A propellant grain residual bias stress in-situ measurement device, system and method

Abstract

The present application belongs to the field of propellant grain residual bias stress measurement, and particularly relates to a propellant grain residual bias stress in-situ measurement device, system and method. The propellant grain residual bias stress in-situ measurement device comprises a support structure, a prefabricated grain block and a sensor. The sensor comprises a strain sensor embedded in the prefabricated grain block, and the prefabricated grain block is arranged on the support structure. The propellant grain residual bias stress in-situ measurement device is arranged in the engine charge combustion chamber through the support structure before casting the engine grain, and is used for monitoring the residual bias stress of the engine grain in the solidification-cooling process in-situ and on-line after casting the engine grain. The prefabricated grain block with the sensor is pre-installed, and the evolution of the residual bias stress of the large solid rocket engine casting grain in the whole solidification-cooling process is realized, and high-fidelity and real-time on-line monitoring is realized.

Description

Technical Field

[0001] This invention belongs to the field of residual deviatoric stress measurement of propellant grains, and specifically relates to an in-situ measurement device, system and method for residual deviatoric stress of propellant grains. Background Technology

[0002] With the rapid development of the aerospace launch vehicle field, solid rocket motors are also rapidly evolving towards higher fill fractions, higher operating pressures, and longer storage periods, leading to increasingly severe challenges in structural integrity. Pressurized curing technology is widely used as it is considered effective in eliminating residual stress in the propellant grains during the cooling process. However, current solid rocket motor curing-cooling processes are often designed based on experience and simple calculations, resulting in unclear residual stress control mechanisms and limited control methods.

[0003] Solid rocket motors possess a multi-interface structure consisting of a shell-insulation layer, an insulation layer-liner, and a liner-propellant grain. Simultaneously, the propellant grain exhibits complex geometry, extreme thickness, and a very high content of solid particles, all of which pose significant challenges to the application of residual stress monitoring technologies based on acoustic emission and radiation principles. Furthermore, solid rocket motors require vacuum-assisted casting and vacuum degassing processes before solidification and cooling to reduce the porosity of the solidified material. These processes often involve intense propellant slurry flow, posing a significant challenge to sensor placement. Sensor placement in solid rocket motors is often limited to interfaces or small internal components such as tensioned optical fibers and thermocouples, making it impossible to measure the evolution of residual stress and strain within the propellant grain. Common destructive testing methods, such as drilling and layer removal, are only applicable to solidified propellant grains, and their measurement depth is often limited, while also carrying significant operational risks.

[0004] The solidification-cooling process involves the transformation of the propellant from a viscous fluid to a viscoelastic solid, which is highly nonlinear. Numerical simulation analysis often relies on numerous assumptions to obtain convergence results, and the reliability of the results also lacks effective experimental data verification.

[0005] Therefore, research on the generation mechanism and optimal control of residual stress in materials during the solidification-cooling process of solid rocket engines is limited by experimental methods and is still in its early stages. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an in-situ measurement device, system and method for residual deviatoric stress of propellant grains that is suitable for accurate measurement of residual deviatoric stress and is easy to assemble.

[0007] The present invention provides an in-situ measurement device for residual deviatoric stress of propellant grains, comprising a support structure, a pre-made propellant block, and a sensor for monitoring the mechanical strain of the pre-made propellant block; The sensors include strain sensors and temperature sensors embedded in pre-made drug blocks, which are mounted on a support structure. The in-situ measurement device for residual deviatoric stress of propellant grains is used to be installed in the combustion chamber of the engine before the propellant grains are poured, and to perform in-situ online monitoring of residual deviatoric stress of the propellant grains during the curing-cooling process after the propellant grains are poured.

[0008] Temperature sensors are used to acquire temperature changes during the solidification-cooling process of engine propellant grains and to calculate thermal strain based on these temperature changes. When monitoring the residual deviatoric stress in situ during the curing-cooling process of engine propellant grains, thermal strain is eliminated, and only mechanical strain results are retained.

[0009] Furthermore, the strain sensor includes radial strain gauges and axial strain gauges.

[0010] Furthermore, the support structure includes a vertically connected sidewall connection and a vertically extending portion; The side wall connecting part is used to fix it to the inner wall of the engine propellant combustion chamber, and the vertical extension part extends into the engine propellant combustion chamber; The pre-made drug block is covered with a vertically extending part.

