Due to space constraints in mountainous areas,twin tunnels are sometimes constructed very close to each other or even overlap.This proximity challenges the structural stability of tunnels built with the drill-and-blas...Due to space constraints in mountainous areas,twin tunnels are sometimes constructed very close to each other or even overlap.This proximity challenges the structural stability of tunnels built with the drill-and-blast method,as the short propagation distance amplifies blasting vibrations.A case of blasting damage is reported in this paper,where concrete cracks crossed construction joints in the twin-arch lining.To identify the causes of these cracks and develop effective vibration mitigation measures,field monitoring and numerical analysis were conducted.Specifically,a restart method was used to simulate the second peak particle velocity(PPV)of MS3 delays occurring 50 ms after the MS1 delays.The study found that the dynamic tensile stress in the tunnel induced by the blast wave has a linear relationship with the of the product of the concrete wave impedance and the PPV.A blast vibration velocity exceeding 23.3 cm/s resulted in tensile stress in the lining surpassing the ultimate tensile strength of C30 concrete,leading to tensile cracking on the blast-facing arch of the constructed tunnel.To control excessive vi-bration velocity,a mitigation trench was implemented to reduce blast wave impact.The trench,approximately 15 m in length,50 cm in width,and 450 cm in height,effectively lowered vibration ve-locities,achieving an average reduction rate of 52%according to numerical analysis.A key innovation of this study is the on-site implementation and validation of the trench's effectiveness in mitigating vi-brations.A feasible trench construction configuration was proposed to overcome the limitations of a single trench in fully controlling vibrations.To further enhance protection,zoned blasting and an auxiliary rock pillar,80 cm in width,were incorporated to reinforce the mid-wall.This study introduces novel strategies for vibration protection in tunnel blasting,offering innovative solutions to address blasting-induced vibrations and effectively minimize their impact,thereby enhancing safety and struc-tural stability.展开更多
Unbalanced force produced by the unbalanced mass will affect vibrations of rotor systems,which probably results in the components failures of rotating machinery.To study the effects of unbalanced mass on the vibration...Unbalanced force produced by the unbalanced mass will affect vibrations of rotor systems,which probably results in the components failures of rotating machinery.To study the effects of unbalanced mass on the vibration characteristics of rotor systems,a flexible rotor system model considering the unbalanced mass is proposed.The time-varying bearing force is considered.The developed model is verified by the experimental and theoretical frequency spectrums.The displacements and axis orbits of flexible and rigid rotor systems are compared.The results show that the unbalanced mass will affect the vibration characteristics of rotor system.This model can be more suitable and effective to calculate vibration characteristics of rotor system with the flexible deformation and unbalanced mass.This paper provides a new reference and research method for predicting the vibrations of flexible rotor system considering the unbalanced mass.展开更多
For the first time,the linear and nonlinear vibrations of composite rectangular sandwich plates with various geometric patterns of lattice core have been analytically examined in this work.The plate comprises a lattic...For the first time,the linear and nonlinear vibrations of composite rectangular sandwich plates with various geometric patterns of lattice core have been analytically examined in this work.The plate comprises a lattice core located in the middle and several homogeneous orthotropic layers that are symmetrical relative to it.For this purpose,the partial differential equations of motion have been derived based on the first-order shear deformation theory,employing Hamilton’s principle and Von Kármán’s nonlinear displacement-strain relations.Then,the nonlinear partial differential equations of the plate are converted into a time-dependent nonlinear ordinary differential equation(Duffing equation)by applying the Galerkin method.From the solution of this equation,the natural frequencies are extracted.Then,to calculate the non-linear frequencies of the plate,the non-linear equation of the plate has been solved analytically using the method of multiple scales.Finally,the effect of some critical parameters of the system,such as the thickness,height,and different angles of the stiffeners on the linear and nonlinear frequencies,has been analyzed in detail.To confirmthe solution method,the results of this research have been compared with the reported results in the literature and finite elements in ABAQUS,and a perfect match is observed.The results reveal that the geometry and configuration of core ribs strongly affect the natural frequencies of the plate.展开更多
