The mechanical, physical and thermal characterization of a composite made from woven raffia fiber vinifiera molded in epoxy resin intended for shipbuilding shows that the density (0.5 g/cm3 with a relative error of 0....The mechanical, physical and thermal characterization of a composite made from woven raffia fiber vinifiera molded in epoxy resin intended for shipbuilding shows that the density (0.5 g/cm3 with a relative error of 0.05 g/cm3) of the composite produced is lower than that of wood used in this field. The material has low porosity (9.8%) and is less absorbent (12.61%) than wood. The result of the thermal conductivity test by the hot plane method shows that this composite can contribute to the internal thermal insulation (an example of thermal conductivity is 0.32W/m.K) of floating boats. The mechanical tests of compression (young modulus is 22.86 GPa), resilience (1.238 J/Cm2) and hardness (233.04 BH30-2.5/187.5-15s) show that this composite is much harder and more absorbent than many wood and bio-composite materials used in the construction of pleasure boats. The abrasion test (0.005349) shows that this composite could well resist friction with the beach.展开更多
The objective of this study is to seek solutions to reduce the impact of buildings on climate change and to promote the use of local bio-sourced or geo-sourced materials for sustainable construction. Different samples...The objective of this study is to seek solutions to reduce the impact of buildings on climate change and to promote the use of local bio-sourced or geo-sourced materials for sustainable construction. Different samples of raw earth from 3 sites were taken in the commune of Mlomp. Geotechnical tests showed that the raw earth samples from sites 2 and 3 have more clay fraction while site 1 contains more sand. The fact of integrating fibers from crushed palm leaves (Borassus aethiopum) (2%, 4% and 6%) into the 3 raw earth samples reduced the mechanical resistance to compression and traction of the 3 raw earths. The experimental results of thermal tests on samples of earth mixtures with crushed Palma leaf fibers show a decrease in thermal conductivity as well as thermal effusivity as the percentages increase (2%, 4% and 6%) of fibers in raw earth for the 3 sites. This shows that this renewable composite material can help improve the thermal insulation of building envelopes.展开更多
The present study focuses on the flow of a yield-stress(Bingham)nanofluid,consisting of suspended Fe3O4 nanoparticles,subjected to a magnetic field in a backward-facing step duct(BFS)configuration.The duct is equipped...The present study focuses on the flow of a yield-stress(Bingham)nanofluid,consisting of suspended Fe3O4 nanoparticles,subjected to a magnetic field in a backward-facing step duct(BFS)configuration.The duct is equipped with a cylindrical obstacle,where the lower wall is kept at a constant temperature.The yield-stress nanofluid enters this duct at a cold temperature with fully developed velocity.The aim of the present investigation is to explore the influence of flow velocity(Re=10 to 200),nanoparticle concentration(ϕ=0 to 0.1),magnetic field intensity(Ha=0 to 100),and its inclination angle(γ=0 to 90)and nanofluid yield stress(Bn=0 to 20)on the thermal and hydrodynamic efficiency inside the backward-facing step.The numerical results have been obtained by resolving the momentum and energy balance equations using the Galerkin finite element method.The obtained results have indicated that an increase in Reynolds number and nanoparticle volume fraction enhances heat transfer.In contrast,a significant reduction is observed with an increase in Hartmann and Bingham numbers,resulting in quasi-immobilization of the fluid under the magnetic influence and radical solidification of this type of fluid,accompanied by the suppression of the vortex zone downstream of the cylindrical obstacle.This study sheds light on the complexity of this magnetically influenced fluid,with potential implications in various engineering and materials science fields.展开更多
This paper investigates the application of Direct Current Atmospheric Plasma Spraying(DC-APS)as a versatile thermal spray technique for the application of coatings with tailored properties to various substrates.The pr...This paper investigates the application of Direct Current Atmospheric Plasma Spraying(DC-APS)as a versatile thermal spray technique for the application of coatings with tailored properties to various substrates.The process uses a high-speed,high-temperature plasma jet to melt and propel the feedstock powder particles,making it particularly useful for improving the performance and durability of components in renewable energy systems such as solar cells,wind turbines,and fuel cells.The integration of nanostructured alumina(Al_(2)O_(3))thin films into multilayer coatings is considered a promising advancement that improves mechanical strength,thermal stability,and environmental resistance.The study highlights the importance of understanding injection parameters and their impact on coating properties and uses simulation tools such as the Jets&Poudres(JP)code for in-depth analysis.Furthermore,the paper discusses the implementation of Artificial Neural Networks(ANN)to optimize the coating process by predicting flight characteristics and improving operating conditions.The results show that ANN models are effective in achieving highly accurate prediction values,highlighting the potential of AI in improving thermal spray technology.展开更多
