Method for analyzing laser polishing residual stress of fused quartz through coupling of multiple fields

Abstract

The invention discloses a method for analyzing laser polishing residual stress of fused quartz through multi-field coupling. The method comprises the steps that temperature fields at all moments in the laser polishing process of the fused quartz are obtained through numerical simulation analysis of an equivalent heat conduction coefficient of carbon dioxide laser fusion polishing of the constructed fused quartz; a step of obtaining a hypothetical temperature field representing the fused quartz structure at each moment through numerical simulation analysis of the equivalent structure relaxation time constant of the constructed fused quartz carbon dioxide laser melting polishing; and carrying out numerical simulation analysis through the equivalent thermal expansion coefficient of the constructed frozen temperature field to obtain the residual stress field after fused quartz carbon dioxide laser fusion polishing. The influence of a series of complex physical processes involved in fused quartz carbon dioxide laser melting polishing is avoided, the residual stress is evaluated from fused quartz laser polishing parameters simply and efficiently, and the method is particularly suitable for fused quartz element laser polishing parameter design and residual stress control with extremely high surface quality requirements.

Description

Technical Field

[0001] The invention relates to the technical field of optical element laser polishing, and in particular to a method for analyzing residual stress of fused quartz laser polishing by utilizing multiple field couplings. Background Art

[0002] Fused quartz strongly absorbs carbon dioxide lasers in the infrared band. Laser irradiation with a sufficiently high power density can quickly raise the temperature of fused quartz above its softening point, reduce the viscosity of fused quartz, and close cracks under the action of surface tension to achieve polishing. The literature (Opt. Lett., 43:5777, 2018) reported that carbon dioxide laser polishing reduced the maximum root mean square roughness of the fused quartz surface to 0.156nm, achieving an ultra-smooth surface. Although carbon dioxide laser polishing of fused quartz can effectively improve the surface quality, the residual stress generated by fused quartz after carbon dioxide laser heating treatment not only affects the surface shape of the fused quartz component, but also poses a risk of causing component cracking.

[0003] People have developed a variety of methods to evaluate the residual stress of fused quartz carbon dioxide laser polishing. Gallais et al. (Opt. Express, 17: 23488, 2009) believed that the thermal stress generated in the area between the strain temperature and the softening temperature at the end of the laser action was imprinted in the material to form residual stress during rapid cooling. Based on this model, the optical path difference formed by the simulated residual stress is of the same order of magnitude as the experimental value of the photoelastic method. Vignes et al. (J. Am. Ceram. Soc., 96: 137, 2013) established a structural relaxation and deformation thermodynamic model of fused quartz laser heating from the perspective of the entire process of carbon dioxide laser action on fused quartz, confirmed the heat conduction model by directly measuring the instantaneous temperature distribution, and derived the structural relaxation parameters using spatially resolved confocal Raman spectroscopy to obtain the residual stress distribution. In addition, the inventor team of this application has disclosed a method for obtaining residual stress distribution by measuring the hypothetical temperature distribution state of fused quartz after carbon dioxide laser action in the Chinese authorized invention patent with publication number CN113340504B.

[0004] The above existing methods for analyzing residual stress generated after CO2 laser treatment on fused quartz have some large deviations (the method of Gallais et al.), some complicated processes (the method of Vignes et al.), and some can only perform residual stress analysis after treatment (invention patent CN113340504B), which are difficult to meet the requirements of rapid and accurate evaluation of residual stress of fused quartz CO2 laser polishing.

[0005] The residual stress generated by CO2 laser polishing of fused quartz involves a series of complex physical processes, including the absorption of laser energy by the fused quartz material, thermal stress strain, high-temperature structural relaxation, viscoelasticity, viscoplasticity, molten pool flow, and sudden cooling structural freezing. It is difficult for existing technologies to efficiently extract the precise distribution of residual stress from these complex physical processes. Therefore, new residual stress analysis methods are urgently needed. The residual stress can be evaluated using CO2 laser polishing parameters to meet the urgent need for effective control of residual stress in fused quartz laser polishing. Summary of the invention

[0006] In order to solve the technical problem that it is difficult in the prior art to efficiently extract the precise distribution of residual stress from complex physical processes such as laser energy absorption, thermal stress strain, high-temperature structural relaxation, viscoelasticity, viscoplasticity, molten pool flow and sudden cooling structure freezing, the present invention provides a method for analyzing the residual stress of fused quartz laser polishing using multiple field coupling.

