The deformation caused by tunnel excavation is quite important for safety,especially when it is adjacent to the existing tunnel.Nevertheless,the investigation of deformation characteristics in overlapped curved shield...The deformation caused by tunnel excavation is quite important for safety,especially when it is adjacent to the existing tunnel.Nevertheless,the investigation of deformation characteristics in overlapped curved shield tunneling remains inadequate.The analytical solution for calculating the deformation of the ground and existing tunnel induced by overlapped curved shield tunneling is derived by the Mirror theory,Mindlin solution and Euler-Bernoulli-Pasternak model,subsequently validated through both finite element simulation and field monitoring.It is determined that the overcutting plays a crucial role in the ground settlement resulting from curved shield tunneling compared to straight shield tunneling.The longitudinal settlement distribution can be categorized into five areas,with the area near the tunnel surface experiencing the most dramatic settlement changes.The deformation of the existing tunnel varies most significantly with turning radius compared to tunnel clearance and grouting pressure,especially when the turning radius is less than 30 times the tunnel diameter.The tunnel crown exhibits larger displacement than the tunnel bottom,resulting in a distinctive‘vertical egg'shape.Furthermore,an optimized overcutting mode is proposed,involving precise control of the extension speed and angular velocity of the overcutting cutter,which effectively mitigates ground deformation,ensuring the protection of the existing tunnel during the construction.展开更多
Due to their superior properties, the interest in nanostructures is increasing today in engineering. This study presents a new two-noded curved finite element for analyzing the in-plane static behaviors of curved nano...Due to their superior properties, the interest in nanostructures is increasing today in engineering. This study presents a new two-noded curved finite element for analyzing the in-plane static behaviors of curved nanobeams. Opposite to traditional curved finite elements developed by using approximate interpolation functions, the proposed curved finite element is developed by using exact analytical solutions. Although this approach was first introduced for analyzing the mechanical behaviors of macro-scale curved beams by adopting the local theory of elasticity, the exact analytical expressions used in this study were obtained from the solutions of governing equations that were expressed via the differential form of the nonlocal theory of elasticity. Therefore, the effects of shear strain and axial extension included in the analytical formulation are also inherited by the curved finite element developed here. The rigidity matrix and the consistent force vector are developed for a circular finite element. To demonstrate the applicability of the method, static analyses of various curved nanobeams subjected to different boundary conditions and loading scenarios are performed, and the obtained results are compared with the exact analytical ones. The presented study provides an accurate and low computational cost method for researchers to investigate the in-plane static behavior of curved nanobeams.展开更多
Traditional manufacturing processes for lightweight curved profiles are often associated with lengthy procedures,high costs,low efficiency,and high energy consumption.In order to solve this problem,a new staggered ext...Traditional manufacturing processes for lightweight curved profiles are often associated with lengthy procedures,high costs,low efficiency,and high energy consumption.In order to solve this problem,a new staggered extrusion(SE)process was used to form the curved profile of AZ31 magnesium alloy in this paper.The study investigates the mapping relationship between the curvature,microstructure,and mechanical properties of the formed profiles by using different eccentricities of the die.Scanning electron microscopy(SEM)and electron backscatter diffraction techniques are employed to examine the effects of different eccentricity values(e)on grain morphology,recrystallization mechanisms,texture,and Schmid factors of the products.The results demonstrate that the staggered extrusion method promotes the deep refinement of grain size in the extruded products,with an average grain size of only 15%of the original billet,reaching 12.28μm.The tensile strength and elongation of the curved profiles after extrusion under the eccentricity value of 10 mm,20 mm and 30 mm are significantly higher than those of the billet,with the tensile strength is increased to 250,270,235 MPa,and the engineering strain elongation increased to 10.5%,12.1%,15.9%.This indicates that staggered extrusion enables curvature control of the profiles while improving their strength.展开更多
The fracture mechanics theory posits that cracks induce strain energy concentration near their tips in structural components,generating localized flexibility that impedes crack propagation.Theoretically,cracks are rep...The fracture mechanics theory posits that cracks induce strain energy concentration near their tips in structural components,generating localized flexibility that impedes crack propagation.Theoretically,cracks are represented as dimensionless,massless spring models,effectively capturing crack characteristics and cross-sectional properties at the crack location.Leveraging this spring-based representation,this study establishes an open-crack model for a one-dimensional(1D)piezoelectric semiconductor(PSC)curved beam under dynamic loading.This model enables the investigation of vibration characteristics in cracked structures.The analytical solutions for the electromechanical fields of the beam are derived using the differential operator method,and the natural frequencies together with the corresponding generalized mode shapes of the beam are determined analytically.Furthermore,the effects of the crack parameters on the natural vibration characteristics of the PSC curved beam are analyzed.展开更多
The effect of seismic directionality is crucial for curved bridges,a subject generally overlooked in seismic vulnerability analysis.This paper focuses on seismic fragility development as a function of seismic incidenc...The effect of seismic directionality is crucial for curved bridges,a subject generally overlooked in seismic vulnerability analysis.This paper focuses on seismic fragility development as a function of seismic incidence directions for a geometrically curved bridge.A series of non-linear time history analyses were carried out for a representative finite element model of the bridge by considering actual ground motions.For reliable seismic demand models,a total of eleven intensity measures(IM)were analyzed based on optimality metrics.To quantify the sensitivity of fragility functions to input incidence directions,fragility surfaces were developed throughout the horizontal plane by considering spectral acceleration at one second(Sa_(1.0))as the optimal IM.Results show that the optimal IM ranking is insignificantly influenced by seismic directionality.However,seismic orientation influences fragility,which intensifies in higher damage states,particularly for piers.For a bridge system,the differences in median demand corresponding to the least and most vulnerable direction for slight,moderate,extensive,and collapse states are about 9.0%,7.31%,10.32%,and 11.60%,respectively.These results imply that while evaluating the vulnerability of curved bridges,the optimality of IM in demand estimation and the impact of seismic directionality should not be disregarded.展开更多
