A simulation analysis method for internal stress of cultural relics

Abstract

The present invention discloses a method for simulating and analyzing the internal stress of cultural relics, comprising: step 1, obtaining the solid area of ​​the cultural relics and the air flow area of ​​the environment in which the cultural relics are located; step 2, based on the air flow area and the solid area of ​​the cultural relics in the environment in which the cultural relics are located, establishing a fluid model, a solid thermal model of the cultural relics and a solid structural model of the cultural relics in the environment; step 3, establishing a bidirectional coupling relationship between the fluid model and the solid thermal model of the cultural relics, establishing a unidirectional coupling relationship between the fluid model and the solid structural model of the cultural relics, and establishing a unidirectional coupling relationship between the solid thermal model of the cultural relics and the solid structural model of the cultural relics; step 4, performing fluid-heat-solid coupling calculation to obtain the internal stress distribution of the cultural relics in each time step. The present invention can accurately obtain the internal stress distribution of the cultural relics under the joint action of multiple environmental factors, which is convenient for accurately judging the preservation state of the cultural relics.

Description

Technical Field

[0001] The invention belongs to the field of cultural relic safety status assessment, and in particular relates to a cultural relic internal stress simulation analysis method. Background Art

[0002] The preservation state and lifespan of cultural relics are affected by many factors in their environment. Among them, the most critical factors include temperature and light. The protection of cultural relics, especially the protection of cultural relics (solid) placed in an open-air environment, requires comprehensive consideration of the impact of various environmental factors on cultural relics; among them, the internal stress (corresponding to the thermal-mechanical effect) caused by wind and sun exposure is an important factor affecting the safety of cultural relics.

[0003] Theoretically, when wind blows over the surface of a cultural relic, the speed of heat convection will increase; therefore, when there is wind, the surface temperature of the cultural relic and the thermal stress inside it will be different. In addition, the greater the difference between the surface temperature of the cultural relic and the air temperature, the faster the cultural relic dissipates heat to the air, so the ambient temperature also has a certain influence on the surface temperature of the cultural relic and the distribution of its internal stress.

[0004] At present, the analysis of the thermal-mechanical effects of cultural relics is mostly qualitative analysis or single-factor (considering only solar radiation) thermal simulation experiments, which does not fully consider the combined effects of solar radiation, wind and air temperature. It cannot accurately evaluate the thermal-mechanical effects of cultural relics under the combined action of multiple environmental factors, and is not conducive to accurately judging the preservation status of cultural relics. Summary of the invention

[0005] The purpose of the present invention is to provide a method for simulating and analyzing the internal stress of cultural relics, so as to accurately obtain the internal stress distribution of cultural relics under the combined action of multiple environmental factors, so as to accurately judge the preservation status of cultural relics.

[0006] The method for simulating and analyzing internal stress of cultural relics of the present invention comprises:

[0007] Step 1: Obtain the solid area of ​​the cultural relics and the air flow area of ​​the environment where the cultural relics are located.

[0008] Step 2: Based on the air flow area and the solid area of ​​the cultural relics, a fluid model, a solid thermal model and a solid structural model of the cultural relics are established.

[0009] Step three: establish a bidirectional coupling relationship between the fluid model and the solid thermal model of the cultural relic, establish a unidirectional coupling relationship between the fluid model and the solid structural model of the cultural relic, and establish a unidirectional coupling relationship between the solid thermal model of the cultural relic and the solid structural model of the cultural relic.

[0010] Step 4: Perform fluid-heat-solid coupling calculation to obtain the internal stress distribution of the cultural relics at each time step.

[0011] Preferably, the step of establishing a fluid model of the environment in which the cultural relics are located comprises:

[0012] S11. Divide the air flow area of ​​the environment where the cultural relics are located into a plurality of volume grids to obtain air volume grids.

[0013] S12. Import the air body grid into the fluid analysis module, and set boundary conditions, initial conditions and air physical property parameters related to fluid analysis in the fluid analysis module.

[0014] Preferably, the boundary conditions related to fluid analysis include: air flow velocity, air flow direction, inflow air temperature, air pressure, return air temperature, solar radiation intensity and solar radiation direction.

[0015] The method for setting boundary conditions related to fluid analysis is:

[0016] The air flow velocity, air flow direction and temperature of the inflowing air are set on the Z+ boundary surface of the air flow area.

[0017] The air pressure and the temperature of the return air are set at the Z boundary surface of the air flow area.

[0018] The contact surface between air and the solid cultural relic is set as the fluid-solid interface, and the solar radiation intensity and solar radiation direction are set on the fluid-solid interface.

[0019] The initial conditions include initial air pressure, initial air temperature, initial air flow velocity and initial air flow direction.

[0020] The air physical property parameters include air density, air thermal expansion coefficient, air viscosity and air specific heat.

[0021] Preferably, the step of establishing a solid thermal model of cultural relics comprises:

[0022] S21. Divide the solid area of ​​the cultural relic into m individual grids to obtain a cultural relic object grid.

