CN115728244A - Metal additive manufacturing Online detection method and device - Google Patents
Metal additive manufacturing Online detection method and device Download PDFInfo
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Abstract
The invention relates to the technical field of metal additive manufacturing, in particular to a metal additive manufacturing online detection method and device. The method comprises the following steps: printing layer by layer through a material increase process, and testing the material increase material by using a laser ultrasonic technology to obtain ultrasonic data when the preset thickness is printed; wherein the additive material comprises all layers obtained by an additive process; printing layer by layer through a material increase process, and measuring the surface temperature of the material increase material by using an infrared temperature measurement technology every time when a preset thickness is printed to obtain temperature data; determining microstructure distribution data, defect data and residual stress data of the additive material according to the ultrasonic data; and obtaining residual stress correction data according to the temperature data, the microstructure distribution data and the defect data. The invention provides an online detection method and device for metal additive manufacturing, which can simultaneously realize online in-situ detection of residual stress, microstructure and internal defects of a metal additive part and provide data support for optimization and control of a metal additive manufacturing process.
Description
Technical Field
The invention relates to the technical field of metal additive manufacturing, in particular to a metal additive manufacturing online detection method and device.
Background
The metal additive manufacturing is an advanced manufacturing technology of part entities which are accumulated and stacked layer by layer from bottom to top by adopting a high-energy beam heat source such as a high-power-density laser beam, an electric arc, an electron beam and other media to melt metal powder or wire materials on the basis of a digital model, the method has the characteristics of complex forming structure, high forming precision, excellent forming performance and the like, and is one of the most promising manufacturing technologies for one-step integral forming of the current complex and precise metal parts or large-size main bearing metal components.
In the metal additive manufacturing process, the material unbalanced physics and the thermophysical process generated along with the long-term cyclic reciprocating process of the high-power laser beam are very complex, complex interaction can occur among a laser heat source, metal powder, a solid base material and molten pool liquid metal, the metal molten pool is moved to carry out reactions such as rapid solidification under the conditions of laser extraordinary metallurgy, ultrahigh temperature gradient change and strong constraint, the processing process is in an extremely complex environment, residual stress and various typical defects are easily generated in the interior or on the surface of a formed part, and the forming precision and the mechanical property of a metal additive part are reduced. In the metal additive manufacturing process, due to the special printing process, the residual stress of a metal additive manufacturing part is relatively complex, due to the fact that the additive manufacturing process is a layer-by-layer overlapping process, each layer needs to be rapidly heated and cooled, in the heating and solidifying process, due to factors such as thermal expansion and contraction, tensile stress and compressive stress can be generated, so that residual stress fields with different sizes and uneven distribution can appear in a sample, and detection is difficult to perform.
Therefore, in view of the above disadvantages, there is a need for a method and apparatus for simultaneously performing online in-situ detection of residual stress, microstructure and internal defects.
Disclosure of Invention
The embodiment of the invention provides an online detection method and device for metal additive manufacturing, which can simultaneously realize online in-situ detection of residual stress, microstructure and internal defects of a metal additive part and provide data support for optimization and control of a metal additive manufacturing process.
In a first aspect, an embodiment of the present invention provides a method for online detection of metal additive manufacturing, including:
printing layer by layer through a material increase process, and testing the material increase material by using a laser ultrasonic technology to obtain ultrasonic data when the preset thickness is printed; wherein the additive material comprises all layers obtained by the additive process;
printing layer by layer through a material increase process, and measuring the temperature of the material increase material by using an infrared temperature measurement technology every time when a preset thickness is printed to obtain temperature data;
determining microstructure distribution data, defect data and residual stress data of the additive material according to the ultrasonic data;
and obtaining residual stress correction data according to the temperature data, the microstructure distribution data and the defect data.
