NL2026239A - method for analyzing mechanical properties of 3D printing sample with different construction orientations - Google Patents
method for analyzing mechanical properties of 3D printing sample with different construction orientations Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/02—Details
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/02—Details
- G01N3/06—Special adaptations of indicating or recording means
- G01N3/068—Special adaptations of indicating or recording means with optical indicating or recording means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/20—Investigating strength properties of solid materials by application of mechanical stress by applying steady bending forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
- G01N2203/0016—Tensile or compressive
- G01N2203/0017—Tensile
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0058—Kind of property studied
- G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
- G01N2203/0075—Strain-stress relations or elastic constants
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/026—Specifications of the specimen
- G01N2203/0262—Shape of the specimen
- G01N2203/0268—Dumb-bell specimens
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/0641—Indicating or recording means; Sensing means using optical, X-ray, ultraviolet, infrared or similar detectors
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Abstract
The invention discloses a method for analyzing the mechanical properties of 3D printing samples with different construction orientations, comprising the following steps: fabricating multiple sample strips with different construction orientations by 3D printing; and forming speckles on a surface of the sample strip; placing the sample strip on a loading device, and debugging the loading device; performing a mechanical property test; and capturing images of the sample strip throughout the test; comparing and analyzing the images of the sample strip before and after deformation by using a digital image correlation method to obtain displacement and strain information; obtaining a stress-strain curve according to the strain information; and obtaining property parameters of the sample strip; repeating the above steps to complete the mechanical property test of the multiple sample strips with different construction orientations; and analyzing the differences in the mechanical properties of the sample strips with different construction orientations.
Description
METHOD FOR ANALYZING MECHANICAL PROPERTIES OF 3D
ORIENTATIONS Field of the Invention The present invention belongs to the field of mechanical property test technology in the additive manufacturing industry, and specifically relates to a method for analyzing the mechanical properties of 3D printing samples with different construction orientations.
Background of the Invention The statement here merely provides the background art related to the present invention, and does not necessarily constitute the prior art. Mechanical property measurement methods are divided into electrical measurement methods and optical measurement methods in principle. The electrical measurement methods include resistance strain gauges, capacitive strain gauges, etc. The electrical measurement methods have been widely used in laboratories due to their advantages of simple operation and the like. However, the electrical measurement methods are contact measurement methods, are restricted by test conditions in many complex situations (such as high temperature, low temperature or magnetic field), and often cannot meet the test requirements. On the other hand, engineering tests often need to paste a lot of strain gauges to the surface of a sample. The non-reusable strain gauges also cause cost problems. Digital image correlation (DIC) is an optical method based on the principle of correlation before and after deformation of a tested object. DIC is a deformation analysis method generated by means of shooting with a CCD camera during the loading of the tested object and in combination with computer image processing and recognition technology, and has the advantages of full field, non-contact, timeliness and low environmental requirement. When the mechanical properties of a material are analyzed, it is usually assumed that the material is continuous and uniform, regardless of the defects or cracks of the material itself, but the anisotropies of products in the manufacturing industry can be seen everywhere, especially in the additive manufacturing industry, in which a sample shows obvious anisotropy because of its unique manufacturing process of layer-by-layer stacking molding.
In the additive manufacturing industry, the stiffness, strength, and stability of the sample may be affected by different factors such as packing density, printing speed, bottom plate temperature, needle temperature, and layer thickness.
The change of any condition will affect the mechanical properties of the product, the surface finish, etc. 3D printing rapid prototyping technology is an emerging additive manufacturing technology that is rapidly developing in the manufacturing industry.
It is compared as “a manufacturing technology having industrial revolution significance”. Research on how to improve the properties of printed products has also been a concerned topic in recent years.
It benefits from the integration of cutting-edge technologies in multiple subject areas, has been applied to a certain degree in the fields of aerospace, national defense, biomedicine, government, medical equipment, high technology, education industry, manufacturing industry, automobiles, motorcycles, home appliances, etc., and has very broad development prospects.
So far, there are more and more types of printing technology.
The printing technology certainly involves a fused deposition modeling (FDM) technology, which is a complex process having a lot of parameters that affect product quality and material properties, and the combination of these parameters is often difficult to understand.
Bi Yongbao et al. blended wheat straw powder and PLA to prepare a biomass composite printing material, researched the mechanical properties of a product of the composite material by exploring different packing density, layer thickness, printing speed, temperature and other conditions, and obtained optimal printing methods for corresponding conditions in combination with experiments.
