Advances in Fracture and Materials Behavior

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Authors: Wei Gao
Abstract: Because it is very important to study the coal pillar stability, a lot of methods to do this have been proposed. But most of those methods do not consider the nature of coal material and only study the coal pillar that is level. To solve this problem suitably, here a new method is proposed. In this method, the plastic softening nature of coal material is considered. And also, the coal seam pitch is considered in our analysis. Based on real deformation of coal pillar and the previous study, the limiting equilibrium method is applied. At last, the rationality of our method is verified through a strip mining engineering example. And the results show that, the computing results of our method are coincided with measuring results very well and our method can be applied in real engineering practice very well.
Authors: Zheng Hua Xiao, Bo Han, Akenjiang Tuohuti, Hong Jian Liao
Abstract: This paper is mainly concerned with the saturated-unsaturated seepage analysis of earth dams based on unsaturated soil theory and the stability analysis of earth dams based on conception of slices. At first, beginning basic seepage theory, thesis introduce the saturated-unsaturated and steady-unsteady seepage differential equation of porous media and the FEM regarding hydraulic pressure head as basic unknown quantity. Then considering the shear strength of unsaturated soil, the method of analysis of general limit equilibrium has been approved and it can be used in the analysis of the stability of saturated-unsaturated slopes. Through an example it is respectively discussed effects of seepage flow when water head is changed in earth dam and the effects of percolation in the stability of the earth dam slope. Some helpful conclusions are gained. This can be making the best of the tow methods and the results can be used in engineering for reference.
Authors: Cheng Yuan Zhang, Xiao Yan Liu, Quan Sheng Liu
Abstract: Coupled THM simulator on FEBEX case is a highly nonlinear system including several nonlinear sub-models. To better understand the coupled THM processes and their influence on the prediction of disposal system behavior, this paper presents an uncertainty study and model optimization on coupled THM simulation under DECOVALEX-THMC framework. It focus on the effect of complexity on model uncertainty which is based on the hypothesis stating that as a model becomes more complex in terms of increased number of processes involved and parameters, the error between simulations and measurements decreases and the overall model sensitivity increases. An uncertainty function is defined which minimizes both error and sensitivity. The result of comparative study basing on different complexity level models of FEBEX case study verifies this hypothesis and indicates that method presented can address uncertainty of numerical model and give us a criterion to choose most suitable model in a relative manner.
Authors: Hui Liu, Wei Lian Qu, Jin Wen Wang
Abstract: Taken the roof of Shenzhen citizen center with huge size and very complicated structure as the engineering background, the intelligent methods of safety monitoring of integer behavior for large span complex space truss structures under wind-excited by the data-acquisition based on limited sensors are discussed in detail in this paper. In order to acquire the working status of the whole structure, the method that can be adopted to obtain structural real-time response under wind load is listed as follows, step1: to identify the wind load; step 2: to update the structural finite element model; step 3: to measure peak factor of structural response; step 4: to directly analyze the structural real timely response. The first two steps are key techniques among all the steps of the method. The weighted proper orthogonal decomposition technique is adopted to identify the characteristics of wind pressures at all internal nodes on the truss structural roof in the frequency domain by using the measured wind pressure data from non-uniformly taps. Moreover, by using measured structural acceleration response from finite acceleration sensors on the structure, the accurate analytical model of the structure is established by updating the finite element model based on modifying node parameters. Then, the monitoring result of entire truss structure in the worst working performance in every ten minutes is obtained according to positive deductive method with the measured mean wind speed and wind direction from anemometer and peak factor acquired from finite strain gauges on the truss structure in every 10 minutes. Finally, based on the above-mentioned method, working status intelligent monitoring system is established, which can display the stress level and safe class of all structural members.
Authors: Q.W. Zhang, Di Tao Niu, T. Zhang, B.Y. Zhang
Abstract: A simplified integrating model is developed for soil-pile dynamic interaction system under seismic loading. Different from previous work, this simplified model constructs the whole system stiffness matrix by combining the stiffness matrix of pile and near region soil system according to the volumetric ratio of pile group and soil system. This simplified model can avoid deviation brought by previous soil-pile surface model and can felicitously simulate the co-working mechanism between soil and piles. The feasibility of the proposed approach is assessed by comparing with in-site observation result of real project.
