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In response to the issues of easy damage and unreasonable arrangement of the arm structure in inclined arm surface hole radial gate, the spatial system method was used to systematically study the layout type of arm structure of inclined arm surface hole radial gate. By analyzing the impact of five commonly used arm structures on strength, stiffness, stability and vibration characteristics of inclined arm surface hole radial gate structure and the arm itself, and combining with the "big data" of hydraulic metal structures, the advantages and disadvantages of the gate support arm in structural design, manufacturing and processing, transportation and installation, operation and maintenance were comprehensively considered, and a reasonable structural type of the surface hole inclined arm had been provided. The influence mechanism of the vertical and diagonal braces on the strength, stiffness and stability of the braced arm structure was clarified. The research results are proved to be reasonable by practical engineering. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the static and dynamic behaviors of the postbuckling of axially moving spin beams (bi-gyro system). The Hamilton's principle is used to derive the nonlinear governing equations of bi-gyro systems, which are based on the Euler-Bernoulli beam model and account for von Karman geometric nonlinearity. After neglecting the time-dependent terms, the static equations are discretized using the differential quadrature method and then solved as a nonlinear algebraic system via the Newton-Raphson iteration method. Subsequently, the linear vibration problem is accurately solved for axially moving spinning beams in their first buckled configuration. Finally, numerical calculations are conducted to investigate the impact of axial and spinning velocities on the steady-state dynamic responses of bi-gyro systems. The findings are as follows: (a) the critical axial velocity where trivial equilibrium is unstable remains unaffected by the presence of spinning velocity; (b) the bifurcation point of the axial velocity corresponding to amplitude is reduced by spinning velocity, resulting from centrifugal force; (c) the vibration amplitude of the bi-gyro system will diverge under a weaker displacement constraint spring; and (d) stable buckled and straight configurations can coexist under certain axial and spinning velocities. [ABSTRACT FROM AUTHOR]

To enhance the static and dynamic performance of the grinding wheel spindle system, with the gear grinding machine (YKF2060) as the research object, a static mechanics model of the spindle system was established based on Castigliano's theorem, taking into account the equivalent effect of the triple-point contact ball bearing at the front end of the spindle. Meanwhile, based on the overall transfer matrix method, a dynamic model of the main spindle–eccentric shaft dual-rotor system was established, taking into account the effects of shear deformation and gyroscopic moments. On this basis, the effect of the spindle span, the front and rear overhang of the eccentric shaft, and the bearing stiffness on the static stiffness and first-order critical speed of the system was analyzed. Finally, static stiffness experiments, modal tests, and finite element simulation models were conducted to verify the static and dynamic models. The results show that the stiffness of the front outer bearing has the greatest influence on the static and dynamic performance of the system, while the stiffness of the rear inner bearing has the least influence. The relative errors of the static stiffness and the first two natural frequencies between static stiffness experiments, modal tests, and finite element simulation models are less than 10%, and the mode shapes match well. The established static and dynamic model can effectively reflect both the static and dynamic characteristics of the spindle system. [ABSTRACT FROM AUTHOR]

The development of reusable liquid rocket turbopumps has gradually highlighted the disadvantages of rolling bearings, particularly the contradiction between long service life and high rotational speed. It is critical to explore a feasible bearing scheme offering a long wear life and high stability to replace the existing rolling bearings. In this study, liquid nitrogen is adopted to simulate the ultra-low temperature environment of liquid rocket turbopumps, and theoretical evaluations of the lubrication performance of thrust-type foil bearings in liquid nitrogen are conducted. A link-spring model for the bump foil structure and a thin-plate finite element model for the top foil structure are established. The static and dynamic characteristics of the bearings are analyzed using methods including the finite difference method, the Newton–Raphson iteration method, and the finite element method. Detailed analysis includes the effects of factors such as rotational speed, fluid film thickness, thrust disk tilt angle, and the friction coefficient of the bump foil interface on the static and dynamic characteristics of thrust-type foil bearings. The research results indicate that thrust-type foil bearings have a good load-carrying capacity and low frictional power consumption. The adaptive deformation of the foil structure increases the fluid film thickness, preventing dry friction due to direct contact between the rotor journal and the bearing surface. When faced with thrust disk tilt, the direct translational stiffness and damping coefficient of the bearing do not undergo significant changes, ensuring system stability. Based on the results of this study, the exceptional performance characteristics of thrust-type foil bearings make them a promising alternative to rolling bearings for the development of reusable liquid rocket turbopumps. [ABSTRACT FROM AUTHOR]

