The buckling behavior of stiffened panels is significantly influenced by material and geometric defects,making it a critical factor in ensuring structural integrity and safety.These panels are widely used in mechanica...The buckling behavior of stiffened panels is significantly influenced by material and geometric defects,making it a critical factor in ensuring structural integrity and safety.These panels are widely used in mechanical,aerospace,marine,and civil engineering applications due to their ability to enhance bending stiffness with minimal additional weight.Under high loads or stress concentrations,localized structural failures can initiate global buckling in stiffened panels.This study investigates how such defects affect the critical buckling load,stiffness,and thickness of stiffened panels.Two finite element analyses were conducted:a linear analysis to identify the initial buckling mode and a nonlinear analysis using the Riks algorithm in Abaqus CAE,incorporating localized imperfections.The simulations show that material and geometric defects can reduce buckling resistance depending on their severity.展开更多
The efficient recovery of silver(Ag)from retired photovoltaic(PV)panels is crucial for resource sustainability and envi-ronmental protection.This study developed an environmentally friendly leaching method using ammon...The efficient recovery of silver(Ag)from retired photovoltaic(PV)panels is crucial for resource sustainability and envi-ronmental protection.This study developed an environmentally friendly leaching method using ammonia(NH_(3)·H_(2)O)and hydrogen peroxide(H_(2)O_(2)),achieving the selective dissolution of Ag from retired crystalline silicon solar panels.Meanwhile,nonprecious metals such as aluminum(Al)and lead(Pb),which are commonly found in PV cells,were barely dissolved,dem-onstrating the excellent selectivity of this method for Ag.Light irradiation significantly improved the dissolution efficiency of Ag and reduced the amount of the reagent used.Ag dissolution occurred owing to a dual-pathway synergistic effect,which stemmed from the direct oxidation of Ag by H_(2)O_(2).The strongly oxidizing hydroxyl radicals generated by photocatalysis accelerated the oxidation and dissolution of Ag.In addition,NH 3·H_(2)O effectively promoted the dissolution and stabilization of oxidation products by forming soluble Ag–NH3·H2O complexes([Ag(NH3)2]+).This article reports an efficient,selective,and environmentally friendly strategy of Ag recovery and elucidates the radical-mediated dissolution mechanism under light-driven conditions,offering a feasible way for sustainably recovering valuable metals from retired PV panels.展开更多
In recent years,there has been a growing global demand for carbon neutrality and energy efficiency,which are expected to become long-term trends.In the field of architecture,an effective approach to achieve this is to...In recent years,there has been a growing global demand for carbon neutrality and energy efficiency,which are expected to become long-term trends.In the field of architecture,an effective approach to achieve this is to reduce heat loss in buildings.Vacuum insulation panels(VIPs),a type of high-performance insulation material,have been increasingly utilised in the construction industry and have played an increa-singly important role as their performance and manufacturing processes continue to improve.This paper provides a review of the factors affecting the thermal conductivity of VIPs and presents a detailed overview of the research progress on core materials,barrier films,and getters.The current research status of VIPs is summarised,including their thermal conductivity,service life,and thermal bridging effects,as well as their applications in the field of architecture.This review aims to provide a comprehensive understanding for relevant practitioners on the factors influencing the thermal conductivity of VIPs,and based on which,measures can be taken to produce VIPs with lower thermal conductivity and longer service life.展开更多
Wind tunnel experiment and CFD(computational fluid dynamics)simulation with LES(large eddy simulation)have been conducted to investigate the characteristics of peak wind force coefficients of porous panels mounted on ...Wind tunnel experiment and CFD(computational fluid dynamics)simulation with LES(large eddy simulation)have been conducted to investigate the characteristics of peak wind force coefficients of porous panels mounted on the roofs of high-rise buildings.First,aerodynamic modelling of porous panels was discussed.The relation between pressure loss coefficient and porosity was obtained.Then,a wind tunnel experiment was conducted to measure the wind forces(net wind pressures)acting on solid and porous panels mounted on the roof of a high-rise building.Because it was difficult to measure the pressures on both sides of thin,porous panel at the same location simultaneously,we proposed to use the roof edge pressures near the panel for the panel’s inside-surface pressures.This experimental method was validated by a CFD simulation reproducing the wind tunnel experiment.The characteristics of peak wind force coefficients of porous panels mounted on the roofs of high-rise buildings were made clear.Finally,positive and negative peak wind force coefficients for designing the rooftop porous panels were proposed.展开更多
