CN113962124A - Laser-induced ultrasonic parameter optimization method and system - Google Patents

Laser-induced ultrasonic parameter optimization method and system Download PDF

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CN113962124A
CN113962124A CN202111221913.2A CN202111221913A CN113962124A CN 113962124 A CN113962124 A CN 113962124A CN 202111221913 A CN202111221913 A CN 202111221913A CN 113962124 A CN113962124 A CN 113962124A
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thermal barrier
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CN113962124B (en
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李兵
黄钰
陈磊
秦峰
张振龙
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Xian Jiaotong University
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Abstract

The invention discloses a laser-induced ultrasonic parameter optimization method and a system, wherein a laser ultrasonic technology is applied to carry out nondestructive testing on a thermal barrier coating material, and a thermal barrier coating geometric model is constructed based on COMSOL; carrying out simulation calculation by utilizing a thermal barrier coating geometric model to obtain the temperature field change and the temperature contour line of the material after the laser acts on the top layer of the thermal barrier coating; and according to the temperature field change and the temperature contour line, combining the temperature ablation threshold of the top layer of the thermal barrier coating to obtain the power density threshold of the correspondingly loaded pulse laser, and calculating to obtain the laser energy threshold of the thermal barrier coating material subjected to ablation so as to realize the parameter optimization of laser-induced ultrasound. The method is simple and easy to realize, can realize laser-induced ultrasonic parameter optimization under the condition of not consuming a large amount of resources, and achieves the purpose of nondestructive testing of the thermal barrier coating material.

Description

Laser-induced ultrasonic parameter optimization method and system
Technical Field
The invention belongs to the technical field of nondestructive testing of thermal barrier coatings, and particularly relates to a laser-induced ultrasonic parameter optimization method and system.
Background
Since the beginning of the research of thermal barrier coatings in the 50 th century, the 60 th century, the U.S. department of defense, and the U.S. national aerospace agency, thermal barrier coating technology has gained rapid development and continued attention in the past few decades. Thermal barrier coatings have been widely used for aircraft engines and hot end parts (high temperature blades, combustors, etc.) of gas turbines at present due to their excellent combination properties of high temperature resistance, low thermal conductivity, corrosion resistance and wear resistance. The thermal barrier coating system has typical multi-component structural characteristics and mainly comprises a ceramic top layer, a bonding layer, a thermal growth oxidation layer and a nickel-based high-temperature alloy substrate layer. In a high-temperature severe service environment, the interaction and the performance change among all components of the thermal barrier coating determine the failure form and the service life of the thermal barrier coating. The main failure modes of the thermal barrier coating comprise coating thinning or peeling, interface crack propagation, thermal property and mechanical property degradation, TGO growth, stress level change and the like, and in order to ensure the service safety of the thermal barrier coating, an effective method is urgently needed to realize the defect representation of the thermal barrier coating.
In the currently common nondestructive testing method, the laser-induced ultrasonic technology has the obvious advantage of being extremely sensitive to the surface characteristic change of the thermal barrier coating material, so that the method has great advantages in the aspect of nondestructive testing of the thermal barrier coating. The laser ultrasonic detection technology is a nondestructive detection technology which utilizes pulse laser to excite ultrasonic signals and is collected by a sensor. In recent years, the laser ultrasonic detection technology is remarkably developed and widely applied to the detection of defects such as metal material surface defect detection, metal surface residual stress detection, and the debonding and layering of resin-based composite materials of aviation parts.
The excitation mechanism of ultrasonic waves is classified into a thermoelastic mechanism and a thermal etching mechanism according to the amount of laser irradiation energy. The difference between the two is mainly whether the incident laser power density is above the material damage threshold. In order to achieve the purpose of nondestructive detection without damaging the thermal barrier coating material, the laser ultrasonic detection technology mainly adopts a thermal-elastic mechanism. For this purpose, the energy of the input pulse laser needs to be controlled, so that the laser power density loaded on the surface of the thermal barrier coating material does not exceed the damage threshold of the material, namely the temperature of the thermal barrier coating material after laser action does not exceed the ablation temperature threshold of the material.
Disclosure of Invention
The invention provides a laser-induced ultrasonic parameter optimization method and system aiming at the ablation phenomenon of a laser ultrasonic nondestructive testing technology when the laser ultrasonic nondestructive testing technology acts on a thermal barrier coating material, the requirement of nondestructive testing of a thermal barrier coating of a gas turbine blade is considered, the temperature threshold value of the ablation of the top layer of the thermal barrier coating is predicted by a simulation means, the laser parameter used for exciting ultrasonic waves is optimized, and the thermal barrier coating is ensured not to be damaged when the laser ultrasonic technology is applied to testing.
