Mechanical compression creep test device and method

Abstract

The application belongs to the field of compression creep test, and particularly relates to a mechanical compression creep test device and method, wherein the device comprises a support, a rotating shaft adjusting assembly, a sector arm, a force applying pressure rod and a weight mounting disc; the rotating shaft adjusting assembly comprises a guide rail assembly arranged on the support, a rotating shaft arranged on the guide rail assembly and an adjusting driving part for driving the rotating shaft to move linearly along the guide rail assembly; the center of the sector arm is hingedly arranged on the rotating shaft, a connecting rope is vertically arranged on the arc-shaped side of the sector arm, and the other end of the connecting rope is connected with the weight mounting disc; the force applying pressure rod is slidingly arranged on the support, the sliding direction of the force applying pressure rod is the vertical direction, the lower end of the sector arm slidingly abuts against the upper end of the force applying pressure rod, and the lower end of the force applying pressure rod acts on the test piece; the application can continuously adjust the pressure applied on the pressure rod, and can realize constant force loading when the test sample has large creep deformation; the experimental device has simple structure, low cost and constant loading.

Description

Technical Field

[0001] This invention belongs to the field of compression creep testing, specifically relating to a mechanical compression creep testing device and method. Background Technology

[0002] Solid propellant is a major component of solid rocket motors, accounting for over 90% of the engine's total weight. The propellant material is a typical viscoelastic material. During long-term storage, the solid propellant grains inside the engine will undergo creep deformation under their own gravity. Accurately predicting the creep characteristics of the propellant grains is crucial for formulating engine storage strategies and accurately predicting engine lifespan, and is of great significance for the safe and reliable use of aircraft. Currently, research on the long-term creep characteristics of solid rocket motor propellant grains often involves lengthy and costly whole-engine testing, making it impossible to quickly obtain the required test results. Therefore, research on the creep characteristics of propellant grains typically utilizes creep testing machines based on the principle of stress-temperature creep acceleration, providing a method for predicting the long-term creep state of the propellant material through short-term testing.

[0003] Currently, there are two main types of testing machines used for material creep measurement: mechanical and electronic. However, these two types of creep testing machines are primarily suitable for testing the creep performance of hard materials such as metals and rocks with relatively small creep compliance. They are ill-suited for testing the creep performance of soft materials such as propellants with large creep compliance. Conventional mechanical creep testing machines are mostly applicable to metals, rocks, and hard composite materials. These types of creep tests are characterized by high creep stress, small creep deformation, and low loading control precision. Propellant materials, compared to metals and rocks, have characteristics such as low modulus, fast creep rate, and large creep deformation. Therefore, existing mechanical creep testing machines are not suitable for measuring the creep performance of propellants. In addition, existing mechanical creep testing machines generally use a lever structure for loading, which has two problems: first, it does not consider the effect of lever arm changes due to lever tilting on the loading force value, making it impossible to achieve constant force loading for tests with large creep deformation; second, the test load adjustment is usually achieved by adding or subtracting weights, resulting in a step-like discontinuous change in the loading load, which cannot provide a controllable and continuous loading load for the test. Existing electronic creep testing machines are mostly used for short-term creep performance testing of materials. When conducting long-term creep tests, they waste a lot of power resources, and the force sensor will inevitably drift under long-term operation, which cannot guarantee the long-term stability of the data. Therefore, they are not suitable for determining the long-term creep performance of propellant materials.

[0004] Take the following three compression creep testing machines as examples.

[0005] Chinese patent "CN202110354227.6 A Simulation Test Device and Method for Compression Creep of Soft Rock in a Similar Environment" describes a device for simulating compression creep of soft rock in a similar environment. Utilizing lever and wheel transmission principles, it applies long-term pressure to rock samples using weights, enabling the study of creep mechanical properties of rock masses under different confining pressures and immersion conditions. However, this device relies solely on increasing or decreasing weights to achieve graded stress loading, resulting in limited and discontinuous accuracy of the loading force. The relative position of the indenter and the bearing of the pressure rod is fixed; as the weights are applied and the pressure rod rotates downwards, the lever arm ratio between the weights and the indenter to the fulcrum changes, thus altering the loading force. Furthermore, the weight of the pressure rod and the tray is not considered, meaning the specimen is already under pressure before the test. Given the relatively small creep stress experienced by solid propellants, the error of this experimental device is not negligible; therefore, this compression creep device is not suitable for composite propellant materials.

[0006] Chinese patent "CN202010699173.2 A Multi-Station Integrated Environmental Fiberglass Bending Creep Testing Device and Method" describes a multi-station integrated environmental fiberglass bending creep testing device. This device includes a lever loading device, a temperature control device, and a data acquisition device. A balance weight is installed at one end of the crossbeam, and a loading weight is installed at the other end. The crossbeam can be adjusted to a horizontal position, ensuring the force on the specimen is zero before the test. Furthermore, the device can perform bending creep tests under different test forces by adjusting the weight of the loading weight and the position of the pressure bar on the crossbeam. However, this compression creep testing machine can only perform graded loading on the specimen, and there are limitations in improving its ability to maintain constant test stress or constant test loading force.