Due to the continuous increase in global energy demand,photovoltaic solar energy generation and associated maintenance requirements have significantly expanded.One critical maintenance challenge in photovoltaic instal...Due to the continuous increase in global energy demand,photovoltaic solar energy generation and associated maintenance requirements have significantly expanded.One critical maintenance challenge in photovoltaic installations is detecting hot spots,localized overheating defects in solar cells that drastically reduce efficiency and can lead to permanent damage.Traditional methods for detecting these defects rely on manual inspections using thermal imaging,which are costly,labor-intensive,and impractical for large-scale installations.This research introduces an automated hybrid system based on two specialized convolutional neural networks deployed in a cascaded architecture.The first convolutional neural network efficiently detects and isolates individual solar panels from high-resolution aerial thermal images captured by drones.Subsequently,a second,more advanced convolutional neural network accurately classifies each isolated panel as either defective or healthy,effectively distinguishing genuine thermal anomalies from false positives caused by reflections or glare.Experimental validation on a real-world dataset comprising thousands of thermal images yielded exceptional accuracy,significantly reducing inspection time,costs,and the likelihood of false defect detections.This proposed system enhances the reliability and efficiency of photovoltaic plant inspections,thus contributing to improved operational performance and economic viability.展开更多
A simulation method is proposed to predict the motion artifacts of plasma display panels （PDPs）. The method simulates the behavior of the human vision system when perceiving moving objects. The simulation is based o...A simulation method is proposed to predict the motion artifacts of plasma display panels （PDPs）. The method simulates the behavior of the human vision system when perceiving moving objects. The simulation is based on the measured temporal light properties of the display for each gray level and each phosphor. Both the effect of subfield arrangement and phosphor decay are involved. A novel algorithm is proposed to improve the calculation speed. The simulation model manages to predict the appearance of the motion image perceived by a human with a still image. The results are validated by a set of perceptual evaluation experiments. This rapid and accurate prediction of motion artifacts enables objective characterization of the PDP performance in this aspect.展开更多
Since bamboo has the advantages of straight grain, beautiful color, high strength and toughness, and excellent abrasion resistance, bamboo-based panels have been widely used in the fields of vehicle, construction, shi...Since bamboo has the advantages of straight grain, beautiful color, high strength and toughness, and excellent abrasion resistance, bamboo-based panels have been widely used in the fields of vehicle, construction, ship building, furniture, and decoration to partly take the place of wood, steel, plastic etc in China. This paper briefly described the basic component units, including strip, sliver, and particle, of bamboo-based panel and pointed out that to design the structure of bamboo-based panels should follow the principle of symmetric structure, surface forming method, and structuring principle of equalizing stress. According to the processing methods and formation of component units, the authors classified the bamboo-based panels in China into 13 types and presented the manufacturing technique and uses of the bamboo products, such as plybamboo, bamboo flooring, and bamboo-wood composite products in detail. In the last part of the paper, much information were offered on the output, market, and selling prospect of each type of bamboo-based panels.展开更多
In order to predict the buckling of stiffeners in the press bend forming of the integral panel,a method for solving the critical buckling load of the stiffeners in press bend forming process was proposed based on ener...In order to predict the buckling of stiffeners in the press bend forming of the integral panel,a method for solving the critical buckling load of the stiffeners in press bend forming process was proposed based on energy method,elastic-plastic mechanics and numerical analysis.Bend to buckle experiments were carried out on the designed press bend dies.It is found that the predicted results based on the proposed method agree well with the experimental results.With the proposed method,the buckling of the stiffeners in press bend forming of the aluminum alloy integral panels with high-stiffener can be predicted reasonably.展开更多
The paper starts with a brief overview to the necessity of sheet metal forming simulation and the complexity of automobile panel forming, then leads to finite element analysis (FEA) which is a powerful simulation too...The paper starts with a brief overview to the necessity of sheet metal forming simulation and the complexity of automobile panel forming, then leads to finite element analysis (FEA) which is a powerful simulation tool for analyzing complex three-dimensional sheet metal forming problems. The theory and features of the dynamic explicit finite element methods are introduced and the available various commercial finite element method codes used for sheet metal forming simulation in the world are discussed,and the civil and international status quo of automobile panel simulation as well. The front door outer panel of one certain new automobile is regarded as one example that the dynamic explicit FEM code Dynaform is used for the simulation of the front door outer panel forming process. Process defects such as ruptures are predicted. The improving methods can be given according to the simulation results. Foreground of sheet metal forming simulation is outlined.展开更多
Stiffened thermosetting composite panels were fabricated with co-curing processing.In the co-curing processing,the temperature distribution in the composite panels was nonuniform.An investigation into the threedimensi...Stiffened thermosetting composite panels were fabricated with co-curing processing.In the co-curing processing,the temperature distribution in the composite panels was nonuniform.An investigation into the threedimensional cure simulation of T-shape stiffened thermosetting composite panels was presented.Flexible tools and locating tools were considered in the cure simulation.Temperature distribution in the composites was predicted as a function of the autoclave temperature history.A nonlinear transient heat transfer finite element model was developed to simulate the curing process of stiffened thermosetting composite panels.And a simulation example was presented to demonstrate the use of the present finite element procedure for analyzing composite curing process.The glass/polyester structure was investigated to provide insight into the nonuniform cure process and the effect of flexible tools and locating tools on temperature distribution.Temperature gradient in the intersection between the skin and the flange was shown to be strongly dependent on the structure of the flexible tools and the thickness of the skin.展开更多