[0023] S22, import the cultural relic body grid into the cultural relic solid thermal analysis module, and set the cultural relic physical property parameters related to thermal analysis, n cultural relic surface initial temperatures and m cultural relic internal initial temperatures in the cultural relic solid thermal analysis module. Among them, the cultural relic physical property parameters related to thermal analysis include the density of the cultural relic, the thermal conductivity of the cultural relic, the specific heat of the cultural relic and the thermal expansion coefficient of the cultural relic. Since there are n surface grid measurement points on the surface of the cultural relic, n cultural relic surface initial temperatures are set. Since there are m individual grids in the solid area of ​​the cultural relic, m cultural relic internal initial temperatures are set.

[0024] Preferably, the step of establishing the solid structure model of the cultural relic includes:

[0025] S31. Divide the solid area of ​​the cultural relic into m individual grids to obtain a cultural relic body grid.

[0026] S32, importing the cultural relic body grid into the cultural relic solid structure analysis module, and setting the cultural relic physical property parameters related to the structural analysis in the cultural relic solid structure analysis module. The cultural relic physical property parameters related to the structural analysis include the Young's modulus and the Poisson's ratio of the cultural relic.

[0027] S33. Set the part where the bottom of the cultural relic is connected to the ground as a fixed constraint in the structural analysis.

[0028] Preferably, the bidirectional coupling relationship between the fluid model and the solid thermal model of the cultural relic is established in step 3 as follows:

[0029] A bidirectional data transmission channel is established between the fluid model and the solid thermal model of the cultural relic, so as to transmit the n convective heat transfer coefficients on the fluid-solid interface, the n solar radiation amounts on the fluid-solid interface and the n air temperatures of a thin layer on the surface of the cultural relic calculated by the fluid analysis module at each step to the solid thermal analysis module of the cultural relic, and to transmit the n initial surface temperatures of the cultural relic set in the solid thermal analysis module of the cultural relic and the n surface temperatures of the cultural relic calculated at each step to the fluid analysis module.

[0030] Preferably, the method of establishing the one-way coupling relationship between the fluid model and the solid structure model of the cultural relic in step 3 is:

[0031] A one-way data transmission channel is established between the fluid model and the solid structure model of the cultural relic, so as to transmit the n cultural relic surface pressures (i.e., the pressure values ​​of the n surface grid measurement points on the cultural relic surface) calculated by the fluid analysis module at each step to the cultural relic solid structure analysis module. The n cultural relic surface pressures reflect the pressure distribution on the cultural relic surface.

[0032] Preferably, the method of establishing the one-way coupling relationship between the solid thermal model of the cultural relic and the solid structural model of the cultural relic in step 3 is:

[0033] A one-way data transmission channel between the solid thermal model of cultural relics and the solid structural model of cultural relics is established to transmit the m internal temperatures of cultural relics calculated by the solid thermal analysis module of cultural relics to the solid structural analysis module of cultural relics at each step. The m internal temperatures of cultural relics reflect the temperature distribution inside the cultural relics.

[0034] Preferably, the step of performing fluid-heat-solid coupling calculation to obtain the internal stress distribution of the cultural relic in each time step includes:

[0035] S41. Set the total calculation time, the step size of each time step, and the number of iterations.

[0036] S42. In the first time step, the fluid analysis module substitutes the boundary conditions, air physical parameters, initial conditions and initial temperatures of n cultural relics surfaces related to fluid analysis into the Navier-Stokes partial differential equations, and solves the air velocity, air flow direction, air temperature, air pressure and n convective heat transfer coefficients h at each grid point in the air flow area in the first time step. air_1 , n solar radiation q rad_1 And the n air temperatures T of a thin layer on the surface of the artifact in the first time step air_1 、n cultural relics surface pressure P surf_1 .

[0037] S43. In the first time step, the cultural relic solid thermal analysis module calculates the cultural relic physical property parameters related to thermal analysis, n cultural relic surface initial temperatures, m cultural relic internal initial temperatures, n convection heat transfer coefficients h air_1 , n solar radiation q rad_1 and n air temperatures T air_1 , substitute into the partial differential equation of heat conduction, and solve to obtain the surface temperature T of n cultural relics in the first time step sol-surf_1 and the internal temperature of m artifacts T sol-body_1 .

[0038] S44. In the first time step, the cultural relic solid structure analysis module calculates the cultural relic physical property parameters related to the structural analysis, the surface pressure P of n cultural relics, and the surf_1 and the internal temperature of m artifacts T sol-body_1 , substituted into the Navier equation, and the internal stress P of m cultural relics in the first time step is obtained. body_1 The internal stress of m cultural relics reflects the internal stress distribution of cultural relics, which is the final manifestation of the thermal-mechanical effect of cultural relics.

