Material stress behavior measuring device and measuring method thereof

Abstract

The present invention relates to a material stress behavior measuring device, comprising a base, a fixing assembly and an adjustment assembly; the fixing assembly comprises a collection unit and a fixing part, a fixed end gap for accommodating a sample to be measured is formed between the collection end of the collection unit and the fixing part; the base is provided with at least two adjustment slots, the adjustment assembly comprises a first clamping part and a second clamping part, the first clamping part and the second clamping part are respectively connected to the two adjustment slots through a connecting part, and an adjustment end gap for accommodating a sample to be measured is formed between the first clamping part and the second clamping part. The measuring device can conveniently fix the two ends of the sample to be measured and allow the sample to be measured to maintain the angle required for measurement, while the collection unit can collect stress data in real time. Since the collection unit is solely subjected to the stress of the sample to be measured, the collected stress data is accurate. When measuring, it can be placed in an environmental chamber to change the ambient temperature of the measurement, so that measurement can be conveniently performed and the accuracy of the measurement can be ensured.

Description

Technical Field

[0001] The present invention relates to the field of testing devices, and more particularly to a material stress behavior measuring device and a measuring method thereof. Background Art

[0002] Studying the stress relaxation behavior of materials is of great significance for optimizing product performance, improving durability, selecting suitable materials, optimizing production processes, and ensuring product safety.

[0003] Common equipment for measuring the stress relaxation behavior of materials includes universal testing machines (UTMs), rheometers, dynamic mechanical analyzers (DMAs), and creep testers. Universal testing machines provide precise load and displacement control and are suitable for accurately measuring stress relaxation, but may have limitations in sample size and environmental compatibility. Rheometers are suitable for detailed analysis of stress relaxation, but may not be suitable for large samples or certain nonlinear viscoelastic materials. DMAs can provide valuable information about viscoelastic properties and relaxation behavior, but are expensive and require expertise. Creep testers are suitable for long-term stress relaxation studies, but may have limitations in the applied stress range and sample geometry. These devices are also unable to cope with the study of stress relaxation behavior under complex environmental factors. Adding variables to environmental factors is also a situation that is inevitably encountered in the actual use of materials, which ultimately makes the testing process of material stress relaxation behavior using the above-mentioned equipment complicated and difficult to operate. Summary of the Invention

[0004] In order to overcome the problems of complicated material relaxation behavior testing process and difficult operation in the above-mentioned prior art, the present invention provides a material stress behavior measuring device and a measuring method thereof, which can more conveniently and accurately measure the material stress relaxation behavior.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a material stress behavior measuring device, including a base, a fixing component and an adjustment component both installed on the base; the fixing component includes a collection unit and a fixing piece, and a fixed end gap for accommodating one end of the sample to be measured is formed between the collection end of the collection unit and the fixing piece; the base is provided with at least two adjustment slots, and the adjustment component includes a first clamping piece and a second clamping piece, the first clamping piece is connected to the adjustment slot through a first connecting piece, and the second clamping piece is connected to the other adjustment slot through a second connecting piece, and an adjustment end gap for accommodating the other end of the sample to be measured is formed between the first clamping piece and the second clamping piece.

[0006] In the above technical solution, the two ends of the sample to be tested are respectively located in the fixed end gap and the adjustment end gap, the fixed end of the sample to be tested is located in the fixed end gap, and the other end is the adjustment end of the sample to be tested. The sample to be tested located in the fixed end gap is connected to the base through the collection unit and the fixing member to achieve clamping of the sample to be tested, and the sample to be tested located in the adjustment end gap is clamped by installing the first clamping member and the second clamping member on the base, wherein the first clamping member and the second clamping member can be connected to different positions of the adjustment groove through the first connecting member and the second connecting member respectively to achieve position change, so that the sample to be tested maintains different angles when clamped, thereby achieving testing of different bending angles of the sample to be tested. When the two ends of the sample to be tested are fixed to the base, since the sample to be tested is in a bent state, and the fixing member, the first clamping member and the second clamping member are fixed, the stress of the sample to be tested will be fully reflected on the collection unit and collected by the collection end of the collection unit. When measuring, the operator can quickly fix the sample to be tested according to the required bending angle, and then place the entire base into the environmental chamber or add reagents to the sample to be tested without affecting the base or causing inaccurate test results, thereby achieving rapid and accurate measurement of the material stress relaxation behavior.

[0007] The fixed end gap and the adjustable end gap are not on the same straight line, and the center line of the fixed end gap and the center line of the adjustable end gap form an angle greater than 0 degrees. When the two ends of the sample to be tested are respectively installed in the fixed end gap and the movable end gap, the sample to be tested is bent.

[0008] The collection end of the collection unit is provided with a pressure sensor, which collects the stress data of the sample to be tested in real time by detecting the pressure.

