With the swift advancement of industrial automation,robots have emerged as an essential component in emerging industries and high-end equipment,thereby propelling industrial production towards greater intelligence and...With the swift advancement of industrial automation,robots have emerged as an essential component in emerging industries and high-end equipment,thereby propelling industrial production towards greater intelligence and efficiency.This paper reviews the pivotal technologies for motion planning of robots engaged in contact tasks within industrial automation contexts,encompassing environmental recognition,trajectory generation strategies,and sim-to-real transfer.Environmental recognition technology empowers robots to accurately discern objects and obstacles in their operational environment.Trajectory generation strategies formulate optimal motion paths based on environmental data and task specifications.Sim-to-real transfer is committed to effectively translating strategies from simulated environments to actual production,thereby diminishing the discrepancies between simulation and reality.The article also delves into the application of artificial intelligence in robot motion planning and how embodied intelligence models catalyze the evolution of robotics technology towards enhanced intelligence and automation.The paper concludes with a synthesis of the methodologies addressing this challenge and a perspective on the myriad challenges that warrant attention.展开更多
The hysteretic behavior and nonlinearity of the equivalent material coefficient of macro fiber composites（MFC） under staircase input conditions are investigated using the Preisach model.Based on a database of first ...The hysteretic behavior and nonlinearity of the equivalent material coefficient of macro fiber composites（MFC） under staircase input conditions are investigated using the Preisach model.Based on a database of first order reversal curves, formulas are derived to predict the hysteresis of strain output and nonlinearity of the equivalent piezoelectric coefficient of MFCs. Formulae are verified by comparing the predicted strains with the measured strains of three MFC specimens,which are driven by a random sequence of staircase voltage inputs. The coefficients obtained by the formulae and experimentation coincide. Further results indicate that the equivalent piezoelectric strain coefficient depends greatly on the value of drive voltage across the entire input range, and the coefficient is asymmetric across the negative and positive input ranges. Deflection testing of an MFC composite cantilever demonstrates the importance of taking the nonlinearity of the equivalent piezoelectric coefficient into consideration in the application of actuation.展开更多
In this work,an enriched model describing the longitudinal wave propagation is established based on Mindlin’s Second Strain Gradient(SSG)theory,which can describe the heterogeneity caused by the micro-structure inter...In this work,an enriched model describing the longitudinal wave propagation is established based on Mindlin’s Second Strain Gradient(SSG)theory,which can describe the heterogeneity caused by the micro-structure interactions in the frame of continuum mechanics.The governing equation and associated boundary conditions are derived based on Hamilton’s principle,then the dispersion relation of non-classical longitudinal wave together with the extra-waves appearing exclusively in SSG theory model are investigated.The investigations are based on the modal density,energy flow,and forced response of the rod.Wave transmission and reflection through planar interfaces based on the proposed model have been calculated.Finally,the results of the enriched model are well interpreted by comparing with the classical theory results,and some useful conclusions are derived on the SSG theory based model in the wave propagation characterization.展开更多
Hypericin(C30H16O8)is a naturally occurring substance,an anthraquinone derived from St.John’s wort,possessing outstanding antiviral,antitumor,antibacterial,and antioxidant properties.Today,hypericin is primarily used...Hypericin(C30H16O8)is a naturally occurring substance,an anthraquinone derived from St.John’s wort,possessing outstanding antiviral,antitumor,antibacterial,and antioxidant properties.Today,hypericin is primarily used in medicinal applications.It is a small,flat organic molecule with a graphene-like core surrounded by oxidized functions,suggesting it could act as a graphene precursor in tribological contacts.Therefore,we investigated the lubrication properties of hypericin as an additive in glycerol,used as a base oil.It is well established that glycerol is superlubricious under full and thin film elastohydrodynamic(EHD)lubrication regimes but generally