A solid rocket engine case interface stress monitoring system and method

Abstract

This application provides a system and method for monitoring interface stress in a solid rocket motor casing. The system includes: a signal input module, an inductive flexible interface stress sensor, a signal output module, a signal excitation module, a signal processing module, and a host PC. The inductive flexible interface stress sensor includes: an inductive flexible substrate, and signal transmitting induction coils and signal receiving induction coils positioned on the upper and lower surfaces of the inductive flexible substrate. Each signal transmitting and receiving induction coil includes: an induction coil and inductive flexible covering layers disposed on the upper and lower surfaces of the induction coil. Two induction interface terminals are provided on the induction coil. The induction coil is wound in a planar helical structure with full turns. This application achieves high-speed and stable monitoring of the bonding interface stress without damaging the solid rocket motor casing.

Description

Technical Field

[0001] This application relates to the field of solid rocket motor monitoring technology, specifically to a solid rocket motor casing interface stress monitoring system and method. Background Technology

[0002] Throughout their entire lifecycle—from production and storage to transportation and launch—solid rocket engines are subjected to complex mechanical and thermal loads, including long-term static gravity, transportation vibrations, and changes in ambient temperature. Under these complex force and thermal loads, the propellant grain undergoes varying degrees of deformation, leading to internal cracking or interfacial debonding. Most solid rocket engines employ a wall-mounted propellant loading method, resulting in a multi-interface bonded structure within the combustion chamber, consisting of the shell, insulation layer, liner, and propellant. The bonding interfaces of the liner are the weakest point in the solid rocket engine structure; nearly one-third of solid rocket engine failures abroad are due to interfacial debonding.

[0003] Patent document CN201720256866.8 discloses a device for monitoring the load-bearing state of the bonding interface of a solid rocket motor. This device utilizes a stress-temperature sensor to measure the normal stress and temperature at the bonding interface of the straight section of the solid rocket motor. The device includes a stress-temperature sensor installed on the inner wall of the solid rocket motor, a stress transmitter installed on the outside of the solid rocket motor and connected to the stress-temperature sensor via leads, a data acquisition system connected to the stress transmitter, and an excitation power supply. The sensor employs a flat-film cylindrical cavity structure, and the leads are insulated flat connecting wires. The sensor is implanted in the insulation layer by drilling blind holes in the insulation layer.

[0004] Patent document CN111999176A discloses a non-destructive monitoring and measurement device and method for stress in buried pipelines. Based on the magnetoelastic effect principle of ferromagnetic materials, it utilizes a magnetic flux sensor to perform non-destructive measurement of stress in buried pipelines. While this solution discloses a non-destructive, non-contact monitoring method, existing technologies generally have limitations in application when facing the unique and complex operating conditions of solid rocket engines. Specifically, these limitations manifest in the following two aspects: First, existing non-destructive testing sensors are rigid structures, while solid rocket motor propellant grains and liners have unique low modulus and viscoelastic characteristics, which will produce slight deformation under service loads. If existing rigid sensors are directly placed into narrow bonding interfaces, local stress concentration is very likely to occur due to severe mismatch in mechanical modulus. This will not only lead to serious distortion of stress monitoring data, but may even act as a foreign object to induce or accelerate the debonding failure of the interface.

[0005] Secondly, the structure or principle of the sensors used require a relatively long response time, limiting the application of monitoring devices in situations requiring rapid response. During transport, hoisting, or ignition, the bonding interface of a solid rocket motor often experiences transient impacts and high-frequency vibration loads at extremely high loading rates. Traditional sensors with slow response times are prone to missing the instantaneous peak stress that truly causes interface failure, thus providing erroneous feedback on interface safety and creating catastrophic safety hazards. Therefore, overcoming the physical delay bottleneck of traditional sensors and accurately capturing high-frequency dynamic loads in an extremely short time to achieve high-response interface stress sensing is another major challenge that current technology struggles to overcome.

