The emergence of mechanically one-way materials presents an exciting opportunity for materials science and engineering. These substances exhibit unique nonreciprocal mechanical responses, enabling them to selectively ...The emergence of mechanically one-way materials presents an exciting opportunity for materials science and engineering. These substances exhibit unique nonreciprocal mechanical responses, enabling them to selectively channel mechanical energy and facilitate directed sound propagation, controlled mass transport, and concentration of mechanical energy amidst random motion. This article explores the fundamentals of mechanically one-way materials, their potential applications across various industries, and the economic and environmental considerations related to their production and use.展开更多
Brittle materials are widely used for producing important components in the industry of optics,optoelectronics,and semiconductors.Ultraprecision machining of brittle materials with high surface quality and surface int...Brittle materials are widely used for producing important components in the industry of optics,optoelectronics,and semiconductors.Ultraprecision machining of brittle materials with high surface quality and surface integrity helps improve the functional performance and lifespan of the components.According to their hardness,brittle materials can be roughly divided into hard-brittle and soft-brittle.Although there have been some literature reviews for ultraprecision machining of hard-brittle materials,up to date,very few review papers are available that focus on the processing of soft-brittle materials.Due to the‘soft’and‘brittle’properties,this group of materials has unique machining characteristics.This paper presents a comprehensive overview of recent advances in ultraprecision machining of soft-brittle materials.Critical aspects of machining mechanisms,such as chip formation,surface topography,and subsurface damage for different machining methods,including diamond turning,micro end milling,ultraprecision grinding,and micro/nano burnishing,are compared in terms of tool-workpiece interaction.The effects of tool geometries on the machining characteristics of soft-brittle materials are systematically analyzed,and dominating factors are sorted out.Problems and challenges in the engineering applications are identified,and solutions/guidelines for future R&D are provided.展开更多
This paper proposed an innovative teaching approach based on finite element technique(FET)to improve the understanding of material mechanics.A teaching experiment was conducted using pure bending deformation of a beam...This paper proposed an innovative teaching approach based on finite element technique(FET)to improve the understanding of material mechanics.A teaching experiment was conducted using pure bending deformation of a beam as an example,and the deformation and stress distribution of the beam were analyzed using FET.The results showed that using color stress nephograms and color U nephograms can improve students’learning outcomes in mechanics classroom.The high levels of satisfaction and interest in incorporating new techniques into the classroom suggest that there is a need to explore and develop innovative teaching methods in mechanics and related fields.This approach may inspire educators to develop more effective ways of teaching material mechanics,and our research can contribute to the advancement of mechanics education.展开更多
Diamond, cubic boron nitride(c-BN), silicon(Si), and germanium(Ge), as examples of typical strong covalent materials, have been extensively investigated in recent decades, owing to their fundamental importance in mate...Diamond, cubic boron nitride(c-BN), silicon(Si), and germanium(Ge), as examples of typical strong covalent materials, have been extensively investigated in recent decades, owing to their fundamental importance in material science and industry. However, an in-depth analysis of the character of these materials' mechanical behaviors under harsh service environments, such as high pressure, has yet to be conducted. Based on several mechanical criteria, the effect of pressure on the mechanical properties of these materials is comprehensively investigated.It is demonstrated that, with respect to their intrinsic brittleness/ductile nature, all these materials exhibit ubiquitous pressure-enhanced ductility. By analyzing the strength variation under uniform deformation, together with the corresponding electronic structures, we reveal for the first time that the pressure-induced mechanical softening/weakening exhibits distinct characteristics between diamond and c-BN, owing to the differences in their abnormal charge-depletion evolution under applied strain, whereas a monotonous weakening phenomenon is observed in Si and Ge. Further investigation into dislocation-mediated plastic resistance indicates that the pressure-induced shuffle-set plane softening in diamond(c-BN), and weakening in Si(Ge), can be attributed to the reduction of antibonding states below the Fermi level, and an enhanced metallization, corresponding to the weakening of the bonds around the slipped plane with increasing pressure, respectively. These findings not only reveal the physical mechanism of pressure-induced softening/weakening in covalent materials, but also highlights the necessity of exploring strain-tunable electronic structures to emphasize the mechanical response in such covalent materials.展开更多
Material Mechanics is an important subject for science and engineering students in vocational colleges.However,its teaching effect has not been up to par for a long time.In order to improve the teaching quality,this p...Material Mechanics is an important subject for science and engineering students in vocational colleges.However,its teaching effect has not been up to par for a long time.In order to improve the teaching quality,this paper discusses four problems existing in the teaching of Material Mechanics and proposes corresponding countermeasures.Rich animations and Mises stress nephograms can be formed using new techniques,such as finite element simulation,making it easier for students to understand abstract concepts.The introduction of engineering-related cases can enhance students’interest,and students’hands-on skills and innovation can be improved with open mechanics laboratory.The suggestions are worthy of reference and should be flexibly applied to the teaching of Material Mechanics.展开更多
Lung diseases associated with alveoli,such as acute respiratory distress syndrome,have posed a long-term threat to human health.However,an in vitro model capable of simulating different deformations of the alveoli and...Lung diseases associated with alveoli,such as acute respiratory distress syndrome,have posed a long-term threat to human health.However,an in vitro model capable of simulating different deformations of the alveoli and a suitable material for mimicking basement membrane are currently lacking.Here,we present an innovative biomimetic controllable strain membrane(BCSM)at an air–liquid interface(ALI)to reconstruct alveolar respiration.The BCSM consists of a high-precision three-dimensional printing melt-electrowritten polycaprolactone(PCL)mesh,coated with a hydrogel substrate—to simulate the important functions(such as stiffness,porosity,wettability,and ALI)of alveolar microenvironments,and seeded pulmonary epithelial cells and vascular endothelial cells on either side,respectively.Inspired by papercutting,the BCSM was fabricated in the plane while it operated in three dimensions.A series of the topological structure of the BCSM was designed to control various local-area strain,mimicking alveolar varied deformation.Lopinavir/ritonavir could reduce Lamin A expression under over-stretch condition,which might be effective in preventing ventilator-induced lung injury.The biomimetic lung-unit model with BCSM has broader application prospects in alveoli-related research in the future,such as in drug toxicology and metabolism.展开更多