This manuscript deals with the effects of recycling on the static and dynamic properties of flax fibers reinforced thermoplastic composites.The corresponding thermoplastic used in this work is Elium resin.It’s the fi...This manuscript deals with the effects of recycling on the static and dynamic properties of flax fibers reinforced thermoplastic composites.The corresponding thermoplastic used in this work is Elium resin.It’s the first liquid thermoplastic resin that allows the production of recycled composite parts with promising mechanical behavior.It appeared on the resin market in 2014.But until now,no studies were available concerning how it can be recycled and reused.For this study,a thermocompression recycling process was investigated and applied to Elium resin.Flax fiber-reinforced Elium composites were produced using a resin infusion process and were subjected to different thermomechanical recycling operations.For each material,five recycling operations were carried out on the raw material.A total of 10 different materials were investigated and tested by means of tensile and free vibration tests to evaluate the effect of recycling on their behavior.In addition,a finite element model of the dynamic problem was developed to evaluate the loss factor and natural frequencies regarding different cases.The results obtained show that the failure tensile properties of Elium resin as well as flax fiber reinforced composites decrease during recycling operations.Conversely,recycling induces a rise in the elastic modulus.Moreover,improvement in the dynamic stiffness was observed with recycling operations.But repeated recycling appeared to have negligible effects on the loss factor of the recycled materials.The results obtained from the experiment and the numerical analyses were in close agreement.展开更多
Finding a basis of unification for the modeling of mechatronic systems is the search subject of several works.This paper is a part of a general research designed to the application of topology as a new approach for th...Finding a basis of unification for the modeling of mechatronic systems is the search subject of several works.This paper is a part of a general research designed to the application of topology as a new approach for the modeling of mechatronic systems.Particularly,the modeling of a one stage spur gear transmission using a topological approach is tackled.This approach is based on the concepts of topological collections and transformations and implemented using the MGS（modeling of general systems）language.The topological collections are used to specify the interconnection laws of the one stage spur gear transmission and the transformations are used to specify the local behavior laws of its different components.In order to validate this approach,simulation results are presented and compared with those obtained with MODELICA language using Dymola solver.Since good results are achieved,this approach might be used as a basis of unification for the modeling of mechatronic systems.展开更多
Based on experimental test results,flax fiber reinforced polymer composites are characterized by nonlinear visco-elastoplastic behavior.The aim of this work is to model the quasi-unidirectional flax fiber reinforced c...Based on experimental test results,flax fiber reinforced polymer composites are characterized by nonlinear visco-elastoplastic behavior.The aim of this work is to model the quasi-unidirectional flax fiber reinforced composite behavior through a three dimensional formulation with orthotropic elasticity and orthotropic plasticity using Hill criterion.The isotropic hardening and Johnson Cook parameters are identified from unidirectional tensile tests at different strain rates.The adjustment of Hill’s yield criterion is developed based on yield stresses obtained in tensile tests at different directions.The numerical integration of the constitutive equations is implemented in a user-defined material,UMAT subroutines for the commercial finite element code ABAQUS.Once model parameters are identified using tensile tests,the model needs to be validated by confronting it with other experimental results.That is why experimental and numerical three-point bending tests are carried out in order to validate the proposed model with tests that have not served for the identification.Finally,a numerical parametric study on low velocity impact of a flax/epoxy composite circular plate is investigated.展开更多
Faced with the world’s environmental and energy-related challenges,researchers are turning to innovative,sustainable and intelligent solutions to produce,store,and distribute energy.This work explores the trend of us...Faced with the world’s environmental and energy-related challenges,researchers are turning to innovative,sustainable and intelligent solutions to produce,store,and distribute energy.This work explores the trend of using a smart sensor to monitor the stability and efficiency of a salt-gradient solar pond.Several studies have been conducted to improve the thermal efficiency of salt-gradient solar ponds by introducing other materials.This study investigates the thermal and salinity behaviors of a pilot of smart salt-gradient solar ponds with(SGSP)and without(SGSPP)paraffin wax(PW)as a phase-change material(PCM).Temperature and salinity were measured experimentally using a smart sensor,with the measurements being used to investigate the stabilizing effects of placing the PCM in the solar pond’s lower convective zone.The experimental results show that the pond with the PCM(SGSPP)achieved greater thermal and salinity stability,with there being a lesser temperature and salinity gradient between the different layers when compared to a solar pond without thePCM(SGSP).The use of the PCM,therefore,helped control the maximum and minimum temperature of the pond’s storage zone.The UCZ has been found to operate approximately 4 degrees above the average ambient temperature of the day in the SGSPP and 7 degrees in SGSP.Moreover,an unstable situation is generated after 5 days from starting the operation and at 1.9 m from the bottom,and certain points have the tendency to be neutral from the upper depths in 1,3 m of the bottom.展开更多
CBR is an essential parameter in the design of flexible pavements in tropical countries.It is used to determine the bearing capacity of materials and to predict the stiffness moduli of untreated granular materials.How...CBR is an essential parameter in the design of flexible pavements in tropical countries.It is used to determine the bearing capacity of materials and to predict the stiffness moduli of untreated granular materials.However,determining it in the laboratory requires a great deal of effort and time.This naturally leads us to a numerical simulation of this test.This article presents the finite element simulation of the CBR test using cast3m,studying the influence of the E-CBR relationship.The results show that the correlation relations overestimate or overestimate the force-displacement curves.This shows that these relationships are not valid for all materials and must be used very carefully in our roads to avoid premature deterioration.展开更多
