Dynamic compression-shear experimental device suitable for soft material and experimental method thereof

Abstract

The invention discloses a dynamic compression-shear experimental device suitable for a soft material and an experimental method thereof. The experimental device comprises an incident bar and a transmission bar which are arranged at an interval, and a load conversion piece arranged between the incident bar and the transmission bar, a mounting gap for placing a tested piece is formed between the load conversion piece and the transmission rod; wherein the first panel and the second panel are arranged in parallel and coaxially, the elastic columns are arranged between the first panel and the second panel in an inclined mode, the brim is arranged on the edge of the second panel and extends towards the direction of the first panel, and the brim is arranged in an annular mode. The dynamic compression-shear experiment device suitable for the soft material is good in composite load synchronization effect, low in cost and easy to implement, the load conversion piece can generate large compression and torsional deformation under the action of compression load, and a dynamic compression-shear loading experiment for the soft material is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of mechanical property experiments, and more specifically to a dynamic compression-shearing experimental device suitable for soft materials and an experimental method thereof. Background Art

[0002] With the development of material science and technology, artificial soft materials with elastic modulus below 1MPa have been rapidly developed and applied in medical, robotics, flexible electronics and other fields. Therefore, it is particularly important to have a deep understanding of the mechanical properties of these materials, especially the critical stress value of failure. At the same time, the human body itself has many different soft tissues, accounting for about 70% of the human body mass. A deep understanding of the mechanical response of these soft tissues under impact loads is of particular significance for human protection and treatment research. Considering the actual situation, compared with simple compression loads, soft materials or soft tissues are more likely to be damaged by compression-shear composite loads. Therefore, it is necessary to experimentally test the mechanical response of these soft materials and soft tissues under dynamic compression-shear loads in order to better understand their mechanical behavior characteristics. However, the current dynamic compression-shear composite loading experimental technology is not suitable for soft materials / soft tissues, which limits the implementation of experimental research. Summary of the invention

[0003] The present invention aims to overcome at least one defect of the above-mentioned prior art and provide a dynamic compression-shear experimental device and an experimental method suitable for soft materials, so as to solve the problem that the current dynamic compression-shear composite loading experimental technology is not suitable for soft materials / soft tissues, which limits the implementation of experimental research.

[0004] The technical solution adopted by the present invention is as follows:

[0005] A dynamic compression-shear test device suitable for soft materials comprises: an incident rod and a transmission rod arranged at intervals, and a load conversion member arranged between the incident rod and the transmission rod; an installation gap for placing a test piece is arranged between the load conversion member and the transmission rod; wherein the load conversion member comprises a first panel and a second panel arranged in parallel and coaxially, a plurality of elastic columns obliquely arranged between the first panel and the second panel, and a brim arranged at the edge of the second panel and extending toward the first panel, wherein the brim is arranged in a ring shape; and the installation gap is arranged between the second panel and the transmission rod.

[0006] In one embodiment, the first panel and the second panel are both circular, and the diameter of the first panel is smaller than the diameter of the second panel; the thickness of the brim is the difference between the radius of the second panel and the radius of the first panel.

[0007] In one embodiment, the diameters, lengths and inclination angles of the plurality of elastic columns are the same.

[0008] In one embodiment, the plurality of elastic columns are evenly spaced and distributed along the circumference of the first panel and the second panel.

[0009] In one embodiment, the plurality of elastic columns are inscribed inwardly with the outer contour of the first panel.

[0010] In one embodiment, the incident rod and the transmission rod are polycarbonate rods; and the load conversion member is a thermoplastic polyurethane elastic member.

[0011] In one embodiment, the number of the elastic columns is 6-10; and / or the distance between the first panel and the second panel is in the range of 8mm-12mm; and / or the diameter of the elastic columns is in the range of 2mm-4mm; and / or the length of the brim is in the range of 5mm-10mm.

[0012] The technical solution also provides a dynamic compression-shear test method applicable to soft materials, and the test method is applied to the dynamic compression-shear test device applicable to soft materials as described in any of the above items.