Glass-ceramics have many excellent properties and are widely used in various fields. During the grinding process,the workpiece surface is typically subject to material removal by grit of incremental heights, which has...Glass-ceramics have many excellent properties and are widely used in various fields. During the grinding process,the workpiece surface is typically subject to material removal by grit of incremental heights, which has rarely been the focus of research. As such, it is necessary to study the material removal mechanism of glass-ceramics under consecutive incremental loading, which more closely reflects the actual grinding process. In this paper,to analyze the plastic deformation and residual stress of lithium aluminosilicate(LAS) glass-ceramics, a finite element model is established based on the Drucker–Prager yield criterion for ductile regimes. A nano-scratch test was also conducted and the test results show that both the residual depth and residual stress increase with an increase in the number of increments, and that consecutive incremental loading promotes the plastic deformation of glass-ceramics and increases the residual stress of the material in the ductile-regime process. These findings provide guidance for achieving higher dimensional accuracy in the actual grinding of glass-ceramics parts.展开更多
Single crystal silicon carbide(SiC)is widely used for optoelectronics applications.Due to the anisotropic characteristics of single crystal materials,the C face and Si face of single crystal SiC have different physica...Single crystal silicon carbide(SiC)is widely used for optoelectronics applications.Due to the anisotropic characteristics of single crystal materials,the C face and Si face of single crystal SiC have different physical properties,which may fit for particular application purposes.This paper presents an investigation of the material removal and associated subsurface defects in a set of scratching tests on the C face and Si face of 4H-SiC and 6H-SiC materials using molecular dynamics simulations.The investigation reveals that the sample material deformation consists of plastic,amorphous transformations and dislocation slips that may be prone to brittle split.The results showed that the material removal at the C face is more effective with less amorphous deformation than that at the Si face.Such a phenomenon in scratching relates to the dislocations on the basal plane(0001)of the SiC crystal.Subsurface defects were reduced by applying scratching cut depths equal to integer multiples of a half molecular lattice thickness,which formed a foundation for selecting machining control parameters for the best surface quality.展开更多
Electrochemical jet machining(EJM)encounters significant challenges in the microstructuring of chemically inert and passivating materials because an oxide layer is easily formed on the material surface,preventing the ...Electrochemical jet machining(EJM)encounters significant challenges in the microstructuring of chemically inert and passivating materials because an oxide layer is easily formed on the material surface,preventing the progress of electrochemical dissolution.This research demonstrates for the first time a jet-electrolytic plasma micromachining(Jet-EPM)method to overcome this problem.Specifically,an electrolytic plasma is intentionally induced at the jet-material contact area by applying a potential high enough to surmount the surface boundary layer(such as a passive film or gas bubble)and enable material removal.Compared to traditional EJM,introducing plasma in the electrochemical jet system leads to considerable differences in machining performance due to the inclusion of plasma reactions.In this work,the implementation of Jet-EPM for fabricating microstructures in the semiconductor material 4H-SiC is demonstrated,and the machining principle and characteristics of Jet-EPM,including critical parameters and process windows,are comprehensively investigated.Theoretical modeling and experiments have elucidated the mechanisms of plasma ignition/evolution and the corresponding material removal,showing the strong potential of Jet-EPM for micromachining chemically resistant materials.The present study considerably augments the range of materials available for processing by the electrochemical jet technique.展开更多
The hot or cold processing would induce the change and the inhomogeneous of the material mechanical properties in the local processing region of the structure,and it is difficult to obtain the specific mechanical prop...The hot or cold processing would induce the change and the inhomogeneous of the material mechanical properties in the local processing region of the structure,and it is difficult to obtain the specific mechanical properties in these regions by using the traditional material tensile test.To accurately get actual material mechanical properties in the local region of structure,a micro-indentation test system incorporated by an electronic universal material test device has been established.An indenter displacement sensor and a group of special micro-indenter assemblies are estab-lished.A numerical indentation inversion analysis method by using ABAQUS software is also proposed in this study.Based on the above test system and analysis platform,an approach to obtaining material mechanical properties in the local region of structures is proposed and established.The ball indentation test is performed and combined with the energy method by using various changed mechanical properties of 316L austenitic stainless steel under differ-ent elongations.The investigated results indicate that the material mechanical properties and the micro-indentation morphological changes have evidently relevance.Compared with the tensile test results,the deviations of material mechanical parameters,such as hardness H,the hardening exponent n,the yield strength σy and others are within 5%obtained through the indentation test and the finite element analysis.It provides an effective and convenient method for obtaining the actual material mechanical properties in the local processing region of the structure.展开更多
Objective:Use network pharmacology to explore the anti-COVID-19 mechanism of Huashi Baidu Recipe,supplemented by molecular docking verification.Methods:Thorugh databases such as TCMSP,GeneCard,String,and software such...Objective:Use network pharmacology to explore the anti-COVID-19 mechanism of Huashi Baidu Recipe,supplemented by molecular docking verification.Methods:Thorugh databases such as TCMSP,GeneCard,String,and software such as Cytoscape,AutoDockVina,network relationships was established,and the binding ability of active ingredients and targets is calculated through molecular docking,and biological function enrichment analysis was conducted.Result:The ingredients in Huashi Baidu Recipe that had strong affinity with SARS-CoV-23CL hydrolase(3CLpro)and angiotensin converting enzyme 2(ACE2)receptors include Quercetin,Baicalein,Astragaloside IV,Wogonin and other ingredients;25 active ingredients which obtained by screening had strong affinity with targets such as IL6,IL1B,NOS2 and CCL2.The biological function enrichment analysis mainly focused on Th17,Th1 and Th2 cell differentiation,NF-κB,MAPK,TNF,IL-17signaling pathway,etc.Conclusion:The active ingredients of Huashi Baidu Recipe may inhibit the infection and replication of SARS-CoV-2 virus,regulate RAS system’balance,inhibit excessive immune inflammatory response,and prevent inflammatory storm from appearing to fight COVID-19.展开更多