Maintaining the integrity and longevity of structures is essential in many industries,such as aerospace,nuclear,and petroleum.To achieve the cost-effectiveness of large-scale systems in petroleum drilling,a strong emp...Maintaining the integrity and longevity of structures is essential in many industries,such as aerospace,nuclear,and petroleum.To achieve the cost-effectiveness of large-scale systems in petroleum drilling,a strong emphasis on structural durability and monitoring is required.This study focuses on the mechanical vibrations that occur in rotary drilling systems,which have a substantial impact on the structural integrity of drilling equipment.The study specifically investigates axial,torsional,and lateral vibrations,which might lead to negative consequences such as bit-bounce,chaotic whirling,and high-frequency stick-slip.These events not only hinder the efficiency of drilling but also lead to exhaustion and harm to the system’s components since they are difficult to be detected and controlled in real time.The study investigates the dynamic interactions of these vibrations,specifically in their high-frequency modes,usingfield data obtained from measurement while drilling.Thefindings have demonstrated the effect of strong coupling between the high-frequency modes of these vibrations on drilling sys-tem performance.The obtained results highlight the importance of considering the interconnected impacts of these vibrations when designing and implementing robust control systems.Therefore,integrating these compo-nents can increase the durability of drill bits and drill strings,as well as improve the ability to monitor and detect damage.Moreover,by exploiting thesefindings,the assessment of structural resilience in rotary drilling systems can be enhanced.Furthermore,the study demonstrates the capacity of structural health monitoring to improve the quality,dependability,and efficiency of rotary drilling systems in the petroleum industry.展开更多
The proposed mass model of vocal fold vibration holds a significant importance in the auxiliary diagnosis and treatment of human vocal fold disorders.Mathematical models are proposed in aerodynamics and acoustics to s...The proposed mass model of vocal fold vibration holds a significant importance in the auxiliary diagnosis and treatment of human vocal fold disorders.Mathematical models are proposed in aerodynamics and acoustics to simulate vocal fold vibration during phonation.This has always been a hot topic in pathological linguistics research.Over the past few decades,researchers have designed various types of mass models of vocal fold vibration based on experiments.These models differ in principles,computational complexity,and degrees of freedom.Therefore,we classify and describe the mass models according to modeling methods.We summarize the research status and characteristics of different models,and based on this,we look forward to future research directions for vocal fold mass models.展开更多
Mega Low Earth Orbit(LEO)satellite constellations can provide pervasive intelligent services in the forthcoming Six-Generation(6G)network via the Free-Space Optical(FSO)InterSatellite Link(ISL).However,the challenges ...Mega Low Earth Orbit(LEO)satellite constellations can provide pervasive intelligent services in the forthcoming Six-Generation(6G)network via the Free-Space Optical(FSO)InterSatellite Link(ISL).However,the challenges posed by the mega LEO satellite constellations,such as limited onboard resources,high-speed movement and the vibration of satellite platforms,present significant obstacles for the existing Pointing,Acquisition and Tracking(PAT)schemes of FSOISL.To address these challenges,we propose a beaconless PAT scheme under satellite platform vibrations,employing a composite scanning approach combining an inner Archimedean spiral scan with an outer regular hexagon step scan.The proposed composite scanning approach covers a wide range of the Field of Uncertainty(FOU)and reduces the required scans by actuator,which can ensure a high Acquisition Probability(AP)while reducing the Average Acquisition Time(AAT)for the inner scan.Specifically,we model and analyze the effect of satellite platform vibrations on the acquisition performance of our beaconless PAT scheme,and derive closed-form expressions for both AP and AAT by utilizing a 2-track model where the acquisition happens on two adjacent spiral scan tracks.By utilizing the theoretical derivations,we can achieve a minimum AAT under diverse APs by selecting appropriate values of overlapping region and scanning range.Simulation results validate that our optimized composite scanning approach for beaconless PAT scheme outperforms the existing schemes.展开更多
