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Evaluation method and application of urban underground space networked expansion disturbance

Zhejiang Daxue Xuebao (Gongxue Ban)/Journal of Zhejiang University (engineering Science) 2022年第7期56卷 1363-1374页

作者： Liu, Zhi-chun Lei, Sheng-Xiang Li, Guo-Liang Zhang, Zhen-Bo Hu, Zhi-Nan State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang050043 China School of Civil Engineering Shijiazhuang Tiedao University Shijiazhuang050043 China China Railway Construction Limited Corporation Beijing100855 China China Railway First Survey and Design Institute Group Limited Corporation Xi’an710043 China

Five expansion pattern types and eighteen structure types were proposed, as well as the "four elements" of the expansion system based on the investigated cases of underground space expansion projects in order to evaluate the disturbance effect of urban underground space network extension construction. The total evaluation objective composed of four sub-objectives, including extensional structure, existing structure, stratum and surrounding environment, and six stress and displacement evaluation indexes were determined based on the analysis of the expansion disturbance conduction path and the internal working mechanism of its elements. The analytic hierarchy process (AHP) was used to construct the judgment matrix. The evaluation index weight was determined by expert scoring. Then the control value grading method was applied to determine the membership degree of the evaluation index, thereby constructing a five-level urban underground space network expansion disturbance classification evaluation standard. The application of the above evaluation method was conducted. The order of expansion disturbance degree of different expansion methods is expansion by small>vertical expansion>horizontal expansion >connected connection, and the order of expansion disturbance degree of different stratum is soft soil >loess >alluvial-diluvial strata>rock. The expansion disturbance degree will decrease significantly with the increase of the proximity distance for horizontal expansion. © 2022 Zhejiang University. All rights reserved.

关键词： Grading

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A Study on the Mesoscopic Damage of Asphalt Mixture Under Freeze-Thaw cycles Based on Discrete Element Theory

SSRN

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SSRN 2023年

作者： Xu, Shuo Yan, Zhanyou Zhao, Li School of Civil Engineering Shijiazhuang Tiedao University Hebei China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Hebei China School of Traffic and Transportation Shijiazhuang Tiedao University Hebei China

In order to study the damage and failure of asphalt mixture under uniaxial loading under freeze-thaw cycle, a damage constitutive model is constructed based on the Particle Flow code (PFc2D). Through four sets of uniaxial compression laboratory tests with different freeze-thaw cycles, numerical simulation with the help of PFc2D, analysis of macroscopic failure of asphalt mixture and evolution law of internal microcracks from mesoscopic perspective, the equation of the relationship between the damage variable and the strain is established. The results of the study showed that: (1) The numerical simulations are in good agreement with the experimental results. (2) The increase of freeze-thaw cycles will increase the freeze-thaw damage variable and peak strain of asphalt mixture and reduce the compressive strength of asphalt mixture. (3) The established piecewise function expression can fit the relationship between the damage variable and the strain well. This study provides a convenient method for the mesoscopic study of asphalt mixture loading test under freeze-thaw cycle. © 2023, The Authors. All rights reserved.

关键词： Asphalt mixtures

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Nonlinear Analysis Of Thermo-Deformation-Polarization-carrier coupling Response of Piezoelectric Semiconductor Plates

SSRN

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SSRN 2024年

作者： Xiao, Zhengguang Liu, Jinxi Zhang, chunli chen, Weiqiu Department of Engineering Mechanics Zhejiang University Hangzhou310027 China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang050043 China Huanjiang Laboratory Zhuji311816 China Faculty of Mechanical Engineering & Mechanics Ningbo University Ningbo315211 China

We present two-dimensional (2-D) thermo-deformation-polarization-carrier (TDPc) coupling equations for piezoelectric semiconductor (PS) thin plates incorporating both geometric and physical nonlinearities. To do so, we assume that the in-plane displacements, electric potential, concentration of carriers, and temperature have a linear distribution while the out-plane displacement has a parabolic distribution along the thickness direction. The derived TDPc coupling plate model comprises the zeroth and first order equations, which can be used to analyze the respective in-plane extensional and out-of-plane flexural deformations of PS plates with nonlinear multi-field coupling. The effectiveness of the developed plate model is validated. Based on the derived 2-D TDPc coupling equations, the nonlinear multi-field coupling mechanical responses of PS plates under single local mechanical or thermal load and their combinations are investigated in detail. The controlling mechanism of the combined mechanical and thermal loads on the electric potential and electron concentration as well as the formation of a potential well in PS plates is also revealed. © 2024, The Authors. All rights reserved.

