A method for analyzing composite laser damage
By establishing a coating-substrate system model and employing sequential coupling analysis and multiple damage simulation models, the problems of insufficient simulation accuracy and single damage mode in existing technologies were solved, achieving efficient and accurate simulation of composite laser damage and revealing the thermo-mechanical synergistic damage mechanism.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHANGCHUN INST OF OPTICS FINE MECHANICS & PHYSICS CHINESE ACAD OF SCI
- Filing Date
- 2026-02-11
- Publication Date
- 2026-06-19
AI Technical Summary
Existing technologies, when simulating the damage of composite lasers to ZrB2-SiC coatings on C/C substrates, fail to fully consider the interfacial thermal resistance, nonlinear changes in material parameters, and thermal mismatch of the coating-substrate composite structure. This results in insufficient simulation accuracy and a single damage mode, failing to integrate simulations of multiple failure mechanisms such as brittle fracture and interfacial delamination.
An analytical model including the substrate, ceramic coating, and interface layer was established. A sequential coupling analysis method was adopted. First, thermal analysis was performed to simulate the thermal effect of continuous laser, and then mechanical analysis was performed to simulate the mechanical effect and damage evolution of pulsed laser. The Johnson-Holmquist second model, cohesive force model, and element deletion criterion were combined to simulate the bulk damage, interface delamination, and ablation process of the ceramic coating.
It significantly improves the accuracy of temperature field and thermal stress field calculations, can clearly reproduce multiple failure modes of coatings under composite laser action, reveals the essential mechanism of thermo-mechanical synergistic damage, and realizes efficient and stable simulation of multi-pulse, long-time laser damage processes.
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Figure CN122241973A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of numerical simulation technology of laser-material interaction, and more specifically, to an analytical method for composite laser damage. Background Technology
[0002] With the development of high-energy laser technology, especially composite laser technology (a combination of continuous and pulsed lasers), it has important applications in fields such as optoelectronic countermeasures and materials processing in advanced aerospace equipment. Carbon / carbon (C / C) composite materials are used as thermal structural components due to their excellent high-temperature properties; however, they are easily oxidized in high-temperature oxygen environments, and ultra-high-temperature ceramic coatings such as ZrB2-SiC are usually prepared on their surfaces for protection. Evaluating the laser damage resistance of such coating materials and understanding their failure mechanisms under the action of high-energy composite lasers is crucial for the survivability of equipment.
[0003] Given the high cost of experimental research and the difficulty in capturing transient physical details, numerical simulation has become an important tool for studying the interaction between lasers and materials. Currently, there are several numerical simulation studies on laser ablation or damage. For example, the Chinese patent application "Numerical Simulation Method for Composite Laser Ablation" discloses a scheme that includes: establishing a basic numerical simulation model of the interaction between continuous laser and matter using finite element software; treating the change in the material's absorptivity to continuous laser caused by defects created by ultrafast laser ablation as equivalent to nonlinear absorption; constructing a pressure calculation model of ultrafast laser-excited plasma shock wave using spectral detection combined with Sedov-Taylor theory, and incorporating this pressure as a volume integral into the continuous laser model, thereby establishing a numerical model of the composite laser ablation process. This scheme provides a solution to the coupling problem caused by the large time scale difference and different physical processes between continuous lasers and ultrafast lasers, namely, approximating the effect of composite lasers by using the equivalent absorption coefficient change and the externally applied shock wave pressure.
[0004] The existing technical solutions have three main limitations: First, the models are highly general but lack specificity, failing to fully consider the key effects unique to coating-substrate composite structures, such as interfacial thermal resistance, nonlinear changes in material parameters, and thermal mismatch, resulting in insufficient simulation accuracy for specific material systems such as C / C substrate ZrB2-SiC coatings. Second, the shock wave models rely on external spectral detection experimental data and are subjected to theoretical inversion calculations, which not only increases cost and complexity but also makes it difficult for models based on constrained / semi-constrained conditions to accurately describe the spatiotemporal distribution of shock waves under unconstrained atmospheric conditions. Third, the damage modes are singular, focusing only on molten pool changes and ablation behavior, failing to integrate simulations of various competing failure mechanisms of ultra-high temperature ceramic coatings under laser thermo-mechanical coupling, such as brittle fracture and interfacial delamination.