[0007] The technical solution is as follows:

[0008] The first aspect of the present application relates to a method for analyzing residual stress of fused silica laser polishing by using multiple field coupling, which is performed according to the following steps:

[0009] S1. Based on the experimental measurement value of the hypothetical temperature depth distribution of fused quartz, the equivalent thermal conductivity coefficient of carbon dioxide laser melting polishing of fused quartz is constructed. The thermal conduction equation using carbon dioxide laser as the heat source is used to obtain the temperature field at each moment during the fused quartz laser polishing process through numerical simulation analysis.

[0010] S2. According to the experimental measurement value of the hypothetical temperature depth distribution of fused quartz, the equivalent structural relaxation time constant of the carbon dioxide laser melting and polishing of fused quartz is constructed, and the glass structure relaxation equation of the hypothetical temperature needle is used to couple the temperature field at each moment obtained in step S1, and the hypothetical temperature field characterizing the fused quartz structure at each moment is obtained through numerical simulation analysis;

[0011] S3. Consider the hypothetical temperature field as a frozen temperature field, and construct the equivalent thermal expansion coefficient of the frozen temperature field according to the experimental measurement value of the residual stress of fused quartz. Use the thermoelasticity theory to couple the hypothetical temperature field characterizing the fused quartz structure at each moment obtained in step S2, and obtain the residual stress field of the fused quartz after carbon dioxide laser melting and polishing through numerical simulation analysis.

[0012] The above method of analyzing the residual stress of fused quartz laser polishing by using multiple field coupling is extremely simple and greatly simplifies the process of evaluating the residual stress of fused quartz laser polishing. Among them, the method of using equivalent thermal conductivity, equivalent structural relaxation time constant and equivalent thermal expansion coefficient avoids the influence of a series of complex physical processes involved in the carbon dioxide laser melting polishing of fused quartz, and realizes the evaluation of residual stress from fused quartz laser polishing parameters in a simple and efficient way. It is especially suitable for the laser polishing parameter design and residual stress control of fused quartz components with extremely high surface quality requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a time evolution diagram of the temperature field of fused quartz polished by single-point irradiation of a CO2 laser Gaussian spot in Example 1;

[0014] Figure 2 The time evolution diagram of the hypothetical temperature field of the fused quartz polished by the single-point irradiation of the CO2 laser Gaussian spot in Example 1;

[0015] Figure 3 is a hypothetical temperature distribution diagram of the carbon dioxide laser spot in the depth direction of the action center of Example 1;

[0016] Figure 4 The distribution diagram of the radial component σrr and the annular component σθθ of the residual stress field generated by the single-point irradiation polishing of fused quartz by the CO2 laser Gaussian spot in Example 1;

[0017] Figure 5 The distribution diagram of the radial component σrr and the annular component σθθ of the residual stress field generated by the single-point irradiation polishing of fused quartz by a CO2 laser Gaussian spot in Example 2;

[0018] Figure 6 The time evolution diagram of the surface temperature field of the fused quartz sample polished by scanning the strip beam of carbon dioxide laser in Example 3;

[0019] Figure 7 The time evolution diagram of the hypothetical temperature field of the surface of the fused quartz sample polished by scanning the strip beam of carbon dioxide laser in Example 3;

[0020] Figure 8 It is the x-direction component σxx of the residual stress field when the surface of the fused quartz sample is polished by scanning the strip beam of carbon dioxide laser in Example 3. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with embodiments and drawings.

[0022] Embodiment 1:

[0023] A method for analyzing residual stress in fused silica laser polishing using multiple field coupling is performed in the following steps:

[0024] S1. Based on the experimental measurement value of the hypothetical temperature depth distribution of fused quartz, the expression of the equivalent thermal conductivity coefficient k of fused quartz carbon dioxide laser melting and polishing is constructed as follows:

[0025] k=0.00056T+0.4893,300K≤T≤1100K

[0026] k=0.00106T-0.0619,1100K<T≤2500K

[0027] Wherein, T represents temperature, the unit is K, and the unit of equivalent thermal conductivity k is W / (m*K).