[0006] In summary, traditional solid rocket motor monitoring methods all require drilling holes at multiple points in the casing to guide wires, which compromises the integrity of the motor structure. Furthermore, non-destructive testing methods from other fields are not suitable for solid rocket motor monitoring. Therefore, how to achieve in-situ, conformal, non-destructive sensing of minute stresses at deep bonding interfaces without damaging the thick casing is a pressing problem that needs to be solved. Summary of the Invention

[0007] The purpose of this application is to address the deficiencies of the existing technology and to provide a solid rocket motor casing interface stress monitoring system and method.

[0008] A solid rocket motor casing interface stress monitoring system, comprising: Signal input module, inductive flexible interface stress sensor, signal output module, signal excitation module, signal processing module, host PC; The output terminal of the signal excitation module is connected to the input terminal of the signal input module via a wire, and the output terminal of the signal input module is connected to the input terminal of the inductive flexible interface stress sensor via a wire; the output terminal of the inductive flexible interface stress sensor is connected to the input terminal of the signal output module via a wire, the output terminal of the signal output module is connected to the input terminal of the signal processing module via a wire, and the output terminal of the signal processing module is connected to the host PC via a wire. The inductive flexible interface stress sensor includes: an inductive flexible substrate, and a signal transmitting induction coil and a signal receiving induction coil located on the upper and lower surfaces of the inductive flexible substrate; the inductive flexible substrate, the signal transmitting induction coil, and the signal receiving induction coil have a centrally symmetrical structure; and the external dimensions of the signal transmitting induction coil, the signal receiving induction coil, and the inductive flexible substrate are matched, and the three are bonded together by silicone sealant. The signal transmitting induction coil and the signal receiving induction coil each include: an induction coil and a flexible induction covering layer disposed on the upper and lower surfaces of the induction coil. Two induction interface terminals are disposed on the induction coil. The induction coil is wound in a planar spiral structure with full turns.

[0009] According to the solid rocket motor casing interface stress monitoring system described above, the inductive flexible cover layer is made of a non-elastic material, which includes any one of polyimide, polyvinyl chloride, and polyethylene terephthalate; the thickness of the inductive flexible cover layer is 2 mm.

[0010] According to the solid rocket motor casing interface stress monitoring system described above, the induction coil has an outer diameter of 2 cm, a wire diameter of 0.1 mm, and a number of turns... Wire diameter and spacing .

[0011] According to the solid rocket motor casing interface stress monitoring system described above, the signal input module and the signal output module each include: a pair of flexible planar coils; each flexible planar coil includes: a signal coil and flexible covering layers disposed on the upper and lower surfaces of the signal coil; and two signal interface terminals are disposed on the signal coil. The signal coil is wound with a planar annular spiral structure, and its center is a hollow design with the number of internal turns removed.

[0012] According to the solid rocket motor casing interface stress monitoring system described above, the ratio of the outer diameter to the inner diameter of the signal coil is 2:1, and its wire diameter is 0.2 mm.

[0013] According to the solid rocket motor casing interface stress monitoring system described above, in the pair of flexible planar coils of the signal input module, one flexible planar coil is placed outside the solid rocket motor casing as the transmitting end, and the other is placed between the liner and the propellant grain as the receiving end. Of the pair of flexible planar coils in the signal output module, one flexible planar coil serves as the transmitting end and is placed between the solid rocket motor liner and the propellant grain, while the other serves as the receiving end and is placed outside the solid rocket motor casing. The pair of flexible planar coils are placed coaxially opposite each other.

[0014] According to the solid rocket motor casing interface stress monitoring system described above, the flexible cover layer is made of a non-elastic material, which includes any one of polyimide, polyvinyl chloride, and polyethylene terephthalate.

[0015] According to the solid rocket motor casing interface stress monitoring system described above, both the induction coil and the signal coil are made of copper. Both the sensing interface terminal and the signal interface terminal adopt the radio frequency IPEX interface.

[0016] According to the solid rocket motor casing interface stress monitoring system described above, the inductive flexible substrate is made of 10:1 polydimethylsiloxane material, that is, the mass ratio of polydimethylsiloxane to the matching curing agent is 10:1.

