An auxiliary device for precisely adjusting the clamping stress of a four-curved surface test sample

Abstract

This utility model relates to an auxiliary device for precisely adjusting the clamping stress of a four-curved surface specimen. It includes a base, a clamp assembly, a universal level, and a dial indicator. The universal level is positioned centrally on the upper surface of a rigid substrate. The specimen is mounted between elastic arc-shaped rubber blocks. The base includes a centering and limiting component for limiting the center position of the specimen and a support for mounting the dial indicator. The dial indicator's probe is vertically downward, directly facing the center of the upper surface of the universal level. A countersunk hole is provided on the top of the base corresponding to the position of the fastening bolt. This application utilizes the centering and limiting component on the base to symmetrically clamp the fatigue specimen. The countersunk hole ensures the clamp assembly remains attached to the base during thickness adjustment. The dial indicator enables continuous and accurate measurement of the clamp thickness. The universal level ensures uniform clamping thickness on all sides. In summary, this design improves the installation efficiency and clamping stress adjustment accuracy of the four-curved surface specimen on the anti-instability clamp.

Description

Technical Field

[0001] This invention belongs to the field of composite material fatigue testing technology, and in particular relates to an auxiliary device for accurately adjusting the clamping stress of a four-curved surface specimen. Background Technology

[0002] Polymer-based fiber-reinforced composites are widely used in aerospace, new energy, and automotive manufacturing due to their superior properties such as high specific strength and high specific modulus. Fatigue testing is an important evaluation method for assessing the durability of materials under long-term cyclic loading. When fiber-reinforced composites undergo compressive (tension-compression, compression-compression) fatigue testing, if the specimen exhibits lateral bending instability after compression, leading to premature failure and abnormal failure modes, the test needs to be repeated to ensure the accuracy and reliability of the fatigue performance assessment.

[0003] In the compressive fatigue testing of fiber-reinforced plastics, the quadrilateral specimen is the main sample type. The shape design of the quadrilateral specimen allows the stress to be concentrated mainly in the curved surface processing area of ​​the specimen, minimizing ineffective damage and improving the reliability and accuracy of the test. However, its clamping distance is significantly longer than that of the strip specimen, making it more prone to compressive instability. Therefore, in order to reduce the probability of compressive instability during the testing of quadrilateral specimens, a special anti-instability fixture needs to be configured for the fatigue test of this specification of specimen. This reduces ineffective instability control and test abnormalities caused by inaccurate or uneven clamping stress control, thereby improving the reliability and consistency of the fatigue test.

[0004] The national standard GB / T 35465.4 proposes an anti-instability fixture for fatigue specimens with four curved surfaces. This fixture primarily uses a set of symmetrical components (including a rigid base plate and an elastic curved rubber block) to clamp the specimen and fit it against its curved working section. Tightening bolts applies pressure, causing the rubber block to deform and apply a specified stress to the curved surface of the specimen. GB / T 35465.4 specifies a specimen clamping stress requirement of 0.8-1.0 MPa, but does not provide specific methods for controlling and adjusting the clamping stress of the anti-instability fixture.

[0005] In light of the aforementioned background conditions, the inventors discovered that, according to the national standard requirement of 0.8-1.0 MPa for sample clamping stress, in practice, taking a medium-hardness (modulus 40-50 MPa) rubber block as an example, the required controlled range of rubber block deformation is 0.3-0.4 mm. The compression state of the rubber block in the clamp is controlled by bolts at the four corners of the clamp, requiring high precision in controlling the deformation of the rubber block. However, in existing technologies, the total thickness of the sample under clamping conditions is manually measured by calipers. The elastic rubber block in the clamp is prone to deformation, and the pressure exerted on each side of the clamp by the caliper jaws during measurement is difficult to maintain consistently, affecting the accuracy of thickness measurement and adjustment. If the degree of compression of the rubber block at each corner of the clamp deviates significantly, the uneven pressure on the rubber block leads to uneven distribution of sample clamping stress, which can easily cause abnormal fatigue test results of the clamped resin fiber composite material sample (i.e., unacceptable failure modes requiring retesting or inconsistent results with low data reliability). In addition, adjusting the thickness of the clamp in the clamping state requires multiple fine adjustments, and each measurement requires picking up the clamp, repeatedly picking up and putting down the clamp and measuring, which is cumbersome and time-consuming. Utility Model Content

