Tooth breakage is a common issue in geared systems. The high-contact-ratio spur gear system (HCRSG) maintains continuoustransmission despite tooth breakage, but experiences increased impact vibration. In aviation, eve...Tooth breakage is a common issue in geared systems. The high-contact-ratio spur gear system (HCRSG) maintains continuoustransmission despite tooth breakage, but experiences increased impact vibration. In aviation, even if the gear teeth break, the gear'stransmission cannot be stopped immediately. Therefore, studying gear system dynamics with tooth breakage is crucial for assessing thereliability of mechanical equipment. This study treats the tooth-back contact induced by backlash as the tooth-back collision andpresents the multi-state meshing-collision pattern of HCRSG with one tooth breakage (OTB), including triple-tooth, double-tooth,single-tooth meshes, disengagement, and tooth-back collision. Time-varying meshing stiffness and load distribution coefficients ofHCRSG with OTB are calculated. Then a multi-state meshing-collision nonlinear dynamic model of HCRSG with OTB is established.The meshing forces of HCRSG with OTB and without OTB are calculated and compared to examine the effect of tooth breakage. Themulti-state meshing-collision nonlinear dynamics of HCRSG with OTB are studied via bifurcation diagram, phase portraits, andPoincaré maps by changing the transmission error amplitude. The results show that 3-2-3-2-3 meshing pattern of HCRSG is shifted to2-1-2-1-2 meshing pattern due to tooth breakage. The effect of tooth breakage on the meshing force and dynamic behavior significantlydepends on teeth disengagement or tooth-back collision. Tooth breakage greatly affects the bifurcation and chaos characteristics ofmultistate meshing-collision behavior of HCRSG. This study creates a framework to predict and assess the dynamics of gear transmissionsystems with tooth breakage in extreme aviation and aerospace environments.展开更多
The gear transmission system is a pivotal power transmission subsystem in locomotives,which operates under high load torque and complex external disturbance conditions.Due to neglecting the extended teeth contact caus...The gear transmission system is a pivotal power transmission subsystem in locomotives,which operates under high load torque and complex external disturbance conditions.Due to neglecting the extended teeth contact caused by gear deformation under load torque,the existing dynamic models of locomotive gear transmission systems lack sufficient precision and have limited dynamic analysis capability.Therefore,this paper proposes an improved dynamic model of the locomotive gear transmission system,which includes the fine gear meshing and locomotive-track coupling models.Notably,the gear meshing model is finely modeled to consider extended tooth contact,gear elasticity,and the structural coupling effect.The motion equations of the wheelset and motor-gearbox affected by extended teeth contact are also established.Then,the established dynamic model of the gear transmission system is experimentally verified.Finally,the effect mechanism of extended teeth contact on the vibration response of the wheelset and motor-gearbox is disclosed.The multi-state mesh,load distribution between teeth,and nonlinear dynamics of the gear transmission system are studied under different locomotive velocities,polygonal wheels,and tooth pitch deviations.The results show that the extended teeth contact will reduce the vibration acceleration of the wheelset and motor-gearbox through the smooth tooth contact force during the alternation process between single-tooth and double-tooth mesh.Both internal and external excitations cause multi-state mesh and nonlinear dynamic behavior in gear transmission systems,including varying degrees of extended teeth contact,tooth disengagement,back-side contact,and phase trajectory expansion.This study offers a theoretical and methodological reference for the comprehensive dynamic evaluation of locomotive gear transmission systems.展开更多
Integration of natural gas and electricity transmission systems has strengthened interdependence between the two systems.Due to the close interconnection through coupling elements between the power system(PS)and natur...Integration of natural gas and electricity transmission systems has strengthened interdependence between the two systems.Due to the close interconnection through coupling elements between the power system(PS)and natural gas system(NGS)when a disturbance happens in one system,a series of complicated sequences of dependent events may follow in another system.Therefore,an integrated planning model jointing security-constrained considering cascading effects is proposed in this paper.Meanwhile,natural gas and electricity transmission systems considering stochastic failures and various operating characteristics of components can be viewed as a multistate systems.Moreover,power-to-gas(P2G),as a promising technology proposed to store surplus renewable energy,is considered in the integrated planning.First,multi-state models for different components are developed to describe realistic operating conditions in natural gas and electricity transmission systems.Furthermore,a mixed-integer linear programming(MILP)approach considers N-1 contingency and cascading effects between natural gas and the electrical power systems.Therefore,a security-constrained integrated planning model of natural gas and electricity transmission systems is represented.The proposed methods are validated using an integrated gas and power test system.展开更多
