In the aerospace field,hole burnishing enhancement plays an essential role in improving the service performance of load-bearing holes.To satisfy the assembly accuracy and strength requirements,the structure shape and ...In the aerospace field,hole burnishing enhancement plays an essential role in improving the service performance of load-bearing holes.To satisfy the assembly accuracy and strength requirements,the structure shape and surface integrity must be considered simultaneously during the enhancement process.The current manufacturing process of hole burnishing has a relatively weak balance between the structure shape and surface integrity;therefore,it is necessary to analyze the mechanism and optimize the parameters to improve the strengthening effect of the holes.In this study,a two-dimensional longitudinal simplified model for the hole burnishing process was established,and the reasons for the surface roughness improvement of the hole wall and material accumulation on the upper surface were analyzed.Experiments were conducted to determine the influence of the burnishing parameters on the structure shape(material accumulation,shape contour,and roundness)and surface integrity(surface roughness,residual stress,and surface hardness),based on the opposite requirements of improving the structure shape and surface integrity for the burnishing depth(BD).The results showed that with an increase in the BD,the structure shape deteriorated,whereas the surface integrity improved.Fatigue behavior verification experiments were conducted,and parameter selection schemes for the collaborative improvement of the structure shape and surface integrity were discussed.For the holes of titanium alloy TB6(Ti-10V-2Fe-3Al),the fatigue life can be increased by 162%when the BD,spindle speed,and feed rate were 0.20 mm,200 r/min,and 0.2 mm/r,respectively.展开更多
In order to investigate a gradient nano/micro-structured surface layer on pure copper produced by severe plasticity roller burnishing （SPRB） and grain refinement mechanism, the microstructure characteristics and mat...In order to investigate a gradient nano/micro-structured surface layer on pure copper produced by severe plasticity roller burnishing （SPRB） and grain refinement mechanism, the microstructure characteristics and material properties of sample at various depths from the topmost surface were investigated by SEM, TEM, XRD, OM etc. The experimental results show that the gradient nano/micro-structure was introduced into the surface layer of over 100μm in thickness. The remarkable increase in hardness near the topmost surface was mainly attributed to the reduced grain size. The equiaxed nano-sized grains were in random orientation and the most of their boundaries were low-angle grain boundaries （LAGBs）. The coarse grains are refined into the few micro-sized grains by dislocation activities;deformation twinning was found to be the primary form for the formation of submicron grains;the formation of nanostructure was dominated by dislocation activities accompanied with rotation of grains in local region.展开更多
Ball burnishing is a plastic deformation process used as a surface smoothing and surface improvement finishing treatment after turning or milling processes. This process changes the surface stereometrics of the previo...Ball burnishing is a plastic deformation process used as a surface smoothing and surface improvement finishing treatment after turning or milling processes. This process changes the surface stereometrics of the previously machining surface. Burnishing with hydrostatic tools can be easily and effectively used on both conventional and Computer Numeric Control(CNC) machines. The existing research of the burnishing process mainly focuses on the functional surface characterization, for example, surface roughness, wear resistance, surface layer hardness, etc. There is a lack of references reporting a detailed analysis of 3D parameters calculation with a mathematical model to evaluate the results of the ball burnishing. This paper presents the effect of ball burnishing process parameters with hydrostatic tools on the resulting surface structure geometry. The surface topography parameters were calculated using the Taly Map software. Studies were conducted based on Hartley’s static, determined plan. Such a plan can be built on a hypersphere or hypercube. In this work, a hypercube was used. In the case of Hartley’s plan makes it possible to define the regression equation in the form of a polynomial of the second degree. The input process parameters considered in this study include the burnishing rate, applied pressure, and line-to-line pitch. The significant influence of these parameters was confirmed and described as a mathematical power model. The results also showed a positive effect of hydrostatic burnishing on the roughness and geometric structure of the surface.展开更多
