In recent years,the addition of Ni has been widely acknowledged to be capable of enhancing the mechanical properties of Al-Si alloys.However,the effect of Ni on the wear behaviors of Al-Si alloys and Al matrix composi...In recent years,the addition of Ni has been widely acknowledged to be capable of enhancing the mechanical properties of Al-Si alloys.However,the effect of Ni on the wear behaviors of Al-Si alloys and Al matrix composites,particularly at elevated temperat-ures,remains an understudied area.In this study,Al-Si-Cu-Mg-Ni/20wt%SiC particles(SiCp)composites with varying Ni contents were prepared by using a semisolid stir casting method.The effect of Ni content on the dry sliding wear behavior of the prepared compos-ites was investigated through sliding tests at 25 and 350℃.Results indicated that theθ-Al_(2)Cu phase gradually diminished and eventually disappeared as the Ni content increased from 0wt%to 3wt%.This change was accompanied by the formation and increase inδ-Al_(3)CuNi andε-Al_(3)Ni phases in microstructures.The hardness and ultimate tensile strength of the as-cast composites improved,and the wear rates of the composites decreased from 5.29×10^(−4)to 1.94×10^(−4)mm^(3)/(N∙m)at 25℃and from 20.2×10^(−4)to 7×10^(−4)mm^(3)/(N∙m)at 350℃with the increase in Ni content from 0wt%to 2wt%.The enhancement in performance was due to the presence of strengthening network structures and additional Ni-containing phases in the composites.However,the wear rate of the 3Ni composite was approximately two times higher than that of the 2Ni composite due to the fracture and debonding of theε-Al_(3)Ni phase.Abrasive wear,delamination wear,and oxidation wear were the predominant wear mechanisms of the investigated composites at 25℃,whereas delamination wear and oxid-ation wear were dominant during sliding at 350℃.展开更多
The friction and wear properties of Mg2B2O5 whisker reinforced 6061Al matrix composite fabricated via power ultrasonic-stir casting process were investigated using a ball-on-disk wear-testing machine against a GCr45 s...The friction and wear properties of Mg2B2O5 whisker reinforced 6061Al matrix composite fabricated via power ultrasonic-stir casting process were investigated using a ball-on-disk wear-testing machine against a GCr45 steel counterface under dry sliding conditions. The reinforcements include as-received Mg2B2O5 whiskers and Mg2B2O5 whiskers coated with CuO and ZnO. The volume fraction of the composites is 2%. The relationship between the wear rate and the coefficient of friction was discussed. The results indicate that the wear rate of the Mg2B2O5 whiskers coated with ZnO reinforced aluminum matrix composites is the lowest among the materials. As the applied load and sliding speed steadily increase the coefficients of friction and wear rates of the as-received matrix alloy and the fabricated composites decrease. As the applied load and sliding speed increase, the wear mechanisms of the composites shift from a mild to a severe regime.展开更多
A simple impact-sliding wear test rig is designed for studying the wear behavior between solid materials on a repetitive normal impact accompanied with the tangential sliding. The test rig consists of a cantilever bea...A simple impact-sliding wear test rig is designed for studying the wear behavior between solid materials on a repetitive normal impact accompanied with the tangential sliding. The test rig consists of a cantilever beam forced by the dynamoelectric vibration exciter and a rotational shaft driven by a spindle. It has a widely adjustable range of testing parameters, including the impact frequency, the impact load and the sliding velocity. The avail- able maximum impact frequency, impact load and sliding velocity are 100 Hz, 200 N and 4.52 m/s, respectively. To evaluate the capability of the test rig, tests are carried out and the impact load is measured. Results show that the test rig has the good repeatability under the same test conditions and the repeatable error is less than 7%. Furthermore, non-destructive examination results by the mass loss method, two-dimensional profilometry and the scanning electron microscopy (SEM) show that the test rig can meet the demands for the impact-sliding wear.展开更多
The alumina toughened zirconia(ATZ) ceramic particle reinforced gray iron matrix surface composite was successfully manufactured by pressureless infi ltration. The porous preform played a key role in the infi ltrating...The alumina toughened zirconia(ATZ) ceramic particle reinforced gray iron matrix surface composite was successfully manufactured by pressureless infi ltration. The porous preform played a key role in the infi ltrating progress. The microstructure was observed by scanning electron microscopy(SEM); the phase constitutions was analyzed by X-ray diffraction(XRD); and the hardness and wear resistance of selected specimens were tested by hardness testing machine and abrasion testing machine, respectively. The addition of high carbon ferrochromium powders leads to the formation of white iron during solidifi cation. The wear volume loss rates of ATZ ceramic particle reinforced gray iron matrix surface composite decreases fi rst, and then tends to be stable. The wear resistance of the composite is 2.7 times higher than that of gray iron matrix. The reason is a combination of the surface hardness increase of gray iron matrix and ATZ ceramic particles and alloy carbides protecting effect on gray iron matrix.展开更多
