The model of heat source(MHS) which reflects the thermal interaction between materials and laser during processing determines the accuracy of simulation results. To acquire desirable simulations results, although vari...The model of heat source(MHS) which reflects the thermal interaction between materials and laser during processing determines the accuracy of simulation results. To acquire desirable simulations results, although various modifications of heat sources in the aspect of absorption process of laser by materials have been purposed, the distribution of laser power density(DLPD) in MHS is still modeled theoretically. However, in the actual situations of laser processing, the DLPD is definitely different from the ideal models. So, it is indispensable to build MHS using actual DLPD to improve the accuracy of simulation results. Besides, an automatic modeling method will be benefit to simplify the tedious pre-processing of simulations. This paper presents a modeling method and corresponding algorithm to model heat source using measured DLPD. This algorithm automatically processes original data to get modeling parameters and provides a step MHS combining with absorption models. Simulations and experiments of heat transfer in steel plates irradiated by laser prove the mothed and the step MHS. Moreover, the investigations of laser induced thermal-crack propagation in glass highlight the signification of modeling heat source based on actual DLPD and demonstrate the enormous application of this method in the simulation of laser processing.展开更多
Thermo' computer program is described. It is intended for computation of thermal cycle parameters during surface pulse heating. For example, during laser processing, surface heating owing to grinding, etc. It gi...Thermo' computer program is described. It is intended for computation of thermal cycle parameters during surface pulse heating. For example, during laser processing, surface heating owing to grinding, etc. It gives rates of heating, cooling, as well as temperature gradients and cumulative exposure time as function of the CURRENT TEMPERATURE, with the peak temperature at the surface as variable parameter. The indicated parameters are calculated at a surface, close to a surface (at 0.01μm)and for the points at a depth of the body. Demo ver. of the software: http://www. sstu.samara.ru/physics/fedosov/thermo_d. zip展开更多
Laser powder bed fusion(LPBF)is an advanced manufacturing technology;however,inappropriate LPBF process parameters may cause printing defects in materials.In the present work,the LPBF process of Ti-6.5Al-3.5Mo-1.5Zr-0...Laser powder bed fusion(LPBF)is an advanced manufacturing technology;however,inappropriate LPBF process parameters may cause printing defects in materials.In the present work,the LPBF process of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy was investigated by a two-step optimization approach.Subsequently,heat transfer and liquid flow behaviors during LPBF were simulated by a well-tested phenomenological model,and the defect formation mechanisms in the as-fabricated alloy were discussed.The optimized process parameters for LPBF were detected as laser power changed from 195 W to 210 W,with scanning speed of 1250 mm/s.The LPBF process was divided into a laser irradiation stage,a spreading flow stage,and a solidification stage.The morphologies and defects of deposited tracks were affected by liquid flow behavior caused by rapid cooling rates.The findings of this research can provide valuable support for printing defect-free metal components.展开更多
The microstructural changes of Fe83Si4B13 amorphous mother alloy during the heating process were investigated by Laser Scanning Confocal Microscopy （LSCM） ,and the phase transformation was determined by the Thermo-C...The microstructural changes of Fe83Si4B13 amorphous mother alloy during the heating process were investigated by Laser Scanning Confocal Microscopy （LSCM） ,and the phase transformation was determined by the Thermo-Calc calculations. The differences in the melting points measured by Differential Scanning Calorimetry （DSC） and LSCM, and those obtained by Thermo-Calc calculations were also discussed. It is found that the melting points measured by DSC and LSCM are relatively similar, whereas the onset and end of the melting temperatures calculated by Thermo-Calc software are higher than those measured by DSC and observed by LSCM.展开更多