The analysis of the dynamics of surface girders is of great importance in the design of engineering structures such as steel welded bridge plane girders or concrete plate-column structures.This work is an extension of...The analysis of the dynamics of surface girders is of great importance in the design of engineering structures such as steel welded bridge plane girders or concrete plate-column structures.This work is an extension of the classical deterministic problem of free vibrations of thin(Kirchhoff)plates.Themain aim of this work is the study of stochastic eigenvibrations of thin(Kirchhoff)elastic plates resting on internal continuous and column supports by the Boundary Element Method(BEM).This work is a continuation of previous research related to the random approach in plate analysis using the BEM.The static fundamental solution(Green’s function)is applied,coupled with a nonsingular formulation of the boundary and domain integral equations.These are derived using a modified and simplified formulation of the boundary conditions,inwhich there is no need to introduce theKirchhoff forces on a plate boundary.The role of the Kirchhoff corner forces is played by the boundary elements placed close to a single corner.Internal column or linear continuous supports are introduced using the Bezine technique,where the additional collocation points are introduced inside a plate domain.This allows for significant simplification of the BEM computational algorithm.An application of the polynomial approximations in the Least Squares Method(LSM)recovery of the structural response is done.The probabilistic analysis will employ three independent computational approaches:semi-analytical method(SAM),stochastic perturbation technique(SPT),and Monte-Carlo simulations.Numerical investigations include the fundamental eigenfrequencies of an elastic,thin,homogeneous,and isotropic plate.展开更多
To advance materials with superior performance,the construction of gradient structures has emerged as a promising strategy.In this study,a gradient nanocrystalline-amorphous structure was induced in Zr46Cu46Al8 bulk m...To advance materials with superior performance,the construction of gradient structures has emerged as a promising strategy.In this study,a gradient nanocrystalline-amorphous structure was induced in Zr46Cu46Al8 bulk metallic glass(BMG)through ultrasonic vibration(UV)treatment.Applying a 20 kHz ultrasonic cyclic loading in the elastic regime,controllable gradient structures with varying crystallized volume fractions can be achieved in less than 2 s by adjusting the input UV energy.In contrast to tradi-tional methods of inducing structural gradients in BMGs,this novel approach offers distinct advantages:it is exceptionally rapid,requires minimal stress,and allows for easy tuning of the extent of structural gradients through precise adjustment of processing parameters.Nanoindentation tests reveal higher hard-ness near the struck surface,attributed to a greater degree of nanocrystal formation,which gradually di-minishes with depth.As a result of the gradient dispersion of nanocrystals,an increased plasticity was found after UV treatment,characterized by the formation of multiple shear bands.Microstructural in-vestigations suggest that UV-induced nanocrystallization originates from local atomic rearrangements in phase-separated Cu-rich regions with high diffusional mobility.Our study underscores the tunability of structural gradients and corresponding performance improvements in BMGs through ultrasonic energy modulation,offering valuable insights for designing advanced metallic materials with tailored mechanical properties.展开更多
Moving-load induced vibrations can,in certain instances,exceed those caused by equivalent static loads,especially at the critical velocity of moving loads.Suppressing these vibrations is of critical practical importan...Moving-load induced vibrations can,in certain instances,exceed those caused by equivalent static loads,especially at the critical velocity of moving loads.Suppressing these vibrations is of critical practical importance in various engineering fields,including the design of precision robotics and advanced aerospace structures where components are subject to moving loads.In this paper,an inertial nonlinear energy sink(NES)is used for the first time to reduce the vibration response of graphene platelet(GPL)-reinforced nanocomposite beams with elastic boundaries under moving loads.Based on the von Kármán nonlinear theory,the governing equations of the beam-NES system are derived using the Lagrange equation.The Newmark-Newton method,in conjunction with the Heaviside step function,is used to obtain the nonlinear responses of the beam under moving loads.The effects of the boundary spring stiffness,the GPL parameters,as well as the velocity and frequency of the moving loads on the beam response and the performance of the NES are thoroughly studied.The results of this work provide insights into applying NESs to suppress the nonlinear vibrations induced by moving loads in composite structures with elastic boundaries.展开更多
In order to control the cross? link forces and the vibration frequencies of the test bed of the full channel gas within the allowable ranges, the analyses of forces and deformation of the test bed was done, for the v...In order to control the cross? link forces and the vibration frequencies of the test bed of the full channel gas within the allowable ranges, the analyses of forces and deformation of the test bed was done, for the variously restrained elastic movable frame and the rigid one, the vibration frequencies were computed respectively by means of the methods of mechanics of materials, elasticity and vibration mechanics, the cross link forces and the vibration frequencies of the test bed were tested. The results of theoretical computation comparatively approach the experimental results. The computational methods could be used to availably estimate the design parameters relevant to the test bed of the full channel gas.展开更多
