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Semi-analytical Modeling of the Influence of Macro Bending Effects on Micro Contact-Inhomogeneity Problems

Acta Mechanica Solida Sinica 2023年第6期36卷 860-874页

作者： Jinran Li Linlin Sun Ning zhao Pu Li School of Mechanical Engineering Northwestern Polytechnical UniversityXi’an 710072China Key Laboratory of Road Construction Technology and Equipment of the Ministry of Education Chang’an UniversityXi’an 710064China Shaanxi Key Laboratory of Gear Transmissions Xi’an 710072China School of Science Harbin Institute of TechnologyShenzhen 518055China

This study examines the effects of macroscopic bending and microscopic contact loading in inhomogeneous materials using a semi-analytical model based on Eshelby’s equivalent inclusion *** model accounts for bending effects through the beam theory,with bending stress included in the Eshelby’s equivalent inclusion *** macroscopic displacement resulting from bending effects is incorporated into the microscopic contact solver,and the final displacement is determined using the conjugate gradient method in an iterative *** efficiency can be improved by incorporating the discrete convolution and fast Fourier *** core scheme is validated using the finite element method,yielding accurate and efficient results for bending-contact problems in inhomogeneous *** reveal the interplay between bending,contact loading,and inhomogeneity,as stress around the inhomogeneity alters and the stress concentration area expands under increasing bending ***,low-magnitude negative bending moments reduce both contact pressure and stress around the *** position where inhomogeneities are least affected shifts from the neutral surface depending on the coupling *** model provides a valuable bridge for connecting the macroscopic bending effect and microscale contact-inhomogeneity problems by visualizing stress fields and assessing pressure distributions.

关键词： Contact analysis Bending effects Inhomogeneity Equivalent inclusion method Semi-analytical model

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Fault detection for centrifugal chillers using a Kernel Entropy Component Analysis (KECA) method

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Building Simulation 2021年第1期14卷 53-61页

作者： Yudong Xia Qiang Ding zhao Li Aipeng Jiang School of Automation(School of Artificial Intelligence) Hangzhou Dianzi UniversityHangzhouChina Institute of Refrigeration and Cryogenics Zhejiang UniversityHangzhouChina School of Environment&Architecture University of Shanghai for Science&TechnologyShanghaiChina

Fault detection is beneficial for chiller routine operation management in building automation *** the limitations of traditional principal component analysis(PCA)algorithm for chiller fault detection,a so-called kernel entropy component analysis(KECA)method has been developed and the development results are reported in this *** traditional PCA,in KECA,the feature extraction or dimensionality reduction is implemented in a new space,called kernel feature *** new space is nonlinearly related to the input *** data set in the kernel feature space is projected onto a principal component subspace constructed by the feature space principal axes determined by the maximum Rényi entropy rather than the top *** proposed KECA is more suitable to deal with nonlinear process without Gaussian *** the available experimental data from ASHRAE RP-1043,seven typical chiller faults were tested by the proposed KECA method,and the results were compared to that of *** statistics,i.e.T2 and squared prediction error(SPE),were employed for fault detection *** fault detection results showed that the proposed KECA method had a better performance in terms of a higher detection accuracy in comparison to the traditional *** the seven typical faults,the fault detection ratios were over 55%,even at their corresponding least severity level when using the proposed KECA based chiller fault detection method.

关键词： fault detection kernel entropy component analysis Renyi entropy water chillers

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Copper-Coated Graphene Nanoplatelets-Reinforced Al–Si Alloy Matrix Composites Fabricated by Stir Casting Method

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Acta Metallurgica Sinica(English Letters) 2021年第1期34卷 111-124页

作者： Xiaoqi Han Lizhuang Yang Naiqin zhao Chunnian He School of Materials Science and Engineering and Tianjin Key Laboratory of Composite and Functional Materials Tianjin UniversityTianjin 300072China Joint School of National University of Singapore and Tianjin University International Campus of Tianjin UniversityBinhai New CityFuzhou 350207China Collaborative Innovation Center of Chemical Science and Engineering(Tianjin) Tianjin 300072China Key Laboratory of Advanced Ceramics and Machining Technology Ministry of EducationTianjin UniversityTianjin 300072China