Magnesium alloys with long-period stacking ordered(LPSO)structures are known for their impressive static mechanical strength,but the consistent occurrence of slip-cracking along the LPSO lamellae,which do not effectiv...Magnesium alloys with long-period stacking ordered(LPSO)structures are known for their impressive static mechanical strength,but the consistent occurrence of slip-cracking along the LPSO lamellae,which do not effectively impede the movement of basal dislocations,has prompted concerns about their very high cycle fatigue(VHCF)performance.In this study,an extruded Mg-Gd-Zn-Zr alloy was developed,showcasing exceptional VHCF resistance due to its bimodal structure comprisingfine grains and coarse grains consisting of curved LPSO lamellae.The investigation on the crack initiation mechanism revealed that slip-induced cracking predominantly occurs infine-grained regions rather than in the interior of coarse grains.The extrusion process aligns the basal planes of most coarse grains parallel to the axial direction,and the presence of curved LPSO lamellae acts as barriers to the movement of basal dislocations,thereby effectively increasing the threshold for slip-cracking along the basal plane.Consequently,fatigue damage manifests in the form of slip bands and micro-cracks within the interior offine grains,ultimately resulting in fatigue crack initiation,propagation andfinal fracture.展开更多
Curved beams with complex geometries are vital in numerous engineering applications,where precise vibration analysis is crucial for ensuring safe and effective designs.Traditional finite element methods(FEMs) often st...Curved beams with complex geometries are vital in numerous engineering applications,where precise vibration analysis is crucial for ensuring safe and effective designs.Traditional finite element methods(FEMs) often struggle to accurately represent the dynamic characteristics of these structures due to the limitations in their shape function approximations.To overcome this challenge,the current study introduces an innovative finite element(FE)-based technique for the undamped vibrational analysis of curved beams with arbitrary curvature,employing explicitly derived interpolation functions.Initially,the exact interpolation functions are developed for circular are elements with the force method.These functions facilitate the creation of a highly accurate stiffness matrix,which is validated against the benchmark examples.To accommodate arbitrary curvature,a systematic transformation technique is established to approximate the intricate curves with a series of circular arcs.The numerical findings indicate that increasing the number of arc segments enhances accuracy,approaching the exact solutions.The analysis of free vibrations is conducted for both circular and non-circular beams.Mass matrices are derived using two methods:lumped mass and consistent mass,where the latter is based on the interpolation functions.The effectiveness of the proposed method is confirmed through the comparisons with the existing literature,demonstrating strong agreement.Finally,several practical cases involving beams with diverse curvature profiles are analyzed.Both natural frequencies and mode shapes are determined,providing significant insights into the dynamic behavior of these structures.This research offers a dependable and efficient analytical framework for the vibrational analysis of complex curved beams,with promising implications for structural and mechanical engineering.展开更多
Arterial stenosis is a critical condition with increasing prevalence among pediatric patients and young adults,making its investigation highly significant.Despite extensive studies on blood flow dynamics,limited resea...Arterial stenosis is a critical condition with increasing prevalence among pediatric patients and young adults,making its investigation highly significant.Despite extensive studies on blood flow dynamics,limited research addresses the combined effects of nanoparticles and arterial curvature on unsteady pulsatile flow through multiple stenoses.This study aims to analyze the influence of nanoparticles on blood flow characteristics in realistic curved arteries with mild to severe overlapped constrictions.Using curvilinear coordinates,the thermal energy and momentum equations for nanoparticle-laden blood were derived,and numerical results were obtained through an explicit finite difference method.Key findings reveal that nanoparticle injections reduce blood temperature intensity,while arterial curvature strongly affects flow symmetry.Moreover,temperature,axial velocity,wall shear stress,and volumetric flow rate decrease significantly in severe stenosis compared to mild and moderate cases.These results provide new insights into nanoparticle-assisted blood flow under complex stenotic conditions and may contribute to improved diagnostic and therapeutic strategies for cardiovascular diseases.展开更多
In this study,an improved integrated radial basis function with nonuniform shape parameter is introduced.The proposed shape parameter varies in each support domain and is defined byθ=1/d_(max),where d_(max)is the max...In this study,an improved integrated radial basis function with nonuniform shape parameter is introduced.The proposed shape parameter varies in each support domain and is defined byθ=1/d_(max),where d_(max)is the maximum distance of any pair of nodes in the support domain.The proposed method is verified and shows good performance.The results are stable and accurate with any number of nodes and an arbitrary nodal distribution.Notably,the support domain should be large enough to obtain accurate results.This method is then applied for transient analysis of curved shell structures made from functionally graded materials with complex geometries.Through several numerical examples,the accuracy of the proposed approach is demonstrated and discussed.Additionally,the influence of various factors on the dynamic behavior of the structures,including the power-law index,different materials,loading conditions,and geometrical parameters of the structures,was investigated.展开更多
Recent advances in bone regeneration have introduced the concept of four-dimensional(4D)scaffolds that can undergo morphological and functional changes in response to external stimuli.While several studies have propos...Recent advances in bone regeneration have introduced the concept of four-dimensional(4D)scaffolds that can undergo morphological and functional changes in response to external stimuli.While several studies have proposed patient-specific designs for defect sites,they often fail to adequately distinguish the advantages of 4D scaffolds over conventional 3D counterparts.This study aimed to investigate the potential benefits of 4D scaffolds in clinically challenging scenarios involving curved defects,where fixation is difficult.We proposed the use of Shape-Memory Polymers(SMPs)as a solution to address critical issues in personalized scaffold fabrication,including dimensional accuracy,measurement error,and manufacturing imprecision.Experimental results demonstrated that the Curved-Layer Fused Deposition Modeling(CLFDM)scaffold,which offers superior conformability to curved defects,achieved significantly higher interfacial contact with the defect area compared to traditional Fused Deposition Modeling(FDM)scaffolds.Specifically,the CLFDM scaffold facilitated bone regeneration of 25.59±4.72 mm^(3),which is more than twice the 9.37±1.36 mm^(3)observed with the 3D FDM scaffold.Furthermore,the 4D CLFDM scaffold achieved 75.38±11.65 mm^(3)of new bone formation after four weeks,approximately three times greater than that of the 3D CLFDM scaffold,regardless of surface micro-roughness.These results underscore that improved geometrical conformity between the scaffold and the defect site enhances cellular infiltration and contributes to more effective bone regeneration.The findings also highlight the promise of 4D scaffolds as a compelling strategy to overcome geometric and dimensional mismatches in the design of patient-specific scaffolds.展开更多
