An eddy current testing simulation analysis method for defect detection of metal additive manufacturing parts

Abstract

This invention discloses an eddy current testing simulation analysis method for defect detection in titanium alloy additive manufacturing parts, belonging to the field of eddy current nondestructive testing technology. The method uses ANSYS Maxwell electromagnetic simulation software to perform finite element analysis on a three-dimensional model. By changing the excitation frequency of the detection coil, the lift-off amount, and the depth, width, and length of the surface defects on the test block, changes in electromagnetic field strength and eddy current density are obtained, forming an eddy current testing simulation analysis method for defect detection in titanium alloy additive manufacturing parts. This invention uses eddy current testing without a coupling agent, enabling non-contact measurement with high sensitivity, and is suitable for nondestructive testing of microcracks, lack of fusion, and porosity defects that are prone to occur in metal additive manufacturing. This invention combines eddy current testing with finite element analysis to study the influence mechanism of part defect characteristics and detection parameters on electromagnetic field properties, laying the foundation for research on nondestructive testing of other additive manufacturing parts.

Description

Technical Field

[0001] This invention relates to the field of eddy current nondestructive testing technology, specifically to an eddy current testing simulation analysis method for defect detection of metal additive manufacturing parts. Background Technology

[0002] Metal additive manufacturing is an advanced manufacturing technology that uses three-dimensional digital models of components as a heat source to melt and deposit metal base materials layer by layer to form solid components. This point-line-surface integrated processing method gives it unique advantages in manufacturing complex-shaped components, reducing mold design and development, shortening product development cycles, and improving material utilization. Therefore, additive manufacturing technology is widely used in aerospace, automotive, medical, and military industries.

[0003] However, the generation and propagation of certain defects are unavoidable during the preparation and use of additive manufacturing products. Furthermore, electronic or laser additive manufacturing is a multi-field physical coupling process, with various unstable factors present during the forming process. Temperature changes are drastic, and the melting, solidification, and cooling of materials occur under extremely rapid conditions. Under stress, formed parts are prone to macroscopic defects such as warping, cracking, and dimensional abnormalities. Simultaneously, unpredictable metallurgical defects such as cracks, porosity, lack of fusion, and inclusions can easily occur internally. Therefore, non-destructive testing (NDT), as a non-destructive inspection method, plays a crucial role in quality control of additive manufacturing products, adjusting additive manufacturing processes, and improving the overall performance of additive manufacturing parts, becoming a significant driving force for the widespread application of additive manufacturing technology in the manufacturing sector.

[0004] Current non-destructive testing (NDT) methods mainly include ultrasonic testing, radiographic testing, penetrant testing, and eddy current testing. Ultrasonic testing requires a coupling agent, which contaminates the sample and makes it difficult to identify the nature and type of defects. Radiographic testing is expensive, complex, inconvenient, harmful to humans, and costly. Penetrant testing is difficult to detect internal defects, and the thickness of the tested parts is usually no more than 10 mm, making these methods unsuitable for testing laser melting deposition specimens. Eddy current NDT does not require a coupling agent, allows for non-contact measurement, has a simple process and low cost, high sensitivity to microcracks and pores, fast detection of surface and near-surface defects, high sensitivity, and provides immediate results. It can also inspect conductors with complex shapes and sizes. Therefore, this invention selects the eddy current NDT method. Because the current standards for NDT in metal additive manufacturing parts have not yet formed a scientific and systematic framework, establishing and further improving NDT method standards is a key development direction for this field in the future.

[0005] Due to the influence of the skin effect and lift-off effect on the magnetic field and eddy current distribution in eddy current nondestructive testing, it is difficult to determine the variation law of the magnetic field inside the test block. Therefore, a simulation analysis method for eddy current nondestructive testing of defects in metal additive manufacturing parts based on ANSYS Maxwell software is proposed. Summary of the Invention

[0006] In response to the needs of the field of non-destructive testing of metal additive manufacturing parts, the purpose of this invention is to provide an eddy current testing simulation analysis method for defect detection of metal additive manufacturing parts, so as to provide a non-destructive testing solution for metal additive manufacturing parts.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] An eddy current detection simulation analysis method for defect detection of metal additive manufacturing parts, the method includes the following steps S1-S3:

[0009] S1: Preprocessing; including the following steps (1)-(5):

[0010] (1) Geometric modeling:

[0011] The electromagnetic field distribution throughout the entire space for defect eddy current testing is non-axisymmetric. Therefore, 3D modeling should be selected before modeling, and the solver mode should be set to Eddy current. The coordinate system should be Cartesian, and the length unit should be mm. To improve simulation efficiency, since the geometry of the additively formed parts and defects in the model is relatively simple, the built-in function of the software can be used to draw cuboid blocks directly. The structure of the coil used for eddy current testing is relatively complex. In the finite element analysis, it is simplified to a hollow cylinder and the difference in electromagnetic field distribution inside the conductor and between turns is ignored. The size of the block in the model is 30×30×18mm, the inner diameter of the coil is 0.5mm, the outer diameter is 2.5mm, and the defect size is 0.5×5×1mm.

