Adhesive interaction is a ubiquitous phenomenon in various aspects of nature and engineering,driving extensive research on adhesive contact over past decades.This brief review surveys adhesive contact models at the si...Adhesive interaction is a ubiquitous phenomenon in various aspects of nature and engineering,driving extensive research on adhesive contact over past decades.This brief review surveys adhesive contact models at the single-asperity level.Attention has been focused on how adhesive interaction is accounted for in models of normal contact,inclined contact,and contact with rolling tendency,and hence the corresponding interfacial tractions have been outlined.Perspectives on remaining challenges in adhesive contact mechanics have also been summarized.展开更多
This paper investigates the contact problem of an air-inflated circular membrane with a finite rigid indentor having three different geometric profiles,namely flat-face,conical,and spherical.Initially,the axisymmetric...This paper investigates the contact problem of an air-inflated circular membrane with a finite rigid indentor having three different geometric profiles,namely flat-face,conical,and spherical.Initially,the axisymmetric inflation problem of a thin circular mem-brane is studied under uniform pressurization.The material is assumed to be homogeneous,isotropic,and incompressible,which is described by the two-parameter Mooney-Rivlin hyperelastic model.An indentor with finite radius is pressed quasi-statically against the inflated membrane,preserving the axisymmetric nature of deformation.The contact problem is formulated for both frictionless and no-slip contact conditions.A set of coupled nonlinear second order partial differential equations for both contact and non-contact regions are solved using a shooting method coupled with an optimization algorithm.The inflated membrane profiles in contact with different indentor geometries,principal stretch ratios,and Cauchy stress resultants are obtained.The possibility of having multiple contact zones and their interaction on different faces of the indentor is also explored.The force-displacement(stiffness)curves for this finite indentor contact problem show the existence of a critical contact force,which limits the force bearing capacity of the inflated structure.This critical force is found to be higher for larger strain-hardening of the material and higher indentor radius.The junction of contact and non-contact regions for flat-faced and conical indentors is found to be the critical section due to slope discontinuity.However,for the spherical indentor,the pole of the membrane is most prone to rupture due to membrane thinning effect.展开更多
This study develops a contact performance-driven method for skiving face gear drives using a single cutter,eliminating the traditional need for separate cutters to reduce production costs and time.First,the mathematic...This study develops a contact performance-driven method for skiving face gear drives using a single cutter,eliminating the traditional need for separate cutters to reduce production costs and time.First,the mathematical models of the tooth flanks for the face gear drives are established based on the gear skiving processes.Then,load tooth contact analysis(LTCA)model is established to calculate the contact performance data.Next,a two-stage optimization model is employed to determine the optimal parameters of the cutting edge with improved contact performances.The effectiveness of this method is validated through simulations and rolling tests.Compared with the traditional method,the proposed method can machine both the face gear and its mating pinion with a single cutter.Simulation results show that the proposed method avoids tooth surface edge contact,with the maximum tooth surface contact stress reduced by 31.7%,the contact ratio decreases by 21.5%,and the transmission error increases by 22.3%.Rolling tests verify the consistency of tooth surface contact patterns between simulations and experiments.The proposed method provides a reference for the cutting edge design of skiving cutters for face gear pairs.展开更多
Al-rich AlxGa1-xN(x≥0.8)is promising for power and deep-ultraviolet(DUV)optoelectronic applications,owing to its ultra-wide bandgap and excellent thermal stability.However,forming low-resistivity contacts on n-...Al-rich AlxGa1-xN(x≥0.8)is promising for power and deep-ultraviolet(DUV)optoelectronic applications,owing to its ultra-wide bandgap and excellent thermal stability.However,forming low-resistivity contacts on n-type Al-rich AlGaN remains a significant challenge.In this work,we utilized an Au-free Ti/Al/Ti metal stack contact on n-type Al-rich AlGaN without graded layers.Record-low contact resistivities were achieved after annealing:1.52×10-6Ω·cm2for n-Al0.8Ga0.2N,3.56×10-6Ω·cm2for n-Al0.86Ga0.14N,and 5.79×10-5Ω·cm2for n-Al0.9Ga0.1N.These results demonstrate a significant advancement in forming low-resistance contacts directly on Al-rich n-AlGaN,offering a viable path forward for next-generation power electronics and DUV optoelectronic devices.展开更多
Revolute joints are widely used in various engineering fields such as deployable space structures and robotics.Currently,various theoretical models have been applied to evaluate the normal contact force of the revolut...Revolute joints are widely used in various engineering fields such as deployable space structures and robotics.Currently,various theoretical models have been applied to evaluate the normal contact force of the revolute joints;however,the results obtained by these models often exhibit significant discrepancies,and there is a lack of explanation for the reasons behind these discrepancies.This study explores the underlying theories of three classical non-conformal contact force models for revolute joints,namely the ESDU-78035 model,the Radzimovsky model,and the Dubowsky-Freudenstein model.The theoretical differences among these classical models are analyzed,and their deficiencies are discovered,and then an improved non-conformal normal contact force model is presented.To validate the accuracy of the presented model,three-dimensional refined finite element models employing surface-to-surface contact elements are constructed to simulate the normal contact of the revolute joint with different clearance sizes and different contact lengths.A comprehensive comparison is carried out between the semi-contact-width,contact pressure,and load-deformation curves obtained from the theoretical models and the finite element model.The results indicate that the presented contact force model outperforms the three classical contact force models in terms of accuracy.The differences between the ideal contact model and the real revolute joint are also investigated,and a sub-model modeling method is presented for the real revolute joint based on the ideal contact force model.展开更多