[0009] Preferably, the adjustment slots are provided with at least four and are arc-shaped, namely the first adjustment slot, the second adjustment slot, the third adjustment slot and the fourth adjustment slot; the first connecting members are provided with two, namely the first connecting member A and the first connecting member B, the first connecting member A and the first connecting member B respectively pass through the two sides of the first clamping member and are connected to the first adjustment slot and the second adjustment slot respectively; the second connecting members are provided with two, namely the second connecting member A and the second connecting member B, the second connecting member A and the second connecting member B respectively pass through the two sides of the second clamping member and are connected to the third adjustment slot and the fourth adjustment slot respectively. The first clamping member and the second clamping member are fixed by the first connecting member and the second connecting member on both sides. The fixing angle of the first clamping member can be changed by changing the connection positions of the first connecting member A and the first connecting member B in the first adjustment slot and the second adjustment slot respectively. Similarly, the fixing angle of the second clamping member is changed in the same way. When the adjustment slots are all arc-shaped, after the sample to be tested is bent, the angles of the first clamping member and the second clamping member are adjusted so that the first clamping member and the second clamping member can have a larger contact area with the sample to be tested, thereby reducing the stress of the sample to be tested in other directions and affecting the data collection results.

[0010] Preferably, the fixed end gap is taken as the center of the circle, wherein the center of the circle may be the midpoint of the fixed end gap or any point of the fixed end gap. After confirming the position of the center of the circle, the arc trajectory function of the first adjustment groove is calculated based on the center of the circle:

[0011] Xt: L / t*(1-cos(t))+7.5*sin(t)-5.5*cos(t)

[0012] Yt:L / t*sin(t)+7.5*cos(t)+5.5*sin(t)

[0013] The arc trajectory function of the second adjustment groove is:

[0014] Xt: L / t*(1-cos(t))+7.5*sin(t)-20.5*cos(t)

[0015] Yt:L / t*sin(t)+7.5*cos(t)+20.5*sin(t)

[0016] The arc trajectory function of the third adjustment groove is:

[0017] Xt: L / t*(1-cos(t))+7.5*sin(t)+5.5*cos(t)

[0018] Yt:L / t*sin(t)+7.5*cos(t)-5.5*sin(t)

[0019] The arc trajectory function of the fourth adjustment groove is:

[0020] Xt: L / t*(1-cos(t))+7.5*sin(t)+20.5*cos(t)

[0021] Yt: L / t*sin(t)+7.5*cos(t)-20.5*sin(t);

[0022] Where t is the bending angle of the sample to be tested, ranging from 30 to 120 degrees; L is the length of the sample to be tested, expressed in millimeters. The bending angle is the arc formed by the sample being bent; arc length = the ratio of arc length to radius. The dimensions of the sample to be tested can be, but are not limited to, 80 to 200 mm in length, 2 to 40 mm in width, and 0.8 to 3.5 mm in thickness. These dimensions can be selected based on actual needs. The sample to be tested can be made of polymer, metal, or other materials.

[0023] After the trajectories of the first, second, third, and fourth adjustment slots are set according to the aforementioned function, as long as the bending angle of the sample to be tested is between 30 and 120 degrees, the first clamping member can adjust the positions of the first connection A and the first connection B in the first and second adjustment slots, respectively, so that the clamping surface of the first clamping member is completely aligned with and leveled with the clamped surface on one side of the adjustable end of the sample to be tested. Similarly, the clamping surface of the second clamping member is completely aligned with and leveled with the clamped surface on the other side of the adjustable end of the sample to be tested. Ultimately, the stress applied to the adjusted end of the sample to be tested after being fixed is perpendicular to the clamping surfaces of the first and second clamping members. As for the fixed end of the sample to be tested located at the collection unit, since the surface of the fixed end of the sample to be tested is aligned with the collection end of the collection unit during installation, when the adjustable end of the sample to be tested does not generate stress in other directions, the fixed end of the sample to be tested will not deviate. The generated stress is perpendicular to the collection end of the collection unit, thereby further ensuring the accuracy of the collected data.

[0024] Preferably, the base is provided with a fixing slot for mounting the collection unit and the fixing member, and the collection unit and the fixing member are connected to the fixing slot via a fastener and a third connecting member, respectively. The collection unit and the fixing member are detachably connected to the base via the fastener and the third connecting member, respectively. This arrangement facilitates component replacement and, when the thickness of the sample to be tested varies, the position of the collection unit and the fixing member can be adjusted to accommodate the thickness variation of the sample to be tested.