The spaceborne turntable is a piece of precision optical equipment utilized for monitoring space information and facilitating laser communication. The measurement accuracy of optical instruments is correlated to some extent with the mechanical properties of the structure. Addressing the design challenge posed by the U-frame in the spaceborne optoelectronic tracking and pointing turntable, this paper proposes a multi-constraint topology optimization method utilizing Abaqus/CAE and TOSCA. This method offers insights for U-frame design and has undergone scientific validation. Initially, the empirical design structure is established, optimization design areas are defined, and the initial model undergoes pre-processing in Abaqus/CAE. Subsequently, conceptual and mathematical models for topology optimization are developed, with the objective of minimizing structural compliance (thereby maximizing stiffness), and including constraints related to volume fraction, first-order natural frequency, and stress. Utilizing TOSCA, the U-frame topology optimization design is finalized, resulting in an optimized conceptual model. A comparative analysis of the optimized design against the empirical design structure demonstrates a significant 27.53% reduction in maximum stress, enhanced static stiffness, an increase of 11.48% in the first natural frequency, and a 4.3% reduction in mass. Moreover, the turntable that utilizes the optimized design structure not only meets reliability requirements in spacecraft structural design but also provides a stable platform for precise optical load alignment. The static and dynamic performance of the optimized U-frame has been enhanced, effectively mitigating the impact of external excitation on optical instrument measurement accuracy and meeting the lightweight design requirements for the U-frame, thus demonstrating the efficacy of the topology optimization method. This research offers valuable insights into U-frame design for spaceborne optoelectronic tracking and pointing turntables and carries significant guiding implications. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Liquid sodium hybrid bearing is mechanical pump shaft bottom key support components, that play a balanced radial force of the impeller by fluid effect, in order to improve the bearing performance, based on the calculation model, simulation analysis, structure improvement and other aspects of analysis, this paper based on the theory of fluid mechanics of bearing finite element model for numerical calculation and analysis of flow field. Under different eccentricities and vibration velocities, the influence of structure improvement on bearing capacity is analysed. The results show that the bearing capacity of the liquid sodium hybrid bearing is mainly the hydrostatic bearing capacity, and the hydrodynamic pressure only plays an auxiliary role. After the improvement of the load‐bearing structure, the load‐bearing capacity is increased by 4%–7.3%. And the leakage is reduced by 27%–38% when the depth of the annular groove is 0.6 mm. [ABSTRACT FROM AUTHOR]

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To enhance the static and dynamic performance of the grinding wheel spindle system, with the gear grinding machine (YKF2060) as the research object, a static mechanics model of the spindle system was established based on Castigliano’s theorem, taking into account the equivalent effect of the triple-point contact ball bearing at the front end of the spindle. Meanwhile, based on the overall transfer matrix method, a dynamic model of the main spindle–eccentric shaft dual-rotor system was established, taking into account the effects of shear deformation and gyroscopic moments. On this basis, the effect of the spindle span, the front and rear overhang of the eccentric shaft, and the bearing stiffness on the static stiffness and first-order critical speed of the system was analyzed. Finally, static stiffness experiments, modal tests, and finite element simulation models were conducted to verify the static and dynamic models. The results show that the stiffness of the front outer bearing has the greatest influence on the static and dynamic performance of the system, while the stiffness of the rear inner bearing has the least influence. The relative errors of the static stiffness and the first two natural frequencies between static stiffness experiments, modal tests, and finite element simulation models are less than 10%, and the mode shapes match well. The established static and dynamic model can effectively reflect both the static and dynamic characteristics of the spindle system.

The properties of a bipolar NPN transistor when exposed to unmodulated incoherent radiation created by a white LED are studied. The static and dynamic characteristics of the transistor are measured at various exposure intensities. It is shown that the change in the characteristics of the transistor under the optical effect is due to the increased lifetime of nonequilibrium charge carriers and the photovoltaic effect in PN transitions. For these reasons, the gain increases, the switching threshold decreases, and the transistor's speed increases. The results obtained are applicable both to the creation of high-speed transistors and integrated circuits of a fundamentally new type. [ABSTRACT FROM AUTHOR]

