A three-dimensional conjugate tooth surface design method for Harmonic Drive with a double-circular-arc tooth profle is proposed. The radial deformation function of the fexspline (FS), obtained through Finite Element ...A three-dimensional conjugate tooth surface design method for Harmonic Drive with a double-circular-arc tooth profle is proposed. The radial deformation function of the fexspline (FS), obtained through Finite Element (FE) analysis, is incorporated into the kinematics model. By analyzing the FS tooth enveloping process, the optimization of the overlapping conjugate tooth profle is achieved. By utilizing the hobbing process, the three-dimensional machinable tooth surface of FS can be acquired. Utilizing the coning deformation of the FS, simulations are conducted to analyze the multi-section assembly and meshing motion of the machinable tooth surface. The FE method is utilized to analyze and compare the loaded contact characteristics. Results demonstrate that the proposed design method can achieve an internal gear pair consisting of a circular spline with a spur gear tooth surface and the FS with a machinable tooth surface. With the rated torque, approximately 24% of the FS teeth are engaged in meshing, and more than 4/5 of the tooth surface in the axial direction carries the load. The contact patterns, maximum contact pressure, and transmission error of the machinable tooth surface are 227.2%, 40.67%, and 71.24% of those on the spur gear tooth surface, respectively. It clearly demonstrates exceptional transmission performance.展开更多
Aviation spiral bevel gears are often generated by spiral generated modified(SGM) roll method.In this style,pinion tooth surface modified generation strategy has an important influence on the meshing and contact per...Aviation spiral bevel gears are often generated by spiral generated modified(SGM) roll method.In this style,pinion tooth surface modified generation strategy has an important influence on the meshing and contact performances.For the optimal contact pattern and transmission error function,local synthesis is applied to obtain the machine-tool settings of pinion.For digitized machine,four tooth surface generation styles of pinion are proposed.For every style,tooth contact analysis(TCA) is applied to obtain contact pattern and transmission error function.For the difference between TCA transmission error function and design objective curve,the degree of symmetry and agreement are defined and the corresponding sub-objective functions are established.Linear weighted combination method is applied to get an equivalent objective function to evaluate the shape of transmission error function.The computer programs for the process above are developed to analyze the meshing performances of the four pinion tooth surface generation styles for a pair of aviation spiral bevel gears with 38/43 teeth numbers.The four analytical results are compared with each other and show that the incomplete modified roll is optimal for this gear pair.This study is an expansion to generation strategy of spiral bevel gears,and offers new alternatives to computer numerical control(CNC) manufacture of spiral bevel gears.展开更多
In order to generate the digital gear tooth surfaces(DGTS)with high efficiency and high precision,a method for identification and compensation of machining errors is demonstrated in this paper.Machining errors are ana...In order to generate the digital gear tooth surfaces(DGTS)with high efficiency and high precision,a method for identification and compensation of machining errors is demonstrated in this paper.Machining errors are analyzed directly from the real tooth surfaces.The topography data of the part are off-line measured in the post-process.A comparison is made between two models:CAD model of DGTS and virtual model of the physical measured surface.And a matching rule is given to determine these two surfaces in an appropriate fashion.The developed error estimation model creates a point-to-point map of the real surface to the theoretical surface in the normal direction.A“pre-calibration error compensation”strategy is presented.Through processing the results of the first trail cutting,the total compensation error is predicted and an imaginary digital tooth surface is reconstructed. The machining errors in the final manufactured surfaces are minimized by generating this imaginary surface.An example of ma- chining 2-D DGTS verifies the developed method.The research is of important theoretical and practical value to manufacture the DGTS and other digital conjugate surfaces.展开更多