Fluid flow through a single fracture is commonly described by the cubic law.However,deviations from this model are expected because natural fracture surfaces are rough and in contact with each other in discrete region...Fluid flow through a single fracture is commonly described by the cubic law.However,deviations from this model are expected because natural fracture surfaces are rough and in contact with each other in discrete regions.In this study,the interactions between fracture closure,contact area,and hydraulic characterization of mesoscopic-scale rough fractures were investigated.First,natural-splitting fractures induced by Brazilian splitting were generated and digitally reproduced using a three-dimensional scanner.The distribution characterization of the initial mechanical fracture apertures was described,and the variation in fracture contact area during fracture closure was evaluated.Second,numerical simulations of fluid flow between rough surfaces were conducted,and the Stokes equations were solved.The results reveal that the hydraulic aperture underwent three stages.When the contact area was less than 0.34%,changes in the hydraulic aperture resulted in flow rate changes that were consistent with the cubic law.When the contact area was between 0.34%and 14.41%,the hydraulic aperture gradually deviated from the cubic law and fell below the mean fracture aperture.At this stage,the hydraulic aperture should be fully considered rather than the mean fracture aperture.When the contact area exceeds 14.41%,although the mechanical fracture decreases with increasing strain,the influence of the contact area on the hydraulic aperture gradually diminishes.This is because the fractures contain less fluid,and the hydraulic aperture approaches the minimum.Finally,the relationship between mechanical and hydraulic aperture strains was established,improving geological engineering applications that account for fracture deformation.展开更多
In rock engineering,natural cracks in rock masses subjected to external loads tend to initiate and propagate,leading to potential safety hazards.To investigate the effect of cracking behavior on the mechanical propert...In rock engineering,natural cracks in rock masses subjected to external loads tend to initiate and propagate,leading to potential safety hazards.To investigate the effect of cracking behavior on the mechanical properties of rocks,the cracking processes of pre-cracked rocks have been extensively studied using numerical modeling methods.The peridynamics(PD)exhibits advantages over other numerical methods due to the absence of the requirements for remeshing and external crack growth criterion.However,for modeling pre-cracked rock cracking processes under impact,current PD implementations lack generally applicable rock constitutive models and impact contact models,which leads to difficulties in determining rock material parameters and efficiently calculating impact loads.This paper proposes a non-ordinary state-based peridynamics(NOSBPD)modeling method integrating the Drucker-Prager(DP)plasticity model and an efficient contact model to address the above problems.In the proposed method,the Drucker-Prager plasticity model is integrated into the NOSBPD,thereby equipping NOSBPD with the capability to accurately characterize the nonlinear stress-strain relationship inherent in rocks.An efficient contact model between particles and meshes is designed to calculate the impact loads,which is essentially a coupling method of PD with the finite element method(FEM).The effectiveness of the proposed NOSBPD modeling method is verified by comparison with other numerical methods and experiments.Experimental results indicate that the proposed method can effectively and accurately predict the 3D cracking processes of pre-cracked cracks under impact loading,and the maximum principal stress is the key driver behind wing crack formation in pre-cracked rocks.展开更多
The accuracy of wheel-rail rolling contact force is of great significance for vehicle dynamics simulation.A wheel-rail rolling contact behavior model considering wheelset yaw is proposed.The NORM algorithm is adopted ...The accuracy of wheel-rail rolling contact force is of great significance for vehicle dynamics simulation.A wheel-rail rolling contact behavior model considering wheelset yaw is proposed.The NORM algorithm is adopted to solve the wheel-rail normal contact problem.The extended creep force model(ECF)is used for the tangential contact problem,which considers different interfacial conditions,temperature in the contact area,and the elastoplastic behavior of the third body.A fatigue life prediction framework based on the critical plane method is introduced to evaluate the contact fatigue damage under the coupled influence of yaw angle and interfacial conditions.The effects of wheel yaw angle on the contact pressure and wheel-rail rolling contact fatigue life under dry and wet conditions are investigated.The results show that under both dry and wet conditions,increasing yaw angle leads to an increase in creepage,expansion of the sliding area,enhancement of creep force,and a simultaneous increase in the contact area temperature,thereby causing an increase in the fatigue parameter(FP).The wheel-rail rolling contact life with yaw angle is shortened compared to that without yaw,and the life decay rate under wet condition is slower than that under dry condition.展开更多
This paper investigates the “brush-like”deformation phenomenon of the contact interface at the bolt-hole during the interference-fit installation of high-locking bolts under static loading in CFRP connection structu...This paper investigates the “brush-like”deformation phenomenon of the contact interface at the bolt-hole during the interference-fit installation of high-locking bolts under static loading in CFRP connection structures.An innovative theoretical model is proposed to predict axial installation force,specifically designed for moderate interference-fit.This model is based on the “brush-like”deformation of the hole wall,with the axial installation force predicted through force analysis and theoretical calculations,effectively overcoming the limitations of prior models that idealized the contact interface at the bolt-hole.The predictions generated by this theoretical model align closely with experimental data,confirming its efficacy in accurately forecasting the curve of installation force for interferencefit bolts during the static installation within the moderate interference-fit range.Additionally,a comprehensive analysis of the relationship between deformation of the hole wall and curves of installation force across small,moderate,and large interference-fit levels are presented.It is demonstrated that the degree of deformation within the moderate interference-fit range is more suitable than that in the small and large interference-fit ranges,making it a reliable alternative for installation force tests within this range during static installation.The moderate interference-fit domain[1.00%,1.24%]is established as a validated and optimal range of interference-fit bolts for the static installation.展开更多
Achieving high emission efficiency at low current densities remains a challenge for micro-LEDs.Here,we demonstrate a controllable interfacial strategy by tuning the annealing temperature of RF-superimposed DC sputtere...Achieving high emission efficiency at low current densities remains a challenge for micro-LEDs.Here,we demonstrate a controllable interfacial strategy by tuning the annealing temperature of RF-superimposed DC sputtered ITO to modulate carrier injection dynamics.STEM analysis reveals 500℃ annealing triggers discrete substitutional In-atom incorporation into the p-GaN lattice,forming localized nanoscale contact regions.This architecture induces a localized carrier injection mechanism that significantly enhances the efficiency of micro-LEDs at low current densities.Specifically,the 500℃-annealed 10μm devices exhibit a dramatic enhancement in light output power(LOP),reaching 1.3×10-1 mW at 5 A/cm2,which is significantly higher than the 5.3×10-4 mW measured for 700°C-annealed devices.Furthermore,the peak efficiency current density(Jpeak)is dramatically shifted from 140 to 17 A/cm2 for 5μm devices.Capacitance-voltage analysis further corroborates the localized carrier injection mechanism.These findings establish contact interfacial modulation as a robust strategy for optimizing micro-LEDs in low-power display applications and tailoring device-level performance across broader optoelectronics.展开更多
