CN111912700B - A lateral displacement compensation device and method for testing foam shear performance - Google Patents

Abstract

The invention discloses a transverse displacement compensation device for testing the shearing performance of foam, which comprises a force application mechanism, a metal clamping plate and a displacement compensation mechanism, wherein the force application mechanism comprises an upper pressure head, a lower pressure head and a connecting mechanism; the upper pressure head is of an L-shaped structure, one end of the upper pressure head is connected with a connecting rod of the connecting mechanism through a locking nut, and the other end of the upper pressure head is connected with the upper clamping plate through a fixing screw; the connecting mechanism comprises an upper connecting mechanism and a lower connecting mechanism, and a connecting joint of the mechanical testing machine is sleeved at one end of the connecting rod and fixedly connected with the connecting rod through a pin; the other end of the connecting rod is rigidly fixed with the pressure head through a locking nut. The invention solves the problem of inaccurate shear performance test caused by the transverse displacement and tensile stress generated by deformation of semi-rigid and soft foam materials, and improves the accuracy and reliability of test results by using the transverse displacement compensation test device and method for the shear performance of the foam materials.

Description

A lateral displacement compensation device and method for testing foam shear performance

technical field

The invention relates to a lateral displacement compensation device and method for testing foam shear performance, belonging to the fields of material performance measurement and material engineering application.

Background technique

In recent years, the rapid development of aerospace technologies such as manned spaceflight, deep space exploration, and hypersonic vehicles has put forward more and more application requirements for thermal protection systems and insulation materials. Space vehicles face complex and changeable high and low temperature environments during their in-orbit service and space-to-earth round trips. A large number of thermal insulation materials are required for thermal protection on the outside. As a structural and functional integrated material, foam thermal insulation materials not only have With low thermal conductivity and certain mechanical load-bearing properties, it is very suitable as a thermal insulation material for space vehicles, and has broad application prospects in new solar wing substrates. As a key performance index of foam materials, shear mechanical properties need to be accurately measured, which has become a technical difficulty in the performance evaluation of foam materials.

The traditional methods for measuring the shear mechanical properties of foam materials mostly adopt the test methods in GB/T 10007-2008 or ASTM C393-00 standards, mainly using the upper and lower force-applying mechanisms to apply tensile stress to the foam materials fixed in the fixture , using the method of tensile shear to realize the measurement of material shear strength or shear modulus. Since the foam material will produce lateral deformation during the test process, and the positions of the two grippers of the force-applying mechanism are fixed, the displacement cannot be adjusted with the lateral deformation of the foam, resulting in the coexistence of lateral tensile stress and longitudinal shear stress. The stress and strain test of the shear performance state causes certain test errors, and the accuracy of the test results is low. The error increases with the increase of deformation, stress ratio and tensile stress. Therefore, the traditional test method is mainly suitable for rigid rigid foam materials. For the shear performance test of semi-rigid and soft foam materials, due to the lack of lateral displacement compensation, there are large measurement error.

In summary, due to the existence of lateral displacement and transverse tensile stress in the process of tensile shearing, the traditional foam material shear performance test method is not suitable for semi-rigid and soft foam materials with large deformation during the test process.

Contents of the invention

The technical problem solved by the patent of the present invention is: the present invention provides a lateral displacement compensation device and method for testing foam shear performance, which solves the problem of lateral displacement and tensile stress of semi-rigid and soft foam materials due to deformation. The resulting problem of inaccurate shear performance testing can accurately test the shear performance of semi-rigid and flexible foam materials, improving test efficiency and applicability.

The technical solution of the patent of the present invention is:

A lateral displacement compensation device for testing foam shear performance, including a force application mechanism, a metal splint and a displacement compensation mechanism,

The force application mechanism includes an upper pressure head, a lower pressure head and a connecting mechanism,

The metal splint includes an upper splint and a lower splint,

The displacement compensation mechanism includes upper guide rail, lower guide rail and roller;

The upper pressure head is L-shaped structure, one end is connected with the connecting rod of the connecting mechanism through a lock nut, and the other end is connected with the upper splint through a fixing screw;

The connection mechanism includes an upper connection mechanism and a lower connection mechanism. The connection mechanism is composed of a connecting rod, a lock nut and a pin. The connecting joint of the mechanical testing machine is set on one end of the connecting rod and fixed by a pin; Rigidly fixed with the indenter;

The foam material test sample is pasted between the upper splint and the lower splint with adhesive, the extended parts of the metal splint are fixedly connected with the upper indenter through fixing screws, and the lower splint is fixedly connected with the upper guide rail in the displacement compensation mechanism;

The integrated design of the lower pressure head and the lower guide rail, at least two parallel rollers are arranged between the upper guide rail and the lower guide rail;

The lower pressure head is connected with the connecting rod of the lower connecting mechanism through the lock nut, and the lower connecting rod is connected with the mechanical testing machine through the pin; the upper guide rail of the displacement compensation mechanism can move with the deformation of the foam material test sample, and the deformation is compensated laterally.

