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 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
Presentation of empirical equations for estimating engineering properties of soils is a simple, low cost and widely-used method. One of the major concerns in using these equations is evaluating their accuracy in diffe...Presentation of empirical equations for estimating engineering properties of soils is a simple, low cost and widely-used method. One of the major concerns in using these equations is evaluating their accuracy in different conditions and regions which often lead to doubts about obtained results. Most of these equations were derived in special laboratories, different climate conditions and in soils with different geotechnical and geological engineering properties and were generalized to other conditions. The main question is that whether these methods are also applicable to other conditions. Using local equations and narrowing the usage range of various methods based on each region’s properties are appropriate methods to solve these problems. This leads to simplified and faster analysis and high reliability in the obtained results. In this paper, empirical equations were derived to estimate internal friction angle, based on SPT numbers of Mashhad City’s soils in Iran, using SPT and direct shear tests results from 50 samples (25 GW and 25 GC soil samples). The results showed similar values for predicted?φ?values by SPT test and?φ?values determined by direct shear tests.展开更多
Friction spun core yarn has two components: filament core and staple fiber sheath. Under axial rubbing action, the failure mode of the core yarn is the stripping of the sheath from the core. This paper introduces a me...Friction spun core yarn has two components: filament core and staple fiber sheath. Under axial rubbing action, the failure mode of the core yarn is the stripping of the sheath from the core. This paper introduces a method to test the anti - stripping property of the core yarn. With a modified Universal Testing Machine, the stripping resistance of friction spun core yarn can be continuously measured. Some factors Influencing the measurements are discussed in detail. The testing results are compared with those from a Y731 Yarn Abrasion Tester and fur - ther confirmed by weaving practice.展开更多
Current work is focused on the influence of friction in deep drawing process. Friction measurements were also conducted using a modified tribotester based on strip sliding between tools. Four different tool surfaces w...Current work is focused on the influence of friction in deep drawing process. Friction measurements were also conducted using a modified tribotester based on strip sliding between tools. Four different tool surfaces were tested under similar contact conditions regarding contact area, normal pressure, sliding speed, lubricant and surface characteristics to calculate the friction coefficient between the tool surface and a high strength low alloy steel sheet HSLA 380. The results showed that friction coefficient varies over a wide range with different lubricating conditions and different sliding velocities. For some sliding velocities, the coefficient of friction is stable and low, while for others it is unstable and higher. Results of the experiments reveal that this novel tribotester is a very useful tool to evaluate and compare the friction between steel sheet and tool surfaces in alloyed steel for cold working applications. The outcomes have only small dispersion within the different test series, which indicates a stable process with good repeatability. The test method enables comparison of different surface finishes and treatments, lubricants and coatings in terms of friction and galling under conditions similar to those found in sheet metal forming processes. The four different types of surfaces considered for this study were grinded, polished, nitrided and quenched/tempered. The main difference among the tested tools in this work was the surface roughness, which was found to have a strong influence on friction.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
The hot deformation behavior of AA6063 aluminium alloy has been investigated by means of compression tests at temperatures between 400 and 520℃, and strain rates ranging from 2.5 to 10 s^-1. Owing to the barreling, t...The hot deformation behavior of AA6063 aluminium alloy has been investigated by means of compression tests at temperatures between 400 and 520℃, and strain rates ranging from 2.5 to 10 s^-1. Owing to the barreling, the theoretical model on the basis of Hills general method is used to calculate the flow stress of a cylindrical specimen under uniaxial simple compression so as to consider the friction effect at the die-specimen interface. A method of evaluating the friction coefficient by combining compression tests with the finite element method is presented. The real flow behavior of AA6063 aluminium alloy can be described with sinh-Arrhenius equation. The hot deformation activation energy Q derived from the corrected stress and strain data is 232. 350 kJ/mol.展开更多