[0005] Therefore, an analytical method for composite laser damage is needed to solve one of the aforementioned technical problems. Summary of the Invention
[0006] The purpose of this application is to provide an analytical method for composite laser damage, which can solve at least one of the technical problems mentioned above. The specific solution is as follows: According to a specific embodiment of this application, this application provides a method for analyzing composite laser damage, comprising: Establish an analytical model that includes the substrate, ceramic coating, and interface layer; A sequential coupling analysis method is adopted, first performing thermal analysis to simulate the thermal effects of continuous laser, and then performing mechanical analysis to simulate the mechanical effects and damage evolution of pulsed laser; The mechanical analysis includes the following concurrent damage simulation process: The Johnson-Holmquist second model was used to simulate the bulk damage evolution process of the ceramic coating; An internal cohesion model was used to simulate the interfacial delamination process between the ceramic coating and the substrate; The ablation removal process of the ceramic coating was simulated using a cell deletion criterion.
[0007] Furthermore, the sequential coupling analysis method includes: In the thermal analysis, the temperature field history is calculated based on a continuous laser heat source; The temperature field history is used as a predefined field and imported into the mechanical analysis to be equivalent to the thermal stress and material thermal softening state generated by continuous laser preheating. Based on the thermal stress and the thermal softening state of the material, a pulsed laser-induced shock wave pressure load based on the laser-supported detonation theory is applied.
[0008] Furthermore, in the thermal analysis, the temperature field history is calculated based on a continuous laser heat source, including: The governing equations for transient heat conduction are established based on Fourier's law of heat conduction. A continuous laser heat source with spatial distribution is applied to the surface of the ceramic coating to obtain spatial distribution parameters; An interfacial thermal resistance boundary condition is introduced at the interface between the ceramic coating and the substrate to obtain the interfacial thermal resistance parameters. Based on the spatial distribution parameters and interface thermal resistance parameters, the governing equations are solved to obtain the temperature field history.
[0009] Furthermore, the governing equations for transient heat conduction based on Fourier's law of heat conduction include: The thermal conductivity and specific heat capacity of the ceramic coating are defined as a first function of temperature. The thermal conductivity and specific heat capacity of the substrate material are defined as a second function of temperature. Based on the first function and the second function, the governing equations that incorporate the nonlinear thermophysical properties of the material are constructed.
[0010] Furthermore, the application of the pulsed laser-induced shock wave pressure load based on the laser-supported detonation theory includes: Construct a spatiotemporal distribution model of shock wave pressure suitable for unconstrained atmospheric environments; Based on the aforementioned shock wave pressure spatiotemporal distribution model, the evolution load values of shock wave pressure with space and time are obtained. The evolved load value is applied as a surface pressure load to the laser-irradiated surface of the ceramic coating.
[0011] Furthermore, the process of applying the shock wave pressure load is a multi-pulse cyclic analysis, including: In the mechanical analysis, the application of the shock wave pressure load is performed periodically and repeatedly; During the interval between two consecutive load applications, the stress, strain, and damage state variables of the analysis model are updated until all pulses have been applied.
[0012] Furthermore, the cohesive force model used to simulate the interface delamination process includes: Zero-thickness cohesive elements are set in the analysis model; The simulation of interface stratification is achieved through the zero-thickness cohesive unit.
[0013] Furthermore, the process of simulating ablation removal using the cell deletion criterion includes: Set the criteria parameters for triggering the deletion of the unit; The deletion of the unit is triggered according to the criterion parameters to simulate ablation removal; The criteria parameters include: ablation temperature threshold and damage variable critical value.
[0014] Furthermore, the conditions under which the criterion parameter triggers the deletion of the unit include: When the temperature of the material unit of the ceramic coating exceeds the ablation temperature threshold; The deletion of the unit is triggered when the damage variable calculated by the Johnson-Holmquist second model reaches the critical value of the damage variable.