基金supported by the Shenzhen Stability Support Plan(Grant No.20231122095154003)National Natural Science Foundation of China(Grant Nos.51978671 and 52378425)Guizhou Provincial Department of Transportation Science and Technology Program(Grant No.2023-122-003)。
文摘Due to space constraints in mountainous areas,twin tunnels are sometimes constructed very close to each other or even overlap.This proximity challenges the structural stability of tunnels built with the drill-and-blast method,as the short propagation distance amplifies blasting vibrations.A case of blasting damage is reported in this paper,where concrete cracks crossed construction joints in the twin-arch lining.To identify the causes of these cracks and develop effective vibration mitigation measures,field monitoring and numerical analysis were conducted.Specifically,a restart method was used to simulate the second peak particle velocity(PPV)of MS3 delays occurring 50 ms after the MS1 delays.The study found that the dynamic tensile stress in the tunnel induced by the blast wave has a linear relationship with the of the product of the concrete wave impedance and the PPV.A blast vibration velocity exceeding 23.3 cm/s resulted in tensile stress in the lining surpassing the ultimate tensile strength of C30 concrete,leading to tensile cracking on the blast-facing arch of the constructed tunnel.To control excessive vi-bration velocity,a mitigation trench was implemented to reduce blast wave impact.The trench,approximately 15 m in length,50 cm in width,and 450 cm in height,effectively lowered vibration ve-locities,achieving an average reduction rate of 52%according to numerical analysis.A key innovation of this study is the on-site implementation and validation of the trench's effectiveness in mitigating vi-brations.A feasible trench construction configuration was proposed to overcome the limitations of a single trench in fully controlling vibrations.To further enhance protection,zoned blasting and an auxiliary rock pillar,80 cm in width,were incorporated to reinforce the mid-wall.This study introduces novel strategies for vibration protection in tunnel blasting,offering innovative solutions to address blasting-induced vibrations and effectively minimize their impact,thereby enhancing safety and struc-tural stability.
基金Support by Shanxi Provincial Key Research and Development Plan of China(Grant No.2024GH-ZDXM-29)National Natural Science Foundation of China(Grant No.52175120)Shaanxi Provincial Innovation Capability Support Program of China(Grant No.2024RS-CXTD-15)。
文摘Unbalanced force produced by the unbalanced mass will affect vibrations of rotor systems,which probably results in the components failures of rotating machinery.To study the effects of unbalanced mass on the vibration characteristics of rotor systems,a flexible rotor system model considering the unbalanced mass is proposed.The time-varying bearing force is considered.The developed model is verified by the experimental and theoretical frequency spectrums.The displacements and axis orbits of flexible and rigid rotor systems are compared.The results show that the unbalanced mass will affect the vibration characteristics of rotor system.This model can be more suitable and effective to calculate vibration characteristics of rotor system with the flexible deformation and unbalanced mass.This paper provides a new reference and research method for predicting the vibrations of flexible rotor system considering the unbalanced mass.
文摘For the first time,the linear and nonlinear vibrations of composite rectangular sandwich plates with various geometric patterns of lattice core have been analytically examined in this work.The plate comprises a lattice core located in the middle and several homogeneous orthotropic layers that are symmetrical relative to it.For this purpose,the partial differential equations of motion have been derived based on the first-order shear deformation theory,employing Hamilton’s principle and Von Kármán’s nonlinear displacement-strain relations.Then,the nonlinear partial differential equations of the plate are converted into a time-dependent nonlinear ordinary differential equation(Duffing equation)by applying the Galerkin method.From the solution of this equation,the natural frequencies are extracted.Then,to calculate the non-linear frequencies of the plate,the non-linear equation of the plate has been solved analytically using the method of multiple scales.Finally,the effect of some critical parameters of the system,such as the thickness,height,and different angles of the stiffeners on the linear and nonlinear frequencies,has been analyzed in detail.To confirmthe solution method,the results of this research have been compared with the reported results in the literature and finite elements in ABAQUS,and a perfect match is observed.The results reveal that the geometry and configuration of core ribs strongly affect the natural frequencies of the plate.