According to the principle of meshing engagement and the theory of the digitized conjugate surface, this paper applies the software Conjugater-1.0 that is developed by ourselves to compute, respectively, the digitized...According to the principle of meshing engagement and the theory of the digitized conjugate surface, this paper applies the software Conjugater-1.0 that is developed by ourselves to compute, respectively, the digitized conjugate curved surfaces of the straight-tooth surface and drum-tooth surface, which will establish the theoretical and technical foundation for digitized engaging analysis, simulation, and digitized manufacturing technology of the diversified gears.展开更多
Tooth modification technique is widely used in gear industry to improve the meshing performance of gearings. However, few of the present studies on tooth modification considers the influence of inevitable random error...Tooth modification technique is widely used in gear industry to improve the meshing performance of gearings. However, few of the present studies on tooth modification considers the influence of inevitable random errors on gear modification effects. In order to investigate the uncertainties of tooth modification amount variations on system's dynamic behaviors of a helical planetary gears, an analytical dynamic model including tooth modification parameters is proposed to carry out a deterministic analysis on the dynamics of a helical planetary gear. The dynamic meshing forces as well as the dynamic transmission errors of the sun-planet 1 gear pair with and without tooth modifications are computed and compared to show the effectiveness of tooth modifications on gear dynamics enhancement. By using response surface method, a fitted regression model for the dynamic transmission error(DTE) fluctuations is established to quantify the relationship between modification amounts and DTE fluctuations. By shifting the inevitable random errors arousing from manufacturing and installing process to tooth modification amount variations, a statistical tooth modification model is developed and a methodology combining Monte Carlo simulation and response surface method is presented for uncertainty analysis of tooth modifications. The uncertainly analysis reveals that the system's dynamic behaviors do not obey the normal distribution rule even though the design variables are normally distributed. In addition, a deterministic modification amount will not definitely achieve an optimal result for both static and dynamic transmission error fluctuation reduction simultaneously.展开更多
Due to the excellent self-centering and load-carrying capability,curvic couplings have been widely used in advanced aero-engine rotors.However,curvic tooth surface errors lead to poor assembly precision.Traditional ph...Due to the excellent self-centering and load-carrying capability,curvic couplings have been widely used in advanced aero-engine rotors.However,curvic tooth surface errors lead to poor assembly precision.Traditional physical-master-gauge-based indirect tooth surface error measurement and circumferential assembly angle optimization methods have the disadvantages of high cost and weak generality.The unknown tooth surface fitting mechanism is a big barrier to assembly precision prediction and improvement.Therefore,this work puts forward a data-driven assembly simulation and optimization approach for aero-engine rotors connected by curvic couplings.The origin of curvic tooth surface error is deeply investigated.Using 5-axis sweep scan method,a large amount of high-precision curvic tooth surface data are acquired efficiently.Based on geometric models of parts,the fitting mechanism of curvic couplings is uncovered for assembly precision simulation and prediction.A circumferential assembly angle optimization model is developed to decrease axial and radial assembly runouts.Experimental results show that the assembly precision can be predicted accurately and improved dramatically.By uncovering the essential principle of the assembly precision formation and proposing circumferential assembly angle optimization model,this work is meaningful for assembly quality,efficiency and economy improvement of multistage aero-engine rotors connected by curvic couplings.展开更多
According to the defect of traditional method of determining instantaneous contact regions for conjugate surfaces, a numerical approach to the determination is proposed. A local coordinate system is built by using the...According to the defect of traditional method of determining instantaneous contact regions for conjugate surfaces, a numerical approach to the determination is proposed. A local coordinate system is built by using the surface unit tangent and unit normal at the contact point. Considering that the gap forming the boundary of instantaneous contact region in the direction of the common normal vectors is given, a system of nonlinear equations is built to find the instantaneous contact boundary in local coordinate system, a modified Powell's hybrid algorithm of finite-difference approximation to the Jacobian used to solve the system. The new method simplifies the task of determining instantaneous contact regions without calculating curvatm'e and relative curvature. The validity of the proposed approach is verified by an example of hypoid gears.展开更多
