A new measuring method──relative revolution principle,is introduced in dealing with friction moment measurement of a counter. The instrument manufactured based on this principle is efficient, accurate, and easy to o...A new measuring method──relative revolution principle,is introduced in dealing with friction moment measurement of a counter. The instrument manufactured based on this principle is efficient, accurate, and easy to operate, and a continuous dynamic measurement of an absolute friction moment is achieved intelligently. The principle is suitable to the measurement of friction moments of many kinds of elements and some special characteristics, and is of good engineering significance.展开更多
This study investigates the efficiency of two types of rehabilitation methods based on economic justification that can lead to logical decision making between the retrofitting schemes. Among various rehabilitation met...This study investigates the efficiency of two types of rehabilitation methods based on economic justification that can lead to logical decision making between the retrofitting schemes. Among various rehabilitation methods, concentric chevron bracing（CCB） and cylindrical friction damper（CFD） were selected. The performance assessment procedure of the frames is divided into two distinct phases. First, the limit state probabilities of the structures before and after rehabilitation are investigated. In the second phase, the seismic risk of structures in terms of life safety and financial losses（decision variables） using the recently published FEMA P58 methodology is evaluated. The results show that the proposed retrofitting methods improve the serviceability and life safety performance levels of steel and RC structures at different rates when subjected to earthquake loads. Moreover, these procedures reveal that financial losses are greatly decreased, and were more tangible by the application of CFD rather than using CCB. Although using both retrofitting methods reduced damage state probabilities, incorporation of a site-specific seismic hazard curve to evaluate mean annual occurrence frequency at the collapse prevention limit state caused unexpected results to be obtained. Contrary to CFD, the collapse probability of the structures retrofitted with CCB increased when compared with the primary structures.展开更多
A compound pendulum based measurement method is put forward and the relevant equipment is designed. By using the variation of angle with the time acquired by an angular displacement sensor, the moment of inertia is ob...A compound pendulum based measurement method is put forward and the relevant equipment is designed. By using the variation of angle with the time acquired by an angular displacement sensor, the moment of inertia is obtained through the numerical solution of certain equations, which are deduced from the phase-plane analysis of compound pendulum. The influences of both friction and air resistance on the compound pendulum are already taken into consideration without estimating and measuring the resistances in advance. With this method, the to-be-measured object can be positioned and fixed easily and safely. Numerical simulations show a favorable precision of this method.展开更多
In this paper,we give a brief introduction to the proposal and development history of the earthquake magnitude concept. Moment magnitude MWis the best physical quantity for measuring earthquakes. Compared with other m...In this paper,we give a brief introduction to the proposal and development history of the earthquake magnitude concept. Moment magnitude MWis the best physical quantity for measuring earthquakes. Compared with other magnitude scales used traditionally,moment magnitude is not saturated for all earthquakes,regardless of big and small earthquakes,deep and shallow earthquakes,far field and near field seismic data,geodetic and geological data,moment magnitude can be measured,and can be connected with wellknown magnitude scales such as surface wave magnitude MS. Moment magnitude is a uniform magnitude scale,which is suitable for statistics with wide magnitude range.Moment magnitude is the preferred magnitude selected by the International Seismological community,and it is preferred by the departments responsible for publishing seismic information to the public. Moment magnitude is a uniform magnitude scale,which is suitable for statistics with wide magnitude range. Moment magnitude is a preferred magnitude for international seismology,it is preferred by the agency responsible for providing information about earthquakes to the public. We provide all formulas used in the calculation of moment magnitude,and the calculation steps in detail. We also analyzed some problems and rules to solve these problems by using different formulas and numerical value calculation steps.展开更多
Tapered roller bearings(TRBs) can withstand axial loads, radial loads, and overturning moments. The performance, safety, and efficiency of rotating machinery are directly influenced by the friction moments within the ...Tapered roller bearings(TRBs) can withstand axial loads, radial loads, and overturning moments. The performance, safety, and efficiency of rotating machinery are directly influenced by the friction moments within the TRBs. However, most current research has relied on empirical formulas that focus on axial loads. Additionally, the friction coefficient between the rollers and the inner ring rib has been defined using simple empirical methods. In actual applications, the loads on TRBs are not purely axial or radial, and simple empirical friction coefficients do not adequately account for the varying lubrication conditions. To address this challenge, this study proposes an improved method for calculating the friction moments of TRB under combined axial and radial loads. This study employs a calculation method for sliding friction coefficients that can model dry, boundary, elastohydrodynamic, and mixed lubrication conditions. To demonstrate the advantages of the proposed method, the friction moments obtained using the existing and proposed methods are compared. Additionally, the influence of TRB structural parameters on the friction moment is discussed. An experimental study is conducted to validate the effectiveness of the proposed method. The findings provide valuable insights for designing TRB structural parameters to minimize friction moments.展开更多
文摘A new measuring method──relative revolution principle,is introduced in dealing with friction moment measurement of a counter. The instrument manufactured based on this principle is efficient, accurate, and easy to operate, and a continuous dynamic measurement of an absolute friction moment is achieved intelligently. The principle is suitable to the measurement of friction moments of many kinds of elements and some special characteristics, and is of good engineering significance.