[0039] S45. In the i-th time step, the fluid analysis module calculates the boundary conditions related to the fluid analysis, the air physical parameters, the air velocity, air flow direction, air temperature, air pressure of each grid point in the air flow area in the i-1th time step, and the surface temperature T of n cultural relics in the i-1th time step. sol-surf_i-1 , substituting into the Navier-Stokes partial differential equations, the air velocity, air flow direction, air temperature, air pressure of each grid point in the air flow area in the i-th time step and the n convective heat transfer coefficients h on the fluid-solid interface in the i-th time step are obtained. air_i , n solar radiation q rad_i And the n air temperatures T of a thin layer on the surface of the artifact in the i-th time step air_i 、n cultural relics surface pressure P surf_i; Wherein, i takes all integers from 2 to j in turn, j represents the total number of steps, j is an integer and j = total duration ÷ step length.

[0040] S46. In the i-th time step, the cultural relic solid thermal analysis module converts the cultural relic physical property parameters related to thermal analysis and the surface temperature T of n cultural relics in the i-1th time step into sol-surf_i-1 , the internal temperature T of m cultural relics in the i-1th time step sol-body_i-1 , n convection heat transfer coefficients h air_i , n solar radiation q rad_i and n air temperatures T air_i , substitute into the partial differential equation of heat conduction, and solve to obtain the surface temperature T of n cultural relics in the i-th time step sol-surf_i and the internal temperature of m artifacts T sol-body_i .

[0041] S47, in the i-th time step, the cultural relic solid structure analysis module will be related to the structure analysis of the cultural relic physical parameters, n cultural relic surface pressure P surf_i and the internal temperature of m artifacts T sol-body_i , substituted into the Navier equation, and the internal stress P of m cultural relics in the i-th time step is obtained. body_i The internal stress of m cultural relics reflects the internal stress distribution of cultural relics, which is the final manifestation of the thermal-mechanical effect of cultural relics.

[0042] Preferably, the step of obtaining the solid area of ​​the cultural relic and the air flow area of ​​the environment where the cultural relic is located in step 1 comprises:

[0043] P1. Perform three-dimensional scanning on cultural relics to obtain point cloud data on the surface of cultural relics.

[0044] P2. Convert the point cloud data into a surface mesh of the cultural relic surface in finite element pre-processing software.

[0045] P3. Create a rectangular area in the fluid simulation software, import the surface grid, set the area within the surface grid as the solid area of ​​the cultural relic, subtract the solid area of ​​the cultural relic from the rectangular area, and obtain the air flow area of ​​the environment where the cultural relic is located.

[0046] The present invention breaks through the limitation of single factor analysis in existing research on the thermal-mechanical effect of cultural relics, comprehensively considers the influence of multiple environmental factors (such as air flow caused by wind and solar radiation caused by sun exposure) on the cultural relics, and uses the fluid-heat-solid coupling analysis method to simulate and establish a coupling correlation model between cultural relics and the environment (i.e., the fluid model of the environment in which the cultural relics are located, the solid thermal model of the cultural relics, and the solid structural model of the cultural relics), accurately obtains the internal stress distribution of the cultural relics under the joint action of multiple environmental factors, so as to more accurately judge the preservation state of the cultural relics. According to the results of the internal stress distribution of the cultural relics, the fragile parts of the cultural relics can be judged, and combined with the characteristics of the cultural relics materials, it can be judged whether the cultural relics will fail due to stress beyond their tolerance (such as whether they will be deformed or broken), which is conducive to providing more accurate data support for the preservation and restoration of cultural relics. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 Flow chart of the method for simulating and analyzing the internal stress of cultural relics in an embodiment of the present invention.

[0048] Figure 2 It is a schematic diagram of the coupling relationship between the fluid model of the environment in which the cultural relics are located, the solid thermal model of the cultural relics, and the solid structural model of the cultural relics in an embodiment of the present invention.

[0049] Figure 3 The figure is a flow chart of the fluid-heat-solid coupling calculation in the embodiment of the present invention.

[0050] Figure 4 Schematic diagram of the fluid model of the environment in which the cultural relics are located in an embodiment of the present invention.

[0051] Figure 5 This is a schematic diagram of the temperature distribution results on a cross section of the air flow area of ​​the environment where the cultural relics are located after being exposed to wind and sun for 8 hours in an embodiment of the present invention.

[0052] Figure 6 This is a schematic diagram of the pressure distribution on the surface of the cultural relic after being exposed to wind and sun for 8 hours in an embodiment of the present invention.

[0053] Figure 7 This is a schematic diagram of the temperature distribution inside the cultural relic after being exposed to wind and sun for 8 hours in an embodiment of the present invention.

[0054] Figure 8 This is a schematic diagram of the stress distribution results of the cultural relics after being exposed to wind and sun for 8 hours in an embodiment of the present invention. DETAILED DESCRIPTION

[0055] In order to enable a more detailed understanding of the features and technical contents of the embodiments of the present invention, the implementation of the embodiments of the present invention is described in detail below in conjunction with the accompanying drawings. The attached drawings are for reference only and are not intended to limit the embodiments of the present invention.

[0056] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein are only for the purpose of describing the embodiments of the present invention and are not intended to limit the present invention.

