A method for predicting groove width of composite materials using femtosecond laser ablation

Abstract

The present invention provides a method for predicting the groove width of composite materials by femtosecond laser ablation. The present invention comprises the following steps: performing a femtosecond laser ablation experiment on the composite material to obtain the ablation threshold F of the material. th ; Establish a laser groove ablation model, and the total energy density F accumulated at a point in the model micro-element area w Reaching the material's ablation threshold F th , the material is ablated; the groove ablation experiment is carried out at different laser scanning rates to obtain the corresponding relationship between different laser scanning rates v and hatching coefficients. According to the relationship between the scanning speed and the hatching coefficient, the laser scanning rate v and energy E are selected. p After that, the corresponding hatching coefficient k is selected to predict the width d of the groove ablation. a Aiming at the problem that the ablation width of composite materials is difficult to control, the present invention proposes a method of transforming point ablation into line ablation and establishes a groove ablation model. The effectiveness of the model prediction results is verified experimentally, providing a theoretical basis for the precision control of femtosecond laser processing of composite materials.

Description

Technical Field

[0001] The present invention relates to the field of special processing of composite materials, and in particular to a method for predicting groove width of composite materials by femtosecond laser ablation. Background Art

[0002] Composite materials, such as particle-reinforced composites (RB-SiC, SiCp / AI) and fiber-reinforced composites (CFRP, Cf / SiC, SiCf / SiC), offer advantages such as low density, high strength, high-temperature resistance, oxidation resistance, and corrosion resistance, and have broad application potential in aerospace and other high-temperature applications. However, due to the significant differences in the physical and chemical properties of the reinforcement and matrix phases of composite materials, processing issues such as poor quality, low efficiency, and poor process stability hinder their wider use, making high-precision, low-damage machining a key technology that must be addressed.

[0003] Ultrafast laser processing plays a crucial role in difficult-to-process applications. Due to its extremely high peak energy and ultra-short timescales, it is widely used for a variety of difficult-to-process materials. Compared to other processing methods, ultrafast lasers release a tremendous amount of energy in an ultra-short time. This allows the material to be ablated before the heat diffuses to untreated areas, making cold processing possible. Consequently, the controllability of the process and the surface quality of the processed material are greatly improved.

[0004] However, in the field of composite material processing, due to their anisotropy and anisotropy, it is difficult to determine the width and depth through simulation and theoretical calculation. Experimental methods are often used to determine them, making it difficult to ensure processing quality and significantly reducing the controllability of ultrafast laser processing. Patent publication number CN112059407A proposes a deep learning-based picosecond ultrafast laser processing system and method. To improve processing controllability, this system uses passive detection, using a detector to monitor the processing surface in real time and making adjustments using the deep learning capabilities of artificial intelligence. However, this is a passive detection method and cannot actively control the width of the laser processing.

[0005] These issues significantly limit the practical application of ultrafast laser processing of composite materials. Therefore, a model-based active prediction method for ultrafast laser processing of composite materials is urgently needed to actively control the width of ultrafast laser ablation and improve processing efficiency and quality. Summary of the Invention

[0006] The present invention proposes a method combining experiments and theories to solve the above problems. In order to solve the problem that the ablation width of composite materials is difficult to control, the present invention proposes a method of transforming point ablation into line ablation, establishes an ablation model based on line ablation and ring ablation, and verifies the effectiveness of the prediction model through experiments. It includes the measurement of the radius r of the point ablation pit, the ablation threshold Fth Calculation of the hatching coefficient k, calculation of the groove ablation width d a The technical means adopted by the present invention are as follows:

[0007] A method for predicting groove width of composite materials by femtosecond laser ablation, comprising the following steps:

[0008] Step S1: Perform a femtosecond laser ablation experiment on the composite material to obtain the ablation threshold F of the material. th ;

[0009] Step S2: Establish a laser groove ablation model, and the total energy density F accumulated at a point in the model micro-element area is w Reaching the material's ablation threshold F th , the material is ablated;

[0010] Step S3, performing a groove ablation experiment at different laser scanning rates to obtain the corresponding relationship between different laser scanning rates v and hatching coefficients, and selecting the laser scanning rate v and energy E according to the relationship between the scanning speed and the hatching coefficient. p After that, the corresponding hatching coefficient k is selected to predict the width d of the groove ablation. a .

[0011] Furthermore, step S1 specifically includes the following steps:

[0012] Single-point ablation experiments with different laser energies were conducted. When measuring the radius of the point ablation crater, three ablation craters were ablated with the same parameters. Each ablation crater was measured three times. The average of the nine values ​​was the ablation diameter D of the point ablation crater. The ablation radius was calculated as r = D / 2.

