Journal of Engineering and Thermal Sciences
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Dynamical processes in a multi-motor gear drive of heavy slabbing mill
Get PDFA real case study is represented of abrupt failures in a new multi-motor gear drive of vertical rolls in the heavy slabbing mill. Modal analysis is conducted, and the lowest torsional vibration modes are verified by the data from an industrial plant. Conditions of parametric resonances due to variable stiffness of teeth are determined within the range of working speed. The branched gear drive is investigated by the non-linear dynamical model with backlashes. It is shown that instantaneous dynamic loads in driveline are strongly dependent on the difference in gap sizes and phase shift between two intermediate gears in the output gear wheel coupling. Deviation in electrical parameters by 0.5 % is considered as the additional cause of not equal load sharing of parallel motors. Results of this research allowed preventing further failures of the gearbox and optimizing slabbing mill control. The proposed approach can be used in other multi-motor machines
Feasibility study on the application of carbon dioxide phase change fracturing technology in a foundation pit of an open cut tunnel
Get PDFCarbon dioxide phase change fracturing technology is a brand-new and efficient cracking and tunneling technology. Because the method utilizes the change of carbon dioxide state, it belongs to a pure physical process. By adjusting the release rate of gaseous substances, it can effectively control the pressure of the gas, and achieve micro vibration, zero flying stone, zero toxic gas emission, and no micro harmful effect of shock wave, but the application of carbon dioxide phase change cracking technology in urban foundation pit excavation is less. In this paper, through the analysis of three different cracking parameters of urban foundation pit excavation process, it is found that when the diameter of the cracked pipe is 85 mm, the construction safety can be guaranteed. In addition, according to the on-site cracking effect, the carbon dioxide phase change cracking technology is a safe, reliable, relatively economical and efficient excavation technology under urban complex environmental conditions, and will not affect the surrounding environment during use, but Its cracking efficiency has a great relationship with the air surface
Numerical simulation and experimental analysis of magneto-mechanical behavior of anti-seismic active sandwich structure
Get PDFThis work focuses on the quasi-static behavior study for simply supported sandwich beams with aluminum faces and magnetorheological elastomer core subjected to three points bending subjected to a magneto-mechanical loading by numerical and experimental investigations. The mechanical properties of the magnetorheological elastomer core are measured experimentally and the mechanical behavior of the MRE was identified by the generalized Maxwell rheological model. Depending upon the adjustable properties of the beam, energy dissipation is by core shear. A systematic series of experiments and finite elements simulations have been performed in order to assess the static behavior of the beam. The results obtained show a significant influence of the magnetic field intensity on the flexural displacement of the beam
Damage identification research on beam structures by integrating multiple modal parameters
Get PDFA new damage identification method with a fusion index to locate the damage position and identify the damage extent of beam structures is presented by integrating the modal strain energy and natural frequency sensitivity. The modal strain energy, which is with the limitation on obtaining the damage extent, is adopted to locate the damage position with avoiding the interference of structure itself. The natural frequency sensitivity, which is with false detection and interference happening when solely used, is adopted for identifying the damage extent. In order to further improve the precision of the damage quantification, additional masses are added on the beam structure to obtain more information about the natural frequency sensitivity. Then, the fusion index for damage identification is established through combining the modal strain energy and the natural frequency sensitivity before and after adding masses on beam structures. The results obtained by finite element analysis and experimental tests show that the presented method can locate and quantify damages on beam structures in an accurate and convenient way
Simulation analysis and experimental verification on body-in-white static stiffness of a certain commercial vehicle
Get PDFThe body-in-white simulation model of a certain commercial vehicle was established to make a numerical analysis of the vehicle body static stiffness in this research. Meanwhile, the effectiveness of the simulation model was verified using the physical test of body-in-white static stiffness. Research results showed that the error of body-in-white static stiffness test and simulation analysis was within the range of ±10 %, which could reduce the test cost and guarantee the test precision. The research findings do provide a better application value and references for vehicle engineering developers
Fine-grained fault recognition method for shaft orbit of rotary machine based on convolutional neural network
Get PDFIn the fault diagnosis of the shaft orbit of rotating machinery, there are few prejudgments about the severity of the faults, which is very important for fault repair. Therefore, a fine-grained recognition method is proposed to detect different severity faults by shaft orbit. Since different shaft orbits represent different type and different severity of faults, the convolutional neural network (CNN) is applied for identifying the shaft orbits to recognize the type and severity of the fault. The recognition rate of proposed fine-grained fault identification method is 97.96 % on the simulated shaft orbit database, and it takes only 0.31 milliseconds for the recognition of single sample. Experimental result indicated that the classification performance of the proposed method are better than the traditional machine learning models. Moreover, the method is applied for the identification of the measured shaft orbits of rotor with different degree of imbalance faults, and the testing accuracy of the experiments in measured shaft orbits is 97.14 %, which has verified the effectiveness of the proposed fine-grained fault recognition method
A novel faults detection method for rolling bearing based on RCMDE and ISVM
Get PDFThe rolling bearing is an essential element widely used in the rotating machinery. Bearing failures are among the main reasons for breakdown of rotating machinery. Therefore, fault detection of bearing is necessary to reduce the probability of breakdown and safety accidents. A novel fault diagnosis method for rolling bearing based on Refined Composite Multiscale Dispersion Entropy (RCMDE) and Improved Support Vector Machine (ISVM) is presented in this paper. The RCMDE is a new irregular index in biomedical signal analysis, which has lower computational cost and more stable results. Therefore, the RCMDE is introduced as fault feature to represent the bearing fault characteristics. After feature extraction, an improved support vector machine based on whale optimization algorithm (WOA) and support vector machine (SVM) is proposed as a fault classifier, which has the advantages of less training samples and good classification effect. The effectiveness of the proposed method in bearing fault diagnosis is verified by using bearing fault experimental data
Movable short-circuit technique to extract the relative permittivity of materials from a coaxial cell
Get PDFIn recent years, industrial applications have been based on the use of intrinsic material properties that improve designs, processes, qualities and product controls. To get to those intrinsic parameters, various appropriate techniques are required. In this paper, a new technique has been developed and presented. It essentially puts the emphasis on the dielectric relative permittivity extraction from the principle of a movable short-circuit through the coaxial transmission-line cell. This technique is aimed at drastically reducing the discontinuity impacts at the interface feed line (connector) and ideal line, solving the phase constant frequency limit, stopping the constraints bound to the higher mode propagations and improving the accuracy level when the frequency range has increased. The technique is based on the use of the sum of two different lengths of the cell by removing the first value of the phase constant in the frequency range of interest when it is negative. This new technique can be easily implemented; its focus is not on iterative principles, but on the use of the constant propagation of a Quasi-TEM mode of the transmission-line. The bio-food industry (semolina), environmental field (palm tree) and building trade (aquarium sand) were used to test the validity of the technique in 2-20 GHz
Bearing type influence on vibration activity at coasting of bent double-span rotor with skew-symmetric residual unbalance
Get PDFThe paper is dedicated to study the dependence of vibration activity at coasting of high-temperature segment of turbine unit (TU), which includes high pressure and medium-low pressure rotors (HPR-MLPR system) with skew-symmetric residual unbalance of each rotor, from frequently used types of bearings. Six-block segmental and elliptical bearings are considered. The study takes into account the presence of unrecoverable initial deflection of the shaft. Calculations are performed for turbine model K-300-23.5. Detailed analysis of results is performed