[0011] Furthermore, the sensor cable is fixed sequentially to the vertical extension part and the side wall connection part, and is led out of the engine combustion chamber through the top of the side wall connection part.

[0012] Furthermore, it also includes a pressure-resistant sealing joint installed on the engine's propellant combustion chamber; The sensor cable is connected to a pressure-resistant sealed connector via a quick-connect plug.

[0013] Furthermore, it also includes a data receiver and data processing device that are installed outside the engine's combustion chamber and connected to the sensor via cables.

[0014] The present invention also provides an in-situ measurement system for residual deviatoric stress of propellant grains, comprising an engine propellant combustion chamber, an engine propellant grain disposed within the engine propellant combustion chamber, and at least one set of the aforementioned in-situ measurement devices for residual deviatoric stress of propellant grains.

[0015] The present invention also provides a method for in-situ measurement of residual deviatoric stress in propellant grains, comprising the following steps: S1, Processing and calibrating the in-situ measurement device for residual deviatoric stress of propellant grains: Pre-made blocks are placed on the support structure, and sensors are embedded in the pre-made blocks, including strain sensors. The sensor is calibrated; S2, Install the in-situ measuring device for residual deviatoric stress of propellant grain in the engine propellant combustion chamber, and lead the sensor out of the engine propellant combustion chamber; S3, pouring propellant slurry into the engine's combustion chamber to form an engine propellant column; S4 continuously acquires sensor data during the solidification-cooling process of the engine propellant grain, and monitors the residual deviatoric stress inside the propellant grain in situ online through the residual deviatoric stress calculation model. The residual deviatoric stress is obtained using the following residual deviatoric stress calculation model:

[0016] in, It is a deviatoric stress; For the time to be accumulated, The shear relaxation modulus of the material can be pre-calibrated by relaxation experiments.

[0017] In step S4, the combined effect of temperature and internal stress in the propellant grain will cause the in-situ measuring device for residual deviatoric stress in the propellant grain to deform. The deformation is divided into two parts: mechanical strain and thermal strain. In step S4, based on the thermal expansion coefficient test of the pre-made block and the temperature feedback results from the temperature sensor, the thermal strain of the pre-made block is eliminated, and only the mechanical strain of the pre-made block is retained. Based on the fact that the Poisson's ratio of both the pre-made propellant block and the engine propellant grain is greater than 0.495, the mechanical strain result of the retained pre-made propellant block is determined to be the pre-made propellant block deviatoric strain result. Based on the stiffness mismatch between the pre-propellant block (2) and the engine propellant grain (5), the deformation of the pre-propellant block (2) in the in-situ measurement device for residual deviatoric stress of the propellant grain is caused by the internal stress of the engine propellant grain (5). Combining the force balance and the measurement of the shear relaxation modulus of the pre-propellant block (2), the residual deviatoric stress inside the propellant grain is monitored in situ online through the residual deviatoric stress calculation model.

[0018] The beneficial effects of this invention are that the in-situ measurement device for residual deviatoric stress in propellant grains utilizes the characteristic that the material properties of the pre-made propellant block are consistent with the material properties of the engine propellant grains to be cast, as well as the characteristic that the pre-made propellant block has a Poisson's ratio greater than 0.495 (approximately incompressible property). By detecting mechanical strain through sensors and measuring the shear relaxation modulus of the pre-made propellant block, the device performs in-situ online monitoring of residual deviatoric stress inside the propellant grain through a residual deviatoric stress calculation model.

[0019] Specifically, based on the stiffness mismatch between the prefabricated structure and the engine propellant grain, the deformation of the prefabricated block in the in-situ measurement device for residual deviatoric stress of the propellant grain is caused by the internal stress of the engine propellant grain. The deformation of the prefabricated block under the internal stress of the engine propellant grain is obtained by compensating for the thermal strain in the prefabricated block using a temperature sensor. Based on the characteristic that the prefabricated block has a Poisson's ratio greater than 0.495 (approximately incompressible), its deformation is not affected by volumetric stress and is only related to the deviatoric stress. Combining force balance and the measurement of the shear relaxation modulus of the prefabricated block, the residual deviatoric stress inside the engine propellant grain is monitored in-situ online using a residual deviatoric stress calculation model. After monitoring, the prefabricated block can also be used as an engine propellant grain when needed.