[0013] In one embodiment, the steps include:

[0014] A layer of speckle is arranged on the outer wall of the incident rod, the transmission rod and the brim;

[0015] Place the tested piece into the installation gap;

[0016] The axial displacement U of the load converter is obtained by using the speckle pattern on the outer wall of the brim and combining DIC technology. ct and longitudinal displacement V ct ;

[0017] The axial displacement U of the transmission rod is obtained by using the speckle pattern on the outer wall of the transmission rod and combining the DIC technique. t and longitudinal displacement V t ;

[0018] The nominal normal strain of the test piece is obtained as (U ct -U t ) / l 0 , where l 0 is the initial height of the tested piece;

[0019] The nominal shear strain of the test piece is obtained as where r 0 is the initial radius of the tested piece, and R is the radius of the transmission rod.

[0020] In one embodiment, the following steps are also included:

[0021] Paste the strain gauge on the transmission rod; obtain the stress σ of the test piece near the end of the transmission rod based on the signal captured by the strain gauge and the material mechanical parameters of the transmission rod. 1 ;

[0022] Using the speckle pattern on the outer wall of the incident rod and the DIC technique, the axial displacement of the incident rod is obtained as Ui, and the axial deformation of the load conversion component is U i -U ct ;

[0023] According to the force-deformation curve of the load converter, the force corresponding to the axial deformation of the load converter is F, and the nominal stress of the test piece close to the load converter is

[0024] According to σ 1 and σ 2 The value of is used to determine whether stress balance is achieved at both ends of the test piece.

[0025] Compared with the prior art, the beneficial effects of the present invention include at least:

[0026] This technical solution is suitable for the dynamic compression-shear test device of soft materials, with good composite load synchronization effect, low cost and easy implementation. Under the action of compression load, the load conversion part can undergo large compression and torsional deformation, realizing the dynamic compression-shear loading test for soft materials. During the experimental test, the compressive stress is transmitted from the incident rod, and the load conversion part simultaneously produces compression and torsional deformation due to the compressive stress, and due to the low stiffness of the load conversion part, the compression and torsional deformation are large. Since the load conversion part includes a first panel and a second panel arranged in parallel and coaxially, and a plurality of elastic columns inclined between the first panel and the second panel, the compressive stress is converted into a compression-shear composite stress by the load conversion part, and synchronously transmitted to the test piece, so that it undergoes synchronous compression and torsional deformation, and the deformation is large, meeting the mechanical experimental requirements of soft materials. One end of the brim is connected to the second panel, and the other end is free. Its axial displacement and rotation angle are the same as the second panel, which is also the end face of the test piece close to the load conversion part when being tested. By setting speckles on the incident rod, the transmission rod and the outer wall of the brim of the load conversion component, the deformation response of the test piece can be obtained in combination with the DIC technology.

[0027] This technical solution is applicable to the dynamic compression-shear test method of soft materials and is applied to the above-mentioned dynamic compression-shear test device applicable to soft materials. The deformation of the tested piece is obtained by combining the speckle on the load conversion piece and the transmission rod with the DIC technology, and the stress at both ends of the tested piece can be obtained by respectively measuring the deformation of the load conversion piece and the transmission rod. The deformation of the load conversion piece is obtained by combining the speckle on the load conversion piece and the incident rod with the DIC technology, and the deformation of the transmission rod is obtained by the strain gauge attached thereto. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic structural diagram of a dynamic compression-shear experimental device suitable for soft materials according to an embodiment of the present invention.

[0029] Figure 2 A perspective view of a dynamic compression-shear test apparatus suitable for soft materials according to an embodiment of the present invention.

[0030] Figure 3 It is a cross-sectional view of a dynamic compression-shear test device suitable for soft materials according to an embodiment of the present invention.

[0031] Figure 4 A schematic diagram of the structure of setting speckle in a dynamic compression-shear experimental device suitable for soft materials according to an embodiment of the present invention.

[0032] Figure numerals: 10, incident rod; 20, transmission rod; 30, load conversion member; 31, first panel; 32, second panel; 33, elastic column; 34, brim; 40, tested member. DETAILED DESCRIPTION

[0033] The drawings of the present invention are only for illustrative purposes and should not be construed as limiting the present invention. In order to better illustrate the following embodiments, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; it is understandable to those skilled in the art that some well-known structures and their descriptions in the drawings may be omitted. Example 1

[0034] like Figure 1-Figure 3 As shown, a dynamic compression-shear test device suitable for soft materials comprises: an incident rod 10 and a transmission rod 20 arranged at intervals, and a load conversion member 30 arranged between the incident rod 10 and the transmission rod 20; an installation gap for placing a test piece 40 is arranged between the load conversion member 30 and the transmission rod 20; wherein the load conversion member 30 comprises a first panel 31 and a second panel 32 arranged in parallel and coaxially, a plurality of elastic columns 33 arranged obliquely between the first panel 31 and the second panel 32, and a brim 34 arranged at the edge of the second panel 32 and extending toward the first panel 31, wherein the brim 34 is arranged in a ring shape; and the installation gap is arranged between the second panel 32 and the transmission rod 20.