On-machine measurement(OMM)stands out as a pivotal technology in complex curved surface adaptive machining.However,the complex structure inherent in workpieces poses a significant challenge as the stylus orientation f...On-machine measurement(OMM)stands out as a pivotal technology in complex curved surface adaptive machining.However,the complex structure inherent in workpieces poses a significant challenge as the stylus orientation frequently shifts during the measurement process.Consequently,a substantial amount of time is allocated to calibrating pre-travel error and probe movement.Furthermore,the frequent movement of machine tools also increases the influence of machine errors.To enhance both accuracy and efficiency,an optimization strategy for the OMM process is proposed.Based on the kinematic chain of the machine tools,the relationship between the angle combination of rotary axes,the stylus orientation,and the calibration position of pre-travel error is disclosed.Additionally,an OMM efficiency optimization model for complex curved surfaces is developed.This model is solved to produce the optimal efficiency angle combinations for each to-be-measured point.Within each angle combination,the effects of positioning errors on measurement results are addressed by coordinate system offset and measurement result compensation method.Finally,the experiments on an impeller are used to demonstrate the practical utility of the proposed method.展开更多
This paper examines the transport analysis,including both heat transfer and mass transfer,in hybrid nanofluid flow containing gyrotactic microorganisms towards a curved oscillatory surface.The influence of magnetic fi...This paper examines the transport analysis,including both heat transfer and mass transfer,in hybrid nanofluid flow containing gyrotactic microorganisms towards a curved oscillatory surface.The influence of magnetic fields is also inspected in terms of their physical characteristics.To depict the phenomena of transport,modified versions of both Fick's and Fourier's laws are used.Additionally,the characteristics of both heterogeneous and homogeneous chemical reactions are also incorporated.Utilizing a curvilinear coordinate system,the flow problem is formulated as partial differential equations(PDEs)for momentum,concentration,microorganism field,and energy.An analytical solution to the obtained flow equations is achieved utilizing the homotopy analysis method(HAM).The effects of significant flow parameters on the pressure and microorganism fields,velocity,oscillation velocity,concentration,and temperature distributions are shown via graphs.Furthermore,the variations in skin friction,mass transfer rate,heat transfer rate,and local motile number due to different involved parameters are presented in tables and are analyzed in detail.Graphical results indicate that the curves of velocity and temperature fields are enhanced as the values of the solid volume fraction variables increase.It is also verified that the concentration rate field decreases as the values of the homogeneous reaction strength parameter and the radius of curvature parameter increase,and it increases with the Schmidt number and the heterogeneous reaction strength parameter.Tabular outcomes show a favorable response of the motile number to advanced values of the Peclet number,the Schmidt number,the microorganism difference parameter,and the bio-convective Lewis number.展开更多
Curved geostructures,such as tunnels,are commonly encountered in geotechnical engineering and are critical to maintaining structural stability.Ensuring their proper performance through field monitoring during their se...Curved geostructures,such as tunnels,are commonly encountered in geotechnical engineering and are critical to maintaining structural stability.Ensuring their proper performance through field monitoring during their service life is essential for the overall functionality of geotechnical infrastructure.Distributed Brillouin sensing(DBS)is increasingly applied in geotechnical projects due to its ability to acquire spatially continuous strain and temperature distributions over distances of up to 150 km using a single optical fibre.However,limited by the complex operations of distributed optic fibre sensing(DFOS)sensors in curved structures,previous reports about exploiting DBS in geotechnical structural health monitoring(SHM)have mostly been focused on flat surfaces.The lack of suitable DFOS installation methods matched to the spatial characteristics of continuous monitoring is one of the major factors that hinder the further application of this technique in curved structures.This review paper starts with a brief introduction of the fundamental working principle of DBS and the inherent limitations of DBS being used on monitoring curved surfaces.Subsequently,the state-of-the-art installation methods of optical fibres in curved structures are reviewed and compared to address the most suitable scenario of each method and their advantages and disadvantages.The installation challenges of optical fibres that can highly affect measurement accuracy are also discussed in the paper.展开更多
Prior to 2012,the integration of designed vertical or horizontal curves into microtunnel alignments was unheard of in Ontario.Straight and relatively short microtunnels,less than 200m long,were the local accepted indu...Prior to 2012,the integration of designed vertical or horizontal curves into microtunnel alignments was unheard of in Ontario.Straight and relatively short microtunnels,less than 200m long,were the local accepted industry standard.Following the release of a large number of infrastructure projects in the suburban Greater Toronto Area(GTA),clients and design consultants encouraged contractors to present value engineered alternatives to proposed project alignments and construction methods.Such an initiative has allowed contractors to develop cost effective solutions,which harnessed the application of state-of-the-art microtunnelling methods and equipment.As a result,several recent projects now feature pre-designed curved microtunnels as part of the tender documents.This paper discusses,in technical detail,three recent projects,whereby,long distance curved microtunnels were successfully constructed.Each of the projects had tunnel drives exceeding 300m in length,ranging in diameter from 1200mm ID to 1500mm ID,incorporating the use of Vertical,Horizontal,and Spatial Curves.Critical parameters such as pre-project planning and engineering are highlighted,while the importance of post-tunnelling assessments is also discussed.展开更多
