The influence of multipass high rotating speed friction stir processing(FSP)on the microstructure evolution,corrosion behavior,and tensile properties of the stirred zone(SZ)was investigated by EBSD,TEM,SEM,electrochem...The influence of multipass high rotating speed friction stir processing(FSP)on the microstructure evolution,corrosion behavior,and tensile properties of the stirred zone(SZ)was investigated by EBSD,TEM,SEM,electrochemical workstation and electronic universal testing machine.The mean grain size of the SZ is significantly refined,and it increases with the increase of the processing pass.In addition to an obvious increase in the number,the distribution ofβ-Al12Mg17 precipitates also becomes more uniform and dispersed with increasing the processing pass.Compared with the as-received AZ31 alloy,the tensile properties of the SZ are hardly improved,but the corrosion resistances are significantly enhanced.The corrosion potential of the SZ prepared by 4-pass FSP is increased from−1.56 V for the unprocessed AZ31 alloy to−1.19 V,while the corrosion current is decreased from 1.55×10^−4 to 5.47×10^−5 A.展开更多
Stationary shoulder friction stir lap welding （SSFSLW） was successfully used to weld 6005A-T6 aluminum alloy in this paper. Effect of pin rotating speed on cross section morphologies and lap shear strength of the SS...Stationary shoulder friction stir lap welding （SSFSLW） was successfully used to weld 6005A-T6 aluminum alloy in this paper. Effect of pin rotating speed on cross section morphologies and lap shear strength of the SSFSLW joints were mainly discussed. Results show that joints without flash and shoulder marks can be obtained by the stationary shoulder. Cross section of the SSFSLW joint presents a basin-like morphology and little material loss. By increasing the rotating speed from 1 000 rpm to 1 600 rpm, both effective sheet thickness and lap width increase, while lap shear failure load firstly decreases and then increases. The maximum failure load of 14. 05 kN /s attained when 1 000 rpm is used. All SSFSLW joints present shear fracture mode.展开更多
The rotating speed fluctuation for turbomachinery is a common problem, which will cause severe destruction for equipments and basis when the fluctuation is very strong. In this paper,in order to study the transient re...The rotating speed fluctuation for turbomachinery is a common problem, which will cause severe destruction for equipments and basis when the fluctuation is very strong. In this paper,in order to study the transient response characteristics of a radial vane pump subjected to slight( 5%) and strong( 20%)fluctuating rotational speeds, the variation characteristics of the external hydraulic performances are numerically predicted by means of computational fluid dynamics( CFD) technology. The results manifest that the responses of head and flow rate are different relative to the fluctuating characteristics of rotational speed. The response of the former is very satisfied in synchronism,while that of the latter is hysteretic. Meanwhile,it is found that the variation tendencies of the static pressures at the inlet and outlet of the pump are completely opposite, while the response characteristics of the dynamic pressures at the inlet and outlet are nearly identical.Subsequently,in order to further reveal the transient behavior during the instantaneous operating periods,two non-dimensional parameters are employed to deeply analyze it. The result shows that the variation tendencies of these two parameters are also approximately opposite.Moreover,the quasi-steady assumption is not able to be used to accurately assess the transient flow during transient operating periods. The comparison results show that the transient behavior does not show obvious distinctions between slight and strong fluctuating rotating speeds.展开更多
We analyze the transverse nonlinear vibrations of a rotating flexible disk subjected to a rotating point force with a periodically varying rotating speed. Based on Hamilton’s principle, the nonlinear governing equati...We analyze the transverse nonlinear vibrations of a rotating flexible disk subjected to a rotating point force with a periodically varying rotating speed. Based on Hamilton’s principle, the nonlinear governing equations of motion (coupled equations among the radial, tangential and transverse displacements) are derived for the rotating flexible disk. When the in-plane inertia is ignored and a stress function is introduced, the three nonlinearly coupled partial differential equations are reduced to two nonlinearly coupled partial differential equations. According to Galerkin’s approach, a four-degree-of-freedom nonlinear system governing the weakly split resonant modes is derived. The resonant case considered here is 1:1:2:2 internal resonance and a critical speed resonance. The primary parametric resonance for the first-order sin and cos modes and the fundamental parametric resonance for the second-order sin and cos modes are also considered. The method of multiple scales is used to obtain a set of eight-dimensional nonlinear averaged equations. Based on the averaged equations, using numerical simulations, the influence of different parameters on the nonlinear vibrations of the spinning disk is detected. It is concluded that there exist complicated nonlinear behaviors including the periodic, period-n and multi-pulse type chaotic motions for the spinning disk with a varying rotating speed. It is also found that among all parameters, the damping and excitation have great influence on the nonlinear responses of the spinning disk with a varying rotating speed.展开更多
In order to control the accumulation of SiC ceramic particles on the wall of the rotating chamber in the frame of a dry granulation process,the effect of the wall reverse speed on the mixing process is investigated.In...In order to control the accumulation of SiC ceramic particles on the wall of the rotating chamber in the frame of a dry granulation process,the effect of the wall reverse speed on the mixing process is investigated.In particular,an Euler-Euler two-phase flow model is used to analyze the dynamics of both SiC particles and air.The numerical results show that by setting a certain reverse rotating speed of the rotating chamber,the accumulation of SiC particles on the wall can be improved,i.e.,their direction of motion in proximity to the wall can be changed and particles can be forced to re-join the granulation process.Experimental tests conducted to verify the reliability of the numerical findings,demonstrate that when the reverse rotating speed of the rotating chamber is 4 r/min,the sphericity of SiC particles in the rotating chamber is the highest and the fluidity is the best possible one.展开更多