Experimental and analytical investigations on the residual strength of the stiffened LY12CZ aluminum alloy panels with widespread fatigue damage （WFD） are conducted. Nine stiffened LY12CZ aluminum alloy panels with ...Experimental and analytical investigations on the residual strength of the stiffened LY12CZ aluminum alloy panels with widespread fatigue damage （WFD） are conducted. Nine stiffened LY12CZ aluminum alloy panels with three different types of damage are tested for residual strength. Each specimen is pre-cracked at rivet holes by saw cuts and subjected to a monotonically increasing tensile load until failure is occurred and the failure load is recorded. The stress intensity factors at the tips of the lead crack and the adjacent WFD cracks of the stiffened aluminum alloy panels are calculated by compounding approach and finite element method （FEM） respectively. The residual strength of the stiffened panels with WFD is evaluated by the engineering method with plastic zone linkup criterion and the FEM with apparent fracture toughness criterion respectively. The predicted residual strength agrees well with the experiment results. It indicates that in engineering practice these methods can be used for residual strength evaluation with the acceptable accuracy. It can be seen from this research that WFD can significantly reduce the residual strength and the critical crack length of the stiffened panels with WFD. The effect of WFD crack length on residual strength is also studied.展开更多
An explicit topology optimization method for the stiffener layout of composite stiffened panels is proposed based on moving morphable components(MMCs).The skin and stiffeners are considered as panels with different be...An explicit topology optimization method for the stiffener layout of composite stiffened panels is proposed based on moving morphable components(MMCs).The skin and stiffeners are considered as panels with different bending stiffnesses,with the use of equivalent stiffness method.Then the location and geometric properties of composite stiffeners are determined by several MMCs to perform topology optimization,which can greatly simplify the finite element model.With the objective of maximizing structural stiffness,several typical cases with various loading and boundary conditions are selected as numerical examples to demonstrate the proposed method.The numerical examples illustrate that the proposed method can provide clear stiffener layout and explicit geometry information,which is not limited within the framework of parameter and size optimization.The mechanical properties of composite stiffened panels can be fully enhanced.展开更多
A finite element formulation is presented for the analysis of the aeroelastic effect on the aerothermoacoustic response of metallic panels in supersonic flow. The first-order shear deformation theory(FSDT) and the von...A finite element formulation is presented for the analysis of the aeroelastic effect on the aerothermoacoustic response of metallic panels in supersonic flow. The first-order shear deformation theory(FSDT) and the von Karman nonlinear strain-displacement relationships are employed to consider the geometric nonlinearity induced by large deflections. The piston theory and the Gaussian white noise are used to simulate the mean flow aerodynamics and the turbulence from the boundary layer. The thermal loading is assumed to be steady and uniformly distributed, and the material properties are assumed to be temperature independent. The governing equations of motion are firstly formulated in structural node degrees of freedom by using the principle of virtual work,and then transformed and reduced to a set of coupled nonlinear Duffing oscillators in modal coordinates. The dynamic response of a panel is obtained by the Runge-Kutta integration method. The results indicate that the increasing aeroelastic effect can lead the panel vibration from a random motion to a highly ordered motion in the fashion of diffused limit cycle oscillations(LCOs), and remarkably alter the stochastic bifurcation and the spectrum of the aerothermoacoustic response.On the other hand there exists a counterbalance mechanism between the external random loading and the aeroelastic effect, which mainly functions through the nonlinear frequency-amplitude response. It is surmised that the aeroelastic effect must be considered in sonic fatigue analysis for panel structures in supersonic flow.展开更多
To predict the attitude of satellite during the whole deployment process and evaluate the locking impact, a numerical flexible model of a certain satellite associated with four flexible honeycomb solar panels was esta...To predict the attitude of satellite during the whole deployment process and evaluate the locking impact, a numerical flexible model of a certain satellite associated with four flexible honeycomb solar panels was established. The flexible solar panel was modeled by the finite element analysis (FEA), and the motion equations were derived by Lagrangian formulation. The locking process was based on the method of Hertzian contact, which enables one to predict the locking impact on the satellite and the subsequent oscillation of solar panels. The results reveal that locking operation has great impact on the attitude of the satellite, and the angular acceleration of satellite reaches 22.03°/s2 at the locking moment; the flexible solar panels model is feasible to predict the accurate response of the satellite during deployment and the oscillation of solar panels; the instantly impulsive force occurred during locking process is about 1.5 kN and the changing time is nearly 0.32 s. It provides an effective approach to present the flexible solar panels' deployment process and evaluate the locking impact.展开更多