This work presents a piezoelectric vibration energy harvester(PVEH)featuring a pre-shaped curved beam with clamped boundaries to investigate its energy harvesting mechanism based on the intrinsic snap-through behavior...This work presents a piezoelectric vibration energy harvester(PVEH)featuring a pre-shaped curved beam with clamped boundaries to investigate its energy harvesting mechanism based on the intrinsic snap-through behavior.Since the ability of the beam to exhibit meta-stable and bi-stable states strongly depends on its geometric parameters,the potential energies of models with varying thicknesses and initial apex heights are analyzed,followed by the derivations of electromechanical coupled equations for both meta-stable and bi-stable systems.The effects of the geometric parameters of the curved beam on the nonlinear dynamic behaviors and energy harvesting efficiencies under different external excitations are examined.Series of experiments are tested to validate the theoretical analyses.The research findings show that the separation between the potential wells in the bi-stable beam is mainly governed by the thickness and initial apex height,while the potential barrier height is affected by both the geometric and material properties.The optimal energy harvesting efficiencies in the transition analyses of meta-stable and bi-stable states are achieved by tuning specific geometric parameters.Design guidelines are provided to maximize the bandwidth and efficiency for energy harvesting applications.展开更多
This paper investigates the free vibration and transient response of interconnected structures including double curved beams and intermediate straight beams,which are all constructed from functionally graded porous(FG...This paper investigates the free vibration and transient response of interconnected structures including double curved beams and intermediate straight beams,which are all constructed from functionally graded porous(FGP)materials.The strain potential and kinetic energies of each beam along with the work done by the external force are calculated.Additionally,a higher-order beam element is introduced to derive stiffness and mass matrices,along with the force vector.The curved and straight beams are discretized,and their assembled stiffness,mass matrices,and force vectors,are obtained.Continuity conditions at the joints are used to derive the total matrices of the entire structure.Subsequently,the natural frequencies and transient response of the system are determined.The accuracy of the mathematical model and the self-developed computer program is validated through the comparison of the obtained results with those of the existing literature and commercial software ANSYS,demonstrating excellent agreement.Furthermore,a comprehensive study is conducted to investigate the effects of various parameters on the free vibration and transient response of the considered structure.展开更多
Defect inspection of specular curved surface is a challenging job. Taking steel balls for example, a new method based on reflected pattern integrity recognition is put forward. The specular steel ball surfac...Defect inspection of specular curved surface is a challenging job. Taking steel balls for example, a new method based on reflected pattern integrity recognition is put forward. The specular steel ball surface will totally reflect the patterns when it is placed inside a dome-shaped light source, whose inner wall is modified by patterns with certain regular. Distortion or intermittence of reflected pattern will occur at the defective part, which indicates the pattern has lost its integrity. Based on the integrity analysis of reflected pattern images？ surface defects can be revealed. In this paper, a set of concentric circles are used as the pattern and an image processing algorithm is customized to extract the surface defects. Results show that the proposed method is effective for the specular curved surface defect inspection展开更多
The unsteady 3D flow fields in a single-stage transonic compressor under designed conditions are simulated numerically to investigate the effects of the curved rotors on the stage performance and the aerodynamic inter...The unsteady 3D flow fields in a single-stage transonic compressor under designed conditions are simulated numerically to investigate the effects of the curved rotors on the stage performance and the aerodynamic interaction between the blade rows. The results show that, compared to the compressor with unurved rotors, the compressor under scrutiny acquires remarkable increases in efficiency with significantly reduced amplitudes of the time-dependent fluctuation. The amplitude of the pressure fluctuation around the stator leading edge decreases at both endwalls, but increases at the mid-span in the curved rotors. The pressure fluctuation near the stator leading edge, therefore, becomes more uniform in the radial direction of this compressor. Except for the leading edge area, the pressure fluctuatinn amplitude declines remarkably in the tip region of stator surface downstream of the curved rotor, but hardly changes in the middle and at the hub.展开更多
For the purpose of carrying out the large deformation finite element analysis of spatial curved beams,the total Lagrangian（TL）and the updated Lagrangian（UL）incremental formulations for arbitrary spatial curved bea...For the purpose of carrying out the large deformation finite element analysis of spatial curved beams,the total Lagrangian（TL）and the updated Lagrangian（UL）incremental formulations for arbitrary spatial curved beam elements are established with displacement vector interpolation,which is improved from component interpolation of the straight beam displacement.A strategy of replacing the actual curve with the isoparametric curve is used to expand the applications of the UL formulation.The examples indicate that the process of establishing the curved beam element is correct,and the accuracy with the curved beam element is obviously higher than that with the straight beam element.Generally,the same level of computational accuracy can be achieved with 1/5 as many curved beam elements as otherwise with straight beam elements.展开更多
The analysis of plane strain elastic-plastic bending of a linear strain hardening curved beam with a narrow rectangular cross section subjected to couples at its end is conducted based on a unified yield criterion. Th...The analysis of plane strain elastic-plastic bending of a linear strain hardening curved beam with a narrow rectangular cross section subjected to couples at its end is conducted based on a unified yield criterion. The solutions for the mechanical properties of plane strain bending are derived, which are adapted for various kinds of non-strength differential materials and can be degenerated to those based on the Tresca, von Mises, and twin-shear yield criteria. The dependences of the two critical bending moments, the radii of the interfaces between the elastic and plastic regions and the radial displacements of the points at the symmetrical plane on different yield criteria and Poisson’s ratios are discussed. The results show that the influences of different yield criteria and Poisson’s ratio on the two critical bending moments, the radii of the interfaces between the elastic and plastic regions and the radial displacements of the points at the symmetrical plane of the curved beam are significant. Once the value of bis obtained by experiments, the yield criterion and the corresponding solution for the materials of interest are then determined.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.52078334)the National Key Research and Development Program of China(Grant No.2017YFC0805402)the Tianjin Research Innovation Project for Postgraduate Students(Grant No.2021YJSB141).
