Laser-assisted machining has been considered as a new alternative machining method of difficult-to-cut materials. A laser module with one-axis manipulator is developed to focus on preheating laser beam effectively. Fi...Laser-assisted machining has been considered as a new alternative machining method of difficult-to-cut materials. A laser module with one-axis manipulator is developed to focus on preheating laser beam effectively. First of all, the thermal characteristic analysis was performed to verify the importance of laser module location. Laser module should be moved within 1 mm. Analysis conditions of three positions in driving range of the one-axis manipulator are selected. And a C coupling is used as a connection device for spindle and laser module. An initial model has one C coupling, and the number of C coupling has been increased from 1 to 2 in an improved model. And the analysis is carried out again for the one-axis manipulator. The results of the static analysis, the maximum displacement and the maximum stress are decreased by 22% and 11%, respectively, for the improved model when the laser module is located at farthest away from the spindle unit. As a result of the modal analysis, the first natural frequency mode is increased by 13%, 18% and 12% at these positions of the improved model, respectively. The harmonic analysis of the improved model was performed by analyzing the results of the modal analysis. The maximum deformation was 0.33 mm in driving unit at 222 Hz. And the maximum compliance of the ISO axis direction was 0.23 mm/N. Finally, the one-axis manipulator has been fabricated successfully using the analysis result.展开更多
The Al 2O 3 particles reinforced aluminum matrix composite (Al 2O 3p/Al) are more and more widely used for their excellent physical and chemical properties. However, their poor machinability leads to severe tool wear ...The Al 2O 3 particles reinforced aluminum matrix composite (Al 2O 3p/Al) are more and more widely used for their excellent physical and chemical properties. However, their poor machinability leads to severe tool wear and bad machined surface. In this paper laser assisted machining is adopted in machining Al 2O 3p/Al composite and good result was obtained. The result of experiment shows in machining Al 2O 3p/Al composites the cutting force is reduced in 30%～50%, the tool wear is reduced in 20%～30% and machined surface quality is improved in laser assisted machining as compared with conventional cutting. The physical model of the cutting process is set up and explains the reason why the cutting forced are reduced. The state of the particles is the main influence of the change. When the material of cutting zone is heating by laser, the aluminum matrix becomes softer and easier in plastic deformation, which leads to the reduction of the pushing force from the tool to the machined surface. The soften aluminum matrix is more easy to be squeezed out from the machined surface, and it leads the concentration of the Al 2O 3 particles in the surface layer of machined surface. The softening effect of laser heating on aluminum matrix reduces the pushing forces of the Al 2O 3 particles on the clearance face of cutting tool, which is just the reason for the severe cutting tool wear in conventional machining of Al 2O 3p/Al composite. Because the Al 2O 3 particles were pushed in during the cutting process, the particles increased in the surface layer. Because of the difference in thermal conductivity and thermal expansion between the Al-matrix and Al 2O 3 particle, residual stress is changed in the matrix after machining due to the extrusion of the tool, deformation of the matrix and displacement of the Al 2O 3 particle in the matrix. Temperature gradient comes into the cutting zone and the work-piece surface layer, it will lead to the increase of thermal stress and misfit dislocation in the matrix. The residual stress is compressive in the laser assisted hot cutting surface, the compressive stress is nearly triple times than that in the conventional cutting surface. Some analysis on the mechanism of laser heat assisted machining of Al 2O 3p/Al composite is given in the paper too.展开更多
Several detailed studies have comprehensively investigated the benefits and limitations of laser-assisted machining(LAM)of titanium alloys.These studies have highlighted the positive impact of the application of laser...Several detailed studies have comprehensively investigated the benefits and limitations of laser-assisted machining(LAM)of titanium alloys.These studies have highlighted the positive impact of the application of laser preheating on reducing cutting forces and improving productivity but have also identified the detrimental effect of LAM on tool life.This paper seeks to evaluate a series of the most common cutting tools with different coating types used in the machining of titanium alloys to identify whether coating type has a dramatic effect on the dominant tool wear mechanisms active during the process.The findings provide a clear illustration that the challenges facing the application of LAM are associated with the development of new types of cutting tools which are not subjected to the diffusion-controlled wear processes that dominate the performance of current cutting tools.展开更多
The low density and high corrosion resistance of titanium alloy make it a material with various applications in the aerospace industry. However, because of its high specifc strength and poor thermal conductivity, ther...The low density and high corrosion resistance of titanium alloy make it a material with various applications in the aerospace industry. However, because of its high specifc strength and poor thermal conductivity, there are problems such as high cutting force, poor surface integrity, and high cutting temperature during conventional machining. As an advanced processing method with high efciency and low damage, laser-assisted machining can improve the machinability of titanium alloy. In this study, a picosecond pulse laser-assisted scratching (PPLAS) method considering both the temperature-dependent material properties and ultrashort pulse laser’s characteristics is frst proposed. Then, the efects of laser power, scratching depth, and scratching speed on the distribution of stress and temperature feld are investigated by simulation. Next, PPLAS experiments are conducted to verify the correctness of the simulation and reveal the removal behavior at various combinations of laser power and scratching depths. Finally, combined with simulated and experimental results, the removal mechanism under the two machining methods is illustrated. Compared with conventional scratching (CS), the tangential grinding force is reduced by more than 60% and the material removal degree is up to 0.948 during PPLAS, while the material removal is still primarily in the form of plastic removal. Grinding debris in CS takes the form of stacked fakes with a “fsh scale” surface, whereas it takes the form of broken serrations in PPLAS. This research can provide important guidance for titanium alloy grinding with high surface quality and low surface damage.展开更多