To simulate the wear and corrosion behavior of high-strength EH47 hull steel in a complicated marine environment in which seawater,sea ice,and sea sand coexist,accelerated wear and corrosion tests were performed in a ...To simulate the wear and corrosion behavior of high-strength EH47 hull steel in a complicated marine environment in which seawater,sea ice,and sea sand coexist,accelerated wear and corrosion tests were performed in a laboratory setting using a tribometer.The effect of large loads on the behavior of abrasion and corrosion in a 3.5wt%NaCl solution with ice and sand to simulate a marine environment were investigated.The experimental results showed that the coefficient of friction(COF)decreases with increasing working load;meanwhile,the loading force and sand on the disk strongly influence the COF.The mechanisms of friction and the coupling effect of abrasion and corrosion in the 3.5wt%NaCl solution with sand were the wear and corrosion mechanisms;furthermore,the wear mechanism exerted the predominant effect.展开更多
Laser alloying was used for production of thick layers on surface of Nimonic 80A-alloy.For laser surface modification,three types of pre-coated pastes were applied:with amorphous boron,with amorphous boron and molybde...Laser alloying was used for production of thick layers on surface of Nimonic 80A-alloy.For laser surface modification,three types of pre-coated pastes were applied:with amorphous boron,with amorphous boron and molybdenum as well as with amorphous boron and niobium.The microstructure,hardness and wear resistance of produced layers were studied in details.The presence of different types of borides in re-melted zone depended on the paste composition and caused an increase in hardness up to about HV 1000.The wear resistance was evaluated by calculation of mass wear intensity factor Imw and relative mass loss of specimen and counter-specimen.The wear behavior of the tested frictional pairs was determined by 3D interference microscopy,scanning electron microscopy equipped with EDS microanalyzer.The significant increase in abrasive wear resistance was observed in comparison to untreated Nimonic 80A-alloy.The lowest mass loss intensity factor was characteristic of laser-alloyed Nimonic 80A-alloy with boron and niobium(Imw=1.234 mg/(cm2?h)).Laser alloyed-layers indicated abrasive wear mechanism with clearly visible grooves.Laser alloying with boron and niobium resulted in the additional oxidative wear mechanism.In this case,EDS patterns revealed presence of oxygen on the worn surface of specimen.展开更多
Dry sliding wear behaviour of stir-cast aluminium matrix composites(AMCs)containing LM13 alloy as matrix and ceramic particles as reinforcement was investigated.Two different ceramic particle reinforcements were used ...Dry sliding wear behaviour of stir-cast aluminium matrix composites(AMCs)containing LM13 alloy as matrix and ceramic particles as reinforcement was investigated.Two different ceramic particle reinforcements were used separately:synthetic ceramic particles(B_(4)C),and natural ceramic particles(ilmenite).Optical micrographs showed uniform dispersion of reinforced particles in the matrix material.Reinforced particles refined the grain size of eutectic silicon and changed its morphology to globular type.B_(4)C reinforced composites(BRCs)showed maximum improvement in hardness of AMCs.Ilmenite reinforced composites(IRCs)showed maximum reduction in coefficient of friction values due to strong matrix−reinforcement interfacial bonding caused by the formation of interfacial compounds.Dry sliding wear behaviour of composites was significantly improved as compared to base alloy.The low density and high hardness of B_(4)C particles resulted in high dislocation density around filler particles in BRCs.On the other hand,the low thermal conductivity of ilmenite particles resulted in early oxidation and formation of a tribo-layer on surface of IRCs.So,both types of reinforcements led to the improvement in wear properties of AMCs,though the mechanisms involved were very different.Thus,the low-cost ilmenite particles can be used as alternative fillers to the high-cost B_(4)C particles for processing of wear resistant composites.展开更多
The friction and wear properties of interpenetrating phase composites(IPC) SiC3D/Al sliding against graphite/SiC(G/SiC) composites were investigated using a sub-scale brake dynamometer. The testing conditions included...The friction and wear properties of interpenetrating phase composites(IPC) SiC3D/Al sliding against graphite/SiC(G/SiC) composites were investigated using a sub-scale brake dynamometer. The testing conditions included a braking pressure of 1.25 MPa and an initial braking speed(IBS) of 200-350 km/h in a braking process of high-speed train according to the scale-conversion rules. The tribo-couple materials were characterized using scanning electron microscopy(SEM), X-ray diffractometry(XRD), and energy-dispersive X-ray spectrometry(EDS). It is found that the matching tribo-couple features low friction surface temperature, reliable friction factor, and high durability. The continuous lubricating mechanically-mixed layer(MML) forms gradually on the worn surfaces of ring in the friction process. The MML is heterogeneous, which greatly controls wear rate and coefficient of friction(COF) of the composites. The wear mechanism of SiC3D/Al is typically abrasive wear at an IBS of 200-300 km/h. When the IBS increases to 350 km/h, oxidation wear and delamination are observed. The friction behavior of the tribo-couple predicted using Solidwork simulation software agrees well with the experimental results. The tribo-couple meets the requirement of emergency braking of high-speed train.展开更多