A novel two-dimensional ultrasonic surface burnishing process(2D-USBP)is proposed.7075-T6 aluminum samples are processed by a custom-designed 2D-USBP setup.Parameter optimization of 2D-USBP is conducted to determine t...A novel two-dimensional ultrasonic surface burnishing process(2D-USBP)is proposed.7075-T6 aluminum samples are processed by a custom-designed 2D-USBP setup.Parameter optimization of 2D-USBP is conducted to determine the best processing strategy of 7075-T6 aluminum.A uniform design method is utilized to optimize the 2D-USBP process.U〔3(133)and 4(72)tables are established to conduct parameter optimization.Burnishing depth,spindle speed,and feed rate are taken as the control parameters.The surface roughness and Vickers hardness are taken as the evaluation indicators.It establishes the active control models for surface quality.Dry wear tests are conducted to compare the wear-resistance of the 2D-USBP treated sample and the original sample.Results show that the machining quality of 2D-USBP is best under 0.24 mm burnishing depth,5000 r/min spindle speed,and 25 mm/min feed rate.The surface roughness of the sample is reduced from 2517.758 to 50.878 nm,and the hardness of the sample surface is improved from 167 to 252 HV.Under the lower load,the wear mechanism of the 2D-USBP treated sample is mainly abrasive wear accompanied by delamination wear,while the wear mechanism of the original sample is mainly delamination wear.Under the higher load,the accumulation of frictional heat on the sample surface transforms the wear mechanisms of the original and the 2D-USBP treated samples into thermal wear.展开更多
Ball burnishing routine permits through a simple,fast and economical manner to obtain free chip on the manufactured parts.It generates a superior surface finish by rotating a ball tool against a workpiece.The burnishi...Ball burnishing routine permits through a simple,fast and economical manner to obtain free chip on the manufactured parts.It generates a superior surface finish by rotating a ball tool against a workpiece.The burnishing process is commonly developed in industry in order to improve the surface quality,which is a critical issue in the manufacturing sector.An experimental study were carried out to determine the best surface quality for magnesium alloy subjected to d iff ere ni medium.Burnishing of magnesium alloy was performed varying four different mediums and combining different burnishing parameters.To design the experiment were used the classical Taguchi method through which were developed the L16 orthogonal array.This strategy allowed to detect the driving parameters that generate the best surface roughness value by computing the signal-to-noise ratio.The driving parameters values for this study are 400 N(force),0.05 mm/min(feed rate),three number of passes and boron oil as medium.The results are paramount important for designing heavy parts used in transportation vehicles such as automobiles,airplanes,high-speed trains etc.展开更多
Burnishing experiments with different burnishing parameters were performed on a computer numerical control milling machine to characterize the surface roughness of an aluminum alloy during burnishing.The chaos theory ...Burnishing experiments with different burnishing parameters were performed on a computer numerical control milling machine to characterize the surface roughness of an aluminum alloy during burnishing.The chaos theory was employed to investigate the nonlinear features of the burnishing system.The experimental results show that the power spectrum is broadband and continuous,and the Lyapunov exponentλis positive,proving that burnishing has chaotic characteristics.The chaotic characteristic parameter,the correlation dimension D,is sensitive to the time behavior of the system and is used to establish the corresponding relationship with the surface roughness.The correlation dimension was the largest,when the surface roughness was the smallest.Furthermore,when the correlation dimension curve decreases,the roughness curve increases.The correlation dimension and surface roughness exhibit opposite variation trends.The higher the correlation dimension,the lower the surface roughness.The surface roughness of the aluminum alloy can be characterized online by calculating the correlation dimension during burnishing.展开更多