[0035] This embodiment is suitable for the dynamic compression-shear test device of soft materials, and has good composite load synchronization effect, low cost, and easy implementation. Under the action of the compression load, the load conversion member 30 can undergo large compression and torsional deformation, thereby realizing the dynamic compression-shear loading test for soft materials. During the experimental test, the compressive stress is transmitted from the incident rod 10, and the load conversion member 30 simultaneously produces compression and torsional deformation due to the compressive stress, and due to the low rigidity of the load conversion member 30, the compression and torsional deformation are both large. Since the load conversion member 30 includes a first panel 31 and a second panel 32 arranged in parallel and coaxially, and a plurality of elastic columns 33 obliquely arranged between the first panel 31 and the second panel 32, the compressive stress is converted into a compression-shear composite stress by the load conversion member 30, and synchronously transmitted to the test piece 40, so that it undergoes synchronous compression and torsional deformation, and the deformation is large, which meets the mechanical experimental requirements of soft materials. One end of the brim 34 is connected to the second panel 32, and the other end is free, and its axial displacement and rotation angle are the same as the second panel 32, which is also the end face of the test piece 40 close to the load conversion member 30. By setting speckles on the incident rod 10 , the transmission rod 20 and the outer wall of the brim 34 of the load conversion member 30 , the deformation response of the test piece 40 can be obtained in combination with the DIC technology.

[0036] In this embodiment, the first panel 31 and the second panel 32 are both circular, and the diameter of the first panel 31 is smaller than the diameter of the second panel 32; the thickness of the brim 34 is the difference between the radius of the second panel 32 and the radius of the first panel 31. That is, the outer diameter of the brim 34 is the same as that of the second panel 32, and the inner diameter of the brim 34 is the same as that of the first panel 31. Therefore, during the experiment, when the load conversion member 30 is compressed, it can be ensured that the brim 34 will not touch the elastic column 33, the first panel 31 and the incident rod 10 during the pressure loading process, and at the same time, the second panel 32 and the brim 34 will not shake, thereby ensuring the stability and reliability of the experimental process.

[0037] In this embodiment, the diameters, lengths and inclination angles of the plurality of elastic columns 33 are all the same, so that the compression and torsional deformation of the load conversion member 30 due to the compressive stress is more uniform.

[0038] Similarly, the plurality of elastic columns 33 are evenly spaced and distributed along the circumferential direction of the first panel 31 and the second panel 32 , so that the compression and torsional deformation of the load conversion member 30 are more uniform.

[0039] In this embodiment, the plurality of elastic columns 33 are all inscribed in the outer contour of the first panel 31 , that is, the diameter of the circumscribed circle of the elastic column 33 on the first panel 31 is the same as the diameter of the first panel 31 and is coaxial.

[0040] In this embodiment, the incident rod 10 and the transmission rod 20 are polycarbonate rods; the load conversion member 30 is a thermoplastic polyurethane elastic member, that is, the first panel 31, the second panel 32 and the elastic column 33 are all made of thermoplastic polyurethane.

[0041] In this embodiment, the number of elastic columns 33 is 6-10; the diameter range of the incident rod 10 and the transmission rod 20 is 15mm-25mm; the distance range of the first panel 31 and the second panel 32 is 8mm-12mm; the diameter range of the elastic column 33 is 2mm-4mm; the length range of the brim 34 is 5mm-10mm. By changing the number, diameter, length and tilt angle of the elastic columns 33 in the load conversion member 30, the ratio of the compressive stress and the shear stress applied to the test piece 40 can be changed, so that the normal stress and the shear stress values ​​of the test piece 40 under various load conditions can be obtained, and more experimental data can be obtained.

[0042] This embodiment also provides a dynamic compression-shear test method applicable to soft materials, and the test method is applied to the dynamic compression-shear test device applicable to soft materials as described above.