Based on the ABAQUS/Explicit finite element method,the forming force changing trend of deep drawing test for 6A16 aluminum alloy plate after pre-aging and storage at room temperature for one month was simulated under ...Based on the ABAQUS/Explicit finite element method,the forming force changing trend of deep drawing test for 6A16 aluminum alloy plate after pre-aging and storage at room temperature for one month was simulated under friction coefficient ranging from 0 to 0.22.The lubricants selected for the tests were mechanical oil,butter and dry film lubricant,and the friction coefficient of these lubricants were 0.05,0.10 and 0.15,respectively.Microstructural evolution of 6 A16 aluminum alloy plate during drawing forming was investigated by OM,SEM and EBSD.The results showed that,with the increase of friction coefficient,the stress,strain and deformation degree in deformation zone increased,while the grain size in deformation zone decreased.Thus,the hardness of the cup-typed component increased with the increase of friction coefficient.Butter-lubricated cups had the highest tensile strength and yield strength after paint-bake cycle.The combination of simulation results and microstructure analysis of 6A16 aluminum alloy plate after drawing forming indicates that the appropriate lubricant is butter.展开更多
The deformation characteristic of bland in deep drawing is discussed. It is pointed out that the friction and lubrication conditions in for drawing are different from that in mechanical motion or machine work or other...The deformation characteristic of bland in deep drawing is discussed. It is pointed out that the friction and lubrication conditions in for drawing are different from that in mechanical motion or machine work or other plastic process. The common test methods in laboratories are analyzed. It shows that though all those test methods can test the friction coefficient, the probe test method is most suitable for the research of friction and lubrication and the process in deep drawing, for this method is identical with the actual work condition either from the test principle or deformation status of the blank. Last the successful application in the deep drawing simulator newly developed the the probe method are intro- duced in detail.展开更多
The present work aims to enhance the ballistic resistance of AA7005 alloy by incorporating the TiB2 and B4C ceramic reinforcement particles. Surface composites with different weight fractions of TiB2 and B4C particles...The present work aims to enhance the ballistic resistance of AA7005 alloy by incorporating the TiB2 and B4C ceramic reinforcement particles. Surface composites with different weight fractions of TiB2 and B4C particles were processed by friction stir processing. Micro-hardness and depth of penetration tests were carried out to evaluate the ballistic properties of the surface composites. The surface hardness of the composite was found to be nearly 70 HV higher than base alloy. The depth of penetration of the steel projectile was 20e26mm in the composites as compared to 37mm in the base alloy. Ballistic mass efficiency factor of the surface composite was found to be 1.6 times higher than base alloy. This is mainly attributed to the dispersion strengthening from the reinforcement particles.展开更多
A probe test method was employed to detect the friction condition of the interfaces between tools and blank. At the same time a self-developed measurement apparatus to realize the probe test method was also presented....A probe test method was employed to detect the friction condition of the interfaces between tools and blank. At the same time a self-developed measurement apparatus to realize the probe test method was also presented. Based on the analysis of force, a correlative friction model was also given. With the self-developed measurement apparatus,the effects of three kinds of lubricating oils which were in common use during the process of sheet steel drawing were studied. By probing the friction coefficient values of different lubricating oils during the drawing process of the hot-galvanized sheet steel （steel brand： ST07Zn）, we can see that the friction caused by PK oil was the lowest, so the effect of PK oil was the best. Then PK oil was used as the base lubricating oil and some solid additive powers was added into it to make a new type lubrication （named as L oil）.The result of test proved that the new lubricating oil had remarkable effect on the drawing process of hot-galvanized sheet steel.展开更多
This paper reviews 19 apparatuses having highvelocity capabilities,describes a rotary-shear low to highvelocity friction apparatus installed at Institute of Geology,China Earthquake Administration,and reports results ...This paper reviews 19 apparatuses having highvelocity capabilities,describes a rotary-shear low to highvelocity friction apparatus installed at Institute of Geology,China Earthquake Administration,and reports results from velocity-jump tests on Pingxi fault gouge to illustrate technical problems in conducting velocity-stepping tests at high velocities.The apparatus is capable of producing plate to seismic velocities（44 mm/a to 2.1 m/s for specimens of 40 mm in diameter）,using a 22 kW servomotor with a gear/belt system having three velocity ranges.A speed range can be changed by 103 or 106by using five electromagnetic clutches without stopping the motor.Two cam clutches allow fivefold velocity steps,and the motor speed can be