The invention adopts the following technical scheme:
a laser-induced ultrasonic parameter optimization method comprises the following steps:
s1, performing nondestructive testing on the thermal barrier coating material by using a laser ultrasonic technology, and constructing a thermal barrier coating geometric model based on COMSOL;
s2, performing simulation calculation by using the thermal barrier coating geometric model constructed in the step S1 to obtain the temperature field change and the temperature contour line of the material after the laser acts on the top layer of the thermal barrier coating;
and S3, according to the temperature field change and the temperature contour line obtained in the step S2, combining the temperature ablation threshold of the top layer of the thermal barrier coating, obtaining a pulse laser power density threshold which is correspondingly loaded, calculating and obtaining a laser energy threshold of the thermal barrier coating material which is ablated, and realizing the parameter optimization of laser-induced ultrasound.
Specifically, step S1 specifically includes:
s101, constructing a thermal barrier coating geometric model, converting the three-dimensional model into a two-dimensional model, selecting a section of a sample for calculation, and setting laser parameters;
s102, adding materials to the thermal barrier coating geometric model constructed in the step S101, and setting basic parameters of thermal barrier coating materials according to the characteristics of the thermal barrier coating materials;
s103, setting a physical field comprising solid heat transfer and solid mechanics, wherein the solid heat transfer simulates temperature field change of laser acted on a thermal barrier coating material, the solid mechanics simulates stress strain generated by the temperature field change, thermal-structure coupling is realized through a thermal expansion interface, and the physical process of laser ultrasound is simulated;
s104, setting boundary conditions of thermal barrier coating materials according to the temperature field change and the stress strain process of the step S103,
s105, calculating by adopting a mapping grid, and dividing the mapping grid according to the initial temperature change process of the step S103 and the spatial resolution required by ultrasonic wave propagation;
and S106, configuring a solver according to the required solving time resolution.
Further, in step S102, the thermal barrier coating material includes a nickel-based superalloy substrate, a bonding layer, and a ceramic top layer, the nickel-based superalloy substrate is Inconel 718, the bonding layer is NiCoCrAlY, the ceramic top layer is 8YSZ, and the basic parameters include a thermal expansion coefficient, a thermal conductivity coefficient, a constant pressure heat capacity, a density, and a poisson' S ratio.
Further, in step S104, the boundary conditions include a temperature field boundary condition and a stress field boundary condition of the thermal barrier coating material, the temperature field boundary condition includes an upper surface boundary condition and a lower surface boundary condition, and the upper surface boundary condition is determined according to the gaussian distribution and the generalized inward heat flux of the laser heat source in time and space; the boundary condition of the stress field meets the stress freedom of the upper surface and the lower surface of the thermal barrier coating material and low-reflection boundaries on two sides.
Further, the upper surface boundary conditions are:
Figure BDA0003312928430000031
the lower surface boundary conditions are:
Figure BDA0003312928430000032
the spatial gaussian distribution is given by:
Figure BDA0003312928430000041
wherein r is0Indicating the spot radius of the pulsed laser.
The temporal gaussian distribution is given by:
Figure BDA0003312928430000042
wherein, t0Indicating pulse laser rise time
Generalized inward heat flux an1(x, t) is:
an1(x,t)=Rc·I0·f(x)·g(t)
wherein R iscIs the absorption coefficient of the ceramic top layer, I0Is the pulsed laser power density.
Specifically, in step S105, the divided maximum grid cell size Δ satisfies the following condition:
Figure BDA0003312928430000043
wherein λ isminRepresenting the surface acoustic wave wavelength.
Specifically, in step S106, the solver uses a transient solver of COMSOL, the time step Δ t is modified in the transient solver configuration, the backward difference formula method in the solver is changed to the generalized α method, the step adopted by the solver is modified from free to manual control, and the time step Δ t satisfies the following condition:
Figure BDA0003312928430000044
wherein f ismaxRepresenting the highest frequency desired.
Specifically, in step S2, before calculating the geometric model of the thermal barrier coating, adding a domain point probe under the component definition, and observing the temperature change condition;
after the calculation of the thermal barrier coating geometric model is completed, post-processing operation is carried out in the result, which specifically comprises the following steps:
adding a two-dimensional drawing group for surface drawing, selecting temperature to obtain the temperature distribution condition after laser action, and adding the maximum and minimum values of the surface to obtain the temperature value of the surface under the laser action;
adding a two-dimensional drawing group, adding a contour option, and acquiring a temperature contour of the material;
and adding a one-dimensional drawing group, further drawing a point diagram, and judging the temperature change condition of different points on the model through the point diagram.