The development of reusable liquid rocket turbopumps has gradually highlighted the disadvantages of rolling bearings, particularly the contradiction between long service life and high rotational speed. It is critical to explore a feasible bearing scheme offering a long wear life and high stability to replace the existing rolling bearings. In this study, liquid nitrogen is adopted to simulate the ultra-low temperature environment of liquid rocket turbopumps, and theoretical evaluations of the lubrication performance of thrust-type foil bearings in liquid nitrogen are conducted. A link-spring model for the bump foil structure and a thin-plate finite element model for the top foil structure are established. The static and dynamic characteristics of the bearings are analyzed using methods including the finite difference method, the Newton–Raphson iteration method, and the finite element method. Detailed analysis includes the effects of factors such as rotational speed, fluid film thickness, thrust disk tilt angle, and the friction coefficient of the bump foil interface on the static and dynamic characteristics of thrust-type foil bearings. The research results indicate that thrust-type foil bearings have a good load-carrying capacity and low frictional power consumption. The adaptive deformation of the foil structure increases the fluid film thickness, preventing dry friction due to direct contact between the rotor journal and the bearing surface. When faced with thrust disk tilt, the direct translational stiffness and damping coefficient of the bearing do not undergo significant changes, ensuring system stability. Based on the results of this study, the exceptional performance characteristics of thrust-type foil bearings make them a promising alternative to rolling bearings for the development of reusable liquid rocket turbopumps.

Research on CL-20-based aluminized explosives formulation and equipment application shows a critical research avenue. When these explosives are damaged, it affects safety, detonation stability, and reliability, which, in turn, impacts weapon system longevity, safety, and combat effectiveness. However, only some studies have explored the mechanical properties due to their complexity. This paper improves the existing models based on experimental data and a modified genetic algorithm. We obtain a more generalized description of theoretical equations, considering the strain-rate effect, which can better match macro-scale experimental results. Then, we compare laboratory and numerical experiments to investigate the static and dynamic characteristics at the mesoscale. As the theory of sound predicted, the distribution characteristics of stress, plastic strain, and density align with stress wave paths. Notably, local maxima approximately correlate with strain rate and compression effects. Boundary conditions also matter, which researchers should consider during practical engineering verification and application to avoid misleading conclusions. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aerostatic porous bearings have been applied widely in precision devices to achieve higher accuracy of motion. Conventional aerostatic porous bearings are made of porous graphite, porous ceramics or sintered metal porous material, having a thickness of several millimetres and a surface-restricted layer. However, during mass production of porous bearings, the time required for the production of the porous materials and the surface restriction treatment leads to an increase in the manufacturing time and cost of the porous bearings. Accordingly, to overcome this problem, an aerostatic porous bearing with a layer thickness of several hundred µm and a support member, manufactured using metal 3D printing technology, is proposed. In this study, the optimum conditions for manufacturing the proposed aerostatic porous bearings with a direct metal laser sintering method 3D printer were investigated, and characteristics of the prototype of the proposed bearings were investigated experimentally. [ABSTRACT FROM AUTHOR]

The current detection methods for grassland fires mainly rely on manual means, which are costly, inefficient, and difficult to achieve real-time and full coverage detection. Therefore, the YOLOv5m-D model and its static and dynamic characteristics are proposed to detect and identify smoke and flame throughout the entire process of grassland fires, and its effectiveness is verified. The experimental results showed that in smoke recognition and detection, YOLOv5m-D model showed slow local convergence under the condition of low Learning rate, and the mAP value of YOLOv5m-D was 86.4% when the batch size was 16. In the comparison of mAP values under the optimal hyperparameters, the Faster RCNN value was 72.34%, SSD value was 75.90%, YOLOv5m value was 86.75%, and YOLOv5m-D value was 89.28%, which was higher than the comparison model. In flame recognition detection, in the Hu1 moment, the ordinary image sequence and infrared thermal imaging sequence, except for a few that were around 0.8, were mostly maintained at around 0.3-0.7, while the color tent was both below 0.1. After combining infrared images with flame static and dynamic feature recognition, the flames are basically recognized. In the comparison of single feature recognition time, the current frame recognition time of different images under the vast majority of features is lower than the reference frame. Overall, the YOLOv5m-D model proposed in the study and its static and dynamic characteristics are effective in detecting and identifying smoke and flame throughout the entire process of grassland fires, and have high practical effects for practical grassland fire detection.