[0025] Preferably, the first clamping member and the second clamping member are each provided with a first elongated hole for the first connecting member and the second connecting member to pass through; the fixing member is provided with a second elongated hole for the third connecting member to pass through. When the thickness of the sample to be tested changes, the first, second, and third connecting members can be loosened, and the width of the adjustment end gap can be changed by moving the first clamping member and the second clamping member separately through the first elongated holes. This eliminates the need to remove the entire first and second clamping members, making adjustment more convenient. Similarly, the adjustment of the fixing member follows the same principle.

[0026] Preferably, a zero scale line is provided on the base. The first, second, third, and fourth adjustment slots are all provided with angle scale lines. When one end of the sample to be tested is fixed to the fixed end gap (this end of the sample is the fixed end), the fixed end of the sample to be tested is aligned with the zero scale line, and then the movable end of the sample to be tested is aligned with the corresponding angle scale line. This allows the sample to be accurately and quickly confirmed each time it changes to a different bending angle, thereby speeding up the fixing speed of the sample to be tested and increasing measurement accuracy.

[0027] Preferably, the base is provided with angle scale lines, the center points of which are located on the zero scale line. When using the tooling to evaluate the rebound behavior of the test sample, after the test sample is thermoformed, the bending conditions of the test sample before and after thermoforming can be measured and compared using the angle scale lines to intuitively detect the angular change of the test sample and thus evaluate the rebound behavior of the test sample.

[0028] During the plastic molding process, parts are fixed to a specific shape and then heat-treated to achieve final shape. However, due to varying thermoforming efficiencies among different materials, the degree of post-molding springback varies. This material's springback behavior adds uncertainty to part structural design, material selection, and the development of the molding process. Springback behavior is a comprehensive result of factors such as the material's stress relaxation rate, its modulus at different temperatures, and residual internal stress. Therefore, traditional instruments struggle to quantify this behavior. This device, however, provides rapid measurement and evaluation of material springback during thermoforming.

[0029] The present invention also provides a material stress behavior measurement method, using the above-mentioned material stress behavior measurement device, comprising the following steps:

[0030] S1: Place the measuring device and the sample to be measured into the environmental chamber, adjust the temperature and humidity of the environmental chamber to the target temperature and target humidity, and connect the acquisition unit to the data analysis and storage unit;

[0031] S2: placing one end of the sample to be tested in the fixed end gap so that the surface of the one end of the sample to be tested is in contact with the collecting end of the collecting unit, and fixing the one end of the sample to be tested by the fixing member and the collecting unit; the collecting end starts to collect stress data, and after the sample to be tested is bent to a desired angle, the other end of the sample to be tested is placed in the adjustable end gap, and the other end of the sample to be tested is fixed by the adjustable end gap formed by the first clamping member and the second clamping member;

[0032] S3: Adjust or maintain the temperature and humidity of the environmental chamber, and record the stress changes over time through the data analysis storage unit.

[0033] In the above method, after the measuring device and the sample to be tested are placed in the environmental chamber, the environmental chamber is first adjusted to the target environment, and then the acquisition unit and the data analysis and storage unit are connected and the sample to be tested is installed on the measuring device. Among them, it is necessary to start data measurement after the fixed end of the sample to be tested is fixed. This operation can more accurately record the initial load of the sample to be tested in the target environment. At the same time, after the fixed end of the sample to be tested is fixed to the measuring device, data collection is started, which is also to enable data collection after the sample to be tested is clamped, so as not to miss any data on the stress changes of the sample to be tested.

[0034] Preferably, in step S1, the temperature of the environmental chamber is adjusted to a target temperature when both the sample to be tested and the temperature of the environmental chamber reach the target temperature. When both the sample to be tested and the temperature of the environmental chamber reach the target temperature, relaxation of the sample to be tested is better ensured to occur at the target temperature, and the relaxation process of the sample to be tested at a specific temperature is more accurately recorded.

[0035] Preferably, in described step S3, the peak value that stress data occurs is observed in the process of recording stress change over time.Peak value is the force value feedback of material generation bending strain, and is relevant to strain amount, material modulus. When strain amount (bending angle is constant), peak value size is determined by material modulus height. It can be used for the calculation of relaxation rate, by observing the rate that peak value can calculate force value relaxation.

[0036] The above method also includes the rebound behavior measurement, and the specific process is as follows:

[0037] S4: After completing step S3, read the current bending angle of the sample to be tested through the angle scale and record it as the angle before the test, adjust the temperature to the temperature required for thermoforming of the sample to be tested, and cool it to room temperature after constant temperature treatment for a preset time; the thermoforming temperature can generally be selected as a certain degree above the glass transition temperature. The temperature above the glass transition temperature is the temperature point at which the molecular segments have the ability to move. The higher the temperature, the stronger the segment movement ability, the shorter the thermoforming time, and the smaller the residual stress. For example, the thermoforming temperature of PA66 can be selected as 150℃; the thermoforming temperature of PA612 can be selected as 130℃; for example, the thermoforming temperature of PBT can be selected as 120℃.