fails with steel under more severe conditions(mixed and boundary regimes).We studied the effect of hypericin added to glycerol for steel-on-steel and steel-on-silicon friction pairs.For the steel-on-steel configuration,results show that hypericin is a strong anti-wear additive due to its antioxidant properties that scavenge OH radicals.Moreover,hypericin is also an efficient friction-reducing agent,providing a steady state and robust ultralow friction coefficient(0.02–0.03).Thus,it outperforms most traditional additive formulations under the same conditions,although it does not achieve superlubricity(coefficient of friction(CoF)<0.01)under more severe conditions.For steel-on-silicon,hypericin significantly extends the superlubricity regime of glycerol to lambda ratios well below unity(low sliding speeds).The mechanism of superlubricity is attributed to the friction-induced formation of graphene layers from hypericin molecules,smoothing friction surfaces,and operating a hybrid liquid–solid superlubricious system.展开更多
While the implementation of sustainable urban planning has proven to be one of the primary goals to reduce the climate change impact,the rapid adoption of nearly Zero Energy Buildings(nZEB)concept in the building sect...While the implementation of sustainable urban planning has proven to be one of the primary goals to reduce the climate change impact,the rapid adoption of nearly Zero Energy Buildings(nZEB)concept in the building sector is inevitable to reach that objective.Following this trend,this article focuses on the implementation of a parametric digital workflow to evaluate the energy performance of a nearly zero energy high-rise 23-storey office building in the climatic and urban contexts of Casablanca at the early design stage.In the scope of this study,Grasshopper-based digital workflow permits to investigate the impact of 147 parametric building designs,which are generated by varying the building’s shape factor and orientation on thermal cooling and heating demand and global solar energy production.The outcomes of this holistic methodology highlight the design trade-offs between energy efficiency strategies and energy performance of building-integrated photovoltaic(BIPV)and photovoltaic(PV)systems,aiming to reach optimized nZEB.Moreover,the results of the study suggest that it is possible to reach an annual load match equivalent to 29.68%.The findings also underscore the significant role of the BIPV systems in shifting towards the goal of net zero energy,accounting for up to 64.43%of the total solar energy output and contributing in total up to 17.62%to the yearly self-sufficiency.In addition,the energy balance evaluation,when assessed on an hourly basis,reveals that the BIPV system significantly improves the daily load cover factor,achieving a value of 12.45%,and increases up to 20.62%when considering also the rooftop PV,particularly during spring season.Finally,the capacity credit factor is improved by up to 31.27%,which is a significant share of grid connection reduction compared to the same building relying totally on the grid for its energy needs.展开更多
Aluminium alloys are commonly used as lightweight materials in the automotive industry.This non-ferrous family of metallic alloys offers a high versatility of properties and designs.To reduce weight and improve safety...Aluminium alloys are commonly used as lightweight materials in the automotive industry.This non-ferrous family of metallic alloys offers a high versatility of properties and designs.To reduce weight and improve safety,high strength-to-weight ratio alloys(e.g.6XXX and 7XXX),are increasingly implemented in vehicles.However,these alloys exhibit low formability and experience considerable springback during cold forming,and are therefore hot formed.During forming,severe adhesion(i.e.galling)of aluminium onto the die surface takes place.This phenomenon has a detrimental effect on the surface properties,geometrical tolerances of the formed parts and maintenance of the dies.The effect of surface engineering as well as lubricant chemistry on galling has not been sufficiently investigated.Diamond-like carbon(DLC)and CrN physical vapour deposition(PVD)coated steel have been studied to reduce aluminium transfer.However,the interaction between lubricants and PVD coatings during hot forming of aluminium alloys is not yet fully understood.The present study thus aims to characterise the high temperature tribological behaviour of selected PVD coatings and lubricants during sliding against aluminium alloy.The objectives are to first select promising lubricant-coating combinations and then to study their tribological response in a high-temperature reciprocating friction and wear tester.Dry and lubricated tests were carried out at 300℃ using a commercial polymer lubricant.Tests using DLC,CrN,CrTiN,and CrAIN coated tool steel were compared to uncoated tool steel reference tests.The initial and worn test specimen surfaces were analysed with a 3-dimensional(3D)optical profiler,scanning electron microscope(SEM)and energy dispersive X-ray spectroscope(EDS)as to understand the wear mechanisms.The results showed formation of tribolayers in the contact zone,reducing both friction and wear.The stability of these layers highly depends on both the coatings'roughness and chemical affinity towards aluminium.The DLC and CrN coatings combined with the polymer lubricant were the most effective in reducing aluminium transfer.展开更多