[0028] The heat conduction equation of carbon dioxide laser as heat source is:

[0029]

[0030] Where ρ represents the density of fused quartz, C p represents the specific heat capacity of fused quartz, and Q represents the heat source term of the carbon dioxide laser.

[0031] In this embodiment, a carbon dioxide laser with a circular Gaussian spot is used to polish the center of the surface of a circular thin plate structure fused quartz sample. Specifically, a power of 26 W and a Gaussian spot radius of 1.5 mm are used to act on the center of the surface of a circular thin plate structure fused quartz sample with a diameter of 10 mm and a thickness of 4 mm for 4 seconds. The expression of the laser heat source term is:

[0032]

[0033] Wherein, d represents the penetration depth of CO2 laser into fused silica, a represents the beam radius of the focused spot, z represents the depth direction inside the fused silica body, r represents the distance to the center of the laser spot, and I represents the absorbed laser light intensity.

[0034] The expression of absorbed laser light intensity I is:

[0035] I=(1-R)P / (πa 2 )

[0036] Where R represents the reflectivity of fused silica to CO2 laser, and P represents the laser power.

[0037] Through numerical simulation analysis, the temperature field of a fused quartz sample with a circular thin plate structure of 10 mm in diameter and 4 mm in thickness was obtained when a CO2 laser with a circular Gaussian spot was applied at a power of 26 W for 4 seconds and during the cooling process.

[0038] The obtained temperature field evolution is as follows Figure 1 As shown in the figure, it can be clearly observed that during the CO2 laser irradiation, the temperature rises rapidly, the range continues to expand, and the temperature distribution is extremely uneven. The temperature reaches the highest at 4s after the laser action, which is above 2200 K. After the CO2 laser action ends at 4s, the temperature drops rapidly and becomes uniform with thermal diffusion.

[0039] S2. Based on the experimental measurement value of the hypothetical temperature depth distribution of fused quartz, the expression of the equivalent structural relaxation time constant τ(T) of fused quartz CO2 laser melting and polishing is constructed as follows:

[0040] τ(T)=2.8098×10 -23 exp(79322.2452 / T),1315K<T≤1450K

[0041] τ(T)=1.2284×10 -7 exp(27101.9488 / T),1450K<T≤1900K

[0042] τ(T)=4.5728×10 -7 exp(28979.5539 / T),1900K<T≤2350K

[0043] The unit of the equivalent structural relaxation time constant τ(T) is s.

[0044] At a hypothetical temperature T f Characterizing the structure of fused quartz, the time evolution of the fused quartz structure at high temperature obeys the glass structure relaxation equation:

[0045]

[0046] Among them, the hypothetical temperature T f The unit is K.

[0047] The temperature field at each moment obtained by coupling step S1 is used to obtain the hypothetical temperature field at each moment through numerical simulation analysis, and its distribution is as follows: Figure 2 As shown, it can be clearly observed that with the rapid increase in the irradiation temperature of the carbon dioxide laser polishing, the fused quartz structure quickly relaxes to a high temperature state, and the hypothetical temperature value at high temperature keeps up with the actual temperature value. The temperature reaches the highest value when the laser acts for 4s, and the hypothetical temperature also reaches the highest value. In the cooling process after the laser acts for 4s, the high hypothetical temperature state relaxes quickly, and the hypothetical temperature decreases and freezes, and no longer changes with the extension of the cooling time.

[0048] The hypothetical temperature field at each moment is coupled with the temperature field at each moment obtained in step S1, and the hypothetical temperature distribution in the depth direction of the center of the carbon dioxide laser spot is obtained through numerical simulation analysis. The distribution is as follows: Figure 3 As shown, the curve is the coupled simulation result of the temperature field using the equivalent thermal conductivity coefficient and the hypothetical temperature field using the equivalent structural relaxation time constant, and the data points are the experimental measurement results. The coupled simulation results are consistent with the experimental measurement results, which confirms the effectiveness of the constructed equivalent thermal conductivity coefficient and equivalent structural relaxation time constant in obtaining the temperature field and hypothetical temperature field of fused quartz carbon dioxide laser melting polishing.