A Hybrid Free-Form Deformation(HFFD)method is developed to improve shape preservation in mesh deformation for perforated surfaces,which traditional Free-Form Deformation(FFD)techniques struggle to handle effectively.T...A Hybrid Free-Form Deformation(HFFD)method is developed to improve shape preservation in mesh deformation for perforated surfaces,which traditional Free-Form Deformation(FFD)techniques struggle to handle effectively.The proposed method enables high-fidelity parameterized deformation for both flat and curved perforated surfaces while maintaining mesh quality with minimal geometric distortion.To evaluate its effectiveness,comparative studies between HFFD and conventional FFD methods are conducted,demonstrating superior performance in mesh quality and geometric fidelity.The HFFD-based framework is further applied to the Multidisciplinary Design Optimization(MDO)of a double-wall turbine blade leading edge.Results indicate an 11.6%increase in cooling efficiency and a 16.21%reduction in maximum stress.Additionally,compared to traditional geometry-based parameterization in MDO,the HFFD approach improves model processing efficiency by 84.15%and overall optimization efficiency by20.05%.These findings demonstrate HFFD's potential to significantly improve complex engineering design optimization by achieving precise shape preservation and improving computational efficiency.展开更多
Mesh models are among the primary representations for storing 3-D objects,encapsulating detailed geometric information.3-D mesh watermarking,in particular,plays a central role in the protection of 3-D content.However,...Mesh models are among the primary representations for storing 3-D objects,encapsulating detailed geometric information.3-D mesh watermarking,in particular,plays a central role in the protection of 3-D content.However,frequency-domain methods rely on complex parameterization and spectral decomposition,which are sensitive to mesh topology and resolution and often introduce perceptible artifacts.Spatial-domain techniques,on the other hand,typically embed watermarks in global or randomly selected regions,leading to visible distortions and reduced robustness.To address the above limitations and protect model copyright without compromising the original aesthetic quality,we propose a deterministice PCA-synchronized 3Dmeshwatermarkingmethodwith fullerene-guided carrier selection.First,a deterministic principal component analysis(PCA)-based mesh synchronization algorithm is employed to align the models to a canonical pose.Next,a fullerene-inspired carrier selection strategy is employed to determine the watermark carriers,leveraging the structural characteristics of fullerene molecules to achieve a more rational and effective carrier selection.Finally,to balance the embedding strength and enhance visual quality,the watermark information is embedded using an APQIM(Adaptive Parity-Check Quantization Index Modulation)scheme.The experimental results show that our method can achieve high visual quality with scalable capacity and strong robustness compared with existing methods.The watermarking scheme can resist various attacks,including simplification,smoothing,Gaussian noise,translation,and rotation.展开更多
This paper studies high order compact finite volume methods on non-uniform meshes for one-dimensional elliptic and parabolic differential equations with the Robin boundary conditions.An explicit scheme and an implicit...This paper studies high order compact finite volume methods on non-uniform meshes for one-dimensional elliptic and parabolic differential equations with the Robin boundary conditions.An explicit scheme and an implicit scheme are obtained by discretizing the equivalent integral form of the equation.For the explicit scheme with nodal values,the algebraic system can be solved by the Thomas method.For the implicit scheme with both nodal values and their derivatives,the system can be implemented by a prediction-correction procedure,where in the correction stage,an implicit formula for recovering the nodal derivatives is introduced.Taking two point boundary value problem as an example,we prove that both the explicit and implicit schemes are convergent with fourth order accuracy with respect to some standard discrete norms using the energy method.Two numerical examples demonstrate the correctness and effectiveness of the schemes,as well as the indispensability of using non-uniform meshes.展开更多