Friction tests have been carried out on bearing steel friction pairs coated with a-C:H and ta-C under lubricated conditions with 1-hexadecene and pure oleic acid,respectively.Main results show that ta-C leads to the s...Friction tests have been carried out on bearing steel friction pairs coated with a-C:H and ta-C under lubricated conditions with 1-hexadecene and pure oleic acid,respectively.Main results show that ta-C leads to the super-low regime with oleic acid(friction coefficient below 0.01)and that a-C:H is quite well lubricated by 1-hexadecen.Surface analyses by coupling X-ray photoelectron spectroscopy(XPS)and secondary ion mass spectrometry(SIMS)have been carried out in the case of oleic acid with ta-C and a-C:H coatings.Results show that tribochemical reactions have occurred.OH groups terminate the ta-C surface whereas a-C:H is covered by a thin tribofilm and is terminated by oleic acid monolayers.The superlow regime in the case of ta-C is mainly attributed to the presence of the OH-termination.展开更多
This study compares micro-abrasive wear in two kinds of grey cast iron.Classical lamellar cast iron with fully pearlitic matrix(FGL1)and lamellar micro-alloyed cast iron with phosphorus and boron(FGL2)are used.FGL2 ha...This study compares micro-abrasive wear in two kinds of grey cast iron.Classical lamellar cast iron with fully pearlitic matrix(FGL1)and lamellar micro-alloyed cast iron with phosphorus and boron(FGL2)are used.FGL2 has a fully pearlitic matrix reinforced by the hard phosphorus eutectic phase.The microstructures of these two types of iron are mechanically characterized using nanoindentation tests.Vickers microindentation and microscratch tests are also performed on these iron samples.The indent and scratch images obtained via scanning electron microscopy were used to compare the scratch damage to the two kinds of iron.The friction coefficient is discussed in terms of applied load,indenter attack angle,and scratch damage.Nanoindentation tests show an improvement in graphite’s mechanical properties and an increase in the matrix hardness of the FGL2,relatively to FGL1.The same damage forms for both microindentation and microscratch testing were observed for the two iron samples.However,cracking of the hard phase is observed in FGL2.The results show that the scratching of the micro-alloyed iron(FGL2)leads to less matrix damage and to an extended microploughing wear mechanism.However,at low normal load,the reinforcement of the matrix can increase the friction coefficient.展开更多
In this study,we will model a light-weight building made of phase change materials(PCMs)to analyze the impact of the building volume,window orientation,and air infiltration on the PCM performance.This is done by calcu...In this study,we will model a light-weight building made of phase change materials(PCMs)to analyze the impact of the building volume,window orientation,and air infiltration on the PCM performance.This is done by calculating the energy savings attained by the use of PCM across all of Morocco.We’ll use the commercial Rubitherm panels with RT28HC as a phase change material in this work.Typically,the EnergyPlus simulation engine is chosen to perform the modeling.The impact of building volumes is also evaluated on the PCM activation for light-weight square buildings with different side lengths of 10 m,9 m,8 m,and 7 m.Also,we looked at how well the PCM performed in terms of energy savings and thermal regulation at different window orientation placements(south,north,west,and east)and various air infiltration rates(0.5,1,1.5,and 3 ACH).This paper’s primary objective is to determine the energy savings for the PCM-enhanced building in Morocco,as well as the effect of building volume,window orientation,and infiltration on the PCM capabilities for stabilizing the indoor room temperature.The results show good indoor temperature stabilization during the summer,for the light-weight square building with a south-facing window and no air infiltration.This configuration was able to achieve a total fluctuation reduction of 1303.3℃for the 10 m building in a semi-arid environment.Besides,a high energy savings percentage of 69.56%was achieved for the PCM-enhanced building with the south-oriented window and air infiltration of 0.5 air change per hour.展开更多