[0006] The technical problem to be solved by this utility model is to provide an auxiliary device for accurately adjusting the clamping stress of a four-curved surface specimen. It can quickly complete the installation and clamping stress adjustment of the four-curved surface specimen on the anti-instability fixture, improve the accuracy of the clamping stress magnitude and the consistency of stress distribution of the four-curved surface specimen, thereby reducing the probability of compressive instability of the four-curved surface specimen in actual operation and improving the installation efficiency and testing accuracy of compressive fatigue testing of resin fiber composite materials.

[0007] The technical solution adopted by this utility model to solve its technical problem is as follows: An auxiliary device for precisely adjusting the clamping stress of a four-curved surface sample is provided, including a base, a clamp assembly, a universal level, and a dial indicator; the clamp assembly includes two rigid base plates, two elastic arc-shaped rubber blocks arranged opposite each other between the two rigid base plates, and fastening bolts connecting the two rigid base plates; the two rigid base plates are arranged in parallel, with the lower rigid base plate mounted on the base, and the universal level positioned at the center of the upper surface of the upper rigid base plate; the sample is mounted between the elastic arc-shaped rubber blocks, with the arc-shaped top surface of each elastic arc-shaped rubber block in contact with the arc-shaped working section of the sample; the base includes a centering and limiting component for limiting the center position of the sample and a support for mounting the dial indicator, with the dial indicator's probe vertically downwards and directly facing the center of the upper surface of the universal level; a countersunk hole is provided on the top of the base corresponding to the position of the fastening bolt, the diameter of the countersunk hole being larger than the outer diameter of the fastening bolt.

[0008] Through the above technical solution, the design of the base, universal level, dial indicator, and fixture assembly improves the accuracy and efficiency of symmetrically clamping fatigue specimens by utilizing the centering and limiting components on the base. Countersunk holes are made on the base to mount the dial indicator, allowing the fixture assembly to remain firmly attached to the base during thickness adjustment. Continuous measurement of the fixture assembly thickness by the dial indicator improves the accuracy of thickness measurement and the efficiency of thickness adjustment (specimen clamping stress adjustment). The universal level ensures uniform thickness on all sides of the fixture, guaranteeing consistent clamping stress distribution, reducing the probability of compressive instability during specimen loading on the fatigue testing machine, and improving the reliability of test results. This device enhances the installation efficiency and testing accuracy of compressive fatigue testing of four-curved surface specimens of resin fiber composite materials.

[0009] Preferably, the centering limiting component includes two first blocks that limit the two ends of the sample along its length and two second blocks that limit the rigid substrate, with the second blocks located on both sides of the sample along its length.

[0010] The above technical solution can be used to center and limit the rigid part of the fixture on the base and the sample itself as a whole.

[0011] Preferably, the first stop has symmetrically opposite limiting grooves along the vertical direction, and the width of the limiting grooves matches the width of the sample, thereby restricting the movement of the end of the sample in the vertical direction within the limiting grooves.

[0012] The above technical solution enables the two ends of the four-curved surface sample to be precisely embedded in the limiting groove of the first stop and limited by the first stop, preventing the four-curved surface sample from shifting left and right (i.e., in the length direction of the sample) during the clamping and adjustment process, which is conducive to the accurate centering and positioning of the sample.

[0013] Preferably, a limiting protrusion is formed in the middle of the second stop, and limiting notches are symmetrically opened on both sides of the rigid substrate parallel to the length direction of the sample. The limiting protrusion and the limiting notches cooperate to limit the rigid substrate.