Copyright of Journal of Southeast University / Dongnan Daxue Xuebao is the property of Journal of Southeast University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents a hydrodynamic lubrication model to investigate the static and dynamic characteristics of micro-grooved bearings considering journal misalignment. An averaged Reynolds equation with the mass conservation is derived and numerical procedure is solved by the finite difference method. The influences of eccentricity ratio, misalignment and micro-groove parameters on lubrication performances of aligned/misaligned journal bearings are compared systematically. Mathematical expressions of five micro-grooves with different geometric shapes i.e., straight-groove, left spiral-groove, right spiral-groove, left herringbone-groove and right herringbone-groove are given. The results show that with the increase of degree of misalignment, the load carrying capacity, main stiffness and damping coefficients increase, and the friction coefficient decreases, while the effect of misalignment angle on bearing performance is opposite. The results also indicated that the left herringbone-groove has better performance improvement for aligned journal bearing, while the right spiral-groove has better performance improvement for misaligned journal bearing under the optimal micro-groove parameters, especially at low eccentricity ratio. Moreover, the amount of the performance improvement of micro-grooved bearing depends on the design of the micro-groove parameters. This study can provide theoretical guidance for the design optimization of micro-grooved journal bearings with misalignment. [ABSTRACT FROM AUTHOR]

Wear is one of the most common failures of hydrodynamic bearings. The main purpose of the present work was to investigate the effects of wear on lubrication performance and acquire efficient vibration signatures for fault diagnosis. In this paper, a finite element model (FEM) for a two-disk rotor supported on worn hydrodynamic bearings is presented in which the oil film force is evaluated by linear and nonlinear models. Numerical and experimental results indicate that the static and dynamic characteristics of the bearing are significantly changed by wear, leading to a drop in system critical speeds due to the deterioration of the constraint status provided by the bearings to the rotor. As the wear depth increases, the onset speed of oil whirl increases, while that of oil whip becomes lower, and large amplitudes of resonance and oil whip are more likely to be excited. More notably, all of the above vibration signatures in the y-direction are more sensitive to wear compared to those in the x-direction, which means that wear faults can be diagnosed by differences in vibration characteristics between the x- and y-directions. This research can provide a theoretical foundation and engineering guidance for the hydrodynamic bearing wear fault diagnosis. [ABSTRACT FROM AUTHOR]

The generation of frictional vibration and noise by water-lubricated bearings is one of the most severe problems putting at risk the safety and concealment of ships. Here, Halbach magnet arrays were integrated as the upper bush of the water-lubricated bearing with the aim of suppressing frictional vibration. Simulations and experiments were conducted and compared between the magnetic bearing and a normal rubber bearing. Effects of magnetic strength, Halbach array length, rotational speed, and external load on bearing characteristics were analyzed. The results show superior static and dynamic performances on the magnetic bearing. More specifically, attractive forces generated by Halbach magnets can reduce static pressure by nearly 37% on the bottom bush. Stiffness of magnetic bearings was calculated as smaller than for normal bearings, indicating a lower natural frequency. Shaft trajectories were observed close to the geometric center of bearing yielding less stress concentration on the bottom bush of the magnetic bearing. Finally, test rig experiments demonstrated suppressed vibrational peaks and reduced frictional vibration (more than 10 dB) on the magnetic bearing. It is also interesting to note that the magnetic bearing even shows exceptional robustness regarding fluctuations of rotating speed or external load. This study presents a new routine for overcoming the frictional vibration and noise of water-lubricated bearings. [ABSTRACT FROM AUTHOR]

Renewable energy sources have become a significant alternative energy source due to the continuing depletion of conventional energy sources and fluctuation in fuel costs. Currently, wind energy is the foremost among all other renewable energy sources. However, modeling and analyzing industrial wind turbines is complex as the wind turbine power ratio and size have steadily increased. Undoubtedly, industrial wind turbines are huge and challenging to keep in research labs; simultaneously, exploring the controller/power converter performance is practically impossible. Therefore, to overcome the above drawbacks, wind turbine emulators have been developed to achieve the static and dynamic characteristics of wind energy conversion systems. This paper aims to present a comprehensive review of the different wind turbine emulators available in the literature. In addition, the implementation of real-time emulators is classified according to the structure and approaches. Furthermore, an extensive analysis of the emulators was presented based on the significant parameters utilized for the real-time wind turbine emulators. Finally, this review analyzes the different emulator topologies according to cost, accuracy, complexity, and hardware implementation. [ABSTRACT FROM AUTHOR]