The investigation studied the plastic anisotropy of the severely-deformed Al-Mg-Si alloy by considering texture changes.The sample deformed via asymmetrical rolling under cross-shear condition was annealed at 598 K wh...The investigation studied the plastic anisotropy of the severely-deformed Al-Mg-Si alloy by considering texture changes.The sample deformed via asymmetrical rolling under cross-shear condition was annealed at 598 K where recrystallization was in progress.It is found upon annealing that the intensity of Cube({001}<100>)was comparable to those of plane-strain components while the intensities of shear components remained constant despite their instabilities in the recrystallization regime.After annealing,the average Lankford value(r)of the present sample was close to a unity whereas the in-plane anisotropy(△r)decreased,resulting in nearly isotropic characteristics of Al-Mg-Si alloy.展开更多
The factors influencing on soil expansion are reviewed in the paper. A mechanics model to determine swelling potential of expansive soils is presented. The mechanics model is based on the softening of expansive soil f...The factors influencing on soil expansion are reviewed in the paper. A mechanics model to determine swelling potential of expansive soils is presented. The mechanics model is based on the softening of expansive soil following absorption of water. The constitutive relationships of the mechanics model include the relationship among swelling under free load, swelling under load, and vertical pressure, and the relationship of swelling under free loading and swelling pressure. A concept of additional compression modulus is introduced and the method determining the modulus is proposed. Finally, the predicted results of swelling potential using the mechanics model compare well with the measured data.展开更多
To accelerate the exploration,screening,and discovery of structural high-entropy alloys with targeted properties,the newly developed High-Throughput Hot-Isostatic-Pressing based Micro-Synthesis Approach(HT-HIP-MSA)is ...To accelerate the exploration,screening,and discovery of structural high-entropy alloys with targeted properties,the newly developed High-Throughput Hot-Isostatic-Pressing based Micro-Synthesis Approach(HT-HIP-MSA)is employed to efficiently synthesize and characterize 85 combinatorial alloys in a 13-principal element alloying space.These Co Cr Fe Ni-based high entropy alloys span 1 quaternary,9 quinary,and 36 senary alloy systems,and their composition-structure-property relationships are characterized and analyzed experimentally and computationally.From the single-phase FCC CoCrFeNi alloy base,with Mn,Cu,Ti,Nb,Ta,Mo,W,Al,and Si as principal element alloying additions,we find(1)the extended Mn solubility in the single-phase FCC CoCrFeNi-Mn_(x) alloys,(2)the destabilizing behavior for most of the quinary and senary alloys,and(3)the distinctive solid-solution-strengthening effects in the alloys.In combining the computational methods,the HT-HIP-MSA can be systematic and economic to explore and refine the compositions,structures,and properties of structural high-entropy alloys.展开更多
Meta-sandwich composites with three-dimensional(3D)printed architecture structure are characterized by their high ability to absorb energy.In this paper,static and fatigue 3-point bending tests are implemented on a 3D...Meta-sandwich composites with three-dimensional(3D)printed architecture structure are characterized by their high ability to absorb energy.In this paper,static and fatigue 3-point bending tests are implemented on a 3D printed sandwich composites with a re-entrant honeycomb core.The skins,core and whole sandwich are manufactured using the same bio-based material which is polylactic acid with flax fiber reinforcement.Experimental tests are performed in order to evaluate the durability and the ability of this material to dissipate energy.First,static tests are conducted to study the bending behaviour of the sandwich beams,as well as to determine the failure parameters and the characteristic used in fatigue tests.Then,fatigue analyses were carried out to determine the fatigue resistance of these structures.The effects of the core density on the stiffness,hysteresis loop,energy absorption and loss factor,for two loading level,are determined.Moreover,the behaviour of this sandwich composite with re-entrant honeycomb core is compared with that of sandwiches with different core topologies.The results show that sandwich with high core density dissipate more energy,which results higher loss factors.The determined properties offer the most sensitive indicators of sandwich composite damage during its lifetime.This work aims to determine the static and fatigue properties of this material,thus,study its potential applications in industry.展开更多
This study aims to design and develop a pavement non-destructive quality testing device with the MASW method. Unlike the traditional acquisition techniques that plants geophones on the pavement, the presented approach...This study aims to design and develop a pavement non-destructive quality testing device with the MASW method. Unlike the traditional acquisition techniques that plants geophones on the pavement, the presented approach uses no-tip geophones, placed directly on the pavement surface to preserve its integrity. To proceed, a seismograph using an Arduino Due microcontroller connected to a Raspberry Pi 4 nano-computer was developed. The receivers consist of 6 4.5 Hz GD geophones connected together by a graduated tape to control the inter-trace distance and to in order to acquire data in land-streamer. The recording is triggered by a KY-038 sound sensor. The Arduino acts as an analog-to-digital converter while the Raspberry is used as a real-time data visualization and processing interface. The obtained seismic data has been processed using the Geopsy open-source software which allows the analysis and inversion of the dispersion curves. The studied system has been tested in 4 different sites. The obtained seismic V<sub>S</sub> and V<sub>P</sub> velocities as a function of the depth allowed to deduce the elastic properties of the pavement layers and to decide on their mechanical quality with the possibility of integrating the results in the road data banks.展开更多