Metro line has the characteristics of short station distance,low operating speed,frequent traction/braking,high acceleration and deceleration,small curve radius and various track types.The wheel-rail low adhesion beha...Metro line has the characteristics of short station distance,low operating speed,frequent traction/braking,high acceleration and deceleration,small curve radius and various track types.The wheel-rail low adhesion behavior,wear and damage problems are prominent under such a complicated operation condition.This article compares and analyzes the wheel-rail adhesion characteristic on four kinds of tracks,including the concrete slab bed track,steel-spring floating slab track,elastic support block track and trapezoidal sleeper track,revealing the adhesion degradation mechanism of metro wheel-rail system under different operating conditions,such as traction and braking.The results indicate that there are differences in the creepage response and the lowest limit of the wheel-rail adhesion coefficient on different track structures,while the maximum adhesion coefficient of the four track structures under traction/braking conditions shows a similar trend with the variation in speed and adhesion conditions.Traction and braking loads,as well as wheel-rail adhesion conditions,exert a relatively minor influence on the normal contact stress distribution of the wheel-rail interface,but significantly affect shear stress distributions.This study is shown to enhance the understanding of the combined effects of adhesion degradation and track types on the wheel-rail contact stress and surface damage.展开更多
The transformative potential of gallium nitride high electron mobility transistors(GaN HEMTs)in advancing carbon-neutral power systems remains bottlenecked by contact resistance(Rc)at the metal-semiconductor(M-S)inter...The transformative potential of gallium nitride high electron mobility transistors(GaN HEMTs)in advancing carbon-neutral power systems remains bottlenecked by contact resistance(Rc)at the metal-semiconductor(M-S)interface,a critical determinant of switching losses and frequency response.Herein,by engineering a TiAl/TiAlTa/Au metastructure,we propose a novel interface-driven strategy employing Ta-mediated interfacial reconstruction to achieve a record-low Rc of 0.07Ωmm,which is two orders of magnitude lower than that of conventional Ti/Al/Ni/Au ohmic contacts.This innovation originates from expansion-bolt-like islands(shaped as inverted truncated pyramid—with extensive coverage and planar tops)formed during rapid thermal annealing(RTA)process,which are sufficiently dug into the two-dimensional electron gas(2DEG)channel.Distinct from traditional thumbtack-like morphology(resembling inverted cones),these expansion-bolt-like islands exhibit enhanced coverage to 2DEG channel,and planarized apex geometries that redistribute electric field,enabling 87%higher off-state breakdown voltage.This interface-driven strategy envisions a universal manufacturable paradigm for next-generation ultra-low-loss GaN power devices.展开更多
MXene-based smart contact lenses demonstrate a cutting-edge advancement in wearable ophthalmic technology,combining real-time biosensing,therapeutic capabilities,and user comfort in a single platform.These devices tak...MXene-based smart contact lenses demonstrate a cutting-edge advancement in wearable ophthalmic technology,combining real-time biosensing,therapeutic capabilities,and user comfort in a single platform.These devices take the advantage of the exceptional electrical conductivity,mechanical flexibility,and biocompatibility of two-dimensional MXenes to enable noninvasive,tear-based monitoring of key physiological markers such as intraocular pressure and glucose levels.Recent developments focus on the integration of transparent MXene films into the conventional lens materials,allowing multifunctional performance including photothermal therapy,antimicrobial and anti-inflammation protection,and dehydration resistance.These innovations offer promising strategies for ocular disease management and eye protection.In addition to their multifunctionality,improvements in MXene synthesis and device engineering have enhanced the stability,transparency,and wearability of these lenses.Despite these advances,challenges remain in long-term biostability,scalable production,and integration with wireless communication systems.This review summarizes the current progress,key challenges,and future directions of MXene-based smart contact lenses,highlighting their transformative potential in next-generation digital healthcare and ophthalmic care.展开更多
This work presents a methodology for modelling multibody systems with contact/impact events,considering angular inertia and energy dissipation,using a spinning top in contact with a flat surface as a case study.This s...This work presents a methodology for modelling multibody systems with contact/impact events,considering angular inertia and energy dissipation,using a spinning top in contact with a flat surface as a case study.This specific application is chosen due to its requirement for an extremely precise characterization of the contact interaction to ensure consistent results.The modelling process is carried out using smooth contact methods,incorporating the Hertz and Flores models for the normal force,and the Ambr´osio and Gonthier models for tangential friction.To propose this methodology,an analysis and comparison of different models of normal and tangential forces will be performed,aiming to identify their differences and determine which are more appropriate for the system under study.Additionally,the impact of a variable restitution coefficient solution proposed by Ma et al.on the system’s dynamics is evaluated.This model,which was developed and tested by a finite element method tool and experiments,is now integrated within the context of a multibody dynamics model.The analysis addresses the effect of contact modelling on the evolution of the motion and the stability of the top.The results show that models with dissipation accelerate the cessation of rebounds and generate tighter trajectories,while models without dissipation produce prolonged oscillations and wider trajectories.Moreover,the impact of model selection on computational cost is discussed.展开更多
To address the limitations of traditional silicone hydrogel contact lenses in wettability and drug release,an innovative approach was proposed by incorporating polyethylene glycol(PEG)and sodium hyaluronate(SH)into th...To address the limitations of traditional silicone hydrogel contact lenses in wettability and drug release,an innovative approach was proposed by incorporating polyethylene glycol(PEG)and sodium hyaluronate(SH)into these lenses.Aminoalkyl-terminated polydimethylsiloxane(KF8010)was reacted with glycidyl methacrylate(GMA)to synthesize GKF8010,which was then mixed with methacryloxymethyltris(trimethylsiloxy)silane(TRIS),N,N-Dimethylaniline(DMA),and PEG400 to fabricate PEG-modified silicone hydrogel contact lenses(PEG-SCL)via UV molding.Unmodified lenses(SCL)were served as controls.The effects of PEG modification on lens properties,including water content,wettability,and optical clarity,and SH loading efficiency and drug release were evaluated.Additionally,the protein adsorption and biocompatibility of the lenses with human umbilical vein endothelial cells(HUVECs)were assessed.Results indicated that PEGmodified lenses exhibited superior water content,reduced protein adsorption,enhanced SH loading capacity and controlled release profiles,highlighting their potential for treating dry eye syndrome.展开更多