Burnishing is a profitable process of surface finishing due to its ability to be automated,which makes burnishing method more desirable than other finishing methods.To obtain high surface finish,non-stop operation is ...Burnishing is a profitable process of surface finishing due to its ability to be automated,which makes burnishing method more desirable than other finishing methods.To obtain high surface finish,non-stop operation is required for CNC machine and we can attain that by choosing a suitable trajectory of the finishing tool.In other words,burnishing paths should be multidirectional rather than monotonic,in order to cover uniformly the surface.Indeed,the burnishing force is also a key parameter of the burnishing process because it determines the degree of plastic deformation,and that makes determining the optimum burnishing force an essential step of the burnishing process a success.Therefore,we consider the strategy of ball burnishing path and the burnishing force as variable parameters in this study.In this paper,we propose a new strategy of burnishing tool path with trochoid cycles that achieves a multidirectional burnishing of the surface according to various patterns.Taking into consideration the optimum burnishing force,to improve flat surface finish of AL6061-O samples by reducing the surface roughness parameter(Rz).Experiments carried out on 3-axis milling machine show that the proposed trochoidal path is more effective than the conventional one.展开更多
Slide burnishing process, which is a surface severe plastic deformation technique, offers an attractive post-machining alternative due to its chip-less and relatively simple operations. The purpose of the present work...Slide burnishing process, which is a surface severe plastic deformation technique, offers an attractive post-machining alternative due to its chip-less and relatively simple operations. The purpose of the present work is to investigate effects of initial turned surface roughness on the burnished surface roughness and hardness in slide burnishing. The carbon steel samples those have different roughness surfaces being treated were prepared by turning by varying the feed. Slide burnishing was then carried out by a silicon nitride ceramic ball that was loaded and fed on the turned surface of a rotating specimen using a lathe machine. It was found that the turned surfaces were smoothed drastically by the burnishing process, and that the Ra and Rz values were reduced at most by a factor of 52 and 21, respectively. However, the smoothing effect of burnishing has limit, and the limited maximum height roughness (Rz*) for burnishing smoothing increased under a higher burnishing force and with a larger ball diameter. When the Rz values of initial turned surfaces were less than the Rz*, the roughness of the burnished surfaces did not depend on the roughness of the initial turned surface and the burnishing force. There was no significant difference in the burnished microstructure and hardness under a specific burnishing force among the initial turned surface roughness, while a higher burnishing force caused a greater increase in surface hardness.展开更多
Cold Metal Transfer-Based Wire Arc Directed Energy Deposition(CMT-WA-DED)presents a promising avenue for the rapid fabrication of components crucial to automotive,shipbuilding,and aerospace industries.However,the susc...Cold Metal Transfer-Based Wire Arc Directed Energy Deposition(CMT-WA-DED)presents a promising avenue for the rapid fabrication of components crucial to automotive,shipbuilding,and aerospace industries.However,the susceptibility to fatigue of CMT-WA-DED-produced AZ31 Mg alloy components has impeded their widespread adoption for critical load-bearing applications.In this study,a comprehensive investigation into the fatigue behaviour of WA-DED-fabricated AZ31 Mg alloy has been carried out and compared to commercially available wrought AZ31 alloy.Our findings indicate that the as-deposited parts exhibit a lower fatigue life than wrought Mg alloy,primarily due to poor surface finish,tensile residual stress,porosity,and coarse grain microstructure inherent in the WA-DED process.Low Plasticity Burnishing(LPB)treatment is applied to mitigate these issues,which induce significant plastic deformation on the surface.This treatment resulted in a remarkable improvement of fatigue life by 42%,accompanied by a reduction in surface roughness,grain refinement and enhancement of compressive residual stress levels.Furthermore,during cyclic deformation,WA-DED specimens exhibited higher plasticity and dislocation density compared to both wrought and WA-DED+LPB specimens.A higher fraction of Low Angle Grain Boundaries(LAGBs)in WA-DED specimens contributed to multiple crack initiation sites and convoluted crack paths,ultimately leading to premature failure.In contrast,wrought and WA-DED+LPB specimens displayed a higher percentage of High Angle Grain Boundaries(HAGBs),which hindered dislocation movement and resulted in fewer crack initiation sites and less complex crack paths,thereby extending fatigue life.These findings underscore the effectiveness of LPB as a post-processing technique to enhance the fatigue performance of WA-DED-fabricated AZ31 Mg alloy components.Our study highlights the importance of LPB surface treatment on AZ31 Mg components produced by CMT-WA-DED to remove surface defects,enabling their widespread use in load-bearing applications.展开更多