The microstructural features and the consequent mechanical properties were characterized in aluminium borate whisker(ABOw)(5, 10 and 15 wt.%) reinforced commercially-pure aluminium composites fabricated by conventiona...The microstructural features and the consequent mechanical properties were characterized in aluminium borate whisker(ABOw)(5, 10 and 15 wt.%) reinforced commercially-pure aluminium composites fabricated by conventional powder metallurgy technique. The aluminium powder and the whisker were effectively blended by a semi-powder metallurgy method. The blended powder mixtures were cold compacted and sintered at 600 ℃. The sintered composites were characterized for microstructural features by optical microscopy(OM), scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS), transmission electron microscopy(TEM) and X-ray diffraction(XRD) analysis. Porosity in the composites with variation in ABOw contents was determined. The effect of variation in content of ABOw on mechanical properties, viz. hardness, bending strength and compressive strength of the composites was evaluated. The dry sliding wear behaviour was evaluated at varying sliding distance at constant loads. Maximum flexural strength of 172 MPa and compressive strength of 324 MPa with improved hardness around HV 40.2 are obtained in composite with 10 wt.% ABOw. Further increase in ABOw content deteriorates the properties. A substantial increase in wear resistance is also observed with 10 wt.% ABOw. The excellent combination of mechanical properties of Al-10 wt.%ABOw composites is attributed to good interfacial bonds, less porosity and uniformity in the microstructure.展开更多
By accurately measuring the displacement between the roller surface and the optical fiber probe relative to a null position, we can test the roller wear. The whole testing method and system were introduced. Each part ...By accurately measuring the displacement between the roller surface and the optical fiber probe relative to a null position, we can test the roller wear. The whole testing method and system were introduced. Each part of the testing system was illustrated. And also a novel fiber-optic sensor with three probes in equal transverse space is adopted. Using this sensor, the effects of fluctuations in the light source, reflectivity changing of target surface and the intensity losses in the fiber lines are automatically compensated. This method offers such advantages as non-contact, no electromagnetic interference, simplicity, low cost, high sensitivity, good accuracy and stability.展开更多
The spherical plain bearing test bench is a necessary detecting equipment in the research process of self?lubricating spherical plain bearings. The varying environmental temperatures cause the thermal deformation of t...The spherical plain bearing test bench is a necessary detecting equipment in the research process of self?lubricating spherical plain bearings. The varying environmental temperatures cause the thermal deformation of the wear?depth detecting system of bearing test benches and then a ect the accuracy of the wear?depth detecting data. However, few researches about the spherical plain bearing test benches can be found with the implementation of the detect?ing error compensation. Based on the self?made modular spherical plain bearing test bench, two main causes of ther?mal errors, the friction heat of bearings and the environmental temperature variation, are analysed. The thermal errors caused by the friction heat of bearings are calculated, and the thermal deformation of the wear?depth detecting sys?tem caused by the varying environmental temperatures is detected. In view of the above results, the environmental temperature variation is the main cause of the two error factors. When the environmental temperatures rise is 10.3 °C, the thermal deformation is approximately 0.01 mm. In addition, the comprehensive compensating model of the thermal error of the wear?depth detecting system is built by multiple linear regression(MLR) and time series analysis. Compared with the detecting data of the thermal errors, the comprehensive compensating model has higher fitting precision, and the maximum residual is only 1 μm. A comprehensive compensating model of the thermal error of the wear?depth detecting system is proposed, which provides a theoretical basis for the improvement of the real?time wear?depth detecting precision of the spherical plain bearing test bench.展开更多
To analyze wheel wear discrepancy between motor car and trailer of an intercity train,a novel wheel wear rates calculation model was proposed,which was composed of the intercity train dynamics model,wheel-rail three-d...To analyze wheel wear discrepancy between motor car and trailer of an intercity train,a novel wheel wear rates calculation model was proposed,which was composed of the intercity train dynamics model,wheel-rail three-dimensional rolling contact FEM model and the wear model.The simulated results were contrasted with measured results in field test.The simulated results showed the motor car wheels had larger rotation rate and longitudinal creepage than the trailer wheels.Meanwhile,the motor car wheels encountered larger vertical forces and longitudinal forces from bogie because of the heavier car body and the impact of traction torque.The traction torque acting on motor car wheel could increase the slip rates in the rear part of wheel contact patch and weaken the spinning phenomenon of relative slip.Larger contact pressure and slip rates caused the higher wear rates of motor car wheel than those of trailer wheel.The overall trends of wheel wear depth in simulated and tested results were similar.And they both showed the motor car wheel encountered the more serious wear than the trailer wheel.These models can be used to study the effect of the traction characteristics curves on the wear of wheel.展开更多
A series of polyester, cotton, and polyester/cotton blend fabrics were evaluated in a subjective wear. Subjective trial data were correlated with the results of in-house laboratory tests with the regression methods. E...A series of polyester, cotton, and polyester/cotton blend fabrics were evaluated in a subjective wear. Subjective trial data were correlated with the results of in-house laboratory tests with the regression methods. Experimental results indicate that clothing-comfort assessment by human perception provides a sound basis for comparison of apparel garments under combined microclimates and human-activity levels of展开更多