This paper quantitatively discusses the influence of well contact on single-event transient(SET)in sub-20 nm FinFET by two-photon absorption(TPA)pulse laser.Two groups of inverter chains were designed to investigate t...This paper quantitatively discusses the influence of well contact on single-event transient(SET)in sub-20 nm FinFET by two-photon absorption(TPA)pulse laser.Two groups of inverter chains were designed to investigate the impact of well contact distance on the FinFET process.The experimental results show that the SET pulse width has a bimodal symmetric distribution,which is different from that of a bulk planar CMOS device.To investigate the detailed mechanism of the phenomenon,a high-precision FinFET TCAD model was established,in which both Id-Vd and Id-Vg errors were less than 10%compared to the SPICE model provided by the commercial process.TCAD simulation under heavy ion injection showed the mechanism of the abnormal phenomenon,where the well contact plays a major role in charge collection at the near-well contact distance,while the source plays a major role at the far distance.This phenomenon is completely different from that of planar CMOS devices.This indicates that the SET mechanism becomes more complicated during the FinFET process.Therefore,more effective SET hardening methods should be investigated for FinFET.展开更多
Two-dimensional Dirac semi-metals have attracted extensive attention for their potential applications in nextgeneration electronics,optoelectronics and quantum technologies.However,numerous topological semimetals pred...Two-dimensional Dirac semi-metals have attracted extensive attention for their potential applications in nextgeneration electronics,optoelectronics and quantum technologies.However,numerous topological semimetals predicted by theory have not yet been experimentally confirmed.Here,we report the controlled synthesis of high-quality NiTe nanosheets via the chemical vapor deposition method.Theoretical analysis confirms the semi-metallic nature of centrosymmetric NiTe and elucidates that its unusual second harmonic generation response originates from the electron transitions between linear dispersed bands near Dirac cone.Furthermore,NiTe nanosheets exhibit an ultra-high conductivity exceeding 10~6 S m-1,rivaling noble metal-based Dirac semimetals.Dirac semi-metallic NiTe serves as a contact electrode for MoS2field-effect transistors,showing a remarkable apparent carrier mobility of 22.45 cm2V-1s-1,which is 6.43 times higher than that of the Au-MoS2device.These findings establish NiTe as an ideal platform for exploring topological quantum states and advancing high-performance electronic devices.展开更多
The distribution of heat generation and operating temperature are crucial factors affecting the performance and useful service life of angular contact ball bearings.A thermodynamic real-time coupling analytical model ...The distribution of heat generation and operating temperature are crucial factors affecting the performance and useful service life of angular contact ball bearings.A thermodynamic real-time coupling analytical model is established in this work to illustrate alterations in the bearing structure,internal load,and the sliding and rotation of the ball correlated with temperature fluctuations.The temperature rise and heat generation of angular contact ball bearings under combined loads are accurately calculated.The simulation of the temperature rise in bearings is conducted based on this model,and the effectiveness of the model is validated through simulation experiments.The simulation results of the distribution of heat generation are compared between thermodynamic real-time coupling and thermodynamic sequential coupling,with a focus on the transient thermal characteristics of bearings and the effect of load on their steady-state thermal characteristics.The precision of temperature simulation through thermodynamic real-time coupling is significantly higher than that through thermodynamic sequential coupling.Axial load mainly affects heat generated by the sliding and rotation of the ball on the inner raceway,while radial load predominantly affects the heat generation of the ball due to sliding on the inner and outer raceways.The findings of the work can guide the design and performance evaluation of angular contact ball bearings and provide support for temperature simulation.展开更多
The issue of fatigue damage to rails has become increasingly prominent with the rise in subway traffic and speed.The hazardous space of the turnout frog significantly intensifies the dynamic interaction between the ve...The issue of fatigue damage to rails has become increasingly prominent with the rise in subway traffic and speed.The hazardous space of the turnout frog significantly intensifies the dynamic interaction between the vehicle and the frog rail,leading to more pronounced fatigue damage in the turnout rail.This paper focuses on the No.9 turnout fixed frog commonly used in subway lines.A three-dimensional explicit transient rolling contact finite element model of the fixed frog is established.The dynamic response of wheel-rail rolling contact is analyzed under various speeds and vertical stiffness conditions.Rolling contact fatigue crack locations,angles,and initiation life were investigated.The research indicates that the 30 mm top width cross-section of the nose rail is most susceptible to fatigue cracks,which initiate on the rail surface.The angle between the crack initiation surface and the lateral direction is between 70°and 95°.Higher speeds result in shorter fatigue life,while the vertical stiffness of the fastener has less of an effect.The simulation results align with findings from field surveys.The established model and research conclusions can provide theoretical support for optimizing fixed frog structures and predicting fatigue life.展开更多
Threaded connection is a common structural form in mechanical engineering,with their complex nonlinear behavior under combined loading critically affecting structural performance.While existing simplified models and f...Threaded connection is a common structural form in mechanical engineering,with their complex nonlinear behavior under combined loading critically affecting structural performance.While existing simplified models and finite element analysis(FEA)methods describe force distribution under single loading conditions,accurately modeling threaded connections under complex loading remains challenging.This paper proposes a simplified theoretical model to efficiently predict contact forces and deformation distributions under tension,torsion,bending,and shear.The model treats bolt and nut bodies as Euler-Bernoulli beams and represents thread stiffness using equivalent trapezoidal cantilever beams,reducing computational complexity while retaining essential mechanical characteristics.The paper introduces reference helical curves and derives a deformation coordination relationship based on contact constraints.The model’s calculations are validated against FEA results,demonstrating both high precision and significant computational efficiency under complex loading conditions.This work provides an efficient and reliable tool for analyzing threaded connections,offering promising engineering applications.展开更多
基金National Natural Science Foundation of China,12172249Ganyun Huang,12192212Ganyun Huang,Innovative Research Group Project of the National Natural Science Foundation of China,12021002。
摘要Adhesive interaction is a ubiquitous phenomenon in various aspects of nature and engineering,driving extensive research on adhesive contact over past decades.This brief review surveys adhesive contact models at the single-asperity level.Attention has been focused on how adhesive interaction is accounted for in models of normal contact,inclined contact,and contact with rolling tendency,and hence the corresponding interfacial tractions have been outlined.Perspectives on remaining challenges in adhesive contact mechanics have also been summarized.