In this study,Cu nanoparticles-coated graphene nanoplatelets(Cu-NPs@GNPs)were synthesized by a simple in situ method with the assistance of Na Cl templates and used for reinforcing Al–10 Si composites through stir casting *** experimental results showed that the coating of Cu-NPs on the GNPs could compromise the density mismatch between GNPs and metal matrix and eff ectively hinder the float of GNPs during *** reaction of Cu-NPs and Al matrix could protect the structural integrity of GNPs as well as improve the interfacial wettability between GNPs and the matrix,thus promoting the uniform dispersion of GNPs in the *** a result,the as-prepared 0.5 wt%Cu-NPs@GNPs/Al–10 Si composite exhibited a tensile strength of 251 MPa(45%higher than the Al–10 Si)with a total elongation of 15%.The strengthening eff ects were mainly attributed to the following three reasons:Firstly,the Cu-NPs coating improved the interfacial bonding between GNPs and Al matrix which promoted the load transfer from the matrix to the ***,the nanoscale Al 2 Cu formed by the reaction of Cu-NPs and Al matrix played a role in precipitation ***,GNPs refined the silicon phases and improved the monolithic performances of the composites.

关键词： Al–Si alloy Graphene Stir casting Wettability Si phase refinement

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Mechanical Behavior and Microstructure Evolution during Tensile Deformation of Twinning Induced Plasticity Steel Processed by Warm Forgings

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Journal of Wuhan University of Technology(Materials Science) 2024年第2期39卷 417-424页

作者：王文 zhao Modi WANG Xingfu 汪聃韩福生 School of Aerospace and Mechanical Engineering Flight College Changzhou Institute of TechnologyChangzhou 213032China Key Laboratory of Materials Physics Institute of Solid State PhysicsChinese Academy of SciencesHefei 230031China School of Physics and Electronic Information Yan’an UniversityYan’an 716000China

The mechanical behavior and microstructural evolution of an Fe-30Mn-3Al-3Si twinninginduced plasticity(TWIP)steel processed using warm forging was *** is found that steel processed via warm forging improves comprehensive mechanical properties compared to the TWIP steel processed via cold rolling,with a high tensile strength(R_(m))of 793 MPa,a yield strength(R_(P))of 682 MPa,an extremely large R_(P)/R_(m)ratio as high as 0.86 as well as an excellent elongation rate of 46.8%.The microstructure observation demonstrates that steel processed by warm forging consists of large and elongated grains together with fine,equiaxed *** micro-defect configurations were also observed within the steel,including dense dislocation networks and a few coarse deformation *** the plastic deformation proceeds,the densities of dislocations and deformation twins significantly ***,a great number of slip lines could be observed in the elongated *** findings reveal that a much more dramatic interaction between microstructural defect and dislocations glide takes place in the forging sample,wherein the fine and equiaxed grains propagated dislocations more rapidly,together with initial defect configurations,are responsible for enhanced strength ***,larger,elongated grains with more prevalently activated deformation twins result in high plasticity.

关键词： TWIP steel twinning mechanical property deformation mechanism microstructure

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Mechanical behavior and damage constitutive model of sandstone under hydro-mechanical (H-M) coupling

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International Journal of Mining Science and Technology 2024年第6期34卷 837-853页

作者： Tao Tan Chunyang Zhang Yanlin zhao Xiaoshuang Li School of Resources and Environmental Engineering Wuhan University of TechnologyWuhan 430070China State Key Laboratory of Safety and Health in Metal Mines Maanshan 243000China Sinosteel Maanshan General Institute of Mining Research Co. Ltd.Maanshan 243000China School of Resource&Environment and Safety Engineering Hunan University of Science and TechnologyXiangtan 411201China School of Urban Construction Changzhou UniversityChangzhouJiangsu 213164China