[0057] In the following description, reference is made to “some embodiments”, which describe a subset of all possible embodiments, but it will be understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0058] like Figures 1 to 3 As shown, the method for simulating and analyzing the internal stress of cultural relics in the embodiment of the present invention includes:

[0059] Step 1: Obtain the solid area of ​​the cultural relics and the air flow area of ​​the environment where the cultural relics are located.

[0060] In some embodiments, the specific method of obtaining the solid area of ​​the cultural relic and the air flow area of ​​the environment where the cultural relic is located includes the following steps:

[0061] P1. (Use laser scanner) perform three-dimensional scanning on cultural relics to obtain point cloud data of the surface of cultural relics.

[0062] P2. Convert the point cloud data of the cultural relic surface into the surface mesh of the cultural relic surface in the finite element pre-processing software Hypermesh.

[0063] P3. Create a rectangular area in the fluid simulation software Ansys Fluent, import the surface mesh of the cultural relic, set the area within the surface mesh of the cultural relic as the solid area of ​​the cultural relic, subtract the solid area of ​​the cultural relic from the rectangular area, and obtain the air flow area of ​​the environment where the cultural relic is located.

[0064] Step 2: Based on the air flow area and solid area of ​​the cultural relics, the fluid model, solid thermal model and solid structural model of the cultural relics are established. The fluid model, solid thermal model and solid structural model of the cultural relics are established in Ansys software.

[0065] In some embodiments, a fluid model of the environment in which the artifact is located is established (see Figure 4 ) steps include:

[0066] S11. Divide the air flow area of ​​the environment where the cultural relics are located into a plurality of volume grids to obtain air volume grids.

[0067] S12. Import the air body grid into the fluid analysis module, and set boundary conditions, initial conditions and air physical property parameters related to fluid analysis in the fluid analysis module.

[0068] Among them, the boundary conditions related to fluid analysis include: air flow velocity, air flow direction, inflow air temperature, air pressure, return air temperature, solar radiation intensity and solar radiation direction.

[0069] The initial conditions include the initial air pressure (atmospheric pressure), the initial air temperature (the air temperature at the initial moment of the air flow area in the environment where the cultural relics are located), the initial air flow velocity and the initial air flow direction.

[0070] Air physical parameters include air density, air thermal expansion coefficient, air viscosity and air specific heat. As an example, the air density is 1.185 kg / m 3 , the thermal expansion coefficient of air is 0.00335 (1 / k), and the viscosity of air is 1.7894e -5 kg / ms, and the specific heat of air is 1006.43 J / kg·K.

[0071] The air flow area of ​​the environment where the cultural relics are located has six boundary surfaces, namely X+, X-, Y+, Y-, Z+, and Z-. X+, X-, and Y+ are set as symmetric boundary surfaces, and Y- is set as a wall boundary surface.

[0072] In some embodiments, the method for setting boundary conditions related to fluid analysis is:

[0073] The air flow velocity, air flow direction and temperature of the inflowing air are set on the Z+ boundary surface of the air flow area of ​​the environment where the cultural relics are located, in order to describe the inflow of air.

[0074] The air pressure and the temperature of the return air are set on the Z-boundary surface of the air flow area of ​​the environment where the cultural relics are located, in order to describe the outflow of air.

[0075] The contact surface between air and the solid object is set as the fluid-solid interface, and the solar radiation intensity and direction are set on the fluid-solid interface. The fluid-solid interface is used for data exchange between subsequent models.

[0076] The fluid model of the environment in which the cultural relics are located is used to study the impact of air flow velocity, air flow direction, air temperature and solar radiation intensity on the cultural relics and their environment.

[0077] In some embodiments, the step of establishing a solid thermal model of the cultural relic includes:

[0078] S21. Divide the solid area of ​​the cultural relic into m individual grids to obtain a cultural relic object grid.

[0079] S22, import the cultural relic body grid into the cultural relic solid thermal analysis module, and set the cultural relic physical property parameters related to thermal analysis, n cultural relic surface initial temperatures and m cultural relic internal initial temperatures in the cultural relic solid thermal analysis module. Among them, the cultural relic physical property parameters related to thermal analysis include the density of the cultural relic, the thermal conductivity of the cultural relic, the specific heat of the cultural relic and the thermal expansion coefficient of the cultural relic, and their values ​​are all constants. Since there are n surface grid measurement points on the surface of the cultural relic, n cultural relic surface initial temperatures are set. Since there are m individual grids in the solid area of ​​the cultural relic, m cultural relic internal initial temperatures are set. As an example, the values ​​of the n cultural relic surface initial temperatures and the m cultural relic internal initial temperatures are the same.

[0080] In some embodiments, the step of establishing a solid structure model of a cultural relic includes:

[0081] S31. Divide the solid area of ​​the cultural relic into m individual grids to obtain a cultural relic body grid.

[0082] S32, importing the cultural relic body grid into the cultural relic solid structure analysis module, and setting the cultural relic physical property parameters related to the structural analysis in the cultural relic solid structure analysis module. The cultural relic physical property parameters related to the structural analysis include the Young's modulus and the Poisson's ratio of the cultural relic, both of which are constants.