Laser-assisted machining(LAM),as one of the most efficient ways,has been employed to improve the machinability of nickel-based superalloys.However,the conventional LAM process usually used high power laser with large ...Laser-assisted machining(LAM),as one of the most efficient ways,has been employed to improve the machinability of nickel-based superalloys.However,the conventional LAM process usually used high power laser with large spot size,easily leading to high processing costs and overheating of bulk materials.In this paper,a new approach of selective laser ablation assisted milling(SLA-Mill)process for nickel-based superalloys was proposed,in which low power laser with small spot size was used to selectively ablate the uncut surface in front of the cutting tool,resulting in plentiful surface defects emerging.Such defects would significantly weaken the mechanical strength of difficult-to-cut materials,which was different from the thermal“softening”principle of conventional LAM.Thus,the laser ablation effect with low power and small spot size was first studied.The relationship between process parameters(e.g.,laser power,cutting speed and cutting depth)and process characteristics of SLA-Mill(e.g.,chip morphology,tool wear and surface integrity)was systematically discussed.Moreover,the chip formation mechanism in the SLA-Mill process was indepth analyzed.Results show that the SLA-Mill process is an effective approach for enhancing the machinability of nickel-based superalloys.The resultant cutting force has a reduction of about 30%at laser power of 60 W,cutting speed of 90 m/min,and cutting depth of 0.1 mm.Furthermore,the chip formation,tool wear,and surface integrity have improved significantly.In general,this paper provides a new route for the application of LAM technology.展开更多
基金Project(2012-0005688) supported by the National Research Foundation of Korea (NRF) Grant funded by the Korea Government (MEST)
文摘Laser-assisted machining has been considered as a new alternative machining method of difficult-to-cut materials. A laser module with one-axis manipulator is developed to focus on preheating laser beam effectively. First of all, the thermal characteristic analysis was performed to verify the importance of laser module location. Laser module should be moved within 1 mm. Analysis conditions of three positions in driving range of the one-axis manipulator are selected. And a C coupling is used as a connection device for spindle and laser module. An initial model has one C coupling, and the number of C coupling has been increased from 1 to 2 in an improved model. And the analysis is carried out again for the one-axis manipulator. The results of the static analysis, the maximum displacement and the maximum stress are decreased by 22% and 11%, respectively, for the improved model when the laser module is located at farthest away from the spindle unit. As a result of the modal analysis, the first natural frequency mode is increased by 13%, 18% and 12% at these positions of the improved model, respectively. The harmonic analysis of the improved model was performed by analyzing the results of the modal analysis. The maximum deformation was 0.33 mm in driving unit at 222 Hz. And the maximum compliance of the ISO axis direction was 0.23 mm/N. Finally, the one-axis manipulator has been fabricated successfully using the analysis result.
文摘The Al 2O 3 particles reinforced aluminum matrix composite (Al 2O 3p/Al) are more and more widely used for their excellent physical and chemical properties. However, their poor machinability leads to severe tool wear and bad machined surface. In this paper laser assisted machining is adopted in machining Al 2O 3p/Al composite and good result was obtained. The result of experiment shows in machining Al 2O 3p/Al composites the cutting force is reduced in 30%～50%, the tool wear is reduced in 20%～30% and machined surface quality is improved in laser assisted machining as compared with conventional cutting. The physical model of the cutting process is set up and explains the reason why the cutting forced are reduced. The state of the particles is the main influence of the change. When the material of cutting zone is heating by laser, the aluminum matrix becomes softer and easier in plastic deformation, which leads to the reduction of the pushing force from the tool to the machined surface. The soften aluminum matrix is more easy to be squeezed out from the machined surface, and it leads the concentration of the Al 2O 3 particles in the surface layer of machined surface. The softening effect of laser heating on aluminum matrix reduces the pushing forces of the Al 2O 3 particles on the clearance face of cutting tool, which is just the reason for the severe cutting tool wear in conventional machining of Al 2O 3p/Al composite. Because the Al 2O 3 particles were pushed in during the cutting process, the particles increased in the surface layer. Because of the difference in thermal conductivity and thermal expansion between the Al-matrix and Al 2O 3 particle, residual stress is changed in the matrix after machining due to the extrusion of the tool, deformation of the matrix and displacement of the Al 2O 3 particle in the matrix. Temperature gradient comes into the cutting zone and the work-piece surface layer, it will lead to the increase of thermal stress and misfit dislocation in the matrix. The residual stress is compressive in the laser assisted hot cutting surface, the compressive stress is nearly triple times than that in the conventional cutting surface. Some analysis on the mechanism of laser heat assisted machining of Al 2O 3p/Al composite is given in the paper too.