文摘Maintaining the integrity and longevity of structures is essential in many industries,such as aerospace,nuclear,and petroleum.To achieve the cost-effectiveness of large-scale systems in petroleum drilling,a strong emphasis on structural durability and monitoring is required.This study focuses on the mechanical vibrations that occur in rotary drilling systems,which have a substantial impact on the structural integrity of drilling equipment.The study specifically investigates axial,torsional,and lateral vibrations,which might lead to negative consequences such as bit-bounce,chaotic whirling,and high-frequency stick-slip.These events not only hinder the efficiency of drilling but also lead to exhaustion and harm to the system’s components since they are difficult to be detected and controlled in real time.The study investigates the dynamic interactions of these vibrations,specifically in their high-frequency modes,usingfield data obtained from measurement while drilling.Thefindings have demonstrated the effect of strong coupling between the high-frequency modes of these vibrations on drilling sys-tem performance.The obtained results highlight the importance of considering the interconnected impacts of these vibrations when designing and implementing robust control systems.Therefore,integrating these compo-nents can increase the durability of drill bits and drill strings,as well as improve the ability to monitor and detect damage.Moreover,by exploiting thesefindings,the assessment of structural resilience in rotary drilling systems can be enhanced.Furthermore,the study demonstrates the capacity of structural health monitoring to improve the quality,dependability,and efficiency of rotary drilling systems in the petroleum industry.
基金the Shanghai Educational Sciences Research Program(No.C2021016)。
文摘The proposed mass model of vocal fold vibration holds a significant importance in the auxiliary diagnosis and treatment of human vocal fold disorders.Mathematical models are proposed in aerodynamics and acoustics to simulate vocal fold vibration during phonation.This has always been a hot topic in pathological linguistics research.Over the past few decades,researchers have designed various types of mass models of vocal fold vibration based on experiments.These models differ in principles,computational complexity,and degrees of freedom.Therefore,we classify and describe the mass models according to modeling methods.We summarize the research status and characteristics of different models,and based on this,we look forward to future research directions for vocal fold mass models.
基金supported in part by the Major Key Project of PCL of China(No.PCL2024A01)in part by the National Natural Science Foundation of China(Nos.62071141,62027802)+1 种基金in part by the Shenzhen Science and Technology Program of China(Nos.JCYJ20241202123904007,GXWD20231127123203001,JSGG20220831110801003)in part by the Fundamental Research Funds for the Central Universities of China(No.HIT.OCEF.2024046)。
文摘Mega Low Earth Orbit(LEO)satellite constellations can provide pervasive intelligent services in the forthcoming Six-Generation(6G)network via the Free-Space Optical(FSO)InterSatellite Link(ISL).However,the challenges posed by the mega LEO satellite constellations,such as limited onboard resources,high-speed movement and the vibration of satellite platforms,present significant obstacles for the existing Pointing,Acquisition and Tracking(PAT)schemes of FSOISL.To address these challenges,we propose a beaconless PAT scheme under satellite platform vibrations,employing a composite scanning approach combining an inner Archimedean spiral scan with an outer regular hexagon step scan.The proposed composite scanning approach covers a wide range of the Field of Uncertainty(FOU)and reduces the required scans by actuator,which can ensure a high Acquisition Probability(AP)while reducing the Average Acquisition Time(AAT)for the inner scan.Specifically,we model and analyze the effect of satellite platform vibrations on the acquisition performance of our beaconless PAT scheme,and derive closed-form expressions for both AP and AAT by utilizing a 2-track model where the acquisition happens on two adjacent spiral scan tracks.By utilizing the theoretical derivations,we can achieve a minimum AAT under diverse APs by selecting appropriate values of overlapping region and scanning range.Simulation results validate that our optimized composite scanning approach for beaconless PAT scheme outperforms the existing schemes.
基金funded by research grant OPUS no.2021/41/B/ST8/02432 entitled Probabilistic entropy in engineering computations sponsored by The National Science Center in Polandthe Institute of Structural Analysis of Poznan University of Technology in the framework of the internal research grant 0411/SBAD/0010.
