阅读说明：本技术 一种增材制造高强铝合金的应力场测试方法及系统 (Stress field testing method and system for additive manufacturing high-strength aluminum alloy ) 是由 宋彬 夏建强 于 2020-12-16 设计创作，主要内容包括：本发明公开一种增材制造高强铝合金的应力场测试方法及系统,所述增材制造高强铝合金的应力场测试方法包括测量零件表层残余应力,并逐层去除零件表层材料,以获得残余应力场测量值,在ANSYS软件中建立有限元模型,测量所述残余应力场,对零件表面涂覆保护层,将零件表面进行热处理强化,以得到处理后的零件,对所述处理后的零件查找热振复合工艺参数组合,确定热振复合应力均化工艺方案。本发明的增材制造高强铝合金的应力场测试方法不仅能够测量材料表面残余应力或规则形状试件的内部残余应力,而且能够实现对内部残余应力场的精确测量。(The invention discloses a stress field testing method and a system for additive manufacturing of a high-strength aluminum alloy. The stress field testing method for the additive manufacturing high-strength aluminum alloy can measure the residual stress on the surface of the material or the internal residual stress of the test piece in the regular shape, and can realize accurate measurement of the internal residual stress field.)

1. A stress field testing method for additive manufacturing of a high-strength aluminum alloy is characterized by comprising the following steps:

measuring the residual stress of the surface layer of the part, and removing the material of the surface layer of the part layer by layer to obtain a residual stress field measured value;

establishing a finite element model in ANSYS software, and measuring the residual stress field;

coating a protective layer on the surface of the part;

carrying out heat treatment strengthening on the surface of the part to obtain a treated part;

and searching a thermal vibration composite process parameter combination for the processed part, and determining a thermal vibration composite stress homogenization process scheme.

2. The method of claim 1, wherein the method comprises the steps of: and measuring the residual stress of the surface layer of the part by an X-ray diffraction method or a laser speckle interference blind hole method.

3. The method of claim 1, wherein the method comprises the steps of: and removing the part surface layer material layer by means of mechanical milling or chemical milling.

4. The method of claim 1, wherein the step of measuring the residual stress field comprises:

correcting the finite element model to obtain a corrected model;

carrying out simulation modeling on the corrected model by a laser melting deposition method to obtain a modeled model;

and analyzing the simulation result of the residual stress field of the modeled model to obtain the measurement result of the residual stress field.

5. The method of claim 1, wherein the method comprises the steps of: the protective layer is made of a mixture of organic silicon, epoxy resin and graphite powder, the volume ratio of the organic silicon to the epoxy resin is 1:2, and the mass ratio of the organic silicon to the graphite powder is 6: 1-15: 1.

6. the method of claim 1, wherein the step of heat treating the surface of the part to strengthen comprises:

and (3) placing the surface of the part in an air heat treatment furnace at the temperature of 200-230 ℃, preserving heat for 3-5 h, introducing argon or nitrogen, quenching and strengthening by gas, cooling to room temperature, and refining the granular tissue into particles with the diameter of 0.3-0.8 micrometer.

7. The method of claim 1, wherein the method comprises the steps of: the thermal vibration composite process parameters comprise one or more of vibration frequency, amplitude, vibration excitation position, vibration time, heating temperature and heat preservation time.

8. The method of claim 5, wherein the method comprises: the thickness of the coating protective layer is 0.8-1.2 mm.

9. The method of claim 6, wherein the method comprises: the tensile strength of the part reaches 800-1240MPa, and the elongation after fracture is 4-12%.

10. A stress field testing system for additive manufacturing of a high strength aluminum alloy, comprising:

the first measurement module is used for measuring the residual stress of the surface layer of the part and removing the material of the surface layer of the part layer by layer to obtain a residual stress field measurement value;

the second measurement module is used for establishing a finite element model in ANSYS software and measuring the residual stress field;

the coating module is used for coating a protective layer on the surface of the part;

the heat treatment strengthening module is used for carrying out heat treatment strengthening on the surface of the part to obtain a treated part;

and the combination module is used for searching the thermal vibration composite process parameter combination for the processed part and determining the thermal vibration composite stress homogenization process scheme.

Technical Field

The invention relates to the technical field of aluminum alloy additive manufacturing, in particular to a stress field testing method and system for high-strength aluminum alloy additive manufacturing.

