An analytical model for contact area and contact stress considering the loading history in incremental sheet forming(ISF)was established.Then,by integrating with the directional characteristics of friction force and h...An analytical model for contact area and contact stress considering the loading history in incremental sheet forming(ISF)was established.Then,by integrating with the directional characteristics of friction force and horizontal force in the process,a friction test method reflecting the forming characteristics of ISF was proposed.Friction coefficients during the forming processes of parts with different wall angles were measured under various plane curves,process paths,and lubrication conditions.Furthermore,the accuracy of the analytical model,as well as the measured friction coefficients and their variation trends,was verified through comparative analysis with experimental results,simulation data,and outcomes from other existing models.The results indicate that the influence of the plane curve characteristics and process paths of parts on the friction condition is not significant.Under the lubrication conditions of L-HM46 oil,MoS_(2)grease,graphite powder,and dry friction,the friction coefficient shows a gradually increasing trend.Notably,when the wall angle is≤40°,the friction coefficient remains relatively constant;however,when the wall angle exceeds 40°,the friction coefficient increases progressively.展开更多
The basic technology and properties of the brake blocks made of modified needle-like wollastonite and fibrous sepiolite were intensively researched.The impact strengthes and fixed velocity friction of the brake blocks...The basic technology and properties of the brake blocks made of modified needle-like wollastonite and fibrous sepiolite were intensively researched.The impact strengthes and fixed velocity friction of the brake blocks prepared by different recipes were tested. The testing results show that it is feasible for needle-like wollastonite and fibrous sepiolite to take the place of asbestos as the reinforced materials of friction materials.The braking effect of the brake blocks is the best when the ratio of the needle-like wollastonite to the fibrous sepiolite was 1∶6.展开更多
Titanium has been increasingly applied to biomedical application because of its improved mechanical characteristics, corrosion resistance and biocompatibility. However their application remains limited, due to the low...Titanium has been increasingly applied to biomedical application because of its improved mechanical characteristics, corrosion resistance and biocompatibility. However their application remains limited, due to the low strength and poor wear resistance of unalloyed titanium. The purpose of this study is to evaluate the friction and wear behavior of high-strength titanium alloys: Ti-6Al-7Nb used in femoral stem (total hip prosthesis). The oscillating friction and wear tests have been carried out in ambient air with oscillating tribotester in accord with standards ISO 7148, ASTM G99-95a, ASTM G 133-95 under different conditions of normal applied load (3, 6 and 10 N) and sliding speed (1, 15 and 25 mm.s-1), and as a counter pair we used the ball of 100C 6, 10 mm of diameter. The surface morphology of the titanium alloys has been characterized by SEM, EDAX, micro hardness, roughness analysis measurements. The behavior observed for both samples suggests that the wear and friction mechanism during the test is the same for Ti alloys, and to increase resistance to wear and friction of biomedical titanium alloys used in total hip prosthesis (femoral stems) the surface coating and treatment are required.展开更多
China's railway prestressed concrete bridge has more than 600000 holes,prestressed engineering is a key force system affecting the safety and durability of the prestressed concrete bridge structure,its constructio...China's railway prestressed concrete bridge has more than 600000 holes,prestressed engineering is a key force system affecting the safety and durability of the prestressed concrete bridge structure,its construction quality is easily affected by traditional manual operation technology,resulting in low construction efficiency and control accuracy,easy to form a hidden danger of quality and safety,it is difficult to meet the needs of less humanized,standardized intelligent construction trend.Based on the research on the intelligent prestressed construction control and testing technology and equipment for railway bridges,this paper proposes the integration of intelligent prestressed tension control and tunnel friction test of railway bridges,intelligent grouting control of tunnel and intelligent testing of beam construction quality,and sets up a complete technical system and integrated equipment for intelligent prestressed construction of bridges based on the industrial Internet of Things(IoT).Overall,improve the quality and efficiency of bridge production,construction,and management.展开更多