Raunt et al. considered the effect of placement angles on the mechanical properties of a product.
Shu You et al. explored the effects of different conditions on the mechanical properties of 3D printed degraded L-lactic acid (PLLA) samples from the three factors of printing speed, packing density and temperature.
There are also many parameters such as construction direction, layer thickness, grating angle, grating width and air gap, which have a great impact on the quality and property of FDM printed parts.
Since 3D printing technology has been quite mature, in recent years, more and more researchers at home and abroad have paid more attention to the setting of printing parameters, or the research of mechanical properties of modified materials blended with printing materials, many scholars have researched the mechanical properties of samples from the setting of various printing parameters, but few scholars have studied the mechanical properties of products from measurement means.
The mechanical properties are critical to functional parts, and the mechanical properties of samples molded by different ways are significantly different, while the experts and scholars at home and abroad have less research on the mechanical properties of printing samples molded with different construction orientations, so it is absolutely necessary to check the influence of process parameters on the mechanical properties.
Therefore, it is necessary to further research the differences in mechanical properties of components caused by different printing parameters, but the inventors found that the differences in mechanical properties of components are not analyzed in the prior art, especially the differences in mechanical properties of parts processed by low-cost 3D printers are seldom analyzed.
Summary of the Invention In view of the shortcomings of the prior art, the objective of the present invention is to overcome the shortcomings of the prior art, seek a method for testing the mechanical properties of printing samples, and provide a method for analyzing the mechanical properties of 3D printing samples with different construction orientations, in which a digital image correlation method is applied to the additive manufacturing industry to analyze the differences in mechanical properties of printing molding samples with different construction orientations.
In order to achieve the above objective, the present invention is implemented by the following technical solution: In a first aspect, an embodiment of the present invention provides a method for analyzing the mechanical properties of 3D printing samples with different construction orientations, including the following steps: fabricating multiple sample strips with different construction orientations by 3D printing, and forming speckles on a surface of the sample strip;
placing the sample strip on a loading device, and debugging the loading device; performing a mechanical property test, and capturing images of the sample strip throughout the test; comparing and analyzing the images of the sample strip before and after deformation by using a digital image correlation method to obtain displacement and strain information; obtaining a stress-strain curve according to the strain information, and obtaining property parameters of the sample strip; and repeating the above steps to complete the mechanical property test of the multiple sample strips with different construction orientations, and analyzing the differences in the mechanical properties of the sample strips with different construction orientations.
As a further technical solution, the step of forming speckles on a surface of the sample strip Is: spraying a whole side surface of the sample strip with a white matte paint, and then embellishing it with a black matte paint to form speckles uniformly distributed.
As a further technical solution, the step of forming speckles on a surface of the sample strip Is: spraying a whole side surface of the sample strip with a black matte paint, and then embellishing it with a white matte paint to form speckles uniformly distributed.
As a further technical solution, the loading device includes a universal tester, the universal tester is connected to a universal test control system, a CCD industrial camera is arranged in front of the universal tester, and the CCD industrial camera is connected to a computer; and a clamping and loading member is arranged in the universal tester.
As a further technical solution, when a three-point bending test is performed, the clamping and loading member includes a slide way and loading supports, a top of the slide way is provided with a chute, the two loading supports are spaced apart from the chute, and the loading supports are slidable along the chute; the sample is placed on the two loading supports, and a concentrated force applying device is arranged above the slide way.
5 As a further technical solution, the concentrated force applying device includes a C-shaped member with an upward opening, a top of the C-shaped member is connected to the universal tester, a bottom of the C-shaped member is connected to a loading rod, the loading rod is arranged vertically, and the slide way is arranged transversely.
As a further technical solution, the process of placing the sample strip is: placing the sample strip in the middle of the universal tester, such that the sample strip is balanced vertically and horizontally, and the side of the spline sprayed with speckles faces the CCD industrial camera. As a further technical solution, the process of obtaining displacement and strain information is: comparing and analyzing the images of the sample strip before and after deformation, then calculating correlations of subsets of the images before and after deformation to obtain relative displacements of center pixels of the subsets before and after deformation, thus obtaining the displacement and strain information. As a further technical solution, the process of obtaining property parameters of the sample strip is: obtaining a real-time stress-strain curve from the displacement and strain information and in combination with the relationship between load and time, and obtaining property parameters such as tensile strength, elongation, deformation speed and acceleration of the sample strip in combination with a strain cloud diagram obtained by the digital image correlation method. As a further technical solution, the mechanical property test includes a tensile test, a compression test, and a three-point bending test, the three tests are sequentially performed on the multiple sample strips with different construction orientations, and the mechanical properties of the sample strips with different construction orientations under each test condition are analyzed.