The objective of this study is to explore the physical and mechanical behaviour of concretes comprising four different ratios of recycled fine(RF),namely(5%,10%,15%and 20%)along with that of a reference concrete(Cref-...The objective of this study is to explore the physical and mechanical behaviour of concretes comprising four different ratios of recycled fine(RF),namely(5%,10%,15%and 20%)along with that of a reference concrete(Cref-0%),under three different heating-cooling cycles(200℃,400℃ and 600℃).The thermal properties of concrete during heating and cooling(20℃-600℃-20℃)were also investigated.It was determined that the physical properties(mass loss and ethanol porosity)of recycled concrete(RC)with 5%of recycled fine(RC-5%)were similar to those of Cref-0%.At ambient temperatures,the higher the ratio of recycled fines,the lower the residual compressive strength and residual elastic modulus of the recycled concrete.After thermal loading at 600℃,the residual mechanical properties of all types of concrete were equivalent,regardless of the content recycled fine.展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.52575091,U2341231)。
文摘With the swift advancement of industrial automation,robots have emerged as an essential component in emerging industries and high-end equipment,thereby propelling industrial production towards greater intelligence and efficiency.This paper reviews the pivotal technologies for motion planning of robots engaged in contact tasks within industrial automation contexts,encompassing environmental recognition,trajectory generation strategies,and sim-to-real transfer.Environmental recognition technology empowers robots to accurately discern objects and obstacles in their operational environment.Trajectory generation strategies formulate optimal motion paths based on environmental data and task specifications.Sim-to-real transfer is committed to effectively translating strategies from simulated environments to actual production,thereby diminishing the discrepancies between simulation and reality.The article also delves into the application of artificial intelligence in robot motion planning and how embodied intelligence models catalyze the evolution of robotics technology towards enhanced intelligence and automation.The paper concludes with a synthesis of the methodologies addressing this challenge and a perspective on the myriad challenges that warrant attention.
文摘The hysteretic behavior and nonlinearity of the equivalent material coefficient of macro fiber composites（MFC） under staircase input conditions are investigated using the Preisach model.Based on a database of first order reversal curves, formulas are derived to predict the hysteresis of strain output and nonlinearity of the equivalent piezoelectric coefficient of MFCs. Formulae are verified by comparing the predicted strains with the measured strains of three MFC specimens,which are driven by a random sequence of staircase voltage inputs. The coefficients obtained by the formulae and experimentation coincide. Further results indicate that the equivalent piezoelectric strain coefficient depends greatly on the value of drive voltage across the entire input range, and the coefficient is asymmetric across the negative and positive input ranges. Deflection testing of an MFC composite cantilever demonstrates the importance of taking the nonlinearity of the equivalent piezoelectric coefficient into consideration in the application of actuation.
基金supported by the LabEx CeLyA (Centre Lyonnais d’Acoustique, ANR-10-LABX-0060) of Universitéde Lyon。
文摘In this work,an enriched model describing the longitudinal wave propagation is established based on Mindlin’s Second Strain Gradient(SSG)theory,which can describe the heterogeneity caused by the micro-structure interactions in the frame of continuum mechanics.The governing equation and associated boundary conditions are derived based on Hamilton’s principle,then the dispersion relation of non-classical longitudinal wave together with the extra-waves appearing exclusively in SSG theory model are investigated.The investigations are based on the modal density,energy flow,and forced response of the rod.Wave transmission and reflection through planar interfaces based on the proposed model have been calculated.Finally,the results of the enriched model are well interpreted by comparing with the classical theory results,and some useful conclusions are derived on the SSG theory based model in the wave propagation characterization.
基金funding from the HORIZON-EIC-2021-PATHFINDEROPEN-0 N.101046693,SSLiP project,funded by the European Union.