increased from zero to 1,500 rpm in 0.1-0.2 s by changing the controlling voltage.A unique feature of the apparatus is a large specimen chamber where different specimen assemblies can be installed easily.In addition to a standard specimen assembly for friction experiments,two pressure vessels were made for pore pressures to 70 MPa;one at room temperature and the other at temperatures to 500 °C.Velocity step tests are needed to see if the framework of rate-and-state friction is applicable or not at high velocities.We report results from velocity jump tests from 1.4 mm/s to 1.4 m/s on yellowish gouge from a Pingxi fault zone,located at the northeastern part of the Longmenshan fault system that caused the 2008 Wenchuan earthquake.An instantaneous increase in friction followed by dramatic slip weakening was observed for the yellowish gouge with smooth sliding surfaces of host rock,but no instantaneous response was recognized for the same gouge with roughened sliding surfaces.Instantaneous and transient frictional properties upon velocity steps cannot be separated easily at high velocities,and technical improvements for velocity step tests are suggested.展开更多
The present study is to optimize the process parameters for friction welding of duplex stainless steel(DSS UNS S32205).Experiments were conducted according to central composite design.Process variables,as inputs of th...The present study is to optimize the process parameters for friction welding of duplex stainless steel(DSS UNS S32205).Experiments were conducted according to central composite design.Process variables,as inputs of the neural network,included friction pressure,upsetting pressure,speed and burn-off length.Tensile strength and microhardness were selected as the outputs of the neural networks.The weld metals had higher hardness and tensile strength than the base material due to grain refinement which caused failures away from the joint interface during tensile testing.Due to shorter heating time,no secondary phase intermetallic precipitation was observed in the weld joint.A multi-layer perceptron neural network was established for modeling purpose.Five various training algorithms,belonging to three classes,namely gradient descent,genetic algorithm and LevenbergeM arquardt,were used to train artificial neural network.The optimization was carried out by using particle swarm optimization method.Confirmation test was carried out by setting the optimized parameters.In conformation test,maximum tensile strength and maximum hardness obtained are 822 MPa and 322 Hv,respectively.The metallurgical investigations revealed that base metal,partially deformed zone and weld zone maintain austenite/ferrite proportion of 50:50.展开更多
Key methods developed and used in the USSR and in the Russian Federation to determine the impact and friction sensitivity of energetic materials and explosives have been discussed.Experimental methodologies and instru...Key methods developed and used in the USSR and in the Russian Federation to determine the impact and friction sensitivity of energetic materials and explosives have been discussed.Experimental methodologies and instruments that underlie the assessment of their production and handling safety have been described.Studies of a large number of compounds have revealed relationships between their sensitivity parameters and structure of individual compounds and compositions.The range of change of physical and chemical characteristics for the compounds we examined covers the entire region of their existence.Theoretical methodology and equations have been formulated to estimate the impact and friction sensitivity parameters of energetic materials and to evaluate the technological safety in use.The developed methodology is characterized by high-accuracy calculations and prediction of sensitivity parameters.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
Friction stir lap welds were produced in 3 mm thick Alclad sheets of Al alloy 2014-T4 using two different tools （with triangular and threaded taper cylindrical pins）. The effects of tool geometry on weld microstruct...Friction stir lap welds were produced in 3 mm thick Alclad sheets of Al alloy 2014-T4 using two different tools （with triangular and threaded taper cylindrical pins）. The effects of tool geometry on weld microstructure, lap-shear performance and failure mode were investigated. The pin profile was found to significantly influence the hook geometry, which in turn strongly influenced the joint strength and the failure mode. Welds produced in alloy 2014-T4 Alclad sheets by using triangular and threaded taper cylindrical tools exhibited an average lap-shear failure load of 16.5 and 19.5 kN, respectively, while the average failure load for standard riveted joints was only 3.4 kN. Welds produced in alloy 2014-T6 Alclad sheets and in alloy 2014-T4 bare sheets （i.e., no Alclad） were comparatively evaluated with those produced in alloy 2014-T4 Alclad sheets. While the welds made （with threaded taper cylindrical tool） in T6 and T4 conditions showed very similar lap-shear failure loads, the joint efficiency of the welds made in T6 condition （43%） was considerably lower （because of the higher base material strength） than those made in T4 condition （51%）. The Alclad layers were found to present no special problems in friction stir lap welding. Welds made with triangular tool in alloy 2014-T4 Alclad and bare sheets showed very similar lap-shear failure loads. The present work provides some useful insights into the use of friction stir welding for joining Al alloys in lap configuration.展开更多