基金funded by the Department of Science and Technology,Government of India.
摘要This paper investigates the contact problem of an air-inflated circular membrane with a finite rigid indentor having three different geometric profiles,namely flat-face,conical,and spherical.Initially,the axisymmetric inflation problem of a thin circular mem-brane is studied under uniform pressurization.The material is assumed to be homogeneous,isotropic,and incompressible,which is described by the two-parameter Mooney-Rivlin hyperelastic model.An indentor with finite radius is pressed quasi-statically against the inflated membrane,preserving the axisymmetric nature of deformation.The contact problem is formulated for both frictionless and no-slip contact conditions.A set of coupled nonlinear second order partial differential equations for both contact and non-contact regions are solved using a shooting method coupled with an optimization algorithm.The inflated membrane profiles in contact with different indentor geometries,principal stretch ratios,and Cauchy stress resultants are obtained.The possibility of having multiple contact zones and their interaction on different faces of the indentor is also explored.The force-displacement(stiffness)curves for this finite indentor contact problem show the existence of a critical contact force,which limits the force bearing capacity of the inflated structure.This critical force is found to be higher for larger strain-hardening of the material and higher indentor radius.The junction of contact and non-contact regions for flat-faced and conical indentors is found to be the critical section due to slope discontinuity.However,for the spherical indentor,the pole of the membrane is most prone to rupture due to membrane thinning effect.
基金Project(2024YFB3410402)supported by the National Key R&D Program of ChinaProject(52075558)supported by the National Natural Science Foundation of China+2 种基金Project(2021RC3012)supported by the Science and Technology Innovation Program of Hunan Province,ChinaProject(2023CXQD050)supported by the Central South University Innovation-Driven Research Program,ChinaProject(CX20230255)supported by the Fundamental Research Funds for the Central Universities,China。
摘要This study develops a contact performance-driven method for skiving face gear drives using a single cutter,eliminating the traditional need for separate cutters to reduce production costs and time.First,the mathematical models of the tooth flanks for the face gear drives are established based on the gear skiving processes.Then,load tooth contact analysis(LTCA)model is established to calculate the contact performance data.Next,a two-stage optimization model is employed to determine the optimal parameters of the cutting edge with improved contact performances.The effectiveness of this method is validated through simulations and rolling tests.Compared with the traditional method,the proposed method can machine both the face gear and its mating pinion with a single cutter.Simulation results show that the proposed method avoids tooth surface edge contact,with the maximum tooth surface contact stress reduced by 31.7%,the contact ratio decreases by 21.5%,and the transmission error increases by 22.3%.Rolling tests verify the consistency of tooth surface contact patterns between simulations and experiments.The proposed method provides a reference for the cutting edge design of skiving cutters for face gear pairs.
基金the support of KAUST Baseline Fund BAS/1/1664-01-01KAUST Competitive Research Grants URF/1/3437-01-01,KAUST Competitive Research Grants URF/1/3771-01-01+1 种基金KAUST Near-term Grand Challenge Fund REI/1/4999-01-01KAUST Impact Acceleration Fund REI/1/5124-01-01。
摘要Al-rich AlxGa1-xN(x≥0.8)is promising for power and deep-ultraviolet(DUV)optoelectronic applications,owing to its ultra-wide bandgap and excellent thermal stability.However,forming low-resistivity contacts on n-type Al-rich AlGaN remains a significant challenge.In this work,we utilized an Au-free Ti/Al/Ti metal stack contact on n-type Al-rich AlGaN without graded layers.Record-low contact resistivities were achieved after annealing:1.52×10-6Ω·cm2for n-Al0.8Ga0.2N,3.56×10-6Ω·cm2for n-Al0.86Ga0.14N,and 5.79×10-5Ω·cm2for n-Al0.9Ga0.1N.These results demonstrate a significant advancement in forming low-resistance contacts directly on Al-rich n-AlGaN,offering a viable path forward for next-generation power electronics and DUV optoelectronic devices.
基金supported by the National Natural Science Foundation of China(Grants Nos.12172181 and 12232011)the Qing Lan Project of Jiangsu Province of China.
摘要Revolute joints are widely used in various engineering fields such as deployable space structures and robotics.Currently,various theoretical models have been applied to evaluate the normal contact force of the revolute joints;however,the results obtained by these models often exhibit significant discrepancies,and there is a lack of explanation for the reasons behind these discrepancies.This study explores the underlying theories of three classical non-conformal contact force models for revolute joints,namely the ESDU-78035 model,the Radzimovsky model,and the Dubowsky-Freudenstein model.The theoretical differences among these classical models are analyzed,and their deficiencies are discovered,and then an improved non-conformal normal contact force model is presented.To validate the accuracy of the presented model,three-dimensional refined finite element models employing surface-to-surface contact elements are constructed to simulate the normal contact of the revolute joint with different clearance sizes and different contact lengths.A comprehensive comparison is carried out between the semi-contact-width,contact pressure,and load-deformation curves obtained from the theoretical models and the finite element model.The results indicate that the presented contact force model outperforms the three classical contact force models in terms of accuracy.The differences between the ideal contact model and the real revolute joint are also investigated,and a sub-model modeling method is presented for the real revolute joint based on the ideal contact force model.
基金National Natural Science Foundation of China,Grant/Award Number:52304239Natural Science Foundation of Shandong Province,Grant/Award Numbers:ZR2021MD016,ZR2023QD026。
摘要Fluid flow through a single fracture is commonly described by the cubic law.However,deviations from this model are expected because natural fracture surfaces are rough and in contact with each other in discrete regions.In this study,the interactions between fracture closure,contact area,and hydraulic characterization of mesoscopic-scale rough fractures were investigated.First,natural-splitting fractures induced by Brazilian splitting were generated and digitally reproduced using a three-dimensional scanner.The distribution characterization of the initial mechanical fracture apertures was described,and the variation in fracture contact area during fracture closure was evaluated.Second,numerical simulations of fluid flow between rough surfaces were conducted,and the Stokes equations were solved.The results reveal that the hydraulic aperture underwent three stages.When the contact area was less than 0.34%,changes in the hydraulic aperture resulted in flow rate changes that were consistent with the cubic law.When the contact area was between 0.34%and 14.41%,the hydraulic aperture gradually deviated from the cubic law and fell below the mean fracture aperture.At this stage,the hydraulic aperture should be fully considered rather than the mean fracture aperture.When the contact area exceeds 14.41%,although the mechanical fracture decreases with increasing strain,the influence of the contact area on the hydraulic aperture gradually diminishes.This is because the fractures contain less fluid,and the hydraulic aperture approaches the minimum.Finally,the relationship between mechanical and hydraulic aperture strains was established,improving geological engineering applications that account for fracture deformation.