In one possible design, prior to the determining the microstructure distribution data, the defect data, and the residual stress data of the additive material from the ultrasonic data, comprising:
preparing a calibration test block by the additive process;
measuring a sound velocity-stress mapping relation by using the calibration test block;
the determining microstructure distribution data, defect data, and residual stress data of the additive material from the ultrasonic data includes:
determining the residual stress data according to a sound velocity-stress mapping relation and the sound velocity of the ultrasonic data;
and determining microstructure distribution data and defect data of the additive material according to the ultrasonic data.
In one possible design, the determining the microstructure distribution data and the defect data of the additive material according to the ultrasonic data includes:
reconstructing according to the Rayleigh wave amplitude of the ultrasonic data to obtain a two-dimensional ultrasonic image;
determining position information of the additive material defect according to the two-dimensional ultrasonic image to obtain defect data;
and determining the microstructure distribution of the additive material according to the two-dimensional ultrasonic image to obtain the microstructure distribution data.
In one possible design, after the calibration test block is manufactured through the additive manufacturing process, before the obtaining residual stress correction data according to the temperature data, the microstructure distribution data and the defect data, the method further includes:
measuring a sound velocity-microstructure distribution mapping relation by using the calibration test block;
measuring a sound velocity-temperature mapping relation by using the calibration test block;
obtaining residual stress correction data according to the temperature data, the microstructure distribution data and the defect data, wherein the residual stress correction data comprises the following steps:
obtaining a first sound velocity correction coefficient according to the temperature data and the sound velocity-temperature mapping relation;
obtaining a second sound velocity correction coefficient according to the microscopic data and the sound velocity-microscopic tissue distribution mapping relation;
correcting the ultrasonic data according to the first sound velocity correction coefficient, the second sound velocity correction coefficient and the defect data to obtain ultrasonic sound velocity correction data; and combining the ultrasonic sound velocity correction data and the sound velocity-stress mapping relation to obtain the residual stress correction data.
In a possible design, the measuring the sound velocity-stress mapping relationship by using the calibration test block includes:
and generating tensile stresses with different sizes in the calibration test block by adopting a unidirectional tensile experiment, applying ultrasonic waves to the calibration test block, measuring the sound velocity of Rayleigh waves under different tensile stresses, and establishing the sound velocity-stress mapping relation according to the tensile stress and the sound velocity.
In a possible design, the measuring a sound velocity-microstructure distribution mapping relationship by using the calibration test block includes:
applying ultrasonic waves to the calibration test block, obtaining Rayleigh wave amplitude and Rayleigh wave sound velocity with mapping relation in different areas of the calibration test block, performing two-dimensional imaging according to the difference of the Rayleigh wave amplitude in the different areas to obtain microstructure distribution, and obtaining the sound velocity-microstructure distribution mapping relation by combining the microstructure with the Rayleigh wave sound velocity.
In one possible design, the measuring a sound velocity-temperature mapping relationship by using the calibration test block includes:
and continuously heating the calibration test block, applying ultrasonic waves to the calibration test block, monitoring the Rayleigh sound velocity of the calibration test block at different temperatures in real time, and establishing the sound velocity-temperature mapping relation.
In one possible design, the printing layer by layer through the additive manufacturing process, and when a preset thickness is printed, the additive manufacturing material is tested by using a laser ultrasonic technology to obtain ultrasonic data, including:
and printing layer by layer through an additive process, polishing the additive material every time a preset thickness is printed, and then testing the additive material by using a laser ultrasonic technology to obtain ultrasonic data.
In one possible design, the calibration test block is a zero-stress test block obtained by stress relief annealing.
In a second aspect, an embodiment of the present invention further provides an online detection apparatus for metal additive manufacturing, which is used to implement the method in any one of the above first aspects, and the apparatus includes:
the device comprises a material adding unit, a detection unit and a mobile platform;
the material increase unit comprises a laser emission assembly and a working bin, the laser emission assembly is used for providing laser beams, the working bin comprises a forming cylinder, a powder feeding cylinder and a powder recovery cylinder, the powder feeding cylinder is used for providing powder for the forming cylinder, the forming cylinder is used for forming the powder under the action of laser, and the powder recovery cylinder is used for recovering redundant powder;
the detection unit comprises a detection bin, and an infrared temperature measuring device and a laser ultrasonic detection device which are arranged in the detection bin, wherein the infrared temperature measuring device is used for measuring the temperature of the material increase product, and the laser ultrasonic detection device is used for transmitting and receiving laser to measure the ultrasonic data of the material increase product;
the moving platform is used for bearing the additive manufactured parts to move between the forming cylinder and the detection bin.