Authors: Yan Ling Han, Shou Qi Cao
Abstract: Diagnosis decision-making and evaluation analysis is two closely-related contents in the process of intelligent fault diagnosis, correct decision-making could be made only based on objective and fair evaluation. This paper brought up decision-making objective and corresponding decision-making model for intelligent fault diagnosis, and gave its evaluation indicator architecture. Combining grey correlative analysis with hierarchical analysis method, multi-hierarchy grey correlative analysis was brought forward to apply into intelligent fault diagnosis, its principle, algorithm and evaluation execution process were researched deeply, and finally the analysis sample was given.
Authors: Xin Pu Shen, Guo Xiao Shen, Ji Hang Liu
Abstract: Instability of completed sand reservoirs reduces oil production rate and degrades production equipments. A major cause of such instability is plastic deformation of perforation tunnel, resulting in sand production. Influence of direction of maximum principal stress on perforation tunnel has not been investigated either experimentally or theoretically. Elastoplastic consolidation analysis is the foundation of sand production prediction of an oilwell. Three dimensional elastoplastic consolidation analyses were made numerically for the deformation of perforation tunnel of an oilwell coupled with oil flow within sand reservoir with ABAQUS-6.5 finite element software. The drilling processes of borehole and perforation tunnel were simulated in combination of rock deformation process which was regarded as a coupled multiphase problem. Mohr-Coulomb yielding criterion was adopted in the calculation. The designs with 4-perforation density and with 8-perforation density were numerically analyzed and compared. Influence of the direction of principal horizontal effective geostress on the instability of perforation tunnel and that of perforation density were investigated. Numerical results indicate that 1) there is rather large plastic zone occurs when the axis of perforation tunnel is alone the direction of the maximum principal horizontal direction. If the axis of perforation tunnel is alone the direction of the minimum principal horizontal direction, there will be no plastic zone under the same loading conditions. 2) When the density of perforation tunnel is reduced from 8-shots per foot to 4 shots per foot, the plastic zone around the perforation tunnels will be much smaller.
Authors: Yan Xu, Wen Lei Sun, Jian Ping Zhou
Abstract: This paper presents static and dynamic analysis of tower structure supporting a 600KW wind turbine based on the theory of FEM. According to the static and dynamic characteristics of tower structure, the works about simplified models and confirming loads and boundary condition are discussed. In static analysis, under different work conditions the load bearing capacity of tower structure is analyzed with door opening in different directions and without door opening. In dynamic analysis, in order to address the impacts of the foundation on structure, the research discusses the natural frequency and eigenmode from the first sixth modes at the assumption of fixed base and the elastic subgrade. Comparative studies have been performed on the results of the above analysis and some useful conclusions are drawn pertaining to the effectiveness and accuracy of the various models used in the work. Our research work lays a solid foundation of the further static and dynamic analysis.
Authors: Wang Cheng, Tian Bao Ma, Jian Guo Ning
Abstract: Based on the principle of the equivalent momentum of the corresponding elements for internal and external liners, annular shaped charge structure is proposed. The generatrix analytical equations for the external surfaces of the external liner and external charge are deduced. Experimental and numerical studies are conducted to investigate the formation and penetration process of the jet for the annular shaped charge under different initiation radiuses, and the initiation radius corresponding to the detonation wave front matched with the liner is optimized. At this radius, shaped charge can form an ideal cylindrical jet. Moreover, the diameter of the jet approximates the theoretical diameter of the jet, and has satisfactory symmetry and focus.
Authors: M. Mahardika, Kimiyuki Mitsui, Zahari Taha
Abstract: The mechanism of fracture in micro-electrical discharge machining (-EDM) processes is related to the discharge pulses energy. This paper investigates the correlation of fractures and discharge pulses energy in the -EDM of polycrystalline diamond (PCD) to the acoustic emission (AE) signals. The evaluation of fracture mechanism was done by measuring the generation and propagation of elastic wave in single discharge pulse by using AE sensor. The results show a strong correlation between fractures and discharge pulses energy to the AE signals and mechanism of material removal in the -EDM processes.

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