Microtextured surfaces,such as those with groove,hole,or protrusion structures,are widely used in various industries for bonding dissimilar materials because of their anchor effect,which enhances adhesion and penetrat...Microtextured surfaces,such as those with groove,hole,or protrusion structures,are widely used in various industries for bonding dissimilar materials because of their anchor effect,which enhances adhesion and penetration with other materials.Although surfaces with grooves and protrusions are expected to show higher bonding strength,it is difficult to fabricate such hybrid structures using a material removal process or additive manufacturing.This study established a new burnishing method using a tool with preformed microgrooves at the tip to fabricate groove-with-protrusion structures on metal surfaces by plastic deformation.The tip of a ball-shaped polycrystalline diamond(PCD)tool was irradiated with a femtosecond pulsed laser to generate multiple trapezoid ten-micron scale grooves.Burnishing was then conducted on an oxygen-free copper surface to investigate the characteristics and mechanism of the burnishing-induced plastic deformation behaviors.The results showed that protrusions and grooves,which were several tens of micrometers in height and depth,were simultaneously produced along the tool path on the material surface.Tool sliding on the workpiece induced shear stress,which mainly triggered dislocation movement and plastic deformation enhancement.Cross-sectional observation revealed that grain elongation and refinement remarkably increased with the burnishing depth,indicating that the shear stress from burnishing produced refined grains that flowed and formed the protrusions.This research demonstrates the feasibility of a highly efficient method for simultaneously generating groove-with-protrusion structures with enhanced surface properties.展开更多
A texturing technique is proposed in which a burnishing tool with a hemispherical tip intermittently contacts a target surface,inducing plastic fow in the surface material to generate a periodic microtopography.The me...A texturing technique is proposed in which a burnishing tool with a hemispherical tip intermittently contacts a target surface,inducing plastic fow in the surface material to generate a periodic microtopography.The mechanism underlying texture formation in the intermittent burnishing process is elucidated,and the fuctional viability of the resulting textured surface is assessed through friction and wear tests.The burnishing tool with a hemispherical tip was rotated eccentrically from the spindle of a fve-axis machining center,facilitating intermittent plastic deformation of the target surface material over multiple tool rotations,thereby producing fne dimples on the surface.Burnishing experiments on an aluminum alloy revealed the efects of tool tip radius and eccentricity on the resulting texture morphology.The dimpled texture produced by a single tool-surface contact exhibited an elliptical shape,with ellipticity controlled by the tool tip radius and eccentricity.The mechanism governing textured surface formation through plastic fow was elucidated by creating overlapping textured regions at equal pitch intervals.High compressive residual stresses were induced on the textured surface.Friction and wear tests using the ball-on-disk method demonstrated that textured surfaces,created under optimized burnishing conditions efectively mitigated the aggressiveness of the sliding mating material.展开更多
The fracture morphologies of several advanced high-strength steels （DP590, DP780, DP980, Ml180, and M1300） formed in uniaxial tension and piercing were observed by scanning electron microscope, and then quantitative...The fracture morphologies of several advanced high-strength steels （DP590, DP780, DP980, Ml180, and M1300） formed in uniaxial tension and piercing were observed by scanning electron microscope, and then quantitatively analyzed by image processing technique. The tension-induced fractographs are dominated by obvious uniform or bimodal size dimples, while shearing-induced fractographs have smooth surfaces and few dimples. The fracture zone of higher grade DP steels is smoother. As for M1180 and M1300, the fracture zones consist of very small dimples and smooth brittle surfaces. The dimple size of M1300（ ,- 1.2 tm） is smaller than that of M1180（ 1.6 tm）. Moreover, in the tensile fracture, the quantitative correlation between average dimple diameter （d） and tensile strength （a） can be represented by d = 10,502.32a-121. However, the relation between dimple density and tensile strength is not monotonic due to the appearance of bimodal size dimples with increase of tensile strength. For shearing-induced fracture during piercing, the fitted empirical model between the percentage of burnish zone （f） and tensile strength can be described asf --- 239.9a-＇36.展开更多