Compared with the prior art, the invention at least has the following beneficial effects:
in this embodiment, the laser ultrasonic technology can perform non-contact non-destructive testing, has the advantages of long distance, wide frequency band and high resolution, and can perform non-contact in-situ testing under high temperature conditions. And carrying out laser ultrasonic detection and temperature detection on the additive material every time the preset thickness is printed to obtain a plurality of temperature data and a plurality of ultrasonic data. Processing the ultrasonic data to obtain microstructure distribution data of the additive material defect data and residual stress data. The temperature factor, the microstructure factor and the defect factor affect the precision of the residual stress data, so that the obtained ultrasonic sound velocity data is corrected according to the microstructure distribution data, the defect data and the temperature data to obtain more accurate residual stress correction data.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a flowchart of an online detection method for metal additive manufacturing according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a front view of an online detection device for metal additive manufacturing according to an embodiment of the present invention;
fig. 3 is a schematic top view of an online detection device for metal additive manufacturing according to an embodiment of the present invention;
FIG. 4 is a schematic optical path diagram of a laser ultrasonic online detection system provided in an embodiment of the present invention;
fig. 5 is a waveform characteristic of a laser ultrasonic signal in a thermo-elastic mechanism according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer and more complete, the technical solutions in the embodiments of the present invention will be 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, and based on the embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without creative efforts belong to the scope of the present invention.
In the description of the embodiments of the present invention, unless explicitly specified or limited otherwise, the terms "first", "second", and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance; the term "plurality" means two or more unless specified or indicated otherwise; the terms "connected," "fixed," and the like are to be construed broadly and may, for example, be fixedly connected, detachably connected, integrally connected, or electrically connected; may be directly connected or indirectly connected through an intermediate. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the description of the present invention, it should be understood that the terms "upper" and "lower" as used in the description of the embodiments of the present invention are used in the angle shown in the drawings, and should not be construed as limiting the embodiments of the present invention. In addition, in this context, it will also be understood that when an element is referred to as being "on" or "under" another element, it can be directly on "or" under "the other element or be indirectly on" or "under" the other element via an intermediate element.
The embodiment of the invention provides a metal additive manufacturing online detection method, which comprises the following steps:
printing layer by layer through a material increase process, and testing the material increase material by using a laser ultrasonic technology to obtain ultrasonic data when the preset thickness is printed; wherein, the additive material comprises all layers obtained by an additive process;
printing layer by layer through an additive process, wherein when the preset thickness is printed, measuring the temperature of the additive material by using an infrared temperature measurement technology to obtain temperature data;
determining microstructure distribution data, defect data and residual stress data of the additive material according to the ultrasonic data;
and obtaining residual stress correction data according to the temperature data, the microstructure distribution data and the defect data.
In this embodiment, the laser ultrasonic technique can be used for nondestructive testing, has the advantages of long distance, wide frequency band and high resolution, and can implement non-contact in-situ testing under high temperature conditions. And carrying out laser ultrasonic detection and temperature detection on the additive material every time the preset thickness is printed to obtain a plurality of temperature data and a plurality of ultrasonic data. And carrying out data processing on the ultrasonic data to obtain microstructure distribution data, defect data and residual stress data of the additive material. The temperature factor, the microstructure factor and the defect factor affect the precision of the residual stress data, so that the obtained ultrasonic sound velocity data is corrected according to the microstructure distribution data, the defect data and the temperature data to obtain more accurate residual stress correction data.
It should be noted that, while the laser ultrasonic technology is used for detecting the additive material, the infrared temperature measurement technology is used for measuring the temperature of the additive material. The predetermined thickness may be one layer or a plurality of layers.