The characterization of microstructure evolution in friction stir welded aluminum alloy was carried out by optical microscopy （OM） and transmission electron microscopy （TEM） and electron backscatter diffraction （...The characterization of microstructure evolution in friction stir welded aluminum alloy was carried out by optical microscopy （OM） and transmission electron microscopy （TEM） and electron backscatter diffraction （EBSD）. The weld nugget consisted of very fine equiaxed grains and experienced dissolution of nearly half of metastable precipitates into the matrix during welding. Thermomechanically affected zone （TMAZ） also experienced dissolution of precipitates but to a lesser extent whereas coarsening of precipitates was observed in heat affected zone （HAZ）. Grain boundary misorientation measurements using EBSD indicated continuous dynamic recrystallization as the underlying mechanism for the fine equiaxed nugget grains. The yield and tensile strength of the weld decreased with comparison to base material. But due to the decrease of grain size and the dissolution of second phase precipitates, an increased Charpy energy value was observed in the weld n u gget.展开更多
The physics phenomena of copper and stainless steel in the process of forming friction welding joint are recorded and observed by the interrupted test method.The test shows that the butt friction welding process of co...The physics phenomena of copper and stainless steel in the process of forming friction welding joint are recorded and observed by the interrupted test method.The test shows that the butt friction welding process of copper and stainless steel bar can be divided into three stages approximately: the adhesion at the beginning friction stage, the friction inside the copper and the plastic ring expansion, and the friction on the bound surface of copper-stainless steel and in stainless steel. During the process,the friction surface was transformed twice.展开更多
This paper describes the model tests for determining the axial friction and the lateral resistance of sand to pipeline by using fine sand and prototype pipeline, and the calculation method based on limit analysis theo...This paper describes the model tests for determining the axial friction and the lateral resistance of sand to pipeline by using fine sand and prototype pipeline, and the calculation method based on limit analysis theory is verified. The effect of cyclic loading is considered in the test.展开更多
The tensile rupture locations of friction stir welded joints of AA2017-T351 and AA6061-T6 aluminum alloys were examined. The experiments show that the rupture locations of the joints are different for the two aluminum...The tensile rupture locations of friction stir welded joints of AA2017-T351 and AA6061-T6 aluminum alloys were examined. The experiments show that the rupture locations of the joints are different for the two aluminum alloys, which are influenced by the welding parameters. When the joints are free of welding defects, the AA2017-T351 joints are ruptured in the weld nugget adjacent to the thermo-mechanically affected zone on the advancing side and the rupture surfaces appear as oval contours of the weld nugget, while the AA6061-T6 joints are ruptured in the heat affected zone on the retreating side and the rupture surfaces are inclined at a certain degree to the bottom surfaces of the joints. When welding defects are present in the joints, the AA2017-T351 joints are ruptured in the weld center, while the AA6061-T6 joints are ruptured on the retreating side near the weld center. The rupture locations of the joints are dependent on the internal structures of the joints and can be explained through them.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 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Presentation of empirical equations for estimating engineering properties of soils is a simple, low cost and widely-used method. One of the major concerns in using these equations is evaluating their accuracy in different conditions and regions which often lead to doubts about obtained results. Most of these equations were derived in special laboratories, different climate conditions and in soils with different geotechnical and geological engineering properties and were generalized to other conditions. The main question is that whether these methods are also applicable to other conditions. Using local equations and narrowing the usage range of various methods based on each region’s properties are appropriate methods to solve these problems. This leads to simplified and faster analysis and high reliability in the obtained results. In this paper, empirical equations were derived to estimate internal friction angle, based on SPT numbers of Mashhad City’s soils in Iran, using SPT and direct shear tests results from 50 samples (25 GW and 25 GC soil samples). The results showed similar values for predicted?φ?values by SPT test and?φ?values determined by direct shear tests.