Further, the sections of the upper guide rail and the lower guide rail are both isosceles triangle structures, and the included angle between the waist of the triangle and the horizontal plate is 45°.

Further, the determination method of the shear modulus of foam material is:

In the formula: G is the shear modulus of the sample; δ is the thickness of the sample; θ is the slope of the straight line in the load-strain diagram; l is the original length of the sample; b is the original width of the sample.

Further, the method of pasting the foam material test sample between the upper splint and the lower splint with an adhesive is as follows: a layer of adhesive is pre-coated on the part of the metal splint where the sample is pasted, so that the foam sample is respectively close to the two splints. Paste the upper and lower edges, place the upper splint and the lower splint relative to each other and stagger a certain distance after gluing; after the paste is completed, add a splint with the same size as the pressure plate on the upper splint, and translate in the opposite direction to the lower splint The same distance to achieve force balance, then add a counterweight on the top of the pressure plate, and pressurize and cure at room temperature for at least 24 hours. After the sample is cured, place the upper and lower splints vertically on the table so that under any pressure.

A lateral displacement compensation method for testing foam shear performance, comprising the steps of:

Step 1. Insert the upper and lower connecting rods into the concave groove of the connecting joint of the mechanical testing machine for connection. One end of the upper connecting rod is fixedly connected with the upper connecting joint, and the other end is fixedly connected with the upper indenter. By rotating the lock nut The upper connecting rod and the upper indenter are rigidly fixed during the test; the lower connecting mechanism makes the lower connecting rod and the lower indenter respectively rigidly fixed through the lock nut;

Step 2: Open the mechanical testing machine, hoist the upper splint with no sample pasted on the testing machine, and clear the additional load brought by the test plate; install the displacement compensation mechanism in place; install the metal splint with the foam test sample on the test machine respectively. Between the upper head and the lower head;

Step 3: Apply compressive shear stress to the foam test sample at a certain loading rate, that is, apply downward pressure to the upper splint and upward pressure to the lower splint. Under the action of lateral tensile stress, the splint drives the displacement compensation mechanism to move horizontally to compensate the lateral displacement;

Step 4, repeatedly load the foam sample three times at a certain loading rate, draw the load-deformation curve, calculate the shear modulus within the range of the linear segment, and then continue loading at a constant rate until the foam sample breaks to obtain the shear strength of the foam material .

Further, the method of pasting the sample on the metal splint is:

A layer of adhesive is pre-coated on the part where the sample is pasted in the metal splint, so that the foam sample is pasted close to the upper and lower edges of the two splints. After completion, add a splint with the same size as the pressure plate on the upper splint, and translate the same distance with the lower splint in the opposite direction to achieve force balance, and then add a counterweight above the pressure plate. Perform pressure curing for at least 24 hours. After the sample is cured, place the upper and lower splints vertically on the table so that they are not subject to any pressure.

Further, the displacement compensation mechanism includes an upper guide rail, a lower guide rail and a roller; the lower splint is fixedly connected with the upper guide rail in the displacement compensation mechanism;

The integrated design of the lower pressure head and the lower guide rail, at least two parallel rollers are arranged between the upper guide rail and the lower guide rail;

The upper guide rail of the displacement compensation mechanism can move with the deformation of the foam material test sample to compensate the deformation laterally.

Further, the sections of the upper guide rail and the lower guide rail are both isosceles triangle structures, and the included angle between the waist of the triangle and the horizontal plate is 45°.

Further, the determination method of the shear modulus of foam material is:

In the formula: G is the shear modulus of the sample; δ is the thickness of the sample; θ is the slope of the straight line in the load-strain diagram; l is the original length of the sample; b is the original width of the sample.