In some embodiments of the invention, prior to determining the microstructure distribution data, the defect data, and the residual stress data of the additive material from the ultrasonic data, comprises:
preparing a calibration test block through a material increase process;
measuring the sound velocity-stress mapping relation by using a calibration test block;
determining microstructure distribution data, defect data, and residual stress data of the additive material from the ultrasonic data, comprising:
determining residual stress data according to the sound velocity-stress mapping relation and the sound velocity of the ultrasonic data;
and determining microstructure distribution data and defect data of the additive material according to the ultrasonic data.
In the present embodiment, in order to obtain the residual stress data from the measured ultrasonic data, it is necessary to establish a sound velocity-stress mapping relationship in advance. Specifically, a calibration test block is prepared by adopting an additive process which is the same as the additive material preparation process, and due to the fact that the additive process is the same, the obtained materials are the same, and the sound velocity-stress mapping relation of the two materials is the same. The method comprises the steps of testing a calibration test block to obtain a sound velocity-stress mapping relation between sound velocity and stress, directly applying the obtained sound velocity-stress mapping relation to laser ultrasonic testing of the material additive, and substituting obtained ultrasonic data into the sound velocity-stress mapping relation to obtain residual stress data of the material additive.
In some embodiments of the invention, determining the microstructure distribution data, the defect data, of the additive material from the ultrasonic data comprises:
reconstructing according to the Rayleigh wave amplitude of the ultrasonic data to obtain a two-dimensional ultrasonic image;
determining position information of the additive material defect according to the two-dimensional ultrasonic image to obtain defect data;
and determining the microstructure distribution of the additive material according to the two-dimensional ultrasonic image to obtain microstructure distribution data.
In this embodiment, the ultrasonic data includes an amplitude and a sound velocity of a rayleigh wave, a two-dimensional ultrasonic image is obtained by reconstruction according to a difference between the amplitudes, when an obvious discontinuous distribution region exists in the two-dimensional ultrasonic image, the region is a defect position, and the defect position is obtained by recording the defect position. And determining the microstructure distribution of the additive material according to the two-dimensional ultrasonic image to obtain microstructure distribution data.
In some embodiments of the present invention, after the calibration block is manufactured by an additive process, before obtaining the residual stress correction data according to the temperature data, the microstructure distribution data, and the defect data, the method further includes:
measuring a sound velocity-microstructure distribution mapping relation by using a calibration test block;
measuring a sound velocity-temperature mapping relation by using a calibration test block;
obtaining residual stress correction data according to the temperature data, the microstructure distribution data and the defect data, wherein the residual stress correction data comprises the following steps:
obtaining a first sound velocity correction coefficient according to the temperature data and the sound velocity-temperature mapping relation;
obtaining a second sound velocity correction coefficient according to the microscopic data and the sound velocity-microscopic tissue distribution mapping relation;
correcting the ultrasonic data according to the first sound velocity correction coefficient, the second sound velocity correction coefficient and the defect data to obtain ultrasonic sound velocity correction data; and obtaining residual stress correction data by combining the ultrasonic sound velocity correction data and the sound velocity-stress mapping relation.
In this embodiment, in order to correct the residual stress data, it is necessary to eliminate the influence of the temperature, the microstructure, and the defect position factors on the residual stress. And meanwhile, obtaining a sound velocity-temperature mapping relation and a sound velocity-microstructure distribution mapping relation by testing in advance by using a calibration test block, respectively substituting the measured temperature data and microstructure distribution data of the material additive into the sound velocity-temperature mapping relation and the sound velocity-microstructure distribution mapping relation to obtain the influence of the temperature on the sound velocity and the influence of the microstructure distribution on the sound velocity, namely a first sound velocity correction coefficient and a second sound velocity correction coefficient, correcting the ultrasonic data according to the first sound velocity correction coefficient and the second sound velocity correction coefficient, eliminating the influence of the temperature and the microstructure distribution on the sound velocity to obtain more accurate ultrasonic sound velocity correction data, and combining the ultrasonic sound velocity correction data with the sound velocity-stress mapping relation to obtain more accurate residual stress data. Furthermore, when data are processed, ultrasonic data of the defect position are removed according to the defect data, and the reliability of residual stress measurement is further improved.