[0007] Chinese patent "CN201811178623.2 A Mechanical High-Temperature Creep Testing Machine with Automatic and Precise Loading" describes a mechanical high-temperature creep testing machine capable of automatic and precise loading. Under the control of a control system, it can automatically load weights and precisely fine-tune the rider, solving problems such as slow loading and inability to perform cyclic load loading in previous manual loading methods. The combined loading method of weights and rider enables continuous loading with high precision. However, this method still has shortcomings in maintaining constant test stress or test loading force, and the complex control system leads to a complex machine structure, high cost, and high energy consumption during long-term creep testing, resulting in low economic efficiency. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a mechanical compression creep testing device and method that can achieve precise loading force or ensure constant stress in the specimen.

[0009] This invention provides a mechanical compression creep testing device, including a support, a rotating shaft adjustment assembly, a sector arm, a force-applying rod, and a weight mounting plate;

[0010] The rotating shaft adjustment assembly includes a guide rail assembly mounted on a bracket, a rotating shaft mounted on the guide rail assembly, and an adjustment drive component that drives the rotating shaft to move linearly along the guide rail assembly.

[0011] The central end of the fan-shaped arm is hinged to the rotating shaft, and a connecting rope is vertically arranged on the arc-shaped side of the fan-shaped arm. The other end of the connecting rope is connected to the weight mounting plate.

[0012] The force-applying rod is slidably mounted on the support, and the sliding direction of the force-applying rod is vertical. The lower edge of the fan-shaped arm slides against the upper end of the force-applying rod, and the lower end of the force-applying rod acts on the specimen.

[0013] Furthermore, a roller is provided at the upper end of the force-applying rod, and the roller rolls in cooperation with the lower edge of the fan-shaped arm.

[0014] Furthermore, a guide groove is provided along the lower edge of the fan-shaped arm, and the roller is rotatably disposed within the guide groove.

[0015] Furthermore, a groove is provided on the arc-shaped edge of the fan-shaped arm, and the connecting rope is disposed in the groove.

[0016] Furthermore, the guide rail assembly includes two parallel guide rails and a slider slidably mounted on the two guide rails. The rotating shaft is rotatably or fixedly mounted on the two sliders. The adjustment drive includes a lead screw rotatably mounted on a bracket and a nut cooperating with the lead screw. The nut is connected to the rotating shaft.

[0017] Furthermore, the support includes a top plate and a bottom plate arranged opposite to each other, the top plate and the bottom plate being connected to each other by a number of guide columns, the rotating shaft adjustment assembly and the fan-shaped arm being arranged on the top plate, the force-applying pressure rod being vertically inserted through the top plate, and a specimen receiving space being formed between the top plate and the bottom plate.

[0018] Furthermore, the support also includes a side plate that encloses the specimen receiving space to form a box space, and also includes a temperature regulating component disposed within the box space.

[0019] Furthermore, a balance bar is provided at the end of the fan-shaped arm away from the weight mounting plate, and a balance weight is slidably mounted on the balance bar.

[0020] Furthermore, the force-applying rod is equipped with a displacement sensor for detecting the compression of the test piece, and also includes a pressure sensor for detecting the pressure of the test piece.

[0021] This invention also provides a constant stress mechanical compression creep test method for specimens, using a mechanical compression creep test apparatus, comprising the following steps:

[0022] S1. Adjust the support to level the test device;

[0023] S2. Adjust the position of the balance weights on the balance bar so that the weight of the sector arm is balanced and the pressure acting on the force-applying bar is zero.

[0024] S3. Based on the stress requirements applied to the specimen, estimate the weight of the weights that need to be added to the weight mounting plate, and precisely adjust the distance between the rotating shaft and the force-applying rod through the rotating shaft adjustment component to obtain the required loading force of the force-applying rod;

[0025] The distance adjustment model between the rotating shaft and the force-applying rod is as follows:

[0026]

[0027] In the formula, L is the distance between the rotating shaft and the contact point of the force-applying rod, G is the weight of the weight and the weight mounting plate, L0 is the distance from the tangent point of the connecting rope and the sector arm to the axis of the rotating shaft, and F is the loading force applied to the force-applying rod, which is determined by the following formula:

[0028] F = σ 试 A

[0029] σ 试 Let A be the creep stress of the compressive specimen, and let A be the cross-sectional area of ​​the specimen.

