Strain testing device and method for 3D printing non-standard sample

Abstract

The invention discloses a strain testing device and a strain testing method for a 3D printing non-standard sample. The device comprises two tensile sample ends; the tensile sample lattice section is arranged between the two tensile sample ends; the connecting platform is arranged on the end head of the tensile sample, the connecting platform is positioned at the middle position of the end head of the tensile sample in the width direction, and two circular bosses are arranged on the connecting platform; the two measuring plates are bound with the two bosses arranged on the two connecting platforms respectively, and the other ends of the two measuring plates are in lap joint with each other; and two ends of the contact extensometer are clamped at the other ends of the two measuring plates. According to the invention, the deformation of the measurement area of the dot matrix is equivalently measured by measuring the relative displacement of the upper and lower measurement plates, so that the measurement of equivalent strain of the non-standard tensile sample is realized, the measurement cost is effectively reduced, the measurement efficiency is improved, and the measurement accuracy is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of 3D printed parts mechanical property testing, and in particular to a strain testing device and method for 3D printed non-standard samples. Background Art

[0002] With social progress and industrial development, traditional manufacturing processes have exposed limitations in meeting the needs of personalization, complexity and high performance. 3D printing lattice technology, with its unique advantages, provides a new way to solve these problems. 3D printing lattice structure has the characteristics of light weight, high strength and strong designability, and has broad application potential in aerospace, biomedicine, construction and other fields. For example, it is used in aerospace to manufacture lightweight and high-strength aviation structural parts, reduce the weight of aircraft and improve fuel efficiency; in the biomedical field, it is used for customized implants to meet the personalized needs of patients and promote the repair of bone, soft tissue and other injuries; in the construction field, it is used to prepare new building materials to achieve efficient and sustainable development of building structures.

[0003] 3D printed lattice structures are porous, non-uniform and anisotropic, and their basic mechanical properties need to be tested by stretching. However, traditional tensile specimen design standards are mainly applicable to uniform materials prepared by traditional processing methods, which cannot fully reflect the special mechanical behavior of 3D printed lattice structures. Therefore, in order to accurately evaluate the tensile properties of 3D printed lattice structures, non-standard tensile specimens that are suitable for them are developed. Non-standard specimens can better simulate the stress state of 3D printed lattices in actual applications, thereby providing a reliable basis for structural optimization and performance improvement.

[0004] However, there are also the following problems in the tensile test of non-standard samples: first, it is difficult to select the test section of non-standard samples, which may not meet the requirements of the gauge length in the standard test method, resulting in errors; second, data acquisition is difficult. Due to the non-uniformity of the lattice structure, the traditional data acquisition system may not be able to accurately capture these changes, resulting in distortion of the test data. At present, the video extensometer and speckle strain measurement (Digital Image Correlation, DIC) method in the field of optical precision measurement can solve the above problems, but the cost is high, the measurement accuracy is highly dependent on the equipment, and the operation process is long. The present invention proposes a strain test device and method for 3D printing non-standard samples, which has the obvious advantages of low cost, reliable measurement, and easy implementation. Summary of the invention

[0005] The purpose of the present invention is to provide a strain testing device and method for 3D printing non-standard specimens in view of the deficiencies in the prior art.

[0006] The objective of the present invention is achieved through the following technical solutions: In a first aspect, an embodiment of the present invention provides a strain testing device for 3D printing non-standard specimens, comprising: Two tensile specimen ends; A tensile specimen dot matrix section is arranged between two ends of the tensile specimen; Two connecting platforms are arranged on the end of the tensile specimen, the connecting platforms are located in the middle of the width direction of the end of the tensile specimen, and two circular bosses are arranged on the connecting platforms; two measuring plates, one end of each measuring plate being bound to two bosses provided on the connecting platform, and the other ends of each measuring plate being overlapped with each other; and The contact extensometer has its two ends clamped at the other ends of the two measuring plates.

[0007] Furthermore, the end of the tensile specimen is provided with a clamping end and a platform mounting portion, and the connecting platform is arranged on the platform mounting portion so that there is no interference area between the connecting platform and the clamping end.