[0017] This application also provides a monitoring method for the solid rocket motor casing interface stress monitoring system as described above, including: Under the initial state of no interfacial stress, obtain the initial reference voltage of the system. , ;in, The inductance coefficient of the signal input module. This represents the sensing coefficient of an inductive flexible interface stress sensor under conditions without interface stress. The inductance coefficient of the signal output module; When the bonding interface of the solid rocket motor is subjected to stress, causing deformation of the induced flexible substrate, the real-time output voltage of the system is acquired again. , ;in, The sensing coefficient of an inductive flexible interface stress sensor under stress. According to the system's initial reference voltage With real-time output voltage Determine the real-time output voltage change of the system. ; ; Based on the real-time output voltage change To determine the changes in the interface stress of the solid rocket motor casing.

[0018] The solid rocket motor casing interface stress monitoring system and method provided in this application utilizes an energy / signal input coil and an energy / signal output coil for the signal input module, the inductive flexible interface stress sensor, and the signal output module. By employing a high-frequency electromagnetic induction working mechanism, the sensor maintains high sensitivity while possessing rapid response capability. This achieves high-speed and stable bonding interface stress monitoring without damaging the solid rocket motor casing. Furthermore, it features thinness, high flexibility, and a simple coil circuit design, providing extremely high application value for monitoring the bonding interface stress and health status of solid rocket motors. Attached Figure Description

[0019] Figure 1A schematic diagram of the solid rocket motor casing interface stress monitoring system provided in this application; Figure 2 This is a front view of the inductive flexible interface stress sensor of this application; Figure 3 for Figure 2 The left view; Figure 4 for Figure 2 Cross-sectional view; Figure 5 This is a schematic diagram of the signal input module 1; Figure 6 This is a schematic diagram showing the bonding positions of the signal input module and the signal output module inside and outside the solid rocket motor in this application; Figure 7 This is a curve showing the relationship between the interfacial compressive stress value and the effective value of the sensor output signal in an embodiment of this application. Figure 8 This is a schematic diagram of the finite element simulation model of the induction coil in the experimental example of this application; Figure 9 This is a schematic diagram of the finite element simulation model of the induction coil after meshing in the experimental example of this application; Figure 10 This is a graph showing the effect of the number of turns of the induction coil on the induced voltage in the experimental examples of this application; Figure 11 This is a graph showing the effect of the wire diameter of the induction coil on the induced voltage in the experimental examples of this application; Figure 12 This is a graph showing the effect of the line spacing of the induction coil on the induced voltage in the experimental examples of this application; Figure label: 1-Signal input module, 2-Inductive flexible interface stress sensor, 3-Signal output module, 4-Wire, 5-Signal excitation module, 6-Signal processing module, 7-Host PC; 8-Signal transmitting induction coil, 9-Signal receiving induction coil, 10-Flexible sensing substrate; 11-Flexible sensing cover layer, 12-Induction coil, 13-Induction interface terminal; 14-Flexible cover layer, 15-Signal coil, 16-Signal interface terminal; 17-Solid rocket motor casing, 18-Liner, 19-Propellant grain. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] The solid rocket motor casing interface stress monitoring system and method provided in this application realize the sensing and wireless transmission of stress across the solid rocket motor bonding interface while meeting the requirements of high response speed interface stress sensing. It avoids the damage to the solid rocket motor casing caused by drilling and implantation, reduces the wiring complexity of solid rocket motor bonding interface monitoring, and facilitates the promotion and application of monitoring devices.

[0022] Figure 1 This is a schematic diagram of the solid rocket motor casing interface stress monitoring system provided in this application, as shown below. Figure 1 As shown, the system includes: a signal input module 1, an inductive flexible interface stress sensor 2, a signal output module 3, a signal excitation module 5, a signal processing module 6, and a host PC 7.

[0023] The output of the signal excitation module 5 is connected to the input of the signal input module 1 via wire 4. The output of the signal input module 1 is connected to the input of the inductive flexible interface stress sensor 2 via wire 4. The output of the inductive flexible interface stress sensor 2 is connected to the input of the signal output module 3 via wire 4. The output of the signal output module 3 is connected to the input of the signal processing module 6 via wire 4. The output of the signal processing module 6 is connected to the host PC 7 via wire 4.

