Method for testing fracture strain temperature correlation of metal material
By using speckle and blue light imaging techniques based on high-temperature coatings, combined with DIC software and a high-temperature environmental chamber, the inconsistency problem in fracture strain measurement at high temperatures was solved, achieving high-precision fracture strain measurement and providing reliable data for material property modeling.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-16
- Publication Date
- 2026-04-07
AI Technical Summary
Existing high-temperature strain measurement techniques suffer from problems such as the easy failure of traditional strain gauges, inconsistencies in measurements due to thermal expansion in the DIC method, and difficulty in accurately extracting the law of fracture strain change with temperature, which affect the temperature term correction of material models.
Using speckle pattern made with high-temperature coating, blue light imaging, and DIC software matching technology, combined with a high-temperature environmental chamber and temperature control system, fracture strain is measured at high temperatures.
It achieves high-precision and repeatable measurement of fracture strain at high temperatures, providing reliable material property data support.
Smart Images
Figure CN121805031A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of material mechanical property testing, and particularly relates to a test method for temperature correlation of fracture strain of metal materials. BACKGROUND
[0002] The relationship between the fracture strain and temperature is an important part of accurately establishing the material constitutive, and the fracture strain is decoupled from the strain rate according to the Johnson-Cook model, and the following formula is met: wherein, is the fracture strain at the reference temperature, can be related to the strain rate, is the homologous temperature: and respectively are the melting temperature and the reference temperature of the material. Stable and accurate high-temperature fracture strain test data are the key to determining the model parameters such as the index m, and .
[0003] The existing high-temperature strain measurement technologies mainly include high-temperature strain gauges and DIC, but there are certain technical problems to be solved: (1) the traditional strain gauges are prone to failure and cannot accurately measure large deformation; (2) the conventional DIC method is difficult to realize the consistency of measurement at different temperatures when the gauge length section of the sample changes due to thermal expansion; (3) the change rule of the fracture strain with temperature is difficult to accurately extract, which affects the temperature term correction of the material model.
[0004] Therefore, a high-temperature stable, positioning consistent and data complete fracture strain test method is urgently needed. SUMMARY
[0005] In view of the above technical problems, the application provides a test method for temperature correlation of fracture strain of metal materials.
[0006] The test method for temperature correlation of fracture strain of metal materials provided by the application specifically includes: S1, configuring a test device for fracture strain temperature correlation; S2, preparing high-temperature speckles for tracking deformation of the sample; S3, taking high-temperature red light suppression measures to improve the imaging quality; S4, performing feature matching on the grid and the imaging picture; S5, performing measurement of the fracture strain at different temperatures.
[0007] In S1, the test device for configuring the fracture strain temperature correlation test comprises: deploying a high-temperature system on a tensile testing machine; wherein: The high-temperature system comprises a high-temperature environmental box, a temperature control system and a water cooling system; A lengthened chuck made of a high-temperature alloy material fixes the sample and is inserted into the high-temperature environmental box and heated synchronously with the sample; The temperature control system is adjusted, the target temperature is set, the heating rate is adjusted, the sample is heated to the target temperature and kept, and then loading is performed.
[0008] In S1, the test device for configuring the fracture strain temperature correlation test comprises: determining the sample configuration; wherein: The sample used is an NT06 sample; a notch is cut on the basis of the tensile sample by a wire cutting, serving as a mark for global DIC calibration.
[0009] In S2, the high-temperature speckle is made, comprising: A high-temperature speckle for tracking the deformation of the sample is made by using a high-temperature paint, the highest use temperature reaches 1500℃, the high-temperature paint is made by adding black or milky white nano composite ceramic powder in a high-temperature adhesive; the liquid adhesive and ceramic particles are uniformly mixed by rotating and mixing the paint on a lathe at a rotating speed of 200 revolutions / min for 20 minutes; the undispersed ceramic particle groups are filtered out by using a 200-mesh filter screen; the sample is subjected to sandblasting roughening treatment by using a diamond grit with a particle size of 46 mesh; Spraying is performed by using a spray gun with a caliber of 0.5mm at 4-6 atmospheres, white paint is first sprayed as a background, the thickness is 50um; after the white paint is completely dry, a rectangular hole mask is placed on the surface of the sample, black paint is uniformly sprayed against the mask, the hollowed-out place leaves black paint on the surface of the sample, forming a white background black dot speckle; the speckle has a regular shape and repeatability, and the test is performed after the paint inside is completely dry after standing at room temperature for 7 days.