[0020] By using pre-installed sensor-equipped propellant blocks, combining the compatibility and Poisson's ratio characteristics of similar materials between the pre-installed propellant blocks and engine propellant grains, and employing an in-situ installation method, this method achieves high-fidelity, real-time online monitoring of the evolution of residual deviatoric stress throughout the curing-cooling process of large solid rocket motor propellant grains in a real working environment. This approach is simple in structure, easy to manufacture, convenient to operate, and widely applicable. It solves the problem of lacking propellant grain test data during the curing-cooling process, greatly improves data reliability and guidance value for optimizing actual processes, and is of great significance for ensuring engine performance and safety.

[0021] In addition, the in-situ measurement device for residual deviatoric stress in the propellant grain has minimal impact on the original internal residual deviatoric stress distribution of the engine propellant grain, thus ensuring measurement accuracy. Attached Figure Description

[0022] Appendix Figure 1 This is a schematic diagram of the in-situ measurement device for residual deviatoric stress of propellant grains in this invention; Appendix Figure 2 This is a schematic diagram of the in-situ measurement system for residual deviatoric stress of propellant grains in this invention; Appendix Figure 3 This is a stress distribution diagram when no in-situ measurement device for residual deviatoric stress of the propellant grain is installed in the propellant grain of this engine. Appendix Figure 4 This is a stress distribution diagram when an in-situ measurement device for residual deviatoric stress of the propellant grain is installed in the propellant grain of this engine.

[0023] In the figure, 1-support structure; 11-side wall connection; 12-vertical extension; 2-pre-made block; 3-strain sensor; 31-radial strain gauge; 32-axial strain gauge; 33-cable; 4-temperature sensor; 5-engine propellant; 6-engine propellant combustion chamber; 61-combustion chamber end cap; 62-mold core; 7-pressure resistant sealing joint; 8-quick connector; 9-data receiver; 10-data processing device. Detailed Implementation

[0024] 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] like Figures 1-4 As shown, the present invention provides an in-situ measurement device for residual deviatoric stress of propellant grain, including a support structure 1, a pre-made propellant block 2, and a sensor for monitoring the mechanical strain of the pre-made propellant block 2. The support structure 1 is used to support the pre-made propellant block 2 and to install the in-situ measurement device for residual deviatoric stress of propellant grain into the combustion chamber 6 of the engine. The material properties of the pre-made propellant block 2 are consistent with the material properties of the engine propellant grain 5, and it serves as the carrier of the sensor. The sensors include a strain sensor 3 and a temperature sensor 4 embedded in the pre-made block 2. The sensors are used to detect the mechanical strain of the pre-made block 2, which is mounted on the support structure 1. The in-situ measurement device for residual deviatoric stress of propellant grain is installed in the combustion chamber 6 of the engine before the engine propellant grain 5 is poured, through the support structure 1. After the engine propellant grain 5 is poured, the engine propellant grain 5 is fused with the pre-made block 2. At this time, the in-situ measurement device for residual deviatoric stress of propellant grain performs in-situ online monitoring of residual deviatoric stress of engine propellant grain 5 during the curing-cooling process.

[0030] The in-situ measurement device for residual deviatoric stress in propellant grains of the present invention utilizes the material properties of the pre-made block 2 being consistent with those of the final engine propellant grain 5 to be cast (material compatibility), and the characteristic that the pre-made block 2 has a Poisson's ratio greater than 0.495 (approximately incompressible property). By detecting the mechanical strain of the pre-made block 2 through sensors and measuring the shear relaxation modulus of the pre-made block 2, the device performs in-situ online monitoring of the residual deviatoric stress inside the propellant grain through a residual deviatoric stress calculation model.