[0038] S5: Remove the first clamp and the second clamp, let it stand for a preset time, read the current bending angle of the sample to be tested through the angle scale and record it as the post-test angle. The difference between the post-test angle and the pre-test angle is the rebound value of the sample to be tested.

[0039] Compared with existing technologies, the present invention has the following advantages: the measuring device can conveniently fix both ends of the sample to be measured and maintain the sample at the required measurement angle. At the same time, the acquisition unit can collect stress data in real time. Because the acquisition unit is solely subjected to the stress of the sample to be measured, the collected stress data is accurate. During measurement, the sample can be placed in an environmental chamber to change the measurement environment temperature, without being affected by many existing measurement devices such as clamping restrictions and environmental limitations. This allows for convenient and accurate measurement of the stress relaxation behavior of different materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the structure of a material stress behavior measuring device of the present invention;

[0041] Figure 2 It is a structural schematic diagram of the base of the present invention;

[0042] Figure 3 is a schematic structural diagram of the first clamping member of the present invention;

[0043] Figure 4 It is a structural schematic diagram of the fixing member of the present invention;

[0044] Figure 5 This is a schematic structural diagram of Example 3 of a material stress behavior measuring device of the present invention;

[0045] Figure 6 A comparison chart of data measured by the measurement method of the present invention and data measured using a DMA device;

[0046] Figure 7 The figure is a comparison diagram of the fitting curve of the data measured by the measurement method of the present invention and the fitting curve of the data measured by the DMA device. DETAILED DESCRIPTION

[0047] The drawings are for illustrative purposes only and should not be construed as limiting this patent. To better illustrate the embodiments, some components in the drawings may be omitted, enlarged, or reduced in size, and do not represent actual product dimensions. Those skilled in the art will understand that some well-known structures and their descriptions may be omitted from the drawings. The positional relationships depicted in the drawings are for illustrative purposes only and should not be construed as limiting this patent.

[0048] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "long", "short", etc. indicating the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0049] The technical solution of the present invention is further described in detail below through specific embodiments and in conjunction with the accompanying drawings:

[0050] Example 1

[0051] like Figure 1 The present invention shows an embodiment 1 of a material stress behavior measurement device, comprising a base 1, a fixing assembly and an adjustment assembly, both mounted on the base 1. The fixing assembly includes a collection unit 2 and a fixing member 3, with a fixed end gap formed between the collection end of the collection unit 2 and the fixing member 3 for accommodating one end of the sample to be measured. The base 1 is provided with at least two adjustment slots, and the adjustment assembly includes a first clamping member 4 and a second clamping member 5. The first clamping member 4 is connected to the adjustment slot via a first connecting member, and the second clamping member 5 is connected to the other adjustment slot via a second connecting member, forming an adjustment end gap between the first clamping member 4 and the second clamping member 5 for accommodating the other end of the sample to be measured. In this embodiment, the collection unit 2 and the fixing member 3 are detachably connected to the base 1, and the connection method may be a snap or fastener. The first connecting member and the second connecting member are fasteners.

[0052] Specifically, there are at least four arc-shaped adjustment slots, namely the first adjustment slot 6, the second adjustment slot 7, the third adjustment slot 8, and the fourth adjustment slot 9. There are two first connecting members, namely the first connecting member A10 and the first connecting member B11. The first connecting member A10 and the first connecting member B11 pass through the two sides of the first clamping member 4 and are connected to the first adjustment slot 6 and the second adjustment slot 7 respectively. There are two second connecting members, namely the second connecting member A12 and the second connecting member B13. The second connecting member A12 and the second connecting member B13 pass through the two sides of the second clamping member 5 and are connected to the third adjustment slot 8 and the fourth adjustment slot 9 respectively. The first clamping member 4 and the second clamping member 5 are fixed by the first connecting member and the second connecting member on both sides. By changing the connection position of the first connecting member A10 and the first connecting member B11 in the first adjustment slot 6 and the second adjustment slot 7 respectively, the fixing angle of the first clamping member 4 can be changed. Similarly, the fixing angle of the second clamping member 5 can be changed in the same way. When the adjustment grooves are all arc-shaped and the sample to be tested is bent, the angles of the first clamping member 4 and the second clamping member 5 are adjusted so that the first clamping member 4 and the second clamping member 5 can have a larger contact area with the sample to be tested, thereby reducing the stress of the sample to be tested in other directions and affecting the data collection results.