Human skin perceives external environmental stimulus by the synergies between the subcutaneous tactile corpuscles.Soft electronics with multiple sensing capabilities by mimicking the function of human skin are of sign...Human skin perceives external environmental stimulus by the synergies between the subcutaneous tactile corpuscles.Soft electronics with multiple sensing capabilities by mimicking the function of human skin are of significance in health monitoring and artificial sensation.The last decade has witnessed unprecedented development and convergence between multimodal tactile sensing devices and soft bioelectronics.Despite these advances,traditional flexible electronics achieve multimodal tactile sensing for pressure,strain,temperature,and humidity by integrating monomodal sensing devices together.This strategy results in high energy consumption,limited integration,and complex manufacturing process.Various multimodal sensors and crosstalk-free sensing mechanisms have been proposed to bridge the gap between natural sensory system and artificial perceptual system.In this review,we provide a comprehensive summary of tactile sensing mechanism,integration design principles,signal-decoupling strategies,and current applications for multimodal tactile perception.Finally,we highlight the current challenges and present the future perspectives to promote the development of multimodal tactile perception.展开更多
Presently,the service performance of new-generation high-tech equipment is directly affected by the manufacturing quality of complex thin-walled components.A high-efficiency and quality manufacturing of these complex ...Presently,the service performance of new-generation high-tech equipment is directly affected by the manufacturing quality of complex thin-walled components.A high-efficiency and quality manufacturing of these complex thin-walled components creates a bottleneck that needs to be solved urgently in machinery manufacturing.To address this problem,the collaborative manufacturing of structure shape and surface integrity has emerged as a new process that can shorten processing cycles,improve machining qualities,and reduce costs.This paper summarises the research status on the material removal mechanism,precision control of structure shape,machined surface integrity control and intelligent process control technology of complex thin-walled components.Numerous solutions and technical approaches are then put forward to solve the critical problems in the high-performance manufacturing of complex thin-wall components.The development status,challenge and tendency of collaborative manufacturing technologies in the high-efficiency and quality manufacturing of complex thin-wall components is also discussed.展开更多
The material loss caused by bubble collapse during the micro-nano bubbles auxiliary chemical mechanical polishing(CMP)process cannot be ignored.In this study,the material removal mechanism of cavitation in the polishi...The material loss caused by bubble collapse during the micro-nano bubbles auxiliary chemical mechanical polishing(CMP)process cannot be ignored.In this study,the material removal mechanism of cavitation in the polishing process was investigated in detail.Based on the mixed lubrication or thin film lubrication,bubble-wafer plastic deformation,spherical indentation theory,Johnson-Cook(J-C)constitutive model,and the assumption of periodic distribution of pad asperities,a new model suitable for micro-nano bubble auxiliary material removal in CMP was developed.The model integrates many parameters,including the reactant concentration,wafer hardness,polishing pad roughness,strain hardening,strain rate,micro-jet radius,and bubble radius.The model reflects the influence of active bubbles on material removal.A new and simple chemical reaction method was used to form a controllable number of micro-nano bubbles during the polishing process to assist in polishing silicon oxide wafers.The experimental results show that micro-nano bubbles can greatly increase the material removal rate(MRR)by about 400%and result in a lower surface roughness of 0.17 nm.The experimental results are consistent with the established model.In the process of verifying the model,a better understanding of the material removal mechanism involved in micro-nano bubbles in CMP was obtained.展开更多
This paper reviews recent developments of the soft abrasive flow finishing(SAF)method in constraint space.The multiphase fluid dynamics modeling,material removal mechanism,auxiliary strengthening finishing techniques,...This paper reviews recent developments of the soft abrasive flow finishing(SAF)method in constraint space.The multiphase fluid dynamics modeling,material removal mechanism,auxiliary strengthening finishing techniques,and observation of surface impact effects by abrasive particles and cavitation bubbles are presented in brief.Development prospects and challenges are given for four aspects:thin-walled curved surfaces,biomedical functions,electronic information,and precise optical components.展开更多
Carbon fiber reinforced silicon carbide(C_(f)/SiC)composites are widely used in aerospace for their excellent mechanical properties.However,the quality of the machined surface is poor and unpredictable due to the mate...Carbon fiber reinforced silicon carbide(C_(f)/SiC)composites are widely used in aerospace for their excellent mechanical properties.However,the quality of the machined surface is poor and unpredictable due to the material heterogeneity induced by complex removal mechanism.To clarify the effects of fiber orientation on the grinding characteristics and removal mechanism,single grit scratch experiments under different fiber orientations are conducted and a three-phase numerical modelling method for 2.5D C_(f)/SiC composites is proposed.Three fiber cutting modes i.e.,transverse,normal and longitudinal,are defined by fiber orientation and three machining directions i.e.,MA(longitudinal and normal),MB(longitudinal and transverse)and MC(normal and transverse),are selected to investigate the effect of fiber orientation on grinding force and micro-morphology.Besides,a three-phase cutting model of 2.5D C_(f)/SiC composites considering the mechanical properties of the matrix,fiber and interface is developed.Corresponding simulations are performed to reveal the micro-mechanism of crack initiation and extension as well as the material removal mechanism under different fiber orientations.The results indicate that the scratching forces fluctuate periodically,and the order of mean forces is MA>MC>MB.Cracks tend to grow along the fiber axis,which results in the largest damage layer for transverse fibers and the smallest for longitudinal fibers.The removal modes of transverse fibers are worn,fracture and peel-off,in which normal fibers are pullout and outcrop and the longitudinal fibers are worn and push-off.Under the stable cutting condition,the change of contact area between fiber and grit leads to different removal modes of fiber in the same cutting mode,and the increase of contact area results in the aggravation of fiber fracture.展开更多