<span style="font-family:Verdana;"></span><span style="font-family:Verdana;">This study aimed to describe the factors associated with biofilms formation in dental pathology by com...<span style="font-family:Verdana;"></span><span style="font-family:Verdana;">This study aimed to describe the factors associated with biofilms formation in dental pathology by comparison of bacterial growth on dental and stainless-steel surfaces.</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">We studied </span><i><span style="font-family:Verdana;">in vitro</span></i><span style="font-family:Verdana;"> the behavior of </span><i><span style="font-family:Verdana;">Staphylococcus aureus Méti</span></i><span style="font-family:Verdana;">s in order to observe the capacity of adhesion, to evaluate quantitatively the potential of proliferation and to compare the behavior of this germ in contact with the two surfaces.</span></span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">The biomaterials used were cylinders in Stainless steel (AISI 316L), dental fragments and stainless-steel fragments, all were disinfected for 15 minutes and then sterilized in a wet autoclave at 120<span style="white-space:nowrap;">˚</span></span><span style="font-family:;" "=""><span style="font-family:Verdana;">C for 30 min. Macroscopic observation with a binocular magnifier of bacterial proliferation was carried out regularly after 6 h and 24 h of incubation. Observation by optical microscope based on GRAM staining made it possible to visualize the presence or absence of bacteria and to differentiate them. The adhesion of </span><i><span style="font-family:Verdana;">Staphylococcus aureus Méti S</span></i><span style="font-family:Verdana;"> on dental fragments was compared to </span><span style="font-family:Verdana;">the one obtained on stainless steel fragments. We also carried a Bacterial</span><span style="font-family:Verdana;"> count by optical dosing.</span></span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">The results show that the ability of this germ to colonize and develop biofilms on surfaces depends mainly on the characteristics of the surface. Rough surfaces as dental surface are more likely to developing biofilms than smooth surfaces like stainless-steel surface.</span>展开更多
The lubrication basis theory of worm pair is given. The lubrication state of worm gear is analyzed. It is found that the temperature distribution on the tooth surface of worm gear is closely related with the lubricati...The lubrication basis theory of worm pair is given. The lubrication state of worm gear is analyzed. It is found that the temperature distribution on the tooth surface of worm gear is closely related with the lubrication state and that the temperature on the tooth surface of worm gear is consistent with the characteristic term of mesh and motion of worm pair.展开更多
齿面点蚀是一种典型的行星齿轮系统故障。为识别点蚀状态,本文开展动力学特性研究并提出了一种新型的评估指标。首先,虑及过渡曲线和齿间结构耦合效应,利用改进Weber法建立了精确的含点蚀故障齿轮副啮合刚度模型,并研究了故障程度对啮...齿面点蚀是一种典型的行星齿轮系统故障。为识别点蚀状态,本文开展动力学特性研究并提出了一种新型的评估指标。首先,虑及过渡曲线和齿间结构耦合效应,利用改进Weber法建立了精确的含点蚀故障齿轮副啮合刚度模型,并研究了故障程度对啮合刚度的影响规律。然后,综合考虑时变啮合刚度、静态传动误差、齿侧间隙和时变振动传递路径等多种因素构建了行星齿轮系统平移-扭转动力学模型,揭示了点蚀程度对系统动态特性的影响规律,并基于振动信号频谱特点提出了边带能量因子(Sideband Energy Factor,SEF)用于损伤评估。最后,利用实验验证了仿真模型的正确性及所提指标的有效性。展开更多
基金Supported by Guangdong Provincial Key-Area Research and Development Program(Grant No.2019B090917002).
文摘A three-dimensional conjugate tooth surface design method for Harmonic Drive with a double-circular-arc tooth profle is proposed. The radial deformation function of the fexspline (FS), obtained through Finite Element (FE) analysis, is incorporated into the kinematics model. By analyzing the FS tooth enveloping process, the optimization of the overlapping conjugate tooth profle is achieved. By utilizing the hobbing process, the three-dimensional machinable tooth surface of FS can be acquired. Utilizing the coning deformation of the FS, simulations are conducted to analyze the multi-section assembly and meshing motion of the machinable tooth surface. The FE method is utilized to analyze and compare the loaded contact characteristics. Results demonstrate that the proposed design method can achieve an internal gear pair consisting of a circular spline with a spur gear tooth surface and the FS with a machinable tooth surface. With the rated torque, approximately 24% of the FS teeth are engaged in meshing, and more than 4/5 of the tooth surface in the axial direction carries the load. The contact patterns, maximum contact pressure, and transmission error of the machinable tooth surface are 227.2%, 40.67%, and 71.24% of those on the spur gear tooth surface, respectively. It clearly demonstrates exceptional transmission performance.