文摘Friction spun core yarn has two components: filament core and staple fiber sheath. Under axial rubbing action, the failure mode of the core yarn is the stripping of the sheath from the core. This paper introduces a method to test the anti - stripping property of the core yarn. With a modified Universal Testing Machine, the stripping resistance of friction spun core yarn can be continuously measured. Some factors Influencing the measurements are discussed in detail. The testing results are compared with those from a Y731 Yarn Abrasion Tester and fur - ther confirmed by weaving practice.
文摘Current work is focused on the influence of friction in deep drawing process. Friction measurements were also conducted using a modified tribotester based on strip sliding between tools. Four different tool surfaces were tested under similar contact conditions regarding contact area, normal pressure, sliding speed, lubricant and surface characteristics to calculate the friction coefficient between the tool surface and a high strength low alloy steel sheet HSLA 380. The results showed that friction coefficient varies over a wide range with different lubricating conditions and different sliding velocities. For some sliding velocities, the coefficient of friction is stable and low, while for others it is unstable and higher. Results of the experiments reveal that this novel tribotester is a very useful tool to evaluate and compare the friction between steel sheet and tool surfaces in alloyed steel for cold working applications. The outcomes have only small dispersion within the different test series, which indicates a stable process with good repeatability. The test method enables comparison of different surface finishes and treatments, lubricants and coatings in terms of friction and galling under conditions similar to those found in sheet metal forming processes. The four different types of surfaces considered for this study were grinded, polished, nitrided and quenched/tempered. The main difference among the tested tools in this work was the surface roughness, which was found to have a strong influence on friction.
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.
基金supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars of Shanxi Province of China (No.9835).
文摘The hot deformation behavior of AA6063 aluminium alloy has been investigated by means of compression tests at temperatures between 400 and 520℃, and strain rates ranging from 2.5 to 10 s^-1. Owing to the barreling, the theoretical model on the basis of Hills general method is used to calculate the flow stress of a cylindrical specimen under uniaxial simple compression so as to consider the friction effect at the die-specimen interface. A method of evaluating the friction coefficient by combining compression tests with the finite element method is presented. The real flow behavior of AA6063 aluminium alloy can be described with sinh-Arrhenius equation. The hot deformation activation energy Q derived from the corrected stress and strain data is 232. 350 kJ/mol.
基金Funded by the National Key Research and Development Program of China(No.2016YFB0300805).
文摘Based on the ABAQUS/Explicit finite element method,the forming force changing trend of deep drawing test for 6A16 aluminum alloy plate after pre-aging and storage at room temperature for one month was simulated under friction coefficient ranging from 0 to 0.22.The lubricants selected for the tests were mechanical oil,butter and dry film lubricant,and the friction coefficient of these lubricants were 0.05,0.10 and 0.15,respectively.Microstructural evolution of 6 A16 aluminum alloy plate during drawing forming was investigated by OM,SEM and EBSD.The results showed that,with the increase of friction coefficient,the stress,strain and deformation degree in deformation zone increased,while the grain size in deformation zone decreased.Thus,the hardness of the cup-typed component increased with the increase of friction coefficient.Butter-lubricated cups had the highest tensile strength and yield strength after paint-bake cycle.The combination of simulation results and microstructure analysis of 6A16 aluminum alloy plate after drawing forming indicates that the appropriate lubricant is butter.
文摘The deformation characteristic of bland in deep drawing is discussed. It is pointed out that the friction and lubrication conditions in for drawing are different from that in mechanical motion or machine work or other plastic process. The common test methods in laboratories are analyzed. It shows that though all those test methods can test the friction coefficient, the probe test method is most suitable for the research of friction and lubrication and the process in deep drawing, for this method is identical with the actual work condition either from the test principle or deformation status of the blank. Last the successful application in the deep drawing simulator newly developed the the probe method are intro- duced in detail.