Previous studies have demonstrated that the surge in jacking force during the Guanjingkou project is caused by the contact conditions of the debris bentonite slurry outside the pipe.Therefore,this paper further system...Previous studies have demonstrated that the surge in jacking force during the Guanjingkou project is caused by the contact conditions of the debris bentonite slurry outside the pipe.Therefore,this paper further systematically investigates the influence of different debris slurry mass ratios(SLRs)and different particle size distributions(PSDs)on the pipe-rock friction characteristics using friction tests.The test results reveal that under the same PSD,an adequate amount of slurry(with an SLR of 1:4)consistently yields the lowest friction coefficient.When the SLR is between 1:2 and 1:3,the viscosity of the slurry reaches its peak,resulting in the highest friction coefficient.Additionally,when the PSD is 1:1:5 and 1:1:15,the friction coefficient is primarily governed by the plowing effect at the contact surface.When the PSD is 5:1:1 and 15:1:1,the friction coefficient is mainly controlled by the void ratio(VR)of debris.In the case of PSDs 1:5:1 and 1:15:1,the friction coefficient is jointly controlled by the adhesion effect of high-viscosity slurry and the plowing effect at the contact surface,and it gradually shifts towards being dominated by the VR as the amount of debris increases.Regardless of the SLRs and PSDs,the continuous deposition of debris and the injection of slurry incessantly exacerbate both the plowing and adhesion effects,creating a vicious cycle.This is the reason why the high-pressure water flushing method can not only fail to resolve the issue but also accelerate the occurrence of the surge in jacking force.展开更多
Several groups of direct shear tests of Nanning expansive soil samples were carded out by improved direct shear apparatus. The results of the characteristics of the ultimate shear stress and residual shear stress at t...Several groups of direct shear tests of Nanning expansive soil samples were carded out by improved direct shear apparatus. The results of the characteristics of the ultimate shear stress and residual shear stress at the interface of expansive soil-structure are presented as follows： linear relation can approximately reflect changes between the both shear stress and the three factors： vertical load, water content and dry density, just different degrees from each other; increasing the vertical load from 25 kPa to 100 kPa （up by 300%） can cause the average increase of ultimate shear stress from 58% （for samples with 1.61 g/cm^3） to 80% （for samples with 1.76 g/cm^3）, and an close average increase of 180% for the residual shear stress; increasing the water content from 14.1% to 20.8% （up by 47.5%） can cause the average decrease of the ultimate shear stress from 40% （for samples with 25 kPa） to 80% （for samples with 100 kPa）, and the average decrease from 25% （for samples with 25 kPa） to 30% （for samples with 100 kPa） for the residual shear stress; increasing the dry density from 1.61 g/cm^3 to 1.76 g/cm^3 （up by 9.3%） can cause the average increase of ultimate shear stress from 92% （for samples with 25 kPa） to 138% （for samples with 100 kPa）, and an average increase of 4% for the residual shear stress. Sensitive analysis was further made to explain reasons causing the differences of the both shear stress induced by the three factors.展开更多
The stability of slopes is essential for ensuring safe production in open-pit mines.Analyzing and managing the deformation and failure of the slope rock mass becomes more challenging as the slope height increases.To i...The stability of slopes is essential for ensuring safe production in open-pit mines.Analyzing and managing the deformation and failure of the slope rock mass becomes more challenging as the slope height increases.To investigate the damage patterns of slopes with varying heights,three slope models were developed based on a rock slope in Dagushan,China.The deformation failure processes of slopes under the influence of excavation and unloading were analyzed using the base friction test method in combination with digital image technology contrasting.The results supported the following findings:(1)Unloading tensile stress caused lateral partitioning in the slope.Both the foot and top of the slope underwent initial tensile cracks.(2)The destabilization mechanism of unloading deformation in slopes of different heights involved a combination of traction at the foot of the slope or pushing at the top of the slope,followed by accelerated deformation,deceleration creep,and overall destabilization.(3)The unloading damage patterns of slopes at different heights were summarized as follows:compression tension cracking,traction,and slip damage for medium and low slopes;compression tension cracking,traction,and slip failure for the upper part of high slopes;and relaxation tension cracking,pushing,traction,and slip failure for the lower part.Moreover,the upper part of ultra-high slopes exhibited compression tension cracking,traction,and slip failure,while the middle and lower parts displayed relaxation tension cracking,pushing,traction,and slip patterns.Finally,numerical simulations were conducted to verify the results of the test analyses,which demonstrated good consistency.These research results were of great engineering value for proposing effective safety management measures for high slopes.展开更多