Specifically, in step S3, the temperature T is acquired0And calculating the pulse laser energy threshold value E when the thermal barrier coating material is ablated according to the laser power density I' corresponding to the lower thermal barrier coating material, and controlling the laser energy of a laser ultrasonic system used in the experiment by taking the pulse laser energy threshold value E as the highest upper limit so as to realize the parameter optimization of laser-induced ultrasound.
Another technical solution of the present invention is a laser-induced ultrasonic parameter optimization system, including:
the building module is used for carrying out nondestructive testing on the thermal barrier coating by applying a laser ultrasonic technology and building a thermal barrier coating geometric model based on COMSOL;
the calculation module is used for carrying out simulation calculation by utilizing the thermal barrier coating geometric model constructed by the construction module to obtain the temperature field change and the temperature contour line of the material after the laser acts on the top layer of the thermal barrier coating;
and the optimization module is used for acquiring a pulse laser power density threshold value correspondingly loaded according to the temperature field change and the temperature contour line acquired by the calculation module and in combination with the temperature ablation threshold value of the top layer of the thermal barrier coating, calculating and acquiring a laser energy threshold value of the thermal barrier coating material subjected to ablation, and realizing the parameter optimization of laser-induced ultrasound.
Compared with the prior art, the invention has at least the following beneficial effects:
the invention relates to a laser-induced ultrasonic parameter optimization method, which comprises the steps of obtaining the temperature field change of laser acting on the top layer of a thermal barrier coating through COMSOL software simulation calculation, obtaining a laser power density threshold value by combining the ablation temperature threshold value of the top layer of the thermal barrier coating, and further obtaining a laser energy threshold value, so as to limit the specific laser energy used by a laser ultrasonic system in an experiment, and further realize laser-induced ultrasonic parameter optimization. The method does not consume a large amount of resources, is simple and easy to realize, and achieves the purpose of performing laser ultrasonic nondestructive testing on the thermal barrier coating through parameter optimization.
Furthermore, in order to ensure that the material is not damaged when the laser ultrasonic technology is applied to detect the thermal barrier coating material, a simulation model of laser ultrasonic loading on the thermal barrier coating is constructed according to actual conditions.
Furthermore, in order to simulate a real experimental sample, the constructed geometric model material is strictly added according to a three-layer structure, and basic material parameters are set according to the thermophysical parameters of the actual sample.
Furthermore, the laser acts on the top layer of the thermal barrier coating material, the instantaneous temperature changes only on the near surface and is arranged at the interface of the multilayer material, and the temperature and the stress change are continuous. To simulate the above, the thermal barrier coating material boundary conditions were set to simulate a specific course of action.
Further, under laser irradiation, laser light energy absorbed by the surface of the thermal barrier coating is firstly converted into heat energy to raise the temperature of the surface layer, and then the laser light energy is diffused from the surface to the inside and from high temperature to low temperature. In order to simulate the real action process of laser ultrasound, setting heat flux as an upper surface boundary condition for simulating heat energy absorbed by a thermal barrier coating material, wherein the lower surface boundary condition shows that the temperature of the lower surface of the thermal barrier coating does not change in a short time; meanwhile, thermal stress is generated by temperature field change, the stress of the upper surface and the lower surface of the stress field is free to simulate the actual stress strain of the thermal barrier coating material, and the two sides meet the low-reflection boundary condition to reduce the boundary echo.
Furthermore, in order to meet the requirements of spatial resolution and calculation accuracy of ultrasonic wave propagation, and simultaneously consider the structure of geometric model comparison rules, a mapping grid is adopted for calculation, and the size of the maximum grid cell needs to be smaller than 1/4 of the wavelength of the surface acoustic wave.
Further, the laser is acted on the surface of the material, the pulse time of the action is ns order, and the requirement is sufficientTime resolution of, the time step size of
Figure BDA0003312928430000061
Furthermore, in order to obtain the temperature field distribution condition of the top layer of the thermal barrier coating after the laser action and further compare the temperature ablation threshold of the material of the top layer of the thermal barrier coating, simulation calculation is carried out through the constructed geometric model.
Further, in order to limit the specific laser energy used in the experiment and further realize laser-induced ultrasonic parameter optimization, the corresponding laser power density threshold is obtained by comparing the temperature field distribution of the top layer of the thermal barrier coating with the temperature ablation threshold, and then the laser energy threshold is calculated and obtained.
In conclusion, the method is simple and easy to implement, can realize laser-induced ultrasonic parameter optimization under the condition of not consuming a large number of resources, and achieves the purpose of nondestructive testing of the thermal barrier coating material.