[0015] Furthermore, the establishment of the analytical model, which includes the substrate, ceramic coating, and interface layer, includes: Define the anisotropic thermal conductivity tensor parameters of the substrate; Define the Johnson-Holmquist second model parameters for the ceramic coating; Define the parameters of the bilinear traction-separation law for the interface layer; A three-dimensional finite element model is established based on the parameters, and the mesh of the central region of the laser spot and the interface layer is refined to complete the analysis model.
[0016] Compared with the prior art, the above-described solutions of this application have at least the following beneficial effects: 1. This application provides an analysis method for composite laser damage. By establishing a model for the coating-substrate system and strictly considering the temperature nonlinearity of interface thermal resistance and material thermal properties, the accuracy of temperature field and thermal stress field calculations is significantly improved, and the method can better reflect the real physical process.
[0017] 2. This application provides an analytical method for composite laser damage. By integrating the Johnson-Holmquist second model to simulate bulk damage, the cohesive model to simulate interface delamination, and the element deletion criterion to simulate surface ablation, it achieves concurrent simulation of all three main failure modes of ultra-high temperature ceramic coatings under composite laser irradiation within a single framework. It can clearly reproduce the complete dynamic competitive failure process from thermal stress accumulation to shock wave loading, ultimately leading to simultaneous internal cracking, interface delamination, and surface ablation of the coating, thus systematically and deeply revealing the essential mechanism of composite laser thermo-mechanical synergistic damage.
[0018] 3. This application provides an analysis method for composite laser damage. The sequentially coupled dual-timescale analysis strategy employs implicit thermal analysis followed by explicit dynamic analysis, effectively avoiding the computational difficulties caused by directly coupling second-level and nanosecond-level physical processes. This achieves efficient and stable calculation for such complex multiphysics problems with huge timescale differences, making it possible to perform engineering simulation analysis of multi-pulse, long-term laser damage processes. Attached Figure Description
[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings: Figure 1 This is a flowchart of the first method for analyzing composite laser damage, as shown in an embodiment of this application.
[0020] Figure 2 This is a second method flowchart illustrating an analysis method for composite laser damage according to an embodiment of this application.
[0021] Figure 3This is a schematic diagram illustrating the theoretical characterization of the impact pressure on the surface of a pulsed laser-induced plasma target, as shown in an embodiment of this application. Detailed Implementation
[0022] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0023] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the application. The singular forms "a," "the," and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, and "multiple" generally includes at least two unless the context clearly indicates otherwise.
[0024] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.
[0025] It should be understood that although the terms first, second, third, etc., may be used in the embodiments of this application, these descriptions should not be limited to these terms. These terms are only used to distinguish the descriptions. For example, first may also be referred to as second without departing from the scope of the embodiments of this application, and similarly, second may also be referred to as first.
[0026] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the product or device that includes that element.
[0027] The optional embodiments of this application are described in detail below with reference to the accompanying drawings.
[0028] like Figure 1 and Figure 2 As shown, a method for analyzing composite laser damage includes: S1. Establish an analytical model including the substrate, ceramic coating, and interface layer. In this embodiment, the substrate is a carbon / carbon (C / C) composite material with dimensions of 50mm × 50mm × 5mm. A 200μm thick ZrB2-SiC ceramic coating is constructed on the upper surface of the substrate. Between the ceramic coating and the substrate, a zero-thickness cohesive unit, such as CoH3D8 in ABAQUS, is defined as the interface layer. In this embodiment, the laser parameters are: energy 1.8J, pulse width 8ns, and laser spot diameter 3mm.
[0029] In this embodiment, ABAQUS is a finite element simulation software, where VDLOAD, VUSDFLD, and VUMAT are all user subroutines in ABAQUS used to simulate complex load application and material response.
[0030] VDLOAD: Load pulse pressure, used to define a distributed load that varies with time and space. Based on pressure load theory, in dynamic analysis, the shock wave pressure induced by a pulsed laser is used. P (r,t) is a dynamic surface load that is precisely applied to the coating surface. It implements the load definition for multi-pulse cyclic loading.