[0031] Specifically, based on the stiffness mismatch between the prefabricated structure and the engine propellant grain 5, the deformation of the prefabricated block 2 in the in-situ measurement device for residual deviatoric stress of the propellant grain is caused by the internal stress of the engine propellant grain 5. The thermal strain in the prefabricated block 2 is compensated by the temperature sensor 4 to obtain the deformation result of the prefabricated block 2 under the action of the internal stress of the engine propellant grain 5. Based on the characteristic that the Poisson's ratio of the prefabricated block 2 is greater than 0.495 (approximately incompressible), its deformation result is not affected by volumetric stress, but only by the action of deviatoric stress. Combining force balance and the measurement of the shear relaxation modulus of the prefabricated block 2, the residual deviatoric stress inside the engine propellant grain 5 is monitored in-situ online using a residual deviatoric stress calculation model. After the monitoring is completed, when the engine propellant grain 5 needs to be used, the prefabricated block 2 can also be used as the engine propellant grain 5.

[0032] By using a pre-installed sensor-equipped pre-powder block 2, and combining the similar material compatibility and Poisson's ratio characteristics of the pre-powder block 2 and the engine propellant grain 5, as well as the in-situ installation method, a high-fidelity, real-time online monitoring of the evolution of residual deviatoric stress during the entire curing-cooling process of large solid rocket motor propellant grains in a real working environment was achieved. This method is simple in structure, easy to manufacture, convenient to operate, and has a wide range of applications. It solves the problem of lacking propellant grain test data during the curing-cooling process, greatly improves the reliability of the data and its guiding value for optimizing actual processes, and is of great significance for ensuring engine performance and safety.

[0033] Additionally, refer to Figure 3 and Figure 4The in-situ measurement device for residual deviatoric stress in the propellant grain has minimal impact on the original distribution of residual deviatoric stress inside the engine propellant grain 5, thus ensuring measurement accuracy.

[0034] Temperature sensor 4 is used to acquire the temperature change during the curing-cooling process of the engine propellant 5, and to calculate the thermal strain based on the temperature change; When monitoring the residual deviatoric stress in situ during the curing-cooling process of the engine propellant grain 5, the thermal strain is eliminated, and only the mechanical strain results are retained.

[0035] When the propellant grain 5 is poured into the combustion chamber 6 of the engine, the combined effect of the temperature of the pre-made block 2 and the internal stress of the propellant grain 5 causes the pre-made block 2 to deform. This deformation consists of two parts: mechanical strain and thermal strain. In this embodiment, by setting a temperature sensor 4, based on the thermal expansion coefficient test of the pre-made block 2 and the temperature feedback result from the temperature sensor 4, the thermal strain of the pre-made block 2 can be eliminated, retaining only the mechanical strain result. This fully considers the exothermic reaction of curing and the instability of the ambient temperature, effectively eliminating measurement errors, and is more suitable for situations with large masses of thermosetting materials, such as solid rocket engines.

[0036] During the solidification and cooling process of the engine propellant grain 5, a complex residual stress distribution is generated inside the propellant grain due to material shrinkage, complex geometry, and complex constraints imposed by the external structure and mandrel (especially by the engine combustion chamber 6). In one embodiment, the strain sensor 3 includes a radial strain gauge 31 and an axial strain gauge 32. By combining the radial strain gauge 31 and the axial strain gauge 32, the residual Mises stress within the pre-propellant block 2 can be measured, providing a comprehensive description of the stress state and improving monitoring accuracy.

[0037] In one embodiment, the support structure 1 includes a vertically connected sidewall connection portion 11 and a vertically extended portion 12; The side wall connecting part 11 is used to fix it to the inner wall of the engine propellant combustion chamber 6, and the vertical extension part 12 extends into the engine propellant combustion chamber 6. The pre-made block 2 is provided to cover the vertically extending part 12.

[0038] In this embodiment, the sidewall connecting part 11 and the vertical extension part 12 in the support structure 1 are arranged in an L-shape. This allows the in-situ measuring device for residual deviatoric stress of the propellant grain to be fixed through the sidewall of the engine propellant combustion chamber 6, and also allows the pre-powder block 2 and the sensor to extend into the middle of the engine propellant combustion chamber 6, enabling detection of any target monitoring point of the engine propellant grain 5 and improving monitoring accuracy. The pre-powder block 2 covers the vertical extension part 12, protecting the sensor lead from the violent flow of the slurry during the casting and vacuum degassing processes. Consequently, during sensor manufacturing, a finer diameter wire can be used, reducing the impact of sensor installation on the engine interface adhesion performance and avoiding serious impact on the engine structural integrity.