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Drawings
FIG. 1 is a flow chart of the present invention;
FIG. 2 is a COMSOL simulation flow diagram;
FIG. 3 is a two-dimensional model mesh subdivision;
FIG. 4 is I0=5×1012W/m2A lower 9ns temperature field distribution diagram;
FIG. 5 is I0=5×1012W/m2Lower 9ns temperature contour plot;
FIG. 6 is I0=5×1012W/m2A temperature change curve of a laser irradiation center;
FIG. 7 is I0=1.73×1012W/m2Temperature change curve of the laser irradiation center.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be understood that the terms "comprises" and/or "comprising" indicate the presence of the stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It is also to be understood that the terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the specification of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
It should be further understood that the term "and/or" as used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.
Various structural schematics according to the disclosed embodiments of the invention are shown in the drawings. The figures are not drawn to scale, wherein certain details are exaggerated and possibly omitted for clarity of presentation. The shapes of various regions, layers and their relative sizes and positional relationships shown in the drawings are merely exemplary, and deviations may occur in practice due to manufacturing tolerances or technical limitations, and a person skilled in the art may additionally design regions/layers having different shapes, sizes, relative positions, according to actual needs.
Referring to fig. 1, the present invention provides a laser-induced ultrasonic parameter optimization method, which simulates a laser-induced ultrasonic process and obtains a temperature distribution after a laser acts on a thermal barrier coating top layer, so as to realize parameter optimization of laser-induced ultrasonic, and includes the following steps:
s1, under the background of nondestructive testing of the thermal barrier coating by applying a laser ultrasonic technology, constructing a thermal barrier coating geometric model based on COMSOL, and setting a physical field, grid division and solver configuration;
referring to fig. 2, the specific steps are as follows:
s101, constructing a thermal barrier coating geometric model and setting laser parameters
According to the structural characteristics of the thermal barrier coating, the experimental sample is established as follows: 1, converting a three-dimensional model into a two-dimensional model, and selecting a section of a sample for calculation in order to simplify the calculation amount and improve the calculation efficiency under the condition of not influencing the result, wherein the length of the geometric model is 30mm multiplied by the height of the geometric model is 2 mm; according to the laser ultrasonic system parameters, setting the relevant laser parameters as follows: the pulse width is 8ns, the laser spot radius is 0.5mm, and the laser pulse energy is adjustable and not more than 42.3mj at most.
S102, setting basic parameters of thermal barrier coating material
The method is mainly added according to a material library in simulation software, wherein some undefined parameters such as thermal expansion coefficient, thermal conductivity, constant pressure heat capacity, density, Poisson ratio and the like are input through actual sample parameters.
The thermal barrier coating material comprises a nickel-based high-temperature alloy substrate, a bonding layer and a ceramic top layer, wherein the nickel-based high-temperature alloy substrate is Inconel 718 and is led in through a COMSOL software library; the bonding layer material is NiCoCrAlY, the ceramic top layer material is 8YSZ, after the bonding layer material is led in through a material library, some undefined parameters such as thermal expansion coefficient, thermal conductivity coefficient, constant pressure heat capacity, density, Poisson ratio and the like are input in a user-defined mode according to actual sample parameters.
S103, setting a physical field
The laser ultrasonic technology principle is combined, namely laser acts on the surface of the thermal barrier coating material, the thermal barrier coating material absorbs laser energy to cause local temperature rise, the volume of the local material is rapidly expanded due to thermal expansion, and elastic waves are formed on the surface of the thermal barrier coating material and spread to the inside and the periphery. Unlike traditional acoustic simulation, the physical process of the invention comprises heat transfer and vibration, for this reason, the invention selects a physical field comprising solid heat transfer and solid mechanics, and the coupling of the two physical fields is realized through a thermal expansion interface.
According to the principle that laser ultrasonic thermoelastic excites ultrasonic waves, the laser generates the ultrasonic waves in the following three processes:
(1) the laser acts on the surface of the thermal barrier coating material to generate a local heat source;
(2) the thermal barrier coating material absorbs laser energy to cause local temperature rise, and elastic waves are formed on the surface of the thermal barrier coating material and spread to the inside and the periphery;
(3) the local heat source generates thermal expansion to cause the local thermal barrier coating material volume to expand sharply, thereby generating a transient displacement field.