[0043] The dynamic compression-shear test method for soft materials in this embodiment is applied to the above-mentioned dynamic compression-shear test device for soft materials. The deformation of the test piece 40 is obtained by measuring the speckle on the load conversion member 30 and the transmission rod 20 in combination with the DIC technology, and the stress at both ends of the test piece 40 can be obtained by measuring the deformation of the load conversion member 30 and the transmission rod 20 respectively.

[0044] Specifically, this embodiment conducts experiments with a set of parameters: the thickness of the first panel 31 and the second panel 32 are both 1 mm, the number of elastic columns 33 is 8, the diameter of the elastic column 33 is 3 mm, the distance between the first panel 31 and the second panel 32 is 10 mm, and the length of the brim 34 is 7 mm.

[0045] This implementation method includes the following steps:

[0046] like Figure 4 As shown, a layer of speckle is provided on the outer wall of the incident rod 10, the transmission rod 20 and the brim 34;

[0047] Put the tested piece 40 into the installation gap, and bond the tested piece 40 to the second panel 32 and the transmission rod 20;

[0048] The axial displacement U of the load conversion member 30 is obtained by using the speckle pattern of the outer wall of the brim 34 and combining the DIC technology. ct and longitudinal displacement V ct ;

[0049] The axial displacement U of the transmission rod 20 is obtained by using the speckle pattern on the outer wall of the transmission rod 20 in combination with the DIC technology. t and longitudinal displacement V t ;

[0050] The nominal normal strain of the test piece 40 is obtained as (U ct -U t ) / l 0 , where l 0 is the initial height of the tested piece 40;

[0051] The nominal shear strain of the test piece 40 is obtained as where r 0 is the initial radius of the tested piece 40 , and R is the radius of the transmission rod 20 .

[0052] During the experiment, the compression stress wave is input into the incident rod 10 and propagates along the incident rod 10. After reaching the load conversion member 30, the load conversion member 30 generates both compression and torsion deformations under the action of the compression load, converting the compression stress into a compression-shear composite stress, and transmitting it to the test piece 40 bonded to the second panel 32, so that the test piece 40 generates both compression and torsion deformations at the same time. Subsequently, the compression-shear composite stress is transmitted to the transmission rod 20 through the test piece 40. The nominal normal strain and nominal shear strain of the test piece 40 are obtained by combining the speckle on the brim 34 of the load conversion member 30 and the transmission rod 20 with the DIC technology.

[0053] This embodiment also includes the following steps:

[0054] A strain gauge is attached to the transmission rod 20; in this embodiment, the strain gauge is attached to the middle position of the transmission rod 20, and the stress σ of the test piece 40 near the end of the transmission rod 20 is obtained according to the signal captured by the strain gauge and the material mechanical parameters of the transmission rod 20. 1 ;

[0055] Using the speckle pattern of the outer wall of the incident rod 10 and the DIC technology, the axial displacement of the incident rod 10 is obtained as Ui, and the axial deformation of the load conversion member 30 is U i -U ct ;

[0056] According to the force-deformation curve of the load conversion member 30, the force corresponding to the axial deformation of the load conversion member 30 is obtained as F, and the nominal stress of the test piece 40 close to the end of the load conversion member 30 is

[0057] According to σ 1 and σ 2The value of is used to judge whether the stress balance is achieved at both ends of the test piece, which is a dynamic mechanical performance test requirement; if stress balance is not achieved, it can be improved by reducing the thickness of the test piece.

[0058] The normal stress and shear stress of the test piece 40 of this embodiment can be obtained by the strain gauge attached to the transmission rod 20. Under the premise that the material mechanical parameters of the transmission rod 20 are known, the stress of the interface of the test piece 40 close to the transmission rod 20 can be inferred through the deformation of the transmission rod 20. In addition, under the premise that the force-deformation curve of the load conversion member 30 is known, the stress of the end face of the test piece 40 close to the load conversion member 30 can be inferred through the deformation of the load conversion member 30, thereby verifying whether the stress balance is achieved at both ends of the test piece 40. The deformation of the load conversion member 30 can be obtained by combining the speckle of the incident rod 10 and the outer wall of the brim 34 of the load conversion member 30 with the DIC technology. Example 2

[0059] The structure and principle of the embodiment are similar to those of the embodiment 1, except that the relevant parameters of the load conversion member 30 of the embodiment are different from those of the embodiment 1. Specifically, the thickness of the first panel 31 of the embodiment is 1 mm, the thickness of the second panel 32 is 2 mm, the number of elastic columns 33 is 6, the diameter of the elastic columns 33 is 2.8 mm, the distance between the first panel 31 and the second panel 32 is 10 mm, and the length of the brim 34 is 7 mm. Example 2