Computing electrostatic interaction on non-cooperative targets with unknown meshes is crucial for electrostatic-based space on-orbit services.Although meshes for electrostatic interaction computations can be reconstru...Computing electrostatic interaction on non-cooperative targets with unknown meshes is crucial for electrostatic-based space on-orbit services.Although meshes for electrostatic interaction computations can be reconstructed from point clouds,they are usually too dense,leading to high computational costs.This paper presents an optimization method for converting dense meshes into optimal meshes,enabling fast and accurate computation of the electrostatic interaction by point clouds.First,the dense mesh reconstructed from point clouds is simplified into a coarse mesh using local operators.Second,the simplified mesh is refined by an iterative strategy that integrates a lightweight method of moments and an impedance matrix inheritance technique,ultimately yielding an optimal mesh for computing the electrostatic interaction.Simulation results show that our method effectively optimizes dense meshes,making electrostatic interaction computations using point clouds approximately 63.4 times more efficient than the previous method.展开更多
In the traditional reliability evaluation based on the Bayesian method,the failure probability of nodes is usually expressed by the average failure rate within a period of time.Aiming at the shortcomings of traditiona...In the traditional reliability evaluation based on the Bayesian method,the failure probability of nodes is usually expressed by the average failure rate within a period of time.Aiming at the shortcomings of traditional Bayesian network reliability evaluation methods,this paper proposes a Bayesian network reliability evaluation method considering dynamics and fuzziness.The fuzzy theory and the dynamic of component failure probability are introduced to construct the dynamic fuzzy set function.Based on the solving characteristics of the dynamic fuzzy set and Bayesian network,the fuzzy dynamic probability and fuzzy dynamic importance degree of the fault state of leaf nodes are solved.Finally,through the dynamic fuzzy reliability analysis of CNC machine tool hydraulic system balance circuit,the application of this method in system reliability evaluation is verified,which provides support for fault diagnosis of CNC machine tools.展开更多
Importance measures in reliability systems are used to identify weak components in contributing to a proper function of the system.Traditional importance measures mainly concerned the changing value of the system reli...Importance measures in reliability systems are used to identify weak components in contributing to a proper function of the system.Traditional importance measures mainly concerned the changing value of the system reliability caused by the change of the reliability of the component,and seldom considered the joint effect of the probability distribution,improvement rate of the object component.This paper studies the rate of the system reliability upgrading with an improvement of the component reliability for the multi-state consecutive k-out-of-n system.To verify the multi-state consecutive k-out-of-n system reliability upgrading by improving one component based on its improvement rate,an increasing potential importance(IPI)and its physical meaning are described at first.Secondly,the relationship between the IPI and Birnbaum importance measures are discussed.And the IPI for some different improvement actions of the component is further discussed.Thirdly,the characteristics of the IPI are analyzed.Finally,an application to an oil pipeline system is given.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12102159,12462003)the Lanzhou Youth Science and Technology Talent Innovation Project(2023-QN-39)the postgraduate research exploration project(222080201023).
文摘Tooth breakage is a common issue in geared systems. The high-contact-ratio spur gear system (HCRSG) maintains continuoustransmission despite tooth breakage, but experiences increased impact vibration. In aviation, even if the gear teeth break, the gear'stransmission cannot be stopped immediately. Therefore, studying gear system dynamics with tooth breakage is crucial for assessing thereliability of mechanical equipment. This study treats the tooth-back contact induced by backlash as the tooth-back collision andpresents the multi-state meshing-collision pattern of HCRSG with one tooth breakage (OTB), including triple-tooth, double-tooth,single-tooth meshes, disengagement, and tooth-back collision. Time-varying meshing stiffness and load distribution coefficients ofHCRSG with OTB are calculated. Then a multi-state meshing-collision nonlinear dynamic model of HCRSG with OTB is established.The meshing forces of HCRSG with OTB and without OTB are calculated and compared to examine the effect of tooth breakage. Themulti-state meshing-collision nonlinear dynamics of HCRSG with OTB are studied via bifurcation diagram, phase portraits, andPoincaré maps by changing the transmission error amplitude. The results show that 3-2-3-2-3 meshing pattern of HCRSG is shifted to2-1-2-1-2 meshing pattern due to tooth breakage. The effect of tooth breakage on the meshing force and dynamic behavior significantlydepends on teeth disengagement or tooth-back collision. Tooth breakage greatly affects the bifurcation and chaos characteristics ofmultistate meshing-collision behavior of HCRSG. This study creates a framework to predict and assess the dynamics of gear transmissionsystems with tooth breakage in extreme aviation and aerospace environments.