Unlike traditional acoustic simulation, the physical process of the invention comprises heat transfer and vibration, for this reason, the invention selects a physical field interface comprising a solid heat transfer and solid mechanics module, and the coupling of the two physical fields is realized through a thermal expansion interface. The solid heat transfer module realizes that the laser heats the surface of the thermal barrier coating material to cause the surface to generate instant temperature rise, and the solid mechanical module simulates the volume expansion of the thermal barrier coating material to form a transient displacement field. The coupling between solid mechanics and the solid heat transfer module is realized through a thermal expansion interface in the multi-physical field coupling.
S104, setting boundary conditions
The thermal barrier coating of the research object of the invention is a layered material, and considering the structural characteristics of the thermal barrier coating material, besides the boundary conditions needed to be met by the upper surface and the lower surface, certain thermal contact conditions and continuity conditions are also met at the interface of the layer, which are specifically as follows:
the upper surface boundary conditions are:
Figure BDA0003312928430000101
the lower surface boundary conditions are:
Figure BDA0003312928430000102
the interface of each layer of the multilayer material is in good thermal contact, namely:
Figure BDA0003312928430000103
Figure BDA0003312928430000104
the initial temperature was set as:
Ti(r,z,t)=293.15 K (5)
wherein, Ti(r, z, t) is the temperature distribution at time t, KiFor heat transfer coefficient, an1(x, t) is heat flux, r is axial length, z is depth, h is thin layer thickness, and i ═ 1,2,3, …, N-1 indicates the material parameters of the ith layer.
Stress field boundary conditions:
on the basis of temperature field analysis, thermal stress change of the thermal barrier coating material is realized through a thermal expansion interface, the upper surface and the lower surface of the thermal barrier coating material meet free boundary conditions, stress continuity and displacement continuity are met on a contact interface of the thermal barrier coating material, initial stress is set to be zero, and low-reflection boundaries are arranged on two sides of the thermal barrier coating material.
According to the actual distribution situation of the laser heat sources, the laser heat sources need to be arranged to be in Gaussian distribution in time and space. Different from directly adding a Gaussian distribution function, the method sets a function expression by respectively adding two analytical functions in COMSOL so as to meet the Gaussian distribution on time and space.
The spatial gaussian distribution is given by:
Figure BDA0003312928430000111
wherein r is0Indicating the spot radius of the pulsed laser.
The temporal gaussian distribution is given by:
Figure BDA0003312928430000112
wherein, t0Indicating the pulsed laser rise time.
The laser is loaded on the surface of the thermal barrier coating material, the thermal diffusivity of the ceramic top layer material is considered to be low, the laser action range is only within a smaller range of the surface layer of the thermal barrier coating material, the convective heat transfer and the radiative heat transfer are neglected, the laser loading is simulated by adding the boundary heat flux, and the expression of the generalized inward heat flux an1(x, t) is set as follows in combination with the analytic functions of time and space:
an1(x,t)=Rc·I0·f(x)·g(t) (8)
wherein R iscIs the absorption coefficient of the ceramic top layer, I0Is the pulsed laser power density.
S105, grid division
The COMSOL grid is excessively densely divided, so that the degree of freedom is excessive, the calculation memory is excessively large, and the calculation efficiency is excessively low; too sparse of mesh partitioning may result in an inability to prepare to resolve the physical process. In consideration of the action process of laser loading on the material, the invention adopts a variable grid technology in calculation, namely, a dense grid is arranged in a region with rapid temperature change or a region with high temperature gradient, and a sparse grid is arranged in a region with gentle temperature change.
For the total mesh size, considering the more regular structure of the geometric model and the size of the calculated amount, the invention adopts the mapping mesh for calculation, as shown in fig. 3. To meet the accuracy requirements of ultrasonic propagation, the maximum mesh size needs to satisfy the following equation:
Figure BDA0003312928430000121
wherein λ isminRepresenting the surface acoustic wave wavelength.
S106 solver configuration
The invention adopts a COMSOL software default transient solver to modify the solving time. The laser acts on the surface of the thermal barrier coating material, the acting pulse time is ns grade, and in order to meet enough time resolution, the time step length meets the following formula:
Figure BDA0003312928430000122
wherein f ismaxRepresenting the highest frequency desired.
And (3) modifying the time step length in the configuration of the transient solver by adopting a COMSOL default transient solver, changing a backward difference formula method in the solver into a generalized alpha method, modifying the step length adopted by the solver from free to manual control, and setting the solving step length to be 1 ns. Considering that the pulse width of the laser is 8ns, after the laser acts, the instantaneous temperature rise of the material occurs in a short time, the total calculation time is set to be 50ns, and the temperature probe diagram is used for judging that the temperature change of the ceramic tends to be stable at the time.