基金supported by Defence Institute of Advanced Technology(DIAT),Pune(DIAT-In house Project)
文摘The present work aims to enhance the ballistic resistance of AA7005 alloy by incorporating the TiB2 and B4C ceramic reinforcement particles. Surface composites with different weight fractions of TiB2 and B4C particles were processed by friction stir processing. Micro-hardness and depth of penetration tests were carried out to evaluate the ballistic properties of the surface composites. The surface hardness of the composite was found to be nearly 70 HV higher than base alloy. The depth of penetration of the steel projectile was 20e26mm in the composites as compared to 37mm in the base alloy. Ballistic mass efficiency factor of the surface composite was found to be 1.6 times higher than base alloy. This is mainly attributed to the dispersion strengthening from the reinforcement particles.
文摘A probe test method was employed to detect the friction condition of the interfaces between tools and blank. At the same time a self-developed measurement apparatus to realize the probe test method was also presented. Based on the analysis of force, a correlative friction model was also given. With the self-developed measurement apparatus,the effects of three kinds of lubricating oils which were in common use during the process of sheet steel drawing were studied. By probing the friction coefficient values of different lubricating oils during the drawing process of the hot-galvanized sheet steel （steel brand： ST07Zn）, we can see that the friction caused by PK oil was the lowest, so the effect of PK oil was the best. Then PK oil was used as the base lubricating oil and some solid additive powers was added into it to make a new type lubrication （named as L oil）.The result of test proved that the new lubricating oil had remarkable effect on the drawing process of hot-galvanized sheet steel.
基金supported by State Key Laboratory of Earthquake Dynamics (Project No.LED2014A06 & LED2010A05)
文摘This paper reviews 19 apparatuses having highvelocity capabilities,describes a rotary-shear low to highvelocity friction apparatus installed at Institute of Geology,China Earthquake Administration,and reports results from velocity-jump tests on Pingxi fault gouge to illustrate technical problems in conducting velocity-stepping tests at high velocities.The apparatus is capable of producing plate to seismic velocities（44 mm/a to 2.1 m/s for specimens of 40 mm in diameter）,using a 22 kW servomotor with a gear/belt system having three velocity ranges.A speed range can be changed by 103 or 106by using five electromagnetic clutches without stopping the motor.Two cam clutches allow fivefold velocity steps,and the motor speed can be increased from zero to 1,500 rpm in 0.1-0.2 s by changing the controlling voltage.A unique feature of the apparatus is a large specimen chamber where different specimen assemblies can be installed easily.In addition to a standard specimen assembly for friction experiments,two pressure vessels were made for pore pressures to 70 MPa;one at room temperature and the other at temperatures to 500 °C.Velocity step tests are needed to see if the framework of rate-and-state friction is applicable or not at high velocities.We report results from velocity jump tests from 1.4 mm/s to 1.4 m/s on yellowish gouge from a Pingxi fault zone,located at the northeastern part of the Longmenshan fault system that caused the 2008 Wenchuan earthquake.An instantaneous increase in friction followed by dramatic slip weakening was observed for the yellowish gouge with smooth sliding surfaces of host rock,but no instantaneous response was recognized for the same gouge with roughened sliding surfaces.Instantaneous and transient frictional properties upon velocity steps cannot be separated easily at high velocities,and technical improvements for velocity step tests are suggested.
文摘The present study is to optimize the process parameters for friction welding of duplex stainless steel(DSS UNS S32205).Experiments were conducted according to central composite design.Process variables,as inputs of the neural network,included friction pressure,upsetting pressure,speed and burn-off length.Tensile strength and microhardness were selected as the outputs of the neural networks.The weld metals had higher hardness and tensile strength than the base material due to grain refinement which caused failures away from the joint interface during tensile testing.Due to shorter heating time,no secondary phase intermetallic precipitation was observed in the weld joint.A multi-layer perceptron neural network was established for modeling purpose.Five various training algorithms,belonging to three classes,namely gradient descent,genetic algorithm and LevenbergeM arquardt,were used to train artificial neural network.The optimization was carried out by using particle swarm optimization method.Confirmation test was carried out by setting the optimized parameters.In conformation test,maximum tensile strength and maximum hardness obtained are 822 MPa and 322 Hv,respectively.The metallurgical investigations revealed that base metal,partially deformed zone and weld zone maintain austenite/ferrite proportion of 50:50.