The use of asbestos material is being avoided to manufacture the brake pads as it is harmful and toxic in nature. Further it leads to various health issues like asbestosis, mesothelioma and lung cancers. These brake p...The use of asbestos material is being avoided to manufacture the brake pads as it is harmful and toxic in nature. Further it leads to various health issues like asbestosis, mesothelioma and lung cancers. These brake pads can be replaced by natural fibers like Palm kernel (0-50%), Nile roses (0-15%) and Wheat (0-10%) with additives like aluminum oxide (5%-20%) and graphite powder (10%-35%). Phenolic resin of 35% is utilized as a binder. Particulated Nile roses are used to increase the friction coefficient and wheat powder is used to reduce the wear rate. Aluminum oxide and graphite are abrasive in nature. This helps to make brake pads with high friction co-efficient and less wear rate with low noise pollution. The wear of the proposed composites have been investigated at different speeds. Various tests like wear on pin-ondisc apparatus, hardness on the Rockwell hardness apparatus and oil absorption test have been conducted. Phenolic resin produces good bonding nature to fiber. Thus, Fibers found to have performed palatably among all commercial brake pads. The objective of the research indicates that Palm kernal shell could be a conceivable alternative for asbestos in friction coating materials.展开更多
The relationships between the microstructure, the composition, the friction temperature and the form of a new kind of friction material which is a glass fibre resin friction materials (GFRF) are studied through a seri...The relationships between the microstructure, the composition, the friction temperature and the form of a new kind of friction material which is a glass fibre resin friction materials (GFRF) are studied through a series of tests on machine as EPMA, STM, DTG-DTA,an optical microscope and a friction test machine. The tests show that the rising rate in temperature and the heat conductivity of GFRF are lower than that of asbestos friction material. In GFRF, the heat-decline is slowed down or even eliminated. the distribution of heat- stress is improved and the life span is extended. Raising the temperature of resin resolution and enhancing the stickness between resin and glass fibre are the two important procedures to improve the friction and wear performance of GFRF.A discription about the friction and wear mechanism of GFRF is given in this paper.展开更多
Reducing wear on a side dam can prolong the casting operation life of a twin-roll strip casting process,thus reducing production cost and improving casting stability.To lengthen the service life of the side dam,it is ...Reducing wear on a side dam can prolong the casting operation life of a twin-roll strip casting process,thus reducing production cost and improving casting stability.To lengthen the service life of the side dam,it is necessary to understand the wear performance of the side dam material.To investigate the wear behavior mechanism of the side dam,in this study,the UMT-2 friction and wear tester was used to determine the relationship between the wear rate of the side-dam material and various parameters.Based on the roughness of the contact area between the side dam and the end of the casting rolls as well as on the amount of deformation of the side dam,which was derived using a thermal-deformation simulation model,the reasons for the uneven wear of the side dam were obtained.展开更多
Mobarakeh Steel Company produces 3 million tons of steel annually with eight 180 tons EBT furnaces. Different types of magnesia-carbon refractories have been employed at slagline during last 5 years. In the present st...Mobarakeh Steel Company produces 3 million tons of steel annually with eight 180 tons EBT furnaces. Different types of magnesia-carbon refractories have been employed at slagline during last 5 years. In the present study the wear and corrosion of MgO-C refractories of these furnaces have been studied via post-mortem analysis of used bricks and the observation of operational effects. Laboratory corrosion tests were also arranged to investigate the effect of slag chemistry and the mechanism of chemical corrosion . Characterization of different magnesia-carbon bricks clarified that the crystal size , type and chemistry of magnesia as well as graphite structure have the main influence on corrosion resistance. The CaO: SiO2 ratio in slag also plays a vital role in the wear of slagline refractories. The iron oxide content of slag also has a major role in graphite oxidation. Of metallurgical parameters , the electric power input and the contact time have great influence on refractories life. The results will be discussed with emphasis on particular operational factors in Mobarakeh steel plant.展开更多
To investigate the fretting wear of steel wires in hoisting ropes, specimenswere made of 6X19 point contact ropes. A model for the fretting ear was developed and a frettingwear test rig was deigned in laboratory. A se...To investigate the fretting wear of steel wires in hoisting ropes, specimenswere made of 6X19 point contact ropes. A model for the fretting ear was developed and a frettingwear test rig was deigned in laboratory. A series of experiments were performed on this test rig.The wear volume was taken as a characteristic parameter to describe the fretting wear in relation tothe contact load, reciprocating cycles and amplitude. Moreover, the wear mechanisms were discussedin the fretting process.展开更多