文摘The deformation caused by tunnel excavation is quite important for safety,especially when it is adjacent to the existing tunnel.Nevertheless,the investigation of deformation characteristics in overlapped curved shield tunneling remains inadequate.The analytical solution for calculating the deformation of the ground and existing tunnel induced by overlapped curved shield tunneling is derived by the Mirror theory,Mindlin solution and Euler-Bernoulli-Pasternak model,subsequently validated through both finite element simulation and field monitoring.It is determined that the overcutting plays a crucial role in the ground settlement resulting from curved shield tunneling compared to straight shield tunneling.The longitudinal settlement distribution can be categorized into five areas,with the area near the tunnel surface experiencing the most dramatic settlement changes.The deformation of the existing tunnel varies most significantly with turning radius compared to tunnel clearance and grouting pressure,especially when the turning radius is less than 30 times the tunnel diameter.The tunnel crown exhibits larger displacement than the tunnel bottom,resulting in a distinctive‘vertical egg'shape.Furthermore,an optimized overcutting mode is proposed,involving precise control of the extension speed and angular velocity of the overcutting cutter,which effectively mitigates ground deformation,ensuring the protection of the existing tunnel during the construction.
基金supported by Scientific Research Projects Department of Istanbul Technical University.Project Number:MGA-2018-41546.Grant receiver:E.T.
文摘Due to their superior properties, the interest in nanostructures is increasing today in engineering. This study presents a new two-noded curved finite element for analyzing the in-plane static behaviors of curved nanobeams. Opposite to traditional curved finite elements developed by using approximate interpolation functions, the proposed curved finite element is developed by using exact analytical solutions. Although this approach was first introduced for analyzing the mechanical behaviors of macro-scale curved beams by adopting the local theory of elasticity, the exact analytical expressions used in this study were obtained from the solutions of governing equations that were expressed via the differential form of the nonlocal theory of elasticity. Therefore, the effects of shear strain and axial extension included in the analytical formulation are also inherited by the curved finite element developed here. The rigidity matrix and the consistent force vector are developed for a circular finite element. To demonstrate the applicability of the method, static analyses of various curved nanobeams subjected to different boundary conditions and loading scenarios are performed, and the obtained results are compared with the exact analytical ones. The presented study provides an accurate and low computational cost method for researchers to investigate the in-plane static behavior of curved nanobeams.
基金Project(JQ2022E004)supported by the Natural Science Foundation of Heilongjiang Province,China。
文摘Traditional manufacturing processes for lightweight curved profiles are often associated with lengthy procedures,high costs,low efficiency,and high energy consumption.In order to solve this problem,a new staggered extrusion(SE)process was used to form the curved profile of AZ31 magnesium alloy in this paper.The study investigates the mapping relationship between the curvature,microstructure,and mechanical properties of the formed profiles by using different eccentricities of the die.Scanning electron microscopy(SEM)and electron backscatter diffraction techniques are employed to examine the effects of different eccentricity values(e)on grain morphology,recrystallization mechanisms,texture,and Schmid factors of the products.The results demonstrate that the staggered extrusion method promotes the deep refinement of grain size in the extruded products,with an average grain size of only 15%of the original billet,reaching 12.28μm.The tensile strength and elongation of the curved profiles after extrusion under the eccentricity value of 10 mm,20 mm and 30 mm are significantly higher than those of the billet,with the tensile strength is increased to 250,270,235 MPa,and the engineering strain elongation increased to 10.5%,12.1%,15.9%.This indicates that staggered extrusion enables curvature control of the profiles while improving their strength.
基金supported by the National Natural Science Foundation of China(No.12272353)the Postdoctoral Research Grant in Henan Province of China(No.202003091)the Key Scientific Research Projects in Colleges and Universities of Henan Province of China(No.22A130008)。
文摘The fracture mechanics theory posits that cracks induce strain energy concentration near their tips in structural components,generating localized flexibility that impedes crack propagation.Theoretically,cracks are represented as dimensionless,massless spring models,effectively capturing crack characteristics and cross-sectional properties at the crack location.Leveraging this spring-based representation,this study establishes an open-crack model for a one-dimensional(1D)piezoelectric semiconductor(PSC)curved beam under dynamic loading.This model enables the investigation of vibration characteristics in cracked structures.The analytical solutions for the electromechanical fields of the beam are derived using the differential operator method,and the natural frequencies together with the corresponding generalized mode shapes of the beam are determined analytically.Furthermore,the effects of the crack parameters on the natural vibration characteristics of the PSC curved beam are analyzed.