Mechanical properties of methane hydrate- bearing-sediments （MHBS） are basic parameters for safety analysis of hydrate exploration and exploitation. Young＇s modulus, cohesion, and internal friction angle of hydrate...Mechanical properties of methane hydrate- bearing-sediments （MHBS） are basic parameters for safety analysis of hydrate exploration and exploitation. Young＇s modulus, cohesion, and internal friction angle of hydrate- bearing sediments synthesized in laboratory, are investigated using tri-axial tests. Stress-strain curves and strength parameters are obtained and discussed for different compositions and different hydrate saturation, followed by empirical expressions related to the cohesion, internal friction angle, and modulus of MHBS. Almost all tested MHBS samples exhibit plastic failure. With the increase of total saturation of ice and methane hydrate （MH）, the specimens＇ internal friction angle decreases while the cohesion increases.展开更多
Scratch test and friction test were performed to evaluate the internal and external interface behaviors of TiAISiN coating, respectively. The critical compressive and shearing stress of coating failure during scratch ...Scratch test and friction test were performed to evaluate the internal and external interface behaviors of TiAISiN coating, respectively. The critical compressive and shearing stress of coating failure during scratch test were calculated and the values are 30.84 MPa and 4.98 MPa respectively. The average friction coefficients of TiAISiN coat- ing against 2Crl2Ni4Mo3VNbN steel are 0.70 （sliding speed 50 m/rain）, 0.63 （sliding speed 100 m/min）, and 0.81 （sliding speed 150 m/min）. The elements diffusion was analyzed by EDS. A1 and Si element of coating material dif- fuse to the steel disc, except Ti element. The oxidation decreases with the increase of sliding speed, but the adhesion increases with the increase of sliding speed. More A1 element diffuses to the steel disc at the high sliding speed, but the diffusion of Si element keeps almost constant at dlfferent sliding speeds.展开更多
In this paper,a physical base friction test model of a slope is established.The model is based on similarity principles and the geological conditions of a complicated bridge slope during construction,deformation and f...In this paper,a physical base friction test model of a slope is established.The model is based on similarity principles and the geological conditions of a complicated bridge slope during construction,deformation and failure.The behavior of the slope in both its natural state and during excavation loading is qualitatively analyzed through base friction tests.The base friction test results are then subjected to comparison and analysis using finite element numerical simulation.The findings show that the whole engineered slope tends to stabilize in its natural state,whereas instabilities will arise at faulted rock masses located near bridge piers during excavation loading.Therefore,to ensure normal construction operation of bridge works,it is suggested that pre-reinforcement of faulted rock masses be performed.展开更多
Friction properties of rock are closely connected with the anisotropy.The anisotropy of rock friction can provide a valuable assessment for geotechnical and geological engineering.In this study,the rotary friction tes...Friction properties of rock are closely connected with the anisotropy.The anisotropy of rock friction can provide a valuable assessment for geotechnical and geological engineering.In this study,the rotary friction tests were conducted to analyze the water effect on the friction property and the friction anisotropy of the four types of rock.The drilling response model(DD-model)was employed to characterize the rotary friction behavior of the rocks.The parameters of this model include the three types of friction parameters:1/ς,μ,and f,where 1/ςandμare constant,and f is a variable.A quantitative method is proposed for assessing the anisotropy of rock friction.The results of the rotary friction tests indicate that the relation between torque force and thrust force conforms to the DD-model.The changes of two friction constants 1/ςandμfrom dry state to water-saturated state suggest that the water effect on the friction strength of the rocks exhibits significant anisotropy.The friction strength determined by the friction variable f increases first,then decreases,and finally stabilizes with the increasing of depth.AIf is an anisotropy index calculated by the proposed method.The percentage difference of the average value of AIf between water-saturated and dry states shows the degree of the water effect on the friction anisotropy of the rocks,mudstone(MU)>granite(GR)>fine sandstone(FS)>argillaceous siltstone(AS).The quantitative model is hopefully constructed for characterizing the relation between the anisotropic friction strength of rock and the moisture state in future.展开更多