文摘In the aerospace field,hole burnishing enhancement plays an essential role in improving the service performance of load-bearing holes.To satisfy the assembly accuracy and strength requirements,the structure shape and surface integrity must be considered simultaneously during the enhancement process.The current manufacturing process of hole burnishing has a relatively weak balance between the structure shape and surface integrity;therefore,it is necessary to analyze the mechanism and optimize the parameters to improve the strengthening effect of the holes.In this study,a two-dimensional longitudinal simplified model for the hole burnishing process was established,and the reasons for the surface roughness improvement of the hole wall and material accumulation on the upper surface were analyzed.Experiments were conducted to determine the influence of the burnishing parameters on the structure shape(material accumulation,shape contour,and roundness)and surface integrity(surface roughness,residual stress,and surface hardness),based on the opposite requirements of improving the structure shape and surface integrity for the burnishing depth(BD).The results showed that with an increase in the BD,the structure shape deteriorated,whereas the surface integrity improved.Fatigue behavior verification experiments were conducted,and parameter selection schemes for the collaborative improvement of the structure shape and surface integrity were discussed.For the holes of titanium alloy TB6(Ti-10V-2Fe-3Al),the fatigue life can be increased by 162%when the BD,spindle speed,and feed rate were 0.20 mm,200 r/min,and 0.2 mm/r,respectively.
基金Project(50975095)supported by the National Natural Science Foundation of ChinaProject(2012ZM0048)supported by the Fundamental Research Funds for the Central Universities,China
文摘In order to investigate a gradient nano/micro-structured surface layer on pure copper produced by severe plasticity roller burnishing （SPRB） and grain refinement mechanism, the microstructure characteristics and material properties of sample at various depths from the topmost surface were investigated by SEM, TEM, XRD, OM etc. The experimental results show that the gradient nano/micro-structure was introduced into the surface layer of over 100μm in thickness. The remarkable increase in hardness near the topmost surface was mainly attributed to the reduced grain size. The equiaxed nano-sized grains were in random orientation and the most of their boundaries were low-angle grain boundaries （LAGBs）. The coarse grains are refined into the few micro-sized grains by dislocation activities;deformation twinning was found to be the primary form for the formation of submicron grains;the formation of nanostructure was dominated by dislocation activities accompanied with rotation of grains in local region.
文摘Ball burnishing is a plastic deformation process used as a surface smoothing and surface improvement finishing treatment after turning or milling processes. This process changes the surface stereometrics of the previously machining surface. Burnishing with hydrostatic tools can be easily and effectively used on both conventional and Computer Numeric Control(CNC) machines. The existing research of the burnishing process mainly focuses on the functional surface characterization, for example, surface roughness, wear resistance, surface layer hardness, etc. There is a lack of references reporting a detailed analysis of 3D parameters calculation with a mathematical model to evaluate the results of the ball burnishing. This paper presents the effect of ball burnishing process parameters with hydrostatic tools on the resulting surface structure geometry. The surface topography parameters were calculated using the Taly Map software. Studies were conducted based on Hartley’s static, determined plan. Such a plan can be built on a hypersphere or hypercube. In this work, a hypercube was used. In the case of Hartley’s plan makes it possible to define the regression equation in the form of a polynomial of the second degree. The input process parameters considered in this study include the burnishing rate, applied pressure, and line-to-line pitch. The significant influence of these parameters was confirmed and described as a mathematical power model. The results also showed a positive effect of hydrostatic burnishing on the roughness and geometric structure of the surface.