[0012] (2) Material definition:

[0013] Add the Ti-6Al-4V material parameters to the material library; its conductivity is 5.68 × 10⁻⁶. 5 s / m; The coil is a copper coil with a relative permeability of 1; Since the magnetic reluctance of metal is much greater than that of air, the defect material is set to air;

[0014] (3) Loading of excitation sources:

[0015] ANSYS Maxwell 3D excitation source loading supports current sources and current density sources; since the coil in the model of step (1) is simplified to a hollow cylinder, it is necessary to convert the current in a single-turn coil into the current in the rectangular cross section of the entire coil and load a current source on the cross section. When an alternating current is applied, the skin effect inside the metal will cause the current to concentrate on the surface. If there are defects on the surface, the magnetic field distribution on the surface will have a significant change at the crack.

[0016] (4) Boundary settings:

[0017] The proper setting of boundary conditions in finite element simulation is the main factor to ensure the accuracy of the solution results. Since the coil size is small in laser melting deposition eddy current detection, the boundary conditions on the variable cross section of the medium inside the field can be set as natural boundary conditions, and the computational domain can be ensured to cover the propagation range of the coil magnetic field in the vacuum domain. In this paper, this range is 50 times the outer diameter of the coil.

[0018] (5) Mesh generation:

[0019] Due to the skin effect, the eddy current field distribution along the depth direction of the additively formed part in the laser melting deposition eddy current inspection process is limited. Therefore, when meshing the additively formed part, it is necessary to refine the mesh on the inspection surface to ensure calculation accuracy, while a sparser mesh can be used in deeper areas to reduce calculation time. Mesh generation can be selected based on the adaptive meshing of the element edge length. The software will automatically refine the mesh during calculation according to the set maximum edge length value, and the depth of the skin effect is calculated. Finally, parameters such as the maximum number of convergence steps, convergence error, percentage of the automatically refined mesh to the previous generation, minimum number of calculation steps, and frequency of the excitation source are set in the solver to complete the mesh generation settings.

[0020] S2: Parameter settings:

[0021] Before simulation, parameters such as convergence step number, simulation step size, and fault tolerance percentage are set. After setting the excitation source and boundary conditions, the solution options are set. Then, simulations are performed at different excitation frequencies of 500kHz, 450kHz, 400kHz, and 300kHz. The results are then calculated to obtain the magnetic flux density vector diagram and magnetic flux density distribution diagram of the model. Three grooves with a width of 1mm, a length of 18mm, and a depth of 0.5mm, 1mm, and 1.5mm are made on the surface of the test block to simulate surface microcracks of different depths. Three grooves with a depth of 1mm, a length of 18mm, and a width of 0.3mm, 0.4mm, and 0.5mm are also made on the surface of the test block to simulate surface microcracks of different widths.

[0022] S3: Post-processing:

[0023] After the simulation calculation is completed, the calculation results of eddy current density distribution, magnetic field strength distribution, magnetic field lines, and magnetic induction intensity can be obtained. The results show the influence of different excitation frequencies, lift-off amounts, and the length, width, and depth of defects on the magnetic induction intensity.

[0024] Preferably, the main analysis area in S1 is the surface defects of the test block and the near-surface area of ​​the test block. The number of coil grids is 1000, the number of air domain grids is 2500, the number of test block surface grids is 1000, and the total number of air domains is 3000.

[0025] Preferably, in S1, the excitation coil has 200 turns, an initial phase angle of 0°, an effective current of 400*1.414A, is a stranded coil, and the excitation source frequency is set to 5000Hz. Only the eddy current effect of the test block is considered, and the effect within the coil is not considered.

[0026] Preferably, a magnetic chip is located below the transmitting coil in S1 to detect the magnetic field at the current position. When the probe moves across the pipe surface, it detects changes in the magnetic field distribution. This change allows the determination of the defect location and size. Only a simplified model was created during modeling; in reality, it contains many insulating components, external circuit components, and other insulating elements, all of which are represented here by this basic structural principle.