[0008] Furthermore, the binding between the measuring plate and the boss is firm and reliable, which is achieved by a self-locking cable tie or a mechanical connection.

[0009] Further, when the measuring plate and the boss are bound by a self-locking cable tie, each cable tie is fixed above each boss, and the cable tie is tightened to a maximum tightness to connect one end of the measuring plate to the connecting platform; or When the measuring plate and the boss are bound by mechanical connection, the boss is a threaded hole, and a screw is inserted into the threaded hole and tightened to connect one end of the measuring plate to the connecting platform.

[0010] Furthermore, the two measuring plates are an upper measuring plate and a lower measuring plate, respectively, wherein one end of the upper measuring plate is provided with a first through slot and the other end is provided with an elastic end; one end of the lower measuring plate is provided with a second through slot; The first through slot is sleeved on two bosses provided on one connecting platform, the second through slot is sleeved on two bosses provided on another connecting platform, and the elastic end is overlapped on the other end of the lower measuring plate so that the other end of the upper measuring plate is overlapped on the other end of the lower measuring plate.

[0011] Further, the width of the first through groove and the width of the second through groove are the same as the diameter of the boss.

[0012] Furthermore, the height of the connection platform relative to the tensile specimen array segment is 5 to 15 mm; The thickness of the measuring plate is 1 mm to 1.5 mm; The height of the boss is 1.5 to 2 times the thickness of the measuring plate; The overlap length of the two measuring plates is 5-10 mm; The surface roughness of the connecting platform is greater than or equal to Ra3.2; The material of the measuring plate is structural steel.

[0013] Furthermore, the contact extensometer is provided with an upper clamping piece and a lower clamping piece, the upper clamping piece is clamped on the elastic end of the upper measuring plate, and the lower clamping piece is clamped on an end of the lower measuring plate away from the second through slot.

[0014] Furthermore, the distance between the end surfaces of the upper clamping piece and the lower clamping piece that are separated from each other is 20-40 mm.

[0015] A second aspect of an embodiment of the present invention provides a strain testing method for the strain testing device for 3D printing non-standard specimens, comprising the following steps: S1. Compare the relative sizes of the width direction and thickness direction of the 3D printed non-standard sample, and determine the direction corresponding to the larger size as the final width direction; wherein the 3D printed non-standard sample includes two tensile sample ends and a tensile sample dot matrix segment arranged between the two tensile sample ends; S2, based on the final width direction determined in step S1, a connection platform is provided at the middle position in the width direction of each tensile specimen end; S3, two circular bosses are arranged on each connecting platform, and the coordinates of the centers of the two bosses are the same in the width direction; S4. Two measuring plates are provided, one end of the two measuring plates is connected to the two connecting platforms respectively, and the other ends of the two measuring plates are overlapped with each other; S5. Bind one end of the measuring plate to the boss on the connecting platform and clamp the contact extensometer on the other end; S6, clamping the 3D printed non-standard specimen, clamping the contact extensometer, stretching the 3D printed non-standard specimen, and detecting its tensile strain; S7. Calculate the equivalent strain of the 3D printed non-standard specimen based on the measurement value of the contact extensometer.

[0016] The beneficial effects of the present invention are as follows: the present invention provides a connecting platform and a measuring plate on a non-standard specimen, and measures the deformation of the measuring area of ​​the dot matrix by measuring the relative displacement of the upper and lower measuring plates, thereby realizing the measurement of the equivalent strain of the non-standard tensile specimen; the measurement cost of the present invention is reduced by more than 50% compared with the measurement cost of the existing video extensometer method, and the measurement time of the present invention is reduced by 90% compared with the measurement time of the existing DIC method (including pre-processing and post-processing time of video images), and the measurement accuracy of the present invention can reach the accuracy of the contact extensometer, which is the strain value. The present invention realizes the measurement of tensile strain of non-standard samples with low cost, high efficiency and high precision. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overall structure of the strain testing device for 3D printing non-standard specimens of the present invention; Figure 2 is a partial enlarged view of the strain testing device of the present invention; Figure 3 is a top view of the strain testing device of the present invention; Figure 4 It is a schematic structural diagram of the strain testing device of the present invention in the thickness direction of the sample; Figure 5 It is a partial enlarged view of the strain testing device of the present invention in the thickness direction of the sample.