文摘Hypericin(C30H16O8)is a naturally occurring substance,an anthraquinone derived from St.John’s wort,possessing outstanding antiviral,antitumor,antibacterial,and antioxidant properties.Today,hypericin is primarily used in medicinal applications.It is a small,flat organic molecule with a graphene-like core surrounded by oxidized functions,suggesting it could act as a graphene precursor in tribological contacts.Therefore,we investigated the lubrication properties of hypericin as an additive in glycerol,used as a base oil.It is well established that glycerol is superlubricious under full and thin film elastohydrodynamic(EHD)lubrication regimes but generally fails with steel under more severe conditions(mixed and boundary regimes).We studied the effect of hypericin added to glycerol for steel-on-steel and steel-on-silicon friction pairs.For the steel-on-steel configuration,results show that hypericin is a strong anti-wear additive due to its antioxidant properties that scavenge OH radicals.Moreover,hypericin is also an efficient friction-reducing agent,providing a steady state and robust ultralow friction coefficient(0.02–0.03).Thus,it outperforms most traditional additive formulations under the same conditions,although it does not achieve superlubricity(coefficient of friction(CoF)<0.01)under more severe conditions.For steel-on-silicon,hypericin significantly extends the superlubricity regime of glycerol to lambda ratios well below unity(low sliding speeds).The mechanism of superlubricity is attributed to the friction-induced formation of graphene layers from hypericin molecules,smoothing friction surfaces,and operating a hybrid liquid–solid superlubricious system.
文摘While the implementation of sustainable urban planning has proven to be one of the primary goals to reduce the climate change impact,the rapid adoption of nearly Zero Energy Buildings(nZEB)concept in the building sector is inevitable to reach that objective.Following this trend,this article focuses on the implementation of a parametric digital workflow to evaluate the energy performance of a nearly zero energy high-rise 23-storey office building in the climatic and urban contexts of Casablanca at the early design stage.In the scope of this study,Grasshopper-based digital workflow permits to investigate the impact of 147 parametric building designs,which are generated by varying the building’s shape factor and orientation on thermal cooling and heating demand and global solar energy production.The outcomes of this holistic methodology highlight the design trade-offs between energy efficiency strategies and energy performance of building-integrated photovoltaic(BIPV)and photovoltaic(PV)systems,aiming to reach optimized nZEB.Moreover,the results of the study suggest that it is possible to reach an annual load match equivalent to 29.68%.The findings also underscore the significant role of the BIPV systems in shifting towards the goal of net zero energy,accounting for up to 64.43%of the total solar energy output and contributing in total up to 17.62%to the yearly self-sufficiency.In addition,the energy balance evaluation,when assessed on an hourly basis,reveals that the BIPV system significantly improves the daily load cover factor,achieving a value of 12.45%,and increases up to 20.62%when considering also the rooftop PV,particularly during spring season.Finally,the capacity credit factor is improved by up to 31.27%,which is a significant share of grid connection reduction compared to the same building relying totally on the grid for its energy needs.
文摘Aluminium alloys are commonly used as lightweight materials in the automotive industry.This non-ferrous family of metallic alloys offers a high versatility of properties and designs.To reduce weight and improve safety,high strength-to-weight ratio alloys(e.g.6XXX and 7XXX),are increasingly implemented in vehicles.However,these alloys exhibit low formability and experience considerable springback during cold forming,and are therefore hot formed.During forming,severe adhesion(i.e.galling)of aluminium onto the die surface takes place.This phenomenon has a detrimental effect on the surface properties,geometrical tolerances of the formed parts and maintenance of the dies.The effect of surface engineering as well as lubricant chemistry on galling has not been sufficiently investigated.Diamond-like carbon(DLC)and CrN physical vapour deposition(PVD)coated steel have been studied to reduce aluminium transfer.However,the interaction between lubricants and PVD coatings during hot forming of aluminium alloys is not yet fully understood.The present study thus aims to characterise the high temperature tribological behaviour of selected PVD coatings and lubricants during sliding against aluminium alloy.The objectives are to first select promising lubricant-coating combinations and then to study their tribological response in a high-temperature reciprocating friction and wear tester.Dry and lubricated tests were carried out at 300℃ using a commercial polymer lubricant.Tests using DLC,CrN,CrTiN,and CrAIN coated tool steel were compared to uncoated tool steel reference tests.The initial and worn test specimen surfaces were analysed with a 3-dimensional(3D)optical profiler,scanning electron microscope(SEM)and energy dispersive X-ray spectroscope(EDS)as to understand the wear mechanisms.The results showed formation of tribolayers in the contact zone,reducing both friction and wear.The stability of these layers highly depends on both the coatings'roughness and chemical affinity towards aluminium.The DLC and CrN coatings combined with the polymer lubricant were the most effective in reducing aluminium transfer.
