Qifeng Peng’s research while affiliated with Centro Universitario de Ciencias de la Salud and other places

Elevators used in ultra-high buildings are prone to vibrating due to their ultra-long traction ropes, which significantly affects the comfort and safety of high-speed elevators. Therefore, vibration of the elevator has always been a topic of research interest. This paper presents a theoretical model for analyzing the tension–torsion coupling vibration of the time-varying elevator traction system. The constitutive relations with the tension–torsion coupling effect of the wire rope are reduced by analyzing the deformation mechanism of the spiral winding wire rope. Based on Hamilton’s principle, the equations of motion and corresponding boundary conditions for the tension–torsion coupling vibration of the elevator traction system are derived. The Galerkin method is employed to account for the influence of nonlinear boundary conditions and to transform the equations of motion into discrete ones with variable coefficients of time, which are solved using the Newmark-β method. The accuracy of the proposed model is justified by the good agreement between theoretical predictions and experimental results, following which, the influence of the operation status and structural parameters of the elevator traction system on its vibration performance is discussed in detail.

Buried pipelines are prone to deformation under surface displacement, pressure occupation, and/or other actions, resulting in stress concentration. Conducting regular stress detection is an important approach to reducing pipeline accidents. This study performed experiments on measuring the coercivity stress of X80 steel, the most commonly used material for high-pressure large-diameter gas transmission pipelines. The coercivity of the specimen under different stress combinations was measured using the DC-driven coercive force measurement system, and the variation of coercive force with biaxial stress was also analyzed. The modified coercive force-stress expression of the generalized Hooke’s law was proposed; the model for the coercive force-stress relationship of X80 steel under the biaxial stress state was established based on this expression. The study indicates that the coercive force method is reliable for accurately measuring the stress of pipeline steel and evaluating the safety margin of in-service pipelines.

In order to analyze emergency stop vibration of the friction vertical lifting system under different loads, a loading experiment was carried out, and the longitudinal vibration characteristics of the carriage, frame, and steel rope were measured during the emergency braking process of an elevator. Accordingly, it is found that the load mass does not affect the peak deceleration value of the car frame and the wire rope during downwards emergency stop. Then, vertical vibration is explored using the time-varying vibration analysis theory. The obtained results show that when analyzing the vibration of objects on both sides of the traction wheel, the deceleration of the wire rope on both sides of the traction wheel are not equal, and the influence of the pressure change during the traction-wheel friction should be considered in calculations. This article may provide a reference to calculate the steel rope tension of the elevator and mine hoist.

An elevator traction system is simplified as a damped vibration system. In order to study the damping characteristics of an elevator traction system, this paper tests the vibration characteristics of a car frame on an in-service elevator with a traction ratio of 2:1. The results show that the natural frequency and stiffness of the system decrease with the increase of the elevator load; the attenuation coefficient and damping increase with the increase of the elevator load; Furthermore, the damping of the traction system is related to the initial running direction. Under the same load, the damping value of downward is greater than that of upward. This research establishes the relationship between vibration parameters, load and elevator running direction and provides an approach to solve the problem of quantitative measurement of damping in the process of elevator operation. Results from this study can provide reference for elevator vibration analysis.

The free vibration control differential equation of shallow spherical shell on two-parameter foundation is a four order differential equation. Using the intermediate variable, the four order differential equation is reduced to two lower order differential equations. The first lower order differential equation is a Helmholtz equation. A new method of two-dimensional Helmholtz operator is proposed as shown in the paper in which the Bessel function included in Helmholtz equation needs to be treated appropriately to eliminate singularity. The first lower order differential equation is transformed into the integral equation using the proposed method in the paper. The second lower order differential equation which is a Laplace equation is transformed into the integral equation by existing methods. Then the two integral equations are discretized according to the middle rectangle formula, and the corresponding solutions can be obtained by MATLAB programming. In this paper, the R-function theory is used to select the appropriate boundary equation to eliminate the singularity. Based on the properties of R-function, the combined method of Helmholtz equation and Laplace equation can solve the free vibration problem of irregular shallow spherical shell on two-parameter foundation. Five examples are given to verify the feasibility of the method.

An elevator is a typical flexible lifting machine. In order to monitor the vibration of elevator structure, the vibration characteristics of an elevator with a traction ratio of 1:1 has been tested experimentally. Sensors were arranged on the platform frame, car roof, and hoist rope to test the vibrations of the elevator in both ascending and descending conditions. The transverse, longitudinal, and coupled transverse-longitudinal vibrations were compared and analyzed. Further, the short-time Fourier transform (STFT) method was used to examine the power spectral density (PSD) of the test results, and the main frequency distribution and influencing factors of the vibration of elevator components were investigated. The results revealed that the transverse and longitudinal vibrations of the platform frame were low-frequency vibrations, which was attributed to the elastic interaction between the platform frame and the car frame. The form and amplitude of longitudinal vibration of the car frame were basically consistent with those of the platform frame, but PSD of the transverse vibration had an obvious peak in the high-frequency region. The transverse and longitudinal vibration frequencies of the hoist rope were higher. Furthermore, the peak PSD value of transverse vibration of the hoist rope was 421 times larger than that of the car frame, so a small disturbance at the end of the rope could lead to a huge disturbance in the center of the rope. Overall, this study provides useful insights on designing an elevator monitoring sensor and relevant data processing.

