A device and method for in-situ monitoring of deformation and cracking in metal additive manufacturing process

Abstract

The present invention discloses a device and method for in-situ monitoring of deformation and cracking in a metal additive manufacturing process. The in-situ monitoring device includes an additive manufacturing system, a strain monitoring module, an image monitoring module, and a data processing system. The additive manufacturing system is responsible for forming metal parts; the strain monitoring module is installed under the forming substrate and is responsible for real-time monitoring of in-plane and out-of-plane deformations during the forming process; the image monitoring module is around the energy control system of the additive manufacturing system and can detect deformation on the upper surface of the part; the data processing system processes the data transmitted by the strain monitoring module and the image monitoring module and gives the forming status. While ensuring the accuracy of cracking monitoring, the present invention liberates manual labor and plays a significant role in promoting the advancement of additive manufacturing technology.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal additive manufacturing, and specifically relates to a device and method for in-situ monitoring of deformation and cracking in a metal additive manufacturing process. Background Art

[0002] Metal Additive Manufacturing (MAM) is one of the fastest growing technologies in the field of material processing. It is widely used in aerospace, automotive industry, biomedicine and other fields because of its advantages of reducing material waste, achieving personalized customization, shortening processing time and forming parts with complex geometries.

[0003] Metal additive manufacturing technologies mainly include laser-based powder bed fusion (LPBF) and directed energy deposition (DED). LPBF technology is widely used due to its high precision, but during the forming process, the cyclic heating and cooling of the material leads to a complex thermal stress field, which may cause deformation and cracking of parts. The current multi-laser large-scale LPBF technology faces the problem of complex and difficult-to-regulate stress, and an effective in-situ deformation and cracking monitoring method is urgently needed.

[0004] Existing deformation cracking monitoring methods are divided into contact and non-contact methods. The non-contact method is based on visual monitoring and is suitable for large deformation detection, but it is limited to the surface of the part and it is difficult to identify slight internal cracks. The contact method uses strain gauges and sensors to monitor the forming matrix, but as the forming height increases, the monitoring sensitivity decreases, making it difficult to accurately detect cracks and surface protrusions.

[0005] In addition, for parts with multi-material structures, the differences in thermal expansion coefficients and melting points of different materials can easily cause large deformation or cracking at the interface, leading to forming failure. Currently, most detection devices cannot effectively monitor deformation and cracking in the horizontal direction. Therefore, an accurate and comprehensive monitoring device and method are urgently needed to improve the reliability of the MAM process and the quality of parts. Summary of the invention

[0006] The present invention provides an in-situ monitoring system for deformation and cracking of parts during metal additive manufacturing. The system adheres a strain gauge array to the bottom of a forming substrate, and installs two cameras of a three-dimensional digital image correlation measurement device above a forming cavity. During the additive manufacturing process, the strain gauge array and the camera respectively collect strain data and surface deformation images of the parts, and the two sets of data are compared and analyzed by a data processing module to comprehensively evaluate the forming state of the parts. The system overcomes the shortcomings of the existing single monitoring method, combines the monitoring means of a bidirectional strain gauge array and three-dimensional digital image correlation, realizes real-time and comprehensive monitoring of the deformation behavior of parts, improves the accuracy and reliability of deformation and cracking detection, and ensures the stability of the forming process and the quality of parts.

[0007] To achieve the above object, the present invention provides the following technical solutions.

[0008] A device for in-situ monitoring of deformation and cracking in a metal additive manufacturing process comprises an additive manufacturing system, a strain monitoring module, an image monitoring module and a data processing system 1, wherein:

[0009] The additive manufacturing system is used to form metal parts, including an energy source 6, an energy control system 3, a forming chamber 5, a powder spreading vehicle 7, a powder cylinder 8, a forming cylinder 9, and a powder recovery cylinder 12;

[0010] The strain monitoring module is used to monitor the strain changes generated during the forming process of the metal component, and includes a forming substrate 11, a biaxial strain gauge array 14, a uniaxial strain gauge 15 and a static strain gauge 13;

[0011] The biaxial strain gauge array 14 is used to detect out-of-plane deformation of the formed metal part, wherein the out-of-plane deformation refers to the deformation direction not coinciding with the plane of the formed substrate;