[0018] In the figure, the tensile specimen end 1, the clamping end 1-1, and the platform mounting portion 1-2; Tensile specimen lattice segment 2; Connecting platform 3 and boss 3-1; Measuring plate 4, upper measuring plate 4-1, first through slot 4-1-1, elastic end 4-1-2, lower measuring plate 4-2, second through slot 4-2-1; Contact extensometer 5, upper clamping piece 5-1, lower clamping piece 5-2. DETAILED DESCRIPTION

[0019] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are merely examples of devices and methods consistent with some aspects of the present invention as detailed in the appended claims.

[0020] The terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The singular forms "a", "the" and "the" used in the present invention and the appended claims are also intended to include plural forms unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0021] It should be understood that although the terms first, second, third, etc. may be used in the present invention to describe various information, these information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present invention, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining".

[0022] The present invention is described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the features of the following embodiments and implementations can be combined with each other.

[0023] There are two difficulties in testing 3D printed dot matrix non-standard samples: one is the uneven deformation. The deformation of each section of the sample along the length direction is different due to the difference in material distribution, and the measurement interval of the ordinary contact extensometer is fixed and short (generally 20mm), which cannot cover the entire measurement area of ​​the non-standard sample; the second is that the cross-sectional area of ​​the sample is large, and the clamping distance of the extensometer is limited, resulting in the extensometer being unable to clamp the sample smoothly. The strain testing device and method for 3D printed non-standard samples of the present invention transfers the measurement of the deformation of the sample dot matrix area to the measurement of the relative displacement of the upper and lower measuring plates by setting a measuring plate with a thickness of 1mm~2mm. In this way, only the relative displacement of the two measuring plates can be measured to determine the total deformation of the entire dot matrix area, thereby realizing low-cost, high-efficiency and high-precision measurement of the tensile strain of non-standard samples.

[0024] like Figure 1 and Figure 2 As shown, the strain testing device for 3D printing non-standard specimens of the present invention specifically includes two tensile specimen ends 1, a tensile specimen lattice segment 2, two connecting platforms 3, two measuring plates 4 and a contact extensometer 5, wherein the tensile specimen lattice segment 2 is arranged between the two tensile specimen ends 1; the connecting platform 3 is arranged on the tensile specimen end 1, the connecting platform 3 is located in the middle position in the width direction of the tensile specimen end 1, and two circular bosses 3-1 are arranged on the connecting platform 3; one end of the measuring plate 4 is bound to the two bosses 3-1 arranged on the connecting platform 3, and the other ends of the two measuring plates 4 are overlapped with each other; the two ends of the contact extensometer 5 are clamped at the other ends of the two measuring plates 4.

[0025] In this embodiment, the connection platform 3 cannot interfere with the upper and lower clamping areas of the sample, and the connection platform 3 can keep a distance of 2mm to 8mm from the upper and lower clamping areas of the sample. Therefore, it is defined that the tensile sample end 1 is provided with a clamping end 1-1 and a platform mounting portion 1-2, and the connection platform 3 is arranged on the platform mounting portion 1-2 so that there is no interference area between the connection platform 3 and the clamping end 1-1. That is, when the tensile machine clamps the sample, the tensile machine needs to clamp the clamping ends 1-1 of the two tensile sample ends 1, so that the two connection platforms 3 on the sample cannot have an interference area with the clamping ends 1-1 clamped by the tensile machine.

[0026] Furthermore, the height of the connecting platform 3 relative to the tensile specimen lattice segment 2 is 5-15 mm, that is, the height of the connecting platform 3 relative to the tensile specimen lattice segment 2 should not be less than 5 mm, and its upper limit is generally 15 mm.

[0027] In this embodiment, the binding of the measuring plate 4 and the boss 3 - 1 is firm and reliable, which is achieved by a self-locking cable tie or a mechanical connection, and does not affect the measurement of the contact extensometer 3 at the lower end.