关键词： Polarization

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Experimental Study on Geogrid-Soil Interface Properties Based on Pullout Tests: A case Study

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SSRN 2024年

作者： Wang, Zhijie Zhang, Guowei Yang, Guangqing Qin, Yan Zhou, Shiguang State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang050043 China School of Civil Engineering Shijiazhuang Tiedao University Shijiazhuang050043 China China Railway Society Beijing100844 China

The geogrid-soil interaction, which is crucial to the safety and stability of reinforced soil structures, is affected by the parameters of soils and geogrids. To investigate the influence of backfill and geogrid on their interface behavior of the reinforced soil retaining walls in Yichang section of Shanghai-chongqing-Sichuan high-speed railway, a series of geogrid pullout tests were carried out. The development and evolution law of pullout force-pullout displacement curves and interface characteristics between geogrid and soil under various testing conditions were analyzed. The results showed that with increasing water content, the geogrid pullout force decreased under the same pullout displacement. The apparent friction angle of the geogrid-soil interface showed a slowly increasing trend with increasing water content. The variation of the apparent friction angle ranged between 9.2° and 10.7°. The apparent cohesion, however, decreased rapidly with increasing water content. With increasing degree of compaction, the apparent friction angle and the apparent cohesion of the geogrid-soil interface gradually increased. The change of the apparent cohesion with the compaction degree was more significant. When the degree of compaction increased from 0.87 to 0.93, the apparent cohesion increased around 7 times. The tensile strength of geogrid has certain influence on its pullout force-pullout displacement relationship. High-strength geogrid could significantly improve the mechanical properties of the geogrid-soil interface. The investigation results can provide some reference for the design and construction of geogrid reinforced soil structures. © 2024, The Authors. All rights reserved.

关键词： Tensile strength

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Problems and corrections of classical Mathematical Model for Piecewise Linear system

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SSRN 2024年

作者： Shen, Yongjun Zhang, Ruiliang Han, Dong Liu, Xiaoyan School of Mechanical Engineering Shijiazhuang Tiedao University Shijiazhuang050043 China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang050043 China Department of Electrical and Information Engineering Hebei Jiaotong Vocational and Technical College Shijiazhuang050035 China

Due to the existence of gap or backlash, many mechanical systems can be simplified into piecewise linear models. The dynamic study on mechanical system should be based on reliable mathematical model, so that it is very important to determine the contact point and separation point between the primary system and the auxiliary spring system (ASS) in the piecewise linear systems. In most existing literatures on piecewise linear systems, the contact point and the separation point of the mathematical model are fixed at the gap. But in this paper, it is found that the contact point and separation point actually change with the system parameters when the ASS contains damper, which implies the most existing mathematical model are incorrect. It is firstly demonstrated through numerical solution that the primary system will prematurely separate from the ASS before reaching the gap under harmonic excitation, which shows the incorrectness of the classical mathematical model. Then, based on the mechanical model and engineering practice, two corrected mathematical models are proposed. And the motions of the primary system and ASS after prematurely separation in the corrected models are studied. Finally, through comparison of the contact point, separation point, amplitude-frequency curves and motion state between the corrected models and the classical mathematical model, it can be concluded that the corrected models are more reasonable. And the comparisons with the experimental data implies that the corrected models can better reflect the engineering practice. These results will be helpful to the study and design of the piecewise linear system. © 2024, The Authors. All rights reserved.