[0012] The uniaxial strain gauge 15 is used to detect the in-plane deformation of the formed component, wherein the in-plane deformation refers to the deformation direction coinciding with the plane of the formed substrate;

[0013] The static strain gauge 13 is used to convert the collected electrical signal into a digital signal of strain data, and transmit the digital strain data to the data processing system 1 through a serial communication interface;

[0014] The image monitoring module is used to monitor the deformation behavior of the laser scanning pattern in the powder bed during the forming process of the metal part, and includes two cameras 2 and two light sources 4;

[0015] The data processing system 1 is used to process the component deformation data measured by the strain monitoring module and the image monitoring module; by performing coupling feature comparison between the component deformation data measured by the strain monitoring module and the image monitoring module and the three-dimensional slice model data of the component and the component design dimension data, the deformation characteristics and strain data of the metal component can be extracted, thereby determining the deformation conditions of various regions of the metal component.

[0016] Further, the energy control system 3 is arranged above the forming cavity 5 and is located directly above the forming cylinder 9;

[0017] The powder spreading vehicle 7 is driven by a motor to spread the powder in the powder cylinder 8 onto the forming cylinder 9 ; the powder cylinder 8 , the forming cylinder 9 , and the powder recovery cylinder 12 are all located below the forming cavity 5 .

[0018] Furthermore, the two light sources 4 are used to illuminate the forming area to increase the brightness of the surface of the formed part, so that the camera 2 can clearly capture the forming data.

[0019] Furthermore, the forming base 11 adopts a non-standard structural design.

[0020] A method for in-situ monitoring of deformation and cracking in a metal additive manufacturing process, characterized in that it comprises the following steps:

[0021] S1: Preparation stage:

[0022] S11. Additive manufacturing system preparation:

[0023] First, a model of a heterogeneous material part is established using 3D design software;

[0024] Subsequently, the model data is sliced ​​and imported into the powder bed fusion equipment to set the corresponding process parameters;

[0025] Finally, add powder material to the additive manufacturing system to complete the preparation of the additive manufacturing system;

[0026] S12. Preparation of strain monitoring module:

[0027] First, use sandpaper to polish the position of the formed metal part where the strain gauge is to be attached, and clean the surface with a cotton ball dipped in alcohol;

[0028] Then, the strain gauge was glued to the polished position using epoxy resin structural adhesive and left to stand for 48 hours;

[0029] After the pasting is completed, the formed metal part with the strain gauge pasted is fixed in the forming cavity of the additive manufacturing system, the forming cavity is sealed, and argon gas is filled to remove the oxygen in the cavity, completing the preparation of the strain monitoring module;

[0030] S13, image monitoring module preparation:

[0031] Firstly, two cameras are installed on both sides of the energy control system above the forming cavity, and the lenses are adjusted to aim at the plane of the formed metal part;

[0032] Then, two light sources were installed next to the camera, and the angles of the light sources were adjusted to ensure that the flat surface of the formed metal part was fully illuminated;

[0033] Finally, the camera takes a picture of the forming plane through the low-frequency thermal mirror window, completing the preparation of the image monitoring module;

[0034] S2: Measurement phase

[0035] S21, additive manufacturing system operation: the additive manufacturing system forms metal parts according to the imported model data;

[0036] S22, strain monitoring module operation:

[0037] First, during the forming process of the additive manufacturing system, the deformation of the metal part is transmitted to the strain gauge under the formed metal part, and is captured by the strain gauge and converted into an electrical signal;

[0038] The static strain gauge then converts the electrical signal into a digital signal and sends the strain data to the data processing system via a serial interface;

[0039] S23, image monitoring module works:

[0040] In the forming process of the additive manufacturing system, when the current layer of the metal part is formed, a circular pattern with a certain density and a diameter of 0.1 mm is first scanned as the speckle pattern required for the camera to shoot;

[0041] Then, the camera takes a picture of the current layer and transmits the captured data to the data processing system;

[0042] S24. Data processing system work:

[0043] First, the data measured by the strain monitoring module and the image monitoring module are transmitted to the data processing system.