[0030] S4. Install the specimen onto the bracket, so that the lower end of the force-applying rod abuts against the specimen;

[0031] S5. The displacement sensor continuously detects the vertical displacement of the applied pressure rod and adjusts the position of the rotating shaft according to the constant stress rotating shaft adjustment model to change the loading force value and ensure the constant stress of the specimen.

[0032] The constant stress rotating shaft adjustment model is as follows:

[0033]

[0034] In the formula, ΔL represents the displacement that the shaft needs to be adjusted, h0 represents the initial height of the specimen, and Δh represents the creep change calculated based on the displacement h displayed by the displacement sensor.

[0035] The beneficial effects of the present invention are that the mechanical compression creep testing device provided by the present invention can perform different test modes to cope with different specimen properties. Specifically, it can be divided into constant loading force compression creep test, constant stress compression creep test and conventional compression creep test corresponding to large creep deformation of the tested material.

[0036] Firstly, this invention enables constant-load creep testing. Through the specific arrangement of the fan-shaped arm, connecting rope, rotating shaft, and force-applying lever, without moving the rotating shaft, during a long-term compression creep test, the distance between the point of tangency of the connecting rope to the fan-shaped arm and the rotating shaft (i.e., the lever arm of the weights and the weight mounting plate) remains constant. Furthermore, the vertical distance from the force-applying lever to the rotating shaft also remains constant (the lever arm of the force acting on the force-applying lever). This weight loading structure, combined with a movable rotating shaft, achieves a constant loading force, eliminating the influence of the deflection of the loading lever (fan-shaped arm) angle on the applied load, maintaining a constant load, and meeting the requirements for large deformation and constant-load creep tests.

[0037] Secondly, this invention enables constant stress compression creep testing. When conducting compression creep tests on specimens with large creep deformation, the specimen undergoes significant compression creep deformation under external load (the specimen height decreases, and the cross-sectional area increases). If the loading force remains constant, the stress on the specimen will decrease due to the increased cross-sectional area, which may not meet the constant stress test requirements for a specific specimen. This invention, however, can detect or calculate the change in the specimen's cross-sectional area and correspondingly adjust the position of the rotating shaft to achieve stepless adjustment of the loading force, ensuring that the stress on the specimen remains constant, ultimately achieving constant stress loading testing of the specimen.

[0038] Furthermore, this invention is applicable to creep tests of materials with low modulus and large creep deformation, as well as materials with high modulus, high creep stress, and small creep deformation. Specifically, the high-stress compression creep test can be performed by adjusting the weight of the weights to apply different loads, and the position of the rotating shaft can be adjusted via the rotating shaft adjustment assembly to achieve continuous, stepless, and precise adjustment of the test loading force. During continuous and precise adjustment, because the weights are connected by a sector arm, the specimen is compressed and deformed, causing the sector arm to rotate. However, the weight of the weights and the lever arm on the sector arm remain constant, achieving constant force loading compared to conventional lever loading methods. Additionally, adjusting the position of the rotating shaft changes the lever arm, amplifying the loading force. Small adjustments to the shaft position achieve large changes in loading force. Therefore, this testing device provides two loading force adjustment methods: adjusting the weight of the weights and adjusting the position of the rotating shaft. The former is discontinuous loading force adjustment, while the latter is continuous and precise loading force adjustment. Moreover, the experimental device of this invention has a simple structure, low cost, and high loading accuracy. Attached Figure Description

[0039] Appendix Figure 1 This is a schematic diagram of the first angle structure of the present invention;

[0040] Appendix Figure 2This is a schematic diagram of the second angle structure of the present invention;

[0041] Appendix Figure 3 For the present invention Figure 2 A magnified view of a section at point A in the middle;

[0042] Appendix Figure 4 This is a front sectional view of the present invention;

[0043] Appendix Figure 5 This is a schematic diagram of the lever arm based on the sector-shaped lever principle in this invention;

[0044] Appendix Figure 6 This is a schematic diagram showing the change in lever arm relationship after the sector arm moves in this invention;

[0045] Appendix Figure 7 This is a schematic diagram showing the change in the lever arm relationship during the rotation of the sector arm in an embodiment of the present invention with a balancing weight.