In order to study the relationship between the braking distance and the load of escalator and realize the prediction of the rated load braking distance with a little load, the method of combining theoretical analysis and experimental research is used. First, the dynamic characteristics of the escalator during emergency braking are analyzed, and the prediction model of the braking distance of the escalator under different loads is derived based on the law of conservation of energy. Furthermore, the influence coefficients under different loads were determined through experimental studies, the model was revised, and the concept of equivalent no-load kinetic energy (ENKE) was proposed. The research shows that the braking distance of the escalator increases nonlinearly with the increase in load. When the no-load braking distance and the 25% rated load braking distance change greatly, the braking distance increases faster as the load increases; the escalators with large brake force have a small ENKE and are easy to stop. Otherwise, it is difficult to stop. The test results show that the comparison between the predicted value of the prediction model and the measured value has a maximum error of 2.7%, and the maximum error at rated load is only 2.0%, which fully meets the needs of engineering measurement. And the prediction method reduces test costs, enhances test security, and improves test coverage.

The governing equation of the bending problem of simply supported thin plate on Pasternak foundation is degraded into two coupled lower order differential equations using the intermediate variable, which are a Helmholtz equation and a Laplace equation. A new solution of two-dimensional Helmholtz operator is proposed as shown in Appendix 1. The R-function and basic solutions of two-dimensional Helmholtz operator and Laplace operator are used to construct the corresponding quasi-Green function. The quasi-Green’s functions satisfy the homogeneous boundary conditions of the problem. The Helmholtz equation and Laplace equation are transformed into integral equations applying corresponding Green’s formula, the fundamental solution of the operator, and the boundary condition. A new boundary normalization equation is constructed to ensure the continuity of the integral kernels. The integral equations are discretized into the nonhomogeneous linear algebraic equations to proceed with numerical computing. Some numerical examples are given to verify the validity of the proposed method in calculating the problem with simple boundary conditions and polygonal boundary conditions. The required results are obtained through MATLAB programming. The convergence of the method is discussed. The comparison with the analytic solution shows a good agreement, and it demonstrates the feasibility and efficiency of the method in this article.

In order to study the dynamic characteristics of the elevator, the response characteristics of the elevator under normal operation and emergency braking conditions are analyzed. In this paper, the centralized mass discretization model is used to study the vibration characteristics of the elevator traction system under the external excitation. Firstly, the vibration equation of the elevator multi-degrees-of-freedom (abbreviated as DOF) system is established. Then, the vibration characteristics of the three DOF system are analyzed, and the natural frequencies and modes are obtained. The free vibration equation and forced vibration equation are obtained, and the theoretical solutions are obtained. Finally, the test method proposed in this paper is used to test the normal operation and emergency braking of the elevator. The test results show that, under normal operation conditions, the measured speed and distance errors are not more than 4.2%, the up running distance measured by the elevator is larger than the actual value, while the down running distance is smaller than the actual value; under emergency braking condition, because the steel wire rope can only bear the pulling force, the peak acceleration fluctuation in the up emergency braking process is large, while the down emergency braking acceleration fluctuation is small. Therefore, the elevator vibration analysis model and the vibration test method proposed in this paper can be used for the analysis of elevator dynamic performance, which has great reference value for the safety performance research of the elevator traction system.

The governing differential equations of the bending problem of simply supported shallow spherical shells on Winkler foundation are simplified to an independent equation of radial deflection. The independent equation of radial deflection is decomposed to two Laplace operators by intermediate variable. The R-function theory is applied to describe a shallow spherical shell on Winkler foundation with concave boundary, and then a quasi-Green’s function is established by using the fundamental solution and the normalized boundary equation. The quasi-Green’s function satisfies the homogeneous boundary condition of the problem. The Laplace operators of the problem are reduced to two simultaneous Fredholm integral equations of the second kind by the Green’s formula. The singularity of the kernel of the integral equation is eliminated by choosing a suitable form of the normalized boundary equation. The integral equations are discretized into the homogeneous linear algebraic equations to proceed numerical computing. The singular term in the discrete equation is eliminated by the integral method. Some numerical examples are given to verify the validity of the proposed method in calculating simple boundary conditions and polygonal boundary conditions. A comparison with the ANSYS finite element (FEM) solution shows a good agreement, and it demonstrates the feasibility and efficiency of the present method.