A new kind of friction-reducing and repairing additive containing nano-scale copper and rare earth compounds were prepared by means of synthesis and compounding methods. The performance of the said additive was invest...A new kind of friction-reducing and repairing additive containing nano-scale copper and rare earth compounds were prepared by means of synthesis and compounding methods. The performance of the said additive was investigated by engine bench test, and was compared to the performance of similar domestic and imported additives. The deterioration of lube oils containing additives over different time intervals was studied by means of plasma spectrometry and mass spectrometry, and the effect of additive package on engine power was also studied. Test results have revealed that the synthetic additive package can provide good anti-wear performance to the tribo-pairs. In particular, after 300 hour application of the said additive package the connection rod shaft and copper sleeve showed 'zero wear' to achieve the in situ dynamic repairing of tribo-pairs. Application of the said synthetic additive can effectively improve the engine power performance and extend the engine service life.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
基金the financial support from Ningbo Institute of Technology, Beihang University
文摘In recent years,the addition of Ni has been widely acknowledged to be capable of enhancing the mechanical properties of Al-Si alloys.However,the effect of Ni on the wear behaviors of Al-Si alloys and Al matrix composites,particularly at elevated temperat-ures,remains an understudied area.In this study,Al-Si-Cu-Mg-Ni/20wt%SiC particles(SiCp)composites with varying Ni contents were prepared by using a semisolid stir casting method.The effect of Ni content on the dry sliding wear behavior of the prepared compos-ites was investigated through sliding tests at 25 and 350℃.Results indicated that theθ-Al_(2)Cu phase gradually diminished and eventually disappeared as the Ni content increased from 0wt%to 3wt%.This change was accompanied by the formation and increase inδ-Al_(3)CuNi andε-Al_(3)Ni phases in microstructures.The hardness and ultimate tensile strength of the as-cast composites improved,and the wear rates of the composites decreased from 5.29×10^(−4)to 1.94×10^(−4)mm^(3)/(N∙m)at 25℃and from 20.2×10^(−4)to 7×10^(−4)mm^(3)/(N∙m)at 350℃with the increase in Ni content from 0wt%to 2wt%.The enhancement in performance was due to the presence of strengthening network structures and additional Ni-containing phases in the composites.However,the wear rate of the 3Ni composite was approximately two times higher than that of the 2Ni composite due to the fracture and debonding of theε-Al_(3)Ni phase.Abrasive wear,delamination wear,and oxidation wear were the predominant wear mechanisms of the investigated composites at 25℃,whereas delamination wear and oxid-ation wear were dominant during sliding at 350℃.
基金Project(2011CB612200)supported by the National Basic Research Program of China
文摘The friction and wear properties of Mg2B2O5 whisker reinforced 6061Al matrix composite fabricated via power ultrasonic-stir casting process were investigated using a ball-on-disk wear-testing machine against a GCr45 steel counterface under dry sliding conditions. The reinforcements include as-received Mg2B2O5 whiskers and Mg2B2O5 whiskers coated with CuO and ZnO. The volume fraction of the composites is 2%. The relationship between the wear rate and the coefficient of friction was discussed. The results indicate that the wear rate of the Mg2B2O5 whiskers coated with ZnO reinforced aluminum matrix composites is the lowest among the materials. As the applied load and sliding speed steadily increase the coefficients of friction and wear rates of the as-received matrix alloy and the fabricated composites decrease. As the applied load and sliding speed increase, the wear mechanisms of the composites shift from a mild to a severe regime.
基金Supported by the National Basic Research Program of China("973"Program)(2007CB607602)~~
文摘A simple impact-sliding wear test rig is designed for studying the wear behavior between solid materials on a repetitive normal impact accompanied with the tangential sliding. The test rig consists of a cantilever beam forced by the dynamoelectric vibration exciter and a rotational shaft driven by a spindle. It has a widely adjustable range of testing parameters, including the impact frequency, the impact load and the sliding velocity. The avail- able maximum impact frequency, impact load and sliding velocity are 100 Hz, 200 N and 4.52 m/s, respectively. To evaluate the capability of the test rig, tests are carried out and the impact load is measured. Results show that the test rig has the good repeatability under the same test conditions and the repeatable error is less than 7%. Furthermore, non-destructive examination results by the mass loss method, two-dimensional profilometry and the scanning electron microscopy (SEM) show that the test rig can meet the demands for the impact-sliding wear.
基金financially supported by the Scientific Research Fund of Si Chuan Provincial Education Department(No.17ZA0395)the Doctoral Program Foundation of Southwest University of Science and Technology(No.10zx7113)
文摘The alumina toughened zirconia(ATZ) ceramic particle reinforced gray iron matrix surface composite was successfully manufactured by pressureless infi ltration. The porous preform played a key role in the infi ltrating progress. The microstructure was observed by scanning electron microscopy(SEM); the phase constitutions was analyzed by X-ray diffraction(XRD); and the hardness and wear resistance of selected specimens were tested by hardness testing machine and abrasion testing machine, respectively. The addition of high carbon ferrochromium powders leads to the formation of white iron during solidifi cation. The wear volume loss rates of ATZ ceramic particle reinforced gray iron matrix surface composite decreases fi rst, and then tends to be stable. The wear resistance of the composite is 2.7 times higher than that of gray iron matrix. The reason is a combination of the surface hardness increase of gray iron matrix and ATZ ceramic particles and alloy carbides protecting effect on gray iron matrix.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.51474127 and 51671100)the State Key Laboratory of Metal Material for Marine Equipment and Application-University of Science and Technology Liaoning co-project,China(Nos.SKLMEA-USTL 2017010 and 201905).