Microdroplets and their dispersion,with a large specific surface area and a short diffusion distance,have been applied in various unit operations and reaction processes.However,it is still a challenge to control the s...Microdroplets and their dispersion,with a large specific surface area and a short diffusion distance,have been applied in various unit operations and reaction processes.However,it is still a challenge to control the size and size distribution of microdroplets,especially for high-throughput generation.In this work,a novel ultra-high speed rotating packed bed(UHS-RPB)was invented,in which rotating foam packing with a speed of 4000-12000 r·min^(-1) provides microfluidic channels to disperse liquid into microdroplets with high throughput.Then generated microdroplets can be directly dispersed into a continuous falling film for obtaining a mixture of microdroplet dispersion.In this UHS-RPB,the effects of rotational speed,liquid initial velocity,liquid viscosity,liquid surface tension and packing pore size on the average size(d_(32))and size distribution of microdroplets were systematically investigated.Results showed that the UHS-RPB could produce microdroplets with a d_(32) of 25-63μm at a liquid flow rate of 1025 L·h^(-1),and the size distribution of the microdroplets accords well with Rosin-Rammler distribution model.In addi-tion,a correlation was established for the prediction of d_(32),and the predicted d_(32) was in good agreement with the experimental data with a deviation within±15%.These results demonstrated that UHS-RPB could be a promising candidate for controllable preparation of uniform microdroplets.展开更多
This study focuses on coupled vibrations of rotating thin-walled composite beams subjected to hygrothermal effects.In the existing literature,many studies have been conducted on coupled bending-torsional vibration and...This study focuses on coupled vibrations of rotating thin-walled composite beams subjected to hygrothermal effects.In the existing literature,many studies have been conducted on coupled bending-torsional vibration and resonance in hygrothermal environments.Few studies considered the coupled flapwise-edgewise and resonances of composite thin-walled beams.Considering this,the flapwise-edgewise coupling effects and resonant characteristics of rotating thin-walled composite beams in a hygrothermal environment are studied.The Rayleigh–Ritz method is used to solve the equations of the beam.Results indicate that flapwise-edgewise coupling factors are essential for the vibration analysis of rectangular thin-walled beams.The ply angle and setting angle strongly affect the internal and external resonances.Large ply angles can significantly reduce the chances of primary internal and external resonances occurring when the permitted rotational speed is lower.展开更多
In order to monitor the working state of piston motor and measure its instantaneous rotation speed accurately, the measuring principle and method of instantaneous rotation speed based on industrial personal computer a...In order to monitor the working state of piston motor and measure its instantaneous rotation speed accurately, the measuring principle and method of instantaneous rotation speed based on industrial personal computer and data acquisition card are introduced, and the major error source, influence mechanism and processing method of data quantization error are dis- cussed. By means of hybrid programming approach of LabVIEW and MATLAB, the instantaneous rotation speed measurement system for the piston motor in variable speed hydraulic system is designed. The simulation and experimental results show that the designed instantaneous speed measurement system is feasible. Furthermore, the sampling frequency has an important influ- ence on the instantaneous rotation speed measurement of piston motor and higher sampling frequency can lower quantization er- ror and improve measurement accuracy.展开更多
By discretizing the convection terms with AUSM+-up scheme in the rotating coordinate system,a finite volume analysis code based on multi-block structured grids was developed independently so as to realize the numerica...By discretizing the convection terms with AUSM+-up scheme in the rotating coordinate system,a finite volume analysis code based on multi-block structured grids was developed independently so as to realize the numerical solving of internal flow fields of turbomachineries.Taking an unshrouded radial impeller with the working fluid of water vapour as the research object,the flow response to the fluctuation of rotational speed was calculated.By comparing the surface pressure profiles and velocity contours calculated by the code and commercial software respectively,the accuracy of flow solver was verified.The analysis of flow response data indicates that,as the working condition shifts closer towards the surge boundary,the response of flow parameters such as mass flow and aerodynamic torque will be more nonsynchronous with the fluctuation of rotational speed,and also the influence of density variation on mass flow variation will be smaller.Moreover,the transient variation region of working condition performance will deviate farther away from the steady performance curve as the working condition approaches the surge boundary.Compared to the working conditions with small mass flows,the distribution characteristics of pressure difference load on the blade surface vary little under large mass flow conditions.The reduction of fluctuation amplitude of rotational speed exerts no influence on abating the hysteresis of flow response.展开更多
The primary focus of this study was to investigate a series of novel motors and pumps,based on a new type of structure called double-stator.The double-stator structure can be used as pump or motor just based on the ap...The primary focus of this study was to investigate a series of novel motors and pumps,based on a new type of structure called double-stator.The double-stator structure can be used as pump or motor just based on the application requirements.A certain amount of pumps or motors can be formed in one shell,and these sub-pumps or sub-motors can work alone or be combined without influence on each other.So this kind of double-stator pump(motor) is called a multi-pump(multi-motor).Through the analysis of multifarious connection modes of the double-acting double-stator multi-pumps and multi-motors,the mathematical expressions of the output flow rate and the rotational speed are acquired.The results indicate that a quantity of different flow rates can be provided by one fixed-displacement multi-pump under the condition of unalterable driven speed by electromotor.Likewise,when supplied by settled input flow,without complex variable mechanism,the functions of double-speed,multiple-speed,and even differential connection can be obtained by employing the use of a double-stator multi-motor.The novel hydraulic transmission is made of such a double-stator multi-pump and multi-motor,and has broad application prospects.展开更多