This paper proposes a model-based prognostics method that couples the Extended Kalman Filter(EKF) and a new developed linearization method. The proposed prognostics method is developed in the context of fatigue crack ...This paper proposes a model-based prognostics method that couples the Extended Kalman Filter(EKF) and a new developed linearization method. The proposed prognostics method is developed in the context of fatigue crack propagation in fuselage panels where the model parameters are unknown and the crack propagation is affected by different types of uncertainties. The coupled method is composed of two steps. The first step employs EKF to estimate the unknown model parameters and the current damage state. In the second step, the proposed efficient linearization method is applied to compute analytically the statistical distribution of the damage evolution path in some future time. A numerical case study is implemented to evaluate the performance of the proposed method. The results show that the coupled EKF-linearization method provides satisfactory results: the EKF algorithm well identifies the model parameters, and the linearization method gives comparable prediction results to Monte Carlo(MC) method while leading to very significant computational cost saving. The proposed prognostics method for fatigue crack growth can be used for developing predictive maintenance strategy for an aircraft fleet, in which case, the computational cost saving is significantly meaningful.展开更多
Sloshing phenomenon in a moving container is a complicated free surface flow problem. It has a wide range of engineering applications, especially in tanker ships and Liquefied Natural Gas (LNG) carriers. When the tank...Sloshing phenomenon in a moving container is a complicated free surface flow problem. It has a wide range of engineering applications, especially in tanker ships and Liquefied Natural Gas (LNG) carriers. When the tank in these vehicles is partially filled, it is essential to be able to evaluate the fluid dynamic loads on tank perimeter. Different geometric shapes such as rectangular, cylindrical, elliptical, spherical and circular conical have been suggested for ship storage tanks by previous researchers. In this paper a numerical model is developed based on incompressible and inviscid fluid motion for the liquid sloshing phenomenon. The coupled BEM-FEM is used to solve the governing equations and nonlinear free surface boundary conditions. The results are validated for rectangular container using data obtained for a horizontal periodic sway motion. Using the results of this model a new arrangement of trapezoidal shapes with quadratic sidewalls is suggested for tanker ship storage panels. The suggested geometric shape not only has a maximum surrounded tank volume to the constant available volume, but also reduces the sloshing effects more efficiently than the existing geometric shapes.展开更多
Considering increasing rate of Iran population and consumption of wood panels, the authors investigated the per capita consump- tion of wood panels during the years from 1997 to 2007. The exponential smoothing method ...Considering increasing rate of Iran population and consumption of wood panels, the authors investigated the per capita consump- tion of wood panels during the years from 1997 to 2007. The exponential smoothing method was used to obtain a per capita consumption panern of wood panels in lran for estimating demand of wood panels by the year of 2012. Results show that the consumption of particleboard, fiberboard, and medium density fiberboard in lran will increase by 33%, 72% and 107 %o, respectively, by the year of 2012; however, the consumption of plywood will increase only by 7% by 2012. The deficient amount of wood panels in Iran is estimated over 1400 000 m^3. The results of this study provide the technique reference for planners of wood panel industries in Iran in capital investment decisions.展开更多
An increase in methane,spontaneous fire and bumping hazards in Polish hard coal mines,observed in the last two decades,led to the need to elaborate the tools allowing proper selection of a range of preventive measures...An increase in methane,spontaneous fire and bumping hazards in Polish hard coal mines,observed in the last two decades,led to the need to elaborate the tools allowing proper selection of a range of preventive measures to fight them at the stage of designing coal extraction.Designing the production of a coal seams in the conditions of associated methane and spontaneous fires hazards in Polish hard coal mines requires elaboration of the design standards for coal panels in gassy coal seams.This paper presents the guidelines on how to design production in the conditions of associated methane and spontaneous fire hazards.Presented tools and methodology since the very first research were many times verified by daily mining operations in the conditions of associated methane and spontaneous fire hazards,which confirms their significant contribution to the development of safe and economical mining operations.展开更多
文摘The buckling behavior of stiffened panels is significantly influenced by material and geometric defects,making it a critical factor in ensuring structural integrity and safety.These panels are widely used in mechanical,aerospace,marine,and civil engineering applications due to their ability to enhance bending stiffness with minimal additional weight.Under high loads or stress concentrations,localized structural failures can initiate global buckling in stiffened panels.This study investigates how such defects affect the critical buckling load,stiffness,and thickness of stiffened panels.Two finite element analyses were conducted:a linear analysis to identify the initial buckling mode and a nonlinear analysis using the Riks algorithm in Abaqus CAE,incorporating localized imperfections.The simulations show that material and geometric defects can reduce buckling resistance depending on their severity.