[0027] Preferably, in step S2, the lift-off amount is 1 mm, and the magnetic field change at a position 0.1 mm below the probe and 0.1 mm from the surface of the test block is detected; the current flowing through the coil is 5000 Hz, the period is 0.3 milliseconds, and the probe movement speed, compared with the frequency, does not cause a coupling effect. The magnetic field at each position is not affected by the coil movement speed, thus establishing a parameterized scan of the coil position.

[0028] The advantages and beneficial effects of this invention are as follows:

[0029] This invention utilizes ANSYS Maxwell to establish an electromagnetic field numerical simulation model of a metal additive test block-probe, and performs simulation analysis on the induced magnetic field of the test block under different excitation frequencies, lift-off amounts, defect widths, and defect depths. When the coil moves from -1mm to 1mm, the voltage amplitude of the detection coil is at its maximum, which is reflected in the graph as a double peak. When the center of the defect coincides with the center of the detection coil, a trough forms between the double peaks. The variation of the magnetic field inside the test block under different excitation frequencies shows that as the excitation frequency decreases from 500kHz, 450kHz, 400kHz to 300kHz, the electromagnetic field strength gradually decreases, the eddy current density decreases, and the magnetic field penetration becomes easier. As the lift-off amount increases from 1mm to 4mm, the electromagnetic field strength gradually decreases, mainly because as the lift-off amount increases, the eddy current density at the defect continuously decreases, leading to a continuous reduction in the interference of the defect on the eddy current field. As the defect depth increases from 0.5mm, 1mm to 1.5mm, the electromagnetic field strength gradually increases, the eddy current density continuously increases, and the peak amplitude of the induced electromotive force of the detection coil shows a monotonically increasing trend with the defect depth. As the defect width increases from 0.3mm, 0.4mm to 0.5mm, the electromagnetic field strength gradually increases, the eddy current density continuously increases, and the peak value of the magnetic field strength of the detection coil increases slowly, indicating that at the same depth, small changes in width have little impact on the signal. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the simulation process of the present invention.

[0031] Figure 2 This is a 3D model diagram of the detection probe-metal additive test block of the present invention.

[0032] Figure 3 This is a diagram showing the distribution of the eddy current and magnetic flux B vector on the XZ interface according to the present invention.

[0033] Figure 4 This diagram illustrates the effect of different excitation frequencies on the magnetic field strength according to the present invention.

[0034] Figure 5 This diagram illustrates the effect of different lift-off amounts on the magnetic field strength according to the present invention.

[0035] Figure 6 This diagram illustrates the effect of different defect depths on the magnetic field strength according to the present invention.

[0036] Figure 7 This diagram illustrates the effect of defect width on magnetic field strength according to the present invention. Detailed Implementation

[0037] To further understand the present invention, the present invention is described below with reference to examples. However, the examples are only for further illustrating the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention.

[0038] Example 1:

[0039] This embodiment provides a simulation analysis method for eddy current detection of defects in titanium alloy additive manufacturing parts. The process is as follows: Figure 1 Specifically, it includes the following steps S1-S3:

[0040] S1: Preprocessing, including the following steps (1)-(5):

[0041] (1) Geometric modeling:

[0042] The electromagnetic field distribution throughout the entire space for defect eddy current testing is non-axisymmetric. Therefore, 3D modeling should be selected before modeling, and the solver mode should be set to Eddy current. The coordinate system should be Cartesian, and the length unit should be mm. To improve simulation efficiency, since the geometry of the additively formed part and its defects in the model is relatively simple, the built-in function of the software can be used to draw a cuboid block. The structure of the coil used for eddy current testing is relatively complex. In the finite element analysis, it is simplified to a hollow cylinder, and the difference in electromagnetic field distribution inside the conductor and between turns is ignored. The size of the block in the model is 30×30×18mm, the inner diameter of the coil is 0.5mm, the outer diameter is 2.5mm, and the defect size is 0.5*5*1mm. Figure 2 ).

[0043] (2) Material definition:

[0044] Add the Ti-6Al-4V material parameters to the material library; its conductivity is 5.68 × 10⁻⁶. 5 s / m; The coil is a copper coil with a relative permeability of 1; Since the magnetic reluctance of metal is much greater than that of air, the defect material is set to air.

[0045] (3) Loading of excitation sources:

[0046] ANSYS Maxwell 3D excitation source loading supports current sources and current density sources. Since the coil in the model of step (1) is simplified to a hollow cylinder, it is necessary to convert the current in a single-turn coil into the current in the rectangular cross-section of the entire coil and load a current source on the cross-section. When an alternating current is applied, the skin effect inside the metal will cause the current to concentrate on the surface. If there are defects on the surface, the magnetic field distribution on the surface will change significantly at the crack.