The particle mixing was studied in a cylindrical stirred tank with elliptical dished bottom by experiments and simulations.The impeller types used were double helical ribbon(HR) + bottom HR,pitched blade ribbon + bott...The particle mixing was studied in a cylindrical stirred tank with elliptical dished bottom by experiments and simulations.The impeller types used were double helical ribbon(HR) + bottom HR,pitched blade ribbon + bottom HR,inner and outer HR + bottom HR,and pitched blade ribbon + Pfaudler + bottom HR labeled as impellers Ⅰ to Ⅳ,respectively.The quantitative correlations among the rotational speed,fill level and power consumption for impeller Ⅰ and impeller Ⅱ were obtained by experiments to validate the discrete element method(DEM) simulations.The particle mixing at different operating conditions was simulated via DEM simulations to calculate the mixing index using the Lacey method,which is a statistical method to provide a mathematical understanding of the mixing state in a binary mixture.The simulation results reveal that as the rotational speed increases,the final mixing index increases,and as the fill level increases,the final mixing index decreases.At the same operating conditions,impeller Ⅲ is the optimal combination,which provides the highest mixing index at the same revolutions.展开更多
In order to address the issues of traditional resampling algorithms involving computational accuracy and efficiency in rolling element bearing fault diagnosis, an equal division impulse-based（EDI-based） resampling a...In order to address the issues of traditional resampling algorithms involving computational accuracy and efficiency in rolling element bearing fault diagnosis, an equal division impulse-based（EDI-based） resampling algorithm is proposed. First, the time marks of every rising edge of the rotating speed pulse and the corresponding amplitudes of faulty bearing vibration signal are determined. Then, every adjacent the rotating pulse is divided equally, and the time marks in every adjacent rotating speed pulses and the corresponding amplitudes of vibration signal are obtained by the interpolation algorithm. Finally, all the time marks and the corresponding amplitudes of vibration signal are arranged and the time marks are transformed into the angle domain to obtain the resampling signal. Speed-up and speed-down faulty bearing signals are employed to verify the validity of the proposed method, and experimental results show that the proposed method is effective for diagnosing faulty bearings. Furthermore, the traditional order tracking techniques are applied to the experimental bearing signals, and the results show that the proposed method produces higher accurate outcomes in less computation time.展开更多
An attempt was made to synthesize Cu/B4C surface composite using friction stir processing（FSP） and to analyze the influence of tool rotational speed on microstructure and sliding wear behavior of the composite. The ...An attempt was made to synthesize Cu/B4C surface composite using friction stir processing（FSP） and to analyze the influence of tool rotational speed on microstructure and sliding wear behavior of the composite. The tool rotational speed was varied from 800 to 1200 r/min in step of 200 r/min. The traverse speed, axial force, groove width and tool pin profile were kept constant. Optical microscopy and scanning electron microscopy were used to study the microstructure of the fabricated surface composites. The sliding wear behavior was evaluated using a pin-on-disc apparatus. The results indicate that the tool rotational speed significantly influences the area of the surface composite and the distribution of B4C particles. Higher rotational speed exhibits homogenous distribution of B4C particles, while lower rotational speed causes poor distribution of B4C particles in the surface composite. The effects of tool rotational speed on the grain size, microhardness, wear rate, worn surface and wear debris were reported.展开更多
A wave rotor is suitable for compact and efficient pressure-exchange between gas flows.This work measured the circumferential pressure distribution of the rotor/stator interfaces and utilized a CFD method to simulate ...A wave rotor is suitable for compact and efficient pressure-exchange between gas flows.This work measured the circumferential pressure distribution of the rotor/stator interfaces and utilized a CFD method to simulate the unsteady pressure waves.The experimental and CFD results showed some slopes in the circumferential pressure distributions,and the slopes indicated the traces of specific unsteady pressure waves.Such traces varied regularly if the rotational speed varied within a range from-11%to+11%off the baseline value,but they were seriously disturbed if the rotational speed varied by-45%from the baseline value.It verified that a pressure wave in a wave rotor tended to keep its pressure ratio and propagation velocity unchanged if the rotational speed varied by a small extent,and that the pressure wave could not keep its propagation patterns if the rotational speed varied by a large extent.Because of the pressure wave behaviors,the wave rotor demonstrated specific regulations of the rotational speed effects on its operational states.展开更多
Additive friction stir deposition(AFSD)is a novel structural repair and manufacturing technology has become a research hotspot at home and abroad in the past five years.In this work,the microstructural evolution and m...Additive friction stir deposition(AFSD)is a novel structural repair and manufacturing technology has become a research hotspot at home and abroad in the past five years.In this work,the microstructural evolution and mechanical performance of the Al-Mg-Si alloy plate repaired by the preheating-assisted AFSD process were investigated.To evaluate the tool rotation speed and substrate preheating for repair quality,the AFSD technique was used to additively repair 5 mm depth blind holes on 6061 aluminum alloy substrates.The results showed that preheat-assisted AFSD repair significantly improved joint bonding and joint strength compared to the control non-preheat substrate condition.Moreover,increasing rotation speed was also beneficial to improve the metallurgical bonding of the interface and avoid volume defects.Under preheating conditions,the UTS and elongation were positively correlated with rotation speed.Under the process parameters of preheated substrate and tool rotation speed of 1000 r/min,defect-free specimens could be obtained accompanied by tensile fracture occurring in the substrate rather than the repaired zone.The UTS and elongation reached the maximum values of 164.2MPa and 13.4%,which are equivalent to 99.4%and 140%of the heated substrate,respectively.展开更多