[0046] In the diagram, 1-bracket; 101-top plate; 102-bottom plate; 103-guide column; 104-specimen receiving space; 2-rotating shaft adjustment assembly; 201-guide rail assembly; 2011-guide rail; 2012-slider; 202-rotating shaft; 203-adjustment drive component; 2031-lead screw; 2032-nut; 20321-connecting plate; 2033-bearing seat; 2034-rotating handle; 3-fan-shaped arm; 301-guide groove; 302-line groove; 4-force application rod; 401-roller; 5-weight mounting plate; 6-connecting rope; 7-balance bar; 8-balance weight; 9-pressure sensor; 10-displacement sensor; 1001-moving plate; 1002-detection unit; 11-weight; 12-specimen. Detailed Implementation

[0047] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0048] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0049] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0050] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection, an electrical connection, a physical connection, or a wireless communication connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two elements or the interaction between two elements, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0051] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0052] As attached Figure 1-7 As shown, the present invention provides a mechanical compression creep testing device, comprising a support 1, a rotating shaft adjustment assembly 2, a fan-shaped arm 3, a force-applying rod 4, and a weight mounting plate 5;

[0053] The rotating shaft adjustment assembly 2 includes a guide rail assembly 201 mounted on the bracket 1, a rotating shaft 202 mounted on the guide rail assembly 201, and an adjustment drive 203 that drives the rotating shaft 202 to move linearly along the guide rail assembly 201, that is, the rotating shaft 202 can move linearly on the bracket 1.

[0054] The central end of the fan-shaped arm 3 is hinged to the rotating shaft 202. A connecting rope 6 is vertically arranged on the arc side of the fan-shaped arm 3. The other end of the connecting rope 6 is connected to the weight mounting plate 5. This arrangement allows the weight mounting plate 5 to always apply vertical force to the fan-shaped arm 3, so that the direction of the force and the direction of the lever arm always remain perpendicular.

[0055] The force-applying rod 4 is slidably mounted on the support 1. Preferably, a guide hole is vertically provided on the panel of the support 1, and the force-applying rod 4 is slidably mounted in the guide hole. The sliding direction of the force-applying rod 4 is vertical. The lower edge of the fan-shaped arm 3 slides against the upper end of the force-applying rod 4. The lower end of the force-applying rod 4 acts on the specimen 12. The weight of the fan-shaped arm 3 and the weight of the weight 12 are both applied as loading forces to the upper end of the force-applying rod 4 and transmitted to the specimen 12 by the force-applying rod 4 to perform a compression creep test on the specimen 12.

[0056] The mechanical compression creep testing device provided by this invention can be used for creep testing of materials with different creep deformation properties. Specifically, it can be divided into constant loading force compression creep test with large creep deformation, constant stress compression creep test, and compression creep test with small creep deformation.

[0057] Firstly, this invention enables constant-load creep testing. Conventional compression creep testing devices, such as the one described in Chinese patent "CN202110354227.6 A Simulation Test Device and Method for Compression Creep in Soft Rock," employ a loading method that, during compression, causes the pressure bar to tilt from horizontal to inclined. This shortens the lever arm of the weights acting on the bearing, resulting in a change in the loading force acting on the guide column, thus failing to achieve a constant loading force. Adjusting the loading force using this method requires adding or removing weights from the weight pan, but this simple addition or removal of weights cannot achieve stepless adjustment of the loading force. This application, through the fan-shaped arm 3, connecting rope 6, rotating shaft 202, and force-applying lever 4 and their specific configuration, ensures that during a long-term compression creep test without moving the rotating shaft 202, the specimen 12 undergoes compression creep deformation (the height of the specimen 12 decreases, and the cross-section increases). The distance between the tangent point of the connecting rope 6 to the fan-shaped arm 3 and the rotating shaft 202 (i.e., the lever arm of the weight 12 and the weight mounting plate 5) remains constant, and the vertical distance from the force-applying lever 4 to the rotating shaft 202 also remains constant (the lever arm of the force acting on the force-applying lever 4). By combining this weight loading structure with the movable rotating shaft 202, precise and constant loading is achieved. This eliminates the influence of the deflection of the loading lever (fan-shaped arm 3) angle on the applied load during the test, maintaining the constantness of the load and meeting the test requirements for precise and constant loading of large creep deformation.

[0058] Secondly, this invention can achieve constant stress compression creep testing, especially for materials with large creep deformation such as solid propellants. When conducting a constant stress compression creep test on a specimen 12 with large creep deformation, the specimen 12 will undergo compression creep deformation during loading (the height of the specimen 12 decreases, and the cross-sectional area increases). If the loading force remains constant, the stress on the specimen 12 will decrease due to the increased cross-sectional area, which does not meet the constant stress test requirements. This invention can detect or calculate the change in the cross-sectional area of ​​the specimen 12 and correspondingly adjust the position of the rotating shaft 202 to achieve stepless adjustment of the loading force, ensuring that the stress on the specimen 12 remains constant, ultimately achieving a constant stress loading test for the specimen 12.