[0053] In this embodiment, the base 1 is provided with a zero scale line at the fixed end gap. The zero scale line is located at the center of the fixed end gap. The center of the circle is located on the zero scale line. Based on the center of the circle, the arc trajectory function of the first adjustment groove 6 is:

[0054] Xt:L / t*(1-cos(t))+7.5*sin(t)-5.5*cos(t)

[0055] Yt:L / t*sin(t)+7.5*cos(t)+5.5*sin(t)

[0056] The arc trajectory function of the second adjustment slot 7 is:

[0057] Xt: L / t*(1-cos(t))+7.5*sin(t)-20.5*cos(t)

[0058] Yt:L / t*sin(t)+7.5*cos(t)+20.5*sin(t)

[0059] The arc trajectory function of the third adjustment groove 8 is:

[0060] Xt: L / t*(1-cos(t))+7.5*sin(t)+5.5*cos(t)

[0061] Yt:L / t*sin(t)+7.5*cos(t)-5.5*sin(t)

[0062] The arc trajectory function of the fourth adjustment slot 9 is:

[0063] Xt: L / t*(1-cos(t))+7.5*sin(t)+20.5*cos(t)

[0064] Yt: L / t*sin(t)+7.5*cos(t)-20.5*sin(t);

[0065] Where t is the bending angle of the sample to be tested, ranging from 30 to 120 degrees; L is the length of the sample to be tested, in millimeters. After the trajectories of the first adjustment slot 6, the second adjustment slot 7, the third adjustment slot 8, and the fourth adjustment slot 9 are set according to the above function, as long as the bending angle of the sample to be tested is between 30 and 120 degrees, the first clamping member 4 can adjust the positions of the first connection A and the first connection member B11 in the first adjustment slot 6 and the second adjustment slot 7, respectively, so that the clamping surface of the first clamping member 4 and the corresponding clamped surface at the other end of the sample to be tested are completely aligned and remain horizontal. Similarly, the clamping surface of the second clamping member 5 is also completely aligned and remains horizontal with the corresponding clamped surface at the other end of the sample to be tested. Ultimately, the stress on the sample to be tested after being fixed is perpendicular to the clamping surfaces of the first clamping member 4 and the second clamping member 5. As for the sample to be tested located at the collection unit 2, since the surface of the fixed end of the sample to be tested is in contact with the collection end of the collection unit 2 during installation, when the adjustment end of the sample to be tested does not generate stress in other directions, the fixed end of the sample to be tested will not be offset. The generated stress is perpendicular to the collection end of the collection unit 2, thereby further ensuring the accuracy of the collected data.

[0066] Furthermore, the first adjustment slot 6, the second adjustment slot 7, the third adjustment slot 8, and the fourth adjustment slot 9 are all provided with angle scale lines. When the sample to be tested is fixed to the base 1, the fixed end of the sample to be tested is aligned with the zero scale line, and then the movable end of the sample to be tested is aligned with the corresponding angle scale line. This allows the sample to be accurately and quickly confirmed each time it changes to a different bending angle, which can speed up the fixing speed of the sample to be tested and increase the accuracy of the measurement.

[0067] The working principle or working process of this embodiment is as follows: the fixed end of the sample 18 to be tested is inserted into the fixed end gap and aligned with the zero scale line, and then the fixing member 3 is fixedly connected to the base 1, so that the two side surfaces of the fixed end of the sample 18 to be tested are respectively in contact with the collection end of the collection unit 2 and the fixing member 3. External force is applied to the sample 18 to bend it and align the adjustment end of the sample 18 to the required angle scale line. In this embodiment, as shown in FIG. Figure 1As shown, bend the sample 18 to be tested 90 degrees. Then, adjust the first connector A10 and the first connector B11 to the first adjustment slot 6 and the second adjustment slot 7, respectively, so that the clamping surface of the first clamping member 4 abuts one side of the adjustable end of the sample 18 to ensure that the clamping surface of the first clamping member 4 is completely aligned with and level with the side of the adjustable end of the sample 18. Then, adjust the second connector A12 and the second connector B13 to the third adjustment slot 8 and the fourth adjustment slot 9, respectively, so that the clamping surface of the second clamping member 5 abuts the other side of the adjustable end of the sample 18 to ensure that the clamping surface of the second clamping member 5 is completely aligned with and level with the other side of the adjustable end of the sample 18. After the first clamping member 4 and the second clamping member 5 are fixed to the base 1, the adjustable end of the sample 18 to be tested is also clamped within the gap between the adjustable ends. During the measurement process, the bending angle of the sample 18 to be tested can be changed by adjusting the positions of the first clamping member 4 and the second clamping member 5, thereby enabling testing of different bending angles of the sample 18 to be tested. After the test sample 18 is fixed to the base 1, since the test sample 18 is in a bent state and the fixing member 3, the first clamping member 4, and the second clamping member 5 are fixed, the stress of the test sample 18 is fully reflected on the collection end of the collection unit 2 and collected by the collection unit 2. During measurement, the operator can quickly fix the test sample 18 according to the required bending angle, and then place the entire base 1 in an environmental chamber or add reagents to the test sample without affecting the base 1 or causing inaccurate test results, thereby achieving rapid and accurate measurement of the material stress relaxation behavior.

