Advances in Mechanical Engineering

Using the concept of overlapping mesh method for reference, a new method called as Overlapping Clouds of Points Method (OCPM) is firstly proposed to simulate unsteady flow with moving boundary problems based on meshless method. Firstly, a set of static background discrete points is generated in the whole calculation zone. Secondly, moving discrete points are created around moving body. According to the initial position of moving object in the flow field, the two sets of discrete points can be overlapped. With the motion of moving objects in the calculation field, moving discrete points around the moving body will inherently move. The exchange of flow field information between static points and moving points is realized by the solution of the clouds of points made up of static and moving discrete points using weighted meshless method nearby overlapping boundary. Four cases including piston problem, NACA0012 airfoil vibration flow around a moving sphere in supersonic and multibody separation are given to verify accuracy and practicability of OCPM. The numerical results agree well with exact solution and experimental results, which shows that the proposed OCPM can be applied to the simulation of unsteady flow problem.

At the request of the Authors, the following article has been retracted.

Yang, Jianwei, Zhao, Chunqing, Zhu, Aihua, Yao, Dechen and Wu, Huijie (2016) The reliability estimation for the braking system of high-speed electric multiple units based on Bayes and GO method Advances in Mechanical Engineering published 21 June 2016. doi: 10.1177/1687814016654825

The authors submitted this article for publication in Advances in Mechanical Engineering on 12 November 2015. After going through peer review, the article was accepted for publication on 6 May 2016 and published online on 21 June 2016 with DOI: 10.1177/1687814016654825.

It has come to the attention of the journal and SAGE Publishing that a similar version of the article has been previously published in another journal.

Yang, Jianwei, Zhao, Chunqing, Zhu, Aihua, Yao, Dechen and Wu, Huijie (2016) Reliability Estimation for the Braking Systems of High-Speed Electric Multiple Units Based on Bayes Inference and the GO Method Journal of Computational and Theoretical Neuroscience 13(2): 1314-1322(9). DOI: http://dx.doi.org/10.1166/jctn.2016.5048

In line with COPE guidance, Advances in Mechanical Engineering and SAGE Publishing have agreed to retract the article at the request of the authors for reasons of redundant publication.

A six-cable driven parallel manipulator and an A-B rotator in the feed support system of the Five-hundred-meter Aperture Spherical radio Telescope (FAST) are adopted for realizing the position and pose of nine feeds. The six-cable driven parallel manipulator is a flexible mechanism, which may not be stably controlled due to a small cable tension. The A-B rotator is a rigid mechanism, and its stability and accuracy can be improved by small pose angle. Based on the different characteristics, a pose planning function is presented. The optimization target of the pose planning function is to get the smallest pose angle of the A-B rotator, and the constraint condition can reflect the controllability of the six-cable driven parallel manipulator. Then, the pose planning realization process of the feed support system is proposed. Based on the pose planning method, optimized pose angles of the feed support system for the nine feeds are obtained, which suggests that the pose angle of the six-cable driven parallel manipulator changes from 0° to 14° and the pose angle of the A-B rotator changes from 0° to 26.4°.

The optimum polishing traces are the double-circle polishing traces with zero-velocity deviation percentage (V_dp = 0%). In 1997, Buzzetti used the relatively high-cost programmable logic controller to control the polishing device having double-circle polishing traces with zero-velocity deviation percentage. In order to reduce the manufacturing cost, link-type and planetary-type polishers are proposed for polishing the optical fiber ferrules. However, they cannot be designed to have the double-circle polishing traces with zero-velocity deviation percentage. This article focuses on the systematic design of polishing device having double-circle polishing traces with zero-velocity deviation percentage (V_dp = 0%). In this article, two design concepts of cam-linkage polishing devices are proposed. Based on the kinematic requirements of double-circle polishing traces, the profiles of X-cam and Y-cam are synthesized. According to the simulation by “Cosmos,” the cam-linkage polishing devices have double-circle polishing traces with zero-velocity deviation percentage. Finally, the corresponding prototype of the second cam-linkage polishing device is manufactured and verifies having double-circle polishing traces with zero-velocity deviation percentage.

A dynamic model of serial robots with multiple clearance joints is developed. The contact phenomenon in the clearance joint is modeled by a continuous dissipative Hertz contact theory, and the friction force is calculated based on the modified Coulomb’s friction law. A neural network method is employed to predict the dynamic response, which avoids the problem in solving the differential algebraic equations. An approximate internal model-based neural control method is proposed to control the undesired effects arising from the joint clearances. The validity of the proposed method is verified by simulation results.