[0010] In S3, high-temperature red light suppression measures are taken to improve the imaging quality; wherein: 450nm wavelength blue light is used as a light source, a 450nm narrow bandwidth filter is added in front of the lens, so as to suppress the interference infrared light.
[0011] In S4, the grid and the imaging picture are matched; wherein: The same batch of samples are formed by one wire cutting and have the same size; a sample model is built in a finite element CAE software and is subjected to appropriate grid division, so that there is at least one mark point in each unit; the grid is imported into EikoSim DIC software, the corresponding feature points on the grid and the imaging picture are clicked, and the grid and the imaging picture are accurately positioned by using the matching algorithm of the software to realize matching.
[0012] In S5, fracture strain measurements are performed at different temperatures; where: Strain or point displacement measurements were performed at the same location on the surface of different specimens in different tests. The same location and the same size area on different specimens at different temperatures were used as the strain extraction interval, and the deformation at the same location on the specimens at different temperatures was compared.
[0013] In S5, fracture strain measurements are performed at different temperatures; specifically, the relationship between fracture strain and temperature is determined. The value represents the fracture strain at temperature, and L represents the length of the marked segment at different times. It is directly extracted by DIC, and the fracture strain is the value when the crack occurs.
[0014] In S5, fracture strain measurements are performed at different temperatures; where: Tensile tests were conducted on NT06 specimens at different temperatures, and the corresponding fracture strain was calculated using the relationship between fracture strain and temperature. The temperatures were set to 200℃, 400℃, and 600℃, and the relationship between strain and time was obtained. As the temperature increased, the time when the sample fractured was delayed; the higher the temperature, the greater the fracture strain.
[0015] In summary, this invention has the inherent advantage of resisting the effects of thermal expansion. Through high-temperature resistant ceramic speckle, blue light imaging, and local strain extraction strategies, it achieves high-precision, repeatable, and temperature-dependent measurement of fracture strain at high temperatures, providing reliable data support for material performance modeling. Attached Figure Description
[0016] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0017] Figure 1 This is a schematic flowchart of a test method for the temperature correlation of fracture strain in metallic materials according to an embodiment of the present invention. Figure 2 This is a schematic diagram of a high-temperature tensile testing system according to an embodiment of the present invention; Figure 3 This is a schematic diagram of an NT06 specimen used for high strain rate and high temperature fracture strain testing according to an embodiment of the present invention. Figure 4 This is a schematic diagram of high-temperature speckle patterns obtained using a photomask according to an embodiment of the present invention; Figure 5 This is a schematic diagram comparing images before and after red light suppression measures are implemented according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the matching effect between the finite element mesh and the sample surface and the extraction area of the central strain gauge during the EikoSim DIC calculation process according to an embodiment of the present invention. Figure 7 This is a schematic diagram of the average strain and fracture strain extracted from the central monitoring area according to an embodiment of the present invention; Figure 8 This is a schematic diagram of the experimental value and fitting curve of the fracture strain temperature term according to an embodiment of the present invention. Detailed Implementation
[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0019] The first aspect of this invention proposes a method for testing the fracture strain-temperature correlation of metallic materials, the method comprising (e.g.) Figure 1 (as shown) S1. Configure the test apparatus for fracture strain-temperature correlation testing; S2. Fabricate high-temperature speckle patterns for tracking sample deformation; S3. High-temperature red light suppression measures are adopted to improve imaging quality; S4. Perform feature matching on the grid and the imaging image; S5. Perform fracture strain measurements at different temperatures.
[0020] In S1, the test setup for the fracture strain-temperature correlation test includes: deploying a high-temperature system on a tensile testing machine; wherein: The high-temperature system includes a high-temperature environmental chamber, a temperature control system, and a water cooling system; The sample is fixed with an extended clamp made of high-temperature alloy material and inserted into a high-temperature environment chamber for synchronous heating with the sample; Adjust the temperature control system, set the target temperature, adjust the heating rate, heat the sample to the target temperature and hold it, and then apply the load.
[0021] In S1, the test setup for the fracture strain-temperature correlation test includes: determining the specimen configuration; wherein: The specimen used was the NT06 specimen; notches were cut into the tensile specimen by wire cutting as marks for global DIC calibration.