文摘Several detailed studies have comprehensively investigated the benefits and limitations of laser-assisted machining(LAM)of titanium alloys.These studies have highlighted the positive impact of the application of laser preheating on reducing cutting forces and improving productivity but have also identified the detrimental effect of LAM on tool life.This paper seeks to evaluate a series of the most common cutting tools with different coating types used in the machining of titanium alloys to identify whether coating type has a dramatic effect on the dominant tool wear mechanisms active during the process.The findings provide a clear illustration that the challenges facing the application of LAM are associated with the development of new types of cutting tools which are not subjected to the diffusion-controlled wear processes that dominate the performance of current cutting tools.
基金Supported by National Natural Science Foundation of China(Grant No.52175377)Chongqing Municipal Science Foundation(Grant No.CSTB2022NSCQ-LZX0080)+1 种基金Fundamental Research Funds for Central Universities(Grant Nos.2023CDJXY-026 and 2023CDJXY-021)National Science and Technology Major Project(Grant No.2017-VII-0002-0095).
文摘The low density and high corrosion resistance of titanium alloy make it a material with various applications in the aerospace industry. However, because of its high specifc strength and poor thermal conductivity, there are problems such as high cutting force, poor surface integrity, and high cutting temperature during conventional machining. As an advanced processing method with high efciency and low damage, laser-assisted machining can improve the machinability of titanium alloy. In this study, a picosecond pulse laser-assisted scratching (PPLAS) method considering both the temperature-dependent material properties and ultrashort pulse laser’s characteristics is frst proposed. Then, the efects of laser power, scratching depth, and scratching speed on the distribution of stress and temperature feld are investigated by simulation. Next, PPLAS experiments are conducted to verify the correctness of the simulation and reveal the removal behavior at various combinations of laser power and scratching depths. Finally, combined with simulated and experimental results, the removal mechanism under the two machining methods is illustrated. Compared with conventional scratching (CS), the tangential grinding force is reduced by more than 60% and the material removal degree is up to 0.948 during PPLAS, while the material removal is still primarily in the form of plastic removal. Grinding debris in CS takes the form of stacked fakes with a “fsh scale” surface, whereas it takes the form of broken serrations in PPLAS. This research can provide important guidance for titanium alloy grinding with high surface quality and low surface damage.
基金This paper was funded by the National Natural Science Foundation of China(Grant Nos.51375174 and 52075187)the Natural Science Foundation of Guangdong Province(Grant No.2017A030313260)the Fundamental Research Funds for the Central University(Grant No.2017ZD024).
文摘Laser-assisted machining(LAM),as one of the most efficient ways,has been employed to improve the machinability of nickel-based superalloys.However,the conventional LAM process usually used high power laser with large spot size,easily leading to high processing costs and overheating of bulk materials.In this paper,a new approach of selective laser ablation assisted milling(SLA-Mill)process for nickel-based superalloys was proposed,in which low power laser with small spot size was used to selectively ablate the uncut surface in front of the cutting tool,resulting in plentiful surface defects emerging.Such defects would significantly weaken the mechanical strength of difficult-to-cut materials,which was different from the thermal“softening”principle of conventional LAM.Thus,the laser ablation effect with low power and small spot size was first studied.The relationship between process parameters(e.g.,laser power,cutting speed and cutting depth)and process characteristics of SLA-Mill(e.g.,chip morphology,tool wear and surface integrity)was systematically discussed.Moreover,the chip formation mechanism in the SLA-Mill process was indepth analyzed.Results show that the SLA-Mill process is an effective approach for enhancing the machinability of nickel-based superalloys.The resultant cutting force has a reduction of about 30%at laser power of 60 W,cutting speed of 90 m/min,and cutting depth of 0.1 mm.Furthermore,the chip formation,tool wear,and surface integrity have improved significantly.In general,this paper provides a new route for the application of LAM technology.