[0049] S3. Considering the hypothetical temperature field as a frozen temperature field, based on the experimental measurement of the residual stress of fused quartz, the expression of the equivalent thermal expansion coefficient α of the frozen temperature field is constructed as follows:

[0050]

[0051] The unit of α is K. -1 .

[0052] The physical equations in the thermoelastic theory related to the equivalent thermal expansion of the hypothetical temperature field are:

[0053]

[0054] Among them, ε rr , ε θθ , ε zz Respectively represent the coordinate variables r, θ, z components of strain in the cylindrical coordinate system, σ rr , σ θθ , σ zz They represent the coordinate variables r, θ, and z in the cylindrical coordinate system, respectively, and the components of stress, E represents Young's modulus, ν represents Poisson's ratio, and ΔT f The difference between the hypothetical temperature field generated after CO2 laser melting and polishing of fused silica and the initial hypothetical temperature field before polishing.

[0055] By using the thermoelastic theory, the initial hypothetical temperature field of the fused quartz before CO2 laser melting and polishing obtained in step S2 is coupled with the final hypothetical temperature field after CO2 laser melting and polishing of the fused quartz, and the residual stress field of the fused quartz with a circular thin plate structure after CO2 laser melting and polishing with a circular Gaussian spot is obtained through numerical simulation analysis, as shown in FIG. Figure 4 shown.

[0056] It can be clearly observed from the residual stress field of fused quartz CO2 laser single-point irradiation polishing that the radial stress and hoop stress in the center area of ​​CO2 laser irradiation both reach 26MPa, which is consistent with the result reported in the literature (Proc. SPIE 7504:750410, 2009) that the maximum hoop stress of fused quartz treated with CO2 laser single-point irradiation can reach 29MPa.

[0057] Embodiment 2:

[0058] The main steps of this embodiment are exactly the same as those of Embodiment 1, except that: in step S1, a residual stress field is generated by applying a carbon dioxide laser with a circular Gaussian spot to a fused quartz sample with a circular thin plate structure at a power of 26 W for 4 seconds, and then the power is linearly reduced from 20 W to 6.25 W within 10 seconds for laser annealing.

[0059] The residual stress field of fused silica after CO2 laser melting and polishing and laser annealing is shown in Figure 2. Figure 5 As shown in Figure 2, the radial stress and hoop stress in the center area of ​​the carbon dioxide laser irradiation were reduced to 11 MPa, and laser annealing effectively suppressed the residual stress.

[0060] Embodiment 3:

[0061] The main steps of this embodiment are exactly the same as those of Embodiment 1, except that in step S1, for a fused quartz sample with a rectangular thin plate structure of 20 mm in length, 20 mm in width, and 4 mm in thickness, a strip-shaped Gaussian beam of 20 mm in length and 1 mm in width is formed by a carbon dioxide laser with a power of 80 W to scan and polish the surface of the entire fused quartz sample along the width direction of the fused quartz sample at a speed of 0.5 mm / s.

[0062] The expression of the laser heat source term is:

[0063]

[0064] Wherein, a0 represents the width of the strip Gaussian beam, x represents the coordinate variable of the rectangular coordinate system, V represents the scanning speed of the strip Gaussian beam on the fused silica surface along the x direction, and t represents the scanning time.

[0065] The expression of absorbed laser light intensity I is:

[0066] I=(1-R)P / (2a0L)

[0067] Where L is the length of the Gaussian beam.

[0068] The temperature field generated by scanning a polished rectangular thin plate structure fused quartz sample with a CO2 laser strip Gaussian beam at a set speed is obtained through numerical simulation analysis. Figure 6 It can be clearly observed that the temperature of the irradiated area rises rapidly during the CO2 laser scanning, reaching more than 2000K. After the beam scans, the temperature drops rapidly, and the temperature field distribution is extremely uneven. After the scanning and polishing of the fused quartz sample, the temperature drops and becomes uniform as the heat diffuses.