Continuous fiber reinforced SiC ceramic matrix composites(FRCMCs-SiC)are currently the preferred material for hot section components,safety–critical components and braking components(in the aerospace,energy,transport...Continuous fiber reinforced SiC ceramic matrix composites(FRCMCs-SiC)are currently the preferred material for hot section components,safety–critical components and braking components(in the aerospace,energy,transportation)with high value,and have triggered the demand for machining.However,the high brittleness,anisotropy,and heterogeneity of materials bring great challenges to machining,due to high mechanical and thermal loads,severe tool wear,and poor machining quality.With the increasing demand of FRCMCs-SiC parts,high-quality and high-efficient machining has become a hot issue.This review paper provides a detailed literature survey on the machining of FRCMCs-SiC.The material removal mechanism,defect form,and interfacial mechanical properties of FRCMCs-SiC were summarized.The machining processes of FRCMCs-SiC were introduced,and their respective advantages and disadvantages were compared.Given the low machinability(high hardness,high brittleness,anisotropy,and heterogeneity)of FRCMCs-SiC,preliminary experiments have proved that ultrasonic-assisted machining and laser-assisted machining have shown unique advantages in reducing force and tool wear,improving machining quality and machining efficiency.The machined surface integrity was discussed,the influence of process parameters on the machined surface quality was analyzed,and the machining defects of FRCMCs-SiC were summarized.But for FRCMCs-SiC,the existing quantitative evaluation of the machined surface integrity was weak and unsystematic.展开更多
Fiber-reinforced composites have become the preferred material in the fields of aviation and aerospace because of their high-strength performance in unit weight.The composite components are manufactured by near netsha...Fiber-reinforced composites have become the preferred material in the fields of aviation and aerospace because of their high-strength performance in unit weight.The composite components are manufactured by near netshape and only require finishing operations to achieve final dimensional and assembly tolerances.Milling and grinding arise as the preferred choices because of their precision processing.Nevertheless,given their laminated,anisotropic,and heterogeneous nature,these materials are considered difficult-to-machine.As undesirable results and challenging breakthroughs,the surface damage and integrity of these materials is a research hotspot with important engineering significance.This review summarizes an up-to-date progress of the damage formation mechanisms and suppression strategies in milling and grinding for the fiber-reinforced composites reported in the literature.First,the formation mechanisms of milling damage,including delamination,burr,and tear,are analyzed.Second,the grinding mechanisms,covering material removal mechanism,thermal mechanical behavior,surface integrity,and damage,are discussed.Third,suppression strategies are reviewed systematically from the aspects of advanced cutting tools and technologies,including ultrasonic vibration-assisted machining,cryogenic cooling,minimum quantity lubrication(MQL),and tool optimization design.Ultrasonic vibration shows the greatest advantage of restraining machining force,which can be reduced by approximately 60%compared with conventional machining.Cryogenic cooling is the most effective method to reduce temperature with a maximum reduction of approximately 60%.MQL shows its advantages in terms of reducing friction coefficient,force,temperature,and tool wear.Finally,research gaps and future exploration directions are prospected,giving researchers opportunity to deepen specific aspects and explore new area for achieving high precision surface machining of fiber-reinforced composites.展开更多
Current three-body abrasive wear theories are based on a macroscale abrasive indentation process,and these theories claim that material wear cannot be achieved without damaging the hard mating surface.In this study,th...Current three-body abrasive wear theories are based on a macroscale abrasive indentation process,and these theories claim that material wear cannot be achieved without damaging the hard mating surface.In this study,the process of three-body nano-abrasive wear of a system including a single crystalline silicon substrate,an amorphous silica cluster,and a polyurethane pad,based on a chemical mechanical polishing(CMP)process,is investigated via molecular dynamics simulations.The cluster slid in a suspended state in smooth regions and underwent rolling impact in the asperity regions of the silicon surface,realizing non-damaging monoatomic material removal.This proves that indentation-plowing is not necessary when performing CMP material removal.Therefore,a non-indentation rolling-sliding adhesion theory for three-body nano-abrasive wear between ultrasoft/hard mating surfaces is proposed.This wear theory not only unifies current mainstream CMP material removal theories,but also clarifies that monoatomic material wear without damage can be realized when the indentation depth is less than zero,thereby perfecting the relationship between material wear and surface damage.These results provide new understanding regarding the CMP microscopic material removal mechanism as well as new research avenues for three-body abrasive wear theory at the monoatomic scale.展开更多
Magnetorheological finishing(MRF)technology is widely used in the fabrication of high-precision optical elements.The material removal mechanism of MRF has not been fully understood because MRF technology involves the ...Magnetorheological finishing(MRF)technology is widely used in the fabrication of high-precision optical elements.The material removal mechanism of MRF has not been fully understood because MRF technology involves the integration of electromagnetics,contact mechanics,and materials science.In this study,the rheological properties of the MR polishing fluid in oscillation model have been investigated.We propose that the shear-thinned MR polishing fluid over the polishing area should be considered a dense granular flow,based on which a new contact model of MRF over the polishing area has been constructed.Removal function and processing force test experiments were conducted under different working gaps.The normal pressure and effective friction equations over the polishing area were built based on the continuous medium and dense granular flow theories.Then,a novel MRF material removal model was established.A comparison of the results of the theoretical model with actual polishing results demonstrated the accuracy of the established model.The novel model proposed herein reveals the generation mechanism of shear force over a polished workpiece and realizes effective decoupling of the main processing parameters that influence the material removal of MRF.The results of this study will provide new and effective theoretical guidance for the process optimization and technology improvement of MRF.展开更多
文摘The emergence of mechanically one-way materials presents an exciting opportunity for materials science and engineering. These substances exhibit unique nonreciprocal mechanical responses, enabling them to selectively channel mechanical energy and facilitate directed sound propagation, controlled mass transport, and concentration of mechanical energy amidst random motion. This article explores the fundamentals of mechanically one-way materials, their potential applications across various industries, and the economic and environmental considerations related to their production and use.