S2, obtaining the temperature field change and the temperature contour line of the material after the laser acts on the top layer of the thermal barrier coating through COMSOL simulation calculation in the step S1;
before calculation of the thermal barrier coating geometric model, a 'domain point probe' is added under the component definition, and the temperature change condition is observed.
After the calculation of the thermal barrier coating geometric model is completed, post-processing operation is carried out in the result:
(1) adding a two-dimensional drawing group for surface drawing, selecting temperature to obtain the temperature distribution condition after laser action, and adding the maximum and minimum values of the surface to obtain the temperature value of the surface under the laser action;
(2) adding a two-dimensional drawing group and adding a contour option to obtain a temperature contour of the material;
(3) and adding a one-dimensional drawing group, further drawing a point diagram, and judging the temperature change condition of different points on the model through the point diagram. As shown in fig. 4, 5, 6 and 7.
And S3, combining the laser ablation temperature threshold of the thermal barrier coating top layer in the step S2, obtaining the power density of the correspondingly loaded pulse laser, calculating and obtaining the laser ablation energy, and realizing the parameter optimization of laser-induced ultrasound.
And adding a 'parametric scan' study in COMSOL, and acquiring the temperature field distribution conditions under different heat fluxes through parametric scanning of laser power density in combination with the temperature acquisition method in the step S2.
Laser power density I0The relationship with the heat flux an1(x, t) is as in equation (8).
By looking up relevant literature data, the temperature T of the ceramic top layer of the thermal barrier coating material is known0At 2680 c, 2953.15K, ablation occurs. Adding power density variable I in parametric scan research0First of all, a relatively low value I is set1Then a relatively high value I is set2Obtaining I by calculation1And I2A corresponding temperature rise; the range 10 is determined by continuously narrowing the interval by bisection12~1013Setting the parametric scan start to 1012The scanning step length is 5 × 1011Stop at 1013. The temperature T is obtained after the temperature threshold is judged to be reached by combining a temperature probe curve through continuous refinement dichotomy and parametric scanning0The corresponding laser power density I' of the lower thermal barrier coating material, such that according to formula (11):
Figure BDA0003312928430000131
and calculating the energy threshold E of the pulse laser when the thermal barrier coating material is ablated so as to obtain the laser parameter threshold when the thermal barrier coating material is ablated.
Calculated as in I0≈1.55×1012W/m2When the material on the top layer of the thermal barrier coating is ablated, the pulse laser energy threshold value E is approximately equal to 9.74mj calculated by the formula (11).
In another embodiment of the present invention, a laser-induced ultrasonic parameter optimization system is provided, which can be used to implement the above laser-induced ultrasonic parameter optimization method.
The construction module is used for carrying out nondestructive testing on the thermal barrier coating by applying a laser ultrasonic technology and constructing a thermal barrier coating geometric model based on COMSOL;
the calculation module is used for carrying out simulation calculation by utilizing the thermal barrier coating geometric model constructed by the construction module to obtain the temperature field change and the temperature contour line of the material after the laser acts on the top layer of the thermal barrier coating;
and the optimization module is used for acquiring a pulse laser power density threshold value correspondingly loaded according to the temperature field change and the temperature contour line acquired by the calculation module and in combination with the temperature ablation threshold value of the top layer of the thermal barrier coating, calculating and acquiring a laser energy threshold value of the thermal barrier coating material subjected to ablation, and realizing the parameter optimization of laser-induced ultrasound.
In yet another embodiment of the present invention, a terminal device is provided that includes a processor and a memory for storing a computer program comprising program instructions, the processor being configured to execute the program instructions stored by the computer storage medium. The Processor may be a Central Processing Unit (CPU), or may be other general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), an off-the-shelf Programmable gate array (FPGA) or other Programmable logic device, a discrete gate or transistor logic device, a discrete hardware component, etc., which is a computing core and a control core of the terminal, and is adapted to implement one or more instructions, and is specifically adapted to load and execute one or more instructions to implement a corresponding method flow or a corresponding function; the processor of the embodiment of the invention can be used for the operation of the laser-induced ultrasonic parameter optimization method, and comprises the following steps:
performing nondestructive testing on the thermal barrier coating material by using a laser ultrasonic technology, and constructing a thermal barrier coating geometric model based on COMSOL; carrying out simulation calculation by utilizing a thermal barrier coating geometric model to obtain the temperature field change and the temperature contour line of the material after the laser acts on the top layer of the thermal barrier coating; and according to the temperature field change and the temperature contour line, combining the temperature ablation threshold of the top layer of the thermal barrier coating to obtain the power density threshold of the correspondingly loaded pulse laser, and calculating to obtain the laser energy threshold of the thermal barrier coating material subjected to ablation so as to realize the parameter optimization of laser-induced ultrasound.
