Journal of Engineering and Thermal Sciences
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A delay analysis of mass volume train security detection network
Get PDFMass volume train security detection network is a real-time and reliable onboard data communication network based on the train level and vehicle level Ethernet network, which will transmit and send mass volume train status and fault diagnosis information, the event log data, rich audio and video data. The network structure and topology is presented, which include all devices which can attach to the network. Then, a delay model of different network topology is put forward, which indicates that the onboard ring network is superior to the linear network topology. Finally, the analysis is confirmed by simulation results. The results indicated that onboard ring topology network will improve control and network function of train, enhance trains’ service and maintenance efficiency
Stress and vibration of a viscoelastic damping isolator under impact loading
Get PDFThere are different types of isolators which include rubber type, coil spring type, slide and rotating type and there are different types of dampers which include viscous type, oil type, and try friction type. Both isolators and dampers are common used to reduce vibration caused by forging or stamping process. However, a new way to reduce the vibration of the punch press is viscoelastic damping isolator (VDI) which can be widely used in manufacturing, electricity and gas supply, construction, transportation and warehousing, and other industries. This study analyzes a VDI composed by partitions, damping fluid, steel springs and level adjusters. Different numbers of the partitions are welded on upper and lower rectangular steel plates, respectively. Up to 150 tons of weight of the punching machines supported by steel springs which are placed at the edges between the square upper/lower plates. Screw types of level adjusters are placed between lower plate and thick steel base to tune the horizontal level of the isolator. High viscosity damping fluid is filled in the space between interlacing partitions around 60 % of the height of the VDI. Punching induced impact energy is dissipated by shear deformation between the damping fluid and partitions. This study uses 3D graphing software and finite element method (FEM) to investigate the dynamic characteristic of the damping isolator after impacted by the puncher. The normal mode analysis of the VDI is obtained. The isolator is settled within 0.3 seconds after 300.000 N of shock impact and satisfies industrial specification of large punchers with loading frequency of 100 cycles per min
Using Taguchi’s method to minimize cogging force of a PM transverse flux linear motor
Get PDFCogging force accounts for important downsides in several aspects, namely causing the speed ripples, inducing vibrations and noises, and increasing the difficulty of position control. All of these negative affects will become more obvious, particularly under light loads and low speeds. So if the cogging force can be kept as minimal as possible, or even completely disappeared, the operational performance of motors will be improved significantly. As our preliminary study indicates, the magnitude of cogging force is influenced by construction of motors, which govern a number of motor parameters. In this paper, the cogging force of a novel type of permanent magnet excited transverse flux linear synchronous motor will be minimized in two steps. First, theoretical analysis will be employed to obtain the most influential parameter on cogging force. Second, Taguchi’s method including 2D finite element analysis is applied to minimize the cogging force. Analytical and simulation results indicate the usefulness of our approach in practice
Influence of hole-drilling diameter on aluminum alloy residual stress measurement
Get PDFA hole-drilling method and finite element (FEM) numerical simulation are used to estimate the residual stress of aluminum alloy welding joints. In order to study the influence of hole diameter on measurement accuracy, a group of experiments are conducted. Experiment results show that the measuring error can be the minimal when the drilling hole diameter is 4 mm. Residual stress of 2219-T87 aluminum alloy welding joints under this optimal hole diameter are obtained. The distribution of the residual stress from the welding seam to the outward is first tensile stress and then compressive stress. And the maximum residual stress is 123.2 MPa
Research on fault law of rolling bearing under different fault levels and loads with HHT method
Get PDFBearing is one of the most important components of rotating machinery. The vibration signals are generally nonlinear and nonstationary while operating. The failed rolling bearing will damage to the machine, or cause a serious loss of property. There are a lot of methods about fault diagnosis of bearing, such as shock pulse method, resonance demodulation. Especially the HHT (Hilbert-Huang Transform) method with the adaptive advantage has gradually become a very promising method to extract the characteristics of nonlinear, nonstationary signal. In this paper the variant energy method was introduced in HHT to reduce the computation of the decomposed signal, which effectively improved the computation, and then an experimental platform was designed and established. The bearing fault categories can be diagnosed correctly in dealing with the vibration signals using this method and the fault law is discovered that the trend of the vibration signal fault characteristic frequency amplitude changes with the load increasing. The bearing failure mechanism provides beneficial reference for further research of nonlinear signal analysis
Comparison of UAV images processing softwares