基金supported by the National Science Foundation of China(Nos.22525606,22176128,22236005,22406131,22506126)the Innovation Program of Shanghai Municipal Education Commission(No.2023ZKZD50)+13 种基金Shanghai Leading Talent Program of Eastern Talent Plan(No.LJ2023002)Shanghai Government(Nos.22dz1205400,23520711100)Chinese Education Ministry Key Laboratory and International Joint Laboratory on Resource ChemistryShanghai Eastern Scholar ProgramThe authors also thank Fellowship of China National Postdoctoral Program for Innovative Talents(No.BX20240229)the China Postdoctoral Science(No.2024M762100)the Foundation the Shanghai Science and Technology Commission Project(No.24ZR1455700)Shanghai Post-doctoral Excellence Pro-gram(No.2024787)the Chenguang Program of Shanghai Education Development Foundation and Shanghai Municipal Education Com-mission(No.24CGA49)the“111 Innovation and Talent Recruitment Base on Photochemical and Energy Materials”(No.D18020)Yunnan University Collaborative Innovation Center(Qujing Green Photovoltaic Industry Collaborative Innovation Center)Technology Talent and Platform Plan Project of Yunnan Provincial Department of Science and Technology(No.202305AF150088)Shanghai Engineering Research Center of Green Energy Chemical Engineering(No.18DZ2254200)Shanghai Frontiers Science Center of Biomimetic Catalysis.
文摘The efficient recovery of silver(Ag)from retired photovoltaic(PV)panels is crucial for resource sustainability and envi-ronmental protection.This study developed an environmentally friendly leaching method using ammonia(NH_(3)·H_(2)O)and hydrogen peroxide(H_(2)O_(2)),achieving the selective dissolution of Ag from retired crystalline silicon solar panels.Meanwhile,nonprecious metals such as aluminum(Al)and lead(Pb),which are commonly found in PV cells,were barely dissolved,dem-onstrating the excellent selectivity of this method for Ag.Light irradiation significantly improved the dissolution efficiency of Ag and reduced the amount of the reagent used.Ag dissolution occurred owing to a dual-pathway synergistic effect,which stemmed from the direct oxidation of Ag by H_(2)O_(2).The strongly oxidizing hydroxyl radicals generated by photocatalysis accelerated the oxidation and dissolution of Ag.In addition,NH 3·H_(2)O effectively promoted the dissolution and stabilization of oxidation products by forming soluble Ag–NH3·H2O complexes([Ag(NH3)2]+).This article reports an efficient,selective,and environmentally friendly strategy of Ag recovery and elucidates the radical-mediated dissolution mechanism under light-driven conditions,offering a feasible way for sustainably recovering valuable metals from retired PV panels.
文摘In recent years,there has been a growing global demand for carbon neutrality and energy efficiency,which are expected to become long-term trends.In the field of architecture,an effective approach to achieve this is to reduce heat loss in buildings.Vacuum insulation panels(VIPs),a type of high-performance insulation material,have been increasingly utilised in the construction industry and have played an increa-singly important role as their performance and manufacturing processes continue to improve.This paper provides a review of the factors affecting the thermal conductivity of VIPs and presents a detailed overview of the research progress on core materials,barrier films,and getters.The current research status of VIPs is summarised,including their thermal conductivity,service life,and thermal bridging effects,as well as their applications in the field of architecture.This review aims to provide a comprehensive understanding for relevant practitioners on the factors influencing the thermal conductivity of VIPs,and based on which,measures can be taken to produce VIPs with lower thermal conductivity and longer service life.
