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Hot Deformation Behavior of Squeeze Casting SiC_p/2 A50 Matrix Composites

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Journal of Wuhan University of Technology(Materials Science) 2012年第3期27卷 443-449页

作者：徐宏张新 School of Materials Science and engineering North University of China Beijing engineering research Center for Advanced Manufacturing and Evaluation of Special Vehicle Parts Center of Technology Beijing North Vehicle Group Corporation

The flow stress behaviors of squeeze casting SiCp/2A50 matrix composites were investigated by means of compression tests on a Gleeble 1500 therma1 mechanical simulator at isothermal constant strain rates ranging from of 0.001 to 1.0 with the testing temperature ranging from 350 to 500 ℃. The experiments showed that the relationship between stress and strain was obviously influenced by the strain rate and temperature. Dynamic recrystallization generally occurred at a higher temperature and a 1ower strain rate. A linear equation could be fitted between the Zener-Hollomon parameter Z and stress in the experiments. The mean value reciprocal of temperature at every true strain had a linear relation with natural logarithm of Z parameter, and the correlation coefficient, R=0.99, which was very significant by examination. The hot deformation activation energy of SiCp/2A50 matrix composites was 163.47 KJ/mol by calculation.

关键词： SiCp/2A50 matrix composites deformation activation energy stress and strain dynamic recrystallization

Ambient vibration testing and updating of the finite element model of a simply supported beam bridge

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Frontiers of Structural and Civil engineering 2011年第3期5卷 344-354页

作者： Ivan Gomez ARAUJO Esperanza MALDONADO Gustavo Chio CHO School of Civil engineering Research Group INMEIndustrial University of SantanderSantanderColombia

An ambient vibration test on a concrete bridge constructed in 1971 and calibration of its finite element model are *** bridge is characterized by a system of post-tensioned and simply supported *** dynamic characteristics of the bridge,*** frequencies,mode shapes and damping ratios were computed from the ambient vibration tests by using the Eigensystem Realization Algorithm(ERA).Then,these characteristics were used to update the finite element model of the bridge by formulating an optimization problem and then using Genetic Algorithms(GA)to solve *** the results of the ambient vibration test of this type of bridge,it is concluded that two-dimensional mode shapes exist:in the longitudinal and transverse;and these experimentally obtained dynamic characteristics were also achieved in the analytical model through *** application of GAs as optimization techniques showed great versatility to optimize any number and type of variables in the model.

关键词： modal analysis parameter identification ambient vibration test Eigensystem Realization Algorithm(ERA)method finite element method

research on the Follow-Up Control Strategy of Biaxial Fatigue Test of Wind Turbine Blade Based on Electromagnetic Excitation

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Energy engineering 2023年第10期120卷 2307-2323页

作者： Wenzhe Guo Leian Zhang Chao Lv Weisheng Liu Jiabin Tian School of Mechanical engineering Shandong University of TechnologyZibo255049China engineering and Technology Department CRRCWind Power(Shandong)Co.Ltd.Jinan250104China testing Center Lianyungang Zhongfulianzhong Composite Material Group Co.Ltd.Lianyungang222000China

Aiming at the drift problem that the tracking control of the actual load relative to the target load during the electromagnetic excitation biaxial fatigue test of wind turbine blades is easy to drift,a biaxial fatigue testingmachine for electromagnetic excitation is designed,and the following strategy of the actual load and the target load is studied.A Fast Transversal Recursive Least Squares algorithm based on fuzzy logic(Fuzzy FTRLS)is proposed to develop a fatigue loading following dynamic strategy,which adjusts the forgetting factor in the algorithmthrough fuzzy logic to overcome the contradiction between convergence accuracy and convergence speed and solve the phenomenon of amplitude overshoot and phase lag of the actual load relative to the target *** with the previous research results,a simulation model was constructed to verify the strategy’s *** tests were carried out to verify its follow-up *** results showthat the tracking error of flapwise and edgewise direction iswithin 4%,which has better robustness and dynamic and static performance than the traditional Recursive Least Squares(RLS)algorithm.

关键词： Wind turbine blades biaxial fatigue loading tracking control fuzzy FTRLS

Creep properties and permeability evolution in triaxial rheological tests of hard rock in dam foundation

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Journal of Central South University 2012年第1期19卷 252-261页

作者： XU Wei-ya WANG Ru-bin WANG Wei ZHANG Zhi-liang ZHANG Jiu-chang WANG Wen-yuan research Institute of Geotechnical engineering Hohai UniversityNanjing 210098China College of Water Conservancy and Hydropower engineering Hohai UniversityNanjing 210098China Kunming Design and research Institute China Hydropower Consulting Group Co.Kunming 650051China