[0013] The Gaussian beam used in the experiment has the following energy density F distribution formula in its cross section and peak energy density F0 formula:

[0014]

[0015]

[0016] Where F0 represents the peak energy density of the laser, x represents the distance from the center of the beam, ω represents the laser radius, and E p is the laser energy;

[0017] According to equations (1) and (2), the mathematical relationship between single pulse energy and ablation radius can be obtained as follows:

[0018]

[0019] The experimental data and formula (3) are used to draw a scatter plot and perform linear fitting, and the ablation threshold F of the material is calculated using the slope and intercept. th .

[0020] Furthermore, the laser grooving ablation model established in step S2 includes linear and circular grooving ablation, wherein the circular ablation microelement is equivalent to the linear ablation microelement. x Calculate the total number of pulses n in the laser ablation micro-element area, and calculate the total laser energy density F using the laser energy distribution law. w .

[0021] Furthermore, the total laser energy density F is calculated using the laser energy distribution law. w Specifically:

[0022] For the straight line and circular groove, the laser ablation micro-element area is selected, and then the total number of laser pulses n is obtained according to the set parameters of laser ablation;

[0023] The formula for calculating the total number of laser pulses is as follows:

[0024]

[0025] Where, l x is the selected laser ablation element length, f is the laser action frequency, d a is the laser ablation radius, θ s is the starting ablation angle.

[0026] According to the selected micro-element interval and the total number of pulses, the micro-element area is divided by angle. The formula is as follows:

[0027]

[0028] Where i is the i-th pulse of ablation in the microelement, θ i The angle between the line connecting the laser spot center to the ablation boundary point and the direction perpendicular to the scanning direction, θ p End ablation angle;

[0029] Accumulate the energy of each pulse laser at the ablation boundary point to obtain the total laser energy density F w .

[0030] Furthermore, the energy density F of each pulse at the boundary point i Formula and radius r of the boundary point i and θ i The relationship formula is as follows:

[0031]

[0032]

[0033] According to formulas (5), (6), and (7), the total laser energy density F can be obtained w as follows:

[0034]

[0035] Furthermore, in step S2, after a period of accumulation of pulse laser energy, as shown in formula (9), the energy density F accumulated at a point in the micro-element area is w Reaching the material's ablation threshold F th , the material is ablated. When ablation occurs at this point, and the laser spot center O is exactly on a straight line perpendicular to the scanning path, this point is called the ablation boundary point, and the location of this point is the groove width boundary point of the groove ablation. It can be expressed as follows:

[0036] F w =F th (9).

[0037] Furthermore, step S3 includes the following steps:

[0038] S31, according to the laser scanning rate, select the corresponding hatching coefficient and processing parameters to calculate the groove width d a ;

[0039] S32, perform a slideway ablation test and compare it with the predicted result. If the error is less than 10% of the error setting value, it can be used for actual processing; otherwise, recalculate the hatching coefficient until the error is less than the error setting value.

[0040] The present invention has the following advantages:

[0041] 1. The present invention utilizes the hatching relationship between point ablation and line ablation, analyzes the relationship between laser scanning speed and hatching coefficient, establishes an ablation model based on line ablation and circular ablation, and verifies the effectiveness of the prediction model through experiments.

[0042] 2. The present invention combines ablation time with microscopic ablation pulses, adopts the laser ablation micro-element analysis method, and combines actual experiments with model prediction results based on the fact that the sum of the cumulative energy density of multiple laser pulses is equal to the ablation threshold of the composite material to achieve accurate prediction of the ablation width of the composite material.

[0043] 3. The present invention systematically establishes a femtosecond laser ablation width prediction model for composite materials. Its analysis ideas and methods can be applied to femtosecond laser processing of other composite materials and have universal applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0045] Figure 1 A schematic flow chart of a method for predicting groove width of composite materials by femtosecond laser ablation provided by the present invention.

[0046] Figure 2 Schematic diagram of the femtosecond laser processing platform used in the present invention.

[0047] Figure 3 These are the experimental results of femtosecond laser point ablation. In the figure, (a) shows the point ablation result when the pulse number is 5, and (b) shows the point ablation result when the pulse number is 20.

[0048] Figure 4 This is the relationship between the square of the ablation crater radius and the single pulse energy.

[0049] Figure 5 Schematic diagram of linear ablation and circular ablation.

[0050] Figure 6 Schematic diagram of light spot overlap in the micro-element area.