文摘Wind tunnel experiment and CFD(computational fluid dynamics)simulation with LES(large eddy simulation)have been conducted to investigate the characteristics of peak wind force coefficients of porous panels mounted on the roofs of high-rise buildings.First,aerodynamic modelling of porous panels was discussed.The relation between pressure loss coefficient and porosity was obtained.Then,a wind tunnel experiment was conducted to measure the wind forces(net wind pressures)acting on solid and porous panels mounted on the roof of a high-rise building.Because it was difficult to measure the pressures on both sides of thin,porous panel at the same location simultaneously,we proposed to use the roof edge pressures near the panel for the panel’s inside-surface pressures.This experimental method was validated by a CFD simulation reproducing the wind tunnel experiment.The characteristics of peak wind force coefficients of porous panels mounted on the roofs of high-rise buildings were made clear.Finally,positive and negative peak wind force coefficients for designing the rooftop porous panels were proposed.
基金funded by the Spanish Ministerio de Ciencia,Innovación y Universidades,grant number RTC2019-007364-3(FPGM)by the Comunidad de Madrid through the direct grant with ref.SI4/PJI/2024-00233 for the promotion of research and technology transfer at the Universidad Autónoma de Madrid。
文摘Due to the continuous increase in global energy demand,photovoltaic solar energy generation and associated maintenance requirements have significantly expanded.One critical maintenance challenge in photovoltaic installations is detecting hot spots,localized overheating defects in solar cells that drastically reduce efficiency and can lead to permanent damage.Traditional methods for detecting these defects rely on manual inspections using thermal imaging,which are costly,labor-intensive,and impractical for large-scale installations.This research introduces an automated hybrid system based on two specialized convolutional neural networks deployed in a cascaded architecture.The first convolutional neural network efficiently detects and isolates individual solar panels from high-resolution aerial thermal images captured by drones.Subsequently,a second,more advanced convolutional neural network accurately classifies each isolated panel as either defective or healthy,effectively distinguishing genuine thermal anomalies from false positives caused by reflections or glare.Experimental validation on a real-world dataset comprising thousands of thermal images yielded exceptional accuracy,significantly reducing inspection time,costs,and the likelihood of false defect detections.This proposed system enhances the reliability and efficiency of photovoltaic plant inspections,thus contributing to improved operational performance and economic viability.
文摘A simulation method is proposed to predict the motion artifacts of plasma display panels （PDPs）. The method simulates the behavior of the human vision system when perceiving moving objects. The simulation is based on the measured temporal light properties of the display for each gray level and each phosphor. Both the effect of subfield arrangement and phosphor decay are involved. A novel algorithm is proposed to improve the calculation speed. The simulation model manages to predict the appearance of the motion image perceived by a human with a still image. The results are validated by a set of perceptual evaluation experiments. This rapid and accurate prediction of motion artifacts enables objective characterization of the PDP performance in this aspect.
基金This study was supported by National 9th-Five-Year Plan Project (No. 96-011-02-07-02).
文摘Since bamboo has the advantages of straight grain, beautiful color, high strength and toughness, and excellent abrasion resistance, bamboo-based panels have been widely used in the fields of vehicle, construction, ship building, furniture, and decoration to partly take the place of wood, steel, plastic etc in China. This paper briefly described the basic component units, including strip, sliver, and particle, of bamboo-based panel and pointed out that to design the structure of bamboo-based panels should follow the principle of symmetric structure, surface forming method, and structuring principle of equalizing stress. According to the processing methods and formation of component units, the authors classified the bamboo-based panels in China into 13 types and presented the manufacturing technique and uses of the bamboo products, such as plybamboo, bamboo flooring, and bamboo-wood composite products in detail. In the last part of the paper, much information were offered on the output, market, and selling prospect of each type of bamboo-based panels.
基金Project (51005010) supported by the National Natural Science Foundation of ChinaProject (20091102110021) supported by the Specialized Research Fund for the Doctoral Program of High Education of China
文摘In order to predict the buckling of stiffeners in the press bend forming of the integral panel,a method for solving the critical buckling load of the stiffeners in press bend forming process was proposed based on energy method,elastic-plastic mechanics and numerical analysis.Bend to buckle experiments were carried out on the designed press bend dies.It is found that the predicted results based on the proposed method agree well with the experimental results.With the proposed method,the buckling of the stiffeners in press bend forming of the aluminum alloy integral panels with high-stiffener can be predicted reasonably.