In some embodiments of the present invention, the measuring the sound velocity-stress mapping relationship by using the calibration test block includes:
the method comprises the steps of generating tensile stress with different sizes in a calibration test block by adopting a unidirectional tensile experiment, applying ultrasonic waves to the calibration test block, measuring the sound velocity of Rayleigh waves under different tensile stresses, and establishing a sound velocity-stress mapping relation according to the tensile stress and the sound velocity.
In this embodiment, a mapping relationship between a material stress and a rayleigh wave velocity is obtained by performing stress relief annealing on an additive manufacturing member to obtain a zero-stress calibration test block, then tensile stresses of different magnitudes are generated in the zero-stress test block by using a unidirectional tensile experiment, rayleigh wave velocities in various stress states are measured at the same time to obtain a variation relationship between sound velocity variation and stress values, and an acoustic elastic constant is obtained, so that the residual stress magnitude is calculated according to rayleigh wave sound velocity variation. Preparing a tensile sample by using a metal additive product under the same process, performing stress relief annealing, performing laser ultrasonic in-situ detection on the metal additive product under a unidirectional tensile condition, establishing a mapping relation between the stress and the Rayleigh wave velocity, and providing a basis for evaluating the residual stress of the metal additive product by using a Rayleigh wave velocity method subsequently.
In some embodiments of the present invention, the sound velocity-microstructure distribution mapping relationship measured by the calibration test block comprises:
applying ultrasonic waves to the calibration test block, obtaining Rayleigh wave amplitude values and Rayleigh wave sound velocities with mapping relations in different regions of the calibration test block, performing two-dimensional imaging according to the difference of the Rayleigh wave amplitude values of the different regions to obtain microstructure distribution, and combining the Rayleigh wave sound velocities with the microstructure to obtain the sound velocity-microstructure distribution mapping relation.
In this embodiment, the material microstructure evaluation adopts a rayleigh wave amplitude attenuation method, that is, two-dimensional imaging is performed according to the difference of rayleigh wave amplitudes at different regions by using a microstructure at a specific position as a standard, so as to provide the microstructure distribution of the metal additive manufactured part. When the distribution of the microstructures is evaluated, in order to reflect the difference of the microstructures more obviously, the frequency of the ultrasonic rayleigh wave needs to be controlled in a rayleigh scattering area according to the grain size of the material, and meanwhile, the distance between the excitation laser and the receiving laser is properly increased, and the cumulative attenuation effect of the microstructures on the amplitude of the ultrasonic wave is increased. Before the microstructure distribution of the metal additive manufactured piece is obtained, the stress-relief annealing treatment needs to be carried out on the manufactured piece test block, so that on one hand, the influence of material stress on the Rayleigh wave velocity can be eliminated, and simultaneously, the transformation relation of the microstructure on the Rayleigh wave velocity in an unstressed state can be obtained, so that the Rayleigh wave velocity change caused by the microstructure is corrected when the residual stress of the metal additive manufactured piece is measured, and the residual stress measurement precision is improved.
In some embodiments of the present invention, the sound speed-temperature mapping relationship measured by the calibration test block comprises:
and continuously heating the calibration test block, applying ultrasonic waves to the calibration test block, monitoring the Rayleigh acoustic velocity of the calibration test block at different temperatures in real time, and establishing an acoustic velocity-temperature mapping relation.
In this embodiment, the relationship between the rayleigh wave velocity and the change of the material surface temperature, that is, the sound velocity-temperature mapping relationship, is obtained by performing continuous heating treatment on the zero-stress metal additive test block and monitoring the change of the rayleigh wave velocity in real time.
In some embodiments of the present invention, the additive material is printed layer by an additive process, and the laser ultrasonic technology is used to test the additive material to obtain ultrasonic data each time a preset thickness is printed, including:
and printing layer by layer through an additive process, polishing the additive material every time a preset thickness is printed, and then testing the additive material by using a laser ultrasonic technology to obtain ultrasonic data.