[0028] Specifically, when the measuring plate 4 and the boss 3-1 are bound by a self-locking tie, each tie is fixed above each boss 3-1, and the tie is tightened to the maximum tightness to connect one end of the measuring plate 4 to the connecting platform 3. When the measuring plate 4 and the boss 3-1 are bound by a mechanical connection, the boss 3-1 is a threaded hole, and a screw is inserted into the threaded hole and tightened to connect one end of the measuring plate 4 to the connecting platform 3.

[0029] In this embodiment, the two measuring plates 4 are an upper measuring plate 4-1 and a lower measuring plate 4-2, wherein one end of the upper measuring plate 4-1 is provided with a first through slot 4-1-1, and the other end is provided with an elastic end 4-1-2; one end of the lower measuring plate 4-2 is provided with a second through slot 4-2-1, such as Figure 2 The first through slot 4-1-1 is sleeved on two bosses 3-1 provided on one connecting platform 3, the second through slot 4-2-1 is sleeved on two bosses 3-1 provided on another connecting platform 3, and the elastic end 4-1-2 is overlapped on the other end of the lower measuring plate 4-2, so that the other end of the upper measuring plate 4-1 is overlapped on the other end of the lower measuring plate 4-2, as shown. Figure 5The existence of the first through slot 4-1-1 and the second through slot 4-2-1 allows the measuring plate 4 to be pulled toward the measuring area when the sample is long, and vice versa, the measuring plate 4 can be pushed out of the pushing area when the sample is short. Specifically, the upper measuring plate 4-1 and the lower measuring plate 4-2 are fixed to the boss 3-1 of the connecting platform 3, and then the upper measuring plate 4-1 and the lower measuring plate 4-2 move relative to each other when the sample is stretched, and the contact extensometer 5 clamped between the upper measuring plate 4-1 and the lower measuring plate 4-2 measures the relative movement, and then converts the equivalent strain of the 3D printed non-standard sample.

[0030] Furthermore, the width of the first through groove 4-1-1 and the width of the second through groove 4-2-1 are the same as the diameter of the boss 3-1.

[0031] Furthermore, the thickness of the measuring plate 4 is 1 mm to 1.5 mm; the height of the boss 3 - 1 is 1.5 to 2 times the thickness of the measuring plate 4 .

[0032] Furthermore, the overlapping length of the two measuring plates 4 is 5-10 mm, that is, the overlapping length of the two measuring plates 4 is greater than or equal to 5 mm, and the overlapping length of the two measuring plates 4 is less than or equal to 10 mm.

[0033] Furthermore, the surface roughness of the connecting platform 3 is greater than or equal to Ra3.2; the material of the measuring plate 4 is structural steel, and the so-called structural steel, as the name implies, is steel mainly used to form a structure.

[0034] Furthermore, the coordinates of the centers of the two bosses 3 - 1 provided on the two connecting platforms 3 are the same in the width direction.

[0035] In this embodiment, the contact extensometer 5 is provided with an upper clamping piece 5-1 and a lower clamping piece 5-2. The upper clamping piece 5-1 is clamped on the elastic end 4-1-2 of the upper measuring plate 4-1, and the lower clamping piece 5-2 is clamped on the end of the lower measuring plate 4-2 away from the second through groove 4-2-1. Figure 4 shown.

[0036] Furthermore, the minimum distance between the two end faces of the contact extensometer 5 should not be less than 20 mm, and its upper limit is 40 mm, that is, the distance between the end faces of the upper clamping piece 5-1 and the lower clamping piece 5-2 that are far away from each other is 20-40 mm. Figure 3 shown.

[0037] It is worth mentioning that an embodiment of the present invention further provides a strain testing method for the strain testing device for 3D printing non-standard specimens of the above embodiment, which specifically includes the following steps: S1. Compare the relative sizes of the width direction and thickness direction of the 3D printed non-standard sample, and determine the direction corresponding to the larger size as the final width direction. The 3D printed non-standard sample includes two tensile sample ends 1 and a tensile sample dot matrix segment 2 arranged between the two tensile sample ends 1.

[0038] S2. Based on the final width direction determined in step S1, a connecting platform 3 is provided at the middle position in the width direction of each tensile specimen end 1.