Further, in step 3, compressive shear stress is applied to the foam test sample at a loading rate of 1-3mm/min, in step 4, the foam sample is repeatedly loaded three times at a loading rate of 1-3mm/min, with 3- The loading is continued at a constant rate of 5 mm/min until the foam sample breaks.

Compared with the prior art, the present invention has beneficial effects as follows:

(1) The present invention utilizes the lateral displacement compensation test method of foam material shear performance, has reduced semi-rigid and soft foam material and the shear performance measurement error that lateral deformation and being subjected to lateral tensile stress causes, and the stress process is closer to Based on the pure shear stress state of the foam material, it solves the inaccurate problem of semi-rigid and soft foam materials using the existing rigid foam shear test tooling, and is more accurate in obtaining the shear performance of the material;

(2) The lateral displacement compensation method of the test device of the present invention is simple and easy to operate, and the test repeatability is high. Compared with the traditional rigid foam material shear performance test device, the whole device has greatly reduced the weight of the fixture, reduced the labor intensity of the testers, and greatly improved the test efficiency;

(3) The load-deformation curve obtained by the present invention using the lateral displacement compensation test method of the shear performance of the foam material is closer to the actual deformation process of the foam material in the process of being subjected to pure shear stress, and the test results have more engineering reference significance.

(4) The parallel rollers between the upper and lower guide rails of the displacement compensation mechanism of the present invention can slide freely, and the sliding range can be adjusted according to the thickness of the sample, which improves the versatility and application range of the test device, and effectively compensates for the existing foam material shear. There are deficiencies in all performance testing methods.

Description of drawings

Fig. 1 is the schematic diagram of the lateral displacement compensation test device of the foam shear performance of the present invention;

Fig. 2 is the sticking and curing schematic diagram of the foam shear sample of the present invention;

Fig. 3 is the load-deformation curve that the lateral displacement compensation test method of foam shear performance of the present invention obtains;

Fig. 4 is the load-deformation curve that traditional foam material shear mechanical properties tensile test method obtains;

In the figure: 13 - the linear segment of the lateral displacement compensation test method, and 14 - the linear segment of the traditional foam shear test method.

detailed description

The present invention will be described in detail below in conjunction with the accompanying drawings.

As shown in Figure 1, a lateral displacement compensation device for testing foam shear performance, including a force application mechanism, a metal splint and a displacement compensation mechanism,

The force applying mechanism includes an upper pressing head 1, a lower pressing head 2 and a connecting mechanism 3,

The metal splint comprises an upper splint 6 and a lower splint 7,

The displacement compensation mechanism includes an upper guide rail 8, a lower guide rail 9 and a roller 10;

The upper pressing head 1 has an L-shaped structure, one end is connected to the connecting rod of the connecting mechanism 3 through a lock nut 5, and the other end is connected to the upper splint 6 through a fixing screw 11;

The connecting mechanism 3 includes an upper connecting mechanism and a lower connecting mechanism. The connecting mechanism is composed of a connecting rod, a lock nut and a pin. The nut and the pressure head are rigidly fixed;

The foam material test sample is pasted between the upper splint 6 and the lower splint 7 by adhesive, the extended part of the metal splint is fixedly connected with the upper pressure head 1 through the fixing screws 11, and the lower splint 7 is connected with the upper guide rail 8 in the displacement compensation mechanism. fixed connection;

The lower pressing head 2 and the lower guide rail 9 are integrated, and at least two parallel rollers 10 are arranged between the upper guide rail 8 and the lower guide rail 9;

The lower pressing head 2 is connected with the connecting rod of the lower connecting mechanism 3 through the lock nut 5, and the lower connecting rod is connected with the mechanical testing machine through a pin; the upper guide rail 8 of the displacement compensation mechanism can move with the deformation of the foam material test sample, and the deformation Make lateral compensation.

Connect the lateral displacement compensation test device with the electronic universal mechanical testing machine. The mechanical testing machine applies longitudinal compressive stress to the force-applying mechanism through the connecting joint. The force applying mechanism mainly includes the upper pressure head, the lower pressure head and the connecting mechanism. The upper pressure head is designed as an "L" shape structure, one end is connected to the connecting rod through a lock nut, and the other end is connected to the upper splint through two M5 fixing screws; The pressure head is integrated with the displacement compensation mechanism; the connection mechanism includes an upper connection mechanism and a lower connection mechanism, which are respectively composed of a connecting rod, a lock nut and a pin. The connecting rod connects with the mechanical testing machine and the indenter through two lock nuts. achieve rigid fixation.