文摘This study investigates the efficiency of two types of rehabilitation methods based on economic justification that can lead to logical decision making between the retrofitting schemes. Among various rehabilitation methods, concentric chevron bracing（CCB） and cylindrical friction damper（CFD） were selected. The performance assessment procedure of the frames is divided into two distinct phases. First, the limit state probabilities of the structures before and after rehabilitation are investigated. In the second phase, the seismic risk of structures in terms of life safety and financial losses（decision variables） using the recently published FEMA P58 methodology is evaluated. The results show that the proposed retrofitting methods improve the serviceability and life safety performance levels of steel and RC structures at different rates when subjected to earthquake loads. Moreover, these procedures reveal that financial losses are greatly decreased, and were more tangible by the application of CFD rather than using CCB. Although using both retrofitting methods reduced damage state probabilities, incorporation of a site-specific seismic hazard curve to evaluate mean annual occurrence frequency at the collapse prevention limit state caused unexpected results to be obtained. Contrary to CFD, the collapse probability of the structures retrofitted with CCB increased when compared with the primary structures.
文摘A compound pendulum based measurement method is put forward and the relevant equipment is designed. By using the variation of angle with the time acquired by an angular displacement sensor, the moment of inertia is obtained through the numerical solution of certain equations, which are deduced from the phase-plane analysis of compound pendulum. The influences of both friction and air resistance on the compound pendulum are already taken into consideration without estimating and measuring the resistances in advance. With this method, the to-be-measured object can be positioned and fixed easily and safely. Numerical simulations show a favorable precision of this method.
基金the Monitoring Task of Department of Earthquake Monitoring and Prediction,China Earthquake Administration(2018)Technical Support and Effect Analysis of New Magnitude National Standard Implementation.
文摘In this paper,we give a brief introduction to the proposal and development history of the earthquake magnitude concept. Moment magnitude MWis the best physical quantity for measuring earthquakes. Compared with other magnitude scales used traditionally,moment magnitude is not saturated for all earthquakes,regardless of big and small earthquakes,deep and shallow earthquakes,far field and near field seismic data,geodetic and geological data,moment magnitude can be measured,and can be connected with wellknown magnitude scales such as surface wave magnitude MS. Moment magnitude is a uniform magnitude scale,which is suitable for statistics with wide magnitude range.Moment magnitude is the preferred magnitude selected by the International Seismological community,and it is preferred by the departments responsible for publishing seismic information to the public. Moment magnitude is a uniform magnitude scale,which is suitable for statistics with wide magnitude range. Moment magnitude is a preferred magnitude for international seismology,it is preferred by the agency responsible for providing information about earthquakes to the public. We provide all formulas used in the calculation of moment magnitude,and the calculation steps in detail. We also analyzed some problems and rules to solve these problems by using different formulas and numerical value calculation steps.
基金supported by the National Natural Science Foundation of China (Grant No. 52175120)the Science Center for Gas Turbine Project(Grant No. 2022-B-III-003)the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University。
文摘Tapered roller bearings(TRBs) can withstand axial loads, radial loads, and overturning moments. The performance, safety, and efficiency of rotating machinery are directly influenced by the friction moments within the TRBs. However, most current research has relied on empirical formulas that focus on axial loads. Additionally, the friction coefficient between the rollers and the inner ring rib has been defined using simple empirical methods. In actual applications, the loads on TRBs are not purely axial or radial, and simple empirical friction coefficients do not adequately account for the varying lubrication conditions. To address this challenge, this study proposes an improved method for calculating the friction moments of TRB under combined axial and radial loads. This study employs a calculation method for sliding friction coefficients that can model dry, boundary, elastohydrodynamic, and mixed lubrication conditions. To demonstrate the advantages of the proposed method, the friction moments obtained using the existing and proposed methods are compared. Additionally, the influence of TRB structural parameters on the friction moment is discussed. An experimental study is conducted to validate the effectiveness of the proposed method. The findings provide valuable insights for designing TRB structural parameters to minimize friction moments.
