Full-face hard rock tunnel boring machines(TBM)are essential equipment in highway and railway tunnel engineering construction.During the tunneling process,TBM have serious vibrations,which can damage some of its key c...Full-face hard rock tunnel boring machines(TBM)are essential equipment in highway and railway tunnel engineering construction.During the tunneling process,TBM have serious vibrations,which can damage some of its key components.The support system,an important part of TBM,is one path through which vibrational energy from the cutter head is transmitted.To reduce the vibration of support systems of TBM during the excavation process,based on the structural features of the support hydraulic system,a nonlinear dynamical model of support hydraulic systems of TBM is established.The influences of the component structure parameters and operating conditions parameters on the stiffness characteristics of the support hydraulic system are analyzed.The analysis results indicate that the static stiffness of the support hydraulic system consists of an increase stage,stable stage and decrease stage.The static stiffness value increases with an increase in the clearances.The pre-compression length of the spring in the relief valve a ects the range of the stable stage of the static stiffness,and it does not a ect the static stiffness value.The dynamic stiffness of the support hydraulic system consists of a U-shape and reverse U-shape.The bottom value of the U-shape increases with the amplitude and frequency of the external force acting on the cylinder body,however,the top value of the reverse U-shape remains constant.This study instructs how to design the support hydraulic system of TBM.展开更多
Talent quality is the lifeline of colleges and universities.Based on employment guidance,this paper establishes a student quality evaluation and control system including knowledge,moral character,and ability,and uses ...Talent quality is the lifeline of colleges and universities.Based on employment guidance,this paper establishes a student quality evaluation and control system including knowledge,moral character,and ability,and uses the Analytic Hierarchy Process(AHP)method to analyze the factors affecting the quality of education in colleges and universities.In addition,some suggestions are provided to improve the quality of students.展开更多
The power density of axial piston pumps can benefit greatly from increased rotational speeds.However,the maximum rotational speed of axial piston machines is limited by the cavitation phenomenon for a given volumetric...The power density of axial piston pumps can benefit greatly from increased rotational speeds.However,the maximum rotational speed of axial piston machines is limited by the cavitation phenomenon for a given volumetric displacement.This paper presents a scaling law derived from an analytical cavitation model to estimate the speed limitations for the same series of axial piston pumps.The cavitation model is experimentally verified using a high-speed axial piston pump,and the scaling law is validated with open specification data in product brochures.Results show that the speed limitation is approximately proportional to the square root of the inlet pressure and inversely proportional to the cube root of volumetric displacement.Furthermore,a characteristic constant is defined based on the presented scaling law.This constant can represent the comprehensive capacity of axial piston pumps free from cavitation.展开更多
基金Supported by National Key R&D Program of China(Grant No.2018YFB1702503)National Program on Key Basic Research Project of China(973 Program,Grant No.2013CB035403)Startup Fund for Youngman Research at SJTU(SFYR at SJTU)
文摘Full-face hard rock tunnel boring machines(TBM)are essential equipment in highway and railway tunnel engineering construction.During the tunneling process,TBM have serious vibrations,which can damage some of its key components.The support system,an important part of TBM,is one path through which vibrational energy from the cutter head is transmitted.To reduce the vibration of support systems of TBM during the excavation process,based on the structural features of the support hydraulic system,a nonlinear dynamical model of support hydraulic systems of TBM is established.The influences of the component structure parameters and operating conditions parameters on the stiffness characteristics of the support hydraulic system are analyzed.The analysis results indicate that the static stiffness of the support hydraulic system consists of an increase stage,stable stage and decrease stage.The static stiffness value increases with an increase in the clearances.The pre-compression length of the spring in the relief valve a ects the range of the stable stage of the static stiffness,and it does not a ect the static stiffness value.The dynamic stiffness of the support hydraulic system consists of a U-shape and reverse U-shape.The bottom value of the U-shape increases with the amplitude and frequency of the external force acting on the cylinder body,however,the top value of the reverse U-shape remains constant.This study instructs how to design the support hydraulic system of TBM.
基金Education Science Planning in Heilongjiang Province“Constructing Index System of Online Teaching Quality Evaluation in Applied Undergraduate Colleges”(GJB1423190)2023 School-Level Teaching Reform Project of Heilongjiang University of Business and Technology“Reform and Practice of Foreign Language Classroom Teaching Mode in Applied Undergraduate Colleges Based on‘MOOC+Flipped Classroom’”(HGSJG2023026)2022 Annual Planning Project of China Association of Private Education“Research on the Innovation Model of Integration of Production and Education for Normal English Majors in Applied Undergraduate Universities”(CANFZG22422)。
文摘Talent quality is the lifeline of colleges and universities.Based on employment guidance,this paper establishes a student quality evaluation and control system including knowledge,moral character,and ability,and uses the Analytic Hierarchy Process(AHP)method to analyze the factors affecting the quality of education in colleges and universities.In addition,some suggestions are provided to improve the quality of students.
基金supported by the China National Postdoctoral Program for Innovative Talents(Grant No.BX20200210)the China Postdoctoral Science Foundation(Grant No.2019M660086)the Common Technology for Equipment Pre-research Project(Grant No.41402050202).
文摘The power density of axial piston pumps can benefit greatly from increased rotational speeds.However,the maximum rotational speed of axial piston machines is limited by the cavitation phenomenon for a given volumetric displacement.This paper presents a scaling law derived from an analytical cavitation model to estimate the speed limitations for the same series of axial piston pumps.The cavitation model is experimentally verified using a high-speed axial piston pump,and the scaling law is validated with open specification data in product brochures.Results show that the speed limitation is approximately proportional to the square root of the inlet pressure and inversely proportional to the cube root of volumetric displacement.Furthermore,a characteristic constant is defined based on the presented scaling law.This constant can represent the comprehensive capacity of axial piston pumps free from cavitation.