This study analyzes the stress distribution of 3D elastoplastic contact problems by using the FE parametric quadratic programming (PQP) method derived from a 3D FE model based on parametric variational principle (PVP). We numerically analyze a 24-blade compressor by combining centrifugal loading with interference-fit one. To accelerate computation, calculation is simplified by structural modeling via multisubstructuring, aiming to deal with FE-simulated computer aided design (CAD) conveniently. We then analyze the relationships between the maximum residual stresses of the compressor posterior to prestressing and overspeed rpms, and we also study the distribution and magnitude of the contact stresses of the compressor in working conditions after overspeed prestressing. Moreover, we thoroughly discuss the distribution and magnitude of the contact stresses of shaft-shaft sleeve-impeller in working conditions. Relative displacement can be prevented and contact stress can be kept uniform due to the nonuniform initial amount of interference in overspeed prestressing. This paper summarizes the FEM simulation results and provides reference data for improving the design and processing of compressor impellers, indicating that overspeed is indispensable in manufacture.

The aim of this study is to investigate the impact of the bus stop near the signalized intersection on the traffic flow from two aspects, traffic volume and delay. A modified Optimal Velocity model is established to analyze the dynamic traffic flow near a signalized intersection with curbside bus stops, and two cases including bus stops placed upstream and downstream the intersection are simulated to compare the impacts. The influencing factors, including the entering probability and the distance between a bus stop and its neighboring signalized intersection, are considered in this study. The simulation results indicate that the impact of the bus stop on the traffic flow is significant when entering probability is above the critical value, and gradually disappears as the distance increases. With respect to the volume, the downstream bus stop is greatly superior to the upstream one when the distance is less than 70 m, and slightly inferior to the upstream one when the distance ranges from 70 m to 200 m. With regard to the vehicle delay, the upstream bus stop is better than the downstream one. We hope these findings will be helpful to offer scientific guidance for the public transport planning and management.

To carry out state identification and fault diagnosis of mechanical equipment, a new method is proposed for fault diagnosis of mechanical equipment based on the reconstruction of feature vector in the fractional Fourier transform domain. First, the time series of vibration signals are performed by fractional Fourier transform in different orders, according to statistical characteristic in the fractional Fourier transform domain. The kurtosis coefficients are then used for searching the optimal order. Next, taking the normal signal as the tracking target, the difference between the detection signal and the normal signal in fractional Fourier transform domain is calculated in the optimal order, so the normal signal is filtered and the state vector is extracted. The characteristic parameters of the correlation dimension, the zero-order moment, and the kurtosis coefficient are then restructured as a feature vector, and finally, the states are recognized using the k-nearest neighbor cross-validation estimation method. The effect of feature extraction is analyzed by correlation coefficient and diagnostic effect is evaluated using the correct rate of diagnosis. Experiment and analysis illustrates that this proposed target tracking filter fault diagnosis method based on reconstruction of feature vector in fractional Fourier transform domain is simple and intuitive. This method has a favorable feature extraction effect, high accuracy rate of diagnosis, high state recognition efficiency, and good recognition stability, making it a viable option for quantitative real-time state recognition and fault diagnosis of mechanical vibration equipment.

The gaseous low-pressure nanofluid flow of a steady-state two-dimensional laminar forced convection heat transfer in the entrance region of pipes is numerically investigated. Such flows are of interest for many engineering applications like the nuclear reactor and electronic equipment cooling, heat exchangers, and many others. Physical parameters considered in this study are Reynolds number (Re), Prandtl number (Pr), nanosolid particles volume fraction ( ϕ ) , Knudsen number (Kn), and the aspect ratio (AR). These parameters ranges are as follows: 500 ≤ Re ≤ 2000 , 0 . 76 ≤ Pr ≤ 0 . 95 , 0 ≤ ϕ ≤ 0 . 5 , 0 ≤ Kn ≤ 0 . 1 , and 1 ≤ AR ≤ 10 . The outcome of this study shows that by increasing Kn, velocity slip and temperature jump at the solid boundaries increase. In addition, heat transfer is enhanced by dispersing Al₂O₃ nanoparticles in the base low-pressure gaseous flow. Results show that there is no effect of the nanoparticles volume fraction with values below 0.03 on the average Nusselt number. The average Nusselt number increases ( Nu ¯ ) as the value of the nanoparticles volume fraction exceeds 0.03. For instance, at Re = 1000, results show that when dispersing Al₂O₃ nanosolid particles with volume fractions of 0.3 and 0.5; there is an enhancement in the average Nusselt number of 30.35% and 136.74%, respectively, when compared to the case of dispersing Al₂O₃ nanosolid particles of 0.03 volume fraction.. Moreover, it is concluded that the average Nusselt number ( Nu ¯ ) depends directly on Reynolds (Re), Prandtl (Pr) numbers, and the nanoparticles volume fraction ( ϕ ) and inversely on Knudsen number (Kn) and the aspect ratio (AR) for the investigated range of parameters considered in this study. Finally, a correlation of Nusselt number among all the investigated parameters in this study is proposed as Nu ¯ = 0 . 976 A R − 0 . 0536 P r 2 . 39 R e 0 . 22 K n − 0 . 378 ϕ 0 . 07 .