[0044] Subsequently, the data processing system preprocesses the received data and compares the preprocessed results;

[0045] The pre-processing comprises:

[0046] (i) Measurement data preprocessing of strain monitoring module:

[0047] After the current layer is formed, for the data detected by the biaxial strain gauge, select the strain gauge with the largest strain value compared with the previous layer, record the maximum strain value, and locate its position in the formed metal part;

[0048] For the data detected by the uniaxial strain gauge: record the difference between the strain value of the current layer and the previous layer. If it exceeds the specified value, it is considered that the metal part is cracked in the horizontal direction and the forming is stopped; if it does not exceed the specified value, compare the pre-processing results;

[0049] (ii) Measurement data preprocessing of image monitoring module:

[0050] After the current layer is formed, the data taken by the two cameras are combined and compared with the data taken by the previous layer to obtain the deformation value of the current layer after forming, and the position with the largest deformation is selected and the maximum deformation value is recorded as the specified value of the image monitoring module.

[0051] The pre-processing results are compared and analyzed to finally obtain the forming state of the metal parts;

[0052] The comparison of the results after the pretreatment specifically includes comparing the position data of the maximum deformation provided by the two groups of pretreatments. When the deviation between the two positions is within 5 mm and the maximum deformation value provided by at least one group of pretreatments exceeds the specified value, the system determines that the metal part has produced a large deformation or cracking in the forming direction, which is regarded as a forming failure and the forming process is terminated; if no cracking occurs, the forming of the next layer is continued until the entire forming process is completed.

[0053] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0054] 1. The in-situ monitoring device for deformation and cracking in the metal additive manufacturing process can obtain the stress and deformation data of parts in the laser powder bed melting process in real time and accurately, reveal the stress distribution law, facilitate the regulation of part deformation, and significantly reduce the time and cost required for offline detection.

[0055] 2. During the powder bed fusion forming process of parts, the in-situ monitoring device for deformation and cracking in the metal additive manufacturing process can simultaneously obtain the deformation data of the surface and interior of the parts through the combination of strain gauge array and three-dimensional digital image correlation monitoring method, comprehensively reflect the deformation state of the parts, and improve the accuracy and reliability of monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 It is a schematic diagram of an in-situ monitoring device for deformation and cracking in a metal additive manufacturing process provided by the present invention;

[0057] Figure 2 It is a schematic diagram of pasting the forming substrate and the strain gauge provided by the present invention;

[0058] Figure 3 is a schematic diagram of the position of the strain gauge array provided by the present invention;

[0059] Figure 4 It is a schematic diagram of speckle distribution of formed parts of different shapes provided by the present invention;

[0060] Figure 5 It is a schematic diagram of the laser speckle formed on the surface of a formed part provided by the present invention;

[0061] Figure 6 This is a schematic diagram of the image monitoring module provided by the present invention detecting deformation of a part;

[0062] Figure 7 It is a schematic flow chart of the in-situ monitoring method for deformation and cracking in the metal additive manufacturing process provided by the present invention;

[0063] Explanation of the numbers in the figure: 1. Data processing system; 2. Camera; 3. Energy control system; 4. Light source; 5. Forming cavity; 6. Energy source; 7. Powder spreading car; 8. Powder cylinder; 9. Forming cylinder; 10. Formed part; 11. Forming substrate; 12. Powder recovery cylinder; 13. Static strain gauge; 14. Biaxial strain gauge array; 15. Uniaxial strain gauge; 16. Protrusion deformation of formed part. DETAILED DESCRIPTION

[0064] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention. Unless otherwise defined, all technical and scientific terms used in this specification have the same meanings as those commonly understood by those skilled in the art of the present invention. The terms used in the description of the present invention in this specification are only for the purpose of describing specific implementation methods and are not used to limit the present invention. The experimental methods in the following embodiments are conventional methods unless otherwise specified.

