In the practical environment,it is very common for the simultaneous occurrence of base excitation and crosswind.Scavenging the combined energy of vibration and wind with a single energy harvesting structure is fascina...In the practical environment,it is very common for the simultaneous occurrence of base excitation and crosswind.Scavenging the combined energy of vibration and wind with a single energy harvesting structure is fascinating.For this purpose,the effects of the wind speed and random excitation level are investigated with the stochastic averaging method(SAM)based on the energy envelope.The results of the analytical prediction are verified with the Monte-Carlo method(MCM).The numerical simulation shows that the introduction of wind can reduce the critical excitation level for triggering an inter-well jump and make a bi-stable energy harvester(BEH)realize the performance enhancement for a weak base excitation.However,as the strength of the wind increases to a particular level,the influence of the random base excitation on the dynamic responses is weakened,and the system exhibits a periodic galloping response.A comparison between a BEH and a linear energy harvester(LEH)indicates that the BEH demonstrates inferior performance for high-speed wind.Relevant experiments are conducted to investigate the validity of the theoretical prediction and numerical simulation.The experimental findings also show that strong random excitation is favorable for the BEH in the range of low wind speeds.However,as the speed of the incoming wind is up to a particular level,the disadvantage of the BEH becomes clear and evident.展开更多
Real-time onboard health monitoring systems are critical for the railway industry to maintain high service quality and operational safety.However,the issue with power supplies for monitoring sensors persists,especiall...Real-time onboard health monitoring systems are critical for the railway industry to maintain high service quality and operational safety.However,the issue with power supplies for monitoring sensors persists,especially for freight trains that lack onboard power.Here,we propose a hybrid piezoelectric-triboelectric rotary generator(HPT-RG)for energy harvesting and vehicle speed sensing.The HPT-RG incorporates a rotational self-adaptive technique that softens the equivalent stiffness,enabling the piezoelectric non-resonant beam to surpass resonance limitations in a low-frequency region.The experiments demonstrate the feasibility of using the HPT-RG as an energy harvesting module to collect the rotational energy of the freight rail transport and power the wireless temperature sensors.To allow multiple monitoring in confined spaces on trains,a triboelectric sensing module is added to the HPT-RG to sense the operation speed and mileage of vehicles.Furthermore,the generator exhibits favorable mechanical durability under more than 600 h of official testing on the train bogie axle.The proposed HPT-RG is essential for creating a truly self-powered,maintenance-free,and zero-carbon onboard wireless monitoring system on freight railways.展开更多
Auxetic honeycomb structures are promising metamaterials with outstanding mechanical properties,and can be potentially used in energy absorption applications.In this study,a novel modified re-entrant hybrid auxetic me...Auxetic honeycomb structures are promising metamaterials with outstanding mechanical properties,and can be potentially used in energy absorption applications.In this study,a novel modified re-entrant hybrid auxetic metamaterial inspired by Islamic motif art is designed by integrating four-pointed double re-entrant motifs with symmetric semi-hexagonal unit cells to achieve a high energy absorption capacity(EAC).Theoretical analyses and numerical simulations are performed to examine the dynamic crushing behavior of the four-pointed double re-entrant combined structure(FDRCS).The developed finite element models(FEMs)are validated by the experiments under quasi-static compression.The deformation mode and stress-strain curves are further studied under low,medium,and high crushing velocities.The theoretically predicted plateau stress of the FDRCS under different crushing velocities is consistent with the numerical simulation results.The crushing stress and the EAC of the FDRCS are influenced by the geometric parameters and crushing velocities.The FDRCS exhibits a negative Poisson's ratio(NPR),owing to the four-point re-entrant structure(RES).Moreover,the specific energy absorption(SEA)of these structures is higher than that of nonauxetic hexagonal and auxetic re-entrant structures,owing to the generation of more plastic hinges that dissipate more energy during dynamic crushing.展开更多
In real systems,the unpredictable jump changes of the random environment can induce the critical transitions(CTs)between two non-adjacent states,which are more catastrophic.Taking an asymmetric Lévy-noise-induced...In real systems,the unpredictable jump changes of the random environment can induce the critical transitions(CTs)between two non-adjacent states,which are more catastrophic.Taking an asymmetric Lévy-noise-induced tri-stable model with desirable,sub-desirable,and undesirable states as a prototype class of real systems,a prediction of the noise-induced CTs from the desirable state directly to the undesirable one is carried out.We first calculate the region that the current state of the given model is absorbed into the undesirable state based on the escape probability,which is named as the absorbed region.Then,a new concept of the parameter dependent basin of the unsafe regime(PDBUR)under the asymmetric Lévy noise is introduced.It is an efficient tool for approximately quantifying the ranges of the parameters,where the noise-induced CTs from the desirable state directly to the undesirable one may occur.More importantly,it may provide theoretical guidance for us to adopt some measures to avert a noise-induced catastrophic CT.展开更多