In this embodiment, each time a layer of a predetermined thickness is printed, the surface of the newly obtained layer is polished before the laser ultrasonic inspection, so that the scattering of the acoustic wave can be reduced. The laser polishing can be carried out, and the scanning speed and the scanning interval are adjusted according to the laser energy and the spot diameter, so that the surface roughness is below 0.1 mu m.
In some embodiments of the present invention, the calibration block is a zero-stress block obtained by a stress-relief annealing process.
In this embodiment, the stress-relief annealing treatment can eliminate the influence of the material stress on the rayleigh wave velocity, and can also obtain the transformation relationship of the microstructure on the rayleigh wave velocity in an unstressed state, so that the rayleigh wave velocity change caused by the microstructure is corrected when the residual stress of the metal additive part is measured, and the residual stress measurement accuracy is improved.
The embodiment of the invention also provides an online detection device for metal additive manufacturing, which is used for realizing any one of the methods, and the device comprises:
the device comprises a material adding unit, a detection unit and a mobile platform;
the material increase unit comprises a laser emission assembly and a working bin, the laser emission assembly is used for providing laser beams, the working bin comprises a forming cylinder, a powder feeding cylinder and a powder recovery cylinder, the powder feeding cylinder is used for providing powder for the forming cylinder, the forming cylinder is used for forming the powder under the action of laser, and the powder recovery cylinder is used for recovering redundant powder;
the detection unit comprises a detection bin, and an infrared temperature measuring device and a laser ultrasonic detection device which are arranged in the detection bin, wherein the infrared temperature measuring device is used for measuring the temperature of the additive manufactured part, and the laser ultrasonic detection device is used for transmitting and receiving laser to measure ultrasonic data of the additive manufactured part;
the moving platform is used for bearing the additive part to move between the forming cylinder and the detection bin.
The present invention and embodiments will be described in detail by taking the example of additive manufacturing of TC4 titanium alloy parts by molten metal in a metal powder bed. As shown in FIG. 2, the laser power is 0.5kW, the laser scanning speed is 600mm/min, the delivery rate is 10.5g/min, the spot diameter is 2.0mm, and the coverage rate is 60%. Firstly, preparing a metal additive manufacturing part with the thickness of L on a base plate of a forming cylinder, wherein the relation between the thickness of L and the number of scanning layers N of the part and the single-layer scanning thickness d is L = N x d, and after the preparation is finished, performing laser polishing treatment on the surface of the part by using additive manufacturing laser. The laser polishing is carried out in a multi-pass (at least 4 passes) scanning mode, the scanning direction difference between every two passes is 90 degrees, the scanning speed and the scanning interval are adjusted according to the laser energy and the spot diameter, the surface roughness is enabled to be below 0.1 mu m, and meanwhile, the optimal polishing process parameters are determined. The final pass impacts the polished surface under thermoelastic conditions by reducing the laser energy, thereby eliminating as much as possible the additional residual stresses introduced by the polishing process.
After finishing the surface polishing of the part, the part was quickly transferred to an inspection cylinder for residual stress testing and characterization of microstructure and typical defects, as shown in fig. 3. Firstly, an infrared thermal imager finishes measurement of a temperature field on the surface of a workpiece through a detection window, then laser emission and laser receiving are triggered synchronously, ultrasonic signals are generated on the surface of the workpiece in a thermoelastic excitation mode, and the laser ultrasonic signals are received through a double-wave mixed interference method. In the process, in order to improve the signal-to-noise ratio of the ultrasonic signal, the point laser source is shaped into a linear laser source by using a cylindrical mirror, the emitted laser and the received laser are both vertical to the surface of a workpiece, and the distance between the emitted laser and the received laser is adjusted according to the requirements on the detection space resolution and the scanning efficiency. After signal acquisition at a certain position is finished, the three-axis moving platform drives the workpiece to perform stepping scanning motion in an x-y plane, so that acquisition of two-dimensional ultrasonic data is realized. In the process, the coordinates of the ultrasonic signal acquisition position and the temperature data of the detection area at the acquisition time are synchronously stored. And after the ultrasonic signal acquisition on the surface of the workpiece is finished, transferring the workpiece to the original position in the forming cylinder, and continuously finishing the subsequent additive manufacturing process. The thickness of each material increase is controlled in the wave field range of the ultrasonic Rayleigh wave until the whole thickness of the workpiece reaches the designated thickness. In the whole manufacturing and detecting process, the workpiece is always in the protective gas atmosphere, so that the surface oxidation of the workpiece is avoided.