文摘The analysis of the dynamics of surface girders is of great importance in the design of engineering structures such as steel welded bridge plane girders or concrete plate-column structures.This work is an extension of the classical deterministic problem of free vibrations of thin(Kirchhoff)plates.Themain aim of this work is the study of stochastic eigenvibrations of thin(Kirchhoff)elastic plates resting on internal continuous and column supports by the Boundary Element Method(BEM).This work is a continuation of previous research related to the random approach in plate analysis using the BEM.The static fundamental solution(Green’s function)is applied,coupled with a nonsingular formulation of the boundary and domain integral equations.These are derived using a modified and simplified formulation of the boundary conditions,inwhich there is no need to introduce theKirchhoff forces on a plate boundary.The role of the Kirchhoff corner forces is played by the boundary elements placed close to a single corner.Internal column or linear continuous supports are introduced using the Bezine technique,where the additional collocation points are introduced inside a plate domain.This allows for significant simplification of the BEM computational algorithm.An application of the polynomial approximations in the Least Squares Method(LSM)recovery of the structural response is done.The probabilistic analysis will employ three independent computational approaches:semi-analytical method(SAM),stochastic perturbation technique(SPT),and Monte-Carlo simulations.Numerical investigations include the fundamental eigenfrequencies of an elastic,thin,homogeneous,and isotropic plate.
基金supported by the Key Basic and Applied Research Program of Guangdong Province,China(Grant No.2019B030302010)the NSF of China(Grant Nos.52122105,52271150,52201185,52201186,52371160)+1 种基金the Science and Technology Innovation Commission Shenzhen(Grants Nos.RCJC20221008092730037,20220804091920001)the Research Team Cultivation Program of Shenzhen University,Grant No.2023QNT001.
文摘To advance materials with superior performance,the construction of gradient structures has emerged as a promising strategy.In this study,a gradient nanocrystalline-amorphous structure was induced in Zr46Cu46Al8 bulk metallic glass(BMG)through ultrasonic vibration(UV)treatment.Applying a 20 kHz ultrasonic cyclic loading in the elastic regime,controllable gradient structures with varying crystallized volume fractions can be achieved in less than 2 s by adjusting the input UV energy.In contrast to tradi-tional methods of inducing structural gradients in BMGs,this novel approach offers distinct advantages:it is exceptionally rapid,requires minimal stress,and allows for easy tuning of the extent of structural gradients through precise adjustment of processing parameters.Nanoindentation tests reveal higher hard-ness near the struck surface,attributed to a greater degree of nanocrystal formation,which gradually di-minishes with depth.As a result of the gradient dispersion of nanocrystals,an increased plasticity was found after UV treatment,characterized by the formation of multiple shear bands.Microstructural in-vestigations suggest that UV-induced nanocrystallization originates from local atomic rearrangements in phase-separated Cu-rich regions with high diffusional mobility.Our study underscores the tunability of structural gradients and corresponding performance improvements in BMGs through ultrasonic energy modulation,offering valuable insights for designing advanced metallic materials with tailored mechanical properties.
基金Project supported by the National Natural Science Foundation of China(No.12472003)the Key Research Project of Zhejiang Market Supervision Administration(No.ZD2024013)the Technical Project of Research Institute of Highway Ministry of Transport of China(No.0225KF12SC1002)。
文摘Moving-load induced vibrations can,in certain instances,exceed those caused by equivalent static loads,especially at the critical velocity of moving loads.Suppressing these vibrations is of critical practical importance in various engineering fields,including the design of precision robotics and advanced aerospace structures where components are subject to moving loads.In this paper,an inertial nonlinear energy sink(NES)is used for the first time to reduce the vibration response of graphene platelet(GPL)-reinforced nanocomposite beams with elastic boundaries under moving loads.Based on the von Kármán nonlinear theory,the governing equations of the beam-NES system are derived using the Lagrange equation.The Newmark-Newton method,in conjunction with the Heaviside step function,is used to obtain the nonlinear responses of the beam under moving loads.The effects of the boundary spring stiffness,the GPL parameters,as well as the velocity and frequency of the moving loads on the beam response and the performance of the NES are thoroughly studied.The results of this work provide insights into applying NESs to suppress the nonlinear vibrations induced by moving loads in composite structures with elastic boundaries.
文摘In order to control the cross? link forces and the vibration frequencies of the test bed of the full channel gas within the allowable ranges, the analyses of forces and deformation of the test bed was done, for the variously restrained elastic movable frame and the rigid one, the vibration frequencies were computed respectively by means of the methods of mechanics of materials, elasticity and vibration mechanics, the cross link forces and the vibration frequencies of the test bed were tested. The results of theoretical computation comparatively approach the experimental results. The computational methods could be used to availably estimate the design parameters relevant to the test bed of the full channel gas.