基金supported by the National Key R&D Program of China(Grant No.2023YFB2604303)the National Natural Science Foundation of China(Grant No.52388102)the Sichuan Science and Technology Program(Grant No.2024NSFTD0011)。
文摘The gear transmission system is a pivotal power transmission subsystem in locomotives,which operates under high load torque and complex external disturbance conditions.Due to neglecting the extended teeth contact caused by gear deformation under load torque,the existing dynamic models of locomotive gear transmission systems lack sufficient precision and have limited dynamic analysis capability.Therefore,this paper proposes an improved dynamic model of the locomotive gear transmission system,which includes the fine gear meshing and locomotive-track coupling models.Notably,the gear meshing model is finely modeled to consider extended tooth contact,gear elasticity,and the structural coupling effect.The motion equations of the wheelset and motor-gearbox affected by extended teeth contact are also established.Then,the established dynamic model of the gear transmission system is experimentally verified.Finally,the effect mechanism of extended teeth contact on the vibration response of the wheelset and motor-gearbox is disclosed.The multi-state mesh,load distribution between teeth,and nonlinear dynamics of the gear transmission system are studied under different locomotive velocities,polygonal wheels,and tooth pitch deviations.The results show that the extended teeth contact will reduce the vibration acceleration of the wheelset and motor-gearbox through the smooth tooth contact force during the alternation process between single-tooth and double-tooth mesh.Both internal and external excitations cause multi-state mesh and nonlinear dynamic behavior in gear transmission systems,including varying degrees of extended teeth contact,tooth disengagement,back-side contact,and phase trajectory expansion.This study offers a theoretical and methodological reference for the comprehensive dynamic evaluation of locomotive gear transmission systems.
基金supported in part by the Key Projects of National Natural Science Foundation of China under Grant 51936003.
文摘Integration of natural gas and electricity transmission systems has strengthened interdependence between the two systems.Due to the close interconnection through coupling elements between the power system(PS)and natural gas system(NGS)when a disturbance happens in one system,a series of complicated sequences of dependent events may follow in another system.Therefore,an integrated planning model jointing security-constrained considering cascading effects is proposed in this paper.Meanwhile,natural gas and electricity transmission systems considering stochastic failures and various operating characteristics of components can be viewed as a multistate systems.Moreover,power-to-gas(P2G),as a promising technology proposed to store surplus renewable energy,is considered in the integrated planning.First,multi-state models for different components are developed to describe realistic operating conditions in natural gas and electricity transmission systems.Furthermore,a mixed-integer linear programming(MILP)approach considers N-1 contingency and cascading effects between natural gas and the electrical power systems.Therefore,a security-constrained integrated planning model of natural gas and electricity transmission systems is represented.The proposed methods are validated using an integrated gas and power test system.
基金supported by the National Science and Technology Major Project,China(No.2017-II-0006-0019)the National Natural Science Foundation of China(No.52375266)the Shaanxi Science Foundation for Distinguished Young Scholars,China(No.2022JC-36)。
文摘A Hybrid Free-Form Deformation(HFFD)method is developed to improve shape preservation in mesh deformation for perforated surfaces,which traditional Free-Form Deformation(FFD)techniques struggle to handle effectively.The proposed method enables high-fidelity parameterized deformation for both flat and curved perforated surfaces while maintaining mesh quality with minimal geometric distortion.To evaluate its effectiveness,comparative studies between HFFD and conventional FFD methods are conducted,demonstrating superior performance in mesh quality and geometric fidelity.The HFFD-based framework is further applied to the Multidisciplinary Design Optimization(MDO)of a double-wall turbine blade leading edge.Results indicate an 11.6%increase in cooling efficiency and a 16.21%reduction in maximum stress.Additionally,compared to traditional geometry-based parameterization in MDO,the HFFD approach improves model processing efficiency by 84.15%and overall optimization efficiency by20.05%.These findings demonstrate HFFD's potential to significantly improve complex engineering design optimization by achieving precise shape preservation and improving computational efficiency.
基金supported by the National Natural Science Foundation of China(NSFC)under Grant 62272331the Key Laboratory of Data Protection and Intelligent Management,Ministry of Education,Sichuan University and the Fundamental Research Funds for the Central Universities under Grant SCU2023D008.