The laser ultrasonic detection system is shown in figure 4. The emitting laser adopts pulse laser with the wavelength of 1064nm, the pulse repetition frequency of 100Hz and continuously adjustable energy, and a circular point light laser source is focused into a linear laser source through a cylindrical mirror. The pulse laser irradiates the designated position of the sample piece to be detected through the dichroic mirror. Meanwhile, the detection laser adopts continuous laser with the wavelength of 532nm, the continuous laser is transmitted to the collimating mirror through the optical fiber to be subjected to beam collimation, and then the continuous laser is divided into a reference beam and a detection beam through the polarization beam splitter. The reference light beam is reflected to the surface of the photoelectric detector by the reflector, and the detection light beam is reflected by the dichroic mirror and then irradiates the surface of the sample piece to be detected. The probe beam is reflected to the photoelectric detector according to the light path in fig. 4 after being reflected by the surface of the sample piece, and is subjected to stable interference with the reference beam, and the laser interference pattern is converted into an analog voltage signal through the photoelectric detector and is stored in the oscilloscope. And part of the emitted laser received by the photoelectric detector is used as a synchronous trigger signal between the emitting laser and the detecting laser, so that the ultrasonic excitation and the receiving are synchronous. The continuous adjustment of the distance between the emitted laser and the received laser is realized by adjusting the angle of a reflector in the light path of the emitted laser.
In order to realize the synchronization of the additive manufacturing process and the online quality monitoring process and ensure the reliability of the monitoring result, the equipment system working flow shown in fig. 1 is specially designed. The forming cylinder is mainly used for completing preparation of metal additive products and surface polishing treatment of the metal additive products, the process can reduce preparation efficiency reduction caused by surface polishing to the maximum extent, and the polishing treatment is also beneficial to reducing formation of various defects in the metal additive products. The detection cylinder is mainly used for completing surface temperature monitoring and laser ultrasonic detection of metal additive parts. Wherein, the surface temperature monitoring is synchronously carried out in the process of exciting and receiving the ultrasonic signals.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, and not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A method for metal additive manufacturing online detection is characterized by comprising the following steps:
printing layer by layer through a material increase process, and testing the material increase material by using a laser ultrasonic technology to obtain ultrasonic data when the preset thickness is printed; wherein the additive material comprises all layers resulting from the additive process;
printing layer by layer through a material increase process, and measuring the temperature of the material increase material by using an infrared temperature measurement technology every time when a preset thickness is printed to obtain temperature data;
determining microstructure distribution data, defect data and residual stress data of the additive material according to the ultrasonic data;
and obtaining residual stress correction data according to the temperature data, the microstructure distribution data and the defect data.
2. The method of claim 1, prior to said determining microstructure distribution data, defect data, and residual stress data of the additive material from the ultrasonic data, comprising:
preparing a calibration test block by the additive process;
measuring a sound velocity-stress mapping relation by using the calibration test block;
the determining microstructure distribution data, defect data, and residual stress data of the additive material from the ultrasonic data includes:
determining the residual stress data according to a sound velocity-stress mapping relation and the sound velocity of the ultrasonic data;
and determining microstructure distribution data and defect data of the additive material according to the ultrasonic data.