The metal splint is used to paste the foam material shear performance test sample, and consists of an upper splint and a lower splint. The extended part of the metal splint is connected with the test device through fixing screws; the upper splint is connected with the upper indenter with two screws; the lower splint is connected with the upper guide rail of the displacement compensation mechanism with two identical screws. The upper and lower splints are loaded with measuring instruments to measure deformation according to the requirements in GJB130.1-86.

The upper guide rail of the displacement compensation mechanism is connected to the lower splint where the foam sample is pasted; the lower guide rail and the lower indenter are designed in an integrated manner, and there are 4 parallel rollers between the upper guide rail and the lower guide rail. The upper guide rail and the lower guide rail are in an isosceles triangle structure, and the included angle between the waist of the triangle and the horizontal plate is 45°. In the integrated design structure of the lower guide rail and the lower pressure head, the lower pressure head is connected with the connecting rod of the lower connection mechanism through a lock nut, which can not only apply pressure but also support the roller to roll freely in the horizontal direction. The mechanical testing machine is connected; the upper guide rail of the displacement compensation mechanism can move with the deformation of the foam material test sample, so as to achieve the purpose of lateral compensation for the deformation.

Taking the lateral displacement compensation test method of the shear performance of polyimide semi-rigid foam material as an example, the implementation of the patent of the present invention will be described in detail below.

(1) First paste the foam shear test sample on the metal splint, and then perform pressure curing. The length of the sample is 150mm, the width is 50mm, the thickness can be determined according to the thickness of the actual application material, and the recommended size is 25mm. The specific pasting process is: pre-coat a layer of adhesive on the metal splint where the sample is pasted. The adhesive should be evenly applied, the thickness should be moderate, and the shear strength should be higher than the shear strength of the foam material itself. The shear failure location shall occur at the foam test sample location and not at the film location. After gluing, place the upper and lower splints relative to each other and stagger a certain distance, as shown in Figure 2, add a splint with the same size as the pressure plate on the upper splint 6, and translate the same as the lower splint 7 in the opposite direction. distance, to achieve force balance, and then add a counterweight 12 above the platen to achieve curing under a fixed pressure.

After the pasting is completed, it is cured under a certain temperature and pressure. The polyimide foam shear sample is loaded with a pressure of 2kPa, and pressurized and cured for 24 hours at a temperature of 23°C and a relative humidity (40-50)%. After the sample is cured, place the upper and lower splints vertically on the table so that they are not subject to any pressure. When pasting, the sample can be pasted with multiple splints and multiple foam test samples at the same time;

(2) Insert the upper and lower connecting rods into the concave grooves of the connecting joints of the mechanical testing machine respectively, and connect them with the connecting joints with pins. The upper connecting rod is tightly connected with the upper connecting joint through the pin and the locking nut 4, and the upper pressing head 1 is rigidly fixed during the test process by rotating the locking nut 5. Tighten the lock nut 4 and the lock nut 5 of the lower connecting mechanism, so that the lower connecting rod and the lower pressure head 2 are rigidly fixed respectively;

(3) Open the mechanical testing machine to test, hoist the upper splint 6 of the unpasted sample on the testing machine, and clear the additional load brought by the test plate; install the displacement compensation mechanism in place; glue the metal splint of the foam test sample They are installed in the middle of the upper pressing head 1 and the lower pressing head 2 respectively. First install the lower splint 7 and then move the mechanical testing machine to install the upper splint 6;

(4) Apply compressive stress to the foam sample at a certain loading rate. The loading rate is recommended to be 1 mm to 2 mm/min. The foam material undergoes shear deformation, and the cross-section changes from a rectangular structure to a parallelogram structure, resulting in longitudinal And lateral deformation, lateral deformation produces a certain lateral tensile stress on the lower splint 7, which drives the upper guide rail 8 and roller 10 of the displacement compensation mechanism to move horizontally, compensating for the lateral displacement of the foam during deformation;

(5) Load the polyimide foam test sample repeatedly three times, draw the load-deformation curve, judge the range of the linear segment and calculate the shear modulus. Then continue loading at a constant rate until fracture to obtain the shear strength of the foam. Calculate the shear modulus of foam material according to formula (1);

In the formula: G is the shear modulus of the sample; δ is the thickness of the sample; θ is the slope of the straight line in the load-strain diagram; l is the original length of the sample; b is the original width of the sample.

