Jaw Functional Orthopedics and Cranoficial Growth
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Dynamic modeling and analysis of elastic isolation damping gears
No full textTransmission error is the main excitation source of gear vibration and noise, how to reduce the transmission error has always been the focus of the research on gear dynamics. In this study, a new type of cylindrical spur gear with elastic isolation is developed for the reduction of transmission error. The elastic isolation damping gear includes three parts: the gear body, the elastic isolation layer, and the involute profile body. Dynamic models are established with the elastic isolation damping gear using lumped parameter method. Dynamic characteristics are simulated via spur gear pair examples by the Runge-Kutta algorithm. By comparing the simulation results of three gear models, the dynamic response of the elastic isolation damping gear with sliding friction is illustrated. The influence of different parameters of the elastic isolation layer on the dynamic response for the elastic isolation damping gear model is carried out. The results indicate that the proposed elastic isolation damping gear model is effective in reducing dynamic transmission error, especially for torque fluctuation, high-speed and heavy-duty conditions. Parameter influence analysis guides the design of elastic isolation damping gears with low transmission error
A study of numerical simulation on extreme flexural stress of ice plate
No full textIce plate is general construction component in the cold region and the flexural stress governs its failure pattern. As per the stress equations which were proposed by Westgaard and Masterson, they explained the generic empirical methods to evaluate the extreme and effective flexural stress of ice plate. Based on these equations, most of consequent experiments and simulations referred them directly. Despite of this, there are not any demonstrations about the limitations of these equations by numerical modeling, therefore, it is possible to find the differences between the simulation values and theoretical calculation values by the deployment of numerical simulations from ‘Finite Element Analysis’ perspective, and based on these comparisons, author proposed some assumptions about the limitations of these equations. In the meantime, the simulation process can enhance the understanding of the applications of these equations
Traveling wave effect of multi-span through concrete-filled steel tubular arch bridge
No full textTo explore the different influence of traveling wave effect on the isolated and non-isolated arch bridge, the isolated and non-isolated multi-span arch bridges models are established respectively, three measured seismic waves were selected, and under the eight kinds of apparent wave velocities and multi-point consistent excitations, the structural responses of the two models, including the internal force response, the arch rib velocity, the pier’s internal force response, the bridge deck acceleration, and the shear force and displacement of isolation support of different arch ribs position in two models, were compared and analyzed. The results show that the isolation effect of the isolation structure is obvious; the wave effect of the isolated structure is significant, the two structures show different internal force response curves in different positions of the arch ribs under the influence of different seismic waves; the influence of the apparent wave velocity on the force and shock reduction rate of the arch ribs is complex; the vertical acceleration of the arch ribs and bridge deck of the isolated structure is reduced significantly; and the shear force and displacement of the isolation bearing increase with the increase of the apparent wave velocity. The study shows the traveling wave effect of multi-span through a concrete-filled steel tubular arch bridge with and without isolation, and the results will be used for the seismic design and analysis of structural diseases caused by the wave effect
An on-line monitoring method for the flow excitation in francis hydraulic turbine based on dynamics
No full textDuring the operation of hydraulic turbine, the vibration often exceeds the standard due to flow excitation, which affects the safe and stable operation of the hydraulic turbine. In this paper, an on-line monitoring method for the flow excitation in Francis hydraulic turbine is proposed based on the dynamic characteristics of Francis hydraulic turbine. Firstly, based on the flow excitation characteristics in Francis hydraulic turbine and the dynamic equation of main shaft system, the internal relationships between the dynamic response of turbine bearing and the flow excitation in the Francis hydraulic turbine are clarified. Secondly, according to these relationships, a method based on wavelet transform (WT), particle swarm optimization (PSO), and variational mode decomposition (VMD) is proposed for extracting the flow excitation features in Francis hydraulic turbine. Then, by this method, the flow excitation features are acquired. Based on the obtained flow excitation features, the flow excitation can be monitored on-line. Finally, the proposed on-line monitoring method for the flow excitation in Francis hydraulic turbine is verified by experiments. Based on the results, the flow excitation components in the signal extracted by this method are about 35 % more than those extracted by the previous methods. The results show that the on-line monitoring method proposed in this paper is convenient and effective