[0060] The structure and principle of the embodiment are similar to those of the embodiment 1 and the embodiment 2, except that the relevant parameters of the load conversion member 30 of the embodiment are different from those of the embodiment 1 and the embodiment 2. Specifically, the thickness of the first panel 31 of the embodiment is 1 mm, the thickness of the second panel 32 is 2 mm, the number of elastic columns 33 is 8, the diameter of the elastic column 33 is 2.6 mm, the distance between the first panel 31 and the second panel 32 is 10 mm, and the length of the brim 34 is 6 mm.

[0061] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solution of the present invention, and are not intended to limit the specific implementation methods of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the claims of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A dynamic compression-shear test device suitable for soft materials, characterized in that: include: An incident rod and a transmission rod are arranged at intervals, and a load conversion member is arranged between the incident rod and the transmission rod; an installation gap for placing a test piece is arranged between the load conversion member and the transmission rod; wherein the load conversion member includes a first panel and a second panel arranged in parallel and coaxially, a plurality of elastic columns obliquely arranged between the first panel and the second panel, and a brim arranged at the edge of the second panel and extending toward the first panel, the brim being arranged in a ring shape; the installation gap is arranged between the second panel and the transmission rod.

2. The dynamic compression-shear test device suitable for soft materials according to claim 1, characterized in that: The first panel and the second panel are both circular, and the diameter of the first panel is smaller than the diameter of the second panel; the thickness of the brim is the difference between the radius of the second panel and the radius of the first panel.

3. The dynamic compression-shear test device suitable for soft materials according to claim 1, characterized in that: The diameters, lengths and inclination angles of the plurality of elastic columns are all the same.

4. The dynamic compression-shear test device for soft materials according to claim 1, characterized in that: The plurality of elastic columns are evenly spaced and distributed along the circumferential direction of the first panel and the second panel.

5. The dynamic compression-shear test device suitable for soft materials according to claim 1, characterized in that: The plurality of elastic columns are all inscribed inwardly with the outer contour of the first panel.

6. The dynamic compression-shear test device for soft materials according to claim 1, characterized in that: The incident rod and the transmission rod are polycarbonate rods; the load conversion component is a thermoplastic polyurethane elastic component.

7. The dynamic compression-shear test device for soft materials according to any one of claims 1 to 6, characterized in that: The number of the elastic columns is 6-10; and / or the distance between the first panel and the second panel is in the range of 8mm-12mm; and / or the diameter of the elastic columns is in the range of 2mm-4mm; and / or the length of the brim is in the range of 5mm-10mm.

8. A dynamic compression-shear test method suitable for soft materials, characterized in that: The experimental method is applied to the dynamic compression-shear experimental device suitable for soft materials as described in any one of claims 1 to 7.

9. The dynamic compression-shear test method applicable to soft materials according to claim 8, characterized in that: The steps include: A layer of speckle is arranged on the outer wall of the incident rod, the transmission rod and the brim; Place the tested piece into the installation gap; The axial displacement U of the load converter is obtained by using the speckle pattern on the outer wall of the brim and combining DIC technology. ct and longitudinal displacement V ct ; The axial displacement U of the transmission rod is obtained by using the speckle pattern on the outer wall of the transmission rod and combining the DIC technique. t and longitudinal displacement V t ; The nominal normal strain of the test piece is obtained as (U ct -U t ) / l0, where l0 is the initial height of the tested piece; The nominal shear strain of the test piece is obtained as Where r0 is the initial radius of the tested piece, and R is the radius of the transmission rod.

10. The dynamic compression-shear test method applicable to soft materials according to claim 9, characterized in that: The following steps are also included: A strain gauge is attached to the transmission rod; based on the signal captured by the strain gauge and the material mechanical parameters of the transmission rod, the stress σ1 of the test piece close to the end of the transmission rod is obtained; Using the speckle pattern on the outer wall of the incident rod and the DIC technique, the axial displacement of the incident rod is obtained as Ui, and the axial deformation of the load conversion component is U i -U ct ; According to the force-deformation curve of the load converter, the force corresponding to the axial deformation of the load converter is F, and the nominal stress of the test piece close to the load converter is According to the values ​​of σ1 and σ2, it is determined whether stress balance is achieved at both ends of the test piece.

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