[0083] S33. Set the part where the bottom of the cultural relic is connected to the ground as a fixed constraint in the structural analysis.

[0084] Step 3: Establish a bidirectional coupling relationship between the fluid model of the environment in which the cultural relics are located and the solid thermal model of the cultural relics, establish a unidirectional coupling relationship between the fluid model of the environment in which the cultural relics are located and the solid structural model of the cultural relics, and establish a unidirectional coupling relationship between the solid thermal model of the cultural relics and the solid structural model of the cultural relics. The flow and heat transfer of air, the heat transfer inside the cultural relics, and the mechanical properties inside the cultural relics work together (for example, the flow of air will affect the distribution of heat inside the cultural relics, and the flow of air will affect the distribution of stress inside the cultural relics), which is reflected in this fluid-heat-solid coupling relationship, which is established in the Ansys software.

[0085] In some embodiments, the bidirectional coupling relationship between the fluid model of the environment in which the cultural relic is located and the solid thermal model of the cultural relic is established as follows:

[0086] A bidirectional data transmission channel is established between the fluid model of the environment in which the cultural relics are located and the solid thermal model of the cultural relics, so as to transmit the n convective heat transfer coefficients on the fluid-solid interface, the n solar radiation amounts on the fluid-solid interface and the n air temperatures of a thin layer on the surface of the cultural relics calculated by the fluid analysis module at each step to the cultural relics solid thermal analysis module, and to transmit the n initial surface temperatures of the cultural relics set in the cultural relics solid thermal analysis module and the n surface temperatures of the cultural relics calculated at each step to the fluid analysis module.

[0087] Since air flow will affect the surface temperature of cultural relics, the fluid analysis module of the environment where the cultural relics are located needs to take the surface temperature distribution of cultural relics as its condition when solving the Navier Stokes partial differential equations; at the same time, since the continuous heat transfer to the inside of the cultural relics will also affect the surface temperature of the cultural relics, the cultural relics solid thermal analysis module needs to take the convective heat transfer on the surface of the cultural relics caused by the external air flow (represented by air temperature / convective heat transfer coefficient) and the heat transferred to the cultural relics by solar radiation as its conditions when solving the heat conduction partial differential equations. Therefore, it is necessary to establish a two-way coupling relationship between the fluid model of the environment where the cultural relics are located and the solid thermal model of the cultural relics.

[0088] The air temperature transmitted from the fluid analysis module to the cultural relic solid thermal analysis module is the air temperature of a thin layer on the surface of the cultural relic, which is different from the surface temperature of the cultural relic. This temperature difference causes heat transfer from the surface of the cultural relic to the air (if there is no temperature difference, there will be no heat transfer). At the same time, the rate of heat transfer is also related to the air flow close to the solid surface. This rate is expressed by the convection heat transfer coefficient, and the heat transferred from the solar radiation to the cultural relic on the surface of the cultural relic is expressed by the amount of solar radiation. With these parameters, the heat conduction partial differential equation inside the cultural relic solid thermal analysis module has sufficient conditions to be solved, and the surface temperature distribution and the internal temperature distribution of the cultural relic are calculated.

[0089] In some embodiments, the one-way coupling relationship between the fluid model of the environment in which the cultural relic is located and the solid structure model of the cultural relic is established as follows:

[0090] A one-way data transmission channel is established between the fluid model of the environment in which the cultural relic is located and the solid structure model of the cultural relic, so as to transmit the n cultural relic surface pressures (i.e., the pressure values ​​of n surface grid measurement points on the cultural relic surface) calculated by the fluid analysis module at each step to the cultural relic solid structure analysis module. The n cultural relic surface pressures reflect the pressure distribution on the cultural relic surface.

[0091] Since the surface pressure of cultural relics will affect the internal stress of cultural relics, the cultural relics solid structure analysis module needs to take the surface pressure distribution of cultural relics as its condition when solving the Navier equation. Therefore, it is necessary to establish a one-way coupling relationship between the fluid model of the environment in which the cultural relics are located and the solid structure model of the cultural relics.

[0092] In some embodiments, the one-way coupling relationship between the solid thermal model of the cultural relic and the solid structural model of the cultural relic is established as follows:

[0093] A one-way data transmission channel between the solid thermal model of cultural relics and the solid structural model of cultural relics is established to transmit the m internal temperatures of cultural relics calculated by the solid thermal analysis module of cultural relics to the solid structural analysis module of cultural relics at each step. The m internal temperatures of cultural relics reflect the temperature distribution inside the cultural relics.

[0094] Since the internal temperature of cultural relics will affect the internal stress of cultural relics, the cultural relics solid structure analysis module needs to take the internal temperature distribution of cultural relics as its condition when solving the Navier equation. Therefore, it is necessary to establish a one-way coupling relationship between the cultural relics solid thermal model and the cultural relics solid structure model.

[0095] Step 4: Perform fluid-heat-solid coupling calculation to obtain the internal stress distribution of the cultural relics at each time step.

[0096] In some embodiments, the fluid-thermal-solid coupling calculation is implemented in Ansys software. Figure 3 )include:

[0097] The first step is to set the total calculation time, the step size of each time step (that is, the time interval between two adjacent time points) and the number of iterations.