[0047] (4) Boundary settings:

[0048] In finite element simulation, the proper setting of boundary conditions is a key factor in ensuring accurate solution results. Since the coil size is relatively small in laser melting deposition eddy current detection, the boundary conditions on the variable cross-section of the medium within the field can be set as natural boundary conditions. It is also important to ensure that the computational domain covers the propagation range of the coil's magnetic field in the vacuum domain; in this example, this range is 50 times the outer diameter of the coil.

[0049] (5) Mesh generation:

[0050] Due to the skin effect, the eddy current field distribution along the depth direction of the additively formed part is limited in the laser melting deposition eddy current inspection process. Therefore, when meshing the additively formed part, it is necessary to refine the mesh on the inspection surface to ensure calculation accuracy, while a sparser mesh can be used in deeper regions to reduce calculation time. Mesh generation can be selected based on adaptive meshing directly according to the element edge length. The software will automatically refine the mesh during calculation according to the set maximum edge length value, and the depth of the skin effect is calculated. Finally, parameters such as the maximum number of convergence steps, convergence error, percentage of automatically refined meshes relative to the previous generation, minimum number of calculation steps, and excitation source frequency are set in the solver to complete the mesh generation settings.

[0051] S2: Parameter Settings: Before simulation, set parameters such as convergence step number, simulation step size, and fault tolerance percentage. After setting the excitation source and boundary conditions, set the solution options. Then, perform simulations at different excitation frequencies of 500kHz, 450kHz, 400kHz, and 300kHz, and solve the model to obtain the magnetic flux density vector diagram and magnetic flux density distribution diagram. Make three grooves on the surface of the test block with a width of 1mm, a length of 18mm, and a depth of 0.5mm, 1mm, and 1.5mm to simulate surface microcracks of different depths. Make three grooves on the surface of the test block with a depth of 1mm, a length of 18mm, and a width of 0.3mm, 0.4mm, and 0.5mm to simulate surface microcracks of different widths.

[0052] S3: Post-processing: After the simulation calculation is completed, the calculation results of eddy current density distribution, magnetic field strength distribution, magnetic field lines, and magnetic induction intensity can be obtained. The results show the influence of different excitation frequencies, lift-off amounts, and the length, width, and depth of defects on the magnetic induction intensity. Figure 3-7 ).

[0053] The main analysis area in S1 is the surface defects of the test block and the near-surface area of ​​the test block. The number of coil grids is 1000, the number of air domain grids is 2500, the number of test block surface grids is 1000, and the total number of air domains is 3000.

[0054] In S1, the selected coil has 200 turns, the initial phase angle is 0°, the effective current is 400*1.414A, the type is selected as stranded coil, and the excitation source frequency is set to 5000Hz. Figure 4Only the eddy current effect of the test block is considered, and the effect inside the coil is not considered.

[0055] Below the transmitting coil in S1 is a magnetic chip used to detect the magnetic field at the current position. As the probe moves across the pipe surface, it detects changes in the magnetic field distribution. This change allows the determination of the defect location and size. Only a simplified model was created; in reality, it includes many insulating components, external circuit elements, and other insulating parts, all of which are represented here by this basic structural principle.

[0056] In S2, the lift-off distance is 1 mm, and the change in magnetic field at a position 0.1 mm directly below the probe and at a distance of 0.1 mm from the surface of the test block is detected. The current flowing through the coil is 5000 Hz, with a period of 0.3 milliseconds. The probe movement speed, compared to the frequency, does not cause a coupling effect, and the magnetic field at each position is unaffected by the coil movement speed, thus establishing a parametric scan of the coil position.