[0022] In S2, the production of high-temperature speckle includes: High-temperature coatings are used to create high-temperature speckle patterns for tracking sample deformation, with a maximum operating temperature of 1500℃. The high-temperature coating is made by adding black or milky white nano-composite ceramic powder to a high-temperature binder. The coating is mixed on a lathe at 200 rpm for 20 minutes to ensure uniform mixing of the liquid binder and ceramic particles. Undispersed ceramic particle clumps are filtered out using a 200-mesh filter. The sample is then roughened by sandblasting with 46-mesh diamond abrasive. Spraying was performed using a 0.5mm nozzle at 4-6 atmospheres. First, a white paint was sprayed as a background with a thickness of 50µm. After the white paint was completely dry, a rectangular perforated mask was placed on the sample surface, and black paint was sprayed evenly onto the mask. The perforated areas left black paint on the sample surface, forming a speckled pattern of black dots on a white background. The speckled pattern was regular and repeatable. The sample was left to stand at room temperature for 7 days to allow the paint to dry completely before the test.
[0023] In S3, high-temperature red light suppression measures are adopted to improve image quality; among them, 450nm wavelength blue light is used as the light source, and a 450nm narrow bandwidth filter is added in front of the lens to suppress interfering infrared light.
[0024] In S4, feature matching is performed on the grid and the imaging image; where: The same batch of samples were cut by wire cutting, and their dimensions were exactly the same. The sample model was built in the finite element CAE software and a suitable mesh was generated so that there was at least one marker point in each element. The mesh was imported into the EikoSim DIC software, and the corresponding feature points on the mesh and the imaging image were clicked. The matching algorithm of the software was used to accurately locate the mesh and the imaging image to achieve matching.
[0025] In S5, fracture strain measurements are performed at different temperatures; where: Strain or point displacement measurements were performed at the same location on the surface of different specimens in different tests. The same location and the same size area on different specimens at different temperatures were used as the strain extraction interval, and the deformation at the same location on the specimens at different temperatures was compared.
[0026] In S5, fracture strain measurements are performed at different temperatures; specifically, the relationship between fracture strain and temperature is determined. The value represents the fracture strain at temperature, and L represents the length of the marked segment at different times. It is directly extracted by DIC, and the fracture strain is the value when the crack occurs.
[0027] In S5, fracture strain measurements are performed at different temperatures; where: Tensile tests were conducted on NT06 specimens at different temperatures, and the corresponding fracture strain was calculated using the relationship between fracture strain and temperature. The temperatures were set to 200℃, 400℃, and 600℃, and the relationship between strain and time was obtained. As the temperature increased, the time when the sample fractured was delayed; the higher the temperature, the greater the fracture strain.
[0028] In some embodiments, such as Figure 2 As shown, a high-temperature system is added to the tensile testing machine. This system includes a high-temperature environmental chamber, a temperature control system, and a water cooling system. During the test, an extended clamp made of high-temperature alloy material is used to fix the specimen, which is then inserted into the high-temperature environmental chamber and heated synchronously with the specimen. The temperature control system is adjusted, the target temperature is set, and the heating rate (10℃ / min) is adjusted to heat the specimen to the target temperature and maintain it for 10 minutes before loading is applied.
[0029] In some embodiments, the sample used is an NT06 sample, such as... Figure 3 As shown. A notch with a radius of 6 mm and a center width of 6 mm was cut into the tensile specimen by wire cutting. Notches were also cut in other locations by wire cutting as markers for global DIC calibration.
[0030] In some embodiments, high-temperature DIC requires high-temperature resistant speckle patterns to track sample deformation. A high-temperature coating is used, with a maximum operating temperature of 1500°C. This high-temperature coating is made by adding black or milky-white nanocomposite ceramic powder to a high-temperature binder. Before use, the coating is stirred on a lathe at 200 rpm for 20 minutes to ensure the liquid binder and ceramic particles are evenly mixed. Undispersed ceramic particle clumps are then filtered out using a 200-mesh filter. The sample is then roughened by sandblasting with 46-mesh corundum (white corundum). Spraying is performed using a 0.5mm nozzle at 4-6 atmospheres. First, a white coating is sprayed as a background, approximately 50µm thick. After the white coating is completely dry, a mask with 0.2mm rectangular holes is placed on the sample surface. Then, black coating is sprayed evenly onto the mask. The cutouts will leave black coating on the sample surface, forming a speckle pattern with black dots on a white background. Figure 4 As shown. This type of speckle pattern is relatively regular and has good repeatability. After the speckle pattern is prepared, it should be left to stand at room temperature for 7 days to allow the paint to dry completely before testing.