Underground engineering often passes through water-rich fractured rock masses, which are prone to fracture and instability under the long-term coupling of in-situ stress field and pore water(P-W) pressure, ultimately threatening the stability of underground structures. In order to explore the mechanical properties of rocks under H-M coupling, the corresponding damage constitutive(D-C) model has become the focus of attention. Considering the inadequacy of the current research on rock strength parameters,energy evolution characteristics and D-C model under H-M coupling, the mechanical properties of typical sandstone samples are discussed based on laboratory tests. The results show that the variation of characteristic stresses of sandstone under H-M coupling conforms to the normalized attenuation equation and Mohr-Coulomb(M-C) criterion. The P-W pressure mechanism of sandstone exhibits a dynamic change from softening effect to H-M fracturing effect. The closure stress is mainly provided by cohesive strength, while the initiation stress, damage stress, and peak stress are jointly dominated by cohesive strength and friction strength. In addition, residual stress is attributed to the friction strength formed by the bite of the fracture surface. Subsequently, the energy evolution characteristics of sandstone under H-M coupling were studied, and it was found that P-W pressure weakened the energy storage capacity and energy dissipation capacity of sandstone, and H-M fracturing was an important factor in reducing its energy storage efficiency. Finally, combined with energy dissipation theory and statistical damage theory, two types of D-C models considering P-W pressure are proposed accordingly, and the model parameters can be determined by four methods. The application results indicate that the proposed and modified D-C models have high reliability, and can characterize the mechanical behavior of sandstone under H-M coupling, overcome the inconvenience of existing D-C models

关键词： H-M coupling Water-saturated sandstone Mechanical mechanism Energy evolution D-C model

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Experimental and numerical investigation of TVOC concentrations and ventilation dilution in enclosed train cabin

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Building Simulation 2022年第5期15卷 831-844页

作者： Le zhao Huang Zhou Yuzhen Jin Zeqing Li Key Laboratory of Fluid Transmission Technology of Zhejiang Province Zhejiang Sci-Tech UniversityHangzhou 310018China Hangzhou Yunze Environmental Technology Co. LtdHangzhouChina

Air pollution in trains is an important factor threatening human health,which has attracted more and more attention in the worldwide public health *** this study,one cabin of a fully enclosed train was taken as an example to conduct experimental and numerical research on pollution level and distribution characteristic of total volatile organic compound(TVOC).The results show that when the average emission rate under daily environmental conditions was taken as the reference,TVOC concentration in the cabin exceeded the limit level of Chinese Indoor Air Quality Standard by more than 4 *** obvious pollutants accumulative phenomenon could be found at bottoms and corners under the action of *** air inlets at the roof of the train,mean age of air ranged from 30 s to 50 s in the breathing *** concentration of pollutants was the lowest at 2.5-5 m from the center point of the cabin structure,and the ventilation efficiency was the *** introduction of clean fresh air could effectively eliminate *** the complete displacement ventilation rates were 51.4 h^(-1) and 28.6 h_1,the removal efficiency of pollutants was about 0.85 and 0.48 mg/m3 per minute,*** study was helpful to the improvement and optimization design of air quality and ventilation mode in trains.

关键词： indoor air quality VOCs CFD railway cabins ventilation dilution

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Data-based Fault Tolerant Control for Affine Nonlinear Systems Through Particle Swarm Optimized Neural Networks

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IEEE/CAA Journal of Automatica Sinica 2020年第4期7卷 954-964页

作者： Haowei Lin Bo zhao Derong Liu Cesare Alippi the School of Automation Guangdong University of TechnologyGuangzhou 510006China the School of Systems Science Beijing Normal UniversityBeijing 100875China the Dipartimento di Elettronica e Informazione Politecnico di MilanoMilano 20133Italy the Universita’Della Svizzera Italiana LuganoSwitzerland

In this paper, a data-based fault tolerant control(FTC) scheme is investigated for unknown continuous-time(CT)affine nonlinear systems with actuator faults. First, a neural network(NN) identifier based on particle swarm optimization(PSO) is constructed to model the unknown system dynamics. By utilizing the estimated system states, the particle swarm optimized critic neural network(PSOCNN) is employed to solve the Hamilton-Jacobi-Bellman equation(HJBE) more ***, a data-based FTC scheme, which consists of the NN identifier and the fault compensator, is proposed to achieve actuator fault tolerance. The stability of the closed-loop system under actuator faults is guaranteed by the Lyapunov stability theorem. Finally, simulations are provided to demonstrate the effectiveness of the developed method.