文摘Brittle materials are widely used for producing important components in the industry of optics,optoelectronics,and semiconductors.Ultraprecision machining of brittle materials with high surface quality and surface integrity helps improve the functional performance and lifespan of the components.According to their hardness,brittle materials can be roughly divided into hard-brittle and soft-brittle.Although there have been some literature reviews for ultraprecision machining of hard-brittle materials,up to date,very few review papers are available that focus on the processing of soft-brittle materials.Due to the‘soft’and‘brittle’properties,this group of materials has unique machining characteristics.This paper presents a comprehensive overview of recent advances in ultraprecision machining of soft-brittle materials.Critical aspects of machining mechanisms,such as chip formation,surface topography,and subsurface damage for different machining methods,including diamond turning,micro end milling,ultraprecision grinding,and micro/nano burnishing,are compared in terms of tool-workpiece interaction.The effects of tool geometries on the machining characteristics of soft-brittle materials are systematically analyzed,and dominating factors are sorted out.Problems and challenges in the engineering applications are identified,and solutions/guidelines for future R&D are provided.
文摘This paper proposed an innovative teaching approach based on finite element technique(FET)to improve the understanding of material mechanics.A teaching experiment was conducted using pure bending deformation of a beam as an example,and the deformation and stress distribution of the beam were analyzed using FET.The results showed that using color stress nephograms and color U nephograms can improve students’learning outcomes in mechanics classroom.The high levels of satisfaction and interest in incorporating new techniques into the classroom suggest that there is a need to explore and develop innovative teaching methods in mechanics and related fields.This approach may inspire educators to develop more effective ways of teaching material mechanics,and our research can contribute to the advancement of mechanics education.
基金Supported by the National Natural Science Foundation of China (Grant No.51672015)the National Key Research and Development Program of China (Grant Nos.2016YFC1102500 and 2017YFB0702100)+3 种基金the 111 Project (Grant No.B17002)and the Fundamental Research Funds for the Central Universitiessupported by the European Regional Development Fund in the IT4Innovations National Supercomputing Center—Path to Exascale Project (Grant No.CZ.02.1.01/0.0/0.0/16 013/0001791)within the Operational Programme for Research,Development and Education,and by the Large Infrastructures for Research,Experimental Development,and Innovation Project (Grant No.e-INFRA CZ-LM2018140) by the Ministry of Education,Youth,Sport of the Czech Republic。
文摘Diamond, cubic boron nitride(c-BN), silicon(Si), and germanium(Ge), as examples of typical strong covalent materials, have been extensively investigated in recent decades, owing to their fundamental importance in material science and industry. However, an in-depth analysis of the character of these materials' mechanical behaviors under harsh service environments, such as high pressure, has yet to be conducted. Based on several mechanical criteria, the effect of pressure on the mechanical properties of these materials is comprehensively investigated.It is demonstrated that, with respect to their intrinsic brittleness/ductile nature, all these materials exhibit ubiquitous pressure-enhanced ductility. By analyzing the strength variation under uniform deformation, together with the corresponding electronic structures, we reveal for the first time that the pressure-induced mechanical softening/weakening exhibits distinct characteristics between diamond and c-BN, owing to the differences in their abnormal charge-depletion evolution under applied strain, whereas a monotonous weakening phenomenon is observed in Si and Ge. Further investigation into dislocation-mediated plastic resistance indicates that the pressure-induced shuffle-set plane softening in diamond(c-BN), and weakening in Si(Ge), can be attributed to the reduction of antibonding states below the Fermi level, and an enhanced metallization, corresponding to the weakening of the bonds around the slipped plane with increasing pressure, respectively. These findings not only reveal the physical mechanism of pressure-induced softening/weakening in covalent materials, but also highlights the necessity of exploring strain-tunable electronic structures to emphasize the mechanical response in such covalent materials.
基金The Project of Beijing Office for Education Sciences Planning and the Project of China Vocational Education Association“A Case Study on the Construction of Pilot Test Base of Technical Skill Innovation Service Platform in Higher Vocational Colleges”(Project Number:CGDB21208)+1 种基金“Research on the Key Elements of the Construction of Vocational Education and Training System in Higher Vocational Colleges”(Project Number:CCDB2020135)“Research on the Role of Technical Skills Competition in Promoting Huang Yanpei’s View on the Quality of Vocational Education”(Project Number:ZJS2022YB024).
文摘Material Mechanics is an important subject for science and engineering students in vocational colleges.However,its teaching effect has not been up to par for a long time.In order to improve the teaching quality,this paper discusses four problems existing in the teaching of Material Mechanics and proposes corresponding countermeasures.Rich animations and Mises stress nephograms can be formed using new techniques,such as finite element simulation,making it easier for students to understand abstract concepts.The introduction of engineering-related cases can enhance students’interest,and students’hands-on skills and innovation can be improved with open mechanics laboratory.The suggestions are worthy of reference and should be flexibly applied to the teaching of Material Mechanics.
基金sponsored by the National Key Research and Development Program of China(2021YFC2501800)the National Natural Science Foundation of China(No.U1909218)the Science Fund for Creative Research Groups of the National Natural Science Foundation of China(No.T2121004).
文摘Lung diseases associated with alveoli,such as acute respiratory distress syndrome,have posed a long-term threat to human health.However,an in vitro model capable of simulating different deformations of the alveoli and a suitable material for mimicking basement membrane are currently lacking.Here,we present an innovative biomimetic controllable strain membrane(BCSM)at an air–liquid interface(ALI)to reconstruct alveolar respiration.The BCSM consists of a high-precision three-dimensional printing melt-electrowritten polycaprolactone(PCL)mesh,coated with a hydrogel substrate—to simulate the important functions(such as stiffness,porosity,wettability,and ALI)of alveolar microenvironments,and seeded pulmonary epithelial cells and vascular endothelial cells on either side,respectively.Inspired by papercutting,the BCSM was fabricated in the plane while it operated in three dimensions.A series of the topological structure of the BCSM was designed to control various local-area strain,mimicking alveolar varied deformation.Lopinavir/ritonavir could reduce Lamin A expression under over-stretch condition,which might be effective in preventing ventilator-induced lung injury.The biomimetic lung-unit model with BCSM has broader application prospects in alveoli-related research in the future,such as in drug toxicology and metabolism.