With the development of superlubricity, the requirement for the accuracy of measuring super low friction force becomes more and more high. In this study, a novel micro-tribometer has been designed. The resolution and ...With the development of superlubricity, the requirement for the accuracy of measuring super low friction force becomes more and more high. In this study, a novel micro-tribometer has been designed. The resolution and accuracy of friction force are 0.01 m N by using the dual frequency laser interferometer. Experiments were performed to investigate the ability of measuring friction force from different aspects. The interference signal mixed in the measured friction force curve was analyzed and can be removed by a designed filter. The results of experiment show that the tribometer is capable of measuring a super low friction force in the order of magnitude of 0.01 m N with an applied load up to 1 N.展开更多
Understanding the slip-style evolution of tectonic faults is important for exploring the earthquake mechanisms. Toreveal the fault slip characteristics under a complex stress state, we conducted a series of laboratory...Understanding the slip-style evolution of tectonic faults is important for exploring the earthquake mechanisms. Toreveal the fault slip characteristics under a complex stress state, we conducted a series of laboratory friction testson saw-cut granite joint surfaces. The effects of load point velocity and normal stress disturbances were investigated. Based on laboratory observations, a one-dimensional Spring-Block model was developed to interpret thefrictional behavior. Under constant normal stress, the simulated fault (granite joint) exhibits a regular stick-slipphenomenon at different load point velocities with stable recurrence intervals and stress drop magnitudes.Under cyclic normal stress, when the load point velocity is slow, stick-slip events occur only after 4-5 cycles ofnormal stress loading. When the load point velocity is large, due to the rapid sliding of the joint interface, onenormal stress cycle can lead to 4-5 stick-slip events. We find that the cyclic normal stress weakens the joint shearstrength when the load point velocity is slow and improves the strength when the velocity is fast. There is acritical value of load point velocity for resonance where the stick-slip occurrence timespan is identical to thenormal stress cyclic period. This work sheds light on the frictional evolution of tectonic faults during the seismiccycles influenced by a complex stress state.展开更多
Food entering the oral cavity undergoes a series of complex processing behaviors.It is subjected to compression and shearing by the teeth,tongue,and palate to reduce its size and mix with saliva until it is swallowed....Food entering the oral cavity undergoes a series of complex processing behaviors.It is subjected to compression and shearing by the teeth,tongue,and palate to reduce its size and mix with saliva until it is swallowed.The oral processing behaviors are thought to be closely related to both food and oral frictional properties.Much effort has been made in recent decades about food oral tribology to explore this complicated lubrication behavior.Understanding the lubrication mechanism of food in the mouth is important for improving the consumption experience and developing the novel food.This paper provides a new perspective on the effects of composition,texture,structure,and saliva-food component interactions on lubrication properties of different foods,the relationship between sensory perception and oral frictional behavior,and the mechanism and pattern of lubrication categorized by common food types.The roles of tribology in the improvement of food taste,the search for healthier ingredient substitutes,functional foods,and the development of green foods are analyzed.Conceptual and numerical prediction models among physical properties,sensory perception,and frictional behavior of food are discussed.Studies of simulating oral processing,such as the selection of friction pair materials,physical modification of contact surfaces,addition of saliva,different modes of motion,and contact forms are concluded and classified.The progress of commercial friction apparatus as well as customized friction devices applied to the food sector in recent years are described.The characteristics,performances,and applications of these tribological instruments are analyzed and compared.In addition,the results achieved by oral tribology in identifying adulterated foods and ensuring food safety are presented.Finally,some suggestions are put forward for the current challenges and future development of food oral tribology.展开更多
基金the National Key R&D Program of China(No.2023YFB3407003)the National Natural Science Foundation of China(No.52375378).