基金Supportedby National Natural Science Foundation of China(Grant Nos.51675483,51705028)Fundamental Research Funds for the Provincial Universities of Zhejiang(Grant No.RF-A2019008)Foundations(Grant Nos.61409230606,EM2015042003).
文摘A novel two-dimensional ultrasonic surface burnishing process(2D-USBP)is proposed.7075-T6 aluminum samples are processed by a custom-designed 2D-USBP setup.Parameter optimization of 2D-USBP is conducted to determine the best processing strategy of 7075-T6 aluminum.A uniform design method is utilized to optimize the 2D-USBP process.U〔3(133)and 4(72)tables are established to conduct parameter optimization.Burnishing depth,spindle speed,and feed rate are taken as the control parameters.The surface roughness and Vickers hardness are taken as the evaluation indicators.It establishes the active control models for surface quality.Dry wear tests are conducted to compare the wear-resistance of the 2D-USBP treated sample and the original sample.Results show that the machining quality of 2D-USBP is best under 0.24 mm burnishing depth,5000 r/min spindle speed,and 25 mm/min feed rate.The surface roughness of the sample is reduced from 2517.758 to 50.878 nm,and the hardness of the sample surface is improved from 167 to 252 HV.Under the lower load,the wear mechanism of the 2D-USBP treated sample is mainly abrasive wear accompanied by delamination wear,while the wear mechanism of the original sample is mainly delamination wear.Under the higher load,the accumulation of frictional heat on the sample surface transforms the wear mechanisms of the original and the 2D-USBP treated samples into thermal wear.
文摘Ball burnishing routine permits through a simple,fast and economical manner to obtain free chip on the manufactured parts.It generates a superior surface finish by rotating a ball tool against a workpiece.The burnishing process is commonly developed in industry in order to improve the surface quality,which is a critical issue in the manufacturing sector.An experimental study were carried out to determine the best surface quality for magnesium alloy subjected to d iff ere ni medium.Burnishing of magnesium alloy was performed varying four different mediums and combining different burnishing parameters.To design the experiment were used the classical Taguchi method through which were developed the L16 orthogonal array.This strategy allowed to detect the driving parameters that generate the best surface roughness value by computing the signal-to-noise ratio.The driving parameters values for this study are 400 N(force),0.05 mm/min(feed rate),three number of passes and boron oil as medium.The results are paramount important for designing heavy parts used in transportation vehicles such as automobiles,airplanes,high-speed trains etc.
基金National Natural Science Foundation of China(Grant Nos.52175194,52105215,52075047)Zhejiang Provincial Natural Science Foundation of China(LR23E050002)+1 种基金Fundamental Research Funds for the Provincial Universities of Zhejiang(Grant No.RF-A2019008)Key Laboratory of E&M(Zhejiang University of Technology),Ministry of Education&Zhejiang Province(Grant No.EM2021120103)。
文摘Burnishing experiments with different burnishing parameters were performed on a computer numerical control milling machine to characterize the surface roughness of an aluminum alloy during burnishing.The chaos theory was employed to investigate the nonlinear features of the burnishing system.The experimental results show that the power spectrum is broadband and continuous,and the Lyapunov exponentλis positive,proving that burnishing has chaotic characteristics.The chaotic characteristic parameter,the correlation dimension D,is sensitive to the time behavior of the system and is used to establish the corresponding relationship with the surface roughness.The correlation dimension was the largest,when the surface roughness was the smallest.Furthermore,when the correlation dimension curve decreases,the roughness curve increases.The correlation dimension and surface roughness exhibit opposite variation trends.The higher the correlation dimension,the lower the surface roughness.The surface roughness of the aluminum alloy can be characterized online by calculating the correlation dimension during burnishing.