Aluminum alloys are subjected to large deformation and decreased strength due to the high expansion modulus caused by heat effects during friction stir welding （FSW）.The optimum conditions for friction stir welding ...Aluminum alloys are subjected to large deformation and decreased strength due to the high expansion modulus caused by heat effects during friction stir welding （FSW）.The optimum conditions for friction stir welding of 5052-O and 6061-T6 Al alloys were determined.The optimum traveling and rotation speeds were identified to be 61mm/min and 1600r/min using various mechanical characteristic evaluation methods.展开更多
Based on the ABAQUS/Explicit code,A 3D elastic-plastic and coupled thermo-mechanical FE model of radial ring rolling of AZ31 Magnesium alloy has been proposed to analyze the influence of rotational speed of driver rol...Based on the ABAQUS/Explicit code,A 3D elastic-plastic and coupled thermo-mechanical FE model of radial ring rolling of AZ31 Magnesium alloy has been proposed to analyze the influence of rotational speed of driver roll to study the inhomogeneity distribution of strain and temperature,fishtail coefficient,rolling force parameters.The results show that:(1)when the rotational speed of driver roll n increases,the strain distribution of the rolled ring becomes less homogeneous,and the temperature distribution more homogeneous yet,and leading to an optimal n value;(2)the fishtail coefficient firstly decreases,then increases with the increase of n;(3)the rolling force,contact area and rolling moment gradually descend with the increase of n.展开更多
In this study, 5052 steel were joined by a new way aluminum alloy and Q235 of arc milling brazing, with the Zn15%A1 filler metal and no use of flux. Effect of rotation speed on mechanical properties and microstructure...In this study, 5052 steel were joined by a new way aluminum alloy and Q235 of arc milling brazing, with the Zn15%A1 filler metal and no use of flux. Effect of rotation speed on mechanical properties and microstructure of joint interface was investigated. The results show that increasing rotation speed is in favor of formation of weld and spread of filler metal on substrate. The fine grain with homogeneous composition in brazed seam can be realized by the stronger stirring in pool induced by milling at more higher rotation speed. And, a composite joint reinforced with needle-like or block-like Fe-A1-Zn intermetallic compounds （IMCs） particle can be obtained by arc milling brazing, which comes from the reaction between steel scrape and Zn-A1 filler alloy. The test on strength of joint interface shows that with the increase in rotation speed, there is a peak value in variation ranges of strength of joint interface. This is to say, when rotation speed is 2720 r.min-~, the strength of joint has maximum value （182.01 MPa）. Moreover, a thin and discontinuous IMCs layer at joint interface can be obtained by increasing rotation speed. But at a low or high rotation speed, there also is a crack at joint interface, which weakens the strength of joint interface. Only at 2720 r.min-1, a good joint interface without an obvious crack can be realized.展开更多
Recent research in cross-domain intelligence fault diagnosis of machinery still has some problems,such as relatively ideal speed conditions and sample conditions.In engineering practice,the rotational speed of the mac...Recent research in cross-domain intelligence fault diagnosis of machinery still has some problems,such as relatively ideal speed conditions and sample conditions.In engineering practice,the rotational speed of the machine is often transient and time-varying,which makes the sample annotation increasingly expensive.Meanwhile,the number of samples collected from different health states is often unbalanced.To deal with the above challenges,a complementary-label(CL)adversarial domain adaptation fault diagnosis network(CLADAN)is proposed under time-varying rotational speed and weakly-supervised conditions.In the weakly supervised learning condition,machine prior information is used for sample annotation via cost-friendly complementary label learning.A diagnosticmodel learning strategywith discretized category probabilities is designed to avoidmulti-peak distribution of prediction results.In adversarial training process,we developed virtual adversarial regularization(VAR)strategy,which further enhances the robustness of the model by adding adversarial perturbations in the target domain.Comparative experiments on two case studies validated the superior performance of the proposed method.展开更多
In order to apply grinding method for degradation of pentachlorophenol(PCP) to an industrial scale,the proportion of different materials[CaO,SiO_2 and CO(NH_2)_2]and the size of grinding balls were examined.For saving...In order to apply grinding method for degradation of pentachlorophenol(PCP) to an industrial scale,the proportion of different materials[CaO,SiO_2 and CO(NH_2)_2]and the size of grinding balls were examined.For saving energy and increasing dechlorination efficiency,the rotation speed and grinding time were maintained at relatively low values.At a mass ratio of grinding balls to materials(40:1),PCP was added into a big steel jar(300 ml) with other materials to grind at 300 r ·min^(-1)for 5 h.The results indicated that when PCP was mixed with CaO and SiO_2in a molar ratio of 1:60:60,the best dechlorination of 58.4%was achieved.CO(NH_2)_2 could not be used as hydrogen donor in the dehalogenation by mechanochemical reaction,since it restrained the dechlorination process.The size of grinding balls has significant effect on the reaction.The experiment with 5 mm steel balls indicates that the weight is too light to provide appropriate energy for the reaction,while steel balls of 10 and 15 mm could give better dechlorination reaction.It indicates that dechlorination depends on the mass of balls and fill rate.展开更多
基金Projects(51861034,51601167)supported by the National Natural Science Foundation of ChinaProject(2020GY-262)supported by the Science and Technology Department of Shaanxi Province,China+1 种基金Project(2019-86-1)supported by the Technology Bureau of Yulin,ChinaProject(20GK06)supported by the High-level Talent Program of Yulin University,China。
文摘The influence of multipass high rotating speed friction stir processing(FSP)on the microstructure evolution,corrosion behavior,and tensile properties of the stirred zone(SZ)was investigated by EBSD,TEM,SEM,electrochemical workstation and electronic universal testing machine.The mean grain size of the SZ is significantly refined,and it increases with the increase of the processing pass.In addition to an obvious increase in the number,the distribution ofβ-Al12Mg17 precipitates also becomes more uniform and dispersed with increasing the processing pass.Compared with the as-received AZ31 alloy,the tensile properties of the SZ are hardly improved,but the corrosion resistances are significantly enhanced.The corrosion potential of the SZ prepared by 4-pass FSP is increased from−1.56 V for the unprocessed AZ31 alloy to−1.19 V,while the corrosion current is decreased from 1.55×10^−4 to 5.47×10^−5 A.