The periodic-phase-diagram similarity method is proposed to identify the frequency of weak harmonic signals.The key technology is to find a set of optimal coefficients for Duffing system,which leads to the periodic mo...The periodic-phase-diagram similarity method is proposed to identify the frequency of weak harmonic signals.The key technology is to find a set of optimal coefficients for Duffing system,which leads to the periodic motion under the influence of weak signal and strong noise.Introducing the phase diagram similarity,the influences of strong noise on the similarity of periodic phase diagram are discussed.The principle of highest similarity of periodic phase diagram with the same frequency is detected by discussing the persistence of similarity of periodic motion phase diagram under the strong noise and the periodic-phase-diagram similarity method is constructed.The weak signals of early fault and strong noise are input into Duffing system to obtain the identified system.The stochastic subharmonic Melnikov method is extended to obtain the conditions of the optimal coefficients for the identified system.Based on the results,the constructed frequency conversion harmonic weak signals are considered to form a datum periodic system.With the change of frequency in the datum periodic system,the phase diagram similarity of the two constructed systems can be calculated.Based on the periodic-phase-diagram similarity method,the frequency of weak harmonic signals can be identified by the principle of highest similarity of periodic phase diagram with the same frequency.The results of numerical simulation and the early fault diagnosis results of actual bearings verify the feasibility of the periodic-phase-diagram similarity method.The accuracy of the detection effect is 97%,and the minimum signal-to-noise ratio is−80.71 dB.展开更多
基金Project supported by the National Natural Science Foundation of China(Nos.12272355,1202520411902294)+1 种基金the Opening Foundation of Shanxi Provincial Key Laboratory for Advanced Manufacturing Technology of China(No.XJZZ202304)the Shanxi Provincial Graduate Innovation Project of China(No.2023KY629)。
文摘In the practical environment,it is very common for the simultaneous occurrence of base excitation and crosswind.Scavenging the combined energy of vibration and wind with a single energy harvesting structure is fascinating.For this purpose,the effects of the wind speed and random excitation level are investigated with the stochastic averaging method(SAM)based on the energy envelope.The results of the analytical prediction are verified with the Monte-Carlo method(MCM).The numerical simulation shows that the introduction of wind can reduce the critical excitation level for triggering an inter-well jump and make a bi-stable energy harvester(BEH)realize the performance enhancement for a weak base excitation.However,as the strength of the wind increases to a particular level,the influence of the random base excitation on the dynamic responses is weakened,and the system exhibits a periodic galloping response.A comparison between a BEH and a linear energy harvester(LEH)indicates that the BEH demonstrates inferior performance for high-speed wind.Relevant experiments are conducted to investigate the validity of the theoretical prediction and numerical simulation.The experimental findings also show that strong random excitation is favorable for the BEH in the range of low wind speeds.However,as the speed of the incoming wind is up to a particular level,the disadvantage of the BEH becomes clear and evident.
基金supported by the National Natural Science Foundation of China(Grant Nos.12302022,12172248,12021002,and 12132010)Tianjin Research Program of Application Foundation and Advanced Technology(Grant No.22JCQNJC00780)+1 种基金the State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures(Grant No.KF2024-09)the IoT Standards and Application Key Laboratory of the Ministry of Industry and Information Technology(Grant No.202306).
文摘Real-time onboard health monitoring systems are critical for the railway industry to maintain high service quality and operational safety.However,the issue with power supplies for monitoring sensors persists,especially for freight trains that lack onboard power.Here,we propose a hybrid piezoelectric-triboelectric rotary generator(HPT-RG)for energy harvesting and vehicle speed sensing.The HPT-RG incorporates a rotational self-adaptive technique that softens the equivalent stiffness,enabling the piezoelectric non-resonant beam to surpass resonance limitations in a low-frequency region.The experiments demonstrate the feasibility of using the HPT-RG as an energy harvesting module to collect the rotational energy of the freight rail transport and power the wireless temperature sensors.To allow multiple monitoring in confined spaces on trains,a triboelectric sensing module is added to the HPT-RG to sense the operation speed and mileage of vehicles.Furthermore,the generator exhibits favorable mechanical durability under more than 600 h of official testing on the train bogie axle.The proposed HPT-RG is essential for creating a truly self-powered,maintenance-free,and zero-carbon onboard wireless monitoring system on freight railways.