Background

The high-strength aluminum alloy is widely applied to aerospace main bearing structural members due to excellent high specific strength, high temperature resistance and corrosion resistance. Influenced by the inherent characteristics of the high-strength aluminum alloy. The traditional machining method of cutting machining is adopted to manufacture large-scale complex high-strength aluminum alloy structural parts, and the defects of low material utilization rate, long production period, high machining cost and the like exist. In recent years, the application of Laser Engineered Net Shaping (LENS) additive manufacturing technology to manufacture large-scale high-performance metal components has gradually become one of leading research hotspots in the crossing field of domestic and foreign advanced manufacturing technology and material processing engineering, and has received high attention from governments, industries and academia worldwide. Compared with the traditional large-scale metal component manufacturing technology such as forging and cutting processing or forging and welding, the laser near-net forming process has the characteristics of short manufacturing flow, fine crystal grains, uniform components, high material utilization rate and the like. The technology is expected to provide a new technology approach with rapidness, flexibility, low cost, high performance and short period for manufacturing large and medium-sized metal components difficult to process in national defense and industrial major equipment.

Most of the existing residual stress testing methods can only measure the surface residual stress of a material or the internal residual stress of a test piece with a regular shape, so that improvement is urgently needed.

Disclosure of Invention

In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a stress field testing method and system for additive manufacturing of a high-strength aluminum alloy, which are used to solve the problem that most of the testing methods in the prior art can only measure the residual stress on the surface of a material or the internal residual stress of a regular-shaped test piece.

To achieve the above and other related objects, the present invention provides a stress field testing method for additive manufacturing of a high strength aluminum alloy, including:

measuring the residual stress of the surface layer of the part, and removing the material of the surface layer of the part layer by layer to obtain a residual stress field measured value;

establishing a finite element model in ANSYS software, and measuring the residual stress field;

coating a protective layer on the surface of the part;

carrying out heat treatment strengthening on the surface of the part to obtain a treated part;

and searching a thermal vibration composite process parameter combination for the processed part, and determining a thermal vibration composite stress homogenization process scheme.

In one embodiment of the invention, the residual stress of the surface layer of the part is measured by an X-ray diffraction method or a laser speckle interference blind hole method.

In one embodiment of the invention, the part surface layer material is removed layer by means of mechanical milling or chemical milling.

In an embodiment of the invention, the step of measuring the residual stress field includes:

correcting the finite element model to obtain a corrected model;

carrying out simulation modeling on the corrected model by a laser melting deposition method to obtain a modeled model;

and analyzing the simulation result of the residual stress field of the modeled model to obtain the measurement result of the residual stress field.

In an embodiment of the present invention, the protective layer material is a mixture of silicone, epoxy resin and graphite powder, a volume ratio of the silicone to the epoxy resin is 1:2, and a mass ratio of the silicone to the graphite powder is 6: 1-15: 1.

in an embodiment of the present invention, the step of performing heat treatment strengthening on the surface of the part includes:

and (3) placing the surface of the part in an air heat treatment furnace at the temperature of 200-230 ℃, preserving heat for 3-5 h, introducing argon or nitrogen, quenching and strengthening by gas, cooling to room temperature, and refining the granular tissue into particles with the diameter of 0.3-0.8 micrometer.

In an embodiment of the invention, the thermal vibration composite process parameter includes one or more of vibration frequency, amplitude, vibration position, vibration time, heating temperature and heat preservation time.

In one embodiment of the invention, the thickness of the coating protective layer is 0.8-1.2 mm.

In an embodiment of the invention, the tensile strength of the part reaches 800-1240MPa, and the elongation after fracture is 4% -12%.

The invention also provides a stress field testing system for additive manufacturing of the high-strength aluminum alloy, which comprises the following steps:

the first measurement module is used for measuring the residual stress of the surface layer of the part and removing the material of the surface layer of the part layer by layer to obtain a residual stress field measurement value;

the second measurement module is used for establishing a finite element model in ANSYS software and measuring the residual stress field;

the coating module is used for coating a protective layer on the surface of the part;

the heat treatment strengthening module is used for carrying out heat treatment strengthening on the surface of the part to obtain a treated part;

and the combination module is used for searching the thermal vibration composite process parameter combination for the processed part and determining the thermal vibration composite stress homogenization process scheme.

As described above, the method and system for testing the stress field of the additive manufacturing high-strength aluminum alloy of the present invention have the following beneficial effects:

the stress field testing method for the additive manufacturing high-strength aluminum alloy can measure the residual stress on the surface of the material or the internal residual stress of the test piece in the regular shape, and can realize accurate measurement of the internal residual stress field.

According to the stress field testing method for the additive manufacturing high-strength aluminum alloy, disclosed by the invention, the residual stress evolution rule in the part in the additive manufacturing process is obtained through simulation calculation. And correcting the simulation model based on the actual measurement result to make the simulation result consistent with the actual measurement result, thereby improving the accuracy and effectiveness of the simulation model in the laser near-net-shape additive manufacturing process.

Drawings

Fig. 1 is a working schematic diagram of a stress field testing method for additive manufacturing of a high-strength aluminum alloy according to an embodiment of the present application.