Claims

1. A simulation analysis method for eddy current detection of defects in metal additive manufacturing parts, characterized in that: The method includes the following steps S1-S3: S1: Preprocessing; Includes the following steps (1)-(5): (1) Geometric modeling: The electromagnetic field distribution throughout the entire space for defect eddy current testing is non-axisymmetric. Therefore, 3D modeling should be selected before modeling, and the solver mode should be set to Eddy current. The coordinate system should be Cartesian, and the length unit should be mm. To improve simulation efficiency, since the geometry of the additively formed parts and defects in the model is relatively simple, the built-in function of the software can be used to draw cuboid blocks directly. The structure of the coil used for eddy current testing is relatively complex. In the finite element analysis, it is simplified to a hollow cylinder and the difference in electromagnetic field distribution inside the conductor and between turns is ignored. The size of the block in the model is 30×30×18mm, the inner diameter of the coil is 0.5mm, the outer diameter is 2.5mm, and the defect size is 0.5×5×1mm. (2) Material definition: Add the Ti-6Al-4V material parameters to the material library; its conductivity is 5.68 × 10⁻⁶. 5 s / m; The coil is made of copper with a relative permeability of 1; since the magnetic reluctance of metal is much greater than that of air, the defect material is set to air. (3) Loading of excitation sources: ANSYS Maxwell 3D excitation source loading supports current source and current density source; since the coil in the model of step (1) is simplified to a hollow cylinder, it is necessary to convert the current in a single-turn coil into the current in the rectangular cross section of the entire coil and load a current source on the cross section; since when an alternating current is applied, the current will be concentrated on the surface due to the skin effect inside the metal, and there are defects on the surface, and the magnetic field distribution on the surface will have an obvious change at the crack. (4) Boundary settings: The proper setting of boundary conditions in finite element simulation is the main factor to ensure the accuracy of the solution results. Since the coil size is small in laser melting deposition eddy current detection, the boundary conditions on the variable cross section of the medium inside the field can be set as natural boundary conditions, and the computational domain can be ensured to cover the propagation range of the coil magnetic field in the vacuum domain. In this paper, this range is 50 times the outer diameter of the coil. (5) Mesh generation: Due to the skin effect, the eddy current field distribution along the depth direction of the additively formed part in the laser melting deposition eddy current inspection process is limited. Therefore, when meshing the additively formed part, it is necessary to refine the mesh on the inspection surface to ensure calculation accuracy, while a sparser mesh can be used in deeper areas to reduce calculation time. Mesh generation can be selected based on the adaptive meshing of the element edge length. The software will automatically refine the mesh during calculation according to the set maximum edge length value, and the depth of the skin effect is calculated. Finally, parameters such as the maximum number of convergence steps, convergence error, percentage of the automatically refined mesh to the previous generation, minimum number of calculation steps, and frequency of the excitation source are set in the solver to complete the mesh generation settings. S2: Parameter settings: Before simulation, parameters such as convergence step number, simulation step size, and fault tolerance percentage are set. After setting the excitation source and boundary conditions, the solution options are set. Then, simulations are performed at different excitation frequencies of 500kHz, 450kHz, 400kHz, and 300kHz. The results are then calculated to obtain the magnetic flux density vector diagram and magnetic flux density distribution diagram of the model. Three grooves with a width of 1mm, a length of 18mm, and a depth of 0.5mm, 1mm, and 1.5mm are made on the surface of the test block to simulate surface microcracks of different depths. Three grooves with a depth of 1mm, a length of 18mm, and a width of 0.3mm, 0.4mm, and 0.5mm are also made on the surface of the test block to simulate surface microcracks of different widths. S3: Post-processing: After the simulation calculation is completed, the calculation results of eddy current density distribution, magnetic field strength distribution, magnetic field lines, and magnetic induction intensity can be obtained. The results show the influence of different excitation frequencies, lift-off amounts, and the length, width, and depth of defects on the magnetic induction intensity.

2. The eddy current detection simulation analysis method for defect detection of metal additive manufacturing parts according to claim 1, characterized in that: In S1, the main analysis area is the surface defects of the test block and the near-surface area of ​​the test block; the number of coil grids is 1000, the number of air domain grids is 2500, the number of test block surface grids is 1000, and the total number of air domains is 3000.

3. The eddy current detection simulation analysis method for defect detection of metal additive manufacturing parts according to claim 1, characterized in that: In S1, the excitation coil has 200 turns, the initial phase angle is 0°, the effective value of the applied current is 400*1.414A, the type is selected as stranded coil, and the excitation source frequency is set to 5000HZ; only the eddy current effect of the test block is considered, and the effect inside the coil is not considered.

4. The eddy current detection simulation analysis method for defect detection of metal additive manufacturing parts according to claim 2, characterized in that: In S1, there is a magnetic chip below the transmitting coil to detect the magnetic field at the current position. When the probe moves on the surface of the pipe, it will detect the change in the magnetic field distribution. Through this change, the location and size of the defect can be determined. Only a simplified model was made during modeling. In reality, there are many insulating components, external circuit components, insulating components, etc., which are all replaced by this principle structure here.

5. The eddy current detection simulation analysis method for defect detection of metal additive manufacturing parts according to claim 2, characterized in that: In S2, the lift-off amount is 1mm, and the magnetic field change at a position 0.1mm below the probe and 0.1mm from the surface of the test block is detected. The current flowing through the coil is 5000HZ, the period is 0.3 milliseconds, and the probe movement speed does not cause coupling effect compared with the frequency. The magnetic field at each position is not affected by the coil movement speed, thus establishing a parameterized scan of the coil position.

Images