[0059] Furthermore, this invention is also applicable to creep tests on specimens with small creep deformation. Specifically, the small deformation compression creep test can be performed by adjusting the weight of the weight 11 to apply different loads under different conditions, and the position of the rotating shaft 202 can be adjusted by the rotating shaft adjustment component 2 to achieve continuous, stepless, and precise adjustment of the test load. During continuous and precise adjustment, because the weight 11 is connected by the fan-shaped arm 3, the specimen 12 is compressed and deformed, causing the fan-shaped arm 3 to rotate. However, the weight of the weight 11 and the lever arm on the fan-shaped arm 3 remain unchanged (when loading using the conventional lever principle, the lever will deflect after the specimen deforms, causing the length of the lever arm to change accordingly). Therefore, compared to the conventional lever loading method, constant force loading is achieved. In addition, adjusting the loading force by adjusting the rotating shaft 202 also has an amplification effect; a small adjustment of the rotating shaft 202 can achieve a large change in loading force. Thus, this test device has two loading force adjustment methods: adjusting the weight of the weight 12 and adjusting the position of the rotating shaft 202. The former is discontinuous loading force adjustment, while the latter is continuous and precise loading force adjustment. In addition, the experimental device of the present invention has a simple structure, low cost, and continuous loading, and the loading force is not affected by lever deflection, thus achieving constant force loading.

[0060] In one embodiment, the upper end of the force-applying rod 4 is provided with a roller 401, which rolls with the lower edge of the fan-shaped arm 3, effectively reducing friction caused by changes in the contact point when the fan-shaped arm 3 moves downward, and further ensuring the constant vertical force of the load.

[0061] In one embodiment, a guide groove 301 is provided at the lower edge of the fan-shaped arm 3, and the roller 401 is rolled in the guide groove 301, which can provide a guiding effect for the movement of the fan-shaped arm 3 and ensure that the movement direction of the fan-shaped arm 3 does not deviate.

[0062] In one embodiment, a groove 302 is provided on the arc-shaped edge of the fan-shaped arm 3, and the connecting rope 6 is disposed in the groove 302. The groove 302 can improve the stability of the connecting rope 6.

[0063] In one embodiment, the guide rail assembly 201 includes two parallel guide rails 2011 and sliders 2012 slidably disposed on the two guide rails. The rotating shaft 202 is rotatably or fixedly disposed on the two sliders 2012. When the rotating shaft 202 is rotatably disposed on the two sliders 2012, the rotating shaft 202 is fixedly connected to the center of the sector arm 3; conversely, when the rotating shaft 202 is fixedly disposed on the two sliders 2012, the rotating shaft 202 is rotatably connected to the center of the sector arm 3. The adjusting drive component 203 includes a lead screw 2031 rotatably disposed on the bracket 1 and a nut 2032 cooperating with the lead screw 2031. The nut 2032 is connected to the rotating shaft 202. When the two sliders 2012 are in contact with each other, the nut 2032 is rotatably connected to the rotating shaft 202. When the rotating shaft 202 is fixedly mounted on the two sliders 2012, the nut 2032 is fixedly connected to the rotating shaft 202. Specifically, both ends of the lead screw 2031 are rotatably fixed to the bracket 1 via bearing seats 2033, and one end of the lead screw 2031 is connected to a rotating handle 2034 for easy adjustment by the operator. In addition, the nut 2032 is fixedly connected to the rotating shaft 202 via two connecting plates 20321, thereby driving the rotating shaft 202 to move linearly along the guide rail 2011. Preferably, a scale is also provided on the adjusting handle 2034 or the guide rail 2011 to facilitate the operator in determining the amount of displacement to be adjusted. In this embodiment, the guide rail assembly 201 and the adjusting drive component 203 have a simple overall structure, precise and convenient adjustment, and are characterized by low cost and stable and reliable structure.

[0064] In one embodiment, the support 1 includes a top plate 101 and a bottom plate 102 disposed opposite to each other. The top plate 101 and the bottom plate 102 are interconnected by a plurality of guide columns 103. The rotating shaft adjustment assembly 2 and the fan-shaped arm 3 are disposed on the top plate 101. The force-applying pressure rod 4 is vertically inserted through the top plate 101. A specimen receiving space 104 is formed between the top plate 101 and the bottom plate 102. In this embodiment, the support 1 has a simple structure and can divide the force-applying part and the specimen into zones, thus rationally allocating the area. A leveling component can be provided on the top plate 101 to facilitate the overall leveling of the device.

[0065] In one embodiment, the support 1 further includes a side plate that encloses the specimen receiving space 104 to form a box space. It also includes a temperature regulating component disposed in the box space. In this embodiment, one of the side plates can be used as a door panel to facilitate the disassembly and assembly of the specimen 12. In addition, by setting the temperature regulating component, compression creep tests can be carried out under high temperature or low temperature environments.