Beneficial effects of the present invention are as follows: The present invention can accurately obtain the displacement strain of the full field, and measure the tensile (compression/bending) strength and elongation of the samples.
The present invention applies the digital image correlation method to the additive manufacturing industry for the first time, and comprehensively analyzes the mechanical properties of the printing samples with different construction orientations.
For other printing parameters changed, this method may also be used to deeply research the differences in mechanical properties.
The present invention overcomes contact measurement of the traditional methods.
This method can analyze the displacement, strain and stress from a microscopic perspective, with a wider range and higher precision, and can better reflect real mechanical properties of the printing samples. The present invention overcomes the problems of large error of measured data given by traditional measurement means and strict requirements for test conditions. The method is simple and fast in measurement, and has low requirements for test conditions.
The method of the present invention overcomes the defect in the prior art that the average value of failure of the splines obtained only by analyzing the pressure-time curve in the stretching process cannot well reflect the situation of local failure, and can analyze the whole process of loading of the entire sample in real time.
Brief Description of the Drawings The accompanying drawings constituting a part of the present invention are used for providing a further understanding of the present invention, and the schematic embodiments of the present invention and the descriptions thereof are used for interpreting the present invention, rather than constituting improper limitations to the present invention.
FIG 1 is a step flowchart of a method for analyzing the mechanical properties of a 3D printing sample according to one or more embodiments of the present invention,
FIG 2 is a schematic diagram of a loading device according to one or more embodiments of the present invention; FIG 3a is a schematic diagram of a standing sample according to one or more embodiments of the present invention; FIG 3b is a schematic diagram of a tilting sample according to one or more embodiments of the present invention; FIG 3c is a schematic diagram of a lying sample according to one or more embodiments of the present invention; FIG 4 is a schematic diagram of shape and size of a sample according to one or more embodiments of the present invention; FIG 5 is a schematic diagram of a clamping and loading member used in three-point bending test according to one or more embodiments of the present invention; FIG 6 is a schematic diagram of an image processing flow according to one or more embodiments of the present invention; In the figures: 1 universal tester, 2 universal test control system, 3 CCD industrial camera, 4 computer, 5 3D printing sample, 6, loading support, 7 slide way, 8 concentrated force applying device.
In order to show the position of each part, the distance or size between them is exaggerated, and the schematic diagrams are only for schematic use.
Detailed Description of the Embodiments It should be pointed out that the following detailed descriptions are all exemplary and aim to further illustrate the present invention. Unless otherwise specified, all technological and scientific terms used in the present invention have the same meanings generally understood by those of ordinary skill in the art of the present invention.
It should be noted that the terms used herein are merely for describing specific embodiments, but are not intended to limit exemplary embodiments according to the present invention. As used herein, unless otherwise clearly stated in the present invention, singular forms are also intended to include plural forms. In addition, it should also be understood that when the terms “contain” and/or “comprise” are used in the description, it indicates the presence of features, steps, operations, devices, ingredients, and/or combinations thereof.
For the convenience of description, the terms “upper”, “lower”, “left” and “right” in the present invention only indicate the upper, lower, left and right directions of the drawings, but do not limit the structure.
They are only for the convenience of description and the simplification of description, do not indicate or imply that the devices or elements must have specific directions or be constructed and operated in specific directions, and therefore cannot be understood as limitations to the present invention.
Interpretation of terms: the terms “mounted”, “coupled”, “connected”, “fixed” and the like in the present invention should be generally understood, for example, the “connected” may be fixedly connected, detachably connected, integrated, mechanically connected, electrically connected, directly connected, indirectly connected by a medium, internally connected between two elements, or interact between two elements, and the specific meanings of the terms in the present invention may be understood by those of ordinary skill in the art according to specific circumstances.
As described in the background, there are shortcomings in the prior art.
In order to solve the above technical problems, the present invention proposes a method for analyzing the mechanical properties of 3D printing samples with different construction orientations.