文摘Stationary shoulder friction stir lap welding （SSFSLW） was successfully used to weld 6005A-T6 aluminum alloy in this paper. Effect of pin rotating speed on cross section morphologies and lap shear strength of the SSFSLW joints were mainly discussed. Results show that joints without flash and shoulder marks can be obtained by the stationary shoulder. Cross section of the SSFSLW joint presents a basin-like morphology and little material loss. By increasing the rotating speed from 1 000 rpm to 1 600 rpm, both effective sheet thickness and lap width increase, while lap shear failure load firstly decreases and then increases. The maximum failure load of 14. 05 kN /s attained when 1 000 rpm is used. All SSFSLW joints present shear fracture mode.
基金Zhejiang Provincial Natural Science Foundation of China(No.LY14E090011)Quzhou Science and Technology Development Fund,China(No.20121057)Zhejiang Provincial Science and Technology Project,China(No.2015C31129)
文摘The rotating speed fluctuation for turbomachinery is a common problem, which will cause severe destruction for equipments and basis when the fluctuation is very strong. In this paper,in order to study the transient response characteristics of a radial vane pump subjected to slight( 5%) and strong( 20%)fluctuating rotational speeds, the variation characteristics of the external hydraulic performances are numerically predicted by means of computational fluid dynamics( CFD) technology. The results manifest that the responses of head and flow rate are different relative to the fluctuating characteristics of rotational speed. The response of the former is very satisfied in synchronism,while that of the latter is hysteretic. Meanwhile,it is found that the variation tendencies of the static pressures at the inlet and outlet of the pump are completely opposite, while the response characteristics of the dynamic pressures at the inlet and outlet are nearly identical.Subsequently,in order to further reveal the transient behavior during the instantaneous operating periods,two non-dimensional parameters are employed to deeply analyze it. The result shows that the variation tendencies of these two parameters are also approximately opposite.Moreover,the quasi-steady assumption is not able to be used to accurately assess the transient flow during transient operating periods. The comparison results show that the transient behavior does not show obvious distinctions between slight and strong fluctuating rotating speeds.
基金support of the National Science Foundation for Distinguished Young Scholars of China (Grant No. 10425209)the National Natural Science Foundation of China (Grant No. 10732020)the Funding Project for Academic Human Resources Devel-opment in Institutions of Higher Learning under the Jurisdiction of Beijing Municipality
文摘We analyze the transverse nonlinear vibrations of a rotating flexible disk subjected to a rotating point force with a periodically varying rotating speed. Based on Hamilton’s principle, the nonlinear governing equations of motion (coupled equations among the radial, tangential and transverse displacements) are derived for the rotating flexible disk. When the in-plane inertia is ignored and a stress function is introduced, the three nonlinearly coupled partial differential equations are reduced to two nonlinearly coupled partial differential equations. According to Galerkin’s approach, a four-degree-of-freedom nonlinear system governing the weakly split resonant modes is derived. The resonant case considered here is 1:1:2:2 internal resonance and a critical speed resonance. The primary parametric resonance for the first-order sin and cos modes and the fundamental parametric resonance for the second-order sin and cos modes are also considered. The method of multiple scales is used to obtain a set of eight-dimensional nonlinear averaged equations. Based on the averaged equations, using numerical simulations, the influence of different parameters on the nonlinear vibrations of the spinning disk is detected. It is concluded that there exist complicated nonlinear behaviors including the periodic, period-n and multi-pulse type chaotic motions for the spinning disk with a varying rotating speed. It is also found that among all parameters, the damping and excitation have great influence on the nonlinear responses of the spinning disk with a varying rotating speed.
基金the National Natural Science Foundation of China(Grant No.51964022).