Triaxial creep tests were carried out under seepage pressure by using rock servo-controlled triaxial rheology testing equipment. Based on experimental results, rock rheological properties influenced by seepage-stress coupling were studied, and variations of seepage rate with time in complete creep processes of rock were analyzed. It is shown that, when the applied stress is less than failure stress level, the creep deformation is not obvious, and its main form is steady-state creep. When applied stress level is greater than or less than but close to fracture stress, it is easier to see the increase of creep deformation and the more obvious accelerative creep characteristics. The circumferential creep deformation is obviously higher than the axial creep deformation. At the stage of steady-state creep, the average of seepage flow rate is about 4.7×10-9 rn/s at confining pressure （tr3） of 2 MPa, and is about 3.9×10-9 m/s at a3 of 6 MPa. It is seen that the seepage flow rate at or3 of 2 MPa in this case is obviously larger than that at tr3 of 6 MPa. At the stage of creep acceleration, the seepage flow rate is markedly increased with the increase of time. The variation of rock permeability is directly connected to the growth and evolution of creep crack. It is suggested that the permeability coefficient in complete creep processes of rock is not a constant, but is a function of rock creep strain, confining pressure, damage variable and pore water pressure. The results can be considered to provide a reliable reference for the establishment of rock rheological model and parameter identification.

关键词： rock mechanics creep properties volcanic breccia triaxial rheology test permeability evolution creep damage

Density effect and intraspecific competition in a leaf-mining moth on bamboo leaves

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Journal of Forestry research 2019年第2期30卷 689-697页

作者： Xiaohua Dai Jiasheng Xu Qingyun Guo Shengchang Lai Peng Liu Juju Fan Peirong Tang Leafminer group School of Life and Environmental Sciences Gannan Normal University National Navel Orange engineering research Center Jiulianshan National Nature Reserve Administration

When confined to a single leaf, the larvae of most leafminers should suffer intense intraspecific competition. The survival and performance of individuals are expected to decline with increasing larval density within a leaf, showing a negative density-dependent effect. The maximum density of an Elachista Treitschke(Lepidoptera:Elachistidae) miner on Indocalamus tessellatus(Munro)Keng f.(Poaceae: Bambusoideae) under natural conditions can be greater than 40 per leaf, making this a good system for studying intraspecific competition and density *** counted the number of leaves with different mine densities in the field and found a clumped distribution of leafminer larvae among host leaves. The emergence rates of pupae(and last-instar larvae), adults and parasitoids were inversely correlated with larval density. Pupal weight and adult weight also showed negative relationships with larval density. However, pairwise tests showed that there might be no differences in pupal or adult weight at larval densities of 1–10 mines per leaf, indicating that densitydependent effects are more obvious at densities greater than 10 mines per leaf. Intraspecific competition could lead to stable density and consistent body size in surviving individual insects, which would help maintain a sustainable population size. The density threshold could be an indicator of the balance between intraspecific competitive detriments and conspecific aggregation benefits; however, the validity of the threshold density hypothesis requires further testing and confirmation.

关键词： Leafminer Density-dependent Distribution pattern Sustainable population Threshold density

Numerical evaluation of strength and deformability of fractured rocks

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Journal of Rock Mechanics and Geotechnical engineering 2013年第6期5卷 419-430页

作者： Majid Noorian Bidgoli Zhihong Zhao Lanru Jing Department of Land and Water Resources engineering Engineering Geology and Geophysics Research GroupRoyal Institute of Technology (KTH) Department of Geological Sciences Stockholm University

Knowledge of the strength and deformability of fractured rocks is important for design, construction and stability evaluation of slopes, foundations and underground excavations in civil and mining engineering. However, laboratory tests of intact rock samples cannot provide information about the strength and deformation behaviors of fractured rock masses that include many fractures of varying sizes, orientations and locations. On the other hand, large-scale in situ tests of fractured rock masses are economically costly and often not practical in reality at present. Therefore, numerical modeling becomes necessary. Numerical predicting using discrete element methods(DEM) is a suitable approach for such modeling because of their advantages of explicit representations of both fractures system geometry and their constitutive behaviors of fractures, besides that of intact rock matrix. In this study, to generically determine the compressive strength of fractured rock masses, a series of numerical experiments were performed on two-dimensional discrete fracture network models based on the realistic geometrical and mechanical data of fracture systems from feld mapping. We used the UDEC code and a numerical servo-controlled program for controlling the progressive compressive loading process to avoid sudden violent failure of the models. The two loading conditions applied are similar to the standard laboratory testing for intact rock samples in order to check possible differences caused by such loading conditions. Numerical results show that the strength of fractured rocks increases with the increasing confning pressure, and that deformation behavior of fractured rocks follows elasto-plastic model with a trend of strain hardening. The stresses and strains obtained from these numerical experiments were used to ft the well-known Mohr-Coulomb(MC) and Hoek-Brown(H-B) failure criteria, represented by equivalent material properties defning these two criteria. The results show that bot

关键词： Strength Deformability Fractured rocks Discrete element methods(DEM) Failure criteria