[0031] In some embodiments, infrared light generated by high-temperature thermal radiation also has a significant impact on camera image quality. If it is not effectively suppressed, the image contrast will be very low or even undetectable (e.g., ...). Figure 5 As shown in the diagram on the left), this makes it impossible to obtain accurate failure strain. In the experiment, we used blue light with a wavelength of approximately 450nm as the light source and added a 450nm narrow-bandwidth filter in front of the lens. This can suppress most of the interfering infrared light, resulting in a significant improvement in image quality (e.g., ...). Figure 5 As shown in the diagram on the right).
[0032] In some embodiments, samples from the same batch are cut in a single wire cut, resulting in identical dimensions. A sample model is created in finite element CAE software, and a suitable mesh is generated, ensuring that each element contains at least one or two marker points (black dots). The mesh is imported into EikoSim DIC software. By clicking on the corresponding feature points on the mesh and the image, and then using the software's matching algorithm, the mesh and image are precisely located. The mesh-sample matching is as follows: Figure 6 As shown.
[0033] In some embodiments, after the finite element mesh is matched with the specimen, it is very easy to select the same location on the surface of different specimens in different tests for strain or point displacement measurement. Even when the specimen's dimensions change due to thermal expansion, the matching accuracy can be guaranteed as long as the thermal expansion of the material is isotropic. In this way, regions of the same location and size on different specimens at different temperatures can be used as strain extraction intervals, with high repeatability and reliability. This makes it relatively convenient to compare the deformation at the same location on the specimen at different temperatures.
[0034] In some embodiments, new interfaces are actually formed during fracture, and no paint can completely follow the specimen deformation, making direct measurement of fracture strain virtually impossible. Therefore, the only option is to enlarge the strain calculation scale and compare the average deformation across the entire observation area. Considering that the specimen dimensions are completely uniform, it is only necessary to monitor the deformation within a small local area and compare the fracture strain in the same area at different temperatures to obtain the relationship between fracture strain and temperature. In practice, we select the center position of the specimen along the axial direction... Strain extraction over a 5mm length region ( Figure 6 The black line in the diagram represents the strain calculation area.
[0035] In some embodiments, the strain is calculated as follows: L is the length of the marked segment at different times, which can be directly extracted using DIC. It is the fracture strain when the crack occurs.
[0036] In some embodiments, the fracture strain is calculated using the above formula by conducting tensile tests on NT06 specimens at different temperatures. In this case, three temperatures were set: 200℃, 400℃, and 600℃, and the relationship between strain and time was obtained, as follows: Figure 7 As shown.
[0037] In some embodiments, it can be observed that the time of fracture of the specimen is significantly delayed as the temperature increases. Simultaneously, the higher the temperature, the greater the fracture strain, consistent with the performance characteristics of metals in high-temperature environments. Table 1 summarizes the temperature-induced increase in material plasticity at different temperatures; at 400℃ and 600℃, the fracture strain increased by 17.77% and 52.55%, respectively, demonstrating a very significant temperature effect.
[0038] Table 1: Normalized Thermoplastic Enhancement
[0039] Based on the data in Table 1, the influence coefficient of temperature on fracture strain in the formula was fitted (the fitting effect is shown in the figure). Figure 8 As shown), the transformation temperature and melting temperature remain the same as before, and are as follows: The power exponent obtained from the fitting is m=1.8214.
[0040] In some embodiments, the influence coefficient of temperature on a certain type of steel is calibrated, and the transformation temperature is determined. The melting temperature is The temperature power exponent m = 1.435 in the constitutive relation and 1.8214 in the fracture strain. It can be seen that temperature has a significant impact on the material properties of this type of steel, resulting in relatively poor high-temperature resistance.
[0041] In summary, this invention has the inherent advantage of resisting the effects of thermal expansion. Through high-temperature resistant ceramic speckle, blue light imaging, and local strain extraction strategies, it achieves high-precision, repeatable, and temperature-dependent measurement of fracture strain at high temperatures, providing reliable data support for material performance modeling.
[0042] Please note that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementations of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the appended claims.