Four empirical models are tested for fitting the T-y-x equilibrium data of ethanol-water mixture by minimizing the Root Mean Square （RMS） between equilibrium data and theoretical points. The total pressure of the co...Four empirical models are tested for fitting the T-y-x equilibrium data of ethanol-water mixture by minimizing the Root Mean Square （RMS） between equilibrium data and theoretical points. The total pressure of the correspondent data is 101.3 kPa. All models parameters are also identified. The study suggests that NRTL model fits the equilibrium data best with RMS = 0.4 %.展开更多
<div style="text-align:justify;"> <span style="font-family:Verdana;">Seismic refraction investigations have been carried out in Bakel, Eastern Senegal. The purpose was to map geometrica...<div style="text-align:justify;"> <span style="font-family:Verdana;">Seismic refraction investigations have been carried out in Bakel, Eastern Senegal. The purpose was to map geometrical relationship between the existing rock types and the Panafrican quarzitic basement, which is valuable information for the project of the Bakel fluviatile port construction. Four seismic refraction profiles were acquired. The obtained data have been processed by inversion. The obtained four seismic P-wave velocity profiles have been integrated to obtain a 3D model. By comparing the outcropping geological formations with the observed seismic data at the surface, it was possible to identify the lithology corresponding to each measured range of seismic velocity for the alluvium, the weathered bed rock, and the fresh rock. The results showed that the depth of the fresh rock of the basement varies from 0 to 18 meters above the sea level, with a deepening toward the Senegal River and toward the Northern part of the studied area. The presence of alluviums and their thickness are linked to the existence of bays and gulfs. The results of this study give valuable information for the river bed dredging cost assessment prior to the port construction phase.</span> </div>展开更多
This research work aims at modeling the creep behavior of a material by a non-linear schapery’s viscoelastic model. We started with analytical part where three powerful methods of creep modeling have been developed a...This research work aims at modeling the creep behavior of a material by a non-linear schapery’s viscoelastic model. We started with analytical part where three powerful methods of creep modeling have been developed and compared. That is the Heaviside, the Nordin and Varna and lastly our own proposed methods. From this preliminary study, it came out that our method is different to the two others because we took into account the loading time at the creep beginning. Besides we studied several loading programs and retained a five order non-linear polynomial which is the program that gave us satisfactory results. The other loading functions led to divergent results and wasn’t present here as consequence. In the second part of this work, we devoted ourselves to the determination of non-linear parameters in the schapery’s viscoelasticity equation, through a well developed and illustrated methodology. From this study, it is straight forward that non-linear parameters are stress dependent;confirming the results of several authors that preceded us in this studying field.展开更多
Mechanical agitation in baffled vessels with turbines plays a vital role in achieving homogeneous fluid mixing and promoting various transfer operations.Therefore,designing vessels with optimal energy efficiency and f...Mechanical agitation in baffled vessels with turbines plays a vital role in achieving homogeneous fluid mixing and promoting various transfer operations.Therefore,designing vessels with optimal energy efficiency and flow dynamics is essential to enhance operational performance and eliminate flow perturbations.Hence,the present research focuses on a numerical investigation of the impact of inclined slots with different angles installed at the side-wall of a cylindrical vessel equipped with a Rushton turbine.This study explores power consumption and vortex size while considering various rotation directions of the impeller with different rotation speeds.The numerical simulations are conducted for Reynolds numbers ranging from 104 to 105,using the RANS k-εturbulence model to govern the flow inside the stirred vessel,accounting for mass and momentum balances.The results have shown that the installation of slots reduces power consumption and vortex size compared to conventional vessel configu-rations.Moreover,increasing the slot angle from 0 to 32.5°further reduces energy consumption and vortex size,especially with negative rotation speeds.On the other hand,increasing the Reynolds numbers leads to a decrease in power consumption and an increase in vortex size.The present research therefore proposes a design for con-structing Rushton-turbine stirred vessels offering optimal operation,characterized by reduced energy consumption and minimized vortex size.展开更多
Periodic variations of warp tension during a weaving cycle result in corresponding change of back rest position, and the oscillation of back rest affects the fluctuation of warp yarn in return. A mechanical model of b...Periodic variations of warp tension during a weaving cycle result in corresponding change of back rest position, and the oscillation of back rest affects the fluctuation of warp yarn in return. A mechanical model of back rest system of looms is presented on basis of auto control theory, and the factors affecting the dynamic performance of the back rest are analyzed. In the model, warp yarn is regarded as a viscoelastic medium, and the adjustable parameters and the adjusting range of the back rest system are increased, so the loom's applicability for the fabric's variety is enhanced. Finally, the methods of designing and adjusting the back rest are discussed, and a trend of back rest system development is given.展开更多