文摘In order to control the accumulation of SiC ceramic particles on the wall of the rotating chamber in the frame of a dry granulation process,the effect of the wall reverse speed on the mixing process is investigated.In particular,an Euler-Euler two-phase flow model is used to analyze the dynamics of both SiC particles and air.The numerical results show that by setting a certain reverse rotating speed of the rotating chamber,the accumulation of SiC particles on the wall can be improved,i.e.,their direction of motion in proximity to the wall can be changed and particles can be forced to re-join the granulation process.Experimental tests conducted to verify the reliability of the numerical findings,demonstrate that when the reverse rotating speed of the rotating chamber is 4 r/min,the sphericity of SiC particles in the rotating chamber is the highest and the fluidity is the best possible one.
基金supported by National Natural Science Foundation of China(21725601)。
文摘Microdroplets and their dispersion,with a large specific surface area and a short diffusion distance,have been applied in various unit operations and reaction processes.However,it is still a challenge to control the size and size distribution of microdroplets,especially for high-throughput generation.In this work,a novel ultra-high speed rotating packed bed(UHS-RPB)was invented,in which rotating foam packing with a speed of 4000-12000 r·min^(-1) provides microfluidic channels to disperse liquid into microdroplets with high throughput.Then generated microdroplets can be directly dispersed into a continuous falling film for obtaining a mixture of microdroplet dispersion.In this UHS-RPB,the effects of rotational speed,liquid initial velocity,liquid viscosity,liquid surface tension and packing pore size on the average size(d_(32))and size distribution of microdroplets were systematically investigated.Results showed that the UHS-RPB could produce microdroplets with a d_(32) of 25-63μm at a liquid flow rate of 1025 L·h^(-1),and the size distribution of the microdroplets accords well with Rosin-Rammler distribution model.In addi-tion,a correlation was established for the prediction of d_(32),and the predicted d_(32) was in good agreement with the experimental data with a deviation within±15%.These results demonstrated that UHS-RPB could be a promising candidate for controllable preparation of uniform microdroplets.
基金supported by the National Natural Science Foundation of China(Grant Nos.11902002 and 51705002)the Sichuan Provincial Natural Science Foundation(Grant No.2022NSFSC0275)the University Outstanding Youth Researcher Support Program of the Education Department of Anhui Province,and the Teaching Project of the Education Department of Anhui Province(Grant No.2022xxsfkc023).
文摘This study focuses on coupled vibrations of rotating thin-walled composite beams subjected to hygrothermal effects.In the existing literature,many studies have been conducted on coupled bending-torsional vibration and resonance in hygrothermal environments.Few studies considered the coupled flapwise-edgewise and resonances of composite thin-walled beams.Considering this,the flapwise-edgewise coupling effects and resonant characteristics of rotating thin-walled composite beams in a hygrothermal environment are studied.The Rayleigh–Ritz method is used to solve the equations of the beam.Results indicate that flapwise-edgewise coupling factors are essential for the vibration analysis of rectangular thin-walled beams.The ply angle and setting angle strongly affect the internal and external resonances.Large ply angles can significantly reduce the chances of primary internal and external resonances occurring when the permitted rotational speed is lower.
基金National Natural Science Foundation of China(No.51275375,No.51509006)Shaanxi Provincial Natural Science Basic Research Plan(No.2014JQ7246)+1 种基金The Science and Technology of Hubei Province(No.B2015115)Doctoral Research Foundation of Hubei University of Automotive Technology(No.BK201403)
文摘In order to monitor the working state of piston motor and measure its instantaneous rotation speed accurately, the measuring principle and method of instantaneous rotation speed based on industrial personal computer and data acquisition card are introduced, and the major error source, influence mechanism and processing method of data quantization error are dis- cussed. By means of hybrid programming approach of LabVIEW and MATLAB, the instantaneous rotation speed measurement system for the piston motor in variable speed hydraulic system is designed. The simulation and experimental results show that the designed instantaneous speed measurement system is feasible. Furthermore, the sampling frequency has an important influ- ence on the instantaneous rotation speed measurement of piston motor and higher sampling frequency can lower quantization er- ror and improve measurement accuracy.
基金supported by the National Key Basic Research Program of China (No.2012CB026000 )the National Science Foundation for Young Scientists (No.2014011155)
文摘By discretizing the convection terms with AUSM+-up scheme in the rotating coordinate system,a finite volume analysis code based on multi-block structured grids was developed independently so as to realize the numerical solving of internal flow fields of turbomachineries.Taking an unshrouded radial impeller with the working fluid of water vapour as the research object,the flow response to the fluctuation of rotational speed was calculated.By comparing the surface pressure profiles and velocity contours calculated by the code and commercial software respectively,the accuracy of flow solver was verified.The analysis of flow response data indicates that,as the working condition shifts closer towards the surge boundary,the response of flow parameters such as mass flow and aerodynamic torque will be more nonsynchronous with the fluctuation of rotational speed,and also the influence of density variation on mass flow variation will be smaller.Moreover,the transient variation region of working condition performance will deviate farther away from the steady performance curve as the working condition approaches the surge boundary.Compared to the working conditions with small mass flows,the distribution characteristics of pressure difference load on the blade surface vary little under large mass flow conditions.The reduction of fluctuation amplitude of rotational speed exerts no influence on abating the hysteresis of flow response.