Fig. 2 is a flowchart of a stress field testing method of the additive manufacturing high-strength aluminum alloy in fig. 1 according to an embodiment of the present application, in step S2.

Fig. 3 is a schematic structural block diagram of a stress field testing system for additive manufacturing of a high-strength aluminum alloy according to an embodiment of the present disclosure.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict.

It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention, and the drawings only show the components related to the present invention rather than the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.

Referring to fig. 1, fig. 1 is a working schematic diagram of a stress field testing method for additive manufacturing of a high-strength aluminum alloy according to an embodiment of the present disclosure. Aiming at the residual stress forming mechanism and the distribution rule of the high-strength aluminum alloy manufactured by the laser near-net-shape additive manufacturing, the stress field testing method for the high-strength aluminum alloy manufactured by the additive manufacturing develops the research of the thermal aging and vibration aging processes under different process parameters, and obtains the microstructure evolution rule and the residual stress elimination effect under different process parameters. Most of the existing residual stress testing methods can only measure the surface residual stress of a material or the internal residual stress of a test piece with a regular shape. The evaluation of the residual stress field inside the complex-shaped part is mainly carried out by a numerical simulation method. The invention combines the 'unit life and death technology' in finite element simulation with an intelligent optimization algorithm, and realizes the accurate measurement of the internal residual stress field through the finite element simulation and the optimization iterative computation. The thermal vibration composite aging has the advantages of both thermal aging and vibration aging, related researches are still in a starting stage, and the thermal vibration composite stress homogenization mechanism of metal additive manufacturing parts still needs to be researched. The method is based on the residual stress distribution characteristics and the thermal aging and vibration aging stress elimination mechanism of the additive manufacturing high-strength aluminum alloy, researches the organization evolution and stress change rule under the thermal vibration coupling effect, and discloses the thermal vibration composite stress homogenization mechanism of the additive manufacturing aluminum alloy. The residual stress in the metal material for additive manufacturing is large, and the dimensional stability and the mechanical property of the part are seriously influenced. The invention combines a thermal-structure coupling numerical simulation model and a thermal vibration composite stress homogenization experiment, explores the influence of each key process parameter on the stress elimination effect, determines a thermal vibration composite stress homogenization scheme aiming at the additive manufacturing of the aluminum alloy, and provides a basis for the application of the process.

Step S1, as shown in fig. 1, measures the residual stress of the surface layer of the part, and removes the material of the surface layer of the part layer by layer to obtain the residual stress field measurement value. And step S2, establishing a finite element model in ANSYS software, and measuring the residual stress field. And step S3, coating a protective layer on the surface of the part. And step S4, performing heat treatment strengthening on the surface of the part to obtain the treated part. And step S5, searching a thermal vibration composite process parameter combination for the processed part, and determining a thermal vibration composite stress homogenization process scheme. Specifically, the residual stress of the surface layer of the part is measured by an X-ray diffraction method or a laser speckle interference blind hole method. And removing the part surface layer material layer by means of mechanical milling or chemical milling. The protective layer is made of a mixture of organic silicon, epoxy resin and graphite powder, the volume ratio of the organic silicon to the epoxy resin is 1:2, and the mass ratio of the organic silicon to the graphite powder is 6: 1-15: 1. the thickness of the coating protective layer is 0.8-1.2 mm. The step of carrying out heat treatment strengthening on the surface of the part comprises the following steps: and (3) placing the surface of the part in an air heat treatment furnace at the temperature of 200-230 ℃, preserving heat for 3-5 h, introducing argon or nitrogen, quenching and strengthening by gas, cooling to room temperature, and refining the granular tissue into particles with the diameter of 0.3-0.8 micrometer. The tensile strength of the part reaches 800-1240MPa, and the elongation after fracture is 4-12%. The thermal vibration composite process parameters comprise one or more of vibration frequency, amplitude, vibration excitation position, vibration time, heating temperature and heat preservation time.

As shown in fig. 1, the residual stress of the surface layer of the part is measured by an X-ray diffraction method or a laser speckle interference blind hole method, and then the material of the surface layer of the part is removed layer by a stripping method. And stripping, namely removing the surface layer material by adopting a mechanical milling or chemical milling mode, and then measuring the surface residual stress after stripping. And obtaining the residual stress value of each layer through layer-by-layer removal and residual stress test. Combining optimization software ISIGHT with finite element software ANSYS, establishing a finite element model in the ANSYS software, setting correction factors of corresponding units of a release layer every release layer, and performing static solution to generate a residual stress field analysis file; analyzing an operation file and a result file of ANSYS by using an Mdol language of ISIGHT, and calling the ANSYS to perform dynamic analysis; and setting the value of a correction factor at the ISIGHT, selecting a proper intelligent optimization algorithm to perform iterative calculation by taking the residual stress calculation value of the 'release' layer and the error obtained by testing as an optimization target until the error condition is met. And obtaining the actual residual stress value of each layer through layer-by-layer iteration.