[0014] Through the above technical solution, corresponding limiting notches are opened on the rigid substrate of the fixture assembly. The limiting notches are set on both sides of the rigid substrate parallel to the length direction of the sample. The upper limit protrusion of the second stop cooperates with the limiting notches on both sides of the rigid substrate, which is conducive to the rigid substrate being embedded in the middle between the second stop. At the same time, it avoids the overall and relative displacement of the two rigid substrates in the horizontal direction during thickness adjustment, effectively shortening the adjustment time.

[0015] Preferably, the rigid substrate is I-shaped, and each of the four corners of the rigid substrate is provided with threaded holes that match the fastening bolts. The fastening bolts are screwed into the threaded holes with the bolt head on top and the bolt shaft facing downwards.

[0016] Preferably, the bottom plane of the elastic arc-shaped adhesive block is provided with a positioning groove, and the side of the rigid substrate that is in contact with the elastic arc-shaped adhesive block is provided with a positioning strip that matches the positioning groove.

[0017] Preferably, the universal level is magnetically attached and is magnetically attached to the upper surface of the rigid substrate. The angle adjustment accuracy of the universal level is 3'.

[0018] The beneficial effects of this utility model are as follows: This application utilizes a combination of a base, a universal level, a dial indicator, and a fixture assembly. The centering and limiting components on the base improve the accuracy and efficiency of symmetrically clamping fatigue specimens. Countersunk holes are provided on the base, and a dial indicator is mounted there, allowing the fixture assembly to remain firmly attached to the base during thickness adjustment. Continuous measurement of the fixture assembly's thickness using the dial indicator improves the accuracy of thickness measurement and the efficiency of thickness adjustment (specimen clamping stress adjustment). The universal level ensures uniform thickness on all sides of the fixture, guaranteeing consistent clamping stress distribution and effectively reducing the probability of compressive instability when testing four-curved surface specimens on the fatigue testing machine, thus improving the reliability of test results. This device enables rapid installation and clamping stress adjustment of four-curved surface specimens on the fixture assembly, improving the installation efficiency and testing accuracy of compressive fatigue testing of resin fiber composite materials. The benefits are even more pronounced in batch testing. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of an embodiment of this application.

[0020] Figure 2 This is a structural schematic diagram to illustrate the clamping state of the clamp assembly in the embodiments of this application.

[0021] Figure 3 This is a side view showing the clamping state of the clamp assembly in the embodiments of this application.

[0022] Figure 4 This is a schematic diagram illustrating the base structure in an embodiment of this application.

[0023] Figure 5 This is a three-dimensional structural diagram of the four-curved surface specimen in this application.

[0024] Explanation of reference numerals in the attached drawings: 1. Base; 101. Countersunk hole; 102. First stop block; 103. Second stop block; 104. Support; 105. Limiting groove; 106. Limiting protrusion; 107. Column; 108. Cross arm; 2. Fixture assembly; 201. Rigid base plate; 202. Elastic arc-shaped rubber block; 203. Fastening bolt; 204. Positioning strip; 3. Sample; 301. Arc-shaped working section; 4. Universal level; 5. Dial indicator. Detailed Implementation

[0025] The following is in conjunction with the appendix Figure 1-5 The present invention will be described in further detail below.

[0026] This invention provides an auxiliary device for precisely adjusting the clamping stress of a four-curved surface specimen, such as... Figure 1 As shown, it includes a base 1, a fixture assembly 2, a dial indicator 5 and a universal level 4, and the specimen 3 is a fatigue test four-curved surface specimen.

[0027] like Figure 2 and Figure 3 As shown, the fixture assembly 2 includes two rigid base plates 201, two elastic arc-shaped rubber blocks 202 and four fastening bolts 203. The two rigid base plates 201 are arranged in parallel and connected by the fastening bolts 203. The lower rigid base plate 201 is mounted on the base 1, and the universal level 4 is positioned at the center of the upper surface of the upper rigid base plate 201.