Utilization of low-potential secondary energy resources at oil pumping station
No full textThe article considers the sources of low-potential heat at oil pumping station, estimates the amount of heat of technological processes that is irretrievably lost in the environment from the oil ACD, cooling systems of electric motors and wastewater treatment plants, and also presents possible ways of utilization and useful use of this heat using heat pumps
Indoor and outdoor multi-source 3D data fusion method for ancient buildings
No full textAncient buildings carry important information, such as ancient politics, economy, culture, customs. However, with the course of time, ancient buildings are often damaged to different degrees, so the restoration of ancient buildings is of great importance from the historical point of view. There are three commonly used non-contact measurement methods, including UAV-based oblique photogrammetry, terrestrial laser scanning, and close-range photogrammetry. These methods can provide integrated three-dimensional surveys of open spaces, indoor and outdoor surfaces for ancient buildings. Theoretically, the combined use of the three measurement methods can provide 3D (three-dimensional) data support for the protection and repair of ancient buildings. However, data from the three methods need to be fused urgently, because if the image data is not used, it will lead to a lack of real and intuitive texture information, and if only image matching point clouds are used, their accuracy will be lower than that of terrestrial laser scanning point clouds, and it will also lead to a lack of digital expression for components with high indoor historical value of ancient buildings. Therefore, in this paper, a data fusion method is proposed to achieve multi-source and multi-scale 3D data fusion of indoor and outdoor surfaces. It takes the terrestrial laser point cloud as the core, and based on fine component texture features and building outline features, respectively, the ground close-range image matching point cloud and UAV oblique image matching point cloud are registered with the terrestrial laser point cloud. This method unifies the data from three measurements in the point cloud and realizes the high-precision fusion of these three data. Based on the indoor and outdoor 3D full-element point cloud formed by the proposed method, it will constitute a visual point cloud model in producing plans, elevations, sections, orthophotos, and other elements for the study of ancient buildings
Effect of damping ditch on blasting vibration reduction by field experiment and numerical simulation
No full textIn order to analyze the influence of a damping ditch on the blasting vibration, a large number of on-site monitoring tests with or without damping ditch were carried out based on the foundation pit excavation project. Based on the Sadovsky’s empirical formula, the optimized vibration velocity attenuation model was established by using the waveform subsection correspondence method and least square method. The calculation results are in good agreement with the measurement results. The average errors in radial direction and vertical direction are 17.04 % and 10.76 % respectively. A series of finite element models were established to study the influence of the damping ditch geometry on the damping effect. The experimental and numerical results show that the damping ditch can obviously reduce the blasting seismic effect, with the highest damping ratio in the area near blasting source. For different damping ditches, the damping ratio first increases and then decreases proportionally to the increase of distance between the measuring point and the blasting zone. The damping ditch depth has the best damping effect on blasting vibration, followed by the distance between the damping ditch and the blasting source, and finally the damping ditch width, which is consistent with the damping mechanism of theoretical analysis. The attenuation of the surface wave is only related to the damping ditch depth. The research results can provide a reference for the design of blasting vibration isolation
Comprehensive sensitivity analysis on static and dynamic reservoir parameters impacting near wellbore injectivity during CO2 sequestration