[0039] refer to Figure 3 and Figure 4 The specific structure of this support structure 1 has minimal impact on the original internal residual deviatoric stress distribution of the engine propellant grain 5, thus ensuring measurement accuracy.

[0040] In one embodiment, the sensor cable 33 is sequentially fixed to the vertical extension portion 12 and the side wall connection portion 11, and leads out of the engine propellant combustion chamber 6 through the top end of the side wall connection portion 11. This arrangement allows for physical protection of the sensor cable 33 by the support structure 1, improving operational stability.

[0041] In one embodiment, a pressure-resistant sealing joint 7 is also provided on the engine propellant combustion chamber 6; The sensor cable 33 is connected to the pressure-resistant sealing connector 7 via a quick-connect plug 8. The pressure-resistant sealing connector 7 is located on the combustion chamber end cover 61.

[0042] In this embodiment, the sensor is connected to the pressure-resistant sealing connector 7 via a quick-connect plug 8. During the removal of the mold core 62 in the curing fixture, the connector can be quickly separated, protecting the signal line from damage.

[0043] In one embodiment, the in-situ measurement device for residual deviatoric stress of the propellant grain further includes a data receiver 9 and a data processing device 10 connected to the sensor cable 33 and disposed outside the engine propellant combustion chamber 6. The data receiver 9 includes a strain receiver connected to the strain sensor 3 and a temperature receiver connected to the temperature sensor 4. The data processing device 10 can be a computer or similar device.

[0044] The present invention also includes an in-situ measurement system for residual deviatoric stress of propellant grains, comprising an engine propellant combustion chamber 6, an engine propellant grain 5 disposed within the engine propellant combustion chamber 6, and at least one set of the aforementioned in-situ measurement devices for residual deviatoric stress of propellant grains.

[0045] When multiple sets of in-situ measurement devices for residual deviatoric stress in propellant grains are installed, a pressure-resistant sealing joint 7 can be connected via a quick-connect plug 8. The support structure 1, pre-made propellant block 2, and sensors in the multiple sets of in-situ measurement devices for residual deviatoric stress in propellant grains can be set at different depths in the engine combustion chamber 6 to monitor the deviatoric stress at different positions of the engine propellant grain 5.

[0046] The present invention also provides a method for in-situ measurement of residual deviatoric stress in propellant grains, comprising the following steps: S1, Processing and calibrating the in-situ measurement device for residual deviatoric stress of propellant grains: A pre-made drug block 2 is set on the support structure 1, and a sensor is embedded in the pre-made drug block 2, wherein the sensor includes a strain sensor 3 and a temperature sensor 4. The sensor is calibrated; S2, Install the in-situ measuring device for residual deviatoric stress of propellant grain in the engine propellant combustion chamber 6, and lead the sensor out of the engine propellant combustion chamber 6; S3, pouring propellant slurry into the engine combustion chamber 6 to form the engine propellant column 5; S4 continuously acquires sensor data during the curing and cooling process of the engine propellant grain 5, and monitors the residual deviatoric stress inside the propellant grain in situ online through the residual deviatoric stress calculation model.

[0047] The residual deviatoric stress is obtained using the following residual deviatoric stress calculation model: ; in, It is a deviatoric stress; For the time to be accumulated, The shear relaxation modulus of the material can be pre-calibrated by relaxation experiments.

[0048] Since the strain measured by the sensor will continuously change during the curing-cooling process of the engine propellant 5, the shear relaxation modulus of the pre-prepared propellant block 2 will also change dynamically with temperature and load application time. Therefore, by pre-calibrating the shear relaxation modulus of the pre-prepared propellant block 2 and measuring the strain changes measured by the sensor, residual deviatoric stress can be monitored in situ online throughout the curing-cooling process of the engine propellant 5.

[0049] Without a temperature sensor, the large size and complex geometry of solid rocket motor propellant grains, along with the difficulty in accurately predicting the heat transfer process, make it impossible to effectively eliminate temperature strain, leading to significant errors.