文摘To simulate the wear and corrosion behavior of high-strength EH47 hull steel in a complicated marine environment in which seawater,sea ice,and sea sand coexist,accelerated wear and corrosion tests were performed in a laboratory setting using a tribometer.The effect of large loads on the behavior of abrasion and corrosion in a 3.5wt%NaCl solution with ice and sand to simulate a marine environment were investigated.The experimental results showed that the coefficient of friction(COF)decreases with increasing working load;meanwhile,the loading force and sand on the disk strongly influence the COF.The mechanisms of friction and the coupling effect of abrasion and corrosion in the 3.5wt%NaCl solution with sand were the wear and corrosion mechanisms;furthermore,the wear mechanism exerted the predominant effect.
基金financially supported within the project "Engineer of the Future.Improving the didactic potential of the Poznan University of Technology"-POKL.04.03.00-00-259/12,implemented within the Human Capital Operational Programme,co-financed by the European Union within the European Social Fundby Ministry of Science and Higher Education in Poland as a part of the 02/24/DSPB project
文摘Laser alloying was used for production of thick layers on surface of Nimonic 80A-alloy.For laser surface modification,three types of pre-coated pastes were applied:with amorphous boron,with amorphous boron and molybdenum as well as with amorphous boron and niobium.The microstructure,hardness and wear resistance of produced layers were studied in details.The presence of different types of borides in re-melted zone depended on the paste composition and caused an increase in hardness up to about HV 1000.The wear resistance was evaluated by calculation of mass wear intensity factor Imw and relative mass loss of specimen and counter-specimen.The wear behavior of the tested frictional pairs was determined by 3D interference microscopy,scanning electron microscopy equipped with EDS microanalyzer.The significant increase in abrasive wear resistance was observed in comparison to untreated Nimonic 80A-alloy.The lowest mass loss intensity factor was characteristic of laser-alloyed Nimonic 80A-alloy with boron and niobium(Imw=1.234 mg/(cm2?h)).Laser alloyed-layers indicated abrasive wear mechanism with clearly visible grooves.Laser alloying with boron and niobium resulted in the additional oxidative wear mechanism.In this case,EDS patterns revealed presence of oxygen on the worn surface of specimen.
文摘Dry sliding wear behaviour of stir-cast aluminium matrix composites(AMCs)containing LM13 alloy as matrix and ceramic particles as reinforcement was investigated.Two different ceramic particle reinforcements were used separately:synthetic ceramic particles(B_(4)C),and natural ceramic particles(ilmenite).Optical micrographs showed uniform dispersion of reinforced particles in the matrix material.Reinforced particles refined the grain size of eutectic silicon and changed its morphology to globular type.B_(4)C reinforced composites(BRCs)showed maximum improvement in hardness of AMCs.Ilmenite reinforced composites(IRCs)showed maximum reduction in coefficient of friction values due to strong matrix−reinforcement interfacial bonding caused by the formation of interfacial compounds.Dry sliding wear behaviour of composites was significantly improved as compared to base alloy.The low density and high hardness of B_(4)C particles resulted in high dislocation density around filler particles in BRCs.On the other hand,the low thermal conductivity of ilmenite particles resulted in early oxidation and formation of a tribo-layer on surface of IRCs.So,both types of reinforcements led to the improvement in wear properties of AMCs,though the mechanisms involved were very different.Thus,the low-cost ilmenite particles can be used as alternative fillers to the high-cost B_(4)C particles for processing of wear resistant composites.
基金Project(51465014)supported by the National Natural Science Foundation of ChinaProject(1099043)supported by Scientific and Technological Research Program of Guangxi,ChinaProjects(2014GXNSFAA118351,2014GXNSFAA118329,2012GXNSFBA053156)supported by the Natural Science Foundation of Guangxi,China
文摘The friction and wear properties of interpenetrating phase composites(IPC) SiC3D/Al sliding against graphite/SiC(G/SiC) composites were investigated using a sub-scale brake dynamometer. The testing conditions included a braking pressure of 1.25 MPa and an initial braking speed(IBS) of 200-350 km/h in a braking process of high-speed train according to the scale-conversion rules. The tribo-couple materials were characterized using scanning electron microscopy(SEM), X-ray diffractometry(XRD), and energy-dispersive X-ray spectrometry(EDS). It is found that the matching tribo-couple features low friction surface temperature, reliable friction factor, and high durability. The continuous lubricating mechanically-mixed layer(MML) forms gradually on the worn surfaces of ring in the friction process. The MML is heterogeneous, which greatly controls wear rate and coefficient of friction(COF) of the composites. The wear mechanism of SiC3D/Al is typically abrasive wear at an IBS of 200-300 km/h. When the IBS increases to 350 km/h, oxidation wear and delamination are observed. The friction behavior of the tribo-couple predicted using Solidwork simulation software agrees well with the experimental results. The tribo-couple meets the requirement of emergency braking of high-speed train.