This research work is focused on both experimental and numerical analysis of laser surface hardening of AISI M2 high speed tool steel. Experimental analysis aims at clarifying effect of different laser processing para...This research work is focused on both experimental and numerical analysis of laser surface hardening of AISI M2 high speed tool steel. Experimental analysis aims at clarifying effect of different laser processing parameters on properties and performance of laser surface treated specimens. Numerical analysis is concerned with analytical approaches that provide efficient tools for estimation of surface temperature, surface hardness and hardened depth as a function of laser surface hardening parameters. Results indicated that optimization of laser processing parameters including laser power, laser spot size and processing speed combination is of considerable importance for achieving maximum surface hardness and deepest hardened zone. In this concern, higher laser power, larger spot size and lower processing speed are more efficient. Hardened zone with 1.25 mm depth and 996 HV surface hardness was obtained using 1800 W laser power, 4 mm laser spot size and 0.5 m/min laser processing speed. The obtained maximum hardness of laser surface treated specimen is 23% higher than that of conventionally heat treated specimen. This in turn has resulted in 30% increase in wear resistance of laser surface treated specimen. Numerical analysis has been carried out for calculation of temperature gradient and cooling rate based on Ashby and Easterling equations. Then, surface hardness and hardened depth have been numerically estimated based on available Design-Expert software. Numerical results indicated that cooling rate of laser surface treated specimen is high enough to be beyond the nose of the CCT diagram of the used steel that in turn resulted in a hard/martensitic structure. Numerically estimated values of surface temperature, surface hardness and hardened depth as a function of laser processing parameters are in a good agreement with experimental results. Laser processing charts indicating expected values of surface temperature, surface hardness and hardened depth as a function of different wider range of laser processing parameters are proposed.展开更多
A heat and mass transfer modelling containing phase transformation dynamics is made for pure metals and binary alloys under pulsed laser processing. The nonequilibrium effects of processing parameters and physical pro...A heat and mass transfer modelling containing phase transformation dynamics is made for pure metals and binary alloys under pulsed laser processing. The nonequilibrium effects of processing parameters and physical properties are evaluated on the melting and solidification of pure metals (Al, Cu, Fe and Ni) and Al Cu alloys. It is shown that the energy intensity of laser beam and physical properties of metals and the solute concentration of alloys have important effect on the interface temperature, melting and solidification velocity, melting depth and non equilibrium partition coefficient. This situation is resulted from the interaction of heat transfer, redistribution of solute, solute trapping and growth kinetics.展开更多
基金Project(2021YFF0500200) supported by the National Key R&D Program of ChinaProject(52105437) supported by the National Natural Science Foundation of China+1 种基金Project(202006120184) supported by the Heilongjiang Provincial Postdoctoral Science Foundation,ChinaProject(LBH-Z20054) supported by the China Scholarship Council。
文摘The model of heat source(MHS) which reflects the thermal interaction between materials and laser during processing determines the accuracy of simulation results. To acquire desirable simulations results, although various modifications of heat sources in the aspect of absorption process of laser by materials have been purposed, the distribution of laser power density(DLPD) in MHS is still modeled theoretically. However, in the actual situations of laser processing, the DLPD is definitely different from the ideal models. So, it is indispensable to build MHS using actual DLPD to improve the accuracy of simulation results. Besides, an automatic modeling method will be benefit to simplify the tedious pre-processing of simulations. This paper presents a modeling method and corresponding algorithm to model heat source using measured DLPD. This algorithm automatically processes original data to get modeling parameters and provides a step MHS combining with absorption models. Simulations and experiments of heat transfer in steel plates irradiated by laser prove the mothed and the step MHS. Moreover, the investigations of laser induced thermal-crack propagation in glass highlight the signification of modeling heat source based on actual DLPD and demonstrate the enormous application of this method in the simulation of laser processing.