[0031] VUSDFLD: Birth and Death Element, used to update or define user-defined state variables during analysis, such as damage variables and temperature threshold markers, and to perform specific operations such as element deletion based on these variables. In this embodiment, the element deletion criteria are implemented. In each analysis increment step, this subroutine iterates through all elements and determines whether one of two deletion conditions is met: 1) the element temperature exceeds a preset ablation threshold (T≥T_ablation); 2) the JH-2 damage variable calculated by VUMAT reaches a critical value (D≥1). When the conditions are met, it marks the element as "failed," and the main program then multiplies its stiffness matrix by a minimum value and removes it, thereby simulating the ablation removal or complete fracture of the material.
[0032] VUMAT: Used to define the constitutive relationship (stress-strain relationship) of materials, including complex mechanical behaviors such as elastoplasticity, damage, and failure. In this embodiment, the Johnson-Holmquist II (JH-2) model is used to implement the material damage constitutive model. This subroutine encodes the strength equation, state equation, and damage accumulation method of the JH-2 model to simulate the dynamic mechanical response, plastic deformation, and damage evolution process of the ZrB2-SiC coating under high temperature, high strain rate, and high pressure. This embodiment provides a preferred scheme for establishing an analytical model including a substrate, a ceramic coating, and an interface layer, including: Define the anisotropic thermal conductivity tensor parameters of the substrate.
[0033] The matrix parameters of the C / C composite material are: density of 1.80 g / cm³, anisotropic thermal conductivity defined in tensor form, and mechanical behavior described by an anisotropic elastic model, using defined engineering constants. E 1 = 80 GPa, E 2 = 50 GPa, E 3 = 20 GPa, Nu 12 =0.25, Nu 13 =0.15, Nu 23 =0.15, G 12 =15 GPa, G 13 =8 GPa, G 23 =8 GPa to construct the stiffness matrix.
[0034] Define the JH-2 model parameters for the ceramic coating. The ceramic coating material parameters are: density 5.60 g / cm³. Its thermophysical parameters are defined as functions of temperature, with specific values obtained from the COMSOL material library or authoritative literature in discrete point table format and then input. Its dynamic mechanical response is described using the Johnson-Holmquist second model, implemented through the user subroutine VUMAT.
[0035] Define the parameters of the bilinear traction-separation law for the interface layer. The mechanical behavior of the interface layer material is simulated using zero-thickness cohesive elements combined with the bilinear traction-separation law to obtain the normal strength, tangential strength, and mixing mode parameters in the BK criterion.
[0036] A three-dimensional finite element model was established based on the parameters, and the mesh was refined in the central region of the laser spot and the interface layer. Within the central diameter region of the laser spot and in the coating and interface layer of a preset thickness, dense hexahedral elements of a preset size were used for mesh refinement; towards the outer region, the mesh size gradually transitioned to a sparse mesh. The analysis model was then completed.
[0037] S2. A sequential coupling analysis method is adopted. First, thermal analysis is performed to simulate the thermal effect of continuous laser, and then mechanical analysis is performed to simulate the mechanical effect and damage evolution of pulsed laser.
[0038] The sequential coupling analysis method consists of two core analysis steps: thermal analysis and mechanical analysis. By establishing a model specifically for the coating-substrate system and rigorously considering the temperature nonlinearity of interfacial thermal resistance and material thermal properties, the accuracy of temperature and thermal stress field calculations is significantly improved, better reflecting the real physical processes.
[0039] In this embodiment, the preheating process of a continuous laser is simulated through transient heat conduction analysis. This stage calculates the system's temperature field history based on the continuous laser heat source. The temperature field is obtained by implicitly solving for heat conduction using the user subroutine DFLUX, enabling the loading of the continuous laser heat source and performing transient heat conduction analysis. This process rigorously considers the interfacial thermal resistance between the ceramic coating and the substrate, as well as the nonlinear changes in the material's thermal properties with temperature, to calculate the historical temperature field under the combined laser action.