关键词： Piecewise linear techniques

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Effect of Deformation Twinning on Microstructure Refinement of Fe-38mn Alloy During Friction Stir Processing

SSRN

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SSRN 2022年

作者： Sang, Deli Xin, Xiaoli Fu, Ruidong Li, Yijun College of Materials Science and Engineering Shijiazhuang Tiedao University Hebei Shijiazhuang050000 China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Hebei Shijiazhuang050043 China State Key Laboratory of Metastable Materials Science and Technology Yanshan University Hebei Qinhuangdao066004 China

The effect of deformation twinning on microstructure refinement was investigated for Fe-38Mn alloy during friction stir processing. It was proved that the friction stir processing microstructure of Fe-38Mn alloy was gradient distribution. The stir zone contained both recrystallized grains and fine deformed grains with average grain size of about 15 μm, and the proportion of twin boundaries in the deformed grain zone was up to 35%. Moreover, the cyclic multidirectional shear induced micro-shear bands and sub-grains with high density dislocations, as well as plentiful deformation twins. The microstructure refinement of Fe-38Mn alloy during friction stir processing resulted from the dynamic recrystallization mechanism and twinning mechanism. In addition, the cyclic multidirectional shear deformation enhanced the deformation twinning effect, so that the microstructure refinement process was completed quickly and effectively. The above works indicate a dynamic mechanism of microstructure refinement in term of the deformation twinning during friction stir processing. © 2022, The Authors. All rights reserved.

关键词： Binary alloys

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Research on Intelligent Trajectory Finding and Escape Dilemma Tracking Strategy of Tire Blowout Vehicle

SSRN

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SSRN 2023年

作者： Han, Zexuan Lu, Yongjie Li, Haoyu Zhang, Junning School of Mechanical Engineering Shijiazhuang Tiedao University Shijiazhuang China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhaung Tiedao University Shijiazhuang China Department of Engineering Mechanics Shijiazhuang Tiedao University Shijiazhuang China School of Mechanicsand Engineering Science Shanghai University Shanghai China

To improve the safety and stability after a vehicle tire blowout in complex road environment, an intelligent trajectory finding and escape dilemma tracking strategy integrating decision-making, planning and control is proposed. The nonlinear static Dugoff tire formula is improved based on the dynamic change of tire blowout mechanical parameters. combined with multi-body vehicle dynamics model and steering control driver model, a joint simulation platform for tire blowout vehicle is established. considering the real-time state of the vehicle and the complexity of the road environment, the original driving trajectory is kept. And based on the Bessel curve method and the fifth-order polynomial method, the vehicle obstacle avoidance and lane change path are planned. The model predictive control algorithm is designed to achieve escape dilemma tracking control of the vehicle after tire blowout. The carSim/Simulink joint simulation test is used to verify the control effect of the intelligent trajectory finding and escape dilemma tracking strategy in different scenarios. The results show that this strategy can reasonably and effectively plan the trajectory of keeping, obstacle avoidance and lane change, and bring vehicle out of danger in time while maintaining safety and stability. © 2023, The Authors. All rights reserved.

关键词： Trajectories

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Fault Diagnosis Method for Multiple Sources based on IESFSc-SSRgram

Fault Diagnosis Method for Multiple Sources based on IESFSC-...

引用

International conference on Sensing, Diagnostics, Prognostics, and control (SDPc)

作者： Wu Zhihao Gong Shixian Huang chenguang Jin Hang Liu Zechao National Engineering Laboratory CRRC Qingdao Sifang Locomotive and Rolling Stock Co. Ltd Qingdao China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structure and School of Mechanical Engineering Shijiazhuang Tiedao University Shijiazhuang China Weichai Power Co. Ltd. Data Management Engineering Center Weifang China Institute of Magnetic Levitation and Electromagnetic Propulsion China Aerospace Science and Industry Corporation Limited Beijing China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang China