关键词： Adaptive dynamic programming(ADP) critic neural network data-based fault tolerant control(FTC) particle swarm optimization(PSO)

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Transient analysis on surface heated piezoelectric semiconductor plate lying on rigid substrate

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Applied Mathematics and Mechanics(English Edition) 2022年第12期43卷 1841-1856页

作者： Luke zhao Sen GU Yaqin SONG Feng JIN State Key Laboratory for Strength and Vibration of Mechanical Structures School of Aerospace EngineeringXi'an Jiaotong UniversityXi'an 710049China

Based on the thermo-electro-elastic coupling theory,the mathematical model for a surface heated piezoelectric semiconductor(PS)plate is developed in the time *** the direct and inverse Laplace transformations to the established model,the mechanical and electrical responses are *** comparison between the analytical solution and the finite element method(FEM)is conducted,which illustrates the validity of the *** calculated results show that the maximum values of the mechanical and electrical fields appear at the heating ***,the perturbation carriers tend to concentrate in the zone near the heating surface under the given boundary *** can also be observed that the heating induced elastic wave leads to jumps for the electric potential and perturbation carrier density at the *** the thermal relaxation time is introduced,all the field quantities become smaller because of the thermal lagging ***,it can be found that the thermal relaxation time can describe the smooth variation at the jump ***,for a plate with P-N junction,the effect of the interface position on the electrical response is *** effects of the initial carrier density on the electrical properties are discussed in *** conclusions in this article can be the guidance for the design of PS devices serving in thermal environment.

关键词： thermo-electro-elastic coupling piezoelectric semiconductor(PS) surface heating transient analysis

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Fracture characterization and permeability prediction by pore scale variables extracted from X-ray CT images of porous geomaterials

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Science China(Technological Sciences) 2020年第5期63卷 755-767页

作者： zhao Zhi ZHOU Xiao-Ping QIAN Qi-Hu School of Civil Engineering Chongqing UniversityChongqing 400045China State Key Laboratory of Disaster Prevention and Mitigation of Explosion and Impact PLA University of Science and TechnologyNanjing 210014China

Pore scale variables(e.g.,porosity,grain size)are important indexes to predict the hydraulic properties of porous geomaterials.X-ray images from ten types of intact sandstones and another type of sandstone samples subjected to triaxial compression are used to investigate the permeability and fracture characteristics.A novel double threshold segmentation algorithm is proposed to segment cracks,pores and grains,and pore scale variables are defined and extracted from these X-ray CT images to study the geometric characteristics of microstructures of porous ***,novel relations among these pore scale variables for permeability prediction are established,and the evolution process of cracks is *** results indicate that the porescale permeability is prominently improved by *** addition,excellent agreements are found between the measured and the estimated pore scale variables and *** established correlations can be employed to effectively identify the hydraulic properties of porous geomaterials.

关键词： sandstones X-ray CT images pore scale variables permeability prediction cracks characterization

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Subspace Clustering via Block-Diagonal Decomposition

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Chinese Journal of Electronics 2024年第6期33卷 1373-1382页

作者： Zhiqiang FU Yao zhao Dongxia CHANG Yiming WANG Institute of Information Science Beijing Jiaotong University Beijing Key Laboratory of Advanced Information Science and Network Technology China Construction Bank

The subspace clustering has been addressed by learning the block-diagonal self-expressive matrix. This block-diagonal structure heavily affects the accuracy of clustering but is rather challenging to obtain. A novel and effective subspace clustering model, i.e., subspace clustering via block-diagonal decomposition(SCBD), is proposed,which can simultaneously capture the block-diagonal structure and gain the clustering result. In our model, a strict block-diagonal decomposition is introduced to directly pursue the k block-diagonal structure corresponding to k clusters. In this novel decomposition, the self-expressive matrix is decomposed into the block indicator matrix to demonstrate the cluster each sample belongs to. Based on the strict block-diagonal decomposition, the block-diagonal shift is proposed to capture the local intra-cluster structure, which shifts the samples in the same cluster to get smaller distances and results in more discriminative features for clustering. Extensive experimental results on synthetic and real databases demonstrate the superiority of SCBD over other state-of-the-art methods.

关键词： Accuracy Databases Data models Matrix decomposition

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