文摘Thermo' computer program is described. It is intended for computation of thermal cycle parameters during surface pulse heating. For example, during laser processing, surface heating owing to grinding, etc. It gives rates of heating, cooling, as well as temperature gradients and cumulative exposure time as function of the CURRENT TEMPERATURE, with the peak temperature at the surface as variable parameter. The indicated parameters are calculated at a surface, close to a surface (at 0.01μm)and for the points at a depth of the body. Demo ver. of the software: http://www. sstu.samara.ru/physics/fedosov/thermo_d. zip
基金Supported by Development of a Verification Platform for Product Design,Process and Information Exchange Standards in Additive Manufacturing (Grant No.2019-00899-1-1)Ministry of Science and Technology of the People’s Republic of China (Grant No.2017YFB1103000)+1 种基金National Natural Science Foundation of China (Grant No.51375242)Natural Science Foundation of Jiangsu Province (Grant No.BK20180483)。
文摘Laser powder bed fusion(LPBF)is an advanced manufacturing technology;however,inappropriate LPBF process parameters may cause printing defects in materials.In the present work,the LPBF process of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy was investigated by a two-step optimization approach.Subsequently,heat transfer and liquid flow behaviors during LPBF were simulated by a well-tested phenomenological model,and the defect formation mechanisms in the as-fabricated alloy were discussed.The optimized process parameters for LPBF were detected as laser power changed from 195 W to 210 W,with scanning speed of 1250 mm/s.The LPBF process was divided into a laser irradiation stage,a spreading flow stage,and a solidification stage.The morphologies and defects of deposited tracks were affected by liquid flow behavior caused by rapid cooling rates.The findings of this research can provide valuable support for printing defect-free metal components.
文摘The microstructural changes of Fe83Si4B13 amorphous mother alloy during the heating process were investigated by Laser Scanning Confocal Microscopy （LSCM） ,and the phase transformation was determined by the Thermo-Calc calculations. The differences in the melting points measured by Differential Scanning Calorimetry （DSC） and LSCM, and those obtained by Thermo-Calc calculations were also discussed. It is found that the melting points measured by DSC and LSCM are relatively similar, whereas the onset and end of the melting temperatures calculated by Thermo-Calc software are higher than those measured by DSC and observed by LSCM.
文摘This research work is focused on both experimental and numerical analysis of laser surface hardening of AISI M2 high speed tool steel. Experimental analysis aims at clarifying effect of different laser processing parameters on properties and performance of laser surface treated specimens. Numerical analysis is concerned with analytical approaches that provide efficient tools for estimation of surface temperature, surface hardness and hardened depth as a function of laser surface hardening parameters. Results indicated that optimization of laser processing parameters including laser power, laser spot size and processing speed combination is of considerable importance for achieving maximum surface hardness and deepest hardened zone. In this concern, higher laser power, larger spot size and lower processing speed are more efficient. Hardened zone with 1.25 mm depth and 996 HV surface hardness was obtained using 1800 W laser power, 4 mm laser spot size and 0.5 m/min laser processing speed. The obtained maximum hardness of laser surface treated specimen is 23% higher than that of conventionally heat treated specimen. This in turn has resulted in 30% increase in wear resistance of laser surface treated specimen. Numerical analysis has been carried out for calculation of temperature gradient and cooling rate based on Ashby and Easterling equations. Then, surface hardness and hardened depth have been numerically estimated based on available Design-Expert software. Numerical results indicated that cooling rate of laser surface treated specimen is high enough to be beyond the nose of the CCT diagram of the used steel that in turn resulted in a hard/martensitic structure. Numerically estimated values of surface temperature, surface hardness and hardened depth as a function of laser processing parameters are in a good agreement with experimental results. Laser processing charts indicating expected values of surface temperature, surface hardness and hardened depth as a function of different wider range of laser processing parameters are proposed.
文摘A heat and mass transfer modelling containing phase transformation dynamics is made for pure metals and binary alloys under pulsed laser processing. The nonequilibrium effects of processing parameters and physical properties are evaluated on the melting and solidification of pure metals (Al, Cu, Fe and Ni) and Al Cu alloys. It is shown that the energy intensity of laser beam and physical properties of metals and the solute concentration of alloys have important effect on the interface temperature, melting and solidification velocity, melting depth and non equilibrium partition coefficient. This situation is resulted from the interaction of heat transfer, redistribution of solute, solute trapping and growth kinetics.