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The vertical water-lubricated bearing technology widely used in the third generation pressurized water reactor nuclear power plant is one of the key points restricting the development of nuclear power in China.Therefore,it is of important engineering value to establish a vertical bearing test bench for relevant tests. A design scheme of vertical water-lubricated tilting pad bearing test bench was proposed,which included loading-drive system,lubrication-seal system and measurement system.By comparing the difference of bearing restraint between horizontal bearing test bench and vertical bearing test bench during loading,the floating bearing restraint mechanism scheme suitable for vertical bearing test bench was given.According to the similar criteria,the vertical water lubricated tilting pad bearing of AP1000 nuclear main pump was designed in a reduced scale, and bearing test pieces suitable for test and research were designed under the condition that the requirements of Summerfeld number,width diameter ratio and clearance ratio were met.The test results show that the developed vertical four-pad tilting pad water lubricated bearing test bench can measure the bearing surface temperature, water supply pressure, static load, water film pulsating pressure, rotating shaft whirl under different rotational speeds and loading excitation conditions.The operating state of the test bench is stable,which can meet the research requirements of dynamic and static characteristics of vertical water-lubricated tilting pad bearings. [ABSTRACT FROM AUTHOR]

The dynamic characteristics determine variations of the inlet pressure in front of the valve in function of the flow through the valve in the time. In any hydraulic system, the valve is connected at least by a pipe at the outlet, and at its inlet there is some volume of compressible oil which influences the quality of the transient process. When switching the directional control valve in the hydraulic system with directoperated pressure relief valves, a transient process occurs in which it is possible for the pressure to reach values many times higher than the set value. This causes the system to be overloaded with undesirable consequences. This paper examines experimentally and theoretically the transients in hydraulic systems with these valves. From the experimental static characteristics, the coefficient of hydrodynamic force acting on the valve poppet is determined. [ABSTRACT FROM AUTHOR]

Modern internal combustion powertrains are the main source of propulsion for on-road and non-road vehicles. However, they are increasingly being replaced by electric or fuel cell-equipped alternative propulsion systems. The article presents a study of fuel cell characteristics operating under both static and dynamic conditions, with a 1.2 kW fuel cell set with a voltage converter and lead-acid batteries. In the conducted tests, the fuel cell stack's maximum efficiency reached 65%. Load tests (static and dynamic) have indicated higher fuel cell efficiencies when using hybrid operation with a DC/DC converter and battery. [ABSTRACT FROM AUTHOR]

An optical free-form milling machine is designed according to the technological characteristics of optical component manufacturing and the finite element (FE) modeling and static and dynamic characteristics analysis of the optical free-form surface milling machine are carried out. The results show that, at the original position under gravity load, when the gravity balance device is not working, the straightness of guide rail is 0.7μm, and when the gravity balance device is working, the straightness of guide rail is 0.035μm, when the gravity balance device is not working, the straightness of lead screw is 2.3μm, and when the gravity balance device is working, the straightness of lead screw is 0.2μm. The natural frequencies of the optical free-form surface milling machine with different structural schemes and material schemes are extracted, and the vibration mode shows that the first vibration mode of the milling machine that affects the machining precision is the third order, the optimal design scheme of dynamic characteristics is that the Z-axis motor of the milling machine is installed on the roof and the milling machine structure material uses natural granite, and the milling machine structure material using natural granite compared with cast iron can significantly improve the dynamic characteristics of the milling machine. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Henan University of Technology Natural Science Edition is the property of Henan University of Technology Journal Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The purpose of this paper is to analyze the influence of turbulent, inertia, and misaligned effects on the static and dynamic characteristics and stability of high-speed water-lubricated hydrodynamic journal bearings. Based on the Navier–Stokes equation, the mixing-length theory, and the essential assumption that the velocity profile is not strongly affected by inertia force, the fluid lubrication model with turbulent, inertia, and misaligned effects is established, and then the stability analysis of bearings is carried out based on the equation of motion with four degrees of freedom. The model is solved by the finite difference method and the numerical results are compared under different operating conditions. The results show that the turbulent effect greatly increases the load capacity, power consumption, stiffness and damping coefficients, and stability of bearings, and the inertia effect significantly increases the volume flow rate of bearings, and the misaligned effect increases the load capacity, stiffness and damping coefficients, and stability of bearings. In high rotary speed and moderate eccentricity ratios, the influence of the inertia effect on the load capacity, stiffness coefficients, and stability cannot be neglected. [ABSTRACT FROM AUTHOR]