文摘An analytical model for contact area and contact stress considering the loading history in incremental sheet forming(ISF)was established.Then,by integrating with the directional characteristics of friction force and horizontal force in the process,a friction test method reflecting the forming characteristics of ISF was proposed.Friction coefficients during the forming processes of parts with different wall angles were measured under various plane curves,process paths,and lubrication conditions.Furthermore,the accuracy of the analytical model,as well as the measured friction coefficients and their variation trends,was verified through comparative analysis with experimental results,simulation data,and outcomes from other existing models.The results indicate that the influence of the plane curve characteristics and process paths of parts on the friction condition is not significant.Under the lubrication conditions of L-HM46 oil,MoS_(2)grease,graphite powder,and dry friction,the friction coefficient shows a gradually increasing trend.Notably,when the wall angle is≤40°,the friction coefficient remains relatively constant;however,when the wall angle exceeds 40°,the friction coefficient increases progressively.
文摘The basic technology and properties of the brake blocks made of modified needle-like wollastonite and fibrous sepiolite were intensively researched.The impact strengthes and fixed velocity friction of the brake blocks prepared by different recipes were tested. The testing results show that it is feasible for needle-like wollastonite and fibrous sepiolite to take the place of asbestos as the reinforced materials of friction materials.The braking effect of the brake blocks is the best when the ratio of the needle-like wollastonite to the fibrous sepiolite was 1∶6.
文摘Titanium has been increasingly applied to biomedical application because of its improved mechanical characteristics, corrosion resistance and biocompatibility. However their application remains limited, due to the low strength and poor wear resistance of unalloyed titanium. The purpose of this study is to evaluate the friction and wear behavior of high-strength titanium alloys: Ti-6Al-7Nb used in femoral stem (total hip prosthesis). The oscillating friction and wear tests have been carried out in ambient air with oscillating tribotester in accord with standards ISO 7148, ASTM G99-95a, ASTM G 133-95 under different conditions of normal applied load (3, 6 and 10 N) and sliding speed (1, 15 and 25 mm.s-1), and as a counter pair we used the ball of 100C 6, 10 mm of diameter. The surface morphology of the titanium alloys has been characterized by SEM, EDAX, micro hardness, roughness analysis measurements. The behavior observed for both samples suggests that the wear and friction mechanism during the test is the same for Ti alloys, and to increase resistance to wear and friction of biomedical titanium alloys used in total hip prosthesis (femoral stems) the surface coating and treatment are required.
基金Scientific and Technological Development Project of China Railway Design Group Co.,Ltd.(No.2022A02480005)Technology Development Project of China Railway Design Group Co.,Ltd.(No.2023A0248001).
文摘China's railway prestressed concrete bridge has more than 600000 holes,prestressed engineering is a key force system affecting the safety and durability of the prestressed concrete bridge structure,its construction quality is easily affected by traditional manual operation technology,resulting in low construction efficiency and control accuracy,easy to form a hidden danger of quality and safety,it is difficult to meet the needs of less humanized,standardized intelligent construction trend.Based on the research on the intelligent prestressed construction control and testing technology and equipment for railway bridges,this paper proposes the integration of intelligent prestressed tension control and tunnel friction test of railway bridges,intelligent grouting control of tunnel and intelligent testing of beam construction quality,and sets up a complete technical system and integrated equipment for intelligent prestressed construction of bridges based on the industrial Internet of Things(IoT).Overall,improve the quality and efficiency of bridge production,construction,and management.
基金the funding support from the National Natural Science Foundations for Young Scientists of China(Grant No.52208391)Doctoral Foundation Project of Guizhou University(Grant No.2021e78).