In a typical embodiment of the present invention, as shown in FIG 1, a method for analyzing the mechanical properties of 3D printing samples with different construction orientations is proposed.
This method is completed by loading a 3D printing sample to a loading device.
As shown in FIG 2, the main structure of the loading device includes a universal tester 1, a universal test control system 2, a CCD industrial camera 3, and a computer 4. A 3D printing sample 5 is connected to the universal tester, the universal tester is used to load the 3D printing sample, the universal test control system is connected with the universal tester to control the start and stop of the universal tester, the CCD industrial camera is arranged in front of the universal tester to capture an image when the universal tester loads the 3D printing sample, and the CCD industrial camera is connected with the computer to store the captured image.
This method analyzes the differences in mechanical properties of three groups of samples with different construction orientations. Thus, 3D printing is required to fabricate three types of samples with different construction orientations first, for example, standing type in FIG 3a, tilting type in FIG. 3b, and lying type in FIG 3c. The samples are fabricated by the following process: Due to the low cost of a polylactic acid material, the maturity of fused deposition printing technology, and the universality of research of many experts and scholars based on the parameters of the material, polylactic acid molded by fused deposition is selected to print the samples, and standard tensile polylactic acid sample strips are fabricated according to GB/T 1040-2006. The standard sample fabricating process of this experiment is: establishing a standard model using three-dimensional modeling software SolidWorks, slicing and supporting the model with cheap and environment-friendly polylactic acid wires and a Tiertime up box printer, and printing three groups of standard splines with different construction orientations by a fused deposition printing method.
Here, taking the tensile test of different constructed samples as an example for illustration, detection and difference analysis of mechanical properties are performed on the tensile sample strips molded with different construction orientations by using the above-mentioned loading device, and the specific test method is carried out according to the following steps:
1. Three types of tensile sample strips with different construction orientations are fabricated by 3D printing.
2. Before test, a whole side surface of the spline is sprayed with a white matte paint, and then embellished with a black matte paint to form appropriate speckles, and vice versa.
The speckles are used as important information for comparison before and after deformation, and the speckles are uniformly and randomly distributed. The size of speckle particles is related to an object distance, because the quality of the speckles directly affects the accuracy and precision of the results.
In order to ensure the quality of speckle formation, when the matte paint is sprayed to the spline, a layer of gauze is spread between the spline and a paint nozzle. In addition, the angle, force and the like of spraying are changed to some extent.
3. When the tensile test is performed by the loading device, wedge-shaped clamps are mounted to the universal tester to clamp the tensile spline; when the tensile spline is placed by the loading device, the tensile spline should be balanced vertically and horizontally, which is achieved by adjusting the clamps and using a gradienter, to avoid a horizontal component force during the tensile test.
The printing tensile spline is placed in the middle of the universal tester, and the side of the printing tensile spline sprayed with speckles faces the CCD industrial camera, such that a spline image appears in the middle of the camera acquisition computer.
4. The CCD industrial camera and the universal material tester are debugged, and the loading speed of the universal tester and the acquisition speed of the camera are adjusted together to achieve an appropriate image acquisition frequency, which will affect its precision. The debugging is performed according to different precision requirements. In this embodiment, the loading speed of the universal tester is adjusted to 0.1 MPa/s, and the acquisition speed is adjusted to 2 fps.
5. A light source is also one of the important factors that affect the accuracy and precision of the results. Generally, ordinary white light is used, but special attention should be paid to two points here: first, the image should not be exposed or dark, and second, strobing should be avoided during the test.
The light source is ordinary white light, and a DC light source may be added or the brightness of the light source may be adjusted according to the situation on site, so that the lighting effect on site can meet the test requirements, and local exposure and local darkness do not occur on the surface of the sample.
When the brightness of the light source is adjusted, images displayed on the computer should be observed much, or a few images are first shot for analysis, and the light is supplemented with DC light to avoid strobing. If the natural light at the test site meets the requirements, light supplement is not required.
6. After the position is adjusted as described in step 4, the CCD industrial camera is connected with the universal material tester, the universal material tester is triggered to start while the CCD industrial camera is started, and the CCD industrial camera captures images in the whole process of sample loading.