[0069] In step S2, the hypothetical temperature field at each moment obtained is coupled with the temperature field at each moment obtained in step S1, and the hypothetical temperature distribution in the depth direction after the CO2 laser strip Gaussian beam scans and polishes the surface of the entire fused quartz sample is obtained through numerical simulation analysis, such as Figure 7 As shown, it can be clearly observed that after the strip-shaped carbon dioxide laser scanning polishing, a layer of imaginary temperature increase area is generated on the surface of the fused quartz, which is permanently frozen on the surface of the fused quartz sample.

[0070] In step S3, the physical equation in the thermoelastic theory and the term related to the equivalent thermal expansion of the hypothetical temperature field are:

[0071]

[0072] Among them, ε xx , ε yy Respectively represent the coordinate variables x and y in the rectangular coordinate system, and σ xx , σ yy They represent the coordinate variables x and y stress components in the rectangular coordinate system respectively.

[0073] By using the thermoelastic theory, the initial hypothetical temperature field obtained in step S2 before the CO2 laser strip Gaussian beam scans and polishes the entire fused quartz sample surface is coupled with the final hypothetical temperature field after the CO2 laser strip Gaussian beam scans and polishes the entire fused quartz sample surface, and the residual stress field of the rectangular thin plate structure fused quartz after the CO2 laser strip Gaussian beam scans and polishes the entire block is obtained through numerical simulation analysis, as shown in FIG. Figure 8 As shown, it can be clearly observed that residual stress up to 10 MPa is formed on the surface of fused quartz after scanning polishing.

[0074] Therefore, the method of analyzing the residual stress of fused quartz laser polishing by using multiple field coupling is extremely simple and convenient, which greatly simplifies the process of evaluating the residual stress of fused quartz laser polishing. Among them, the method of using equivalent thermal conductivity, equivalent structural relaxation time constant and equivalent thermal expansion coefficient avoids the influence of a series of complex physical processes involved in the carbon dioxide laser melting polishing of fused quartz, and realizes the evaluation of residual stress from fused quartz laser polishing parameters in a simple and efficient way. It is especially suitable for the laser polishing parameter design and residual stress control of fused quartz components with extremely high surface quality requirements.

[0075] Finally, it should be noted that the above description is only a preferred embodiment of the present invention. Under the guidance of the present invention, ordinary technicians in this field can make various similar expressions without violating the purpose and claims of the present invention, and such changes all fall within the scope of protection of the present invention.

Claims

1. A method for analyzing residual stress in fused silica laser polishing using multiple field coupling, It is characterized in that Follow these steps: S1. Based on the experimental measurement value of the hypothetical temperature depth distribution of fused quartz, the equivalent thermal conductivity coefficient of carbon dioxide laser melting polishing of fused quartz is constructed. The thermal conduction equation using carbon dioxide laser as the heat source is used to obtain the temperature field at each moment during the fused quartz laser polishing process through numerical simulation analysis. S2. According to the experimental measurement value of the hypothetical temperature depth distribution of fused quartz, the equivalent structural relaxation time constant of the carbon dioxide laser melting and polishing of fused quartz is constructed, and the glass structure relaxation equation of the hypothetical temperature needle is used to couple the temperature field at each moment obtained in step S1, and the hypothetical temperature field characterizing the fused quartz structure at each moment is obtained through numerical simulation analysis; S3. Consider the hypothetical temperature field as a frozen temperature field, and construct the equivalent thermal expansion coefficient of the frozen temperature field according to the experimental measurement value of the residual stress of fused quartz. Use the thermoelasticity theory to couple the hypothetical temperature field characterizing the fused quartz structure at each moment obtained in step S2, and obtain the residual stress field of the fused quartz after carbon dioxide laser melting and polishing through numerical simulation analysis.