文摘Aviation spiral bevel gears are often generated by spiral generated modified(SGM) roll method.In this style,pinion tooth surface modified generation strategy has an important influence on the meshing and contact performances.For the optimal contact pattern and transmission error function,local synthesis is applied to obtain the machine-tool settings of pinion.For digitized machine,four tooth surface generation styles of pinion are proposed.For every style,tooth contact analysis(TCA) is applied to obtain contact pattern and transmission error function.For the difference between TCA transmission error function and design objective curve,the degree of symmetry and agreement are defined and the corresponding sub-objective functions are established.Linear weighted combination method is applied to get an equivalent objective function to evaluate the shape of transmission error function.The computer programs for the process above are developed to analyze the meshing performances of the four pinion tooth surface generation styles for a pair of aviation spiral bevel gears with 38/43 teeth numbers.The four analytical results are compared with each other and show that the incomplete modified roll is optimal for this gear pair.This study is an expansion to generation strategy of spiral bevel gears,and offers new alternatives to computer numerical control(CNC) manufacture of spiral bevel gears.
文摘In order to generate the digital gear tooth surfaces(DGTS)with high efficiency and high precision,a method for identification and compensation of machining errors is demonstrated in this paper.Machining errors are analyzed directly from the real tooth surfaces.The topography data of the part are off-line measured in the post-process.A comparison is made between two models:CAD model of DGTS and virtual model of the physical measured surface.And a matching rule is given to determine these two surfaces in an appropriate fashion.The developed error estimation model creates a point-to-point map of the real surface to the theoretical surface in the normal direction.A“pre-calibration error compensation”strategy is presented.Through processing the results of the first trail cutting,the total compensation error is predicted and an imaginary digital tooth surface is reconstructed. The machining errors in the final manufactured surfaces are minimized by generating this imaginary surface.An example of ma- chining 2-D DGTS verifies the developed method.The research is of important theoretical and practical value to manufacture the DGTS and other digital conjugate surfaces.
文摘According to the principle of meshing engagement and the theory of the digitized conjugate surface, this paper applies the software Conjugater-1.0 that is developed by ourselves to compute, respectively, the digitized conjugate curved surfaces of the straight-tooth surface and drum-tooth surface, which will establish the theoretical and technical foundation for digitized engaging analysis, simulation, and digitized manufacturing technology of the diversified gears.
基金Supported by National Natural Science Foundation of China(Grant No.51375013)Anhui Provincial Natural Science Foundation of China(Grant No.1208085ME64)
文摘Tooth modification technique is widely used in gear industry to improve the meshing performance of gearings. However, few of the present studies on tooth modification considers the influence of inevitable random errors on gear modification effects. In order to investigate the uncertainties of tooth modification amount variations on system's dynamic behaviors of a helical planetary gears, an analytical dynamic model including tooth modification parameters is proposed to carry out a deterministic analysis on the dynamics of a helical planetary gear. The dynamic meshing forces as well as the dynamic transmission errors of the sun-planet 1 gear pair with and without tooth modifications are computed and compared to show the effectiveness of tooth modifications on gear dynamics enhancement. By using response surface method, a fitted regression model for the dynamic transmission error(DTE) fluctuations is established to quantify the relationship between modification amounts and DTE fluctuations. By shifting the inevitable random errors arousing from manufacturing and installing process to tooth modification amount variations, a statistical tooth modification model is developed and a methodology combining Monte Carlo simulation and response surface method is presented for uncertainty analysis of tooth modifications. The uncertainly analysis reveals that the system's dynamic behaviors do not obey the normal distribution rule even though the design variables are normally distributed. In addition, a deterministic modification amount will not definitely achieve an optimal result for both static and dynamic transmission error fluctuation reduction simultaneously.
基金co-supported by the National Basic Research Project(Nos.J2022-VII-0001-0043 and 2017-VII-0010-0104)the Fundamental Research Funds for the Central Universities,and the National Natural Science Foundation of China(No.72231008)。
文摘Due to the excellent self-centering and load-carrying capability,curvic couplings have been widely used in advanced aero-engine rotors.However,curvic tooth surface errors lead to poor assembly precision.Traditional physical-master-gauge-based indirect tooth surface error measurement and circumferential assembly angle optimization methods have the disadvantages of high cost and weak generality.The unknown tooth surface fitting mechanism is a big barrier to assembly precision prediction and improvement.Therefore,this work puts forward a data-driven assembly simulation and optimization approach for aero-engine rotors connected by curvic couplings.The origin of curvic tooth surface error is deeply investigated.Using 5-axis sweep scan method,a large amount of high-precision curvic tooth surface data are acquired efficiently.Based on geometric models of parts,the fitting mechanism of curvic couplings is uncovered for assembly precision simulation and prediction.A circumferential assembly angle optimization model is developed to decrease axial and radial assembly runouts.Experimental results show that the assembly precision can be predicted accurately and improved dramatically.By uncovering the essential principle of the assembly precision formation and proposing circumferential assembly angle optimization model,this work is meaningful for assembly quality,efficiency and economy improvement of multistage aero-engine rotors connected by curvic couplings.