In order to accurately perform fault diagnosis of key rotating machines of rail vehicles, a new method for diagnosis was proposed, based on local mean decomposition—energy moment—directed acyclic graph support vector machine. The vibration signals of rotating machines were decomposed by local mean decomposition to obtain the signal components, and then energy moment is calculated for each state feature component for feature extraction. For state identification, the directed acyclic graph support vector machine is established, multiple classical support vector machine were trained, and then multi-state identification was completed using directed acyclic graph support vector machine. The proposed method was tested on a train rolling bearing. Experimental results show that the method has nearly 95% identification accuracy and verified the feasibility and advantages of this method.

The solution of the energy equation of thermo-elasto-hydrodynamic analysis for bearings by the finite element method usually leads to convergence difficulties due to the presence of convection terms inherited from the Navier–Stokes equations. In this work, the numerical analysis is performed with finite element method universally by adopting the characteristic-based split method to solve the energy equation. Five case studies of fixed pad thrust bearings have been set up with different geometries, loads, and lubricants. The two-dimensional film pressure is obtained by solving the Reynolds equation with pre-defined axial load on the pad. The energy equation of the lubricant film and the heat transfer equation of the bearing pad are handled by characteristic-based split method and conventional finite element method in three-dimensional space, respectively. Hot oil carry-over effect and variable lubricant viscosity are considered in the simulations. The results of the temperature distributions in the lubricant film and the bearing pad are presented. The possible usability of characteristic-based split method for future thermo-elasto-hydrodynamic analysis is discussed.

The lifting and propulsion mechanism of a novel biped robot inspired by the basilisk lizard's water-walking function has been developed. The movement trajectories of the Watt-I planar linkage are brought out by combining the movement equations of the four-bar mechanism and the coordinate transformation equations, which are used to simulate the foot trajectories of the basilisk lizard, and the lifting and propulsion mechanism of the biped robot walking on water is carried out. The links' parameters are optimized by taking the trajectories overlap ratio as the objective function. The prototype of the biped robot walking on water is manufactured by the results of the kinematic analysis on the robot. And the lifting and propulsion force curve on the robot from water is measured. The experiment results show that the lifting and propulsion system can satisfy the function requirement of the biped robot walking on water.

The conception of sealed hard drives with helium gas mixture has been recently suggested over the current hard drives for achieving higher reliability and less position error. Therefore, it is important to understand the effects of different helium gas mixtures on the slider bearing characteristics in the head–disk interface. In this article, the helium/air and helium/argon gas mixtures are applied as the working fluids and their effects on the bearing characteristics are studied using the direct simulation Monte Carlo method. Based on direct simulation Monte Carlo simulations, the physical properties of these gas mixtures such as mean free path and dynamic viscosity are achieved and compared with those obtained from theoretical models. It is observed that both results are comparable. Using these gas mixture properties, the bearing pressure distributions are calculated under different fractions of helium with conventional molecular gas lubrication models. The outcomes reveal that the molecular gas lubrication results could have relatively good agreement with those of direct simulation Monte Carlo simulations, especially for pure air, helium, or argon gas cases. For gas mixtures, the bearing pressures predicted by molecular gas lubrication model are slightly larger than those from direct simulation Monte Carlo simulation.

Nowadays, progressive addition lenses are widely applied to correct people’s vision disorders, but the design and machining of progressive addition lenses are still difficult. Generally, a progressive addition lens has a freeform front surface and a spherical back surface. In this article, the design of the front surface was simplified as a minimization problem of a functional, and the solution was obtained directly using a variational-difference method. After solving this problem, the description of the surface was discussed, and an evaluation method was proposed to analyze the fitting accuracy of Zernike polynomial method and B-spline interpolation method with different degrees. As a result, the progressive addition lens surface was constructed by the method with smaller fitting error. Moreover, a new generation algorithm of entrance parameters for tool path generation was put forward, which can reduce the interpolation error. The experimental results indicate that the design method was feasible and the machined surface quality was satisfactory using the proposed algorithm.

