CN-121972797-A - Mobile femtosecond laser processing morphology prediction method considering facula evolution

CN121972797ACN 121972797 ACN121972797 ACN 121972797ACN-121972797-A

Abstract

The invention discloses a method for predicting the morphology of mobile femtosecond laser processing by considering the evolution of light spots, and particularly relates to the field of femtosecond laser processing. The method comprises the steps of establishing a three-dimensional geometric model of a material to be processed, conducting grid division on the three-dimensional geometric model to obtain a grid model, establishing a dual-temperature model, determining laser intensity, determining a laser source item according to the laser intensity, inputting the laser source item into the dual-temperature model to obtain lattice temperature and electron temperature, determining grid deformation speed when the lattice temperature is greater than or equal to sublimation temperature, removing the material of the grid model according to the grid deformation speed to obtain a deformed grid model, obtaining ablation depth, updating the radius of a light spot when the next pulse is conducted, and updating the lattice temperature, the electron temperature and the ablation depth until the lattice temperature and the electron temperature reach balance, and obtaining final ablation depth. Based on the method, the prediction accuracy can be improved.

Inventors

ZHANG ZHAO
GONG WEICHUAN
WU XIN
PANG SHUQI
LUO MING

Assignees

西北工业大学

Dates

Publication Date: 20260505
Application Date: 20260311

Claims (8)

1. A method for predicting the morphology of mobile femtosecond laser processing by considering the evolution of a light spot is characterized by comprising the following steps: establishing a three-dimensional geometric model of a material to be processed, and carrying out grid division on the three-dimensional geometric model to obtain a grid model; Establishing a double-temperature model according to electron temperature and lattice temperature in a material to be processed and a laser source item in the femtosecond laser pulse processing process; determining laser intensity according to laser scanning speed, pulse repetition frequency, pulse width, light spot radius, reflectivity of a material to be processed, laser power and moving distance of laser; Determining a laser source item according to the laser intensity, and inputting the laser source item into a dual-temperature model to obtain a lattice temperature and an electron temperature; when the lattice temperature is greater than or equal to the sublimation temperature, determining the deformation speed of the lattice according to the lattice temperature, the ablation temperature and the sublimation heat, removing the material of the lattice model according to the deformation speed of the lattice to obtain a deformed lattice model, and obtaining the ablation depth; And updating the radius of the focal spot according to the ablation depth, the Rayleigh length and the radius of the focal spot during the next pulse, and updating the lattice temperature, the electron temperature and the ablation depth until the lattice temperature and the electron temperature reach balance, thereby obtaining the final ablation depth.
2. The method for predicting the morphology of mobile femtosecond laser machining taking into consideration spot evolution as set forth in claim 1, wherein the dual temperature model is: In the formula, The temperature of the electrons is indicated and, The temperature of the crystal lattice is indicated, And Respectively represent electron and lattice specific heat capacities, Represents the thermal conductivity of electrons, Representing the coupling coefficient of the coupling coefficient, Representing the laser source term.
3. The method for predicting the morphology of mobile femtosecond laser processing taking into account spot evolution according to claim 1, wherein the expression of the laser intensity is: In the formula, Indicating the reflectivity of the material and, The laser power is indicated as being the power of the laser, The frequency of the repetition is indicated and, The pulse width is indicated as such, Represents the scanning speed, x represents the moving distance in the horizontal direction, y represents the moving distance in the vertical horizontal direction, and in the plane of the heat source, For the spot radius at ablation depth z, initially, ablation depth z is 0, then Is the spot radius of the focal position.
4. The method for predicting the morphology of mobile femtosecond laser machining taking into account spot evolution as set forth in claim 1, wherein the expression of the spot radius at the ablation depth z is: where z represents the ablation depth, The spot radius representing the focal position, Representing the rayleigh length.
5. The method for predicting the morphology of mobile femtosecond laser processing taking into account spot evolution as set forth in claim 1, wherein the expression of the laser source term is: In the formula, The intensity of the laser light is indicated, Representing the femtosecond laser pulse form.
6. The method for predicting the morphology of mobile femtosecond laser machining taking into consideration spot evolution as set forth in claim 1, wherein the expression of the grid deformation speed is: In the formula, Representing the rate of deformation of the mesh, Representing the effective heat transfer coefficient in the form of a step function, The ablation temperature is indicated as such, The temperature of the crystal lattice is indicated, The heat of sublimation is used to produce a heat, Representing the material density.
7. The method for predicting the morphology of the mobile femtosecond laser processing taking into consideration the spot evolution according to claim 1, wherein the removing the material of the grid model according to the grid deformation speed to obtain the deformed grid model comprises the following steps: And removing the material of the grid model by adopting any Lagrange-Euler method according to the grid deformation speed to obtain the deformed grid model.
8. The utility model provides a remove femtosecond laser processing appearance prediction device of facula evolution is considered which characterized in that includes: the model building module is used for building a three-dimensional geometric model of a material to be processed, and carrying out grid division on the three-dimensional geometric model to obtain a grid model; The heat transfer module is used for establishing a double-temperature model according to electron temperature and lattice temperature in a material to be processed and a laser source item in the femtosecond laser pulse processing process; The laser intensity determining module is used for determining the laser intensity according to the laser scanning speed, the pulse repetition frequency, the pulse width, the light spot radius, the reflectivity of the material to be processed, the laser power and the moving distance of the laser; The calculation module is used for determining a laser source item according to the laser intensity, inputting the laser source item into a dual-temperature model to obtain a lattice temperature and an electron temperature; The deformation geometric module is used for removing the material of the grid model according to the grid deformation speed when the lattice temperature is greater than or equal to the sublimation temperature, so as to obtain a deformed grid model and obtain the ablation depth; And the updating module is used for updating the radius of the optical spot according to the ablation depth, the Rayleigh length and the radius of the optical spot at the focal position when the next pulse is generated, and updating the lattice temperature, the electron temperature and the ablation depth until the lattice temperature and the electron temperature reach balance, so as to obtain the final ablation depth.