Claims
1. A test method for the temperature correlation of fracture strain in metallic materials, characterized in that, The method performs a test on the temperature correlation of fracture strain in metallic materials by deploying a high-temperature system on a tensile testing machine; the method includes: S1. Configure the test apparatus for fracture strain-temperature correlation testing; S2. Fabricate high-temperature speckle patterns for tracking sample deformation; S3. High-temperature red light suppression measures are adopted to improve imaging quality; S4. Perform feature matching on the grid and the imaging image; S5. Perform fracture strain measurements at different temperatures.
2. The method for testing the correlation between fracture strain and temperature in metallic materials according to claim 1, characterized in that, In S1, the test setup for the fracture strain-temperature correlation test includes: deploying a high-temperature system on a tensile testing machine; wherein: The high-temperature system includes a high-temperature environmental chamber, a temperature control system, and a water cooling system; The sample is fixed with an extended clamp made of high-temperature alloy material and inserted into a high-temperature environment chamber for synchronous heating with the sample; Adjust the temperature control system, set the target temperature, adjust the heating rate, heat the sample to the target temperature and hold it, and then apply the load.
3. The method for testing the correlation between fracture strain and temperature in metallic materials according to claim 2, characterized in that, In S1, the test setup for the fracture strain-temperature correlation test includes: determining the specimen configuration; wherein: The specimen used was the NT06 specimen; notches were cut into the tensile specimen by wire cutting as marks for global DIC calibration.
4. The method for testing the correlation between fracture strain and temperature in metallic materials according to claim 3, characterized in that, In S2, the production of high-temperature speckle includes: High-temperature coatings are used to create high-temperature speckle patterns for tracking sample deformation, with a maximum operating temperature of 1500℃. The high-temperature coating is made by adding black or milky white nano-composite ceramic powder to a high-temperature binder. The coating is mixed on a lathe at 200 rpm for 20 minutes to ensure uniform mixing of the liquid binder and ceramic particles. Undispersed ceramic particle clumps are filtered out using a 200-mesh filter. The sample is then roughened by sandblasting with 46-mesh diamond abrasive. Spraying was performed using a 0.5mm nozzle at 4-6 atmospheres. First, a white paint was sprayed as a background with a thickness of 50µm. After the white paint was completely dry, a rectangular perforated mask was placed on the sample surface, and black paint was sprayed evenly onto the mask. The perforated areas left black paint on the sample surface, forming a speckled pattern of black dots on a white background. The speckled pattern was regular and repeatable. The sample was left to stand at room temperature for 7 days to allow the paint to dry completely before the test.
5. The method for testing the temperature correlation of fracture strain in metallic materials according to claim 4, characterized in that, In S3, high-temperature red light suppression measures are adopted to improve image quality; among them, 450nm wavelength blue light is used as the light source, and a 450nm narrow bandwidth filter is added in front of the lens to suppress interfering infrared light.
6. The method for testing the temperature correlation of fracture strain in metallic materials according to claim 5, characterized in that, In S4, feature matching is performed on the grid and the imaging image; where: The same batch of samples were cut by wire cutting, and their dimensions were exactly the same. The sample model was built in the finite element CAE software and a suitable mesh was generated so that there was at least one marker point in each element. The mesh was imported into the EikoSim DIC software, and the corresponding feature points on the mesh and the imaging image were clicked. The matching algorithm of the software was used to accurately locate the mesh and the imaging image to achieve matching.
7. The method for testing the temperature correlation of fracture strain in metallic materials according to claim 6, characterized in that, In S5, fracture strain measurements are performed at different temperatures; where: Strain or point displacement measurements were performed at the same location on the surface of different specimens in different tests. The same location and the same size area on different specimens at different temperatures were used as the strain extraction interval, and the deformation at the same location on the specimens at different temperatures was compared.
8. The method for testing the temperature correlation of fracture strain in metallic materials according to claim 7, characterized in that, In S5, fracture strain measurements are performed at different temperatures; specifically, the relationship between fracture strain and temperature is determined. The value represents the fracture strain at temperature, and L represents the length of the marked segment at different times. It is directly extracted by DIC, and the fracture strain is the value when the crack occurs.
9. The method for testing the temperature correlation of fracture strain in metallic materials according to claim 8, characterized in that, In S5, fracture strain measurements are performed at different temperatures; where: Tensile tests were conducted on NT06 specimens at different temperatures, and the corresponding fracture strain was calculated using the relationship between fracture strain and temperature. The temperatures were set to 200℃, 400℃, and 600℃, and the relationship between strain and time was obtained. As the temperature increased, the time when the sample fractured was delayed; the higher the temperature, the greater the fracture strain.