基金supported by the National Key Research and Development Program of China (No. 2018YFB1107602)the National Natural Science Foundation of China (Nos. 51875405 & 51375336)。
文摘Glass-ceramics have many excellent properties and are widely used in various fields. During the grinding process,the workpiece surface is typically subject to material removal by grit of incremental heights, which has rarely been the focus of research. As such, it is necessary to study the material removal mechanism of glass-ceramics under consecutive incremental loading, which more closely reflects the actual grinding process. In this paper,to analyze the plastic deformation and residual stress of lithium aluminosilicate(LAS) glass-ceramics, a finite element model is established based on the Drucker–Prager yield criterion for ductile regimes. A nano-scratch test was also conducted and the test results show that both the residual depth and residual stress increase with an increase in the number of increments, and that consecutive incremental loading promotes the plastic deformation of glass-ceramics and increases the residual stress of the material in the ductile-regime process. These findings provide guidance for achieving higher dimensional accuracy in the actual grinding of glass-ceramics parts.
基金financial support from National Natural Science Foundation of China(Grant No.51835004 and 51575197)Huaqiao University International Cultivation Program for Outstanding Postgraduates and Subsidized Projec for Postgraduates’Innovative Fund in Scientific Research of Huaqiao University(No.18011080010)。
文摘Single crystal silicon carbide(SiC)is widely used for optoelectronics applications.Due to the anisotropic characteristics of single crystal materials,the C face and Si face of single crystal SiC have different physical properties,which may fit for particular application purposes.This paper presents an investigation of the material removal and associated subsurface defects in a set of scratching tests on the C face and Si face of 4H-SiC and 6H-SiC materials using molecular dynamics simulations.The investigation reveals that the sample material deformation consists of plastic,amorphous transformations and dislocation slips that may be prone to brittle split.The results showed that the material removal at the C face is more effective with less amorphous deformation than that at the Si face.Such a phenomenon in scratching relates to the dislocations on the basal plane(0001)of the SiC crystal.Subsurface defects were reduced by applying scratching cut depths equal to integer multiples of a half molecular lattice thickness,which formed a foundation for selecting machining control parameters for the best surface quality.
基金supported by the National Key R&D Pro-gram of China(No.2021YFF0501700)the National Nat-ural Science Foundation of China(No.51905255)+1 种基金the Project of Guangdong Provincial Department of Education(No.2019KTSCX152)the Shenzhen Science and Technology Pro-gram(No.GJHZ20200731095204014).
文摘Electrochemical jet machining(EJM)encounters significant challenges in the microstructuring of chemically inert and passivating materials because an oxide layer is easily formed on the material surface,preventing the progress of electrochemical dissolution.This research demonstrates for the first time a jet-electrolytic plasma micromachining(Jet-EPM)method to overcome this problem.Specifically,an electrolytic plasma is intentionally induced at the jet-material contact area by applying a potential high enough to surmount the surface boundary layer(such as a passive film or gas bubble)and enable material removal.Compared to traditional EJM,introducing plasma in the electrochemical jet system leads to considerable differences in machining performance due to the inclusion of plasma reactions.In this work,the implementation of Jet-EPM for fabricating microstructures in the semiconductor material 4H-SiC is demonstrated,and the machining principle and characteristics of Jet-EPM,including critical parameters and process windows,are comprehensively investigated.Theoretical modeling and experiments have elucidated the mechanisms of plasma ignition/evolution and the corresponding material removal,showing the strong potential of Jet-EPM for micromachining chemically resistant materials.The present study considerably augments the range of materials available for processing by the electrochemical jet technique.
基金Supported by National Natural Science Foundation of China(Grant No.52075434)Key R&D Projects in Shaanxi Province(Grant No.2021KW-36).
文摘The hot or cold processing would induce the change and the inhomogeneous of the material mechanical properties in the local processing region of the structure,and it is difficult to obtain the specific mechanical properties in these regions by using the traditional material tensile test.To accurately get actual material mechanical properties in the local region of structure,a micro-indentation test system incorporated by an electronic universal material test device has been established.An indenter displacement sensor and a group of special micro-indenter assemblies are estab-lished.A numerical indentation inversion analysis method by using ABAQUS software is also proposed in this study.Based on the above test system and analysis platform,an approach to obtaining material mechanical properties in the local region of structures is proposed and established.The ball indentation test is performed and combined with the energy method by using various changed mechanical properties of 316L austenitic stainless steel under differ-ent elongations.The investigated results indicate that the material mechanical properties and the micro-indentation morphological changes have evidently relevance.Compared with the tensile test results,the deviations of material mechanical parameters,such as hardness H,the hardening exponent n,the yield strength σy and others are within 5%obtained through the indentation test and the finite element analysis.It provides an effective and convenient method for obtaining the actual material mechanical properties in the local processing region of the structure.
基金National Natural Science Foundation of China(No.81273662,81473592)。
文摘Objective:Use network pharmacology to explore the anti-COVID-19 mechanism of Huashi Baidu Recipe,supplemented by molecular docking verification.Methods:Thorugh databases such as TCMSP,GeneCard,String,and software such as Cytoscape,AutoDockVina,network relationships was established,and the binding ability of active ingredients and targets is calculated through molecular docking,and biological function enrichment analysis was conducted.Result:The ingredients in Huashi Baidu Recipe that had strong affinity with SARS-CoV-23CL hydrolase(3CLpro)and angiotensin converting enzyme 2(ACE2)receptors include Quercetin,Baicalein,Astragaloside IV,Wogonin and other ingredients;25 active ingredients which obtained by screening had strong affinity with targets such as IL6,IL1B,NOS2 and CCL2.The biological function enrichment analysis mainly focused on Th17,Th1 and Th2 cell differentiation,NF-κB,MAPK,TNF,IL-17signaling pathway,etc.Conclusion:The active ingredients of Huashi Baidu Recipe may inhibit the infection and replication of SARS-CoV-2 virus,regulate RAS system’balance,inhibit excessive immune inflammatory response,and prevent inflammatory storm from appearing to fight COVID-19.