[0028] Two elastic arc-shaped adhesive blocks 202 are arranged facing each other between two rigid substrates 201. The sample 3 is clamped between the two elastic arc-shaped adhesive blocks 202. The arc-shaped top surface of the elastic arc-shaped adhesive block 202 is in contact with the arc-shaped working section 301 of the sample 3, and the bottom surface of the elastic arc-shaped adhesive block 202 is in contact with the rigid substrate 201.

[0029] like Figure 1 and Figure 2 As shown, the base 1 is equipped with a centering and limiting component for limiting the center position of the sample 3 and a support 104 for mounting the dial indicator 5. The support 104 is equipped with a column 107, and a horizontal arm 108 is held on the column 107 with adjustable height. The end of the horizontal arm 108 holds the dial indicator 5, and the probe of the dial indicator 5 is vertically downward and directly facing the upper surface of the universal level 4.

[0030] Specifically, such as Figure 2 and Figure 3 As shown, the rigid base plate 201 of the clamp assembly 2 is I-shaped, and each of the four corners of the rigid base plate 201 has threaded holes that mate with the fastening bolts 203. The fastening bolts 203 are screwed into the threaded holes with the screw head facing up and the screw shaft facing down, making it easy for the operator to tighten the fastening bolts 203. Figure 4As shown, the base 1 has a countersunk hole 101 on its surface for accommodating the screw. The diameter of the countersunk hole 101 is larger than the outer diameter of the screw. When the tightening bolt 203 is turned too far, the bottom of the screw will penetrate into the countersunk hole 101 and will not press against the surface of the base 1. This can reduce the need to pick up and put down the clamp assembly 2 due to thickness adjustment, and also avoid measurement errors caused by unevenness of the clamp assembly 2 during use.

[0031] like Figures 1 to 4 As shown, the centering and limiting assembly includes two first stops 102 that limit the ends of the sample 3 along its length and two second stops 103 that limit the rigid substrate 201. The second stops 102 are located on both sides of the sample 3 along its length. The first stops 102 have symmetrically opposite limiting grooves 105 in the vertical direction. The width of the limiting grooves 105 matches the width of the sample 3, and the ends of the sample 3 are restricted to move vertically within the limiting grooves 105.

[0032] A limiting protrusion 106 is formed in the middle of the second stop 103. A limiting notch is symmetrically opened on both sides of the rigid substrate 201 parallel to the length direction of the sample 3. The limiting protrusion 106 and the limiting notch of the rigid substrate 201 limit each other, so that the rigid substrate 201 is centered and embedded between the second stop 106. At the same time, it avoids the overall and relative displacement of the two rigid substrates 201 in the horizontal direction during thickness adjustment, effectively shortening the adjustment time and improving work efficiency.

[0033] In use, the two ends of the sample 3 along its length can be accurately embedded in the limiting groove 105, and the limiting protrusion 106 can be accurately embedded in the limiting notches on both sides of the rigid substrate 201, ensuring that the sample 3 is accurately centered.

[0034] Furthermore, such as Figure 3 As shown, in one specific embodiment, the bottom plane of the elastic arc-shaped adhesive block 202 is provided with a positioning groove, and the side of the rigid substrate 201 that is in contact with the elastic arc-shaped adhesive block 202 is provided with a positioning strip 204 that matches the positioning groove. During installation, the positioning strip 204 is embedded in the positioning groove to realize the combination and positioning of the elastic arc-shaped adhesive block 202 and the rigid substrate 201, thereby improving clamping stability.

[0035] like Figure 2 and Figure 3As shown, in one specific embodiment, the universal level 4 is magnetically attached to the upper surface of the rigid substrate 201 by magnetic force. The angle adjustment accuracy of the universal level 4 is 3'. This accuracy can control the relative thickness deviation of the clamp assembly 2 in the front and back / left and right within 0.05mm. When tightening the fastening bolts 203 at the four corners, the uniformity of the height of each side of the clamp assembly 2 can be ensured with the assistance of the universal level 4, thereby ensuring the uniformity of the deformation and clamping stress of each point of the sample 3 in contact with the elastic arc surface rubber block 202.