Description

Mobile femtosecond laser processing morphology prediction method considering facula evolution Technical Field The invention relates to the field of femtosecond laser processing, in particular to a method for predicting the morphology of mobile femtosecond laser processing by considering the evolution of light spots. Background The femtosecond laser processing has the characteristics of extremely short pulse width (usually in the femtosecond order), high instantaneous peak power, obviously shorter energy deposition time than the material heat diffusion time and the like, so that the approximately 'cold processing' effect can be realized in the material processing process, thereby effectively inhibiting the expansion of a heat affected zone and reducing the heat damage. Meanwhile, the femtosecond laser processing belongs to a non-contact processing mode, is not influenced by cutter abrasion and mechanical force action, and has the advantages of high processing precision, good repeatability, stable processing process, wide material application range and the like. At present, the technology is widely applied to the fields of aerospace, precision manufacturing, microelectronics and the like, and particularly in the precision machining of high-strength and low-heat-conductivity difficult-to-machine materials such as titanium alloy, nickel-based superalloy and the like, the technology has the technical advantage that the traditional machining is difficult to replace. In practical engineering applications, femtosecond lasers are generally used for carrying out multi-pulse continuous or overlapping irradiation processing on the surface of a material in a high-speed scanning mode. Due to the superposition of laser pulses in time and space, the material undergoes complex energy absorption, electronic excitation, phase change and material removal processes during processing, and finally micro-grooves, hole arrays or functional surface textures are formed. The depth, width and shape consistency of the groove and the range of the heat affected zone of the structure directly influence the surface functional property and the service performance of the part. Therefore, how to reasonably select the laser power, pulse parameters, scanning speed and other technological parameters on the premise of ensuring the processing quality becomes a key problem to be solved in the field of femtosecond laser precision processing. In order to reduce time and cost consumption caused by a large number of tests in the process of optimizing technological parameters and improve predictability of the machining process, researchers gradually introduce a numerical simulation method to perform modeling analysis on the femtosecond laser machining process. The double-temperature model is used for describing unbalanced heat transfer and energy coupling processes between the electronic system and the lattice system under the action of the femtosecond laser by respectively establishing energy conservation equations of the electronic system and the lattice system, so that a key physical mechanism in the femtosecond laser processing process can be accurately reflected, and the double-temperature model becomes an important theoretical model in the femtosecond laser processing simulation research. Although the existing femtosecond laser processing simulation method based on the dual-temperature model has a certain research progress under the single-pulse or fixed-point processing condition, the following defects still exist in the practical engineering application: 1. the existing model is mostly based on static or quasi-static pulse assumption, and the actual processing working condition that a laser spot continuously moves along with time and space in the scanning process is not fully considered, so that deviation exists between the description of the multi-pulse superposition processing process and the actual situation, and the trench morphology formed by continuous etching is difficult to accurately predict. 2. Along with the gradual ablation and removal of materials, the relative position between the processing surface and the laser focus is continuously changed, the laser spot size is evolved, most of the existing models still assume that the spot radius is constant, gaussian beam propagation rules are not considered, accumulation of laser energy distribution calculation errors is easily caused, and prediction errors are more obvious especially under deep groove processing conditions. 3. The existing method cannot effectively couple the light beam propagation characteristics, the material removal process and the geometric shape evolution, so that the prediction precision of the depth, the width and the heat affected zone of the groove is insufficient, and a reliable basis is difficult to provide for optimizing the femtosecond laser processing technological parameters. Disclosure of Invention The application mainly aims to provide a method for predicti