文摘The paper starts with a brief overview to the necessity of sheet metal forming simulation and the complexity of automobile panel forming, then leads to finite element analysis (FEA) which is a powerful simulation tool for analyzing complex three-dimensional sheet metal forming problems. The theory and features of the dynamic explicit finite element methods are introduced and the available various commercial finite element method codes used for sheet metal forming simulation in the world are discussed,and the civil and international status quo of automobile panel simulation as well. The front door outer panel of one certain new automobile is regarded as one example that the dynamic explicit FEM code Dynaform is used for the simulation of the front door outer panel forming process. Process defects such as ruptures are predicted. The improving methods can be given according to the simulation results. Foreground of sheet metal forming simulation is outlined.
文摘Stiffened thermosetting composite panels were fabricated with co-curing processing.In the co-curing processing,the temperature distribution in the composite panels was nonuniform.An investigation into the threedimensional cure simulation of T-shape stiffened thermosetting composite panels was presented.Flexible tools and locating tools were considered in the cure simulation.Temperature distribution in the composites was predicted as a function of the autoclave temperature history.A nonlinear transient heat transfer finite element model was developed to simulate the curing process of stiffened thermosetting composite panels.And a simulation example was presented to demonstrate the use of the present finite element procedure for analyzing composite curing process.The glass/polyester structure was investigated to provide insight into the nonuniform cure process and the effect of flexible tools and locating tools on temperature distribution.Temperature gradient in the intersection between the skin and the flange was shown to be strongly dependent on the structure of the flexible tools and the thickness of the skin.
文摘Experimental and analytical investigations on the residual strength of the stiffened LY12CZ aluminum alloy panels with widespread fatigue damage （WFD） are conducted. Nine stiffened LY12CZ aluminum alloy panels with three different types of damage are tested for residual strength. Each specimen is pre-cracked at rivet holes by saw cuts and subjected to a monotonically increasing tensile load until failure is occurred and the failure load is recorded. The stress intensity factors at the tips of the lead crack and the adjacent WFD cracks of the stiffened aluminum alloy panels are calculated by compounding approach and finite element method （FEM） respectively. The residual strength of the stiffened panels with WFD is evaluated by the engineering method with plastic zone linkup criterion and the FEM with apparent fracture toughness criterion respectively. The predicted residual strength agrees well with the experiment results. It indicates that in engineering practice these methods can be used for residual strength evaluation with the acceptable accuracy. It can be seen from this research that WFD can significantly reduce the residual strength and the critical crack length of the stiffened panels with WFD. The effect of WFD crack length on residual strength is also studied.
基金The financial supports from the National Key Research and Development Plan(2016YFB0201601)the Foundation for Innovative Research Groups of the National Natural Science Foundation(11821202)+3 种基金the National Natural Science Foundation(11872138,11702048,11732004 and 11772076)Program for Changjiang Scholars,Innovative Research Team in University(PCSIRT)Young Elite Scientists Sponsorship Program by CAST(2018QNRC001)Liaoning Natural Science Foundation Guidance Plan(20170520293)111 Project(B14013)are gratefully acknowledged.
文摘An explicit topology optimization method for the stiffener layout of composite stiffened panels is proposed based on moving morphable components(MMCs).The skin and stiffeners are considered as panels with different bending stiffnesses,with the use of equivalent stiffness method.Then the location and geometric properties of composite stiffeners are determined by several MMCs to perform topology optimization,which can greatly simplify the finite element model.With the objective of maximizing structural stiffness,several typical cases with various loading and boundary conditions are selected as numerical examples to demonstrate the proposed method.The numerical examples illustrate that the proposed method can provide clear stiffener layout and explicit geometry information,which is not limited within the framework of parameter and size optimization.The mechanical properties of composite stiffened panels can be fully enhanced.
基金supported by the National Natural Science Foundation of China (No. 11472216)support from China Scholarship Council (CSC)German Aerospace Center (DLR)
文摘A finite element formulation is presented for the analysis of the aeroelastic effect on the aerothermoacoustic response of metallic panels in supersonic flow. The first-order shear deformation theory(FSDT) and the von Karman nonlinear strain-displacement relationships are employed to consider the geometric nonlinearity induced by large deflections. The piston theory and the Gaussian white noise are used to simulate the mean flow aerodynamics and the turbulence from the boundary layer. The thermal loading is assumed to be steady and uniformly distributed, and the material properties are assumed to be temperature independent. The governing equations of motion are firstly formulated in structural node degrees of freedom by using the principle of virtual work,and then transformed and reduced to a set of coupled nonlinear Duffing oscillators in modal coordinates. The dynamic response of a panel is obtained by the Runge-Kutta integration method. The results indicate that the increasing aeroelastic effect can lead the panel vibration from a random motion to a highly ordered motion in the fashion of diffused limit cycle oscillations(LCOs), and remarkably alter the stochastic bifurcation and the spectrum of the aerothermoacoustic response.On the other hand there exists a counterbalance mechanism between the external random loading and the aeroelastic effect, which mainly functions through the nonlinear frequency-amplitude response. It is surmised that the aeroelastic effect must be considered in sonic fatigue analysis for panel structures in supersonic flow.