[0098] In the second step, the fluid analysis module calculates the air velocity, air flow direction, air temperature, air pressure and h at each grid point in the air flow area in the first time step. air_1 ,q rad_1 、T air_1 , P surf_1 .

[0099] Specifically, in the first time step, the fluid analysis module substitutes the boundary conditions related to fluid analysis (i.e., air flow velocity, air flow direction, inflow air temperature, air pressure, return air temperature, solar radiation intensity and solar radiation direction), air physical parameters (i.e., air density, air thermal expansion coefficient, air viscosity and air specific heat), initial conditions (i.e., air initial pressure, air initial temperature, air initial flow velocity and air initial flow direction) and n initial temperatures of the surface of cultural relics (transmitted from the cultural relics solid thermal analysis module) into the Navier-Stokes partial differential equations, and solves the air flow velocity, air flow direction, air temperature, air pressure of each grid point in the air flow area of ​​the environment where the cultural relics are located in the first time step and the n convective heat transfer coefficients h on the fluid-solid interface in the first time step. air_1 , n solar radiation q on the fluid-solid interface in the first time step rad_1 And the n air temperatures T of a thin layer on the surface of the artifact in the first time step air_1 , the surface pressure P of n cultural relics in the first time step surf_1 .

[0100] Step 3: The solid thermal analysis module of the cultural relic calculates T in the first time step sol-surf_1 and T sol-body_1 .

[0101] Specifically, in the first time step, the solid thermal analysis module of cultural relics will calculate the cultural relics physical parameters related to thermal analysis (i.e., the density of cultural relics, the thermal conductivity of cultural relics, the specific heat of cultural relics and the thermal expansion coefficient of cultural relics), n initial surface temperatures of cultural relics, m initial internal temperatures of cultural relics, n convection heat transfer coefficients h air_1 , n solar radiation q rad_1 and n air temperatures T air_1 (transferred by the fluid analysis module), substituted into the partial differential equation of heat conduction, and solved to obtain the surface temperature T of n cultural relics in the first time step sol-surf_1 and the internal temperature T of m artifacts in the first time step sol-body_1 .

[0102] Step 4: The cultural relic solid structure analysis module calculates P in the first time step body_1 .

[0103] Specifically, in the first time step, the solid structure analysis module of the cultural relic will calculate the physical parameters of the cultural relic related to the structural analysis (i.e., the Young's modulus and Poisson's ratio of the cultural relic), the surface pressure P of n cultural relics in the first time step, and the surf_1 (transferred by the fluid analysis module) and the internal temperature T of the m artifacts in the first time step sol-body_1 (transferred from the cultural relic solid thermal analysis module), substituted into the Navier equation, and solved to obtain the internal stress P of m cultural relics in the first time step body_1 The internal stress of m cultural relics reflects the internal stress distribution of cultural relics, which is the final manifestation of the thermal-mechanical effect of cultural relics.

[0104] Step 5: The fluid analysis module calculates the air velocity, air flow direction, air temperature, air pressure and h at each grid point in the air flow area in the i-th time step. air_i ,q rad_i 、T air_i , P surf_i .

[0105] Specifically, in the i-th time step, the fluid analysis module will calculate the boundary conditions and air physical parameters related to fluid analysis, as well as the air velocity, air flow direction, air temperature, air pressure of each grid point in the air flow area in the i-1th time step, and the surface temperature T of n cultural relics in the i-1th time step. sol-surf_i-1 (transferred by the cultural relics solid thermal analysis module), substituted into the Navier-Stokes partial differential equations, and solved to obtain the air velocity, air flow direction, air temperature, air pressure of each grid point in the air flow area in the i-th time step and the n convective heat transfer coefficients h on the fluid-solid interface in the i-th time step air_i , n solar radiation q on the fluid-solid interface in the i-th time steprad_i And the n air temperatures T of a thin layer on the surface of the artifact in the i-th time step air_i , the surface pressure P of n cultural relics in the i-th time step surf_i ; Wherein, i takes all integers from 2 to j in turn, j represents the total number of steps, j is an integer and j = total duration ÷ step length.

[0106] Step 6: The cultural relic solid thermal analysis module calculates T in the i-th time step sol-surf_i and T sol-body_i .

[0107] Specifically, in the i-th time step, the cultural relic solid thermal analysis module will convert the cultural relic physical property parameters related to thermal analysis and the surface temperature T of n cultural relics in the i-1th time step into sol-surf_i-1 , the internal temperature T of m cultural relics in the i-1th time step sol-body_i-1 , n convection heat transfer coefficients h air_i , n solar radiation q rad_i and n air temperatures T air_i (transferred by the fluid analysis module), substituted into the partial differential equation of heat conduction, and solved to obtain the surface temperature T of n cultural relics in the i-th time step sol-surf_i and the internal temperature T of m artifacts in the i-th time step sol-body_i .

[0108] Step 7: The cultural relic solid structure analysis module calculates P in the i-th time step body_i .