ISBN: (数字)9798350388855

ISBN: (纸本)9798350388862

The division and determination of frequency bands are always core problems in fault diagnosis methods for rotating machinery. currently, the frequency band division strategy of most fault diagnosis methods is the 1/3-binary tree or realized by wavelet packet transform (such as fast kurtosis diagram and Autogram). This method is relatively fixed, making it difficult to accurately cover the resonance frequency band and achieve multi-source fault identification. To address the above problems, an adaptive frequency band division strategy based on Fast Spectral correlation (FSc) and Scale-Space Representation (SSR) is proposed. The enhanced enveloping spectrum (EES) of each frequency band after division is obtained, and the improved Fault Quantification Index (IFQI) is used to measure the richness of target information in each enveloped spectrum (ES), generating a two-dimensional diagram. The envelope spectrum with the largest IFQI value is selected as the improved envelope spectrum (IES) obtained by the FSc and SSR division strategy (IESFSc-SSRgram), enabling the fault diagnosis of the axle box bearing. The effectiveness and superiority of the proposed method in identifying multi-source concurrent faults in the wheelset bearing system are verified by comparing it with the traditional method.

关键词： Fault diagnosis correlation Resonant frequency Frequency conversion Wavelet packets Power capacitors Frequency measurement Sensors Indexes Frequency control

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Illumination robust loop closure detection with the constraint of pose

arXiv

引用

arXiv 2019年

作者： Deli, Yan Wenkun, Tuo Weiming, Wang Shaohua, Li State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang050043 China School of Electrical and Electronic Engineering Shijiazhuang Tiedao University Shijiazhuang050043 China School of Electronic and Information Engineering Beijing Jiaotong University Beijing100044 China

Background: Loop closure detection is a crucial part in robot navigation and simultaneous location and mapping (SLAM). Appearance-based loop closure detection still faces many challenges, such as illumination changes, perceptual aliasing and increasing computational complexity. Method: In this paper, we proposed a visual loop-closure detection algorithm which combines illumination robust descriptor DIRD and odometry information. The estimated pose and variance are calculated by the visual inertial odometry (VIO), then the loop closure candidate areas are found based on the distance between images. We use a new distance combing the the Euclidean distance and the Mahalanobis distance and a dynamic threshold to select the loop closure candidate areas. Finally, in loop-closure candidate areas, we do image retrieval with DIRD which is an illumination robust descriptor. Results: The proposed algorithm is evaluated on KITTI_00 and EuRoc datasets. The results show that the loop closure areas could be correctly detected and the time consumption is effectively reduced. We compare it with SeqSLAM algorithm, the proposed algorithm gets better performance on PR-curve. copyright © 2019, The Authors. All rights reserved.

关键词： Mapping

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Response characteristics of a Piezoelectric Semiconductor Layer Under a Rigid Spherical Indenter

SSRN

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SSRN 2024年

作者： Liu, Jinxi Gao, Shijing Ju, chengjian Nie, Guoquan chen, Weiqiu State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang050043 China School of Mechanical Engineering Shijiazhuang Tiedao University Shijiazhuang050043 China Department of Engineering Mechanics Hebei Key Laboratory for Mechanics of Intelligent Materials and Structures Shijiazhuang Tiedao University Shijiazhuang050043 China Key Lab of CAD & CG Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province Department of Engineering Mechanics Zhejiang University Hangzhou310027 China

This paper considers the axisymmetric frictionless indentation responses of a piezoelectric semiconductor (PSc) layer, which is perfectly bonded to a rigid substrate and acted on by a rigid spherical indenter. While both the indenter and the rigid substrate are assumed to be electrically insulating, the interaction of piezoelectricity and semiconducting property of PSc is fully taken into consideration. By the Hankel integral transformation, the indentation problem is reduced to a Fredholm integral equation of the second kind, which is solved numerically. The variations of the indentation force, electric potential and contact radius with the indentation depth are obtained. The effects of the layer thickness, indenter size and semiconducting on the variation relationships are analyzed in detail to achieve a better understanding of the response of the PSc layer under indentation. Furthermore, the theoretical results based on the singular integral equation method are verified by the finite element simulation. © 2024, The Authors. All rights reserved.

关键词： Piezoelectricity

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