基金financial support from the Ministry of Education,Culture,Sports,Science and Technology (MEXT),Japan
文摘The effect of seismic directionality is crucial for curved bridges,a subject generally overlooked in seismic vulnerability analysis.This paper focuses on seismic fragility development as a function of seismic incidence directions for a geometrically curved bridge.A series of non-linear time history analyses were carried out for a representative finite element model of the bridge by considering actual ground motions.For reliable seismic demand models,a total of eleven intensity measures(IM)were analyzed based on optimality metrics.To quantify the sensitivity of fragility functions to input incidence directions,fragility surfaces were developed throughout the horizontal plane by considering spectral acceleration at one second(Sa_(1.0))as the optimal IM.Results show that the optimal IM ranking is insignificantly influenced by seismic directionality.However,seismic orientation influences fragility,which intensifies in higher damage states,particularly for piers.For a bridge system,the differences in median demand corresponding to the least and most vulnerable direction for slight,moderate,extensive,and collapse states are about 9.0%,7.31%,10.32%,and 11.60%,respectively.These results imply that while evaluating the vulnerability of curved bridges,the optimality of IM in demand estimation and the impact of seismic directionality should not be disregarded.
基金supported by the National Natural Science Foundation of China(grant nos.12072212,12372185 and 12102280)the Sichuan Province Science and Technology Project(grant nos.2023NSFSC1918,and 2022JDJQ0011).
文摘Magnesium alloys with long-period stacking ordered(LPSO)structures are known for their impressive static mechanical strength,but the consistent occurrence of slip-cracking along the LPSO lamellae,which do not effectively impede the movement of basal dislocations,has prompted concerns about their very high cycle fatigue(VHCF)performance.In this study,an extruded Mg-Gd-Zn-Zr alloy was developed,showcasing exceptional VHCF resistance due to its bimodal structure comprisingfine grains and coarse grains consisting of curved LPSO lamellae.The investigation on the crack initiation mechanism revealed that slip-induced cracking predominantly occurs infine-grained regions rather than in the interior of coarse grains.The extrusion process aligns the basal planes of most coarse grains parallel to the axial direction,and the presence of curved LPSO lamellae acts as barriers to the movement of basal dislocations,thereby effectively increasing the threshold for slip-cracking along the basal plane.Consequently,fatigue damage manifests in the form of slip bands and micro-cracks within the interior offine grains,ultimately resulting in fatigue crack initiation,propagation andfinal fracture.
文摘Curved beams with complex geometries are vital in numerous engineering applications,where precise vibration analysis is crucial for ensuring safe and effective designs.Traditional finite element methods(FEMs) often struggle to accurately represent the dynamic characteristics of these structures due to the limitations in their shape function approximations.To overcome this challenge,the current study introduces an innovative finite element(FE)-based technique for the undamped vibrational analysis of curved beams with arbitrary curvature,employing explicitly derived interpolation functions.Initially,the exact interpolation functions are developed for circular are elements with the force method.These functions facilitate the creation of a highly accurate stiffness matrix,which is validated against the benchmark examples.To accommodate arbitrary curvature,a systematic transformation technique is established to approximate the intricate curves with a series of circular arcs.The numerical findings indicate that increasing the number of arc segments enhances accuracy,approaching the exact solutions.The analysis of free vibrations is conducted for both circular and non-circular beams.Mass matrices are derived using two methods:lumped mass and consistent mass,where the latter is based on the interpolation functions.The effectiveness of the proposed method is confirmed through the comparisons with the existing literature,demonstrating strong agreement.Finally,several practical cases involving beams with diverse curvature profiles are analyzed.Both natural frequencies and mode shapes are determined,providing significant insights into the dynamic behavior of these structures.This research offers a dependable and efficient analytical framework for the vibrational analysis of complex curved beams,with promising implications for structural and mechanical engineering.
文摘Arterial stenosis is a critical condition with increasing prevalence among pediatric patients and young adults,making its investigation highly significant.Despite extensive studies on blood flow dynamics,limited research addresses the combined effects of nanoparticles and arterial curvature on unsteady pulsatile flow through multiple stenoses.This study aims to analyze the influence of nanoparticles on blood flow characteristics in realistic curved arteries with mild to severe overlapped constrictions.Using curvilinear coordinates,the thermal energy and momentum equations for nanoparticle-laden blood were derived,and numerical results were obtained through an explicit finite difference method.Key findings reveal that nanoparticle injections reduce blood temperature intensity,while arterial curvature strongly affects flow symmetry.Moreover,temperature,axial velocity,wall shear stress,and volumetric flow rate decrease significantly in severe stenosis compared to mild and moderate cases.These results provide new insights into nanoparticle-assisted blood flow under complex stenotic conditions and may contribute to improved diagnostic and therapeutic strategies for cardiovascular diseases.
基金Ho Chi Minh City University of Technology (HCMUT), VNU-HCM for supporting this study
文摘In this study,an improved integrated radial basis function with nonuniform shape parameter is introduced.The proposed shape parameter varies in each support domain and is defined byθ=1/d_(max),where d_(max)is the maximum distance of any pair of nodes in the support domain.The proposed method is verified and shows good performance.The results are stable and accurate with any number of nodes and an arbitrary nodal distribution.Notably,the support domain should be large enough to obtain accurate results.This method is then applied for transient analysis of curved shell structures made from functionally graded materials with complex geometries.Through several numerical examples,the accuracy of the proposed approach is demonstrated and discussed.Additionally,the influence of various factors on the dynamic behavior of the structures,including the power-law index,different materials,loading conditions,and geometrical parameters of the structures,was investigated.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIT)(No.NRF-2022R1A4A1028747 and RS-2024-00344151).