7. The images before and after deformation, captured by the CCD industrial camera, are compared and analyzed by using a DIC method. The basic principle of this method is: surface shape images of the tested object before and after deformation are converted into digital images by an emitron camera or a digital camera, then correlation calculation is performed on subsets of the images before and after deformation to obtain relative displacements of center pixels of the subsets before and after deformation, and mechanical information such as displacement and strain is obtained accordingly. When searching and matching for correlation calculation is performed in this method, the standard covariance correlation function used is:
M M > lens leteruyvy-g,l Clu v) = A 5 ee M Af U 2 Van} > Dlt vrg] xm Af y=M x=M y=-Af Where OV) and BEF Y+V) represent gray values of each pixel of the images; To and 8» are average gray values of the subsets of the images; u and v are displacements of the centers of the subsets in units of pixel.
8. Real-time image displacement and strain information of the sample may be obtained on the acquisition computer according to step 7, and combined with the relationship between load and time given by the universal tester to obtain a stress-strain curve in real time, a strain cloud diagram is obtained by the digital image correlation method, and property parameters such as tensile strength, elongation, deformation speed and acceleration of the sample are obtained.
The images may be processed by means of software such as MATLAB based on the principle of the digital image correlation method, and then the parameters that characterize the basic mechanical properties of the sample can be obtained by offset guiding, derivation and the like.
9. The above steps are repeated to complete multiple repeated tests on the three groups of samples molded with different construction directions. During the test, the images may be analyzed in real time, and combined with the data of the universal tester to obtain a stress-strain relationship, and the differences in mechanical properties of the 3D printing samples molded in different construction orientations under the tensile tests can thus be analyzed.
At the end of the test, the information such as images captured during the test and loading time data of the tester may also be saved for future use.
Compared with the prior art, the present invention can accurately obtain the displacement strain of the full field, and measure the information such as tensile (compression/bending) strength and elongation of the samples.
Similarly, corresponding compression test and three-point bending test can be performed by replacing the sample clamps in the loading device based on the same test principle as the tensile test, and details are not described herein again.
The three-point bending test is described as follows: The universal tester is provided with a clamping and loading member. When the three-point bending test is performed, the clamping and loading member includes two loading supports 6, a slide way 7, and a concentrated force applying device 8, as shown in FIG. 5. The concentrated force applying device is machined according to the universal tester and can be directly mounted on an indenter of the universal tester, the concentrated force applying device includes a C-shaped member with an upward opening, a top of the C-shaped member is connected to the universal tester, a bottom of the C-shaped member is connected to a loading rod, the loading rod is arranged vertically and its bottom is arranged above the slide way; the slide way is arranged transversely, the slide way is provided with a chute, the two loading supports are connected to the chute of the slide way at a set distance, and the loading supports can slide along the slide way to adjust the position of a loading point during three-point bending, so as to better complete the three-point bending test. The 3D printing sample 1s placed on the two loading supports during the test, and the universal tester loads the sample through the concentrated force applying device mounted on the indenter.
5 When an upper loading end of the concentrated force applying device is in a laboratory, its presses the symmetrical position of the sample. The opening of the C-shaped member of the concentrated force applying device can accommodate supporting devices of the universal material tester. After the concentrated force applying device is fixed, it can transfer pressure down firmly. The concentrated force applying device can be conveniently mounted and removed during use, its end in contact with the sample should be polished smooth, and it should be always vertical during the loading process, which requires it to have certain rigidity and stability. Before the test, a three-point surface in contact with the sample should be wiped up and coated with a thin layer of lubricant.
The bending performance of the three-point bending sample is tested according to the GB/T 9341-2006 standard. For the three-point bending test, it should be first ensured that the two loading supports below are horizontal and the slide way has sufficient rigidity. Before the test, the loading supports are adjusted to balance by using a gradienter here and fixed, and the loading supports are spaced at the ends by a distance of 3 cm. However, the distance of 3 cm in this test is not a constant. Different spans correspond to different pressures, which does not affect the analysis and evaluation on the mechanical properties of the printing spline.
The present invention applies the DIC method to the additive manufacturing industry for the first time, and comprehensively analyzes the mechanical properties of the printing samples with different construction orientations. For other printing parameters changed, this method may also be used to deeply research the differences in mechanical properties.
The present invention overcomes contact measurement of the traditional methods. This method can analyze the displacement, strain and stress from a microscopic perspective, with a wider range and higher precision, and can better reflect real mechanical properties of the printing samples.
The present invention realizes real-time analysis on the images, and the images together with the basic displacement, strain, maximum bending strength, etc. synchronously obtained during the test are used to characterize the basic mechanical properties such as stretching, bending, and compression.