[0066] refer to Figure 7 In one embodiment, a balance bar 7 is also provided at the end of the fan-shaped arm 3 facing away from the weight mounting plate 5. Figures 1-2 (Not shown), a balance weight 8 is slidably mounted on the balance rod 7. In this embodiment, the balance rod 7 and the balance weight 8 can be used to balance the weight of the sector arm 3, so that the force on the force-applying rod 4 is zero before the test begins. In addition, the balance weight 8 can also realize continuous and precise adjustment of the loading force, and there is no amplification effect during the adjustment process. Therefore, fine and precise adjustment can be achieved, so that this test device has three loading force adjustment methods: adjusting the weight of the weight 12, adjusting the position of the rotating shaft 202, and adjusting the position of the balance weight 8. The first is discontinuous large-range adjustment of the loading force, the second is continuous large-range precise adjustment of the loading force, and the third is continuous small-range precise adjustment of the loading force. The loading force can be adjusted precisely and quickly according to the test needs. In constant loading force test and constant stress loading test, the balance weight 8 is generally used to balance the self-weight of the sector arm 3, which facilitates the adjustment of loading force or stress. In addition, in the small deformation compression creep test, since the movement of the rotating shaft 202 has an amplification effect, it is more suitable for scenarios that require large-range adjustment of loading. Therefore, the loading force in the constant stress mode can be precisely adjusted in a small range by the position of the balance weight 8.

[0067] In one embodiment, a pressure sensor 9 is provided on the force-applying rod 4 for detecting the applied force, and a displacement sensor 10 for detecting the compression of the test specimen 12 is also included. In a specific embodiment, the displacement sensor 10 includes a movable piece 1001 disposed on the force-applying rod 4 and a detection part 1002 disposed on the bracket 1. The detection part 1002 detects the displacement of the force-applying rod 4 through the movable piece 1001, thereby reflecting the compression of the test specimen 12.

[0068] The present invention also provides a constant stress mechanical compression creep test method for specimens, using the above-mentioned mechanical compression creep test device, comprising the following steps:

[0069] S1. Adjust the four support screws on the base plate 102 and use the bubble level to level the test device;

[0070] S2. Adjust the position of the balance weight 8 on the balance bar 7 so that the weight of the sector arm 3 is balanced and the pressure acting on the force-applying rod 4 is zero.

[0071] S3. Based on the stress requirements applied to the specimen 12, estimate the weight of the weight 11 that needs to be added to the weight mounting plate 5, and precisely adjust the distance between the rotating shaft 202 and the force-applying rod 4 through the rotating shaft adjustment assembly 2 to obtain the required loading force of the force-applying rod 4.

[0072] The distance adjustment model between the rotating shaft 202 and the force-applying rod 4 is as follows:

[0073]

[0074] In the formula, L is the distance between the rotating shaft 202 and the contact point of the force-applying rod 4, G is the weight of the weight 11 and the weight mounting plate 5, L0 is the distance from the tangent point of the connecting rope 6 and the fan-shaped arm 3 to the axis of the rotating shaft 202, and F is the loading force applied to the force-applying rod 4, which is determined by the following formula:

[0075] F = σ 试 A

[0076] σ 试 Let A be the creep stress of the compression specimen 12, and let A be the cross-sectional area of ​​the specimen 12.

[0077] S4. Install the specimen 12 onto the bracket 1, so that the lower end of the force-applying rod 4 abuts against the specimen 12;

[0078] S5. Displacement sensor 10 continuously detects the vertical displacement of the applied pressure rod 4 and adjusts the position of the rotating shaft 202 according to the constant stress rotating shaft adjustment model to change the loading force value and ensure the constant stress of specimen 12. Considering the Poisson effect, when the compressive creep strain of specimen 12 is large, the effect of the increase in the cross section of specimen 12 on the stress in specimen 12 cannot be ignored. At this time, if the external load remains unchanged, the stress in specimen 12 will decrease. In order to ensure the condition of constant stress creep, it is necessary to adjust the magnitude of the external load in the experiment. When electric control is adopted, it can be adjusted in time by program control. If manual adjustment is adopted, it is necessary to adjust after the strain change reaches a certain level. The adjustment at this time is step adjustment.

[0079] The constant stress rotating shaft adjustment model is as follows:

[0080]

[0081] In the formula, ΔL represents the displacement that the shaft needs to be adjusted, h0 represents the initial height of the specimen, and Δh represents the creep change calculated based on the displacement h displayed by the displacement sensor.

[0082] This method can keep the stress on specimen 12 constant, thus providing a basis for accurate constant stress creep research on specimen 12.

[0083] In step S1, the balance weight 8 is adjusted to a suitable position to maintain balance with the sector arm 3 without the weight 11, so as to avoid putting pressure on the specimen 12.

[0084] The specific working principle of this invention:

[0085] like Figure 5As shown, during the rotation of the sector arm 3, the fulcrum is fixed, the effort arm L0 remains constant and is equal to the radius R of the sector arm 3; since the position of the force-applying lever 4 is fixed, the resistance arm L also remains constant. Based on the lever principle, the experimental loading force value is:

[0086]

[0087] Where G is the weight of weight 12 plus weight mounting plate 5, and L = R.