[0040] In the technical solution of this application embodiment, performing transient heat conduction analysis to calculate the temperature field history specifically includes: S201. Based on Fourier's law of heat conduction, establish the governing equations for transient heat conduction. The expression for the governing equations is: in, ρ Indicates the density of the material; C p denoted by Specific heat capacity; k represents the thermal conductivity tensor; Indicates the heat source; and These represent the surface thermal radiation and convection terms, respectively. This indicates the exothermic oxidation term; T represents temperature.
[0041] In the technical solution of the embodiments of this application, The expression for the heat source is: Where R represents the surface reflectivity of the target material; Indicates the material absorption coefficient; Indicates laser intensity; Indicates distance in the positive direction.
[0042] S202. Apply a continuous laser heat source with spatial distribution to the surface of the ceramic coating and obtain the spatial distribution parameters.
[0043] On the surface of the ceramic coating, a continuous laser heat source is applied, and its spatial distribution parameters are obtained. Specifically, the spatial distribution parameters include: the laser energy exhibits a Gaussian distribution, and the spot diameter is [value missing].
[0044] The thermal conductivity and specific heat capacity of the ceramic coating are defined as a first function of temperature. Discrete data points of ZrB2-SiC coating as a function of temperature are obtained from the COMSOL material library or literature to establish the first functional relationship. In the material properties module of the finite element software, the temperature correlation option for thermal conductivity and specific heat capacity is selected, and typical discrete data are input.
[0045] The thermal conductivity and specific heat capacity of the substrate material are defined as a second function of temperature. Based on the requirement of material nonlinearity, temperature-related data of the thermal properties of the C / C composite substrate are input to form a second function relationship.
[0046] S203. Introduce interfacial thermal resistance boundary conditions at the interface between the ceramic coating and the substrate, and obtain the interfacial thermal resistance parameters.
[0047] In finite element software, based on the first and second functions, the temperature-related parameters defined above are assigned to the corresponding terms in the governing equations. The first function is assigned to the governing equation parameters of the coating region, and the second function is assigned to the governing equation parameters of the substrate region, thereby constructing a governing equation that incorporates the nonlinear thermophysical properties of the material, forming a nonlinear system that considers the changes in material properties with temperature.
[0048] At the interface between the coated ceramic and the substrate, i.e., at z=hi, a thermal resistance boundary condition is introduced. The expression for the thermal resistance boundary condition is: Where Ri represents the interfacial thermal resistance; Tc and Ts represent the temperatures of the ceramic coating and the substrate, respectively; kc and ks represent the thermal conductivity of the ceramic coating and the substrate, respectively; and hi represents the location of the interfacial interface. Indicates the area above the interlayer interface; This indicates the area below the interlayer interface.
[0049] S204. Solve the governing equations based on the spatial distribution parameters and interface thermal resistance parameters to obtain the temperature field history.
[0050] In the technical solution of this application embodiment, explicit dynamic mechanical analysis performs the following concurrent damage simulation process to simulate pulsed laser shock and the resulting dynamic mechanical response and damage evolution, specifically including: The entire time-history temperature field obtained from the transient heat conduction analysis is used as a predefined field and imported into the mesh of the current explicit dynamic mechanical analysis through interpolation to represent the thermal stress and material thermal softening state generated by continuous laser preheating. Based on the thermal stress and material thermal softening state, a pulsed laser-induced shock wave pressure load based on the Laser Supported Detonation (LSD) theory is applied. Specifically, the pulsed laser-induced shock wave pressure P(r,t) is applied as a dynamic load to the ceramic coating surface via a user subroutine (VDLOAD). The technical solution of this application is equivalent to introducing the thermal stress and material thermal softening state generated by continuous laser preheating into the mechanical analysis, providing an accurate initial stress field and material state for subsequent mechanical impact simulation.
[0051] S205. Based on the Laser-Supported Detonation (LSD) theory, a model applicable to the unconstrained atmospheric environment is constructed in the user subroutine VDLOAD to describe the whole process of the shock wave pressure from establishment to decay.
[0052] The expression of the shock wave pressure P(r, t) during the laser action period (0 < t ≤ τ) is: Among them, t represents time; τ represents the duration of the pulsed laser action; I(r, t) represents the laser intensity with Gaussian spatio-temporal distribution; K represents a constant related to the specific heat ratio of air and the ambient density; represents the plasma establishment time constant, which reflects the transient process of pressure establishment.