文摘Previous studies have demonstrated that the surge in jacking force during the Guanjingkou project is caused by the contact conditions of the debris bentonite slurry outside the pipe.Therefore,this paper further systematically investigates the influence of different debris slurry mass ratios(SLRs)and different particle size distributions(PSDs)on the pipe-rock friction characteristics using friction tests.The test results reveal that under the same PSD,an adequate amount of slurry(with an SLR of 1:4)consistently yields the lowest friction coefficient.When the SLR is between 1:2 and 1:3,the viscosity of the slurry reaches its peak,resulting in the highest friction coefficient.Additionally,when the PSD is 1:1:5 and 1:1:15,the friction coefficient is primarily governed by the plowing effect at the contact surface.When the PSD is 5:1:1 and 15:1:1,the friction coefficient is mainly controlled by the void ratio(VR)of debris.In the case of PSDs 1:5:1 and 1:15:1,the friction coefficient is jointly controlled by the adhesion effect of high-viscosity slurry and the plowing effect at the contact surface,and it gradually shifts towards being dominated by the VR as the amount of debris increases.Regardless of the SLRs and PSDs,the continuous deposition of debris and the injection of slurry incessantly exacerbate both the plowing and adhesion effects,creating a vicious cycle.This is the reason why the high-pressure water flushing method can not only fail to resolve the issue but also accelerate the occurrence of the surge in jacking force.
基金Projects(50378097 50678177) supported by the National Natural Science Foundation of ChinaProject (01JJY3043) supported by the Natural Science Foundation of Hunan Province, China
文摘Several groups of direct shear tests of Nanning expansive soil samples were carded out by improved direct shear apparatus. The results of the characteristics of the ultimate shear stress and residual shear stress at the interface of expansive soil-structure are presented as follows： linear relation can approximately reflect changes between the both shear stress and the three factors： vertical load, water content and dry density, just different degrees from each other; increasing the vertical load from 25 kPa to 100 kPa （up by 300%） can cause the average increase of ultimate shear stress from 58% （for samples with 1.61 g/cm^3） to 80% （for samples with 1.76 g/cm^3）, and an close average increase of 180% for the residual shear stress; increasing the water content from 14.1% to 20.8% （up by 47.5%） can cause the average decrease of the ultimate shear stress from 40% （for samples with 25 kPa） to 80% （for samples with 100 kPa）, and the average decrease from 25% （for samples with 25 kPa） to 30% （for samples with 100 kPa） for the residual shear stress; increasing the dry density from 1.61 g/cm^3 to 1.76 g/cm^3 （up by 9.3%） can cause the average increase of ultimate shear stress from 92% （for samples with 25 kPa） to 138% （for samples with 100 kPa）, and an average increase of 4% for the residual shear stress. Sensitive analysis was further made to explain reasons causing the differences of the both shear stress induced by the three factors.
基金funded by the National Natural Science Foundation of China(No.52308316)China Postdoctoral Science Foundation(No.2022M721885)supported by Key Laboratory of Rock Mechanics and Geohazards of Zhejiang Province(No.ZJRMG2022-01)。
文摘The stability of slopes is essential for ensuring safe production in open-pit mines.Analyzing and managing the deformation and failure of the slope rock mass becomes more challenging as the slope height increases.To investigate the damage patterns of slopes with varying heights,three slope models were developed based on a rock slope in Dagushan,China.The deformation failure processes of slopes under the influence of excavation and unloading were analyzed using the base friction test method in combination with digital image technology contrasting.The results supported the following findings:(1)Unloading tensile stress caused lateral partitioning in the slope.Both the foot and top of the slope underwent initial tensile cracks.(2)The destabilization mechanism of unloading deformation in slopes of different heights involved a combination of traction at the foot of the slope or pushing at the top of the slope,followed by accelerated deformation,deceleration creep,and overall destabilization.(3)The unloading damage patterns of slopes at different heights were summarized as follows:compression tension cracking,traction,and slip damage for medium and low slopes;compression tension cracking,traction,and slip failure for the upper part of high slopes;and relaxation tension cracking,pushing,traction,and slip failure for the lower part.Moreover,the upper part of ultra-high slopes exhibited compression tension cracking,traction,and slip failure,while the middle and lower parts displayed relaxation tension cracking,pushing,traction,and slip patterns.Finally,numerical simulations were conducted to verify the results of the test analyses,which demonstrated good consistency.These research results were of great engineering value for proposing effective safety management measures for high slopes.