[0068] The beneficial effects of this embodiment include: the measuring device can conveniently secure both ends of the sample to be measured and maintain the sample at the required angle for measurement; simultaneously, the acquisition unit 2 can collect stress data in real time. Because the acquisition unit 2 is solely subjected to the stress of the sample to be measured, the collected stress data is accurate. During measurement, the sample can be placed in an environmental chamber to change the ambient temperature of the measurement, without being affected by many existing measurement devices, such as clamping limitations and environmental restrictions. This allows for convenient and accurate measurement of stress relaxation behavior of different materials.

[0069] Example 2

[0070] like Figure 2Example 2 of a material stress behavior measurement device is shown. Based on Example 1, it differs from Example 1 in that a fixing slot 14 is provided on the base 1 for mounting a collection unit 2 and a fixing member 3. The collection unit 2 and the fixing member 3 are connected to the fixing slot 14 via a fastener and a third connecting member 17, respectively. Both the collection unit 2 and the fixing member 3 are detachably connected to the base 1 via the third connecting member 17. This arrangement facilitates component replacement and, when the thickness of the sample to be measured varies, the position of the collection unit 2 and the fixing member 3 can be adjusted to accommodate the thickness variation.

[0071] Furthermore, the first clamping member 4 and the second clamping member 5 are respectively provided with a first elongated hole 15 for the first connecting member and the second connecting member to pass through; the fixing member 3 is provided with a second elongated hole 16 for the third connecting member 17 to pass through. The first connecting member, the second connecting member and the third connecting member 17 are all fasteners. In this embodiment, the structures of the first clamping member, the second clamping member and the fixing member are consistent. When the thickness of the sample to be tested changes, the first connection, the second connecting member and the third connecting member 17 can be loosened, and the width of the adjustment end gap can be increased by moving the first clamping member 4 and the second clamping member 5 respectively through the action of the first elongated hole 15. There is no need to remove the entire first clamping member 4 and the second clamping member 5, and the adjustment is more convenient. Similarly, the adjustment of the fixing member 3 also follows the above-mentioned principle.

[0072] The remaining features and principles of this embodiment are consistent with those of embodiment 1.

[0073] Example 3

[0074] like Figure 5 Example 3 of a material stress behavior measurement device is shown. Based on Example 2, it differs from Example 2 in that base 1 is provided with angle scale lines 19, the center of which is located on the zero scale line. When using the fixture to evaluate the rebound behavior of a test sample, the angle scale lines can be used to visually detect the angular changes of the test sample after thermoforming, thereby evaluating the sample's rebound behavior.

[0075] Example 4

[0076] An embodiment of a method for measuring material stress behavior, using the material stress behavior measuring device of embodiment 1 or embodiment 2, comprises the following steps:

[0077] S1: placing the measuring device and the sample to be measured into an environmental chamber, adjusting the temperature and humidity of the environmental chamber to the target temperature and target humidity, wherein the standard for adjusting the temperature of the environmental chamber to meet the standard is that the temperature of the sample to be measured and the measurement temperature in the environmental chamber both reach the target temperature, and connecting the acquisition unit to the data analysis and storage unit;

[0078] S2: placing one end of the sample to be tested in the fixed end gap so that the surface of the one end of the sample to be tested is in contact with the collecting end of the collecting unit, and fixing the one end of the sample to be tested by the fixing member and the collecting unit; the collecting end starts to collect stress data, and after the sample to be tested is bent to a desired angle, the other end of the sample to be tested is placed in the adjustable end gap, and the other end of the sample to be tested is fixed by the adjustable end gap formed by the first clamping member and the second clamping member;

[0079] S3: Maintain the temperature and humidity of the environmental chamber, record the stress changes over time through the data analysis storage unit and observe the peak value of the data.

[0080] The working principle of this embodiment is as follows: after the measuring device and the sample to be tested are placed in the environmental chamber, the environmental chamber is first adjusted to the target environment. The target environment refers to the temperature of the sample to be tested reaching the target temperature, and the temperature and humidity of the measuring environment in the environmental chamber both reach the target temperature and target humidity. Then the acquisition unit and the data analysis and storage unit are connected and the sample to be tested is mounted on the measuring device. Among them, it is necessary to start data measurement after the fixed end of the sample to be tested is fixed. This operation can more accurately record the initial load of the sample to be tested in the target environment. At the same time, after the fixed end of the sample to be tested is fixed on the measuring device, data collection is started. This is also to enable data collection to be performed after the sample to be tested is clamped, so as not to miss any data on the stress changes of the sample to be tested at a specific temperature.