文摘To predict the attitude of satellite during the whole deployment process and evaluate the locking impact, a numerical flexible model of a certain satellite associated with four flexible honeycomb solar panels was established. The flexible solar panel was modeled by the finite element analysis (FEA), and the motion equations were derived by Lagrangian formulation. The locking process was based on the method of Hertzian contact, which enables one to predict the locking impact on the satellite and the subsequent oscillation of solar panels. The results reveal that locking operation has great impact on the attitude of the satellite, and the angular acceleration of satellite reaches 22.03°/s2 at the locking moment; the flexible solar panels model is feasible to predict the accurate response of the satellite during deployment and the oscillation of solar panels; the instantly impulsive force occurred during locking process is about 1.5 kN and the changing time is nearly 0.32 s. It provides an effective approach to present the flexible solar panels' deployment process and evaluate the locking impact.
基金partially funded by the National Natural Science Foundation of China (No.51805262)
文摘This paper proposes a model-based prognostics method that couples the Extended Kalman Filter(EKF) and a new developed linearization method. The proposed prognostics method is developed in the context of fatigue crack propagation in fuselage panels where the model parameters are unknown and the crack propagation is affected by different types of uncertainties. The coupled method is composed of two steps. The first step employs EKF to estimate the unknown model parameters and the current damage state. In the second step, the proposed efficient linearization method is applied to compute analytically the statistical distribution of the damage evolution path in some future time. A numerical case study is implemented to evaluate the performance of the proposed method. The results show that the coupled EKF-linearization method provides satisfactory results: the EKF algorithm well identifies the model parameters, and the linearization method gives comparable prediction results to Monte Carlo(MC) method while leading to very significant computational cost saving. The proposed prognostics method for fatigue crack growth can be used for developing predictive maintenance strategy for an aircraft fleet, in which case, the computational cost saving is significantly meaningful.
文摘Sloshing phenomenon in a moving container is a complicated free surface flow problem. It has a wide range of engineering applications, especially in tanker ships and Liquefied Natural Gas (LNG) carriers. When the tank in these vehicles is partially filled, it is essential to be able to evaluate the fluid dynamic loads on tank perimeter. Different geometric shapes such as rectangular, cylindrical, elliptical, spherical and circular conical have been suggested for ship storage tanks by previous researchers. In this paper a numerical model is developed based on incompressible and inviscid fluid motion for the liquid sloshing phenomenon. The coupled BEM-FEM is used to solve the governing equations and nonlinear free surface boundary conditions. The results are validated for rectangular container using data obtained for a horizontal periodic sway motion. Using the results of this model a new arrangement of trapezoidal shapes with quadratic sidewalls is suggested for tanker ship storage panels. The suggested geometric shape not only has a maximum surrounded tank volume to the constant available volume, but also reduces the sloshing effects more efficiently than the existing geometric shapes.
文摘Considering increasing rate of Iran population and consumption of wood panels, the authors investigated the per capita consump- tion of wood panels during the years from 1997 to 2007. The exponential smoothing method was used to obtain a per capita consumption panern of wood panels in lran for estimating demand of wood panels by the year of 2012. Results show that the consumption of particleboard, fiberboard, and medium density fiberboard in lran will increase by 33%, 72% and 107 %o, respectively, by the year of 2012; however, the consumption of plywood will increase only by 7% by 2012. The deficient amount of wood panels in Iran is estimated over 1400 000 m^3. The results of this study provide the technique reference for planners of wood panel industries in Iran in capital investment decisions.
文摘An increase in methane,spontaneous fire and bumping hazards in Polish hard coal mines,observed in the last two decades,led to the need to elaborate the tools allowing proper selection of a range of preventive measures to fight them at the stage of designing coal extraction.Designing the production of a coal seams in the conditions of associated methane and spontaneous fires hazards in Polish hard coal mines requires elaboration of the design standards for coal panels in gassy coal seams.This paper presents the guidelines on how to design production in the conditions of associated methane and spontaneous fire hazards.Presented tools and methodology since the very first research were many times verified by daily mining operations in the conditions of associated methane and spontaneous fire hazards,which confirms their significant contribution to the development of safe and economical mining operations.