A probe is an important part of high-precision thread-measuring machines. Probe design affects the ability of the machine to achieve precision. The development of three-dimensional (3D) thread-measuring machines has mandated strict requirements for matching measuring heads. A contact scanning probe offers the advantages of a relatively high measurement accuracy and stable performance. In this study, the structure of the scanning probe was designed. First, a micro-force probe model was established according to 3D thread characteristics. The "T"-shaped, ballpoint-pen-shaped needle was selected according to the characteristics of the detection hole and thread. Thereafter, the dimension parameters of the measuring ball, measuring bar, parallel spring plates, and other components were designed to enable the measuring head to meet the precision requirements. The flexural deformation of the measuring rod was analyzed to determine the appropriate length and diameter of the measuring rod. Finally, the effective static and dynamic characteristics of the head were demonstrated through finite element simulation and experimental measurements. In addition, the static characteristics of the probe were measured. The return error was 0.29 µm, and the repeatability error was 0.24 µm. The dynamic characteristics were tested using the percussion method, and the natural frequency was 180 Hz. These results help ensure the precision of the probe and improve the measuring precision of the machine. [ABSTRACT FROM AUTHOR]

At present, piezoelectric sensors are primarily applied in health monitoring areas. They may fall off owing to the adhesive's durability, and even damage the monitored equipment. In this paper, a piezoelectric film sensor (PFS) based on a positive piezoelectric effect (PPE) is presented and a ZnO film is deposited on a GH4169 superalloy steel (GSS) substrate using magnetron sputtering. The microstructure and micrograph of ZnO piezoelectric thin films were analyzed by an X-ray diffractometer (XRD), energy dispersive spectrometer (EDS), scanning electron microscope (SEM), and atomic force microscope (AFM). The results showed that the surface morphology was dense and uniform and had a good c-axis-preferred orientation. According to the test results of five piezoelectric sensors, the average value of the longitudinal piezoelectric coefficient was 1.36 pC/N, and the average value of the static calibration sensitivity was 19.77 mV/N. We selected the sensor whose parameters are closest to the average value for the dynamic test experiment and we drew the output voltage response curve of the piezoelectric film sensor under different loads. The measurement error was 4.03% when repeating the experiment six times. The research achievements reveal the excellent performance of the piezoelectric film sensor directly deposited on a GH4169 superalloy steel substrate. This method can reduce measurement error caused by the adhesive and reduce the risk of falling off caused by the aging of the adhesive, which provides a basis for the research of smart bolts and guarantees a better application in structural health monitoring (SHM). [ABSTRACT FROM AUTHOR]

In order to analysis static and dynamic characteristics of a certain type electric wheel dump truck frame,the load information of key bearing connection sites of the fame was obtained by the rigid and flexible coupling multi-body dynamics analysis for the whole vehicle and the finite element model of the frame with welding details was constructed simultaneously.Then,the static analysis of the frame on the condition of static state with full load was carried out and its correctness was verified by using stress test on the mine road surface. The dynamic analysis of the frame under the conditions of horizontal bending,ultimate torsion and emergency braking with full load,stiffness analysis and modal analysis were conducted. The results can be illustrated that the stiffness of the frame under the ultimate torsion condition has some room for improvement to avoid frame failure.Therefore,the multi-objective optimization design for the frame stiffness under different conditions was carried out by utilizing topological optimization technology. The result shows that the reconstructed frame after optimization satisfies operating requirements of the whole vehicle and this analysis method also provides some reference experience for frame static and dynamic characteristics design as well.

Wear is one of the most common failures of hydrodynamic bearings. The main purpose of the present work was to investigate the effects of wear on lubrication performance and acquire efficient vibration signatures for fault diagnosis. In this paper, a finite element model (FEM) for a two-disk rotor supported on worn hydrodynamic bearings is presented in which the oil film force is evaluated by linear and nonlinear models. Numerical and experimental results indicate that the static and dynamic characteristics of the bearing are significantly changed by wear, leading to a drop in system critical speeds due to the deterioration of the constraint status provided by the bearings to the rotor. As the wear depth increases, the onset speed of oil whirl increases, while that of oil whip becomes lower, and large amplitudes of resonance and oil whip are more likely to be excited. More notably, all of the above vibration signatures in the y-direction are more sensitive to wear compared to those in the x-direction, which means that wear faults can be diagnosed by differences in vibration characteristics between the x- and y-directions. This research can provide a theoretical foundation and engineering guidance for the hydrodynamic bearing wear fault diagnosis.