The Senegalese road network is strongly influenced in the long term by seasonal variations in climate and weather conditions. Indeed, much of the damage is due to these environmental factors. The objective of th... The Senegalese road network is strongly influenced in the long term by seasonal variations in climate and weather conditions. Indeed, much of the damage is due to these environmental factors. The objective of this paper is to study the behaviour of bituminous structures under the effect of high temperatures. Material samples were taken for a physico-mechanical characterization of the coated components. The results show that Marshall creep (2.87, 3.39, 5, 5.5 mm) and the bitumen penetrability increase with the increasing of temperatures respectively from 34°C to 45<span style="white-space:normal;">°</span>C and from 20<span style="white-space:normal;">°</span>C to 50<span style="white-space:normal;">°</span>C. Marshall Stability drops from 15.81 kN to 11.31 kN for temperatures between 34<span style="white-space:normal;">°</span>C and 45<span style="white-space:normal;">°</span>C. The simulation carried out on Alize-LCPC shows an increase in distortions of traction at the basis of the rolling layer and at the top of the platform if temperatures vary between 34<span style="white-space:normal;">°</span>C and 45<span style="white-space:normal;">°</span>C. This work makes it possible to conform that the bituminous concrete is thermally sensitive and the hypothesis of fixing the constant modulus of the bituminous layers in Senegal for all projects remains unsuitable for a good dimensioning of sustainable road structures. The knowledge of the equivalent regional temperature will make it possible to produce quality pavements with a long lifespan.展开更多
文摘The mechanical, physical and thermal characterization of a composite made from woven raffia fiber vinifiera molded in epoxy resin intended for shipbuilding shows that the density (0.5 g/cm3 with a relative error of 0.05 g/cm3) of the composite produced is lower than that of wood used in this field. The material has low porosity (9.8%) and is less absorbent (12.61%) than wood. The result of the thermal conductivity test by the hot plane method shows that this composite can contribute to the internal thermal insulation (an example of thermal conductivity is 0.32W/m.K) of floating boats. The mechanical tests of compression (young modulus is 22.86 GPa), resilience (1.238 J/Cm2) and hardness (233.04 BH30-2.5/187.5-15s) show that this composite is much harder and more absorbent than many wood and bio-composite materials used in the construction of pleasure boats. The abrasion test (0.005349) shows that this composite could well resist friction with the beach.
文摘The objective of this study is to seek solutions to reduce the impact of buildings on climate change and to promote the use of local bio-sourced or geo-sourced materials for sustainable construction. Different samples of raw earth from 3 sites were taken in the commune of Mlomp. Geotechnical tests showed that the raw earth samples from sites 2 and 3 have more clay fraction while site 1 contains more sand. The fact of integrating fibers from crushed palm leaves (Borassus aethiopum) (2%, 4% and 6%) into the 3 raw earth samples reduced the mechanical resistance to compression and traction of the 3 raw earths. The experimental results of thermal tests on samples of earth mixtures with crushed Palma leaf fibers show a decrease in thermal conductivity as well as thermal effusivity as the percentages increase (2%, 4% and 6%) of fibers in raw earth for the 3 sites. This shows that this renewable composite material can help improve the thermal insulation of building envelopes.
文摘The present study focuses on the flow of a yield-stress(Bingham)nanofluid,consisting of suspended Fe3O4 nanoparticles,subjected to a magnetic field in a backward-facing step duct(BFS)configuration.The duct is equipped with a cylindrical obstacle,where the lower wall is kept at a constant temperature.The yield-stress nanofluid enters this duct at a cold temperature with fully developed velocity.The aim of the present investigation is to explore the influence of flow velocity(Re=10 to 200),nanoparticle concentration(ϕ=0 to 0.1),magnetic field intensity(Ha=0 to 100),and its inclination angle(γ=0 to 90)and nanofluid yield stress(Bn=0 to 20)on the thermal and hydrodynamic efficiency inside the backward-facing step.The numerical results have been obtained by resolving the momentum and energy balance equations using the Galerkin finite element method.The obtained results have indicated that an increase in Reynolds number and nanoparticle volume fraction enhances heat transfer.In contrast,a significant reduction is observed with an increase in Hartmann and Bingham numbers,resulting in quasi-immobilization of the fluid under the magnetic influence and radical solidification of this type of fluid,accompanied by the suppression of the vortex zone downstream of the cylindrical obstacle.This study sheds light on the complexity of this magnetically influenced fluid,with potential implications in various engineering and materials science fields.
文摘This paper investigates the application of Direct Current Atmospheric Plasma Spraying(DC-APS)as a versatile thermal spray technique for the application of coatings with tailored properties to various substrates.The process uses a high-speed,high-temperature plasma jet to melt and propel the feedstock powder particles,making it particularly useful for improving the performance and durability of components in renewable energy systems such as solar cells,wind turbines,and fuel cells.The integration of nanostructured alumina(Al_(2)O_(3))thin films into multilayer coatings is considered a promising advancement that improves mechanical strength,thermal stability,and environmental resistance.The study highlights the importance of understanding injection parameters and their impact on coating properties and uses simulation tools such as the Jets&Poudres(JP)code for in-depth analysis.Furthermore,the paper discusses the implementation of Artificial Neural Networks(ANN)to optimize the coating process by predicting flight characteristics and improving operating conditions.The results show that ANN models are effective in achieving highly accurate prediction values,highlighting the potential of AI in improving thermal spray technology.