基金the Taishan Young Scholar Program of Shandong Province(No.tsqnz20231235)National Natural Science Foundation of China(Grant Nos.22104021,52303075,22227804)+1 种基金Natural Science Foundation of Shandong Province(ZR2023QB227)Department of Science and Technology of Guangdong Province(2022A1515110014).
文摘Human skin perceives external environmental stimulus by the synergies between the subcutaneous tactile corpuscles.Soft electronics with multiple sensing capabilities by mimicking the function of human skin are of significance in health monitoring and artificial sensation.The last decade has witnessed unprecedented development and convergence between multimodal tactile sensing devices and soft bioelectronics.Despite these advances,traditional flexible electronics achieve multimodal tactile sensing for pressure,strain,temperature,and humidity by integrating monomodal sensing devices together.This strategy results in high energy consumption,limited integration,and complex manufacturing process.Various multimodal sensors and crosstalk-free sensing mechanisms have been proposed to bridge the gap between natural sensory system and artificial perceptual system.In this review,we provide a comprehensive summary of tactile sensing mechanism,integration design principles,signal-decoupling strategies,and current applications for multimodal tactile perception.Finally,we highlight the current challenges and present the future perspectives to promote the development of multimodal tactile perception.
基金supported by the National Natural Science Foundation of China(Nos.51921003,92160301,52175415 and 52205475)the Science Center for Gas Turbine Project(No.P2022-A-IV-002-001)Natural Science Foundation of Jiangsu Province(No.BK20210295).
文摘Presently,the service performance of new-generation high-tech equipment is directly affected by the manufacturing quality of complex thin-walled components.A high-efficiency and quality manufacturing of these complex thin-walled components creates a bottleneck that needs to be solved urgently in machinery manufacturing.To address this problem,the collaborative manufacturing of structure shape and surface integrity has emerged as a new process that can shorten processing cycles,improve machining qualities,and reduce costs.This paper summarises the research status on the material removal mechanism,precision control of structure shape,machined surface integrity control and intelligent process control technology of complex thin-walled components.Numerous solutions and technical approaches are then put forward to solve the critical problems in the high-performance manufacturing of complex thin-wall components.The development status,challenge and tendency of collaborative manufacturing technologies in the high-efficiency and quality manufacturing of complex thin-wall components is also discussed.
基金supported by the National Natural Science Foundation of China(No.51975343)Science and Technology Major Project of Inner Mongolia Autonomous Region in China(No.2021ZD0028)+1 种基金Shanghai Technical Service Center for Advanced Ceramics Structure Design and Precision Manufacturing(No.20DZ2294000)the China Scholarship Council.
文摘The material loss caused by bubble collapse during the micro-nano bubbles auxiliary chemical mechanical polishing(CMP)process cannot be ignored.In this study,the material removal mechanism of cavitation in the polishing process was investigated in detail.Based on the mixed lubrication or thin film lubrication,bubble-wafer plastic deformation,spherical indentation theory,Johnson-Cook(J-C)constitutive model,and the assumption of periodic distribution of pad asperities,a new model suitable for micro-nano bubble auxiliary material removal in CMP was developed.The model integrates many parameters,including the reactant concentration,wafer hardness,polishing pad roughness,strain hardening,strain rate,micro-jet radius,and bubble radius.The model reflects the influence of active bubbles on material removal.A new and simple chemical reaction method was used to form a controllable number of micro-nano bubbles during the polishing process to assist in polishing silicon oxide wafers.The experimental results show that micro-nano bubbles can greatly increase the material removal rate(MRR)by about 400%and result in a lower surface roughness of 0.17 nm.The experimental results are consistent with the established model.In the process of verifying the model,a better understanding of the material removal mechanism involved in micro-nano bubbles in CMP was obtained.
基金supported by the National Natural Science Foundation of China(Nos.52175124 and 52305139)the Natural Science Foundation of Zhejiang Province(Nos.LZ21E050003,LY17E050004,and LQ23E050017)+1 种基金the Zhejiang Provincial Postdoctoral Merit-Based Funding Project(No.ZJ2022068)the Open Foundation of the State Key Laboratory of Fluid Power and Mechatronic Systems(No.GZKF-202125),China.
文摘This paper reviews recent developments of the soft abrasive flow finishing(SAF)method in constraint space.The multiphase fluid dynamics modeling,material removal mechanism,auxiliary strengthening finishing techniques,and observation of surface impact effects by abrasive particles and cavitation bubbles are presented in brief.Development prospects and challenges are given for four aspects:thin-walled curved surfaces,biomedical functions,electronic information,and precise optical components.
基金supported by the National Natural Science Foundation of China(No.51922066)the Key Research and Development Plan of Shandong Province(Nos.2019JMRH0307,2020CXGC010204)。
文摘Carbon fiber reinforced silicon carbide(C_(f)/SiC)composites are widely used in aerospace for their excellent mechanical properties.However,the quality of the machined surface is poor and unpredictable due to the material heterogeneity induced by complex removal mechanism.To clarify the effects of fiber orientation on the grinding characteristics and removal mechanism,single grit scratch experiments under different fiber orientations are conducted and a three-phase numerical modelling method for 2.5D C_(f)/SiC composites is proposed.Three fiber cutting modes i.e.,transverse,normal and longitudinal,are defined by fiber orientation and three machining directions i.e.,MA(longitudinal and normal),MB(longitudinal and transverse)and MC(normal and transverse),are selected to investigate the effect of fiber orientation on grinding force and micro-morphology.Besides,a three-phase cutting model of 2.5D C_(f)/SiC composites considering the mechanical properties of the matrix,fiber and interface is developed.Corresponding simulations are performed to reveal the micro-mechanism of crack initiation and extension as well as the material removal mechanism under different fiber orientations.The results indicate that the scratching forces fluctuate periodically,and the order of mean forces is MA>MC>MB.Cracks tend to grow along the fiber axis,which results in the largest damage layer for transverse fibers and the smallest for longitudinal fibers.The removal modes of transverse fibers are worn,fracture and peel-off,in which normal fibers are pullout and outcrop and the longitudinal fibers are worn and push-off.Under the stable cutting condition,the change of contact area between fiber and grit leads to different removal modes of fiber in the same cutting mode,and the increase of contact area results in the aggravation of fiber fracture.