2. The method for analyzing residual stress of fused silica laser polishing by using multiple field coupling according to claim 1, It is characterized in that In step S1, the expression of the equivalent thermal conductivity coefficient k of fused silica carbon dioxide laser melting and polishing is constructed as follows: k=0.00056T+0.4893,300K≤T≤1100K k=0.00106T-0.0619,1100K<T≤2500K Wherein, T represents temperature; The heat conduction equation of carbon dioxide laser as heat source is: Where ρ represents the density of fused quartz, C p represents the specific heat capacity of fused quartz, Q represents the heat source term of carbon dioxide laser; The center of the surface of a circular thin-plate fused quartz sample is polished using a CO2 laser with a circular Gaussian spot. The expression of the laser heat source term is: Wherein, d represents the penetration depth of CO2 laser into fused silica, a represents the beam radius of the focused spot, z represents the depth direction inside the fused silica body, r represents the distance to the center of the laser spot, and I represents the absorbed laser light intensity; The expression of absorbed laser light intensity I is: I=(1-R)P / (πa 2 ) Where R represents the reflectivity of fused silica to CO2 laser, and P represents the laser power; The temperature field of a fused quartz sample with a circular thin plate structure subjected to a CO2 laser with a circular Gaussian spot at the first set power for the first set time and during the cooling process is obtained through numerical simulation analysis.

3. The method for analyzing residual stress of fused silica laser polishing by using multiple field coupling according to claim 1, It is characterized in that In step S1, the expression of the equivalent thermal conductivity coefficient k of fused silica carbon dioxide laser melting and polishing is constructed as follows: k=0.00056T+0.4893,300K≤T≤1100K k=0.00106T-0.0619,1100K<T≤2500K Wherein, T represents temperature; The heat conduction equation of carbon dioxide laser as heat source is: Where ρ represents the density of fused quartz, C p represents the specific heat capacity of fused quartz, Q represents the heat source term of carbon dioxide laser; The center of the surface of a circular thin-plate fused quartz sample is polished using a CO2 laser with a circular Gaussian spot. The expression of the laser heat source term is: Wherein, d represents the penetration depth of CO2 laser into fused silica, a represents the beam radius of the focused spot, z represents the depth direction inside the fused silica body, r represents the distance to the center of the laser spot, and I represents the absorbed laser light intensity; The expression of absorbed laser light intensity I is: I=(1-R)P / (πa 2 ) Where R represents the reflectivity of fused silica to CO2 laser, and P represents the laser power; Through numerical simulation analysis, the residual stress field generated by a carbon dioxide laser with a circular Gaussian spot acting on a circular thin plate structure fused quartz sample is obtained by first acting at a first set power for a first set time and then linearly reducing the power from the second set power to a third set power for laser annealing within a second set time, wherein the first set power is greater than the second set power, and the second set power is greater than the third set power.

4. The method for analyzing residual stress of fused silica laser polishing by using multiple field coupling according to claim 2 or 3, It is characterized in that In step S2, the expression of the equivalent structural relaxation time constant τ(T) of the carbon dioxide laser melting and polishing of fused silica is constructed as follows: τ(T)=2.8098×10 -23 exp(79322.2452 / T),1315K<T≤1450K τ(T)=1.2284×10 -7 exp(27101.9488 / T),1450K<T≤1900K τ(T)=4.5728×10 -7 exp(28979.5539 / T),1900K<T≤2350K At a hypothetical temperature T f Characterizing the structure of fused quartz, the time evolution of the fused quartz structure at high temperature obeys the glass structure relaxation equation: The temperature field at each moment obtained in step S1 is coupled to obtain the hypothetical temperature field at each moment through numerical simulation analysis; The obtained hypothetical temperature field at each moment is coupled with the temperature field at each moment obtained in step S1, and the hypothetical temperature distribution in the depth direction of the center of action of the carbon dioxide laser spot is obtained through numerical simulation analysis.