基金the National Natural Science Foundation of China(Nos.12102274,1207220311872253)+1 种基金the Natural Science Foundation of Hebei Province of China(No.A2022210005)the Central Guidance on Local Science and Technology Development Fund of Hebei Province of China(No.226Z4901G)。
文摘Auxetic honeycomb structures are promising metamaterials with outstanding mechanical properties,and can be potentially used in energy absorption applications.In this study,a novel modified re-entrant hybrid auxetic metamaterial inspired by Islamic motif art is designed by integrating four-pointed double re-entrant motifs with symmetric semi-hexagonal unit cells to achieve a high energy absorption capacity(EAC).Theoretical analyses and numerical simulations are performed to examine the dynamic crushing behavior of the four-pointed double re-entrant combined structure(FDRCS).The developed finite element models(FEMs)are validated by the experiments under quasi-static compression.The deformation mode and stress-strain curves are further studied under low,medium,and high crushing velocities.The theoretically predicted plateau stress of the FDRCS under different crushing velocities is consistent with the numerical simulation results.The crushing stress and the EAC of the FDRCS are influenced by the geometric parameters and crushing velocities.The FDRCS exhibits a negative Poisson's ratio(NPR),owing to the four-point re-entrant structure(RES).Moreover,the specific energy absorption(SEA)of these structures is higher than that of nonauxetic hexagonal and auxetic re-entrant structures,owing to the generation of more plastic hinges that dissipate more energy during dynamic crushing.
基金Project supported by the National Natural Science Foundation of China(No.12072264)the Fundamental Research Funds for the Central Universities+3 种基金the Research Funds for Interdisciplinary Subject of Northwestern Polytechnical Universitythe Shaanxi Project for Distinguished Young Scholarsthe National Key Research and Development Program of China(No.2018AAA0102201)the Shaanxi Provincial Key R&D Program(Nos.2020KW-013 and 2019TD-010)。
文摘In real systems,the unpredictable jump changes of the random environment can induce the critical transitions(CTs)between two non-adjacent states,which are more catastrophic.Taking an asymmetric Lévy-noise-induced tri-stable model with desirable,sub-desirable,and undesirable states as a prototype class of real systems,a prediction of the noise-induced CTs from the desirable state directly to the undesirable one is carried out.We first calculate the region that the current state of the given model is absorbed into the undesirable state based on the escape probability,which is named as the absorbed region.Then,a new concept of the parameter dependent basin of the unsafe regime(PDBUR)under the asymmetric Lévy noise is introduced.It is an efficient tool for approximately quantifying the ranges of the parameters,where the noise-induced CTs from the desirable state directly to the undesirable one may occur.More importantly,it may provide theoretical guidance for us to adopt some measures to avert a noise-induced catastrophic CT.
基金This study was supported by the National Natural Science Foundation of China(Nos.12072203,11872253,12032017)the Hundred Excellent Innovative Talents in Hebei Province(No.SLRC2019037)+3 种基金the“333 talent project”in Hebei Province(No.A202005007)the Natural Science Foundation in Hebei Province of China(Nos.A2019421005,A2019402043,E2019210278)the Hebei Provincial Department of Education Project(Nos.ZD2020328,QN2019149,QN2018237)the Graduate Student Innovation Ability Training Project of Hebei Education Department(CXZZSS2021080).
文摘The periodic-phase-diagram similarity method is proposed to identify the frequency of weak harmonic signals.The key technology is to find a set of optimal coefficients for Duffing system,which leads to the periodic motion under the influence of weak signal and strong noise.Introducing the phase diagram similarity,the influences of strong noise on the similarity of periodic phase diagram are discussed.The principle of highest similarity of periodic phase diagram with the same frequency is detected by discussing the persistence of similarity of periodic motion phase diagram under the strong noise and the periodic-phase-diagram similarity method is constructed.The weak signals of early fault and strong noise are input into Duffing system to obtain the identified system.The stochastic subharmonic Melnikov method is extended to obtain the conditions of the optimal coefficients for the identified system.Based on the results,the constructed frequency conversion harmonic weak signals are considered to form a datum periodic system.With the change of frequency in the datum periodic system,the phase diagram similarity of the two constructed systems can be calculated.Based on the periodic-phase-diagram similarity method,the frequency of weak harmonic signals can be identified by the principle of highest similarity of periodic phase diagram with the same frequency.The results of numerical simulation and the early fault diagnosis results of actual bearings verify the feasibility of the periodic-phase-diagram similarity method.The accuracy of the detection effect is 97%,and the minimum signal-to-noise ratio is−80.71 dB.