文摘Burnishing is a profitable process of surface finishing due to its ability to be automated,which makes burnishing method more desirable than other finishing methods.To obtain high surface finish,non-stop operation is required for CNC machine and we can attain that by choosing a suitable trajectory of the finishing tool.In other words,burnishing paths should be multidirectional rather than monotonic,in order to cover uniformly the surface.Indeed,the burnishing force is also a key parameter of the burnishing process because it determines the degree of plastic deformation,and that makes determining the optimum burnishing force an essential step of the burnishing process a success.Therefore,we consider the strategy of ball burnishing path and the burnishing force as variable parameters in this study.In this paper,we propose a new strategy of burnishing tool path with trochoid cycles that achieves a multidirectional burnishing of the surface according to various patterns.Taking into consideration the optimum burnishing force,to improve flat surface finish of AL6061-O samples by reducing the surface roughness parameter(Rz).Experiments carried out on 3-axis milling machine show that the proposed trochoidal path is more effective than the conventional one.
文摘Slide burnishing process, which is a surface severe plastic deformation technique, offers an attractive post-machining alternative due to its chip-less and relatively simple operations. The purpose of the present work is to investigate effects of initial turned surface roughness on the burnished surface roughness and hardness in slide burnishing. The carbon steel samples those have different roughness surfaces being treated were prepared by turning by varying the feed. Slide burnishing was then carried out by a silicon nitride ceramic ball that was loaded and fed on the turned surface of a rotating specimen using a lathe machine. It was found that the turned surfaces were smoothed drastically by the burnishing process, and that the Ra and Rz values were reduced at most by a factor of 52 and 21, respectively. However, the smoothing effect of burnishing has limit, and the limited maximum height roughness (Rz*) for burnishing smoothing increased under a higher burnishing force and with a larger ball diameter. When the Rz values of initial turned surfaces were less than the Rz*, the roughness of the burnished surfaces did not depend on the roughness of the initial turned surface and the burnishing force. There was no significant difference in the burnished microstructure and hardness under a specific burnishing force among the initial turned surface roughness, while a higher burnishing force caused a greater increase in surface hardness.
基金supported by the Department of Science and Technology Government of India,grant number SP/YO2019/1287(G)supported by Fronius India Solutions&Skill Centre,Bengaluru and CRF NITK Surathkal.
文摘Cold Metal Transfer-Based Wire Arc Directed Energy Deposition(CMT-WA-DED)presents a promising avenue for the rapid fabrication of components crucial to automotive,shipbuilding,and aerospace industries.However,the susceptibility to fatigue of CMT-WA-DED-produced AZ31 Mg alloy components has impeded their widespread adoption for critical load-bearing applications.In this study,a comprehensive investigation into the fatigue behaviour of WA-DED-fabricated AZ31 Mg alloy has been carried out and compared to commercially available wrought AZ31 alloy.Our findings indicate that the as-deposited parts exhibit a lower fatigue life than wrought Mg alloy,primarily due to poor surface finish,tensile residual stress,porosity,and coarse grain microstructure inherent in the WA-DED process.Low Plasticity Burnishing(LPB)treatment is applied to mitigate these issues,which induce significant plastic deformation on the surface.This treatment resulted in a remarkable improvement of fatigue life by 42%,accompanied by a reduction in surface roughness,grain refinement and enhancement of compressive residual stress levels.Furthermore,during cyclic deformation,WA-DED specimens exhibited higher plasticity and dislocation density compared to both wrought and WA-DED+LPB specimens.A higher fraction of Low Angle Grain Boundaries(LAGBs)in WA-DED specimens contributed to multiple crack initiation sites and convoluted crack paths,ultimately leading to premature failure.In contrast,wrought and WA-DED+LPB specimens displayed a higher percentage of High Angle Grain Boundaries(HAGBs),which hindered dislocation movement and resulted in fewer crack initiation sites and less complex crack paths,thereby extending fatigue life.These findings underscore the effectiveness of LPB as a post-processing technique to enhance the fatigue performance of WA-DED-fabricated AZ31 Mg alloy components.Our study highlights the importance of LPB surface treatment on AZ31 Mg components produced by CMT-WA-DED to remove surface defects,enabling their widespread use in load-bearing applications.