5. The method for analyzing residual stress of fused silica laser polishing by using multiple field coupling according to claim 4, It is characterized in that In step S3, the expression of the equivalent thermal expansion coefficient α of the constructed frozen temperature field is: The physical equations in the thermoelastic theory related to the equivalent thermal expansion of the hypothetical temperature field are: Among them, ε rr , ε θθ , ε zz Respectively represent the coordinate variables r, θ, z components of strain in the cylindrical coordinate system, σ rr , σ θθ , σ zz They represent the coordinate variables r, θ, and z in the cylindrical coordinate system, respectively, and the components of stress, E represents Young's modulus, ν represents Poisson's ratio, and ΔT f The difference between the hypothetical temperature field generated after CO2 laser melting and polishing of fused silica and the initial hypothetical temperature field before polishing; By using the thermoelastic theory, the initial hypothetical temperature field of the fused quartz before the CO2 laser melting and polishing obtained in step S2 is coupled with the final hypothetical temperature field after the CO2 laser melting and polishing of the fused quartz, and the residual stress field of the fused quartz with a circular thin plate structure after the CO2 laser melting and polishing with a circular Gaussian spot is obtained through numerical simulation analysis.

6. The method for analyzing residual stress of fused silica laser polishing by using multiple field coupling according to claim 1, It is characterized in that In step S1, the expression of the equivalent thermal conductivity coefficient k of fused silica carbon dioxide laser melting and polishing is constructed as follows: k=0.00056T+0.4893,300K≤T≤1100K k=0.00106T-0.0619,1100K<T≤2500K Wherein, T represents temperature; The heat conduction equation of carbon dioxide laser as heat source is: Where ρ represents the density of fused quartz, C p represents the specific heat capacity of fused quartz, Q represents the heat source term of carbon dioxide laser; For a rectangular thin plate fused quartz sample, a strip Gaussian beam with the same length as one side of the fused quartz sample is used to scan and polish the surface of the entire fused quartz sample. The expression of the laser heat source term is: Among them, a 0 represents the width of the strip Gaussian beam, x represents the coordinate variable of the rectangular coordinate system, V represents the scanning speed of the strip Gaussian beam along the x direction on the fused quartz surface, and t represents the scanning time; The expression of absorbed laser light intensity I is: I=(1-R)P / (2a 0 L) Where L represents the length of the strip Gaussian beam; The temperature field generated by a CO2 laser strip Gaussian beam scanning a polished rectangular thin plate structure fused quartz sample at a set speed is obtained through numerical simulation analysis.

7. The method for analyzing residual stress of fused silica laser polishing by using multiple field coupling according to claim 6, It is characterized in that In step S2, the expression of the equivalent structural relaxation time constant τ(T) of the carbon dioxide laser melting and polishing of fused silica is constructed as follows: τ(T)=2.8098×10 -23 exp(79322.2452 / T),1315K<T≤1450K τ(T)=1.2284×10 -7 exp(27101.9488 / T),1450K<T≤1900K τ(T)=4.5728×10 -7 exp(28979.5539 / T),1900K<T≤2350K At a hypothetical temperature T f Characterizing the structure of fused quartz, the time evolution of the fused quartz structure at high temperature obeys the glass structure relaxation equation: The temperature field at each moment obtained in step S1 is coupled to obtain the hypothetical temperature field at each moment through numerical simulation analysis; The obtained hypothetical temperature field at each moment is coupled with the temperature field at each moment obtained in step S1, and the hypothetical temperature distribution in the depth direction after the CO2 laser strip Gaussian beam scans and polishes the surface of the entire fused quartz sample is obtained through numerical simulation analysis.

8. The method for analyzing residual stress of fused silica laser polishing by using multiple field coupling according to claim 7, It is characterized in that In step S3, the expression of the equivalent thermal expansion coefficient α of the constructed frozen temperature field is: The physical equations in the thermoelastic theory related to the equivalent thermal expansion of the hypothetical temperature field are: Among them, ε xx , ε yy Respectively represent the coordinate variables x and y in the rectangular coordinate system, and σ xx , σ yy They represent the coordinate variables x and y stress components in the rectangular coordinate system respectively; By using the thermoelastic theory, the initial hypothetical temperature field obtained in step S2 before the CO2 laser strip Gaussian beam scans and polishes the surface of the entire fused quartz sample is coupled with the final hypothetical temperature field after the CO2 laser strip Gaussian beam scans and polishes the surface of the entire fused quartz sample, and the residual stress field of the rectangular thin plate structure fused quartz after the CO2 laser strip Gaussian beam scans and polishes the entire piece is obtained through numerical simulation analysis.

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