A data analytics-based tool for the detection and diagnosis of anomalous daily energy patterns in buildings

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Building Simulation 2021年第1期14卷 131-147页

作者： Marco Savino Piscitelli Silvio Brandi Alfonso Capozzoli Fu Xiao Department of Energy“Galileo Ferraris” TEBE research groupPolitecnico di TorinoTurinItaly Department of Building Services engineering The Hong Kong Polytechnic UniversityHong KongChina

In this paper,a tool for the detection and diagnosis of anomalous electrical daily energy patterns relative to a transformer substation of a university campus was developed and *** an innovative pattern recognition analysis consisting in a multi-step clustering process,six clusters of anomalous daily load profiles were identified and isolated in two-year historical data of total electrical energy *** infrequent electrical load profiles were found to be strongly affected,in terms of both shape and magnitude,by the energy consumption behaviour related to the heating/cooling mechanical ***,a fault-free predictive model,which uses artificial neural network(ANN)in combination with a Regression Tree,was developed to detect anomalous trends of the electrical energy *** model was able to detect the 93.7%of the anomalous profiles and only the 5%of fault-free days were wrongly predicted as ***,a diagnosis phase was conceived and validated with a testing data set.A number of daily abnormal load profiles were detected and compared with the centroids of the anomalous clusters identified in the pattern-recognition *** work led to the development of a flexible intelligent tool useful for operating a continuous commissioning of the campus facilities.

关键词： anomaly detection data analytics energy management pattern recognition prediction models

Mechanical Properties of Two Kinds of New Cold-Formed Flange-Closed Welding Section Members

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沈阳建筑大学学报（自然科学版） 2011年第6期27卷 1021-1032页

作者：武胜 College of Civil engineering Northeast Forestry University Workstation for Postdoctoral Fellows of Heilongjiang Construction engineering group research Station on Civil engineering for Postdoctoral Fellows of Harbin Institute of Technology

The hollow flange beam(HFB) is a unique cold-formed steel section developed in Australia for use as a flexural ***′s a particular cross section with two torsion rigid closed triangular flanges and a comparatively flexible web,and it is a type of high efficient cross *** paper presents two kinds of new cold-formed flange-closed welding sections named HF1 and HF2 according to different section component and parameters of *** finite element method has been adopted to investigate the mechanical properties such as buckling mode,deformation process,rigidity,ductility and correlation curve of two kinds of new section members which being subjected to axial compression,flexure,combined compression and *** comparisons of the consumed steel quantities of per unit load carrying capacity between new section members and the same section dimensions of cold-formed C-section members have been carried *** conclusions can be drawn from above work that the new sections have some superior properties including higher load carrying capacity and section modulus,sufficient section stiffness,and difficult occurrence for the sub element local *** new sections are suitable for bearing flexure,compression,combined compression and *** new sections′ consumed steel quantities of per unit load carrying capacity are almost half as those of the same dimension C-section members′.The experimental investigation is carried out further on the new cold-formed flange-closed welding section members and can be used in the practical engineering.

关键词： hollow flange beam cold-formed steel members finite element analysis mechanical properties

Microstructures and strengthening mechanisms of Mg-8.2Gd-4.6Y-1.5Zn-0.4Zr alloy containing LPSO,β’ and γ type phases

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Journal of Rare Earths 2020年第10期38卷 1119-1125,I0004页

作者： Xiangsheng Xia Kui Zhang Minglong Ma Ting Lie State Key Laboratory of Non-Ferrous Metals and Processes GRINM Co.LtdBeijing 700088China GR1MAT engineering Institute Co. Ltd.Beijing 101400China General research Institute for Non-Ferrous Metals Beijing 100088China Southwest Technology and engineering research Institute Chongqing 400039China National Center of Analysis and testing for Nonferrous Metals and Electronic Materials China United Test&Certification Co.Ltd.GRINM Group Co.Ltd.Beijing 100088China

The microstructures and strengthening mechanisms of the Mg-8.2 Gd-4.6 Y-1.5 Zn-0.4 Zr(wt%) alloy with long-period stacking ordered(LPSO),β’ and γ type phases were systematically *** results show that the LPSO with lamellar and block structures forms near the grain *** grains are clearly refined,and the 18 R LPSO phase is oriented along the extrusion direction after *** particles also precipitate from the Mg matrix *** extruded alloy exhibits a remarkable agehardening response,and mechanical properties,with a tensile strength(TS) of 449 MPa,yield strength(YS) of 362 MPa,and elongation of 7.9% obtained in the peak-aged *** strengthening mechanisms of the alloy in different states are *** boundary and precipitation strengthening are the main strengthening mechanisms for the peak-aged alloy.

关键词： Mg-Cd-Y-Zn-Zr alloy LPSO phase Microstructure Mechanical properties Strengthening mechanism Rare earths