Get PDFRecently, the aircrafts tend to be replaced by unmanned, light, simple, aerial vehicles (UAVs), same can be said about the field of aerial photogrammetry. UAV system besides the standard airframe and engine includes main processor board, Inertial Navigation System (INS), Global Positions Systems (GPS), telemetry module. For areal imaging purposes there can be a photo camera mounted too. The images taken by the areal camera can later be processed by software which is specialized for photogrammetry. The project of testing Pix4d Mapper (Switzerland) and PhotoMod (Russia) software programs is described in this paper. Pix4d Mapper is software specialized for UAV images proceedings meanwhile PhotoMod is designed for common photogrammetry proceedings. PhotoMod request some special photogrammetric knowledge from the user. There were 36 images processed producing ortho-mosaic and surface model. The results are further described in the paper
Flutter analysis for wing structure using finite element modeling with equivalent stiffness
Get PDFThe aim of this study is to find a rapid and accurate method for wing flutter prediction in the early stage of aircraft design. A method using the concept of equivalent stiffness is presented for the modal and flutter analysis of a wing. The concept of equivalent stiffness method is that the stringer-stiffened panels in wing structures are replaced by unstiffened panels with the same stiffness, and accordingly the complicacy of the finite element (FE) modeling for wing structures can be reduced substantially. The key of the method is on computation of the stiffness matrices of the unstiffened panels with the equivalent mechanical properties of the stringer-stiffened panels. A regional aircraft wing is used for a case study to verify the accuracy of this method. Both the detailed FE model and the FE model with equivalent stiffness for the wing structure are created and analyzed in MSC.Patran/Nastran. The numbers of elements and degrees of freedom in the FE model with equivalent stiffness are reduced to one-tenth of those in the detailed wing FE model. The complicacy of the detailed FE modeling of the wing structure, such as modeling stringers and handling irregular surface, is avoided in the FE model with equivalent stiffness. The results show that the natural frequencies, mode shapes and flutter speed from the two models are in a good agreement. Satisfactory accuracy and rapid modeling of the FE model with equivalent stiffness make it suitable for wing flutter prediction in conceptual and preliminary aircraft design
A new nonlinear longitudinal vibration model of belt driving system applied in energy saving
Get PDFA belt driving system (BDS) of beam pumping unit is of the following characteristics: 1) energy can flow bidirectional freely; 2) the equivalent rotational inertia is a function of the pulley angle and the stiffness is a function of time. Take account of the above characteristics, a new mathematical model of nonlinear longitudinal vibration is built for BDS. The nonlinear relationship between the equivalent rotational inertia and driven-pulley angle as well as the equivalent stiffness and slipping angle is obtained. Comparing experiment results with simulated results, good agreement is found, which shows the simulation model is feasible. The amplitude-frequency curves are given, which show the jumping phenomenon. In addition, the amplitude-frequency curves are very sensitive to the system parameters, such as Young’s modulus, the preload force, the rotational inertia and load torque. In the details, with increasing Young’s modulus as well as decreasing the preload force, the jumping phenomenon moves the high frequency region, and the amplitude-frequency curves of the system move their mutational direction with load torque increasing. The jumping phenomenon of equivalent stiffness suggests that the jumping phenomenon of steady-state response of the pulley is influenced by the nonlinear dynamic stiffness of the belt. Real application indicates that the system energy consumption is increasing with the preload force decreasing, and it is also increasing with the load torque increasing. Therefore, the simulation analysis of nonlinear longitudinal vibration of BDS plays an important role in understanding the effects of the system parameters on the nonlinear steady-state response and saving energy by parameter optimization in practical application
Human activity recognition: classifier performance evaluation on multiple datasets
Get PDFHuman activity recognition is an active research area with new datasets and new methods of solving the problem emerging every year. In this paper, we focus on evaluating the performance of both classic and less commonly known classifiers with application to three distinct human activity recognition datasets freely available in the UCI Machine Learning Repository. During the research, we placed considerable limitations on how to approach the problem. We decided to test the classifiers on raw, unprocessed data received directly from the sensors and attempt to classify it in every single time-point, thus ignoring potentially beneficial properties of the provided time-series. This approach is beneficial as it alleviates the problem of classifiers having to be fast enough to process data coming from the sensors in real-time. The results show that even under these heavy restrictions, it is possible to achieve classification accuracy of up to 98.16 %. Implicitly, the results also suggest which of the three sensor configurations is the most suitable for this particular setting of the human activity recognition problem
Simulation of the lateral oscillation of rope-guided conveyance based on fluid-structure interaction
Get PDFHow to define the clearance between rope-guided conveyances and shaft wall reasonably has confused peers for more than one hundred years. In this paper, the fluid-structure interaction approach was used to simulate the lateral oscillations of rope-guided conveyances. With Yaoqiao vertical production shaft taken into account to validate this approach, user-defined functions coupled with ANSYS FLUENT were employed to conduct the two-dimensional numerical simulation, and the simulation results show that the lateral aerodynamic buffeting force when two conveyances pass each other is much larger than Coriolis force. What’s more important, with the lateral acceleration, velocity and displacement of the conveyances obtained, the simulation results can explain how the lateral aerodynamic buffeting force to oscillate the conveyance laterally successfully. This approach can be easily extended to three-dimensional simulations, to be more reasonable