[0065] like Figures 1 to 7 As shown, an embodiment of the present invention provides a device for in-situ monitoring of deformation and cracking in a metal additive manufacturing process, including an additive manufacturing system, a strain monitoring module, an image monitoring module and a data processing system 1, wherein:

[0066] The additive manufacturing system is used to form metal parts, including an energy source 6, an energy control system 3, a forming chamber 5, a powder spreading vehicle 7, a powder cylinder 8, a forming cylinder 9, and a powder recovery cylinder 12;

[0067] The strain monitoring module is used to monitor the strain changes generated during the forming process of the metal component, and includes a forming substrate 11, a biaxial strain gauge array 14, a uniaxial strain gauge 15 and a static strain gauge 13;

[0068] The biaxial strain gauge array 14 is used to detect out-of-plane deformation of the formed metal part, wherein the out-of-plane deformation refers to the deformation direction not coinciding with the plane of the formed substrate;

[0069] The uniaxial strain gauge 15 is used to detect the in-plane deformation of the formed component, wherein the in-plane deformation refers to the deformation direction coinciding with the plane of the formed substrate;

[0070] The static strain gauge 13 is used to convert the collected electrical signal into a digital signal of strain data, and transmit the digital strain data to the data processing system 1 through a serial communication interface;

[0071] The image monitoring module is used to monitor the deformation behavior of the laser scanning pattern in the powder bed during the forming process of the metal part, and includes two cameras 2 and two light sources 4;

[0072] The data processing system 1 is used to process the component deformation data measured by the strain monitoring module and the image monitoring module; by performing coupling feature comparison between the component deformation data measured by the strain monitoring module and the image monitoring module and the three-dimensional slice model data of the component and the component design dimension data, the deformation characteristics and strain data of the metal component can be extracted, thereby determining the deformation conditions of various regions of the metal component.

[0073] Further, the energy control system 3 is arranged above the forming cavity 5 and is located directly above the forming cylinder 9;

[0074] The powder spreading vehicle 7 is driven by a motor to spread the powder in the powder cylinder 8 onto the forming cylinder 9 ; the powder cylinder 8 , the forming cylinder 9 , and the powder recovery cylinder 12 are all located below the forming cavity 5 .

[0075] Furthermore, the two light sources 4 are used to illuminate the forming area to increase the brightness of the surface of the formed part, so that the camera 2 can clearly capture the forming data.

[0076] Furthermore, the forming base 11 adopts a non-standard structural design.

[0077] like Figure 7 As shown, a method for an in-situ monitoring device for deformation and cracking in a metal additive manufacturing process is characterized by comprising the following steps:

[0078] S1: Preparation stage:

[0079] S11. Additive manufacturing system preparation:

[0080] First, a model of a heterogeneous material part is established using 3D design software;

[0081] Subsequently, the model data is sliced ​​and imported into the powder bed fusion equipment to set the corresponding process parameters;

[0082] Finally, add powder material to the additive manufacturing system to complete the preparation of the additive manufacturing system;

[0083] S12. Preparation of strain monitoring module:

[0084] First, use sandpaper to polish the position of the formed metal part where the strain gauge is to be attached, and clean the surface with a cotton ball dipped in alcohol;

[0085] Then, the strain gauge was glued to the polished position using epoxy resin structural adhesive and left to stand for 48 hours;

[0086] After the pasting is completed, the formed metal part with the strain gauge pasted is fixed in the forming cavity of the additive manufacturing system, the forming cavity is sealed, and argon gas is filled to remove the oxygen in the cavity, completing the preparation of the strain monitoring module;

[0087] S13, image monitoring module preparation:

[0088] Firstly, two cameras are installed on both sides of the energy control system above the forming cavity, and the lenses are adjusted to aim at the plane of the formed metal part;

[0089] Then, two light sources were installed next to the camera, and the angles of the light sources were adjusted to ensure that the flat surface of the formed metal part was fully illuminated;

[0090] Finally, the camera takes a picture of the forming plane through the low-frequency thermal mirror window, completing the preparation of the image monitoring module;

[0091] S2: Measurement phase

[0092] S21, additive manufacturing system operation: the additive manufacturing system forms metal parts according to the imported model data;

[0093] S22, strain monitoring module operation:

[0094] First, during the forming process of the additive manufacturing system, the deformation of the metal part is transmitted to the strain gauge under the formed metal part, and is captured by the strain gauge and converted into an electrical signal;