基金support from the National Natural Science Foundation of China(Grant Nos.42277161 and 42230709).
摘要In rock engineering,natural cracks in rock masses subjected to external loads tend to initiate and propagate,leading to potential safety hazards.To investigate the effect of cracking behavior on the mechanical properties of rocks,the cracking processes of pre-cracked rocks have been extensively studied using numerical modeling methods.The peridynamics(PD)exhibits advantages over other numerical methods due to the absence of the requirements for remeshing and external crack growth criterion.However,for modeling pre-cracked rock cracking processes under impact,current PD implementations lack generally applicable rock constitutive models and impact contact models,which leads to difficulties in determining rock material parameters and efficiently calculating impact loads.This paper proposes a non-ordinary state-based peridynamics(NOSBPD)modeling method integrating the Drucker-Prager(DP)plasticity model and an efficient contact model to address the above problems.In the proposed method,the Drucker-Prager plasticity model is integrated into the NOSBPD,thereby equipping NOSBPD with the capability to accurately characterize the nonlinear stress-strain relationship inherent in rocks.An efficient contact model between particles and meshes is designed to calculate the impact loads,which is essentially a coupling method of PD with the finite element method(FEM).The effectiveness of the proposed NOSBPD modeling method is verified by comparison with other numerical methods and experiments.Experimental results indicate that the proposed method can effectively and accurately predict the 3D cracking processes of pre-cracked cracks under impact loading,and the maximum principal stress is the key driver behind wing crack formation in pre-cracked rocks.
基金Project(52372391)supported by the National Natural Science Foundation of ChinaProject(2024YFB4303301)supported by the National Key Research and Development Program of ChinaProject(2022CYY006)supported by the Research Fund of CRRC Corporation Limited,China。
摘要The accuracy of wheel-rail rolling contact force is of great significance for vehicle dynamics simulation.A wheel-rail rolling contact behavior model considering wheelset yaw is proposed.The NORM algorithm is adopted to solve the wheel-rail normal contact problem.The extended creep force model(ECF)is used for the tangential contact problem,which considers different interfacial conditions,temperature in the contact area,and the elastoplastic behavior of the third body.A fatigue life prediction framework based on the critical plane method is introduced to evaluate the contact fatigue damage under the coupled influence of yaw angle and interfacial conditions.The effects of wheel yaw angle on the contact pressure and wheel-rail rolling contact fatigue life under dry and wet conditions are investigated.The results show that under both dry and wet conditions,increasing yaw angle leads to an increase in creepage,expansion of the sliding area,enhancement of creep force,and a simultaneous increase in the contact area temperature,thereby causing an increase in the fatigue parameter(FP).The wheel-rail rolling contact life with yaw angle is shortened compared to that without yaw,and the life decay rate under wet condition is slower than that under dry condition.
基金co-supported by the National Natural Science Foundation of China(Nos.52275165 and 52305146)the Sichuan Science and Technology Program,China(Nos.2023YFG0165 and 2023NSFSC0372)+1 种基金the Sichuan Province Engineering Technology Research Center of General Aircraft Maintenance Project,China(No.GAMRC2023ZD03)the Student Innovation Fund Project,China(No.24CAFUC10202)。
摘要This paper investigates the “brush-like”deformation phenomenon of the contact interface at the bolt-hole during the interference-fit installation of high-locking bolts under static loading in CFRP connection structures.An innovative theoretical model is proposed to predict axial installation force,specifically designed for moderate interference-fit.This model is based on the “brush-like”deformation of the hole wall,with the axial installation force predicted through force analysis and theoretical calculations,effectively overcoming the limitations of prior models that idealized the contact interface at the bolt-hole.The predictions generated by this theoretical model align closely with experimental data,confirming its efficacy in accurately forecasting the curve of installation force for interferencefit bolts during the static installation within the moderate interference-fit range.Additionally,a comprehensive analysis of the relationship between deformation of the hole wall and curves of installation force across small,moderate,and large interference-fit levels are presented.It is demonstrated that the degree of deformation within the moderate interference-fit range is more suitable than that in the small and large interference-fit ranges,making it a reliable alternative for installation force tests within this range during static installation.The moderate interference-fit domain[1.00%,1.24%]is established as a validated and optimal range of interference-fit bolts for the static installation.
基金supported by National Key Research and Development Program of China(No.2023YFB3609800)National Natural Science Foundation of China(No.62304244)+3 种基金China Postdoctoral Science Foundation(No.2025M780550)Frontier Technologies R&D Program of Jiangsu(No.BF2025032)Natural Science Foundation of Jiangsu Province(No.BK20230235)Suzhou Key Core Technology Project:Leading the Charge with Open Competition(No.SYG2024104)。
摘要Achieving high emission efficiency at low current densities remains a challenge for micro-LEDs.Here,we demonstrate a controllable interfacial strategy by tuning the annealing temperature of RF-superimposed DC sputtered ITO to modulate carrier injection dynamics.STEM analysis reveals 500℃ annealing triggers discrete substitutional In-atom incorporation into the p-GaN lattice,forming localized nanoscale contact regions.This architecture induces a localized carrier injection mechanism that significantly enhances the efficiency of micro-LEDs at low current densities.Specifically,the 500℃-annealed 10μm devices exhibit a dramatic enhancement in light output power(LOP),reaching 1.3×10-1 mW at 5 A/cm2,which is significantly higher than the 5.3×10-4 mW measured for 700°C-annealed devices.Furthermore,the peak efficiency current density(Jpeak)is dramatically shifted from 140 to 17 A/cm2 for 5μm devices.Capacitance-voltage analysis further corroborates the localized carrier injection mechanism.These findings establish contact interfacial modulation as a robust strategy for optimizing micro-LEDs in low-power display applications and tailoring device-level performance across broader optoelectronics.