[0081] In this embodiment, the sample to be tested is a sample obtained by injection molding of PA66 (relative viscosity 2.6), the sample length is 120 mm, the thickness is 1.6 mm, the width is 12.5 mm, the test target temperature is 85°C, the target humidity is 50%, and the sample bending angle is 90°.

[0082] This example sets up a comparative example for comparison with the present example. The stress relaxation properties of the same sample under test were measured using a dynamic mechanical testing (DMT) instrument (Discovery DMA850). The sample was clamped between two parallel plates and subjected to a constant deformation at a given temperature of 85°C. Deformation was performed using strain-controlled mode, with the sample stretched to a predetermined strain of 10% and held at this strain for 3 hours. The stress response of the sample was recorded over time.

[0083] The data obtained by the above two measurement methods are plotted and we can get Figure 6 .from Figure 6It can be seen that the stress equilibrium point in the data obtained by the measurement method of this embodiment appears later than the stress equilibrium point obtained by the DMA measurement method, and the resulting curve is smoother. The stress data obtained by the DMA measurement method becomes a straight line after the turning point. However, the stress of the measured sample gradually changes over time, and it is not logical for the stress data to suddenly remain unchanged and reach stress equilibrium. Therefore, by comparison, the measurement method of this embodiment is more consistent with natural laws, thus showing that the measurement method of this embodiment is more accurate in measuring stress relaxation behavior.

[0084] The results of the method of this embodiment are compared with those of the comparative example. Figure 7 As shown, the EXP_tool curve is a stress relaxation curve obtained by actually measuring the sample to be tested using the method of this embodiment, and the SIM-tool curve is a curve obtained by obtaining material parameters through data measured by the tool and fitting through CAE; the EXP_DMA curve is a stress relaxation curve obtained by actually measuring the sample to be tested using the comparative example method, and the SIM_DMA curve is a curve obtained by obtaining material parameters through data actually measured by the DMA device and fitting through CAE.

[0085] Using the measured material parameters and computer-aided engineering (CAE), the stress relaxation data is reversed to obtain the predicted stress relaxation data, thereby reproducing the actual data. The higher the reproducibility between the predicted stress relaxation data and the actual data, that is, the more similar the results of the forward measurement and the reverse deduction are, the more accurate the actual data is. Figure 7 , the EXP_tooling curve is basically consistent with the SIM-tooling curve, while the EXP_DMA curve deviates significantly from the SIM_DMA curve, indicating that the measurement method of this embodiment is more accurate.

[0086] The remaining features and principles of this embodiment are consistent with those of embodiment 1.

[0087] Example 5

[0088] An embodiment of a material stress behavior measurement method, using the material stress behavior measurement device of embodiment 3, includes the following steps:

[0089] S1: placing the measuring device and the sample to be measured into an environmental chamber, adjusting the temperature and humidity of the environmental chamber to the target temperature and target humidity, wherein the standard for adjusting the temperature of the environmental chamber to meet the standard is that the temperature of the sample to be measured and the measurement temperature in the environmental chamber both reach the target temperature, and connecting the acquisition unit to the data analysis and storage unit;

[0090] S2: Place one end of the sample to be tested in the gap at the fixed end and clamp it with the fixing member and the acquisition unit; start data acquisition, bend the sample to be tested to the desired angle, place the other end in the gap at the adjustment end, and clamp the sample to be tested with the first clamping member and the second clamping member;

[0091] S3: Maintaining temperature and humidity, recording stress changes over time through the data analysis storage unit and observing the peak value of the data;

[0092] S4: After completing step S3, the current bending angle of the sample to be tested is read through the angle scale and recorded as the angle before the test. The temperature is adjusted to the temperature required for thermoforming of the sample to be tested. After constant temperature treatment for a preset time, it is cooled to room temperature.

[0093] S5: Remove the first clamp and the second clamp, let it stand for a preset time, read the current bending angle of the sample to be tested through the angle scale and record it as the post-test angle. The difference between the post-test angle and the pre-test angle is the rebound value of the sample to be tested.

[0094] In this embodiment, the stress relaxation behavior and rebound behavior of the sample to be measured are measured by the measuring device of embodiment 3, so that the rebound behavior can be quantitatively evaluated.