At present, few scholars have conducted differential analysis on the mechanical properties of printing samples with different construction orientations, while the present invention can achieve this analysis. This method can conveniently detect and analyze the basic mechanical properties such as stretching, compression, and bending, and the results are traceable.
In the field of additive manufacturing, people pay great attention to the influence of different parameters on the mechanical properties of the samples. The detection proposed by the present invention for different construction orientations can be expanded for other changed parameters that cause differences in properties.
The present invention solves the problems of large error of measured data given by traditional measurement means and strict requirements for test conditions. The method is simple and fast in measurement, has low requirements for test conditions, and can analyze the whole process of loading of the entire sample. The method has the advantages of ingenious design, simple operation, low experimental conditions, relatively high environmental adaptability, and accurate measurement results. The application of the DIC method in the field of additive manufacturing has the advantages of digital accuracy, traceability, real-time analysis, full field, non-contact and the like, so that the method has a wide application market in this industry.
The present invention analyzes the differences in mechanical properties of the printing samples with different construction orientations, and performs non-contact and full-field deformation analysis on the whole process of stretching, compression, and three-point bending test for the printing samples with different construction orientations to detect the differences in mechanical properties of the printing samples with different construction orientations, which provides a reliable basis for further theoretical research, and provides a new idea for subsequent researchers of 3D printing in terms of physical shape and temperature condition analysis.
The present invention records the entire test process by means of the DIC method. Its unique full-field analysis and real-time recording functions provide a comprehensive and traceable convenience for subsequent research on the mechanical properties of the samples, and provide effective and convenient means for in-depth research on the mechanical properties of the samples.
In order that those skilled in the art can understand the technical solution of the present application more clearly, the technical solution of the present application will be described in detail below in combination with a specific embodiment.
This embodiment is described by a tensile test. The middle section of a sample is used to measure the tensile deformation. The length /; of this section is called “gauge length”. The thicker parts at both ends are the head, and are loaded into chucks of the tester. The shape of the head of the sample depends on the requirements of the chuck of the tester. FIG 4 shows the shape and size of the sample. In this example, /,=80 mm. The specific test steps are as follows: (1) The 3D printing sample is sprayed with black and white speckles, dried, and then mounted in the universal tester by using the tensile clamps of the universal tester, and the universal test control system is connected to the universal tester. Software of the universal tester is opened to record the loading displacement, velocity and force of the sample in real time, and a tension-displacement curve is drawn in real time.
(2) The CCD industrial camera is connected to the computer, acquisition software VIC-2D of the camera is opened, and the CCD industrial camera is debugged, such that a lens of the camera focuses on an observation area of the sample. The sampling frequency of the camera is set to 2 fps.
(3) The universal tester is turned on, and the CCD camera is activated by using typical DIC software and VIC-2D software. When tensile loading is performed on the sample by the clamps of the tester, the full-field deformation of the sample is acquired in real time by using the CCD camera at the sampling frequency of 2 fps, and the images are automatically saved in a designated folder in a numerical order to obtain sequence images of sample deformation during loading, for example, Image001, Image002,
Image003...
(4) The test 1s completed until tensile failure occurs in the sample. The CCD camera stops capturing images. All acquired data is saved.
(5) The sequence images saved are processed by using the DIC method, all the sequence images are compared and analyzed with Image001, displacement fields and strain fields in all subsequent states are obtained by calculation through the process shown in FIG 5, and the displacement fields and strain fields are analyzed to obtain parameters such as deformation speed, acceleration, and elongation of the sample.
The elastic modulus and Poisson's ratio of the sample are obtained in combination with the information about the loading displacement and force of the sample acquired by the universal tester.
Described above are merely preferred embodiments of the present invention, and the present invention is not limited thereto. Various modifications and variations may be made to the present invention for those skilled in the art. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention shall fall into the protection scope of the present invention.
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| CN115015103B (en) * | 2022-05-24 | 2023-01-03 | 武汉中誉鼎力智能科技有限公司 | Real-time detection method and device for friction factor and microscopic morphology of material surface |
| CN115184141B (en) * | 2022-06-27 | 2024-06-07 | 武汉理工大学 | DIC-based reinforcement compressive deformation measurement method |
| WO2024020977A1 (en) * | 2022-07-29 | 2024-02-01 | 中国矿业大学(北京) | Method for acquiring dynamic evolution information of displacement field and strain field inside solid |
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