文摘Friction tests have been carried out on bearing steel friction pairs coated with a-C:H and ta-C under lubricated conditions with 1-hexadecene and pure oleic acid,respectively.Main results show that ta-C leads to the super-low regime with oleic acid(friction coefficient below 0.01)and that a-C:H is quite well lubricated by 1-hexadecen.Surface analyses by coupling X-ray photoelectron spectroscopy(XPS)and secondary ion mass spectrometry(SIMS)have been carried out in the case of oleic acid with ta-C and a-C:H coatings.Results show that tribochemical reactions have occurred.OH groups terminate the ta-C surface whereas a-C:H is covered by a thin tribofilm and is terminated by oleic acid monolayers.The superlow regime in the case of ta-C is mainly attributed to the presence of the OH-termination.
文摘This study compares micro-abrasive wear in two kinds of grey cast iron.Classical lamellar cast iron with fully pearlitic matrix(FGL1)and lamellar micro-alloyed cast iron with phosphorus and boron(FGL2)are used.FGL2 has a fully pearlitic matrix reinforced by the hard phosphorus eutectic phase.The microstructures of these two types of iron are mechanically characterized using nanoindentation tests.Vickers microindentation and microscratch tests are also performed on these iron samples.The indent and scratch images obtained via scanning electron microscopy were used to compare the scratch damage to the two kinds of iron.The friction coefficient is discussed in terms of applied load,indenter attack angle,and scratch damage.Nanoindentation tests show an improvement in graphite’s mechanical properties and an increase in the matrix hardness of the FGL2,relatively to FGL1.The same damage forms for both microindentation and microscratch testing were observed for the two iron samples.However,cracking of the hard phase is observed in FGL2.The results show that the scratching of the micro-alloyed iron(FGL2)leads to less matrix damage and to an extended microploughing wear mechanism.However,at low normal load,the reinforcement of the matrix can increase the friction coefficient.
文摘In this study,we will model a light-weight building made of phase change materials(PCMs)to analyze the impact of the building volume,window orientation,and air infiltration on the PCM performance.This is done by calculating the energy savings attained by the use of PCM across all of Morocco.We’ll use the commercial Rubitherm panels with RT28HC as a phase change material in this work.Typically,the EnergyPlus simulation engine is chosen to perform the modeling.The impact of building volumes is also evaluated on the PCM activation for light-weight square buildings with different side lengths of 10 m,9 m,8 m,and 7 m.Also,we looked at how well the PCM performed in terms of energy savings and thermal regulation at different window orientation placements(south,north,west,and east)and various air infiltration rates(0.5,1,1.5,and 3 ACH).This paper’s primary objective is to determine the energy savings for the PCM-enhanced building in Morocco,as well as the effect of building volume,window orientation,and infiltration on the PCM capabilities for stabilizing the indoor room temperature.The results show good indoor temperature stabilization during the summer,for the light-weight square building with a south-facing window and no air infiltration.This configuration was able to achieve a total fluctuation reduction of 1303.3℃for the 10 m building in a semi-arid environment.Besides,a high energy savings percentage of 69.56%was achieved for the PCM-enhanced building with the south-oriented window and air infiltration of 0.5 air change per hour.
基金funded by Pack Ambition International(PAI)of the Rhône-Alpes and Auvergne Region,FRANCE.
文摘The objective of this study is to explore the physical and mechanical behaviour of concretes comprising four different ratios of recycled fine(RF),namely(5%,10%,15%and 20%)along with that of a reference concrete(Cref-0%),under three different heating-cooling cycles(200℃,400℃ and 600℃).The thermal properties of concrete during heating and cooling(20℃-600℃-20℃)were also investigated.It was determined that the physical properties(mass loss and ethanol porosity)of recycled concrete(RC)with 5%of recycled fine(RC-5%)were similar to those of Cref-0%.At ambient temperatures,the higher the ratio of recycled fines,the lower the residual compressive strength and residual elastic modulus of the recycled concrete.After thermal loading at 600℃,the residual mechanical properties of all types of concrete were equivalent,regardless of the content recycled fine.