[0095] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A material stress behavior measuring device, characterized in that: The invention comprises a base (1), a fixing assembly and an adjusting assembly both mounted on the base (1); the fixing assembly comprises a collecting unit (2) and a fixing member (3); a fixing end gap for accommodating one end of a sample to be tested is formed between the collecting end of the collecting unit (2) and the fixing member (3); the base (1) is provided with at least two adjusting slots; the adjusting assembly comprises a first clamping member (4) and a second clamping member (5); the first clamping member (4) is connected to the adjusting slot via a first connecting member, the second clamping member (5) is connected to the other adjusting slot via a second connecting member, and an adjusting end gap for accommodating the other end of the sample to be tested is formed between the first clamping member (4) and the second clamping member (5); The adjustment grooves are provided with at least four and are in an arc shape, namely, a first adjustment groove (6), a second adjustment groove (7), a third adjustment groove (8) and a fourth adjustment groove (9); the first connecting members are provided with two, namely, a first connecting member A (10) and a first connecting member B (11), the first connecting member A (10) and the first connecting member B (11) respectively pass through both sides of the first clamping member (4) and are respectively connected to the first adjustment groove (6) and the second adjustment groove (7); the second connecting members are provided with two, namely, a second connecting member A (12) and a second connecting member B (13), the second connecting member A (12) and the second connecting member B respectively pass through both sides of the second clamping member (5) and are respectively connected to the third adjustment groove (8) and the fourth adjustment groove (9).

2. A material stress behavior measuring device according to claim 1, characterized in that: With the fixed end gap as the center of the circle, the arc trajectory function of the first adjustment groove (6) is: Xt:L / t*(1-cos(t))+7.5*sin(t)-5.5*cos(t) Yt:L / t*sin(t)+7.5*cos(t)+5.5*sin(t) The arc trajectory function of the second adjustment groove (7) is: Xt: L / t*(1-cos(t))+7.5*sin(t)-20.5*cos(t) Yt:L / t*sin(t)+7.5*cos(t)+20.5*sin(t) The arc trajectory function of the third adjustment groove (8) is: Xt: L / t*(1-cos(t))+7.5*sin(t)+5.5*cos(t) Yt:L / t*sin(t)+7.5*cos(t)-5.5*sin(t) The arc trajectory function of the fourth adjustment groove (9) is: Xt: L / t*(1-cos(t))+7.5*sin(t)+20.5*cos(t) Yt: L / t*sin(t)+7.5*cos(t)-20.5*sin(t); Where t is the bending angle of the sample to be tested, ranging from 30 degrees to 120 degrees; L is the length of the sample to be tested.

3. A material stress behavior measuring device according to claim 2, characterized in that: The base (1) is provided with a fixing groove (14) for installing the collection unit (2) and the fixing member (3); the collection unit (2) and the fixing member (3) are connected to the fixing groove (14) via a fastener and a third connecting member (17), respectively.

4. A material stress behavior measuring device according to claim 3, characterized in that: The first clamping member (4) and the second clamping member (5) are each provided with a first elongated hole (15) for the first connecting member and the second connecting member to pass through; the fixing member (3) is provided with a second elongated hole (16) for the third connecting member (17) to pass through.

5. A material stress behavior measuring device according to any one of claims 2 to 4, characterized in that: A zero scale line is provided on the base (1).

6. The material stress behavior measuring device according to claim 5, characterized in that: The first adjustment slot (6), the second adjustment slot (7), the third adjustment slot (8) and the fourth adjustment slot (9) are all provided with angle scale lines.

7. The material stress behavior measuring device according to claim 5, characterized in that: An angle scale line (19) is provided on the base (1), and the center point of the angle scale line (19) is located on the zero scale line.

8. A method for measuring material stress behavior, characterized in that: Using the material stress behavior measuring device according to claim 7 includes the following steps: S1: Place the measuring device and the sample to be measured into the environmental chamber, adjust the temperature and humidity of the environmental chamber to the target temperature and target humidity, and connect the acquisition unit to the data analysis and storage unit; S2: placing one end of the sample to be tested in the fixed end gap so that the surface of the one end of the sample to be tested is in contact with the collection end of the collection unit, and fixing the one end of the sample to be tested by the fixing member and the collection unit; the collection end starts to collect stress data, and after bending the sample to be tested to a desired angle, the other end of the sample to be tested is placed in the adjustment end gap, and the other end of the sample to be tested is fixed by the adjustment end gap formed by the first clamping member and the second clamping member; S3: Adjust or maintain the temperature and humidity of the environmental chamber, and record the stress changes over time through the data analysis storage unit.

9. A material stress behavior measurement method according to claim 8, characterized in that: It also includes the rebound behavior measurement, the specific process is as follows: S4: After completing step S3, the current bending angle of the sample to be tested is read through the angle scale and recorded as the angle before the test. The temperature is adjusted to the temperature required for thermoforming of the sample to be tested. After constant temperature treatment for a preset time, it is cooled to room temperature. S5: Remove the first clamp and the second clamp, let it stand for a preset time, read the current bending angle of the sample to be tested through the angle scale and record it as the post-test angle. The difference between the post-test angle and the pre-test angle is the rebound value of the sample to be tested.

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