As shown in FIG. 1, based on the stress relief effect and mechanism of thermal aging and vibratory aging, the structure evolution and stress change rule under the action of thermal vibration coupling is explored in a mode of combining thermal-structure field coupling numerical simulation, a stress homogenization technology, a residual stress test and metallographic structure analysis, and the stress relief mechanism of the additive manufacturing high-strength aluminum alloy is disclosed. The research on the additive manufacturing high-strength aluminum alloy thermal vibration composite stress homogenization process comprises the following steps: the thermal-force coupling numerical simulation and the thermal vibration composite stress homogenization experiment are combined, parameters such as vibration frequency, amplitude, vibration excitation position, vibration time, heating temperature and the like are explored, and the influence on the stress elimination effect of the high-strength aluminum alloy manufactured by laser near-net-shape additive manufacturing is explored. And optimizing the combination of thermal vibration composite process parameters by taking the optimal stress homogenization effect as a target to determine a stress homogenization scheme.

Referring to fig. 2, fig. 2 is a flowchart illustrating a stress field testing method of the additive manufacturing high-strength aluminum alloy shown in fig. 1 according to an embodiment of the present application in step S2. The step of measuring the residual stress field in step S2 includes: and step S21, correcting the finite element model to obtain a corrected model. And step S22, carrying out simulation modeling on the corrected model by a laser melting deposition method to obtain a modeled model. And step S23, analyzing the simulation result of the residual stress field of the modeled model to obtain the measurement result of the residual stress field.

As shown in FIG. 2, a multi-physical field numerical simulation model of the laser near-net-shape additive manufacturing process is established by considering the factors of material thermodynamic characteristics, laser power, scanning path and speed, molten pool size, molten pool temperature field and the like. And obtaining the evolution rule of the residual stress inside the part in the additive manufacturing process through simulation calculation. And correcting the simulation model based on the actual measurement result to make the simulation result consistent with the actual measurement result, thereby improving the accuracy and effectiveness of the simulation model in the laser near-net-shape additive manufacturing process. Based on the thermal aging and vibration aging stress homogenization mechanism, the research on the thermal vibration composite stress homogenization mechanism of the high-strength aluminum alloy manufactured by the additive manufacturing is carried out by combining the structural characteristics and the residual stress distribution rule of the aluminum alloy manufactured by the laser near-net-shape additive manufacturing. The method is characterized in that the structure evolution and stress change rules under the thermal action, the vibration action and the thermal vibration coupling action are respectively explored in a mode of combining thermal-structure field coupling numerical simulation, a stress homogenization experiment, a residual stress test and metallographic structure analysis, and the stress release mechanism of the additive manufacturing aluminum alloy is disclosed. Designing and developing thermal vibration composite process equipment aiming at the parts with complex shapes in additive manufacturing, combining thermal-structure coupling numerical simulation with a thermal vibration composite stress homogenization experiment, developing different thermal vibration composite process parameters such as vibration frequency, amplitude, vibration excitation position, vibration time, heating temperature, heat preservation time and the like, and researching the influence of stress elimination effect, material mechanical property and microstructure of the high-strength aluminum alloy in additive manufacturing. And (3) finding the optimal thermal vibration composite process parameter combination by taking the optimal stress homogenization effect as a target, and determining a thermal vibration composite stress homogenization process scheme.

Referring to fig. 3, fig. 3 is a schematic structural diagram of a stress field testing system for additive manufacturing of a high-strength aluminum alloy according to an embodiment of the present disclosure. Similar to the principle of the stress field testing method for the additive manufacturing of the high-strength aluminum alloy, the invention provides a stress field testing system for the additive manufacturing of the high-strength aluminum alloy, which includes, but is not limited to, a first measuring module 10, a second measuring module 20, a coating module 30, a heat treatment strengthening module 40 and a combination module 50. The first measurement module 10 is used for measuring the residual stress of the surface layer of the part and removing the material of the surface layer of the part layer by layer to obtain the measured value of the residual stress field. The second measurement module 20 is used to build a finite element model in ANSYS software to measure the residual stress field. The coating module 30 is used for coating a protective layer on the surface of the part. The heat treatment strengthening module 40 is used for performing heat treatment strengthening on the surface of the part to obtain a treated part. The combination module 50 is used for searching the thermal vibration composite process parameter combination for the processed part and determining the thermal vibration composite stress homogenization process scheme.

In conclusion, the stress field testing method for the additive manufacturing of the high-strength aluminum alloy can measure the residual stress on the surface of the material or the internal residual stress of the test piece in the regular shape, and can realize accurate measurement of the internal residual stress field.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.