文摘This manuscript deals with the effects of recycling on the static and dynamic properties of flax fibers reinforced thermoplastic composites.The corresponding thermoplastic used in this work is Elium resin.It’s the first liquid thermoplastic resin that allows the production of recycled composite parts with promising mechanical behavior.It appeared on the resin market in 2014.But until now,no studies were available concerning how it can be recycled and reused.For this study,a thermocompression recycling process was investigated and applied to Elium resin.Flax fiber-reinforced Elium composites were produced using a resin infusion process and were subjected to different thermomechanical recycling operations.For each material,five recycling operations were carried out on the raw material.A total of 10 different materials were investigated and tested by means of tensile and free vibration tests to evaluate the effect of recycling on their behavior.In addition,a finite element model of the dynamic problem was developed to evaluate the loss factor and natural frequencies regarding different cases.The results obtained show that the failure tensile properties of Elium resin as well as flax fiber reinforced composites decrease during recycling operations.Conversely,recycling induces a rise in the elastic modulus.Moreover,improvement in the dynamic stiffness was observed with recycling operations.But repeated recycling appeared to have negligible effects on the loss factor of the recycled materials.The results obtained from the experiment and the numerical analyses were in close agreement.
文摘Finding a basis of unification for the modeling of mechatronic systems is the search subject of several works.This paper is a part of a general research designed to the application of topology as a new approach for the modeling of mechatronic systems.Particularly,the modeling of a one stage spur gear transmission using a topological approach is tackled.This approach is based on the concepts of topological collections and transformations and implemented using the MGS（modeling of general systems）language.The topological collections are used to specify the interconnection laws of the one stage spur gear transmission and the transformations are used to specify the local behavior laws of its different components.In order to validate this approach,simulation results are presented and compared with those obtained with MODELICA language using Dymola solver.Since good results are achieved,this approach might be used as a basis of unification for the modeling of mechatronic systems.
文摘Based on experimental test results,flax fiber reinforced polymer composites are characterized by nonlinear visco-elastoplastic behavior.The aim of this work is to model the quasi-unidirectional flax fiber reinforced composite behavior through a three dimensional formulation with orthotropic elasticity and orthotropic plasticity using Hill criterion.The isotropic hardening and Johnson Cook parameters are identified from unidirectional tensile tests at different strain rates.The adjustment of Hill’s yield criterion is developed based on yield stresses obtained in tensile tests at different directions.The numerical integration of the constitutive equations is implemented in a user-defined material,UMAT subroutines for the commercial finite element code ABAQUS.Once model parameters are identified using tensile tests,the model needs to be validated by confronting it with other experimental results.That is why experimental and numerical three-point bending tests are carried out in order to validate the proposed model with tests that have not served for the identification.Finally,a numerical parametric study on low velocity impact of a flax/epoxy composite circular plate is investigated.
基金supported and funded by the Deanship of Scientific Research at Imam Mohammad Ibn Saud Islamic University(IMSIU)(Grant Number IMSIU-RG23098).
文摘Faced with the world’s environmental and energy-related challenges,researchers are turning to innovative,sustainable and intelligent solutions to produce,store,and distribute energy.This work explores the trend of using a smart sensor to monitor the stability and efficiency of a salt-gradient solar pond.Several studies have been conducted to improve the thermal efficiency of salt-gradient solar ponds by introducing other materials.This study investigates the thermal and salinity behaviors of a pilot of smart salt-gradient solar ponds with(SGSP)and without(SGSPP)paraffin wax(PW)as a phase-change material(PCM).Temperature and salinity were measured experimentally using a smart sensor,with the measurements being used to investigate the stabilizing effects of placing the PCM in the solar pond’s lower convective zone.The experimental results show that the pond with the PCM(SGSPP)achieved greater thermal and salinity stability,with there being a lesser temperature and salinity gradient between the different layers when compared to a solar pond without thePCM(SGSP).The use of the PCM,therefore,helped control the maximum and minimum temperature of the pond’s storage zone.The UCZ has been found to operate approximately 4 degrees above the average ambient temperature of the day in the SGSPP and 7 degrees in SGSP.Moreover,an unstable situation is generated after 5 days from starting the operation and at 1.9 m from the bottom,and certain points have the tendency to be neutral from the upper depths in 1,3 m of the bottom.
文摘CBR is an essential parameter in the design of flexible pavements in tropical countries.It is used to determine the bearing capacity of materials and to predict the stiffness moduli of untreated granular materials.However,determining it in the laboratory requires a great deal of effort and time.This naturally leads us to a numerical simulation of this test.This article presents the finite element simulation of the CBR test using cast3m,studying the influence of the E-CBR relationship.The results show that the correlation relations overestimate or overestimate the force-displacement curves.This shows that these relationships are not valid for all materials and must be used very carefully in our roads to avoid premature deterioration.