[0109] Specifically, in the i-th time step, the cultural relic solid structure analysis module will be related to the structure analysis of the cultural relic physical parameters, the surface pressure P of n cultural relics in the i-th time step surf_i (transferred by the fluid analysis module) and the internal temperature T of the m artifacts in the i-th time step sol-body_i (transferred from the cultural relic solid thermal analysis module), substituted into the Navier equation, and solved to obtain the internal stress P of m cultural relics in the i-th time step body_i The internal stress of m cultural relics reflects the internal stress distribution of cultural relics, which is the final manifestation of the thermal-mechanical effect of cultural relics.

[0110] A typical summer environmental condition is used as part of the boundary conditions in the fluid analysis module (see Table 1), the wind speed is the air flow speed, and the wind direction is the air flow direction.

[0111] Table 1

[0112] <![CDATA[Solar radiation intensity (W / m 2 )]]> Temperature (℃) Wind speed (m / s) Direction of solar radiation wind direction Total duration (hours) 800 35 5 -Z -X 8

[0113] The flow-heat-solid coupling calculation is performed and the following is obtained: Figures 5 to 8The shown results are the temperature distribution results of the air flow area of ​​the environment where the cultural relics are located, the pressure distribution results on the surface of the cultural relics, the temperature distribution results inside the cultural relics, and the (internal) stress distribution results of the cultural relics.

[0114] By performing simulation analysis under different wind speeds, we can obtain the maximum temperature and stress results inside the cultural relics under different wind speed conditions as shown in Table 2.

[0115] Table 2

[0116] Wind speed (m / s) Maximum temperature inside the cultural relic (℃) Maximum principal stress inside the cultural relic (Pa) 0 94.75 <![CDATA[3.7432e 7 ]]> 5 73.87 <![CDATA[2.4540e 7 ]]> 10 65.23 <![CDATA[2.1126e 7 ]]>