文摘Recent advances in bone regeneration have introduced the concept of four-dimensional(4D)scaffolds that can undergo morphological and functional changes in response to external stimuli.While several studies have proposed patient-specific designs for defect sites,they often fail to adequately distinguish the advantages of 4D scaffolds over conventional 3D counterparts.This study aimed to investigate the potential benefits of 4D scaffolds in clinically challenging scenarios involving curved defects,where fixation is difficult.We proposed the use of Shape-Memory Polymers(SMPs)as a solution to address critical issues in personalized scaffold fabrication,including dimensional accuracy,measurement error,and manufacturing imprecision.Experimental results demonstrated that the Curved-Layer Fused Deposition Modeling(CLFDM)scaffold,which offers superior conformability to curved defects,achieved significantly higher interfacial contact with the defect area compared to traditional Fused Deposition Modeling(FDM)scaffolds.Specifically,the CLFDM scaffold facilitated bone regeneration of 25.59±4.72 mm^(3),which is more than twice the 9.37±1.36 mm^(3)observed with the 3D FDM scaffold.Furthermore,the 4D CLFDM scaffold achieved 75.38±11.65 mm^(3)of new bone formation after four weeks,approximately three times greater than that of the 3D CLFDM scaffold,regardless of surface micro-roughness.These results underscore that improved geometrical conformity between the scaffold and the defect site enhances cellular infiltration and contributes to more effective bone regeneration.The findings also highlight the promise of 4D scaffolds as a compelling strategy to overcome geometric and dimensional mismatches in the design of patient-specific scaffolds.
基金Projects(51775445,52175435)supported by the National Natural Science Foundation of ChinaProject(CX2023051)supported by the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University,China。
文摘On-machine measurement(OMM)stands out as a pivotal technology in complex curved surface adaptive machining.However,the complex structure inherent in workpieces poses a significant challenge as the stylus orientation frequently shifts during the measurement process.Consequently,a substantial amount of time is allocated to calibrating pre-travel error and probe movement.Furthermore,the frequent movement of machine tools also increases the influence of machine errors.To enhance both accuracy and efficiency,an optimization strategy for the OMM process is proposed.Based on the kinematic chain of the machine tools,the relationship between the angle combination of rotary axes,the stylus orientation,and the calibration position of pre-travel error is disclosed.Additionally,an OMM efficiency optimization model for complex curved surfaces is developed.This model is solved to produce the optimal efficiency angle combinations for each to-be-measured point.Within each angle combination,the effects of positioning errors on measurement results are addressed by coordinate system offset and measurement result compensation method.Finally,the experiments on an impeller are used to demonstrate the practical utility of the proposed method.
文摘This paper examines the transport analysis,including both heat transfer and mass transfer,in hybrid nanofluid flow containing gyrotactic microorganisms towards a curved oscillatory surface.The influence of magnetic fields is also inspected in terms of their physical characteristics.To depict the phenomena of transport,modified versions of both Fick's and Fourier's laws are used.Additionally,the characteristics of both heterogeneous and homogeneous chemical reactions are also incorporated.Utilizing a curvilinear coordinate system,the flow problem is formulated as partial differential equations(PDEs)for momentum,concentration,microorganism field,and energy.An analytical solution to the obtained flow equations is achieved utilizing the homotopy analysis method(HAM).The effects of significant flow parameters on the pressure and microorganism fields,velocity,oscillation velocity,concentration,and temperature distributions are shown via graphs.Furthermore,the variations in skin friction,mass transfer rate,heat transfer rate,and local motile number due to different involved parameters are presented in tables and are analyzed in detail.Graphical results indicate that the curves of velocity and temperature fields are enhanced as the values of the solid volume fraction variables increase.It is also verified that the concentration rate field decreases as the values of the homogeneous reaction strength parameter and the radius of curvature parameter increase,and it increases with the Schmidt number and the heterogeneous reaction strength parameter.Tabular outcomes show a favorable response of the motile number to advanced values of the Peclet number,the Schmidt number,the microorganism difference parameter,and the bio-convective Lewis number.
基金support provided by Science Foundation Ireland Frontiers for the Future Programme,21/FFP-P/10090.
文摘Curved geostructures,such as tunnels,are commonly encountered in geotechnical engineering and are critical to maintaining structural stability.Ensuring their proper performance through field monitoring during their service life is essential for the overall functionality of geotechnical infrastructure.Distributed Brillouin sensing(DBS)is increasingly applied in geotechnical projects due to its ability to acquire spatially continuous strain and temperature distributions over distances of up to 150 km using a single optical fibre.However,limited by the complex operations of distributed optic fibre sensing(DFOS)sensors in curved structures,previous reports about exploiting DBS in geotechnical structural health monitoring(SHM)have mostly been focused on flat surfaces.The lack of suitable DFOS installation methods matched to the spatial characteristics of continuous monitoring is one of the major factors that hinder the further application of this technique in curved structures.This review paper starts with a brief introduction of the fundamental working principle of DBS and the inherent limitations of DBS being used on monitoring curved surfaces.Subsequently,the state-of-the-art installation methods of optical fibres in curved structures are reviewed and compared to address the most suitable scenario of each method and their advantages and disadvantages.The installation challenges of optical fibres that can highly affect measurement accuracy are also discussed in the paper.
文摘Prior to 2012,the integration of designed vertical or horizontal curves into microtunnel alignments was unheard of in Ontario.Straight and relatively short microtunnels,less than 200m long,were the local accepted industry standard.Following the release of a large number of infrastructure projects in the suburban Greater Toronto Area(GTA),clients and design consultants encouraged contractors to present value engineered alternatives to proposed project alignments and construction methods.Such an initiative has allowed contractors to develop cost effective solutions,which harnessed the application of state-of-the-art microtunnelling methods and equipment.As a result,several recent projects now feature pre-designed curved microtunnels as part of the tender documents.This paper discusses,in technical detail,three recent projects,whereby,long distance curved microtunnels were successfully constructed.Each of the projects had tunnel drives exceeding 300m in length,ranging in diameter from 1200mm ID to 1500mm ID,incorporating the use of Vertical,Horizontal,and Spatial Curves.Critical parameters such as pre-project planning and engineering are highlighted,while the importance of post-tunnelling assessments is also discussed.