[0050] In step S4, the combined effects of temperature and pressure will cause the in-situ measuring device for residual deviatoric stress of the propellant grain to deform, and the deformation is divided into two parts: mechanical strain and thermal strain. In step S4, based on the thermal expansion coefficient test of the pre-made block 2 and the temperature feedback result from the temperature sensor 4, the thermal strain of the pre-made block 2 is eliminated, and only the mechanical strain result of the pre-made block 2 is retained. That is, when temperature sensor 4 is installed, the deviatoric strain It is calculated using the strain data measured by strain sensor 3 and the temperature data measured by temperature sensor 4. Specifically: Since the strain of pre-made block 2 can be divided into two parts: mechanical strain and thermal strain, that is...

[0051] in, For mechanical strain; Thermal strain; The strain of the pre-formed block is acquired by strain sensor 3, including mechanical strain. and thermal strain Based on this, the thermal strain can be calculated by measuring the temperature using temperature sensor 4. Since thermal strain is independent of the stress on the pre-formed block, it needs to be eliminated. Combining the results measured by temperature sensor 4, the method for eliminating thermal strain can be derived. Post-mechanical strain .

[0052] .

[0053] Based on this, mechanical strain can be divided into volumetric strain and deviatoric strain.

[0054] in, For volumetric strain, For partial strain.

[0055] Since the Poisson's ratio of propellant materials is often greater than 0.495, the propellant material can be considered approximately incompressible, and its volumetric strain can be ignored. That is, the measured strain can be approximated as the deviatoric strain of the propellant mass. Considering material compatibility, there is no thermal stress in the engine propellant grain and the propellant mass during the curing-cooling process; stress can be effectively transferred between the propellant grain and the propellant mass. Therefore, .

[0056] This in-situ measurement method for residual deviatoric stress in the propellant grain is based on the fact that the Poisson's ratio of pre-powder block 2 is greater than 0.495, which means that the proportion of lateral shrinkage when pre-powder block 2 is subjected to longitudinal tension is significant. The closer the Poisson's ratio is to 0.5, the closer the material is to being "volume incompressible." At this point, the mechanical strain result of the retained pre-powder block 2 can be determined as the deviatoric strain result of the pre-powder block. Since the pre-powder block 2 and the engine propellant grain 5 are made of the same material, there is no thermal stress or interface problem during the curing-cooling process. Therefore, the stress can be effectively transferred between the two. It is assumed that the deviatoric stress at the measuring point of the engine propellant grain is the result of the deviatoric stress on the pre-powder block.

[0057] In this embodiment, based on the stiffness mismatch between the prefabricated structure and the engine propellant grain 5, the deformation of the prefabricated block 2 in the in-situ measurement device for residual deviatoric stress of the propellant grain is caused by the internal stress of the engine propellant grain 5. The thermal strain in the prefabricated block 2 is compensated by the temperature sensor 4 to obtain the deformation result of the prefabricated block 2 under the action of the internal stress of the engine propellant grain 5. Based on the characteristic that the Poisson's ratio of the prefabricated block 2 is greater than 0.495 (approximately incompressible), its deformation result is not affected by volumetric stress, but only by the action of deviatoric stress. Combining the force balance and the measurement of the shear relaxation modulus of the prefabricated block 2, the residual deviatoric stress inside the engine propellant grain 5 is monitored in-situ online using a residual deviatoric stress calculation model.

[0058] The above description is merely an embodiment and does not constitute any limitation on the present invention. Any person skilled in the art can make many possible variations, modifications, or alterations to the technical solutions of the present invention without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the present invention, should fall within the protection scope of the present invention.

Claims

1. An in-situ measuring device for residual deviatoric stress in propellant grains, characterized in that, It includes a support structure (1), a pre-made block (2), and sensors for monitoring the mechanical strain of the pre-made block (2); The sensor is embedded in the pre-made drug block (2), and the pre-made drug block (2) is set on the support structure (1); The in-situ measurement device for residual deviatoric stress of propellant grain is used to be installed in the combustion chamber (6) of the engine before the engine propellant grain (5) is poured through the support structure (1), and to monitor the residual deviatoric stress of the engine propellant grain (5) in situ during the curing-cooling process after the engine propellant grain (5) is poured.

2. The in-situ measurement device for residual deviatoric stress of propellant grains as described in claim 1, characterized in that, The sensors include a strain sensor (3) and a temperature sensor (4). Temperature sensor (4) is used to acquire the temperature change during the curing-cooling process of the engine propellant (5) and to calculate the thermal strain based on the temperature change; When monitoring the residual deviatoric stress in situ during the curing-cooling process of the engine propellant grain (5), the thermal strain is eliminated and only the mechanical strain result is retained.