基金supported by the National Natural Science Foundation of China (11102209 and 11072245)the National High Technology Research and Development Program of China (863)the Key Program of Chinese Academy of Sciences (KJCX2-YW-L02)
文摘Mechanical properties of methane hydrate- bearing-sediments （MHBS） are basic parameters for safety analysis of hydrate exploration and exploitation. Young＇s modulus, cohesion, and internal friction angle of hydrate- bearing sediments synthesized in laboratory, are investigated using tri-axial tests. Stress-strain curves and strength parameters are obtained and discussed for different compositions and different hydrate saturation, followed by empirical expressions related to the cohesion, internal friction angle, and modulus of MHBS. Almost all tested MHBS samples exhibit plastic failure. With the increase of total saturation of ice and methane hydrate （MH）, the specimens＇ internal friction angle decreases while the cohesion increases.
基金Supported by China Postdoctoral Science Foundation(No. 20110490380 and No. 20110490383)Dongfang Turbine Co, Ltd (No. 2011GZ011)State Key Laboratory of Tribology, Tsinghua University (No. SKLT10A01)
文摘Scratch test and friction test were performed to evaluate the internal and external interface behaviors of TiAISiN coating, respectively. The critical compressive and shearing stress of coating failure during scratch test were calculated and the values are 30.84 MPa and 4.98 MPa respectively. The average friction coefficients of TiAISiN coat- ing against 2Crl2Ni4Mo3VNbN steel are 0.70 （sliding speed 50 m/rain）, 0.63 （sliding speed 100 m/min）, and 0.81 （sliding speed 150 m/min）. The elements diffusion was analyzed by EDS. A1 and Si element of coating material dif- fuse to the steel disc, except Ti element. The oxidation decreases with the increase of sliding speed, but the adhesion increases with the increase of sliding speed. More A1 element diffuses to the steel disc at the high sliding speed, but the diffusion of Si element keeps almost constant at dlfferent sliding speeds.
基金The authors gratefully acknowledge the financial support of this work,which was provided by the National Natural Science Foundation of China(Grant Nos.41172260 and 51108393)the Specialized Research Fund for the Doctoral Program of Higher Education(No.20110184110018)the National Basic Research Program of China(No.2008CB425801).
文摘In this paper,a physical base friction test model of a slope is established.The model is based on similarity principles and the geological conditions of a complicated bridge slope during construction,deformation and failure.The behavior of the slope in both its natural state and during excavation loading is qualitatively analyzed through base friction tests.The base friction test results are then subjected to comparison and analysis using finite element numerical simulation.The findings show that the whole engineered slope tends to stabilize in its natural state,whereas instabilities will arise at faulted rock masses located near bridge piers during excavation loading.Therefore,to ensure normal construction operation of bridge works,it is suggested that pre-reinforcement of faulted rock masses be performed.
基金sponsored by the National Natural Science Foundation of China(Grant nos.42177158,11902249,and 11872301)Key Research and Development project of Shaanxi Province(Grant no.2022SF-412)+4 种基金Education Bureau of Shaanxi Province Scientific Research Plan Projects of Shaanxi Education Department in China(Grant no.20JS093)Opening fund of State Key Laboratory of Geohazard Prevention and Geoenvironment Protection(Chengdu University of Technology)(Grants no.SKLGP2022K005)Higher Education Basic Science(Natural Science)Research Project of Jiangsu Province in China(Grant no.23KJD410002)Yangzhou Green Yang Golden Phoenix Plan(Grant no.2408008/022)Yangzhou Science and Technology Project(Grant no.YZ2021166).
