Study On The Formation Mechanism Of The Controllable Bottom Shape Of Surface Texture Of Nanosecond Laser

The surface texture is a micro-nanoscale microstructure with a specific shape and distribution pattern on the surface of the material by a certain processing method.The simulation studies and theoretical analysis results in recent years show that Optimizing the shape of the bottom surface of the surface texture can effectively improve the tribological properties of the textured friction pair.However,due to the limitations of the preparation process,the experimental study on the influence of the texture on the bottom shape of the texture is still relatively lack of.Laser processing is expected to realize the construction of the controllable bottom shape texture.In theory,effective control of the hole shape can be achieved by controlling the laser light intensity distribution and controlling the thickness of the molten layer.Therefore,the key to achieving the construction of the controllable bottom texture is to achieve control of the thickness of the molten layer.To this end,this paper investigates the influence of laser parameters on the thickness of the molten layer in nanosecond laser processing by numerical simulation and experiment,and specifically carries out the following work:First of all,Construct a nanosecond laser processing model,during the simulation,the laser ablation model is simplified into a two-dimensional symmetrical structure,and the model is irregularly divided using the Dist Mesh meshing tool.Using MATLAB software and parametric design language,the variation of texture parameters such as melt thickness and ablation profile with laser parameters(including laser energy density,pulse number and pulse width)was simulated.It is found that in a wide energy range,the melt thickness produced by nanosecond laser processing varies with the energy density of the laser pulse in accordance with the model proposed by C K?rner;at low energy density,as the laser pulse energy increases,simulation and experimental results show that the melt thickness decreases slightly with the increase of energy density;as the number of pulses increases,the change of melt thickness shows an upward trend.It can be seen that relative to the influence of laser energy,the increase in the number of pulses has a more significant effect on the melt thickness;in the range of pulse widths examined,the melt thickness at the center point increases almost proportionally with the increase in laser pulse width.The above results show that the melt thickness in nanosecond laser processing can be effectively controlled by controlling the laser parameters.However,the anomalous variation of melt thickness with energy density means that at lower energy densities,there are other factors associated with energy density that affect the melt thickness,which is for further study.Controlling the pulse width allows control of the spatial distribution of the temperature field andcontrol of the melt thickness.This conclusion can be used to explain that an increase in the laser pulse width will result in an extended laser and material action time resulting in more melt.At the same time,it will provide a useful reference for the study of the thickness of recast layer in laser micropore processing.Finally,the simulation results were verified by the variation of the relative height of the microstructure crater with the pulse energy in the nanosecond laser processing experiment,and the controllability of the melt thickness of nanosecond laser processing was further verified.In order to further confirm the controllability of the nanosecond laser intensity distribution on the shape of the texture bottom,we found that the laser ablation profile and intensity distribution are strong in each case by simulating the ablation profile under different laser intensity distribution conditions.The correlation,that is,controlling the laser intensity distribution is an effective way to achieve the shape control of the texture bottom.This provides a certain reference for the control of laser surface texture morphology.The research results in this paper lay a theoretical foundation for nanosecond laser processing of controlled bottom texture,and have certain guiding significance for improving the fluid lubrication performance of friction pair by laser surface texturing technology.