Get PDFCarbon capture and storage (CCS) is proved to be effective measure for reducing CO2 emissions. whilst the world still highly depends on the use of fossil fuel energy, this method is necessary for reaching the world’s 1.5 °C goal. In CCS, CO2 is hindered from entering the atmosphere by capturing it from sources of emission and storing it in geological formation. Saline aquifers among all possible underground formations are most common targeted ones for CO2 storage due to their frequent presence, and large storage capacity. However, this storage option suffers from sufficient well injectivity to inject large volumes of CO2 at acceptable rates through a minimum number of wells. The injectivity impairment / reinforcement happens through mineral dissolution, fine particle movement, salt precipitation and hydrate formation (known so far). Each of these mechanisms will be more dominant in injectivity alteration at different distance from the injection point depending on reservoir pressure and temperature, formation water salinity, rock mineralogy, and flow rate of CO2 injection as well as its dryness. Incorporating all the finding into radial flow near wellbore will help gaining insight into the resultant of injectivity changes over time and distant from injection point. In this study we have chosen Eclipse 300 together with an open-source code to investigate the impact of formation characteristics, CO2 -Brine-Rock interaction, pressure, temperature as well as injection rate on injectivity alteration. The goal for this work is to provide a workflow which can help predicting injectivity alteration using the existing tools. Simulation results show that the high homogenous horizontal permeability in combination with vertical flow baffles in the formation (among all other parameters) has positive impact on storage capacity by increasing residual trapping. However, permeability is affected severely by salt precipitation during CO2 injection. Combined static and dynamic parameter study demonstrate that the injection rate plays a crucial role in size and expansion of CO2 plume as well as growth rate of dry out zone length, amount of salt precipitation and length of equilibrium region. The higher the injection rate, the quicker activation of the capillary and gravity force which leads to drag more brine to near well-bore resulting in higher volume fraction of salt precipitation. However, low injection rate could result in smaller CO2 plume, shorter dry out zone and longer equilibrium region in term of distance from injection point
Simulation analysis on seismic dynamic response of pile supported tunnels in deep backfill area of soil-rock mixture
Get PDFTo reveal the seismic dynamic response of the pile-supported tunnel group in the soil-rock mixture deep backfill region, a three-dimensional finite element model was established based on the engineering conditions of the subway section and three tunnels with close access lines. Subsequently, the seismic dynamic response of the tunnel lining structure was studied. The results show that: Under the action of seismic, the soil-rock mixture stratum presents nonlinear characteristics with shear failure and plastic deformation. In addition, the acceleration and earth pressure of the soil-rock mixture stratum is in a “saturated” state; The seismic dynamic response of the three tunnels influences each other. The bending moments in the X and Y directions of the tunnel lining cross-section are distributed in “X” and inverted “V” shapes, respectively. Meanwhile, the tensile stress and shear stress are distributed in an “X” shape; Under the action of seismic, the main failure form of tunnel lining is tension shear failure, and the most vulnerable position is the left and right arch foot, followed by the left and right arch shoulder; The bending moment of the pile body changes nonlinearly in the height direction. The most significant bending moment value appears at the top 1/5 of the pile length and the junction of different strata. Furthermore, the most significant horizontal displacement of the lining structure occurs at the tunnel vault
Study on empirical model and CFD about pressure rising in Cab during door closure
Get PDFAiming at the problem that there is a strong eardrum pressure in the passenger car during the closing process, two analysis and prediction methods, fast formula prediction and CFD simulation based on accurate models, are proposed. The regression model of ear pressure comfort was established by DOE method and multiple linear regression; The simulation software star-CCM+ is applied to simulate and analyze the dynamic characteristics of the flow field in the cockpit during the closing process by using the overlapping grid technology, and the pressure change curve near the ear is obtained. Finally, the CFD numerical simulation model is established by comparing and analyzing the regression prediction analysis results and the real vehicle test data. The results show that the effects of closing speed, effective opening area of pressure relief valve and air tightness of the whole vehicle on the pressure of passengers’ eardrums decrease in turn, and the prediction error of multiple linear regression equation is 17 %; The analysis error of the internal flow field dynamic characteristic model based on refined modeling is 8 %. This study provides a theoretical basis for solving the problem of rapid prediction of eardrum pressure and optimization of engineering structure