(6) After a test, remove the metal splint pasted with foam material, repeat the measurement of the next test piece or close the electronic universal testing machine to end the test.

The shear performance load-deformation curve (Fig. 3) formed by the lateral displacement compensation test method of foam material shear performance is compared with the load-deformation curve (Fig. 4) of the existing foam material tensile shear test method. Using two methods, calculate the shear modulus (second shear modulus, third shear modulus) obtained in the repeated loading stage, the fourth shear modulus obtained in the continuous loading stage, and the continuous loading until The shear strength obtained at fracture is shown in Table 1.

The shear modulus obtained by the lateral displacement compensation test method of the foam material in Fig. 3 is lower than that obtained by the tensile shear test method in Fig. 4, and the shear strength of the former is slightly higher than that of the latter. The slope of the linear segment 13 range of Fig. 3 is smaller than that of the linear segment 14 range of Fig. 4, that is, within the same force value variation range, the longitudinal (i.e. tangential) deformation produced by the lateral displacement compensation test method is larger, and the deformation of the foam material is closer to The true deformation, and therefore the smaller the resulting shear modulus.

Table 1 The shear strength and modulus obtained by different foam material shear test methods

Due to the reduction of the influence of lateral displacement and lateral tensile stress, the modulus measured by the lateral displacement compensation test method for shear performance is smaller and closer to the actual shear modulus. Accurate testing of semi-rigid and soft foam shear properties (including shear modulus and shear strength) has been realized.

The content that is not described in detail in the description of the present invention belongs to the well-known technology of those skilled in the art. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may modify or equivalently replace the technical solution within the scope of the claims, which does not affect the essence of the present invention.

Claims (10)

1. A transverse displacement compensation device for testing the shearing performance of foam is characterized by comprising a force application mechanism, a metal clamping plate and a displacement compensation mechanism,

the force application mechanism comprises an upper pressure head (1), a lower pressure head (2) and a connecting mechanism (3),

the metal splint comprises an upper splint (6) and a lower splint (7),

the displacement compensation mechanism comprises an upper guide rail (8), a lower guide rail (9) and a roller (10);

the upper pressure head (1) is of an L-shaped structure, one end of the upper pressure head is connected with a connecting rod of the connecting mechanism (3) through a locking nut (5), and the other end of the upper pressure head is connected with an upper clamping plate (6) through a fixing screw (11);

the connecting mechanism (3) comprises an upper connecting mechanism and a lower connecting mechanism, the connecting mechanisms are respectively composed of a connecting rod, a locking nut and a pin, and a connecting joint of the mechanical testing machine is sleeved at one end of the connecting rod and fixedly connected with the connecting rod through the pin; the other end of the connecting rod is rigidly fixed with the pressure head through a locking nut;

the foam material test sample is adhered between an upper clamping plate (6) and a lower clamping plate (7) through an adhesive, the extension part of the metal clamping plate is fixedly connected with an upper pressure head (1) through a fixing screw (11), and the lower clamping plate (7) is fixedly connected with an upper guide rail (8) in a displacement compensation mechanism;

the lower pressure head (2) and the lower guide rail (9) are integrally designed, and at least two parallel rolling shafts (10) are arranged between the upper guide rail (8) and the lower guide rail (9);

the lower pressure head (2) is connected with a connecting rod of the lower connecting mechanism (3) through a locking nut, and the lower connecting rod is connected with a mechanical testing machine through a pin; the upper guide rail (8) of the displacement compensation mechanism can move along with the deformation of the foam material test sample to perform transverse compensation on the deformation.

2. The lateral displacement compensation device for testing the shearing performance of the foam as claimed in claim 1, wherein the cross sections of the upper guide rail (8) and the lower guide rail (9) are both isosceles triangle structures, and the included angle between the triangle waist and the horizontal plate is 45 degrees.

3. The lateral displacement compensation device for testing the shear performance of foam according to claim 1, wherein the shear modulus of the foam is determined by:

in the formula: g is the shear modulus of the sample; δ is the thickness of the sample; theta is the slope of a straight line in the load-deformation diagram; l is the original length of the sample; b is the original width of the sample.

4. The lateral displacement compensation device for testing the shear performance of foam according to claim 1, wherein the foam test sample is adhered between the upper clamping plate (6) and the lower clamping plate (7) by the adhesive by the following method: coating a layer of adhesive on the part of the metal splint, which is adhered with the sample, in advance to ensure that the foam sample is respectively adhered close to the upper edge and the lower edge of the two splints, and oppositely placing the upper splint (6) and the lower splint (7) and staggering a certain distance after the adhesive is coated; after the sample is cured, the upper clamping plate and the lower clamping plate are vertically placed on a table top to prevent the sample from being subjected to any pressure.