基金Supported by National Natural Science Foundation of China (Grant Nos.52072317,52302474)Liaoning Provincial Revitalization Talents Program (Grant No.XLYC2403115)+2 种基金State Key Laboratory of Rail Transit Vehicle System Program (Grant No.RVL2513)the Fundamental Research Funds for Liaoning Provincial Universities (Grant No.LJ232410150023)the Department of Education of Hebei Province (Grant No.BJK2024052)。
摘要Metro line has the characteristics of short station distance,low operating speed,frequent traction/braking,high acceleration and deceleration,small curve radius and various track types.The wheel-rail low adhesion behavior,wear and damage problems are prominent under such a complicated operation condition.This article compares and analyzes the wheel-rail adhesion characteristic on four kinds of tracks,including the concrete slab bed track,steel-spring floating slab track,elastic support block track and trapezoidal sleeper track,revealing the adhesion degradation mechanism of metro wheel-rail system under different operating conditions,such as traction and braking.The results indicate that there are differences in the creepage response and the lowest limit of the wheel-rail adhesion coefficient on different track structures,while the maximum adhesion coefficient of the four track structures under traction/braking conditions shows a similar trend with the variation in speed and adhesion conditions.Traction and braking loads,as well as wheel-rail adhesion conditions,exert a relatively minor influence on the normal contact stress distribution of the wheel-rail interface,but significantly affect shear stress distributions.This study is shown to enhance the understanding of the combined effects of adhesion degradation and track types on the wheel-rail contact stress and surface damage.
基金financially supported by the National Natural Science Foundation of China(Grant No.52192611)Beijing Natural Science Foundation(Grant No.Z230024).
摘要The transformative potential of gallium nitride high electron mobility transistors(GaN HEMTs)in advancing carbon-neutral power systems remains bottlenecked by contact resistance(Rc)at the metal-semiconductor(M-S)interface,a critical determinant of switching losses and frequency response.Herein,by engineering a TiAl/TiAlTa/Au metastructure,we propose a novel interface-driven strategy employing Ta-mediated interfacial reconstruction to achieve a record-low Rc of 0.07Ωmm,which is two orders of magnitude lower than that of conventional Ti/Al/Ni/Au ohmic contacts.This innovation originates from expansion-bolt-like islands(shaped as inverted truncated pyramid—with extensive coverage and planar tops)formed during rapid thermal annealing(RTA)process,which are sufficiently dug into the two-dimensional electron gas(2DEG)channel.Distinct from traditional thumbtack-like morphology(resembling inverted cones),these expansion-bolt-like islands exhibit enhanced coverage to 2DEG channel,and planarized apex geometries that redistribute electric field,enabling 87%higher off-state breakdown voltage.This interface-driven strategy envisions a universal manufacturable paradigm for next-generation ultra-low-loss GaN power devices.
摘要MXene-based smart contact lenses demonstrate a cutting-edge advancement in wearable ophthalmic technology,combining real-time biosensing,therapeutic capabilities,and user comfort in a single platform.These devices take the advantage of the exceptional electrical conductivity,mechanical flexibility,and biocompatibility of two-dimensional MXenes to enable noninvasive,tear-based monitoring of key physiological markers such as intraocular pressure and glucose levels.Recent developments focus on the integration of transparent MXene films into the conventional lens materials,allowing multifunctional performance including photothermal therapy,antimicrobial and anti-inflammation protection,and dehydration resistance.These innovations offer promising strategies for ocular disease management and eye protection.In addition to their multifunctionality,improvements in MXene synthesis and device engineering have enhanced the stability,transparency,and wearability of these lenses.Despite these advances,challenges remain in long-term biostability,scalable production,and integration with wireless communication systems.This review summarizes the current progress,key challenges,and future directions of MXene-based smart contact lenses,highlighting their transformative potential in next-generation digital healthcare and ophthalmic care.
基金supported by the part of the projects managed by the projects MEMRIAAP-CM-UC3M(managed by the Community of Madrid)TED2021-131372A-I00 and PID2020-116984RB-C22(managed by the Spanish Ministry of Science and Innovation-MCIN/AEI/10.13039/501100011033-).
摘要This work presents a methodology for modelling multibody systems with contact/impact events,considering angular inertia and energy dissipation,using a spinning top in contact with a flat surface as a case study.This specific application is chosen due to its requirement for an extremely precise characterization of the contact interaction to ensure consistent results.The modelling process is carried out using smooth contact methods,incorporating the Hertz and Flores models for the normal force,and the Ambr´osio and Gonthier models for tangential friction.To propose this methodology,an analysis and comparison of different models of normal and tangential forces will be performed,aiming to identify their differences and determine which are more appropriate for the system under study.Additionally,the impact of a variable restitution coefficient solution proposed by Ma et al.on the system’s dynamics is evaluated.This model,which was developed and tested by a finite element method tool and experiments,is now integrated within the context of a multibody dynamics model.The analysis addresses the effect of contact modelling on the evolution of the motion and the stability of the top.The results show that models with dissipation accelerate the cessation of rebounds and generate tighter trajectories,while models without dissipation produce prolonged oscillations and wider trajectories.Moreover,the impact of model selection on computational cost is discussed.
基金Funded by the industry-academia-research cooperation projects in Jiangsu Province(No.BY20231084)the University-Industry Collaboration Project(No.jit-h-2025-016)the Nanjing Optometric New Materials and Application Technology Innovation Team。
摘要To address the limitations of traditional silicone hydrogel contact lenses in wettability and drug release,an innovative approach was proposed by incorporating polyethylene glycol(PEG)and sodium hyaluronate(SH)into these lenses.Aminoalkyl-terminated polydimethylsiloxane(KF8010)was reacted with glycidyl methacrylate(GMA)to synthesize GKF8010,which was then mixed with methacryloxymethyltris(trimethylsiloxy)silane(TRIS),N,N-Dimethylaniline(DMA),and PEG400 to fabricate PEG-modified silicone hydrogel contact lenses(PEG-SCL)via UV molding.Unmodified lenses(SCL)were served as controls.The effects of PEG modification on lens properties,including water content,wettability,and optical clarity,and SH loading efficiency and drug release were evaluated.Additionally,the protein adsorption and biocompatibility of the lenses with human umbilical vein endothelial cells(HUVECs)were assessed.Results indicated that PEGmodified lenses exhibited superior water content,reduced protein adsorption,enhanced SH loading capacity and controlled release profiles,highlighting their potential for treating dry eye syndrome.