文摘Mesh models are among the primary representations for storing 3-D objects,encapsulating detailed geometric information.3-D mesh watermarking,in particular,plays a central role in the protection of 3-D content.However,frequency-domain methods rely on complex parameterization and spectral decomposition,which are sensitive to mesh topology and resolution and often introduce perceptible artifacts.Spatial-domain techniques,on the other hand,typically embed watermarks in global or randomly selected regions,leading to visible distortions and reduced robustness.To address the above limitations and protect model copyright without compromising the original aesthetic quality,we propose a deterministice PCA-synchronized 3Dmeshwatermarkingmethodwith fullerene-guided carrier selection.First,a deterministic principal component analysis(PCA)-based mesh synchronization algorithm is employed to align the models to a canonical pose.Next,a fullerene-inspired carrier selection strategy is employed to determine the watermark carriers,leveraging the structural characteristics of fullerene molecules to achieve a more rational and effective carrier selection.Finally,to balance the embedding strength and enhance visual quality,the watermark information is embedded using an APQIM(Adaptive Parity-Check Quantization Index Modulation)scheme.The experimental results show that our method can achieve high visual quality with scalable capacity and strong robustness compared with existing methods.The watermarking scheme can resist various attacks,including simplification,smoothing,Gaussian noise,translation,and rotation.
文摘This paper studies high order compact finite volume methods on non-uniform meshes for one-dimensional elliptic and parabolic differential equations with the Robin boundary conditions.An explicit scheme and an implicit scheme are obtained by discretizing the equivalent integral form of the equation.For the explicit scheme with nodal values,the algebraic system can be solved by the Thomas method.For the implicit scheme with both nodal values and their derivatives,the system can be implemented by a prediction-correction procedure,where in the correction stage,an implicit formula for recovering the nodal derivatives is introduced.Taking two point boundary value problem as an example,we prove that both the explicit and implicit schemes are convergent with fourth order accuracy with respect to some standard discrete norms using the energy method.Two numerical examples demonstrate the correctness and effectiveness of the schemes,as well as the indispensability of using non-uniform meshes.
基金supported by the National Natural Science Foundation of China(No.62003269).
文摘Computing electrostatic interaction on non-cooperative targets with unknown meshes is crucial for electrostatic-based space on-orbit services.Although meshes for electrostatic interaction computations can be reconstructed from point clouds,they are usually too dense,leading to high computational costs.This paper presents an optimization method for converting dense meshes into optimal meshes,enabling fast and accurate computation of the electrostatic interaction by point clouds.First,the dense mesh reconstructed from point clouds is simplified into a coarse mesh using local operators.Second,the simplified mesh is refined by an iterative strategy that integrates a lightweight method of moments and an impedance matrix inheritance technique,ultimately yielding an optimal mesh for computing the electrostatic interaction.Simulation results show that our method effectively optimizes dense meshes,making electrostatic interaction computations using point clouds approximately 63.4 times more efficient than the previous method.
基金This research was supported by the Sichuan Science and Technology Depart-ment under Contract Nos.2019YJ0396 and 2018JY0516the National Natural Science Foundation of China under the Contract No.51705041.
文摘In the traditional reliability evaluation based on the Bayesian method,the failure probability of nodes is usually expressed by the average failure rate within a period of time.Aiming at the shortcomings of traditional Bayesian network reliability evaluation methods,this paper proposes a Bayesian network reliability evaluation method considering dynamics and fuzziness.The fuzzy theory and the dynamic of component failure probability are introduced to construct the dynamic fuzzy set function.Based on the solving characteristics of the dynamic fuzzy set and Bayesian network,the fuzzy dynamic probability and fuzzy dynamic importance degree of the fault state of leaf nodes are solved.Finally,through the dynamic fuzzy reliability analysis of CNC machine tool hydraulic system balance circuit,the application of this method in system reliability evaluation is verified,which provides support for fault diagnosis of CNC machine tools.
基金supported by the National Natural Science Foundation of China(7127117071101116)+1 种基金the National High Technology Research and Development Program of China(863 Progrom)(2012AA040914)the Basic Research Foundation of Northwestern Polytechnical University(JC20120228)
文摘Importance measures in reliability systems are used to identify weak components in contributing to a proper function of the system.Traditional importance measures mainly concerned the changing value of the system reliability caused by the change of the reliability of the component,and seldom considered the joint effect of the probability distribution,improvement rate of the object component.This paper studies the rate of the system reliability upgrading with an improvement of the component reliability for the multi-state consecutive k-out-of-n system.To verify the multi-state consecutive k-out-of-n system reliability upgrading by improving one component based on its improvement rate,an increasing potential importance(IPI)and its physical meaning are described at first.Secondly,the relationship between the IPI and Birnbaum importance measures are discussed.And the IPI for some different improvement actions of the component is further discussed.Thirdly,the characteristics of the IPI are analyzed.Finally,an application to an oil pipeline system is given.