[0051] Figure 7 Schematic diagram of energy accumulation in the laser ablation micro-element area.

[0052] Figure 8 The results of the groove line ablation experiment are shown, where (a) is a three-dimensional view and (b) is a cross-sectional morphology.

[0053] Figure 9 Comparison chart of predicted results and experimental results. DETAILED DESCRIPTION

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0055] like Figure 1 As shown, the present invention provides a method for predicting groove width of composite materials by femtosecond laser ablation, and the method process includes the following steps:

[0056] Step S1: Perform a femtosecond laser ablation experiment on the composite material to obtain the ablation threshold F of the material. th ;

[0057] Specifically, by Figure 2 The femtosecond laser processing platform shown in the figure was used to conduct femtosecond laser ablation experiments on reaction-sintered silicon carbide (RB-SiC) composite materials. The workpiece was set on a two-dimensional workbench, the output parameters of the laser were controlled by a controller, and the surface image of the workpiece after ablation was obtained by a CCD camera. The femtosecond laser processing platform can output a laser pulse wavelength of 1035nm, a pulse duration of 350fs, a maximum average power of 20W, and a maximum frequency of 100kHz. The experiment was repeated multiple times while changing the laser power alone. The ablation results are shown in Figure 2. Figure 3 As shown in FIG, when measuring the radius of the point ablation pit, three ablation pits are ablated with the same parameters, each ablation pit is measured three times, and the average of the nine values ​​is the ablation diameter D of the point ablation pit. The ablation radius is calculated by r=D / 2.

[0058] The Gaussian beam used in the experiment, the energy density F distribution formula within a single pulse cross section and the peak energy density F0 formula are as follows:

[0059]

[0060]

[0061] Where F0 represents the peak energy density of the laser, x represents the distance from the center of the beam, and ω represents the beam waist radius (1 / e 2 ), E p is the laser energy.

[0062] According to equations (1) and (2), the mathematical relationship between single pulse energy and ablation radius can be obtained as follows:

[0063]

[0064] Using the experimental data and formula (3), a scatter plot is drawn and a linear fit is performed, such as Figure 4 As shown, the ablation threshold F of the material is calculated using the slope and intercept th .

[0065] Specifically, the ablation threshold F of the material is calculated using the slope a and intercept b th , the formula is as follows:

[0066]

[0067] Step S2: Establish a laser groove ablation model, and the total energy density F accumulated at a point in the model micro-element area is w Reaching the material's ablation threshold F th, the material is ablated;

[0068] Specifically, for the linear and circular groove ablation models, the circular ablation radius is much larger than the laser spot radius, so the circular ablation element can be equivalent to the linear ablation element, such as Figure 5 shown.

[0069] For example Figure 6 The laser ablation micro-element area shown is used to obtain the total number of pulses n in the laser ablation micro-element area according to the set parameters of the laser ablation.

[0070] The formula for calculating the total number of laser pulses is as follows:

[0071]

[0072] Where, l x is the selected laser ablation element length, f is the laser action frequency, d a is the laser ablation radius, θ s is the starting ablation angle.

[0073] According to the selected micro-element interval and the total number of pulses, the micro-element area is divided by angle. The formula is as follows:

[0074]

[0075] Where i is the i-th pulse of ablation in the microelement, θ i The angle between the line connecting the laser spot center to the ablation boundary point and the direction perpendicular to the scanning direction, θ p End ablation angle;

[0076] The energy distribution characteristics of a single-point laser spot follow a Gaussian distribution in the radial direction. The closer to the center, the higher the energy density. When the laser spot moves, the energy density of a certain point in the micro-element area will also change. Accumulate the energy of each pulse laser at the ablation boundary point to obtain the total laser energy density F w .

[0077] The energy density F of each pulse at the boundary point i Formula and radius r of the boundary point i and θ i The relationship formula is as follows:

[0078]

[0079]

[0080] According to formulas (5), (6), and (7), the total laser energy density F can be obtained w as follows:

[0081]

[0082] After a period of accumulation of pulse laser energy, as shown in formula (9), the energy density F accumulated at a point in the micro-element area is w Reaching the material's ablation threshold F th , the material is ablated. When ablation occurs at this point, and the laser spot center O is exactly on a straight line perpendicular to the scanning path, this point is called the ablation boundary point, and the location of this point is the groove width boundary point of the groove ablation. It can be expressed as follows:

[0083] F w =F th (9)

[0084] Step S3, performing a groove ablation experiment at different laser scanning rates, such as Figure 8 As shown, the corresponding relationship between different laser scanning rates v and hatching coefficients is obtained;

[0085] According to the relationship between scanning speed and hatching coefficient, the laser scanning rate v and energy E are selected. p After that, the corresponding hatching coefficient k is selected and the groove ablation width d is predicted according to formula (8): a , the laser ablation radius is the ablation width of the groove.