[0039] S3. Two circular bosses 3-1 are arranged on each connecting platform 3, and the coordinates of the centers of the two bosses 3-1 are the same in the width direction.

[0040] S4. Two measuring plates 4 are provided, one end of the two measuring plates 4 is connected to the two connecting platforms 3 respectively, and the other ends of the two measuring plates 4 are overlapped with each other.

[0041] S5. Bind one end of the measuring plate 4 to the boss 3 - 1 on the connecting platform 3 , and clamp the contact extensometer 5 at the other end.

[0042] S6, clamping the 3D printed non-standard sample, clamping the contact extensometer 5, stretching the 3D printed non-standard sample, and detecting its tensile strain.

[0043] Specifically, a stretching machine can be used to clamp the 3D printed non-standard sample, that is, the stretching machine clamps the clamping ends 1-1 of the two tensile sample ends 1, and then the 3D printed non-standard sample is stretched, and the two measuring plates 4 will produce relative displacement, and the tensile strain of the 3D printed non-standard sample is equivalently measured by the relative displacement generated by the two measuring plates 4. Among them, the contact extensometer 5 and the stretching machine should be equipped with auxiliary devices such as a synchronization box to ensure that the measurement data of the two are strictly synchronized.

[0044] S7. Calculate the equivalent strain of the 3D printed non-standard specimen according to the measurement value of the contact extensometer 5.

[0045] It should be understood that the equivalent strain of the 3D printed non-standard sample can be calculated based on the measurement value of the contact extensometer 5, that is, the deformation measured by the contact extensometer 5 is divided by the original length of the 3D printed non-standard sample to obtain the equivalent strain of the 3D printed non-standard sample.

[0046] In summary, the present invention adopts an alternative method to solve the problem that the strain of the dot matrix area cannot be directly measured for non-standard dot matrix samples. The features of the present invention specifically include: 1. Strong compatibility and good generalization: For non-standard samples of different sizes, it can be applied as long as the basic conditions are met; 2. Low cost: Compared with precision optical measurement, the cost of the present invention is more than 50% lower. This is because optical precision measurement requires the use of high-precision optical measurement equipment, such as video extensometers, DIC measuring instruments, etc., and the cost of using the instruments is high; 3. Short measurement time: Compared with optical measurement methods such as video extensometers and DIC, the present invention eliminates the workload of spraying marking points in the pre-processing link and image calculation processing in the post-processing link. It is directly measured by a clamp-type extensometer, and the results are output synchronously with the force data of the stretching machine. The measurement time is more than 90% less than that of DIC; 4. High measurement accuracy: When measured by a clamp-type extensometer, the device described in the present invention is reliably connected, so the measurement accuracy of the clamp-type extensometer is the accuracy of the method described in the present invention, which is the strain value. .

[0047] The above is only a preferred implementation case of the present invention and does not limit the present invention in any form. Although the implementation process of the present invention is described in detail above, for those familiar with the art, they can still modify the technical solutions recorded in the above examples, or replace some of the technical features therein with equivalents. All modifications, equivalent replacements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A strain testing device for 3D printing non-standard specimens, characterized in that: include: Two tensile test specimen ends (1); A tensile specimen dot matrix section (2) is arranged between the two tensile specimen ends (1); Two connecting platforms (3) are arranged on the end of the tensile specimen (1), the connecting platform (3) is located at the middle position of the end of the tensile specimen (1) in the width direction, and two circular bosses (3-1) are arranged on the connecting platform (3); Two measuring plates (4), one end of each measuring plate (4) being bound to two bosses (3-1) provided on the connecting platform (3), and the other ends of each measuring plate (4) being overlapped with each other; and The two ends of the contact extensometer (5) are clamped on the other ends of the two measuring plates (4).

2. The strain testing device for 3D printing non-standard specimens according to claim 1, characterized in that: The tensile specimen end (1) is provided with a clamping end (1-1) and a platform mounting portion (1-2), and the connecting platform (3) is arranged on the platform mounting portion (1-2) so that there is no interference area between the connecting platform (3) and the clamping end (1-1).

3. The strain testing device for 3D printing non-standard specimens according to claim 1, characterized in that: The binding of the measuring plate (4) and the boss (3-1) is firm and reliable, and is achieved by means of a self-locking cable tie or a mechanical connection.