基金support provided by the Central Instrument Facility Centre(CIFC)of IIT(BHU)the Department of Ceramic Engineering especially Advance Refractory Lab(ARL)of IIT(BHU)Varanasi。
文摘The microstructural features and the consequent mechanical properties were characterized in aluminium borate whisker(ABOw)(5, 10 and 15 wt.%) reinforced commercially-pure aluminium composites fabricated by conventional powder metallurgy technique. The aluminium powder and the whisker were effectively blended by a semi-powder metallurgy method. The blended powder mixtures were cold compacted and sintered at 600 ℃. The sintered composites were characterized for microstructural features by optical microscopy(OM), scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS), transmission electron microscopy(TEM) and X-ray diffraction(XRD) analysis. Porosity in the composites with variation in ABOw contents was determined. The effect of variation in content of ABOw on mechanical properties, viz. hardness, bending strength and compressive strength of the composites was evaluated. The dry sliding wear behaviour was evaluated at varying sliding distance at constant loads. Maximum flexural strength of 172 MPa and compressive strength of 324 MPa with improved hardness around HV 40.2 are obtained in composite with 10 wt.% ABOw. Further increase in ABOw content deteriorates the properties. A substantial increase in wear resistance is also observed with 10 wt.% ABOw. The excellent combination of mechanical properties of Al-10 wt.%ABOw composites is attributed to good interfacial bonds, less porosity and uniformity in the microstructure.
文摘By accurately measuring the displacement between the roller surface and the optical fiber probe relative to a null position, we can test the roller wear. The whole testing method and system were introduced. Each part of the testing system was illustrated. And also a novel fiber-optic sensor with three probes in equal transverse space is adopted. Using this sensor, the effects of fluctuations in the light source, reflectivity changing of target surface and the intensity losses in the fiber lines are automatically compensated. This method offers such advantages as non-contact, no electromagnetic interference, simplicity, low cost, high sensitivity, good accuracy and stability.
基金Supported by National Natural Science Foundation of China(Grant No.51405422)Hebei Provincial Natural Science Foundation of China(Grant No.E2015203113)Technological Innovation Fund of Aviation Industry of China(Grant No.2014E00468R)
文摘The spherical plain bearing test bench is a necessary detecting equipment in the research process of self?lubricating spherical plain bearings. The varying environmental temperatures cause the thermal deformation of the wear?depth detecting system of bearing test benches and then a ect the accuracy of the wear?depth detecting data. However, few researches about the spherical plain bearing test benches can be found with the implementation of the detect?ing error compensation. Based on the self?made modular spherical plain bearing test bench, two main causes of ther?mal errors, the friction heat of bearings and the environmental temperature variation, are analysed. The thermal errors caused by the friction heat of bearings are calculated, and the thermal deformation of the wear?depth detecting sys?tem caused by the varying environmental temperatures is detected. In view of the above results, the environmental temperature variation is the main cause of the two error factors. When the environmental temperatures rise is 10.3 °C, the thermal deformation is approximately 0.01 mm. In addition, the comprehensive compensating model of the thermal error of the wear?depth detecting system is built by multiple linear regression(MLR) and time series analysis. Compared with the detecting data of the thermal errors, the comprehensive compensating model has higher fitting precision, and the maximum residual is only 1 μm. A comprehensive compensating model of the thermal error of the wear?depth detecting system is proposed, which provides a theoretical basis for the improvement of the real?time wear?depth detecting precision of the spherical plain bearing test bench.
基金Project(51805374)supported by the National Natural Science Foundation of ChinaProject(208YFB1201603-08)supported by the Key R&D Program of Ministry of Science and Technology,China。
文摘To analyze wheel wear discrepancy between motor car and trailer of an intercity train,a novel wheel wear rates calculation model was proposed,which was composed of the intercity train dynamics model,wheel-rail three-dimensional rolling contact FEM model and the wear model.The simulated results were contrasted with measured results in field test.The simulated results showed the motor car wheels had larger rotation rate and longitudinal creepage than the trailer wheels.Meanwhile,the motor car wheels encountered larger vertical forces and longitudinal forces from bogie because of the heavier car body and the impact of traction torque.The traction torque acting on motor car wheel could increase the slip rates in the rear part of wheel contact patch and weaken the spinning phenomenon of relative slip.Larger contact pressure and slip rates caused the higher wear rates of motor car wheel than those of trailer wheel.The overall trends of wheel wear depth in simulated and tested results were similar.And they both showed the motor car wheel encountered the more serious wear than the trailer wheel.These models can be used to study the effect of the traction characteristics curves on the wear of wheel.