[0086] Conduct groove ablation verification experiments according to the experimental parameters, and repeat multiple groups of verification experiments.

[0087] Finally, the result is Figure 9 As shown, a groove ablation experiment is performed to verify and compare with the predicted results. If the error is less than 10%, it can be used for actual processing and put into practical application. Otherwise, it is necessary to return to step 7 and recalculate the hatching coefficient k.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for predicting groove width of composite materials by femtosecond laser ablation, characterized in that: The steps include: Step S1: Perform femtosecond laser ablation experiments on composite materials to obtain the ablation threshold of the material. ; Step S2: Establish a laser groove ablation model, and the total energy density accumulated at one point in the model micro-element area is Reaching the material's ablation threshold , the material is ablated; Step S3, performing a groove ablation experiment at different laser scanning rates to obtain the different laser scanning rates. v The corresponding relationship between the scanning speed and the hatching coefficient is obtained. When the laser scanning rate is selected, v and energy E p Then, select the corresponding hatching coefficient k , and then predict the width of the groove ablation d a ; The laser grooving ablation model established in step S2 includes linear and circular grooving ablation, wherein the circular ablation microelement is equivalent to the linear ablation microelement. Calculate the total number of pulses in the laser ablation micro-element area , calculate the total laser energy density using the laser energy distribution law ; Calculate the total laser energy density using the laser energy distribution law Specifically: For the straight line and circular groove, select the laser ablation micro-element area, and then obtain the total number of laser pulses according to the set parameters of laser ablation ; The formula for calculating the total number of laser pulses is as follows: Where, is the selected laser ablation element length, is the laser action frequency, is the laser ablation radius, is the starting ablation angle; According to the selected micro-element interval and the total number of pulses, the micro-element area is divided by angle. The formula is as follows: Where, i The first i Second pulse, The angle between the line connecting the center of the laser spot to the ablation boundary point and the direction perpendicular to the scanning direction, End ablation angle; Accumulate the energy of each pulse laser at the ablation boundary point to obtain the total laser energy density F w .

2. The method for predicting groove width of composite materials by femtosecond laser ablation according to claim 1, characterized in that: Step S1 specifically includes the following steps: Single-point ablation experiments with different laser energies were conducted. When measuring the radius of the point ablation crater, three ablation craters were ablated with the same parameters. Each ablation crater was measured three times, and the average of the nine values ​​was the ablation diameter of the point ablation crater. D , the ablation radius passes = D / 2 is calculated; The Gaussian beam used in the experiment has an energy density in its cross section Distribution formula and peak energy density The formula is as follows: In the formula represents the peak energy density of the laser, represents the distance from the center of the beam, represents the laser radius, is the laser energy; According to the formula , the mathematical relationship between single pulse energy and ablation radius can be obtained as follows: The experimental data and formula (3) are used to draw a scatter plot and perform linear fitting, and the ablation threshold of the material is calculated using the slope and intercept. .

3. The method for predicting groove width of composite materials by femtosecond laser ablation according to claim 1, characterized in that: The energy density of each pulse at the boundary point Formula and radius of boundary point and The relationship formula is as follows: According to the formula 、 、 , the total laser energy density can be obtained F w as follows: in, k is the hatching coefficient.

4. The method for predicting groove width of composite materials by femtosecond laser ablation according to claim 3, characterized in that: In step S2, after a period of accumulation of pulse laser energy, as shown in the formula As shown, the energy density accumulated at a point in the micro-element area is F w Reaching the material's ablation threshold , the material is ablated; when ablation occurs at this point, when it is exactly on a straight line perpendicular to the scanning path with the center point O of the laser spot, this point is called the ablation boundary point. The location of this point is the groove width boundary point of the groove ablation, which is expressed by the following formula:

5. The method for predicting groove width of composite materials by femtosecond laser ablation according to claim 4, characterized in that: The step S3 comprises the following steps: S31, according to the laser scanning rate, select the corresponding hatching coefficient and processing parameters to calculate the groove width of the groove ablation d a ; S32, perform a slideway ablation test and compare it with the predicted result. If the error is less than 10% of the error setting value, it can be used for actual processing; otherwise, recalculate the hatching coefficient until the error is less than the error setting value.

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