4. The strain testing device for 3D printing non-standard specimens according to claim 3, characterized in that: When the measuring plate (4) and the boss (3-1) are bound together by means of a self-locking cable tie, each cable tie is fixed above each boss (3-1), and the cable tie is tightened to a maximum tightness to connect one end of the measuring plate (4) to the connecting platform (3); or When the measuring plate (4) and the boss (3-1) are bound together by means of mechanical connection, the boss (3-1) is a threaded hole, and a screw is inserted into the threaded hole and tightened to connect one end of the measuring plate (4) to the connecting platform (3).

5. The strain testing device for 3D printing non-standard specimens according to claim 1, characterized in that: The two measuring plates (4) are respectively an upper measuring plate (4-1) and a lower measuring plate (4-2), wherein one end of the upper measuring plate (4-1) is provided with a first through slot (4-1-1) and the other end is provided with an elastic end (4-1-2); one end of the lower measuring plate (4-2) is provided with a second through slot (4-2-1); The first through groove (4-1-1) is sleeved on two bosses (3-1) provided on one connecting platform (3), the second through groove (4-2-1) is sleeved on two bosses (3-1) provided on another connecting platform (3), and the elastic end (4-1-2) is overlapped on the other end of the lower measuring plate (4-2), so that the other end of the upper measuring plate (4-1) is overlapped on the other end of the lower measuring plate (4-2).

6. The strain testing device for 3D printing non-standard specimens according to claim 5, characterized in that: The width of the first through groove (4-1-1) and the width of the second through groove (4-2-1) are the same as the diameter of the boss (3-1).

7. The strain testing device for 3D printing non-standard specimens according to claim 1, characterized in that: The height of the connecting platform (3) relative to the tensile specimen dot matrix segment (2) is 5 to 15 mm; The thickness of the measuring plate (4) is 1 mm to 1.5 mm; The height of the boss (3-1) is 1.5 to 2 times the thickness of the measuring plate (4); The overlapping length of the two measuring plates (4) is 5 to 10 mm; The surface roughness of the connecting platform (3) is greater than or equal to Ra3.2; The material of the measuring plate (4) is structural steel.

8. The strain testing device for 3D printing non-standard specimens according to claim 1, characterized in that: The contact extensometer (5) is provided with an upper clamping piece (5-1) and a lower clamping piece (5-2), wherein the upper clamping piece (5-1) is clamped on the elastic end (4-1-2) of the upper measuring plate (4-1), and the lower clamping piece (5-2) is clamped on an end of the lower measuring plate (4-2) away from the second through slot (4-2-1).

9. The strain testing device for 3D printing non-standard specimens according to claim 8, characterized in that: The distance between the end surfaces of the upper clamping piece (5-1) and the lower clamping piece (5-2) that are separated from each other is 20 to 40 mm.

10. A strain testing method for a strain testing device for 3D printing non-standard specimens according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. Comparing the relative sizes of the width direction and thickness direction of the 3D printed non-standard sample, and determining the direction corresponding to the larger dimension as the final width direction; wherein the 3D printed non-standard sample comprises two tensile sample ends (1) and a tensile sample dot matrix segment (2) arranged between the two tensile sample ends (1); S2, based on the final width direction determined in step S1, a connection platform (3) is provided at the middle position in the width direction of each tensile specimen end (1); S3, two circular bosses (3-1) are arranged on each connecting platform (3), and the coordinates of the centers of the two bosses (3-1) are the same in the width direction; S4, two measuring plates (4) are provided, one end of the two measuring plates (4) is connected to the two connecting platforms (3) respectively, and the other ends of the two measuring plates (4) are overlapped with each other; S5, one end of the measuring plate (4) is bound to the boss (3-1) on the connecting platform (3), and the other end is clamped with the contact extensometer (5); S6, clamping the 3D printed non-standard sample, clamping the contact extensometer (5), stretching the 3D printed non-standard sample, and detecting the tensile strain thereof; S7. Calculate the equivalent strain of the 3D printed non-standard specimen based on the measurement value of the contact extensometer (5).

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