[0095] The static strain gauge then converts the electrical signal into a digital signal and sends the strain data to the data processing system via a serial interface;

[0096] S23, image monitoring module works:

[0097] In the forming process of the additive manufacturing system, when the current layer of the metal part is formed, a circular pattern with a certain density and a diameter of 0.1 mm is first scanned as the speckle pattern required for the camera to shoot;

[0098] Then, the camera takes a picture of the current layer and transmits the captured data to the data processing system;

[0099] S24. Data processing system work:

[0100] First, the data measured by the strain monitoring module and the image monitoring module are transmitted to the data processing system.

[0101] Subsequently, the data processing system preprocesses the received data and compares the preprocessed results;

[0102] The pre-processing comprises:

[0103] (i) Measurement data preprocessing of strain monitoring module:

[0104] After the current layer is formed, for the data detected by the biaxial strain gauge, select the strain gauge with the largest strain value compared with the previous layer, record the maximum strain value, and locate its position in the formed metal part;

[0105] For the data detected by the uniaxial strain gauge: record the difference between the strain value of the current layer and the previous layer. If it exceeds the specified value, it is considered that the metal part is cracked in the horizontal direction and the forming is stopped; if it does not exceed the specified value, compare the pre-processing results;

[0106] (ii) Measurement data preprocessing of image monitoring module:

[0107] After the current layer is formed, the data taken by the two cameras are combined and compared with the data taken by the previous layer to obtain the deformation value of the current layer after forming, and the position with the largest deformation is selected and the maximum deformation value is recorded as the specified value of the image monitoring module.

[0108] The pre-processing results are compared and analyzed to finally obtain the forming state of the metal parts;

[0109] The comparison of the results after the pretreatment specifically includes comparing the position data of the maximum deformation provided by the two groups of pretreatments. When the deviation between the two positions is within 5 mm and the maximum deformation value provided by at least one group of pretreatments exceeds the specified value, the system determines that the metal part has produced a large deformation or cracking in the forming direction, which is regarded as a forming failure and the forming process is terminated; if no cracking occurs, the forming of the next layer is continued until the entire forming process is completed.

Claims

1. A device for in-situ monitoring of deformation and cracking during metal additive manufacturing, comprising an additive manufacturing system, a strain monitoring module, an image monitoring module and a data processing system (1), characterized in that: The additive manufacturing system is used to form a metal component, comprising an energy source (6), an energy control system (3), a forming chamber (5), a powder spreading vehicle (7), a powder cylinder (8), a forming cylinder (9), and a powder recovery cylinder (12); The strain monitoring module is used to monitor the strain changes generated during the forming process of the metal component, and comprises a forming substrate (11), a biaxial strain gauge array (14), a uniaxial strain gauge (15) and a static strain gauge (13); The biaxial strain gauge array (14) is used to detect out-of-plane deformation of a formed metal component, wherein the out-of-plane deformation refers to a deformation direction that does not coincide with a plane of a formed substrate; The uniaxial strain gauge (15) is used to detect the in-plane deformation of the formed component, wherein the in-plane deformation refers to the deformation direction coinciding with the plane of the formed substrate; The static strain gauge (13) is used to convert the collected electrical signal into a digital signal of strain data, and transmit the digital signal of strain data to the data processing system (1) via a serial communication interface; The image monitoring module is used to monitor the deformation behavior of the laser scanning pattern in the powder bed during the metal component forming process, and includes two cameras (2) and two light sources (4); The data processing system (1) is used to process component deformation data measured by the strain monitoring module and the image monitoring module; by performing coupling feature comparison between the component deformation data measured by the strain monitoring module and the image monitoring module, the three-dimensional slice model data of the component, and the component design dimension data, the deformation characteristics and strain data of the metal component can be extracted, thereby determining the deformation conditions of various regions of the metal component; The forming base (11) adopts a non-standard structural design.

2. The device for in-situ monitoring of deformation and cracking during metal additive manufacturing according to claim 1, characterized in that: The energy control system (3) is arranged above the forming cavity (5) and is located directly above the forming cylinder (9); The powder spreading vehicle (7) is driven by a motor to spread the powder in the powder material cylinder (8) onto the forming cylinder (9); the powder material cylinder (8), the forming cylinder (9) and the powder recovery cylinder (12) are all located below the forming cavity (5).