The results of the optimization of design and technological parameters device structures insulated-gate bipolar transistor (IGBT), formed in bulk silicon and using «Silicon on Insulator» (SOI) technology are presented. The specific features of the functioning of various constructive solutions IGBT are studied. A construction of SOI-IGBT structure with multiple gates, which allows a step change in the switched current, is suggested and investigated.

The main elements of the statistical model of packed hole assemblies (PHA) design for drilling holding sections in conditions of information uncertainty are formalized and described. A constraint system has been given for the angle maintenance conditions of wellbore direction and dynamic stability of bottom hole assembly (BHA) lateral vibrations. The influence of the information uncertainty of some factors (angle, parameters of the drilling practice, presence of local caverns, etc.) on risk indicators has been analyzed according to the results of the numerical calculations. It has been determined that the risks of angle maintenance disturbance are significantly influenced by the angle and weight on the bit (WOB), and dynamic stability conditions, such as angle and rotation frequency. Risks of multi-supported BHAs which have been designed for conditions of minimizing bit side force, dynamic stability and include 4-6 stabilizers. [ABSTRACT FROM AUTHOR]

In this work, the process of vacuum membrane distillation in the process of extracting ethanol from molasses solution was investigated. The growth of biofuel production (especially anhydrous ethanol) stimulated the search for new methods that allow to extract and concentrate it in a more efficient and profitable way; membrane technology is one of them. Membrane distillation, intended for the extraction of alcohols, is a technique using porous membranes to separate the liquid mixture, in which the driving force of the process is the partial pressure gradient on the membrane. During the process, the volatile components must change phase to pass through the membrane. The main advantage of this method is the possibility of continuous removal of ethanol at the stage of production of fuel alcohol. Membrane distillation with vacuum, designed to reduce alcohols is almost not studied. The urgent task is to create a mathematical model of the process. In this paper, a mathematical model of the dynamics of temperature and concentration at the outlet of the membrane module is developed. The formulated assumptions are accepted at development of mathematical model of process. The mathematical model takes into account the change in the concentration of ethanol in the solution at the outlet and in the vapor diffusing through the membrane. Possible control effects are considered to be the change of vacuum in the permeate channel and the flow of cooling water for condensation of ethanol vapors. . Static and dynamic characteristics of the control and perturbation channels are determined on the basis of the created mathematical model of the process. The influence of assumptions on the type and nature of dynamic properties is investigated. The system was studied in the state space. The finite difference method is used to solve the mathematical model using the Matlab software tool. The graphic results of the research are given. [ABSTRACT FROM AUTHOR]

At present, piezoelectric sensors are primarily applied in health monitoring areas. They may fall off owing to the adhesive’s durability, and even damage the monitored equipment. In this paper, a piezoelectric film sensor (PFS) based on a positive piezoelectric effect (PPE) is presented and a ZnO film is deposited on a GH4169 superalloy steel (GSS) substrate using magnetron sputtering. The microstructure and micrograph of ZnO piezoelectric thin films were analyzed by an X-ray diffractometer (XRD), energy dispersive spectrometer (EDS), scanning electron microscope (SEM), and atomic force microscope (AFM). The results showed that the surface morphology was dense and uniform and had a good c-axis-preferred orientation. According to the test results of five piezoelectric sensors, the average value of the longitudinal piezoelectric coefficient was 1.36 pC/N, and the average value of the static calibration sensitivity was 19.77 mV/N. We selected the sensor whose parameters are closest to the average value for the dynamic test experiment and we drew the output voltage response curve of the piezoelectric film sensor under different loads. The measurement error was 4.03% when repeating the experiment six times. The research achievements reveal the excellent performance of the piezoelectric film sensor directly deposited on a GH4169 superalloy steel substrate. This method can reduce measurement error caused by the adhesive and reduce the risk of falling off caused by the aging of the adhesive, which provides a basis for the research of smart bolts and guarantees a better application in structural health monitoring (SHM).