5. A lateral displacement compensation method for testing the shear performance of foam, which is characterized by using the lateral displacement compensation device of claims 1-4, comprising the following steps:

the method comprises the following steps that firstly, an upper connecting rod and a lower connecting rod are respectively inserted into a connecting joint concave groove of a mechanical testing machine to be connected, one end of the upper connecting rod is fixedly connected with an upper connecting joint, the other end of the upper connecting rod is fixedly connected with an upper pressure head (1), and the upper connecting rod and the upper pressure head are rigidly fixed in the testing process through rotating a locking nut (4) and a locking nut (5); the lower connecting mechanism enables the lower connecting rod and the lower pressure head (2) to respectively achieve rigid fixed connection through a locking nut;

opening a mechanical testing machine, hoisting an upper clamping plate (6) which is not adhered with a sample on the testing machine, and resetting the additional load brought by the testing plate; mounting the displacement compensation mechanism in place; respectively arranging metal clamping plates adhered with foam test samples between an upper pressure head (1) and a lower pressure head (2);

thirdly, applying a pressing shear stress to the foam test sample at a certain loading rate, namely applying a downward pressure to the upper clamping plate (6) and applying an upward pressure to the lower clamping plate (7), wherein the foam material generates longitudinal and transverse deformation under the action of the shear stress, and the lower clamping plate (7) drives the displacement compensation mechanism to horizontally move under the action of the transverse tensile stress to compensate the transverse displacement;

and step four, repeatedly loading the foam sample at a certain loading rate for three times, drawing a load-deformation curve, calculating the shear modulus in a linear section range, and continuously loading at a constant rate until the foam sample is broken to obtain the shear strength of the foam material.

6. The lateral displacement compensation method for testing the shearing performance of the foam as claimed in claim 5, wherein the method for adhering the sample on the metal clamping plate comprises the following steps:

coating a layer of adhesive on the part, which is adhered with the sample, of the metal clamping plate in advance, so that the foam sample is respectively adhered close to the upper edge and the lower edge of the two clamping plates, and after the adhesive is coated, oppositely placing the upper clamping plate (6) and the lower clamping plate (7) and staggering a certain distance; after the pasting is finished, a clamping plate with the same size as the upper clamping plate is added on the upper clamping plate (6) to serve as a pressing plate, the upper clamping plate and the lower clamping plate (7) move horizontally for the same distance in the opposite direction to achieve stress balance, then a balancing weight (12) is added above the pressing plate, pressurization curing is carried out for at least 24 hours under the condition of normal temperature, and after sample curing is finished, the upper clamping plate and the lower clamping plate are vertically placed on a table top to be free of any pressure.

7. The lateral displacement compensation method for testing the shearing performance of the foam is characterized in that the displacement compensation mechanism comprises an upper guide rail (8), a lower guide rail (9) and a roller (10); the lower clamping plate (7) is fixedly connected with an upper guide rail (8) in the displacement compensation mechanism;

the lower pressure head (2) and the lower guide rail (9) are integrally designed, and at least two parallel rolling shafts (10) are arranged between the upper guide rail (8) and the lower guide rail (9);

the upper guide rail (8) of the displacement compensation mechanism can move along with the deformation of the foam material test sample to perform transverse compensation on the deformation.

8. The lateral displacement compensation method for testing the shearing performance of the foam as claimed in claim 7, wherein the sections of the upper guide rail (8) and the lower guide rail (9) are both isosceles triangle structures, and the included angle between the triangle waist and the horizontal plate is 45 °.

9. The method for compensating lateral displacement for testing the shear performance of foam according to claim 5, wherein the shear modulus of the foam material is determined by:

in the formula: g is the shear modulus of the sample; δ is the thickness of the sample; theta is the slope of a straight line in the load-deformation diagram; l is the original length of the sample; b is the original width of the sample.

10. The method of claim 5, wherein the foam test sample is applied with a compressive shear stress at a loading rate of 1-3mm/min in step three, and the foam sample is repeatedly loaded at a loading rate of 1-3mm/min three times and continuously loaded at a constant rate of 3-5mm/min until the foam sample breaks in step four.

Images