基金Project(No.50975246)supported by the National Natural Science Foundation of China
文摘The primary focus of this study was to investigate a series of novel motors and pumps,based on a new type of structure called double-stator.The double-stator structure can be used as pump or motor just based on the application requirements.A certain amount of pumps or motors can be formed in one shell,and these sub-pumps or sub-motors can work alone or be combined without influence on each other.So this kind of double-stator pump(motor) is called a multi-pump(multi-motor).Through the analysis of multifarious connection modes of the double-acting double-stator multi-pumps and multi-motors,the mathematical expressions of the output flow rate and the rotational speed are acquired.The results indicate that a quantity of different flow rates can be provided by one fixed-displacement multi-pump under the condition of unalterable driven speed by electromotor.Likewise,when supplied by settled input flow,without complex variable mechanism,the functions of double-speed,multiple-speed,and even differential connection can be obtained by employing the use of a double-stator multi-motor.The novel hydraulic transmission is made of such a double-stator multi-pump and multi-motor,and has broad application prospects.
文摘The particle mixing was studied in a cylindrical stirred tank with elliptical dished bottom by experiments and simulations.The impeller types used were double helical ribbon(HR) + bottom HR,pitched blade ribbon + bottom HR,inner and outer HR + bottom HR,and pitched blade ribbon + Pfaudler + bottom HR labeled as impellers Ⅰ to Ⅳ,respectively.The quantitative correlations among the rotational speed,fill level and power consumption for impeller Ⅰ and impeller Ⅱ were obtained by experiments to validate the discrete element method(DEM) simulations.The particle mixing at different operating conditions was simulated via DEM simulations to calculate the mixing index using the Lacey method,which is a statistical method to provide a mathematical understanding of the mixing state in a binary mixture.The simulation results reveal that as the rotational speed increases,the final mixing index increases,and as the fill level increases,the final mixing index decreases.At the same operating conditions,impeller Ⅲ is the optimal combination,which provides the highest mixing index at the same revolutions.
基金Fundamental Research Funds for the Central Universities(No.2016JBM051)
文摘In order to address the issues of traditional resampling algorithms involving computational accuracy and efficiency in rolling element bearing fault diagnosis, an equal division impulse-based（EDI-based） resampling algorithm is proposed. First, the time marks of every rising edge of the rotating speed pulse and the corresponding amplitudes of faulty bearing vibration signal are determined. Then, every adjacent the rotating pulse is divided equally, and the time marks in every adjacent rotating speed pulses and the corresponding amplitudes of vibration signal are obtained by the interpolation algorithm. Finally, all the time marks and the corresponding amplitudes of vibration signal are arranged and the time marks are transformed into the angle domain to obtain the resampling signal. Speed-up and speed-down faulty bearing signals are employed to verify the validity of the proposed method, and experimental results show that the proposed method is effective for diagnosing faulty bearings. Furthermore, the traditional order tracking techniques are applied to the experimental bearing signals, and the results show that the proposed method produces higher accurate outcomes in less computation time.
文摘An attempt was made to synthesize Cu/B4C surface composite using friction stir processing（FSP） and to analyze the influence of tool rotational speed on microstructure and sliding wear behavior of the composite. The tool rotational speed was varied from 800 to 1200 r/min in step of 200 r/min. The traverse speed, axial force, groove width and tool pin profile were kept constant. Optical microscopy and scanning electron microscopy were used to study the microstructure of the fabricated surface composites. The sliding wear behavior was evaluated using a pin-on-disc apparatus. The results indicate that the tool rotational speed significantly influences the area of the surface composite and the distribution of B4C particles. Higher rotational speed exhibits homogenous distribution of B4C particles, while lower rotational speed causes poor distribution of B4C particles in the surface composite. The effects of tool rotational speed on the grain size, microhardness, wear rate, worn surface and wear debris were reported.
基金co-supported by the National Natural Science Foundation of China(No.51906007)the National Key Laboratory Foundation of China(No.6142702190204)。
文摘A wave rotor is suitable for compact and efficient pressure-exchange between gas flows.This work measured the circumferential pressure distribution of the rotor/stator interfaces and utilized a CFD method to simulate the unsteady pressure waves.The experimental and CFD results showed some slopes in the circumferential pressure distributions,and the slopes indicated the traces of specific unsteady pressure waves.Such traces varied regularly if the rotational speed varied within a range from-11%to+11%off the baseline value,but they were seriously disturbed if the rotational speed varied by-45%from the baseline value.It verified that a pressure wave in a wave rotor tended to keep its pressure ratio and propagation velocity unchanged if the rotational speed varied by a small extent,and that the pressure wave could not keep its propagation patterns if the rotational speed varied by a large extent.Because of the pressure wave behaviors,the wave rotor demonstrated specific regulations of the rotational speed effects on its operational states.
基金financially supported by Science and Technology Major Project of Changsha,China(No.kh2401034)the Fundamental Research Funds for the Central Universities of Central South University(No.CX20230182)the National Key Research and Development Project of China(No.2019YFA0709002)。
文摘Additive friction stir deposition(AFSD)is a novel structural repair and manufacturing technology has become a research hotspot at home and abroad in the past five years.In this work,the microstructural evolution and mechanical performance of the Al-Mg-Si alloy plate repaired by the preheating-assisted AFSD process were investigated.To evaluate the tool rotation speed and substrate preheating for repair quality,the AFSD technique was used to additively repair 5 mm depth blind holes on 6061 aluminum alloy substrates.The results showed that preheat-assisted AFSD repair significantly improved joint bonding and joint strength compared to the control non-preheat substrate condition.Moreover,increasing rotation speed was also beneficial to improve the metallurgical bonding of the interface and avoid volume defects.Under preheating conditions,the UTS and elongation were positively correlated with rotation speed.Under the process parameters of preheated substrate and tool rotation speed of 1000 r/min,defect-free specimens could be obtained accompanied by tensile fracture occurring in the substrate rather than the repaired zone.The UTS and elongation reached the maximum values of 164.2MPa and 13.4%,which are equivalent to 99.4%and 140%of the heated substrate,respectively.