文摘A series of polyester, cotton, and polyester/cotton blend fabrics were evaluated in a subjective wear. Subjective trial data were correlated with the results of in-house laboratory tests with the regression methods. Experimental results indicate that clothing-comfort assessment by human perception provides a sound basis for comparison of apparel garments under combined microclimates and human-activity levels of
文摘The use of asbestos material is being avoided to manufacture the brake pads as it is harmful and toxic in nature. Further it leads to various health issues like asbestosis, mesothelioma and lung cancers. These brake pads can be replaced by natural fibers like Palm kernel (0-50%), Nile roses (0-15%) and Wheat (0-10%) with additives like aluminum oxide (5%-20%) and graphite powder (10%-35%). Phenolic resin of 35% is utilized as a binder. Particulated Nile roses are used to increase the friction coefficient and wheat powder is used to reduce the wear rate. Aluminum oxide and graphite are abrasive in nature. This helps to make brake pads with high friction co-efficient and less wear rate with low noise pollution. The wear of the proposed composites have been investigated at different speeds. Various tests like wear on pin-ondisc apparatus, hardness on the Rockwell hardness apparatus and oil absorption test have been conducted. Phenolic resin produces good bonding nature to fiber. Thus, Fibers found to have performed palatably among all commercial brake pads. The objective of the research indicates that Palm kernal shell could be a conceivable alternative for asbestos in friction coating materials.
文摘The relationships between the microstructure, the composition, the friction temperature and the form of a new kind of friction material which is a glass fibre resin friction materials (GFRF) are studied through a series of tests on machine as EPMA, STM, DTG-DTA,an optical microscope and a friction test machine. The tests show that the rising rate in temperature and the heat conductivity of GFRF are lower than that of asbestos friction material. In GFRF, the heat-decline is slowed down or even eliminated. the distribution of heat- stress is improved and the life span is extended. Raising the temperature of resin resolution and enhancing the stickness between resin and glass fibre are the two important procedures to improve the friction and wear performance of GFRF.A discription about the friction and wear mechanism of GFRF is given in this paper.
文摘Reducing wear on a side dam can prolong the casting operation life of a twin-roll strip casting process,thus reducing production cost and improving casting stability.To lengthen the service life of the side dam,it is necessary to understand the wear performance of the side dam material.To investigate the wear behavior mechanism of the side dam,in this study,the UMT-2 friction and wear tester was used to determine the relationship between the wear rate of the side-dam material and various parameters.Based on the roughness of the contact area between the side dam and the end of the casting rolls as well as on the amount of deformation of the side dam,which was derived using a thermal-deformation simulation model,the reasons for the uneven wear of the side dam were obtained.
文摘Mobarakeh Steel Company produces 3 million tons of steel annually with eight 180 tons EBT furnaces. Different types of magnesia-carbon refractories have been employed at slagline during last 5 years. In the present study the wear and corrosion of MgO-C refractories of these furnaces have been studied via post-mortem analysis of used bricks and the observation of operational effects. Laboratory corrosion tests were also arranged to investigate the effect of slag chemistry and the mechanism of chemical corrosion . Characterization of different magnesia-carbon bricks clarified that the crystal size , type and chemistry of magnesia as well as graphite structure have the main influence on corrosion resistance. The CaO: SiO2 ratio in slag also plays a vital role in the wear of slagline refractories. The iron oxide content of slag also has a major role in graphite oxidation. Of metallurgical parameters , the electric power input and the contact time have great influence on refractories life. The results will be discussed with emphasis on particular operational factors in Mobarakeh steel plant.
基金This work was financially supported by the Ministry of Coal Industry, China(the Research Foundation of Mining Science) and the L
文摘To investigate the fretting wear of steel wires in hoisting ropes, specimenswere made of 6X19 point contact ropes. A model for the fretting ear was developed and a frettingwear test rig was deigned in laboratory. A series of experiments were performed on this test rig.The wear volume was taken as a characteristic parameter to describe the fretting wear in relation tothe contact load, reciprocating cycles and amplitude. Moreover, the wear mechanisms were discussedin the fretting process.
文摘A new kind of friction-reducing and repairing additive containing nano-scale copper and rare earth compounds were prepared by means of synthesis and compounding methods. The performance of the said additive was investigated by engine bench test, and was compared to the performance of similar domestic and imported additives. The deterioration of lube oils containing additives over different time intervals was studied by means of plasma spectrometry and mass spectrometry, and the effect of additive package on engine power was also studied. Test results have revealed that the synthetic additive package can provide good anti-wear performance to the tribo-pairs. In particular, after 300 hour application of the said additive package the connection rod shaft and copper sleeve showed 'zero wear' to achieve the in situ dynamic repairing of tribo-pairs. Application of the said synthetic additive can effectively improve the engine power performance and extend the engine service life.
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.