[0036] The following steps are included when using this utility model:

[0037] S1. Connect the two rigid base plates 201 of the fixture assembly 2 with bolts (the bolts do not need to be tightened at this time), and insert the fatigue sample 3 of the four-curved surface specification in the middle of the elastic arc surface rubber block 202 of the assembly.

[0038] S2. Place the fixture assembly 2 containing the sample 3 inside the base 1. Ensure that the sample 3 and the fixture assembly 2 are symmetrically centered by the centering and limiting components on the four sides of the base 1, and make the four corner fastening bolts 203 embedded in the countersunk holes 101 on the base 1 to ensure that the lower surface of the fixture assembly 2 is in contact with the surface of the base 1.

[0039] S3. Place a magnetic high-precision universal level 4 in the center of the upper part of the fixture assembly 2, and adjust the position of the dial indicator 5 so that its conical probe contacts the upper surface of the universal level 4 and is centered.

[0040] S4. Use dial indicator 5 to measure the initial total thickness of the middle part of the fixture assembly 2.

[0041] S5. Based on the clamping stress value of sample 3, calculate the corresponding deformation of elastic arc surface rubber block 202 and the target total clamping thickness of clamp assembly 2.

[0042] S6. Tighten the four corner bolts 203 in sequence and adjust them simultaneously, and observe the reading of dial indicator 5 in real time until the center of the fixture assembly 2 reaches the target total thickness.

[0043] S7. Check the consistency of thickness adjustment on each side of the fixture assembly 2 according to the indication of the universal level 4. If there is any inconsistency, fine-tune the tightening depth of the four corner fastening bolts 203 until the bubble in the universal level 4 is within the 3' scale range. The reading of the dial indicator 5 should remain unchanged when fine-tuning the fastening bolts 203. This means that the fixture assembly 2 reaches the target total thickness in all directions, and the clamping stress at each point of the sample 3 is consistent.

[0044] S8. Take the anti-instability fixture assembly 2, which has installed the sample 3 and completed the clamping stress adjustment, out of the base 1 and clamp it on the fatigue testing machine fixture according to the principle of symmetry and coaxiality. Perform the compressive fatigue test of the four-curved fiber reinforced composite material in accordance with relevant standards such as GB / T 35465.

[0045] Understandably, in other usage steps of this embodiment, the rigid substrate 201 located below can be placed into the base 1 first, and then the sample 3 and the rigid substrate 201 located above can be placed into the base 1 in sequence, followed by the placement of the magnetic universal level 4 and the tightening of the mounting bolts 203, and the measurement, adjustment and clamping of the sample 3 can be performed.

[0046] The principle of this utility model for an auxiliary device for precisely adjusting the clamping stress of a four-curved surface sample is as follows: A base 1, a universal level 4, a dial indicator 5, and a clamp assembly 2 are combined. A first stop 102 and a second stop 103 are set on the base 1. The first stop 102, which limits the two ends of the sample 3 along its length, ensures that both ends of the four-curved surface sample 3 are within the limiting grooves 105 of the first stop 102, preventing the sample 3 from shifting left or right during clamping and adjustment. A corresponding limiting notch is formed on the rigid base plate 201 of the clamp assembly 2. The upper limit protrusion 106 of the second stop 103 engages with the limiting notches on both sides of the rigid base plate 201, guiding the rigid base plate 201 to be centered between the second stop 103. This also prevents the two rigid base plates 201 from shifting horizontally or relative during thickness adjustment, improving the accuracy and efficiency of clamping and adjusting the sample 3. A countersunk hole 101 is made on the base 1 and a dial indicator 5 is installed so that the fixture assembly 2 can be attached to the base 1 without leaving it during the thickness adjustment process. The continuous measurement of the thickness of the fixture assembly 2 by the dial indicator 5 can improve the measurement accuracy of the fixture thickness and the efficiency of the thickness adjustment. The universal level 4 ensures that the thickness of each side of the fixture is uniform and consistent, ensuring the consistency of the clamping stress distribution, effectively reducing the probability of compressive instability when the four-curved surface specimen 3 is placed on the fatigue testing machine. The device can quickly complete the installation of the four-curved surface specimen 3 on the fixture assembly 2 and the clamping stress adjustment, improving the installation efficiency and testing accuracy of the compressive fatigue test of resin fiber composite materials.