[0088] like Figure 6 As shown, the power arm L0 remains constant, equal to the radius R of the sector arm; the position of the force-applying lever 4 is fixed. The fulcrum position of the sector arm 3, under the control of the rotating shaft adjustment assembly 2, can be adjusted. That is, the sector arm 3 can move back and forth, changing the fulcrum position accordingly, and the length of the resistance arm becomes L'. Based on the lever principle, the experimental applied force becomes:

[0089]

[0090] At this time, by adjusting the rotating shaft adjustment component 2, the fulcrum of the fan-shaped arm 3 is changed, and the feedback force value of the pressure sensor 9 is used to continuously and controllably adjust the loading force precisely.

[0091] like Figure 7 As shown, in the embodiment with the balancing weight 8, a balance bar 7 and the balancing weight 8 are provided at the front end of the sector arm 3, which can be used to balance the weight of the sector arm 3. The weight of the sector arm is G3, the weight of the balancing weight is G4, the power arm controlled by the weight of the sector arm 3 is L3, and the resistance arm controlled by the balancing weight is L4. Based on the lever principle, the equilibrium formula before rotation can be obtained as follows:

[0092] L3G3 = L4G4

[0093] The equilibrium state after rotation is as follows Figure 7 As shown, the torque relative to the axis of rotation on the left is G4L4cosα, and the torque relative to the axis of rotation on the right after rotation is G3L3cosα. It can be seen that the torques on the left and right sides are still equal after rotation. Therefore, rotation does not change the balance relationship between the left and right sides. That is, as long as the weight of the sector arm is balanced by the balance weight on the left side, its influence can be ignored in the whole experiment.

[0094] Regarding the change in the cross-sectional area of ​​specimen 12 during the experiment:

[0095] Taking specimen 12 as an example of a propellant compression specimen, specimen 12 is a cuboid with dimensions a×a×h0. The Poisson's ratio μ of the propellant material is generally close to 0.5, making it a material with incompressible volume.

[0096] The formula relating test stress and applied force is as follows:

[0097]

[0098] Among them, A=a 2 .

[0099] As the test force is applied, the cross-sectional area of ​​specimen 12 will change. To maintain a constant test stress, the loading force needs to be adjusted in real time (as the cross-section of specimen 12 increases, the corresponding loading force also needs to increase to keep the test stress constant). During the test, the longitudinal strain of the specimen is:

[0100]

[0101] Where Δh is the change in height of specimen 12, and h0 is the initial height of specimen 12.

[0102] Since propellant materials are incompressible, according to the principle of constant volume:

[0103] V = A·h0 = A'·h'

[0104] Where h'=h0(1-ε z Therefore, the change in cross-sectional area of ​​specimen 12 is:

[0105]

[0106] Therefore, if the test stress remains constant, the applied force value should be adjusted as follows:

[0107]

[0108] During the loading process, the distance between the sector arm weight 11 and the rotating shaft 202 remains constant at L0. Based on the lever balance principle and the stress required to be generated in the specimen 12 during the test, the distance from the contact point between the force-applying rod 4 and the sector arm 3 to the rotating shaft 202 can be obtained.

[0109]

[0110] After specimen 12 is compressed, its cross-sectional area changes from the initial A to A'. In order to maintain the stress σ in the specimen... 试 The value remains unchanged. At this point, the loading force acting on the applying pressure bar 4 needs to be increased to achieve the value of the following formula.

[0111] F'=σ 试 A′

[0112] If the force is applied to the pressure rod 4 by adjusting the position of the rotating shaft 202, the length of the lever arm of the loading rod needs to be changed. The force-to-length ratio after the change is given by Equation 1:

[0113]

[0114] At this time, the distance that the rotating shaft 202 adjusts on the slide rail is given by Equation 2:

[0115]

[0116] At this point, the rotating shaft 202 needs to be moved horizontally to the right. This reduces the resistance arm and increases the applied force, thus ensuring that the internal stress of the specimen 12 remains at σ even after the cross-sectional area increases. 试 constant.

[0117] The displacement change Δh fed back by displacement sensor 10 is used to calculate the distance from rotating shaft 202 to the force-applying pressure rod 4 using Equation 1, or the distance rotating shaft 202 needs to move to the right using Equation 2, thus ensuring the constant test stress. During the test, if the position of rotating shaft 202 is adjusted electrically, it can be automatically adjusted via program control. If manual adjustment is used, adjustment is required only after Δh changes to a certain extent; this adjustment is a step-by-step adjustment.