3. The method of claim 2, wherein the determining microstructure distribution data, defect data, of the additive material from the ultrasonic data comprises:
reconstructing according to the Rayleigh wave amplitude of the ultrasonic data to obtain a two-dimensional ultrasonic image;
determining position information of the additive material defect according to the two-dimensional ultrasonic image to obtain defect data;
and determining the microstructure distribution of the additive material according to the two-dimensional ultrasonic image to obtain the microstructure distribution data.
4. The method of claim 3, wherein after said preparing a calibration block by said additive process, before said obtaining residual stress modification data from said temperature data, microstructure distribution data, and defect data, further comprises:
measuring a sound velocity-microstructure distribution mapping relation by using the calibration test block;
measuring a sound velocity-temperature mapping relation by using the calibration test block;
obtaining residual stress correction data according to the temperature data, the microstructure distribution data and the defect data, wherein the residual stress correction data comprises the following steps:
obtaining a first sound velocity correction coefficient according to the temperature data and the sound velocity-temperature mapping relation;
obtaining a second sound velocity correction coefficient according to the microscopic data and the sound velocity-microscopic tissue distribution mapping relation;
correcting the ultrasonic data according to the first sound velocity correction coefficient, the second sound velocity correction coefficient and the defect data to obtain ultrasonic sound velocity correction data; and combining the ultrasonic sound velocity correction data and the sound velocity-stress mapping relation to obtain the residual stress correction data.
5. The method of claim 2, wherein the measuring the sound velocity-stress mapping relationship using the calibration test block comprises:
and generating tensile stresses with different sizes in the calibration test block by adopting a unidirectional tensile experiment, applying ultrasonic waves to the calibration test block, measuring the sound velocity of Rayleigh waves under different tensile stresses, and establishing the sound velocity-stress mapping relation according to the tensile stress and the sound velocity.
6. The method of claim 4, wherein the measuring the sound velocity-microstructure distribution mapping relationship by using the calibration test block comprises:
applying ultrasonic waves to the calibration test block, obtaining Rayleigh wave amplitude values and Rayleigh wave sound velocities which have a mapping relation in different areas of the calibration test block, performing two-dimensional imaging according to the difference of the Rayleigh wave amplitude values in the different areas to obtain microstructure distribution, and combining the microstructure with the Rayleigh wave sound velocities to obtain the sound velocity-microstructure distribution mapping relation.
7. The method of claim 4, wherein the measuring a sound speed-temperature mapping relationship using the calibration test block comprises:
and continuously heating the calibration test block, applying ultrasonic waves to the calibration test block, monitoring the Rayleigh sound velocity of the calibration test block at different temperatures in real time, and establishing the sound velocity-temperature mapping relation.
8. The method of claim 1, wherein the additive material is printed layer by an additive process, and the testing of the additive material using a laser ultrasonic technique to obtain ultrasonic data comprises, for each predetermined thickness printed,:
the method comprises the steps of printing layer by layer through an additive process, polishing the additive material when the preset thickness is printed, and testing the additive material by using a laser ultrasonic technology to obtain ultrasonic data.
9. The method of claim 2, wherein the calibration test block is a zero-stress test block obtained by a stress-relief annealing process.
10. A metal additive manufacturing online detection device for implementing the method of any one of claims 1-9, the device comprising:
the device comprises a material adding unit, a detection unit and a mobile platform;
the material adding unit comprises a laser emitting assembly and a working bin, the laser emitting assembly is used for providing laser beams, the working bin comprises a forming cylinder, a powder feeding cylinder and a powder recycling cylinder, the powder feeding cylinder is used for providing powder for the forming cylinder, the forming cylinder is used for forming the powder under the action of laser, and the powder recycling cylinder is used for recycling redundant powder;
the detection unit comprises a detection bin, and an infrared temperature measuring device and a laser ultrasonic detection device which are arranged in the detection bin, wherein the infrared temperature measuring device is used for measuring the temperature of the material increase product, and the laser ultrasonic detection device is used for transmitting and receiving laser to measure the ultrasonic data of the material increase product;
the moving platform is used for bearing the additive parts to move between the forming cylinder and the detection bin.
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