基金supported by the National Natural Science Foundation of China(Nos.12172012,12372024,and 11802005)。
文摘This work presents a piezoelectric vibration energy harvester(PVEH)featuring a pre-shaped curved beam with clamped boundaries to investigate its energy harvesting mechanism based on the intrinsic snap-through behavior.Since the ability of the beam to exhibit meta-stable and bi-stable states strongly depends on its geometric parameters,the potential energies of models with varying thicknesses and initial apex heights are analyzed,followed by the derivations of electromechanical coupled equations for both meta-stable and bi-stable systems.The effects of the geometric parameters of the curved beam on the nonlinear dynamic behaviors and energy harvesting efficiencies under different external excitations are examined.Series of experiments are tested to validate the theoretical analyses.The research findings show that the separation between the potential wells in the bi-stable beam is mainly governed by the thickness and initial apex height,while the potential barrier height is affected by both the geometric and material properties.The optimal energy harvesting efficiencies in the transition analyses of meta-stable and bi-stable states are achieved by tuning specific geometric parameters.Design guidelines are provided to maximize the bandwidth and efficiency for energy harvesting applications.
文摘This paper investigates the free vibration and transient response of interconnected structures including double curved beams and intermediate straight beams,which are all constructed from functionally graded porous(FGP)materials.The strain potential and kinetic energies of each beam along with the work done by the external force are calculated.Additionally,a higher-order beam element is introduced to derive stiffness and mass matrices,along with the force vector.The curved and straight beams are discretized,and their assembled stiffness,mass matrices,and force vectors,are obtained.Continuity conditions at the joints are used to derive the total matrices of the entire structure.Subsequently,the natural frequencies and transient response of the system are determined.The accuracy of the mathematical model and the self-developed computer program is validated through the comparison of the obtained results with those of the existing literature and commercial software ANSYS,demonstrating excellent agreement.Furthermore,a comprehensive study is conducted to investigate the effects of various parameters on the free vibration and transient response of the considered structure.
基金Tianjin Research Program of Application Foundation and Advanced Technology(No.14JCYBJC18600,No.14JCZDJC39700)National Key Scientific Instrument and Equipment Development Project(No.2013YQ17053903)
文摘Defect inspection of specular curved surface is a challenging job. Taking steel balls for example, a new method based on reflected pattern integrity recognition is put forward. The specular steel ball surface will totally reflect the patterns when it is placed inside a dome-shaped light source, whose inner wall is modified by patterns with certain regular. Distortion or intermittence of reflected pattern will occur at the defective part, which indicates the pattern has lost its integrity. Based on the integrity analysis of reflected pattern images？ surface defects can be revealed. In this paper, a set of concentric circles are used as the pattern and an image processing algorithm is customized to extract the surface defects. Results show that the proposed method is effective for the specular curved surface defect inspection
基金National Natural Science Foundation of China (506460210) Chinese Specialized Research Fund for the Doctoral Program of Higher Education (20060213007)Development Program for Outstanding Young Teachers in Harbin Institute of Technology (HITQNJS.2006.046)
文摘The unsteady 3D flow fields in a single-stage transonic compressor under designed conditions are simulated numerically to investigate the effects of the curved rotors on the stage performance and the aerodynamic interaction between the blade rows. The results show that, compared to the compressor with unurved rotors, the compressor under scrutiny acquires remarkable increases in efficiency with significantly reduced amplitudes of the time-dependent fluctuation. The amplitude of the pressure fluctuation around the stator leading edge decreases at both endwalls, but increases at the mid-span in the curved rotors. The pressure fluctuation near the stator leading edge, therefore, becomes more uniform in the radial direction of this compressor. Except for the leading edge area, the pressure fluctuatinn amplitude declines remarkably in the tip region of stator surface downstream of the curved rotor, but hardly changes in the middle and at the hub.
基金The Major Research Plan of the National Natural Science Foundation of China(No.90715021)
文摘For the purpose of carrying out the large deformation finite element analysis of spatial curved beams,the total Lagrangian（TL）and the updated Lagrangian（UL）incremental formulations for arbitrary spatial curved beam elements are established with displacement vector interpolation,which is improved from component interpolation of the straight beam displacement.A strategy of replacing the actual curve with the isoparametric curve is used to expand the applications of the UL formulation.The examples indicate that the process of establishing the curved beam element is correct,and the accuracy with the curved beam element is obviously higher than that with the straight beam element.Generally,the same level of computational accuracy can be achieved with 1/5 as many curved beam elements as otherwise with straight beam elements.
基金The Project of the Ministry of Housing and Urban-Rural Development(No.2014-K4-010)
文摘The analysis of plane strain elastic-plastic bending of a linear strain hardening curved beam with a narrow rectangular cross section subjected to couples at its end is conducted based on a unified yield criterion. The solutions for the mechanical properties of plane strain bending are derived, which are adapted for various kinds of non-strength differential materials and can be degenerated to those based on the Tresca, von Mises, and twin-shear yield criteria. The dependences of the two critical bending moments, the radii of the interfaces between the elastic and plastic regions and the radial displacements of the points at the symmetrical plane on different yield criteria and Poisson’s ratios are discussed. The results show that the influences of different yield criteria and Poisson’s ratio on the two critical bending moments, the radii of the interfaces between the elastic and plastic regions and the radial displacements of the points at the symmetrical plane of the curved beam are significant. Once the value of bis obtained by experiments, the yield criterion and the corresponding solution for the materials of interest are then determined.