文摘Friction properties of rock are closely connected with the anisotropy.The anisotropy of rock friction can provide a valuable assessment for geotechnical and geological engineering.In this study,the rotary friction tests were conducted to analyze the water effect on the friction property and the friction anisotropy of the four types of rock.The drilling response model(DD-model)was employed to characterize the rotary friction behavior of the rocks.The parameters of this model include the three types of friction parameters:1/ς,μ,and f,where 1/ςandμare constant,and f is a variable.A quantitative method is proposed for assessing the anisotropy of rock friction.The results of the rotary friction tests indicate that the relation between torque force and thrust force conforms to the DD-model.The changes of two friction constants 1/ςandμfrom dry state to water-saturated state suggest that the water effect on the friction strength of the rocks exhibits significant anisotropy.The friction strength determined by the friction variable f increases first,then decreases,and finally stabilizes with the increasing of depth.AIf is an anisotropy index calculated by the proposed method.The percentage difference of the average value of AIf between water-saturated and dry states shows the degree of the water effect on the friction anisotropy of the rocks,mudstone(MU)>granite(GR)>fine sandstone(FS)>argillaceous siltstone(AS).The quantitative model is hopefully constructed for characterizing the relation between the anisotropic friction strength of rock and the moisture state in future.
基金supported by National Natural Scienceof China(Grant Nos.51527901,51335005&51321092)National Basic Research Program of China(Grant No.2013CB934200)
文摘With the development of superlubricity, the requirement for the accuracy of measuring super low friction force becomes more and more high. In this study, a novel micro-tribometer has been designed. The resolution and accuracy of friction force are 0.01 m N by using the dual frequency laser interferometer. Experiments were performed to investigate the ability of measuring friction force from different aspects. The interference signal mixed in the measured friction force curve was analyzed and can be removed by a designed filter. The results of experiment show that the tribometer is capable of measuring a super low friction force in the order of magnitude of 0.01 m N with an applied load up to 1 N.
基金funded by the National Natural Science Foundation of China(No.52474122)the Natural Science Foundation of Guangdong Province,China(No.2022A1515240009).
文摘Understanding the slip-style evolution of tectonic faults is important for exploring the earthquake mechanisms. Toreveal the fault slip characteristics under a complex stress state, we conducted a series of laboratory friction testson saw-cut granite joint surfaces. The effects of load point velocity and normal stress disturbances were investigated. Based on laboratory observations, a one-dimensional Spring-Block model was developed to interpret thefrictional behavior. Under constant normal stress, the simulated fault (granite joint) exhibits a regular stick-slipphenomenon at different load point velocities with stable recurrence intervals and stress drop magnitudes.Under cyclic normal stress, when the load point velocity is slow, stick-slip events occur only after 4-5 cycles ofnormal stress loading. When the load point velocity is large, due to the rapid sliding of the joint interface, onenormal stress cycle can lead to 4-5 stick-slip events. We find that the cyclic normal stress weakens the joint shearstrength when the load point velocity is slow and improves the strength when the velocity is fast. There is acritical value of load point velocity for resonance where the stick-slip occurrence timespan is identical to thenormal stress cyclic period. This work sheds light on the frictional evolution of tectonic faults during the seismiccycles influenced by a complex stress state.
基金This work was supported by the National Natural Science Foundation of China(No.51965039).
文摘Food entering the oral cavity undergoes a series of complex processing behaviors.It is subjected to compression and shearing by the teeth,tongue,and palate to reduce its size and mix with saliva until it is swallowed.The oral processing behaviors are thought to be closely related to both food and oral frictional properties.Much effort has been made in recent decades about food oral tribology to explore this complicated lubrication behavior.Understanding the lubrication mechanism of food in the mouth is important for improving the consumption experience and developing the novel food.This paper provides a new perspective on the effects of composition,texture,structure,and saliva-food component interactions on lubrication properties of different foods,the relationship between sensory perception and oral frictional behavior,and the mechanism and pattern of lubrication categorized by common food types.The roles of tribology in the improvement of food taste,the search for healthier ingredient substitutes,functional foods,and the development of green foods are analyzed.Conceptual and numerical prediction models among physical properties,sensory perception,and frictional behavior of food are discussed.Studies of simulating oral processing,such as the selection of friction pair materials,physical modification of contact surfaces,addition of saliva,different modes of motion,and contact forms are concluded and classified.The progress of commercial friction apparatus as well as customized friction devices applied to the food sector in recent years are described.The characteristics,performances,and applications of these tribological instruments are analyzed and compared.In addition,the results achieved by oral tribology in identifying adulterated foods and ensuring food safety are presented.Finally,some suggestions are put forward for the current challenges and future development of food oral tribology.