In still another embodiment of the present invention, the present invention further provides a storage medium, specifically a computer-readable storage medium (Memory), which is a Memory device in a terminal device and is used for storing programs and data. It is understood that the computer readable storage medium herein may include a built-in storage medium in the terminal device, and may also include an extended storage medium supported by the terminal device. The computer-readable storage medium provides a storage space storing an operating system of the terminal. Also, one or more instructions, which may be one or more computer programs (including program code), are stored in the memory space and are adapted to be loaded and executed by the processor. It should be noted that the computer-readable storage medium may be a high-speed RAM memory, or may be a non-volatile memory (non-volatile memory), such as at least one disk memory.
One or more instructions stored in the computer-readable storage medium can be loaded and executed by the processor to implement the corresponding steps of the laser-induced ultrasonic parameter optimization method in the above embodiments; one or more instructions in the computer-readable storage medium are loaded by the processor and perform the steps of:
performing nondestructive testing on the thermal barrier coating material by using a laser ultrasonic technology, and constructing a thermal barrier coating geometric model based on COMSOL; carrying out simulation calculation by utilizing a thermal barrier coating geometric model to obtain the temperature field change and the temperature contour line of the material after the laser acts on the top layer of the thermal barrier coating; and according to the temperature field change and the temperature contour line, combining the temperature ablation threshold of the top layer of the thermal barrier coating to obtain the power density threshold of the correspondingly loaded pulse laser, and calculating to obtain the laser energy threshold of the thermal barrier coating material subjected to ablation so as to realize the parameter optimization of laser-induced ultrasound.
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The method disclosed by the invention predicts the threshold parameter of the laser ablation thermal barrier coating through COMSOL simulation software, calculates by constructing a two-dimensional model, adds a one-dimensional drawing group and a two-dimensional drawing group in the result to obtain the temperature distribution condition after laser action, and parametrically scans the laser power density to obtain the temperature change condition under different laser power densities, so as to obtain the laser power density threshold corresponding to the ablation temperature threshold, and calculates by a formula to obtain the laser energy threshold.
Compared with the prior art, the method has the advantages that: on one hand, finite element simulation experiments are carried out through COMSOL software, and a laser power density threshold corresponding to an ablation temperature threshold is obtained through parametric scanning, so that a laser energy threshold is obtained, and the method is simple and easy to implement; on the other hand, the method saves a large amount of experimental materials, predicts the laser ablation energy threshold of the thermal barrier coating under the condition of not consuming a large amount of resources, realizes the nondestructive detection of the thermal barrier coating by effectively restricting the upper limit of the laser energy, and ensures that the materials are not damaged.
In summary, according to the laser-induced ultrasonic parameter optimization method and system, the temperature distribution of the material after the laser acts on the top layer of the thermal barrier coating is obtained through COMSOL software simulation calculation, the laser ablation temperature threshold of the top layer of the thermal barrier coating is combined to obtain the correspondingly loaded pulse laser power density, the laser energy threshold is further obtained through formula calculation, the threshold is taken as the upper limit, the specific laser energy used by the laser ultrasonic system in the experiment is limited, and therefore the parameter optimization of laser-induced ultrasound is achieved.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.

Claims (10)

1. A laser-induced ultrasonic parameter optimization method is characterized by comprising the following steps:
s1, performing nondestructive testing on the thermal barrier coating material by using a laser ultrasonic technology, and constructing a thermal barrier coating geometric model based on COMSOL;
s2, performing simulation calculation by using the thermal barrier coating geometric model constructed in the step S1 to obtain the temperature field change and the temperature contour line of the material after the laser acts on the top layer of the thermal barrier coating;
and S3, according to the temperature field change and the temperature contour line obtained in the step S2, combining the temperature ablation threshold of the top layer of the thermal barrier coating, obtaining a pulse laser power density threshold which is correspondingly loaded, calculating and obtaining a laser energy threshold of the thermal barrier coating material which is ablated, and realizing the parameter optimization of laser-induced ultrasound.
2. The method according to claim 1, wherein step S1 is specifically:
s101, constructing a thermal barrier coating geometric model, converting the three-dimensional model into a two-dimensional model, selecting a section of a sample for calculation, and setting laser parameters;
s102, adding materials to the thermal barrier coating geometric model constructed in the step S101, and setting basic parameters of thermal barrier coating materials according to the characteristics of the thermal barrier coating materials;
s103, setting a physical field comprising solid heat transfer and solid mechanics, wherein the solid heat transfer simulates temperature field change of laser acted on a thermal barrier coating material, the solid mechanics simulates stress strain generated by the temperature field change, thermal-structure coupling is realized through a thermal expansion interface, and the physical process of laser ultrasound is simulated;
s104, setting boundary conditions of thermal barrier coating materials according to the temperature field change and the stress strain process of the step S103,
s105, calculating by adopting a mapping grid, and dividing the mapping grid according to the initial temperature change process of the step S103 and the spatial resolution required by ultrasonic wave propagation;
and S106, configuring a solver according to the required solving time resolution.