基金the National Natural Science Foundation of China(No.51975368)。
文摘Continuous fiber reinforced SiC ceramic matrix composites(FRCMCs-SiC)are currently the preferred material for hot section components,safety–critical components and braking components(in the aerospace,energy,transportation)with high value,and have triggered the demand for machining.However,the high brittleness,anisotropy,and heterogeneity of materials bring great challenges to machining,due to high mechanical and thermal loads,severe tool wear,and poor machining quality.With the increasing demand of FRCMCs-SiC parts,high-quality and high-efficient machining has become a hot issue.This review paper provides a detailed literature survey on the machining of FRCMCs-SiC.The material removal mechanism,defect form,and interfacial mechanical properties of FRCMCs-SiC were summarized.The machining processes of FRCMCs-SiC were introduced,and their respective advantages and disadvantages were compared.Given the low machinability(high hardness,high brittleness,anisotropy,and heterogeneity)of FRCMCs-SiC,preliminary experiments have proved that ultrasonic-assisted machining and laser-assisted machining have shown unique advantages in reducing force and tool wear,improving machining quality and machining efficiency.The machined surface integrity was discussed,the influence of process parameters on the machined surface quality was analyzed,and the machining defects of FRCMCs-SiC were summarized.But for FRCMCs-SiC,the existing quantitative evaluation of the machined surface integrity was weak and unsystematic.
基金the National Key R&D Program of China(Grant No.2020YFB2010500)the National Natural Science Foundation of China(Grant Nos.51975305 and 51905289)+2 种基金Shandong Natural Science Foundation,China(Grant Nos.ZR2020KE027 and ZR2020ME158)the Innovation Talent Supporting Program for Postdoctoral Fellows of Shandong Province,China(Grant No.SDBX2020012)the Major Science and Technology Innovation Engineering Projects of Shandong Province,China(Grant No.2019JZZY020111).
文摘Fiber-reinforced composites have become the preferred material in the fields of aviation and aerospace because of their high-strength performance in unit weight.The composite components are manufactured by near netshape and only require finishing operations to achieve final dimensional and assembly tolerances.Milling and grinding arise as the preferred choices because of their precision processing.Nevertheless,given their laminated,anisotropic,and heterogeneous nature,these materials are considered difficult-to-machine.As undesirable results and challenging breakthroughs,the surface damage and integrity of these materials is a research hotspot with important engineering significance.This review summarizes an up-to-date progress of the damage formation mechanisms and suppression strategies in milling and grinding for the fiber-reinforced composites reported in the literature.First,the formation mechanisms of milling damage,including delamination,burr,and tear,are analyzed.Second,the grinding mechanisms,covering material removal mechanism,thermal mechanical behavior,surface integrity,and damage,are discussed.Third,suppression strategies are reviewed systematically from the aspects of advanced cutting tools and technologies,including ultrasonic vibration-assisted machining,cryogenic cooling,minimum quantity lubrication(MQL),and tool optimization design.Ultrasonic vibration shows the greatest advantage of restraining machining force,which can be reduced by approximately 60%compared with conventional machining.Cryogenic cooling is the most effective method to reduce temperature with a maximum reduction of approximately 60%.MQL shows its advantages in terms of reducing friction coefficient,force,temperature,and tool wear.Finally,research gaps and future exploration directions are prospected,giving researchers opportunity to deepen specific aspects and explore new area for achieving high precision surface machining of fiber-reinforced composites.
基金This work was supported by the National Natural Science Foundation of China(Nos.51375291 and 91323302)the Natural Science Foundation of Shanghai(No.19ZR1401500).
文摘Current three-body abrasive wear theories are based on a macroscale abrasive indentation process,and these theories claim that material wear cannot be achieved without damaging the hard mating surface.In this study,the process of three-body nano-abrasive wear of a system including a single crystalline silicon substrate,an amorphous silica cluster,and a polyurethane pad,based on a chemical mechanical polishing(CMP)process,is investigated via molecular dynamics simulations.The cluster slid in a suspended state in smooth regions and underwent rolling impact in the asperity regions of the silicon surface,realizing non-damaging monoatomic material removal.This proves that indentation-plowing is not necessary when performing CMP material removal.Therefore,a non-indentation rolling-sliding adhesion theory for three-body nano-abrasive wear between ultrasoft/hard mating surfaces is proposed.This wear theory not only unifies current mainstream CMP material removal theories,but also clarifies that monoatomic material wear without damage can be realized when the indentation depth is less than zero,thereby perfecting the relationship between material wear and surface damage.These results provide new understanding regarding the CMP microscopic material removal mechanism as well as new research avenues for three-body abrasive wear theory at the monoatomic scale.
基金funding provided by the National Natural Science Foundation of China(Nos.62127901,6207031149 and11903035).
文摘Magnetorheological finishing(MRF)technology is widely used in the fabrication of high-precision optical elements.The material removal mechanism of MRF has not been fully understood because MRF technology involves the integration of electromagnetics,contact mechanics,and materials science.In this study,the rheological properties of the MR polishing fluid in oscillation model have been investigated.We propose that the shear-thinned MR polishing fluid over the polishing area should be considered a dense granular flow,based on which a new contact model of MRF over the polishing area has been constructed.Removal function and processing force test experiments were conducted under different working gaps.The normal pressure and effective friction equations over the polishing area were built based on the continuous medium and dense granular flow theories.Then,a novel MRF material removal model was established.A comparison of the results of the theoretical model with actual polishing results demonstrated the accuracy of the established model.The novel model proposed herein reveals the generation mechanism of shear force over a polished workpiece and realizes effective decoupling of the main processing parameters that influence the material removal of MRF.The results of this study will provide new and effective theoretical guidance for the process optimization and technology improvement of MRF.