[0047] The above specific embodiments are merely explanations of this application and are not intended to limit this application. After reading this specification, those skilled in the art can make modifications to these embodiments without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. An auxiliary device for precisely adjusting the clamping stress of a four-curved surface specimen, characterized in that, It includes a base (1), a clamp assembly (2), a universal level (4) and a dial indicator (5); the clamp assembly (2) includes two rigid base plates (201), two elastic arc-shaped rubber blocks (202) arranged opposite to each other between the two rigid base plates (201), and fastening bolts (203) connecting the two rigid base plates. Two rigid substrates (201) are arranged in parallel. The lower rigid substrate (201) is placed on the base (1). The universal level (4) is placed at the center of the upper surface of the upper rigid substrate (201). The sample (3) is installed between the elastic arc surface adhesive blocks (202). The arc-shaped top surface of the elastic arc surface adhesive block (202) is in contact with the arc-shaped working section (301) of the sample (3). The base (1) includes a centering and limiting component for limiting the middle position of the sample (3) and a support (104) for mounting the dial indicator (5). The probe of the dial indicator (5) is vertically downward and directly faces the center of the upper surface of the universal level (4). The top of the base (1) has a countersunk hole (101) corresponding to the position of the fastening bolt (203). The diameter of the countersunk hole (101) is larger than the outer diameter of the fastening bolt (203).

2. The auxiliary device for precisely adjusting the clamping stress of a four-curved surface specimen according to claim 1, characterized in that, The centering limiting component includes two first blocks (102) that limit the two ends of the sample (3) along its length and two second blocks (103) that limit the rigid substrate (201) along its length. The second blocks (103) are located on both sides of the sample (3) along its length.

3. The auxiliary device for precisely adjusting the clamping stress of a four-curved surface specimen according to claim 2, characterized in that, The first stop (102) has symmetrically opposite limiting grooves (105) in the vertical direction. The width of the limiting groove (105) matches the width of the sample (3), thus restricting the movement of the end of the sample (3) in the vertical direction within the limiting groove (105).

4. The auxiliary device for precisely adjusting the clamping stress of a four-curved surface specimen according to claim 2, characterized in that, A limiting protrusion (106) is formed in the middle of the second stop (103). The rigid substrate (201) has symmetrical limiting notches on both sides parallel to the length direction of the sample (3). The limiting protrusion (106) is matched with the two sides of the rigid substrate (201) for limiting.

5. The auxiliary device for precisely adjusting the clamping stress of a four-curved surface specimen according to claim 1, characterized in that, The rigid substrate (201) is in the shape of an "I". Each of the four corners of the rigid substrate (201) is provided with a threaded hole that matches the fastening bolt (203). The fastening bolt (203) is screwed into the threaded hole with the screw head on top and the screw shaft on the bottom.

6. The auxiliary device for precisely adjusting the clamping stress of a four-curved surface specimen according to claim 1, characterized in that, The bottom plane of the elastic arc-shaped adhesive block (202) is provided with a positioning groove, and the side of the rigid substrate (201) that is in contact with the elastic arc-shaped adhesive block (202) is provided with a positioning strip (204) that matches the positioning groove.

7. The auxiliary device for precisely adjusting the clamping stress of a four-curved surface specimen according to claim 1, characterized in that, The universal level (4) is magnetically attached and is magnetically attached to the upper surface of the rigid substrate (201). The angle adjustment accuracy of the universal level (4) is 3'.

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