[0053] The expression of the shock wave pressure P(r, t) after the laser ends (t > τ) is: Among them, n represents the power-law decay exponent; represents the heat dissipation time constant. The expression describes the decay law of the shock wave after no energy replenishment.
[0054] The technical solution of the embodiment of the present application proposes a shock wave pressure model based on the Laser-Supported Detonation (LSD) theory, which is designed specifically for the unconstrained atmospheric environment and does not need to rely on additional complex experiments for calibration. It simplifies the simulation process, reduces costs and complexity, and at the same time describes the shock wave in this application scenario more reliably.
[0055] S206. Based on the spatio-temporal distribution model of the shock wave pressure, obtain the evolution load values of the shock wave pressure with space and time.
[0056] S207. Apply the evolution load value as the surface pressure load to the laser-irradiated surface of the ceramic coating.
[0057] According to the expression of the shock wave pressure P(r, t), the load values of the shock wave pressure with an almost Gaussian distribution in space and a change of first rising and then decaying in time are calculated. Through the VDLOAD subroutine, the calculated spatio-temporal evolution load value is used as the surface pressure load and applied to the upper surface of the ceramic coating, that is, the laser-irradiated area.
[0058] This application provides a preferred technical solution for simulating multi-pulse laser action, where the application of shock wave pressure load is performed through multi-pulse cyclic analysis. In the mechanical analysis, the number of repeating pulses, the pulse period, and the duration of each period are set. The load application is performed periodically and repeatedly. At the beginning of each pulse period, the VDLOAD subroutine is called to apply a shock wave pressure load once. During the interval between two adjacent load applications, i.e., from the end of the load in each period to the start of the next period, the stress, strain, and damage state variables of the entire analysis model are calculated and automatically updated. This cycle repeats automatically until the entire number of pulses has been applied.
[0059] Throughout the mechanical analysis, including the multi-pulse cycle process, three damage models are invoked simultaneously to perform concurrent damage simulations: The Johnson-Holmquist second model was used to simulate the bulk damage evolution of the ceramic coating. This was implemented using the user subroutine VUMAT. The model describes the dynamic response of the ZrB2-SiC coating under high strain rate, high pressure, and high temperature. During the analysis, the damage variable D of the element was calculated in real time, varying from 0 to 1.
[0060] In this embodiment of the application, the Johnson-Holmquist second model includes an intensity model, a state equation, and a damage evolution.
[0061] The normalized equivalent stress of the Johnson-Holmquist second model is expressed as: in, Indicates the normalized complete strength; Indicates normalized fracture strength; D It represents a damage scalar that varies from 0 to 1.
[0062] All normalized stresses can be derived from... Obtained from.
[0063] in, Indicates the current equivalent stress. This represents the equivalent stress at HEL.
[0064] The expression for damage accumulation is: in, Indicates the equivalent plastic fracture strain; This represents the increment of plastic strain; the expression reflects the increment of plastic strain. In equivalent plastic fracture strain Accumulated.
[0065] A cohesive force model is used to simulate the interfacial delamination process between the ceramic coating and the substrate. In the technical solution of this application embodiment, the starting criterion of the cohesive force model is: the energy-based quadratic nominal stress criterion (QUADS) is used to determine when damage begins at the interface under combined stress. It is a stress-based judgment standard, expressed as: in, Indicates the normal traction force of the interface; This indicates the first tangential traction force, parallel to the interface, in the first shear direction; This indicates the second tangential traction force, which is parallel to the interface and perpendicular to the first shear direction. Indicates the normal intensity of the interface; Indicates the first tangential strength; This indicates the second tangential strength.
[0066] Evolution Criterion: The Benzeggagagh-Kenane (BK) energy criterion is adopted to control how damage develops until complete failure of the interface after the onset of damage. It is an energy-based judgment standard. The damage variable increases with the energy release rate of the hybrid mode until the interface completely fails (D=1).