[0117] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for simulating and analyzing internal stress of cultural relics, characterized in that: include: Step 1, obtaining the solid area of ​​the cultural relics and the air flow area of ​​the environment where the cultural relics are located; Step 2: Based on the air flow area and the solid area of ​​the cultural relics, a fluid model, a solid thermal model and a solid structural model of the cultural relics are established. Step 3: establishing a bidirectional coupling relationship between the fluid model and the solid thermal model of the cultural relic, establishing a unidirectional coupling relationship between the fluid model and the solid structural model of the cultural relic, and establishing a unidirectional coupling relationship between the solid thermal model of the cultural relic and the solid structural model of the cultural relic; Step 4: Perform fluid-heat-solid coupling calculation to obtain the internal stress distribution of the cultural relic in each time step; The steps to build a fluid model of the environment in which the cultural relics are located include: S11, dividing the air flow area of ​​the environment where the cultural relics are located into a plurality of volume grids to obtain air volume grids; S12, importing the air body grid into the fluid analysis module, and setting boundary conditions, initial conditions and air physical property parameters related to the fluid analysis therein; The boundary conditions related to fluid analysis include: air flow velocity, air flow direction, inflow air temperature, air pressure, return air temperature, solar radiation intensity and solar radiation direction; The method for setting boundary conditions related to fluid analysis is: Setting the air flow velocity, air flow direction and temperature of the inflowing air on the Z+ boundary surface of the air flow area; Setting the air pressure and the temperature of the return air on the Z-boundary surface of the air flow area; The contact surface between air and the solid cultural relic is set as the fluid-solid interface, and the solar radiation intensity and solar radiation direction are set on the fluid-solid interface; The initial conditions include initial air pressure, initial air temperature, initial air flow velocity and initial air flow direction; The air physical property parameters include air density, air thermal expansion coefficient, air viscosity and air specific heat; The steps to establish a solid thermal model of cultural relics include: S21, dividing the solid area of ​​the cultural relic into m individual grids to obtain a cultural relic object grid; S22, importing the cultural relic body grid into the cultural relic solid thermal analysis module, and setting the cultural relic physical property parameters related to thermal analysis, n cultural relic surface initial temperatures, and m cultural relic internal initial temperatures therein; wherein the cultural relic physical property parameters related to thermal analysis include the density of the cultural relic, the thermal conductivity of the cultural relic, the specific heat of the cultural relic, and the thermal expansion coefficient of the cultural relic; The steps to establish the solid structure model of cultural relics include: S31, dividing the solid area of ​​the cultural relic into m individual grids to obtain a cultural relic object grid; S32, importing the cultural relic body grid into the cultural relic solid structure analysis module, and setting the cultural relic physical property parameters related to the structural analysis therein; wherein the cultural relic physical property parameters related to the structural analysis include the Young's modulus and the Poisson's ratio of the cultural relic; S33, setting the part where the bottom of the cultural relic is connected to the ground as a fixed constraint in the structural analysis; The method of establishing the bidirectional coupling relationship between the fluid model and the solid thermal model of the cultural relic in step 3 is: A bidirectional data transmission channel between the fluid model and the solid thermal model of the cultural relic is established, so as to transmit the n convective heat transfer coefficients on the fluid-solid interface, the n solar radiation on the fluid-solid interface and the n air temperatures of a thin layer on the surface of the cultural relic calculated by the fluid analysis module at each step to the cultural relic solid thermal analysis module, and to transmit the n initial surface temperatures of the cultural relic set in the solid thermal analysis module and the n surface temperatures of the cultural relic calculated at each step to the fluid analysis module; The method of establishing the one-way coupling relationship between the fluid model and the solid structure model of the cultural relic in step 3 is: Establishing a one-way data transmission channel between the fluid model and the cultural relic solid structure model to transmit the n cultural relic surface pressures calculated by the fluid analysis module at each step to the cultural relic solid structure analysis module; The method of establishing the one-way coupling relationship between the solid thermal model of the cultural relic and the solid structural model of the cultural relic in step 3 is: A one-way data transmission channel between the solid thermal model of the cultural relic and the solid structural model of the cultural relic is established to transmit the internal temperatures of the m cultural relics calculated by the solid thermal analysis module at each step to the solid structural analysis module of the cultural relic; The steps of performing fluid-thermal-solid coupling calculation and obtaining the internal stress distribution of the cultural relic at each time step include: S41, setting the total calculation time, the step size of each time step and the number of iterations; S42. In the first time step, the fluid analysis module substitutes the boundary conditions, air physical parameters, initial conditions and initial temperatures of n cultural relics surfaces related to fluid analysis into the Navier-Stokes partial differential equations, and solves the air velocity, air flow direction, air temperature, air pressure and n convective heat transfer coefficients h at each grid point in the air flow area in the first time step. air_1 , n solar radiation q rad_1 And the n air temperatures T of a thin layer on the surface of the artifact in the first time step air_1 、n cultural relics surface pressure P surf_1 ; S43. In the first time step, the cultural relic solid thermal analysis module calculates the cultural relic physical property parameters related to thermal analysis, n cultural relic surface initial temperatures, m cultural relic internal initial temperatures, n convection heat transfer coefficients h air_1 , n solar radiation q rad_1 and n air temperatures T air_1 , substitute into the partial differential equation of heat conduction, and solve to obtain the surface temperature T of n cultural relics in the first time step sol-surf_1 and the internal temperature of m artifacts T sol-body_1 ; S44. In the first time step, the cultural relic solid structure analysis module calculates the cultural relic physical property parameters related to the structural analysis, the surface pressure P of n cultural relics, and the surf_1 and the internal temperature of m artifacts T sol-body_1 , substituted into the Navier equation, and the internal stress P of m cultural relics in the first time step is obtained. body_1 ; S45. In the i-th time step, the fluid analysis module calculates the boundary conditions related to the fluid analysis, the air physical parameters, the air velocity, air flow direction, air temperature, air pressure of each grid point in the air flow area in the i-1th time step, and the surface temperature T of n cultural relics in the i-1th time step. sol-surf_i-1 , substituting into the Navier-Stokes partial differential equations, the air velocity, air flow direction, air temperature, air pressure of each grid point in the air flow area in the i-th time step and the n convective heat transfer coefficients h on the fluid-solid interface in the i-th time step are obtained. air_i , n solar radiation q rad_i And the n air temperatures T of a thin layer on the surface of the artifact in the i-th time step air_i 、n cultural relics surface pressure P surf_i ; Where i is all integers from 2 to j, j represents the total number of steps, j is an integer and j=total duration ÷ step length; S46. In the i-th time step, the cultural relic solid thermal analysis module calculates the cultural relic physical property parameters related to thermal analysis and the surface temperatures T of n cultural relics. sol-surf_i-1 , the internal temperature T of m cultural relics in the i-1th time step sol-body_i-1 , n convection heat transfer coefficients h air_i , n solar radiation q rad_i and n air temperatures T air_i , substitute into the partial differential equation of heat conduction, and solve to obtain the surface temperature T of n cultural relics in the i-th time step sol-surf_i and the internal temperature of m artifacts T sol-body_i ; S47, in the i-th time step, the cultural relic solid structure analysis module will be related to the structure analysis of the cultural relic physical parameters, n cultural relic surface pressure P surf_i and the internal temperature of m artifacts T sol-body_i , substituted into the Navier equation, and the internal stress P of m cultural relics in the i-th time step is obtained. body_i .

2. The method for simulating and analyzing internal stress of cultural relics according to claim 1, characterized in that: The step of obtaining the solid area of ​​the cultural relic and the air flow area of ​​the environment where the cultural relic is located in step 1 comprises: P1. Perform 3D scanning on cultural relics to obtain point cloud data on the surface of cultural relics; P2. Converting the point cloud data into a surface mesh of the cultural relic surface in finite element pre-processing software; P3. Create a rectangular area in the fluid simulation software, import the surface grid, set the area within the surface grid as the solid area of ​​the cultural relic, subtract the solid area of ​​the cultural relic from the rectangular area, and obtain the air flow area of ​​the environment where the cultural relic is located.

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