基金supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (MOE), Republic of Korea (No. NRF2017R1D1A1A09000921)
文摘The investigation studied the plastic anisotropy of the severely-deformed Al-Mg-Si alloy by considering texture changes.The sample deformed via asymmetrical rolling under cross-shear condition was annealed at 598 K where recrystallization was in progress.It is found upon annealing that the intensity of Cube({001}<100>)was comparable to those of plane-strain components while the intensities of shear components remained constant despite their instabilities in the recrystallization regime.After annealing,the average Lankford value(r)of the present sample was close to a unity whereas the in-plane anisotropy(△r)decreased,resulting in nearly isotropic characteristics of Al-Mg-Si alloy.
文摘The factors influencing on soil expansion are reviewed in the paper. A mechanics model to determine swelling potential of expansive soils is presented. The mechanics model is based on the softening of expansive soil following absorption of water. The constitutive relationships of the mechanics model include the relationship among swelling under free load, swelling under load, and vertical pressure, and the relationship of swelling under free loading and swelling pressure. A concept of additional compression modulus is introduced and the method determining the modulus is proposed. Finally, the predicted results of swelling potential using the mechanics model compare well with the measured data.
基金financially supported by the National Key Research and Development Program of China(2016YFB0700300)the financial support from National Natural Science Foundation of China(No.52001271)+2 种基金the supports from the National Science Foundation(DMR-1611180 and 1809640)the US Army Research Office(W911NF-13-1-0438 and W911NF-19-20049)the Swiss National Science Foundation for support of this work by project"Harnessing atomicscale randomness:design and optimization of mechanical performance in High Entropy Alloys"(Project 200021_118198/1)。
文摘To accelerate the exploration,screening,and discovery of structural high-entropy alloys with targeted properties,the newly developed High-Throughput Hot-Isostatic-Pressing based Micro-Synthesis Approach(HT-HIP-MSA)is employed to efficiently synthesize and characterize 85 combinatorial alloys in a 13-principal element alloying space.These Co Cr Fe Ni-based high entropy alloys span 1 quaternary,9 quinary,and 36 senary alloy systems,and their composition-structure-property relationships are characterized and analyzed experimentally and computationally.From the single-phase FCC CoCrFeNi alloy base,with Mn,Cu,Ti,Nb,Ta,Mo,W,Al,and Si as principal element alloying additions,we find(1)the extended Mn solubility in the single-phase FCC CoCrFeNi-Mn_(x) alloys,(2)the destabilizing behavior for most of the quinary and senary alloys,and(3)the distinctive solid-solution-strengthening effects in the alloys.In combining the computational methods,the HT-HIP-MSA can be systematic and economic to explore and refine the compositions,structures,and properties of structural high-entropy alloys.
文摘Meta-sandwich composites with three-dimensional(3D)printed architecture structure are characterized by their high ability to absorb energy.In this paper,static and fatigue 3-point bending tests are implemented on a 3D printed sandwich composites with a re-entrant honeycomb core.The skins,core and whole sandwich are manufactured using the same bio-based material which is polylactic acid with flax fiber reinforcement.Experimental tests are performed in order to evaluate the durability and the ability of this material to dissipate energy.First,static tests are conducted to study the bending behaviour of the sandwich beams,as well as to determine the failure parameters and the characteristic used in fatigue tests.Then,fatigue analyses were carried out to determine the fatigue resistance of these structures.The effects of the core density on the stiffness,hysteresis loop,energy absorption and loss factor,for two loading level,are determined.Moreover,the behaviour of this sandwich composite with re-entrant honeycomb core is compared with that of sandwiches with different core topologies.The results show that sandwich with high core density dissipate more energy,which results higher loss factors.The determined properties offer the most sensitive indicators of sandwich composite damage during its lifetime.This work aims to determine the static and fatigue properties of this material,thus,study its potential applications in industry.
文摘This study aims to design and develop a pavement non-destructive quality testing device with the MASW method. Unlike the traditional acquisition techniques that plants geophones on the pavement, the presented approach uses no-tip geophones, placed directly on the pavement surface to preserve its integrity. To proceed, a seismograph using an Arduino Due microcontroller connected to a Raspberry Pi 4 nano-computer was developed. The receivers consist of 6 4.5 Hz GD geophones connected together by a graduated tape to control the inter-trace distance and to in order to acquire data in land-streamer. The recording is triggered by a KY-038 sound sensor. The Arduino acts as an analog-to-digital converter while the Raspberry is used as a real-time data visualization and processing interface. The obtained seismic data has been processed using the Geopsy open-source software which allows the analysis and inversion of the dispersion curves. The studied system has been tested in 4 different sites. The obtained seismic V<sub>S</sub> and V<sub>P</sub> velocities as a function of the depth allowed to deduce the elastic properties of the pavement layers and to decide on their mechanical quality with the possibility of integrating the results in the road data banks.