3. The in-situ measurement device for residual deviatoric stress of propellant grains as described in claim 2, characterized in that, The strain sensor (3) includes a radial strain gauge (31) and an axial strain gauge (32).

4. The in-situ measuring device for residual deviatoric stress of propellant grains as described in any one of claims 1-3, characterized in that, The support structure (1) includes a vertically connected side wall connection (11) and a vertically extended part (12). The side wall connecting part (11) is used to fix to the inner wall of the engine charging combustion chamber (6), and the vertical extension part (12) extends into the engine charging combustion chamber (6); The pre-made block (2) is provided to cover the vertically extending part (12).

5. The in-situ measurement device for residual deviatoric stress of propellant grains as described in claim 4, characterized in that, The sensor cable (33) is fixed in sequence to the vertical extension part (12) and the side wall connection part (11), and is led out of the engine charge combustion chamber (6) through the top of the side wall connection part (11).

6. The in-situ measurement device for residual deviatoric stress of propellant grains as described in claim 5, characterized in that, It also includes a pressure-resistant sealing joint (7) installed on the engine propellant combustion chamber (6); The sensor cable (33) is connected to the pressure-resistant sealed connector (7) via a quick-connect plug (8).

7. The in-situ measurement device for residual deviatoric stress of propellant grains as described in claim 6, characterized in that, It also includes a data receiver (9) and a data processing device (10) located outside the engine combustion chamber (6) and connected to the sensor via a cable (33).

8. An in-situ measurement system for residual deviatoric stress in propellant grains, characterized in that, It includes an engine propellant combustion chamber (6), an engine propellant grain (5) disposed in the engine propellant combustion chamber (6), and at least one set of in-situ measuring devices for residual deviatoric stress of the propellant grain as described in any one of claims 1-7.

9. A method for in-situ measurement of residual deviatoric stress in propellant grains, characterized in that, Includes the following steps: S1, Processing and calibrating the in-situ measurement device for residual deviatoric stress of propellant grains: A pre-made drug block (2) is set on the support structure (1), and a sensor is pre-embedded on the pre-made drug block (2), wherein the sensor includes a strain sensor (3) and a temperature sensor (4). The sensor is calibrated; S2, the in-situ measuring device for residual deviatoric stress of propellant grain is installed in the engine propellant combustion chamber (6), and the sensor leads are led out of the engine propellant combustion chamber (6). S3, pour propellant slurry into the engine combustion chamber (6) to form an engine propellant column (5); S4, during the solidification-cooling process of the engine propellant (5), the sensor continuously acquires the sensing data, and the residual deviatoric stress inside the propellant is monitored in situ online through the residual deviatoric stress calculation model; The residual deviatoric stress is obtained using the following residual deviatoric stress calculation model: in, It is a deviatoric stress; For the time to be accumulated, The shear relaxation modulus of the material can be pre-calibrated by relaxation experiments.

10. The method for in-situ measurement of residual deviatoric stress in propellant grains as described in claim 9, characterized in that, In step S4, the combined effect of temperature and internal stress in the engine propellant (5) will cause the in-situ online monitoring device for residual deviatoric stress after solidification and cooling of the propellant block to deform. The deformation is divided into mechanical strain and thermal strain. In step S4, based on the thermal expansion coefficient test of the pre-made block (2) and the temperature feedback result of the temperature sensor (4), the thermal strain of the pre-made block (2) is eliminated, and only the mechanical strain result of the pre-made block (2) is retained; Based on the fact that the Poisson's ratio of both the pre-made block (2) and the engine propellant column (5) is greater than 0.495, the mechanical strain result of the retained pre-made block (2) is determined to be the pre-made block deviatoric strain result. Based on the stiffness mismatch between the pre-propellant block (2) and the engine propellant grain (5), the deformation of the pre-propellant block (2) in the in-situ measurement device for residual deviatoric stress of the propellant grain is caused by the internal stress of the engine propellant grain (5). Combining the force balance and the measurement of the shear relaxation modulus of the pre-propellant block (2), the residual deviatoric stress inside the propellant grain is monitored in situ online through the residual deviatoric stress calculation model.

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