[0118] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

Claims

1. A mechanical compression creep testing device, characterized in that, It includes a bracket (1), a rotating shaft adjustment assembly (2), a fan-shaped arm (3), a force-applying rod (4), and a weight mounting plate (5); The rotating shaft adjustment assembly (2) includes a guide rail assembly (201) mounted on the bracket (1), a rotating shaft (202) mounted on the guide rail assembly (201), and an adjustment drive (203) that drives the rotating shaft (202) to move linearly along the guide rail assembly (201). The central end of the fan-shaped arm (3) is hinged to the rotating shaft (202), and a connecting rope (6) is vertically arranged on the arc side of the fan-shaped arm (3). The other end of the connecting rope (6) is connected to the weight mounting plate (5). The force-applying rod (4) is slidably mounted on the support (1), and the sliding direction of the force-applying rod (4) is vertical. The lower edge of the fan-shaped arm (3) slides against the upper end of the force-applying rod (4), and the lower end of the force-applying rod (4) acts on the specimen (12). The fan-shaped arm (3) is also provided with a balance bar (7) at the end away from the weight mounting plate (5), and a balance weight (8) is slidably mounted on the balance bar (7).

2. The mechanical compression creep testing device as described in claim 1, characterized in that, The upper end of the force-applying rod (4) is provided with a roller (401), and the roller (401) rolls in cooperation with the lower edge of the fan-shaped arm (3).

3. The mechanical compression creep testing device as described in claim 2, characterized in that, The lower edge of the fan-shaped arm (3) is provided with a guide groove (301), and the roller (401) is rolled in the guide groove (301).

4. The mechanical compression creep testing device as described in claim 1, characterized in that, A groove (302) is provided on the arc-shaped side of the fan-shaped arm (3), and the connecting rope (6) is provided in the groove (302).

5. The mechanical compression creep testing device as described in claim 1, characterized in that, The guide rail assembly (201) includes two parallel guide rails (2011) and a slider (2012) slidably disposed on the two guide rails. The rotating shaft (202) is rotatably or fixedly disposed on the two sliders (2012). The adjustment drive (203) includes a lead screw (2031) rotatably disposed on the bracket (1) and a nut (2032) cooperating with the lead screw (2031). The nut (2032) is connected to the rotating shaft (202).

6. The mechanical compression creep testing device as described in claim 1, characterized in that, The support (1) includes a top plate (101) and a bottom plate (102) arranged opposite to each other. The top plate (101) and the bottom plate (102) are connected to each other by a number of guide columns (103). The rotating shaft adjustment assembly (2) and the fan-shaped arm (3) are arranged on the top plate (101). The force-applying pressure rod (4) is vertically inserted on the top plate (101). A specimen receiving space (104) is formed between the top plate (101) and the bottom plate (102).

7. The mechanical compression creep testing device as described in claim 6, characterized in that, The support (1) also includes a side plate, which encloses the specimen receiving space (104) to form a box space, and also includes a temperature regulating component disposed in the box space.

8. The mechanical compression creep testing device as described in claim 7, characterized in that, The pressure sensor (9) for detecting the pressure of the test piece is provided on the force-applying rod (4), and a displacement sensor (10) for detecting the compression of the test piece (12) is also included.

9. A constant stress mechanical compression creep test method for specimens, characterized in that, Using the mechanical compression creep testing apparatus as described in claim 8 includes the following steps: S1. Adjust the support (1) to level the test device; S2. Adjust the position of the balance weight (8) on the balance bar (7) so that the weight of the sector arm (3) is balanced and the pressure acting on the force-applying bar (4) is zero. S3. Based on the stress requirements applied to the specimen (12), estimate the weight of the weight (11) to be added to the weight mounting plate (5), and precisely adjust the distance between the rotating shaft (202) and the force-applying rod (4) through the rotating shaft adjustment assembly (2) to obtain the required loading force of the force-applying rod (4); The distance adjustment model between the rotating shaft (202) and the force-applying rod (4) is as follows: In the formula L The distance between the rotating shaft (202) and the contact point of the force-applying rod (4) is... G The weights of the weights (11) and the weight mounting plate (5) are: L 0 is the distance from the point of tangency between the connecting rope (6) and the fan-shaped arm (3) to the axis of the rotating shaft (202). F The loading force applied to the compression bar (4) F Determined by the following formula: To compress the creep stress of specimen (12), A The cross-sectional area of ​​specimen (12); S4. Install the specimen (12) onto the bracket (1) so that the lower end of the force-applying rod (4) abuts against the specimen (12). S5. The displacement sensor (10) continuously detects the vertical displacement of the applied pressure rod (4) and adjusts the position of the rotating shaft (202) according to the constant stress rotating shaft adjustment model to change the loading force value and ensure the constant stress of the specimen (12). The constant stress rotating shaft adjustment model is as follows: In the formula, This indicates the amount of displacement that the rotating shaft (202) needs to be adjusted. Indicates the initial height of specimen (12), This indicates the displacement displayed by the displacement sensor. The amount of creep change obtained by calculation.

Images