Bump-type gas foil bearing is a special type of sliding bearing, especially suitable for supporting rotors with light loads and high speeds. In this paper, a deformation model of bump foil is established by using elastic mechanics theory. A fluid-structure interaction algorithm is proposed according to Reynolds equation of compressible gas. On this basis, a method for calculating the static and dynamic characteristics of the bump-type gas foil bearing is established considering the structure parameters of the bump foil. The presented model is validated using the data reported in the existing research. The gas film pressure distribution, gas film thickness distribution of the bearing, and the influences of bump foil structure parameters on the static and dynamic characteristics of the bearing are studied with an example. Results show that, decreasing the bump foil thickness tB or increasing the bump pitch s will increase the limiting load-carrying capacity W and decrease the attitude angle β. And increasing tB or decreasing s will decrease the friction torque Tr and increase the side leakage flow of gas Qz, resulting in less friction heat generation and faster heat dissipation. Increasing tB or decreasing s will increase the absolute values of K xx , K xy , K yx , K yy , C xx , C xy , C yx and C yy of the gas film, leading to higher equivalent stiffness of the gas film K eq . [ABSTRACT FROM AUTHOR]

A novel 50 nm recessed T-gate AlN spacer based InAlN/GaN HEMT with AlGaN back-barrier is designed. The static and dynamic characteristics of the proposed device structure are investigated using Synopsys TCAD tool. The remarkable potential device features such as heavily doped source/drain region, Al2O3 passivated device surface helped the device to suppress the parasitic resistances and capacitances of the transistor for enhancing the microwave characteristics. The designed InAlN/GaN HEMT exhibits the sheet carrier density (ns) of 1.9 × 1013 cm−2, the drain current density (Ids) of 2.1 A/mm, the transconductance (gm) of 800 mS/mm, the breakdown voltage (VBR) of 40 V, the current gain cut-off frequency (ft) of 221 GHz and the power gain cut-off frequency (fmax) of 290 GHz. The superior static and dynamic characteristics of obtained InAlN/GaN HEMTs undoubtedly placed the device at the forefront for high power millimeter wave applications.

A novel full circumferential reluctance maglev coupling (FCRMC) is proposed in this paper, which not only meets the requirements of force transmission and valve position feedback of two-dimensional (2D) valve but also has the advantages of closed-loop magnetic circuit and high magnetic energy utilization rate. To investigate the torque-displacement characteristic of FCRMC, a detailed analytical model based on the equivalent magnetic circuit method is formulated, which considers the leakage flux effect, edge effect, and magnetic permeability nonlinearity. The effects of the inclination angle, width, air gap, and number of teeth on the torque are explored by the analytical model, and appropriate structural parameters are selected to design and manufacture the prototype. A dedicated test bench is built and the static/dynamic characteristics of FCRMC are tested. The experimental results show that the FCRMC prototype has a step velocity of 20.8 × 10−3 mm/ms, a torque-volume ratio of 8.47 × 10−3 N m/cm3, a torque-permanent magnets(PMs) volume ratio of 0.050 N m/cm3, and a step velocity-PMs volume ratio of 2.63 × 10−3 mm/ms·cm3. Finally, to verify the feasibility of the FCRMC in real work situations, the FCRMC is applied to a 2D electro-hydraulic proportional flow valve. The experimental results show that, at 15 MPa, the no-load flow of the valve is 82.4L/min, with a hysteresis of 3.8 %, a step velocity of 17.5 × 10−3 mm/ms, and amplitude and phase frequency widths of 22.4 Hz and 26.5 Hz. • The highlights of this paper are as follows: since rare earth permanent magnet is a non-renewable strategic resource, the study on rare earth permanent magnet effective utilization of maglev coupling is substantially important. Therefore, a novel FCRMC for 2D valves is proposed, which not only meets the requirements of force transmission and valve position feedback of 2D valves but also has the advantages of closed-loop magnetic circuit and high magnetic energy utilization rate. [ABSTRACT FROM AUTHOR]

Bu çalışmada elektromekanik supap mekanizmalarında kullanılabilecek uygun manyetik devre tipleri incelenmiştir. Disk tipi manyetik devreye elektromekanik supap mekanizması iki farklı tipte tasarlanmış ve yay sabiti, kütle, besleme gerilimi ve tutma akımı gibi çeşitli tasarım parametrelerinin sistem üzerindeki etkileri incelenmiştir. Sistemin statik ve dinamik denklemleri çıkarılarak MATLAB/Simulink programı ile sayısal çözümleri elde edilmiştir. Prototip iki sistem üzerinde deneysel çalışmalar yürütülmüş ve teorik sonuçlarla karşılaştırılmıştır. Elde edilen sonuçlardan benzetim ve deneysel çalışmaların birbiriyle uyumlu olduğu görülmüştür.