-based (DIB) technique is employed to characterize and quantify the heterogeneity of concrete, and the obtained data is directly imported into a numerical code named RFPA (Rock Failure Process Analysis) to study the effect of heterogeneity on the Failure Process of concrete. The upgraded RFPA is capable to simulate the progressive Failure of brittle materials such as rock and concrete, representing both the growth of existing fractures and the formation of new fractures, obviating the need to identify crack tips and their interaction explicitly. The simulated results are in reasonable agreement with experimental measurements and phenomenological observations reported in previous studies.
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Three-Dimensional Material Failure Process Analysis
Key Engineering Materials, 2005Co-Authors: Chun An Tang, Zheng Zhao Liang, Yong Bin ZhangAbstract:This paper introduces a newly developed three-dimensional Material Failure Process Analysis code, MFPA3D to model the Failure Processes of brittle materials, such as concrete, ceramics, fibrous materials, and rocks. This numerical code, based on a stress analysis method (finite element method) and a material Failure constitutive law, can be taken as a tool in numerical modeling analysis to enhance our understanding of the Failure mechanisms of brittle materials. Properties of material heterogeneity are taken into account. The material is discretized into numerous small elements with fixed size. Fracture behavior can be modeled by reducing the material stiffness and strength after the peak strength of the material has been reached. The evolution of the cracking Process down to full fracture implies strain softening, which describes the post-peak gradual decline of stress at increasing strain. In the present study, a Mohr-Coulomb criterion envelop with a tension cut-off is used so that the element may fail either in shear or in tension. Simulated fracture or crack patterns of two examples are found quite realistic, and the results strongly depend on the heterogeneity level.