文摘Microtextured surfaces,such as those with groove,hole,or protrusion structures,are widely used in various industries for bonding dissimilar materials because of their anchor effect,which enhances adhesion and penetration with other materials.Although surfaces with grooves and protrusions are expected to show higher bonding strength,it is difficult to fabricate such hybrid structures using a material removal process or additive manufacturing.This study established a new burnishing method using a tool with preformed microgrooves at the tip to fabricate groove-with-protrusion structures on metal surfaces by plastic deformation.The tip of a ball-shaped polycrystalline diamond(PCD)tool was irradiated with a femtosecond pulsed laser to generate multiple trapezoid ten-micron scale grooves.Burnishing was then conducted on an oxygen-free copper surface to investigate the characteristics and mechanism of the burnishing-induced plastic deformation behaviors.The results showed that protrusions and grooves,which were several tens of micrometers in height and depth,were simultaneously produced along the tool path on the material surface.Tool sliding on the workpiece induced shear stress,which mainly triggered dislocation movement and plastic deformation enhancement.Cross-sectional observation revealed that grain elongation and refinement remarkably increased with the burnishing depth,indicating that the shear stress from burnishing produced refined grains that flowed and formed the protrusions.This research demonstrates the feasibility of a highly efficient method for simultaneously generating groove-with-protrusion structures with enhanced surface properties.
基金funded by JKA and its promotion funds from the KEIRIN RACE.
文摘A texturing technique is proposed in which a burnishing tool with a hemispherical tip intermittently contacts a target surface,inducing plastic fow in the surface material to generate a periodic microtopography.The mechanism underlying texture formation in the intermittent burnishing process is elucidated,and the fuctional viability of the resulting textured surface is assessed through friction and wear tests.The burnishing tool with a hemispherical tip was rotated eccentrically from the spindle of a fve-axis machining center,facilitating intermittent plastic deformation of the target surface material over multiple tool rotations,thereby producing fne dimples on the surface.Burnishing experiments on an aluminum alloy revealed the efects of tool tip radius and eccentricity on the resulting texture morphology.The dimpled texture produced by a single tool-surface contact exhibited an elliptical shape,with ellipticity controlled by the tool tip radius and eccentricity.The mechanism governing textured surface formation through plastic fow was elucidated by creating overlapping textured regions at equal pitch intervals.High compressive residual stresses were induced on the textured surface.Friction and wear tests using the ball-on-disk method demonstrated that textured surfaces,created under optimized burnishing conditions efectively mitigated the aggressiveness of the sliding mating material.
基金financially supported by the National Natural Science Foundation of China(No.51105246)
文摘The fracture morphologies of several advanced high-strength steels （DP590, DP780, DP980, Ml180, and M1300） formed in uniaxial tension and piercing were observed by scanning electron microscope, and then quantitatively analyzed by image processing technique. The tension-induced fractographs are dominated by obvious uniform or bimodal size dimples, while shearing-induced fractographs have smooth surfaces and few dimples. The fracture zone of higher grade DP steels is smoother. As for M1180 and M1300, the fracture zones consist of very small dimples and smooth brittle surfaces. The dimple size of M1300（ ,- 1.2 tm） is smaller than that of M1180（ 1.6 tm）. Moreover, in the tensile fracture, the quantitative correlation between average dimple diameter （d） and tensile strength （a） can be represented by d = 10,502.32a-121. However, the relation between dimple density and tensile strength is not monotonic due to the appearance of bimodal size dimples with increase of tensile strength. For shearing-induced fracture during piercing, the fitted empirical model between the percentage of burnish zone （f） and tensile strength can be described asf --- 239.9a-＇36.