文摘Key methods developed and used in the USSR and in the Russian Federation to determine the impact and friction sensitivity of energetic materials and explosives have been discussed.Experimental methodologies and instruments that underlie the assessment of their production and handling safety have been described.Studies of a large number of compounds have revealed relationships between their sensitivity parameters and structure of individual compounds and compositions.The range of change of physical and chemical characteristics for the compounds we examined covers the entire region of their existence.Theoretical methodology and equations have been formulated to estimate the impact and friction sensitivity parameters of energetic materials and to evaluate the technological safety in use.The developed methodology is characterized by high-accuracy calculations and prediction of sensitivity parameters.
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the Indian Space Research Organization (ISRO) for providing financial support forcarrying out this work
文摘Friction stir lap welds were produced in 3 mm thick Alclad sheets of Al alloy 2014-T4 using two different tools （with triangular and threaded taper cylindrical pins）. The effects of tool geometry on weld microstructure, lap-shear performance and failure mode were investigated. The pin profile was found to significantly influence the hook geometry, which in turn strongly influenced the joint strength and the failure mode. Welds produced in alloy 2014-T4 Alclad sheets by using triangular and threaded taper cylindrical tools exhibited an average lap-shear failure load of 16.5 and 19.5 kN, respectively, while the average failure load for standard riveted joints was only 3.4 kN. Welds produced in alloy 2014-T6 Alclad sheets and in alloy 2014-T4 bare sheets （i.e., no Alclad） were comparatively evaluated with those produced in alloy 2014-T4 Alclad sheets. While the welds made （with threaded taper cylindrical tool） in T6 and T4 conditions showed very similar lap-shear failure loads, the joint efficiency of the welds made in T6 condition （43%） was considerably lower （because of the higher base material strength） than those made in T4 condition （51%）. The Alclad layers were found to present no special problems in friction stir lap welding. Welds made with triangular tool in alloy 2014-T4 Alclad and bare sheets showed very similar lap-shear failure loads. The present work provides some useful insights into the use of friction stir welding for joining Al alloys in lap configuration.
文摘The characterization of microstructure evolution in friction stir welded aluminum alloy was carried out by optical microscopy （OM） and transmission electron microscopy （TEM） and electron backscatter diffraction （EBSD）. The weld nugget consisted of very fine equiaxed grains and experienced dissolution of nearly half of metastable precipitates into the matrix during welding. Thermomechanically affected zone （TMAZ） also experienced dissolution of precipitates but to a lesser extent whereas coarsening of precipitates was observed in heat affected zone （HAZ）. Grain boundary misorientation measurements using EBSD indicated continuous dynamic recrystallization as the underlying mechanism for the fine equiaxed nugget grains. The yield and tensile strength of the weld decreased with comparison to base material. But due to the decrease of grain size and the dissolution of second phase precipitates, an increased Charpy energy value was observed in the weld n u gget.
文摘The physics phenomena of copper and stainless steel in the process of forming friction welding joint are recorded and observed by the interrupted test method.The test shows that the butt friction welding process of copper and stainless steel bar can be divided into three stages approximately: the adhesion at the beginning friction stage, the friction inside the copper and the plastic ring expansion, and the friction on the bound surface of copper-stainless steel and in stainless steel. During the process,the friction surface was transformed twice.
文摘This paper describes the model tests for determining the axial friction and the lateral resistance of sand to pipeline by using fine sand and prototype pipeline, and the calculation method based on limit analysis theory is verified. The effect of cyclic loading is considered in the test.
文摘The tensile rupture locations of friction stir welded joints of AA2017-T351 and AA6061-T6 aluminum alloys were examined. The experiments show that the rupture locations of the joints are different for the two aluminum alloys, which are influenced by the welding parameters. When the joints are free of welding defects, the AA2017-T351 joints are ruptured in the weld nugget adjacent to the thermo-mechanically affected zone on the advancing side and the rupture surfaces appear as oval contours of the weld nugget, while the AA6061-T6 joints are ruptured in the heat affected zone on the retreating side and the rupture surfaces are inclined at a certain degree to the bottom surfaces of the joints. When welding defects are present in the joints, the AA2017-T351 joints are ruptured in the weld center, while the AA6061-T6 joints are ruptured on the retreating side near the weld center. The rupture locations of the joints are dependent on the internal structures of the joints and can be explained through them.