3. The device for in-situ monitoring of deformation and cracking during metal additive manufacturing according to claim 1, characterized in that: The two light sources (4) are used to illuminate the forming area to increase the brightness of the surface of the formed part, thereby enabling the camera (2) to clearly capture the forming data.

4. The method for in-situ monitoring of deformation and cracking in a metal additive manufacturing process according to claim 1 or 2, characterized in that: The steps include: S1: Preparation stage: S11. Additive manufacturing system preparation: First, a model of a heterogeneous material part is established using 3D design software; Subsequently, the model data is sliced ​​and imported into the powder bed fusion equipment to set the corresponding process parameters; Finally, add powder material to the additive manufacturing system to complete the preparation of the additive manufacturing system; S12. Preparation of strain monitoring module: First, use sandpaper to polish the position of the formed metal part where the strain gauge is to be attached, and clean the surface with a cotton ball dipped in alcohol; Then, the strain gauge was glued to the polished position using epoxy resin structural adhesive and left to stand for 48 hours; After the pasting is completed, the formed metal part with the strain gauge pasted is fixed in the forming cavity of the additive manufacturing system, the forming cavity is sealed, and argon gas is filled to remove the oxygen in the cavity, completing the preparation of the strain monitoring module; S13, image monitoring module preparation: Firstly, two cameras are installed on both sides of the energy control system above the forming cavity, and the lenses are adjusted to aim at the plane of the formed metal part; Then, two light sources were installed next to the camera, and the angles of the light sources were adjusted to ensure that the flat surface of the formed metal part was fully illuminated; Finally, the camera takes a picture of the forming plane through the low-frequency thermal mirror window, completing the preparation of the image monitoring module; S2: Measurement phase: S21, additive manufacturing system operation: the additive manufacturing system forms metal parts according to the imported model data; S22, strain monitoring module operation: First, during the forming process of the additive manufacturing system, the deformation of the metal part is transmitted to the strain gauge under the formed metal part, and is captured by the strain gauge and converted into an electrical signal; The static strain gauge then converts the electrical signal into a digital signal and sends the strain data to the data processing system via a serial interface; S23, image monitoring module works: In the forming process of the additive manufacturing system, when the current layer of the metal part is formed, a circular pattern with a certain density and a diameter of 0.1 mm is first scanned as the speckle pattern required for the camera to shoot; Then, the camera takes a picture of the current layer and transmits the captured data to the data processing system; S24. Data processing system work: First, the data measured by the strain monitoring module and the image monitoring module are transmitted to the data processing system; Subsequently, the data processing system preprocesses the received data and compares the preprocessed results; The pre-processing comprises: (i) Measurement data preprocessing of strain monitoring module: After the current layer is formed, for the data detected by the biaxial strain gauge, select the strain gauge with the largest strain value compared with the previous layer, record the maximum strain value, and locate its position in the formed metal part; For the data detected by the uniaxial strain gauge: record the difference between the strain value of the current layer and the previous layer. If it exceeds the specified value, it is considered that the metal part is cracked in the horizontal direction and the forming is stopped; if it does not exceed the specified value, compare the pre-processing results; (ii) Measurement data preprocessing of image monitoring module: After the current layer is formed, the data captured by the two cameras are combined and compared with the data captured by the previous layer to obtain the deformation value of the current layer after forming, and the position with the largest deformation is selected and the maximum deformation value is recorded as the specified value of the image monitoring module; The pre-processing results are compared and analyzed to finally obtain the forming state of the metal parts; The comparison of the results after the pretreatment specifically includes comparing the position data of the maximum deformation provided by the two groups of pretreatments. When the deviation between the two positions is within 5 mm and the maximum deformation value provided by at least one group of pretreatments exceeds the specified value, the system determines that the metal part has produced a large deformation or cracking in the forming direction, which is regarded as a forming failure and the forming process is terminated; if no cracking occurs, the forming of the next layer is continued until the entire forming process is completed.

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