文摘Aluminum alloys are subjected to large deformation and decreased strength due to the high expansion modulus caused by heat effects during friction stir welding （FSW）.The optimum conditions for friction stir welding of 5052-O and 6061-T6 Al alloys were determined.The optimum traveling and rotation speeds were identified to be 61mm/min and 1600r/min using various mechanical characteristic evaluation methods.
基金The authors are grateful for the financial support of Project Supported by:Chongqing Municipal Engineering Research Center of Institutions of Higher Education(cstc2011ptgc70007)Project Supported by Program for Innovation Team Building at Institutions of Higher Education in Chongqing(201028)Achievement Transfer Program of Institutions of Higher Education in Chongqing(kjzh11221).
文摘Based on the ABAQUS/Explicit code,A 3D elastic-plastic and coupled thermo-mechanical FE model of radial ring rolling of AZ31 Magnesium alloy has been proposed to analyze the influence of rotational speed of driver roll to study the inhomogeneity distribution of strain and temperature,fishtail coefficient,rolling force parameters.The results show that:(1)when the rotational speed of driver roll n increases,the strain distribution of the rolled ring becomes less homogeneous,and the temperature distribution more homogeneous yet,and leading to an optimal n value;(2)the fishtail coefficient firstly decreases,then increases with the increase of n;(3)the rolling force,contact area and rolling moment gradually descend with the increase of n.
基金financially supported by the State Key Laboratory of Advanced Welding and Joining of China (No.AWJ-Z16-02)
文摘In this study, 5052 steel were joined by a new way aluminum alloy and Q235 of arc milling brazing, with the Zn15%A1 filler metal and no use of flux. Effect of rotation speed on mechanical properties and microstructure of joint interface was investigated. The results show that increasing rotation speed is in favor of formation of weld and spread of filler metal on substrate. The fine grain with homogeneous composition in brazed seam can be realized by the stronger stirring in pool induced by milling at more higher rotation speed. And, a composite joint reinforced with needle-like or block-like Fe-A1-Zn intermetallic compounds （IMCs） particle can be obtained by arc milling brazing, which comes from the reaction between steel scrape and Zn-A1 filler alloy. The test on strength of joint interface shows that with the increase in rotation speed, there is a peak value in variation ranges of strength of joint interface. This is to say, when rotation speed is 2720 r.min-~, the strength of joint has maximum value （182.01 MPa）. Moreover, a thin and discontinuous IMCs layer at joint interface can be obtained by increasing rotation speed. But at a low or high rotation speed, there also is a crack at joint interface, which weakens the strength of joint interface. Only at 2720 r.min-1, a good joint interface without an obvious crack can be realized.
基金Shanxi Scholarship Council of China(2022-141)Fundamental Research Program of Shanxi Province(202203021211096).
文摘Recent research in cross-domain intelligence fault diagnosis of machinery still has some problems,such as relatively ideal speed conditions and sample conditions.In engineering practice,the rotational speed of the machine is often transient and time-varying,which makes the sample annotation increasingly expensive.Meanwhile,the number of samples collected from different health states is often unbalanced.To deal with the above challenges,a complementary-label(CL)adversarial domain adaptation fault diagnosis network(CLADAN)is proposed under time-varying rotational speed and weakly-supervised conditions.In the weakly supervised learning condition,machine prior information is used for sample annotation via cost-friendly complementary label learning.A diagnosticmodel learning strategywith discretized category probabilities is designed to avoidmulti-peak distribution of prediction results.In adversarial training process,we developed virtual adversarial regularization(VAR)strategy,which further enhances the robustness of the model by adding adversarial perturbations in the target domain.Comparative experiments on two case studies validated the superior performance of the proposed method.
文摘In order to apply grinding method for degradation of pentachlorophenol(PCP) to an industrial scale,the proportion of different materials[CaO,SiO_2 and CO(NH_2)_2]and the size of grinding balls were examined.For saving energy and increasing dechlorination efficiency,the rotation speed and grinding time were maintained at relatively low values.At a mass ratio of grinding balls to materials(40:1),PCP was added into a big steel jar(300 ml) with other materials to grind at 300 r ·min^(-1)for 5 h.The results indicated that when PCP was mixed with CaO and SiO_2in a molar ratio of 1:60:60,the best dechlorination of 58.4%was achieved.CO(NH_2)_2 could not be used as hydrogen donor in the dehalogenation by mechanochemical reaction,since it restrained the dechlorination process.The size of grinding balls has significant effect on the reaction.The experiment with 5 mm steel balls indicates that the weight is too light to provide appropriate energy for the reaction,while steel balls of 10 and 15 mm could give better dechlorination reaction.It indicates that dechlorination depends on the mass of balls and fill rate.