基金National Education Dep.of China (No. 20060056016)National Hi-tech Research and Development Program of China(863 Program, No. 2007AA042005, No. 2006AA 04Z146).
文摘According to the defect of traditional method of determining instantaneous contact regions for conjugate surfaces, a numerical approach to the determination is proposed. A local coordinate system is built by using the surface unit tangent and unit normal at the contact point. Considering that the gap forming the boundary of instantaneous contact region in the direction of the common normal vectors is given, a system of nonlinear equations is built to find the instantaneous contact boundary in local coordinate system, a modified Powell's hybrid algorithm of finite-difference approximation to the Jacobian used to solve the system. The new method simplifies the task of determining instantaneous contact regions without calculating curvatm'e and relative curvature. The validity of the proposed approach is verified by an example of hypoid gears.
文摘<span style="font-family:Verdana;"></span><span style="font-family:Verdana;">This study aimed to describe the factors associated with biofilms formation in dental pathology by comparison of bacterial growth on dental and stainless-steel surfaces.</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">We studied </span><i><span style="font-family:Verdana;">in vitro</span></i><span style="font-family:Verdana;"> the behavior of </span><i><span style="font-family:Verdana;">Staphylococcus aureus Méti</span></i><span style="font-family:Verdana;">s in order to observe the capacity of adhesion, to evaluate quantitatively the potential of proliferation and to compare the behavior of this germ in contact with the two surfaces.</span></span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">The biomaterials used were cylinders in Stainless steel (AISI 316L), dental fragments and stainless-steel fragments, all were disinfected for 15 minutes and then sterilized in a wet autoclave at 120<span style="white-space:nowrap;">˚</span></span><span style="font-family:;" "=""><span style="font-family:Verdana;">C for 30 min. Macroscopic observation with a binocular magnifier of bacterial proliferation was carried out regularly after 6 h and 24 h of incubation. Observation by optical microscope based on GRAM staining made it possible to visualize the presence or absence of bacteria and to differentiate them. The adhesion of </span><i><span style="font-family:Verdana;">Staphylococcus aureus Méti S</span></i><span style="font-family:Verdana;"> on dental fragments was compared to </span><span style="font-family:Verdana;">the one obtained on stainless steel fragments. We also carried a Bacterial</span><span style="font-family:Verdana;"> count by optical dosing.</span></span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">The results show that the ability of this germ to colonize and develop biofilms on surfaces depends mainly on the characteristics of the surface. Rough surfaces as dental surface are more likely to developing biofilms than smooth surfaces like stainless-steel surface.</span>
文摘The lubrication basis theory of worm pair is given. The lubrication state of worm gear is analyzed. It is found that the temperature distribution on the tooth surface of worm gear is closely related with the lubrication state and that the temperature on the tooth surface of worm gear is consistent with the characteristic term of mesh and motion of worm pair.
文摘齿面点蚀是一种典型的行星齿轮系统故障。为识别点蚀状态,本文开展动力学特性研究并提出了一种新型的评估指标。首先,虑及过渡曲线和齿间结构耦合效应,利用改进Weber法建立了精确的含点蚀故障齿轮副啮合刚度模型,并研究了故障程度对啮合刚度的影响规律。然后,综合考虑时变啮合刚度、静态传动误差、齿侧间隙和时变振动传递路径等多种因素构建了行星齿轮系统平移-扭转动力学模型,揭示了点蚀程度对系统动态特性的影响规律,并基于振动信号频谱特点提出了边带能量因子(Sideband Energy Factor,SEF)用于损伤评估。最后,利用实验验证了仿真模型的正确性及所提指标的有效性。