[0067] An element deletion criterion is employed to simulate the ablation removal process of ceramic coatings. Implemented via a VUSDFLD user subroutine, elements are "deleted" when their temperature exceeds their ablation threshold or their mechanical damage reaches a critical value, visually simulating the melting and vaporization removal process. The VUSDFLD user subroutine sets the criteria for triggering element deletion: ablation temperature threshold and critical damage variable value. In each incremental step of the analysis, all ceramic coating elements are examined. Deletion of an element is triggered when either condition is met.
[0068] The technical solution of this application integrates the JH-2 model (bulk damage), the cohesive force model (interface delamination), and the element deletion criterion (surface ablation) to achieve concurrent simulation of all three main failure modes of ultra-high temperature ceramic coatings under composite laser irradiation within a single simulation framework. It can clearly reproduce the complete dynamic competitive failure process from thermal stress accumulation to shock wave loading, ultimately leading to simultaneous internal cracking, interface delamination, and surface ablation of the coating, thus systematically and deeply revealing the essential mechanism of composite laser "thermal-mechanical synergistic" damage.
[0069] This application provides a preferred technical solution where the conditions for unit deletion include: the temperature of the ceramic coating material unit exceeds the ablation temperature threshold, or the damage variable calculated by the Johnson-Holmquist second model reaches the critical value of the damage variable.
[0070] In this embodiment, the spatiotemporal evolution load P(r,t) of the plasma shock wave pressure induced by pulsed laser is applied to the coating surface via the user subroutine VDLOAD. Referring to actual laser parameters—energy 1.8 J, pulse width 8 ns, and laser spot diameter 3 mm—the shock wave pressure is characterized through programming. Figure 3 Figure a shows the time distribution of impact stress, indicating the change of impact stress in the central region (r=0) of the laser irradiation over time. During the pulsed laser action, the pressure first rises to a peak value and then decays, and then decays more rapidly after the laser action ends. Figure 3 Figure b shows the spatial variation of the peak pressure (t=4.2ns), which is almost a Gaussian distribution. Figure 3 Figure c in the middle represents a three-dimensional representation of the spatiotemporal distribution of pressure. Figure 3 The d-plot represents a contour map of the spatiotemporal distribution of pressure. Therefore, it can be seen that the technical solution of this application embodiment completely reproduces the entire dynamic failure process from continuous laser preheating and thermal stress accumulation to pulsed laser shock, ultimately leading to coating cracking, interface peeling, and material ablation, verifying the effectiveness and accuracy of the method of this invention.
[0071] This application provides an analysis method for composite laser damage. By establishing a model for the coating-substrate system and strictly considering the temperature nonlinearity of interface thermal resistance and material thermal properties, the accuracy of temperature field and thermal stress field calculations is significantly improved, and the method can better reflect the real physical process.
[0072] This application provides an analytical method for composite laser damage. By integrating the Johnson-Holmquist second model to simulate bulk damage, the cohesive force model to simulate interface delamination, and the element deletion criterion to simulate surface ablation, it achieves concurrent simulation of all three main failure modes of ultra-high temperature ceramic coatings under composite laser irradiation within a single framework. It can clearly reproduce the complete dynamic competitive failure process from thermal stress accumulation to shock wave loading, ultimately leading to simultaneous internal cracking, interface delamination, and surface ablation of the coating, thus systematically and deeply revealing the essential mechanism of composite laser thermo-mechanical synergistic damage.
[0073] This application provides an analysis method for complex laser damage, which adopts a sequentially coupled dual-timescale analysis strategy. It first performs implicit thermal analysis and then explicit dynamic analysis, effectively avoiding the computational difficulties caused by directly coupling second-level and nanosecond-level physical processes. This enables efficient and stable calculation of such complex multiphysics problems with huge timescale differences, making it possible to perform engineering simulation analysis of multi-pulse, long-term laser damage processes.
[0074] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.
[0075] The units described in the embodiments of this application can be implemented in software or hardware. The names of the units are not, in some cases, limiting the scope of the unit itself.