3. The method of claim 2, wherein in step S102, the thermal barrier coating material comprises a ni-based superalloy substrate, a bond coat layer, and a ceramic top layer, the ni-based superalloy substrate is Inconel 718, the bond coat material is NiCoCrAlY, the ceramic top layer material is 8YSZ, and the basic parameters include thermal expansion coefficient, thermal conductivity coefficient, constant pressure heat capacity, density, and poisson' S ratio.
4. The method of claim 2, wherein in step S104, the boundary conditions include temperature field boundary conditions and stress field boundary conditions of the thermal barrier coating material, the temperature field boundary conditions include upper surface boundary conditions and lower surface boundary conditions, the upper surface boundary conditions are determined according to a gaussian distribution and a generalized inward heat flux of the laser heat source in time and space; the boundary condition of the stress field meets the stress freedom of the upper surface and the lower surface of the thermal barrier coating material and low-reflection boundaries on two sides.
5. The method of claim 4, wherein the upper surface boundary conditions are:
Figure FDA0003312928420000021
the lower surface boundary conditions are:
Figure FDA0003312928420000022
the spatial gaussian distribution is given by:
Figure FDA0003312928420000023
wherein r is0Represents the spot radius of the pulsed laser;
the temporal gaussian distribution is given by:
Figure FDA0003312928420000024
wherein, t0Indicating pulse laser rise time
Generalized inward heat flux an1(x, t) is:
an1(x,t)=Rc·I0·f(x)·g(t)
wherein R iscIs the absorption coefficient of the ceramic top layer, I0Is the pulsed laser power density.
6. The method according to claim 1, wherein in step S105, the divided maximum grid cell size Δ satisfies the following condition:
Figure FDA0003312928420000031
wherein λ isminRepresenting the surface acoustic wave wavelength.
7. The method as claimed in claim 1, wherein in step S106, the solver uses a COMSOL transient solver, the time step Δ t is modified in the transient solver configuration, the backward difference formula method in the solver is changed to a generalized α method, the step used by the solver is modified from free to manual control, and the time step Δ t satisfies the following condition:
Figure FDA0003312928420000032
wherein f ismaxRepresenting the highest frequency desired.
8. The method of claim 1, wherein in step S2, before calculating the geometric model of the thermal barrier coating, a domain point probe is added under the component definition, and the temperature variation is observed;
after the calculation of the thermal barrier coating geometric model is completed, post-processing operation is carried out in the result, which specifically comprises the following steps:
adding a two-dimensional drawing group for surface drawing, selecting temperature to obtain the temperature distribution condition after laser action, and adding the maximum and minimum values of the surface to obtain the temperature value of the surface under the laser action;
adding a two-dimensional drawing group, adding a contour option, and acquiring a temperature contour of the material;
and adding a one-dimensional drawing group, further drawing a point diagram, and judging the temperature change condition of different points on the model through the point diagram.
9. The method according to claim 1, wherein in step S3, the temperature T is obtained0And calculating the pulse laser energy threshold value E when the thermal barrier coating material is ablated according to the laser power density I' corresponding to the lower thermal barrier coating material, and controlling the laser energy of a laser ultrasonic system used in the experiment by taking the pulse laser energy threshold value E as the highest upper limit so as to realize the parameter optimization of laser-induced ultrasound.
10. A laser-induced ultrasound parameter optimization system, comprising:
the building module is used for carrying out nondestructive testing on the thermal barrier coating by applying a laser ultrasonic technology and building a thermal barrier coating geometric model based on COMSOL;
the calculation module is used for carrying out simulation calculation by utilizing the thermal barrier coating geometric model constructed by the construction module to obtain the temperature field change and the temperature contour line of the material after the laser acts on the top layer of the thermal barrier coating;
and the optimization module is used for acquiring a pulse laser power density threshold value correspondingly loaded according to the temperature field change and the temperature contour line acquired by the calculation module and in combination with the temperature ablation threshold value of the top layer of the thermal barrier coating, calculating and acquiring a laser energy threshold value of the thermal barrier coating material subjected to ablation, and realizing the parameter optimization of laser-induced ultrasound.
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