基金supported by Natural Science Foundation of China(Nos.62174180 and 62304258)National Key R&D Program of China(No.2023YFA1609000)。
摘要This paper quantitatively discusses the influence of well contact on single-event transient(SET)in sub-20 nm FinFET by two-photon absorption(TPA)pulse laser.Two groups of inverter chains were designed to investigate the impact of well contact distance on the FinFET process.The experimental results show that the SET pulse width has a bimodal symmetric distribution,which is different from that of a bulk planar CMOS device.To investigate the detailed mechanism of the phenomenon,a high-precision FinFET TCAD model was established,in which both Id-Vd and Id-Vg errors were less than 10%compared to the SPICE model provided by the commercial process.TCAD simulation under heavy ion injection showed the mechanism of the abnormal phenomenon,where the well contact plays a major role in charge collection at the near-well contact distance,while the source plays a major role at the far distance.This phenomenon is completely different from that of planar CMOS devices.This indicates that the SET mechanism becomes more complicated during the FinFET process.Therefore,more effective SET hardening methods should be investigated for FinFET.
基金granted by the National Key R&D Program of the Ministry of Science and Technology of China(No.2022YFA1203801)National Natural Science Foundation of China(No.52221001)Open Research Fund of Suzhou Laboratory(No.SZLAB-1508-2024TS013)。
摘要Two-dimensional Dirac semi-metals have attracted extensive attention for their potential applications in nextgeneration electronics,optoelectronics and quantum technologies.However,numerous topological semimetals predicted by theory have not yet been experimentally confirmed.Here,we report the controlled synthesis of high-quality NiTe nanosheets via the chemical vapor deposition method.Theoretical analysis confirms the semi-metallic nature of centrosymmetric NiTe and elucidates that its unusual second harmonic generation response originates from the electron transitions between linear dispersed bands near Dirac cone.Furthermore,NiTe nanosheets exhibit an ultra-high conductivity exceeding 10~6 S m-1,rivaling noble metal-based Dirac semimetals.Dirac semi-metallic NiTe serves as a contact electrode for MoS2field-effect transistors,showing a remarkable apparent carrier mobility of 22.45 cm2V-1s-1,which is 6.43 times higher than that of the Au-MoS2device.These findings establish NiTe as an ideal platform for exploring topological quantum states and advancing high-performance electronic devices.
基金funded by the National Natural Science Foundation of China(Grant Nos.52365010,52262049,and 52475087)Jiangxi Provincial Natural Science Foundation Project(Grant No.20242BAB25262).
摘要The distribution of heat generation and operating temperature are crucial factors affecting the performance and useful service life of angular contact ball bearings.A thermodynamic real-time coupling analytical model is established in this work to illustrate alterations in the bearing structure,internal load,and the sliding and rotation of the ball correlated with temperature fluctuations.The temperature rise and heat generation of angular contact ball bearings under combined loads are accurately calculated.The simulation of the temperature rise in bearings is conducted based on this model,and the effectiveness of the model is validated through simulation experiments.The simulation results of the distribution of heat generation are compared between thermodynamic real-time coupling and thermodynamic sequential coupling,with a focus on the transient thermal characteristics of bearings and the effect of load on their steady-state thermal characteristics.The precision of temperature simulation through thermodynamic real-time coupling is significantly higher than that through thermodynamic sequential coupling.Axial load mainly affects heat generated by the sliding and rotation of the ball on the inner raceway,while radial load predominantly affects the heat generation of the ball due to sliding on the inner and outer raceways.The findings of the work can guide the design and performance evaluation of angular contact ball bearings and provide support for temperature simulation.
基金supported by the National Key R&D Program of China(No.2023YFB2603702)the National Natural Science Foundation of China(Nos.52472458,52478474,and 52388102)+1 种基金Sichuan Science and Technology Program(Nos.2025NSFTD0013,2025YFHZ0035,2024NSFTD0010,and 2025ZNSFSC1318)Major Program of Sichuan Provincial Natural Science Foundation of China(No.2024NSFSC0003)。
摘要The issue of fatigue damage to rails has become increasingly prominent with the rise in subway traffic and speed.The hazardous space of the turnout frog significantly intensifies the dynamic interaction between the vehicle and the frog rail,leading to more pronounced fatigue damage in the turnout rail.This paper focuses on the No.9 turnout fixed frog commonly used in subway lines.A three-dimensional explicit transient rolling contact finite element model of the fixed frog is established.The dynamic response of wheel-rail rolling contact is analyzed under various speeds and vertical stiffness conditions.Rolling contact fatigue crack locations,angles,and initiation life were investigated.The research indicates that the 30 mm top width cross-section of the nose rail is most susceptible to fatigue cracks,which initiate on the rail surface.The angle between the crack initiation surface and the lateral direction is between 70°and 95°.Higher speeds result in shorter fatigue life,while the vertical stiffness of the fastener has less of an effect.The simulation results align with findings from field surveys.The established model and research conclusions can provide theoretical support for optimizing fixed frog structures and predicting fatigue life.
基金supported by the National Natural Science Foundation of China(Grant Nos.11932001,U2241264,and 12272003).
摘要Threaded connection is a common structural form in mechanical engineering,with their complex nonlinear behavior under combined loading critically affecting structural performance.While existing simplified models and finite element analysis(FEA)methods describe force distribution under single loading conditions,accurately modeling threaded connections under complex loading remains challenging.This paper proposes a simplified theoretical model to efficiently predict contact forces and deformation distributions under tension,torsion,bending,and shear.The model treats bolt and nut bodies as Euler-Bernoulli beams and represents thread stiffness using equivalent trapezoidal cantilever beams,reducing computational complexity while retaining essential mechanical characteristics.The paper introduces reference helical curves and derives a deformation coordination relationship based on contact constraints.The model’s calculations are validated against FEA results,demonstrating both high precision and significant computational efficiency under complex loading conditions.This work provides an efficient and reliable tool for analyzing threaded connections,offering promising engineering applications.