文摘Four empirical models are tested for fitting the T-y-x equilibrium data of ethanol-water mixture by minimizing the Root Mean Square （RMS） between equilibrium data and theoretical points. The total pressure of the correspondent data is 101.3 kPa. All models parameters are also identified. The study suggests that NRTL model fits the equilibrium data best with RMS = 0.4 %.
文摘<div style="text-align:justify;"> <span style="font-family:Verdana;">Seismic refraction investigations have been carried out in Bakel, Eastern Senegal. The purpose was to map geometrical relationship between the existing rock types and the Panafrican quarzitic basement, which is valuable information for the project of the Bakel fluviatile port construction. Four seismic refraction profiles were acquired. The obtained data have been processed by inversion. The obtained four seismic P-wave velocity profiles have been integrated to obtain a 3D model. By comparing the outcropping geological formations with the observed seismic data at the surface, it was possible to identify the lithology corresponding to each measured range of seismic velocity for the alluvium, the weathered bed rock, and the fresh rock. The results showed that the depth of the fresh rock of the basement varies from 0 to 18 meters above the sea level, with a deepening toward the Senegal River and toward the Northern part of the studied area. The presence of alluviums and their thickness are linked to the existence of bays and gulfs. The results of this study give valuable information for the river bed dredging cost assessment prior to the port construction phase.</span> </div>
文摘This research work aims at modeling the creep behavior of a material by a non-linear schapery’s viscoelastic model. We started with analytical part where three powerful methods of creep modeling have been developed and compared. That is the Heaviside, the Nordin and Varna and lastly our own proposed methods. From this preliminary study, it came out that our method is different to the two others because we took into account the loading time at the creep beginning. Besides we studied several loading programs and retained a five order non-linear polynomial which is the program that gave us satisfactory results. The other loading functions led to divergent results and wasn’t present here as consequence. In the second part of this work, we devoted ourselves to the determination of non-linear parameters in the schapery’s viscoelasticity equation, through a well developed and illustrated methodology. From this study, it is straight forward that non-linear parameters are stress dependent;confirming the results of several authors that preceded us in this studying field.
文摘Mechanical agitation in baffled vessels with turbines plays a vital role in achieving homogeneous fluid mixing and promoting various transfer operations.Therefore,designing vessels with optimal energy efficiency and flow dynamics is essential to enhance operational performance and eliminate flow perturbations.Hence,the present research focuses on a numerical investigation of the impact of inclined slots with different angles installed at the side-wall of a cylindrical vessel equipped with a Rushton turbine.This study explores power consumption and vortex size while considering various rotation directions of the impeller with different rotation speeds.The numerical simulations are conducted for Reynolds numbers ranging from 104 to 105,using the RANS k-εturbulence model to govern the flow inside the stirred vessel,accounting for mass and momentum balances.The results have shown that the installation of slots reduces power consumption and vortex size compared to conventional vessel configu-rations.Moreover,increasing the slot angle from 0 to 32.5°further reduces energy consumption and vortex size,especially with negative rotation speeds.On the other hand,increasing the Reynolds numbers leads to a decrease in power consumption and an increase in vortex size.The present research therefore proposes a design for con-structing Rushton-turbine stirred vessels offering optimal operation,characterized by reduced energy consumption and minimized vortex size.
文摘Periodic variations of warp tension during a weaving cycle result in corresponding change of back rest position, and the oscillation of back rest affects the fluctuation of warp yarn in return. A mechanical model of back rest system of looms is presented on basis of auto control theory, and the factors affecting the dynamic performance of the back rest are analyzed. In the model, warp yarn is regarded as a viscoelastic medium, and the adjustable parameters and the adjusting range of the back rest system are increased, so the loom's applicability for the fabric's variety is enhanced. Finally, the methods of designing and adjusting the back rest are discussed, and a trend of back rest system development is given.
文摘 The Senegalese road network is strongly influenced in the long term by seasonal variations in climate and weather conditions. Indeed, much of the damage is due to these environmental factors. The objective of this paper is to study the behaviour of bituminous structures under the effect of high temperatures. Material samples were taken for a physico-mechanical characterization of the coated components. The results show that Marshall creep (2.87, 3.39, 5, 5.5 mm) and the bitumen penetrability increase with the increasing of temperatures respectively from 34°C to 45<span style="white-space:normal;">°</span>C and from 20<span style="white-space:normal;">°</span>C to 50<span style="white-space:normal;">°</span>C. Marshall Stability drops from 15.81 kN to 11.31 kN for temperatures between 34<span style="white-space:normal;">°</span>C and 45<span style="white-space:normal;">°</span>C. The simulation carried out on Alize-LCPC shows an increase in distortions of traction at the basis of the rolling layer and at the top of the platform if temperatures vary between 34<span style="white-space:normal;">°</span>C and 45<span style="white-space:normal;">°</span>C. This work makes it possible to conform that the bituminous concrete is thermally sensitive and the hypothesis of fixing the constant modulus of the bituminous layers in Senegal for all projects remains unsuitable for a good dimensioning of sustainable road structures. The knowledge of the equivalent regional temperature will make it possible to produce quality pavements with a long lifespan.