Claims
1. A method for analyzing composite laser damage, characterized in that, include: Establish an analytical model that includes the substrate, ceramic coating, and interface layer; A sequential coupling analysis method is adopted, first performing thermal analysis to simulate the thermal effects of continuous laser, and then performing mechanical analysis to simulate the mechanical effects and damage evolution of pulsed laser; The mechanical analysis includes the following concurrent damage simulation process: The Johnson-Holmquist second model was used to simulate the bulk damage evolution process of the ceramic coating; An internal cohesion model was used to simulate the interfacial delamination process between the ceramic coating and the substrate; The ablation removal process of the ceramic coating was simulated using a cell deletion criterion.
2. The analytical method according to claim 1, characterized in that, The sequential coupling analysis method includes: In the thermal analysis, the temperature field history is calculated based on a continuous laser heat source; The temperature field history is used as a predefined field and imported into the mechanical analysis to be equivalent to the thermal stress and material thermal softening state generated by continuous laser preheating. Based on the thermal stress and the thermal softening state of the material, a pulsed laser-induced shock wave pressure load based on the laser-supported detonation theory is applied.
3. The analytical method according to claim 2, characterized in that, The thermal analysis, based on the calculation of the temperature field history using a continuous laser heat source, includes: The governing equations for transient heat conduction are established based on Fourier's law of heat conduction. A continuous laser heat source with spatial distribution is applied to the surface of the ceramic coating to obtain spatial distribution parameters; An interfacial thermal resistance boundary condition is introduced at the interface between the ceramic coating and the substrate to obtain the interfacial thermal resistance parameters. Based on the spatial distribution parameters and interface thermal resistance parameters, the governing equations are solved to obtain the temperature field history.
4. The analytical method according to claim 3, characterized in that, The governing equations for transient heat conduction established based on Fourier's law of heat conduction include: The thermal conductivity and specific heat capacity of the ceramic coating are defined as a first function of temperature. The thermal conductivity and specific heat capacity of the substrate material are defined as a second function of temperature. Based on the first function and the second function, the governing equations that incorporate the nonlinear thermophysical properties of the material are constructed.
5. The analytical method according to claim 2, characterized in that, The application of pulsed laser-induced shock wave pressure load based on laser-supported detonation theory includes: Construct a spatiotemporal distribution model of shock wave pressure suitable for unconstrained atmospheric environments; Based on the aforementioned shock wave pressure spatiotemporal distribution model, the evolution load values of shock wave pressure with space and time are obtained. The evolved load value is applied as a surface pressure load to the laser-irradiated surface of the ceramic coating.
6. The analytical method according to claim 5, characterized in that, The process of applying the shock wave pressure load is a multi-pulse cyclic analysis, including: In the mechanical analysis, the application of the shock wave pressure load is performed periodically and repeatedly; During the interval between two consecutive load applications, the stress, strain, and damage state variables of the analysis model are updated until all pulses have been applied.
7. The analytical method according to claim 1, characterized in that, The process of simulating interface delamination using a cohesive force model includes: Zero-thickness cohesive elements are set in the analysis model; The simulation of interface stratification is achieved through the zero-thickness cohesive unit.
8. The analytical method according to claim 1, characterized in that, The process of simulating ablation removal using the unit deletion criterion includes: Set the criteria parameters for triggering the deletion of the unit; The deletion of the unit is triggered according to the criterion parameters to simulate ablation removal; The criteria parameters include: ablation temperature threshold and damage variable critical value.
9. The analytical method according to claim 8, characterized in that, The conditions under which the criterion parameters trigger the deletion of the unit include: When the temperature of the material unit of the ceramic coating exceeds the ablation temperature threshold; The deletion of the unit is triggered when the damage variable calculated by the Johnson-Holmquist second model reaches the critical value of the damage variable.
10. The analytical method according to claim 1, characterized in that, The establishment of the analytical model, which includes the substrate, ceramic coating, and interface layer, includes: Define the anisotropic thermal conductivity tensor parameters of the substrate; Define the Johnson-Holmquist second model parameters for the ceramic coating; Define the parameters of the bilinear traction-separation law for the interface layer; A three-dimensional finite element model is established based on the parameters, and the mesh of the central region of the laser spot and the interface layer is refined to complete the analysis model.