The fast response, high efficiency, and good reliability are very important characteristics to electric vehicles (EVs) dc/dc converters. Two-stage dc-dc converter is a kind of dc-dc topologies that can offer those characteristics to EVs. Presently, nonlinear control is an active area of research in the field of the control algorithm of dc-dc converters. However, very few papers research on two-stage converter for EVs. In this paper, a fixed switching frequency sliding mode (FSFSM) controller and double-integral sliding mode (DISM) controller for two-stage dc-dc converter are proposed. And a conventional linear control (lag) is chosen as the comparison. The performances of the proposed FSFSM controller are compared with those obtained by the lag controller. In consequence, the satisfactory simulation and experiment results show that the FSFSM controller is capable of offering good large-signal operations with fast dynamical responses to the converter. At last, some other simulation results are presented to prove that the DISM controller is a promising method for the converter to eliminate the steady-state error.

A lot of mechanical parts are subject to failure due to the deterioration. Usually the preventive maintenance is taken to ensure the safety and reliability. Therefore, it is very important to study the gradual reliability design of the mechanical part for improving the gradual reliability of the mechanical system under the condition of considering the preventive maintenance. Beta distribution is employed to describe the randomness of the mechanical part state after the preventive maintenance. The deterioration process of the mechanical part is modeled using the nonstationary Gamma process. The gradual reliability model before the first preventive maintenance is proposed according to the gradual failure principle and using the initial state distribution and the properties of Gamma process. Then, the gradual reliability model between any two times of preventive maintenance is also derived. Subsequently, the sensitivity equations of the proposed gradual reliability model to each parameter are given. The application process and practicality of the proposed approach are described by a numerical example. This work solved the problem where the maintenance has not been well considered in the reliability design of the mechanical part and contributed to the theory and method of improving the safety and reliability operation of the mechanical system.

Ambient pressure has a certain inhibiting effect on underwater welding droplet transfer and the stability of welding process. Good droplet transfer of underwater welding plays an important role in improving repairing quality of underwater structures. As an additional droplet separating force, laser provides effective means in improving the welding quality. For quantitative analysis and comparison of laser enhanced effect on droplet transfer, a high-speed camera system to shoot the process of welding droplet transfer was designed and by adopting the frequency domain operation, a filter aiming at image processing of welding droplet was also designed to filter the ambient noise and diffraction fringe. Through edge detection algorithm, edges of droplet images were detected, and the size of droplet was computed accurately with welding wire as the reference. At last, droplets’ statues under different welding parameters were compared. The results show that the clear images of GMAW droplet separated from the noise background can be acquired, which makes the high-precision quantitative analysis of laser enhanced effect possible. All of the results lay a foundation for further test of laser enhanced hyperbaric underwater welding.

The accuracy and real time are crucial in turning intention recognition. Therefore, a hybrid model of Gaussian mixture hidden Markov and generalized growing and pruning algorithm for radial basis function neural network is constructed to recognize driver turning intention real timely. The feature parameters of the driving intention identification are determined using principal component analysis. The turning initial stage is selected for identifying turning intention, thus improving the real time of hybrid model. Using support vector machine model and Gaussian mixture hidden Markov model and Gaussian mixture hidden Markov model/generalized growing and pruning algorithm for radial basis function hybrid model, driver turning intention is identified in normal turning and sharp turning. The results show that Gaussian mixture hidden Markov model/generalized growing and pruning algorithm for radial basis function hybrid model identifies turning intention accurately and more efficiently. The accuracy is as high as 96.88% in the normal turning, which is 24.53% higher than that obtained using the Gaussian mixture hidden Markov model and 25.88% higher than that obtained using the support vector machine. The recognition in the turning initial stage is 1.8 s quicker than that in the turning keeping stage. The identification accuracy and real time of hybrid model are substantially better than those of the Gaussian mixture hidden Markov model and support vector machine, especially in the normal turning. When applied in control systems, this method can improve the safety and comfort of vehicle operation and reduce the burden of drivers.

For the image-guided surgery, the positioning of mobile C-arms is a key technique to take X-ray images in a desired pose for the confirmation of current surgical outcome. Unfortunately, surgeons and patient often suffer the radiation exposure due to the repeated imaging when the X-ray image is of poor quality or not captured at a good projection view. In this paper, a virtual reality (VR) aided positioning method for the mobile C-arm is proposed by the alignment of 3D surface model of region of interest and preoperative anatomy, so that a reference pose of the mobile C-arm with respect to the inside anatomy can be figured out from outside view. It allows a one-time imaging from the outside view to greatly reduce the additional radiation exposure. To control the mobile C-arm to the desired pose, the mobile C-arm is modeled as a robotic arm with a movable base. Experiments were conducted to evaluate the accuracy of appearance model and precision of mobile C-arm positioning. The appearance model was reconstructed with the average error of 2.16 mm. One-time imaging of mobile C-arm was achieved, and new modeling of mobile C-arm with 8 DoFs enlarges the working space in the operating room.