[0024] Figure 2 This is a front view of the inductive flexible interface stress sensor of this application. Figure 3 for Figure 2 Left view, Figure 4 for Figure 2 Cross-sectional view, such as Figure 2-4 As shown, the inductive flexible interface stress sensor 2 includes: an inductive flexible substrate 10, and a signal transmitting induction coil 8 and a signal receiving induction coil 9 located on the upper and lower surfaces of the inductive flexible substrate 10; the inductive flexible substrate 10, the signal transmitting induction coil 8, and the signal receiving induction coil 9 have a centrally symmetrical structure.

[0025] The signal transmitting induction coil 8 and the signal receiving induction coil 9 each include: an induction coil 12 and a flexible induction covering layer 11 disposed on the upper and lower surfaces of the induction coil 12. Two induction interface terminals 13 are disposed on the induction coil 12. The induction coil 12 is fully wound in a planar spiral structure.

[0026] Specifically, the inductive flexible interface stress sensor provided in this application utilizes the electromagnetic induction phenomenon between its signal transmitting coil 8 and signal receiving coil 9 to achieve wireless transmission of sensor signals. When the signal transmitting coil 8 is subjected to external interface stress, the flexible substrate 10 deforms accordingly, causing a change in the distance between the signal transmitting coil 8 and the signal receiving coil 9, thereby affecting the output of the induced electromotive force of the signal receiving coil 9. By calibrating the relationship between the interface compressive stress experienced by the sensor and its output signal, the interface compressive stress can be monitored based on the output signal.

[0027] The signal transmitting coil 8 and signal receiving coil 9 are both made of flexible printed circuit boards (FPCs). FPCs are characterized by their flexibility, thinness, and high flexibility, and a mature mass production process has been established. The flexible sensing cover layer 11 is made of polyimide, the sensing coil 12 is made of copper, and the two sensing interface terminals 13 use RF IPEX interfaces. Considering that the curved propellant grains of solid propellants have low modulus and viscoelasticity, they are prone to deformation under environmental loads. Therefore, the sensors attached to them must have extremely high flexibility and structural stability. Polyimide has high voltage breakdown resistance and excellent bending resistance, effectively preventing copper circuit oxidation and environmental moisture corrosion. Copper has good ductility and long bending fatigue life, making it very suitable for use in flexible sensors attached to curved propellant grains.

[0028] The signal transmitting induction coil 8 and the signal receiving induction coil 9 are wound in a full-turn planar spiral structure to improve the coupling coefficient between the sensor signal transmitting induction coil 8 and the signal receiving induction coil 9, thereby converting minute interface deformations into more significant changes in the output electrical signal, thus greatly improving the sensor's sensitivity to force.

[0029] In this application, a pair of flexible planar coils for signal input module 1 and signal output module 3 are placed facing each other inside and outside the solid rocket motor casing to ensure radial alignment of the inner and outer coils.

[0030] The two ends of wire 4 are connected to interface terminals, which respectively connect the receiving end of signal input module 1 to the signal transmitting coil 8 of inductive flexible interface stress sensor 2, and the transmitting end of signal output module 3 to the signal receiving coil 9 of inductive flexible interface stress sensor 2. In this example, the length of wire 4 is... It is 20cm long and connects to the female RF IPEX interface terminal at both ends.

[0031] In this example, signal excitation module 5 has the capability to output electrical signals, providing excitation signals of various waveforms, both modulated and unmodulated. Signal excitation module 5 uses a signal generator to produce an AC signal with a peak-to-peak value of 10V and a frequency of 1MHz. The output terminal of the signal generator is connected to the transmitting terminal of the energy / signal input coil via wire 4, providing stable energy and signal to the system.

[0032] In this example, signal processing module 6 has the capabilities to demodulate, detect, calculate, convert, and acquire electrical signals, and can be configured with an independent power supply. Signal processing module 6 integrates multiple chips using a printed circuit board, enabling it to detect electrical signals, perform AD conversion, and process data, while reducing external interference through an independent power supply. The host PC 7 is protocol-compatible with signal processing module 6 and can record and process system data.

[0033] The system provided in this application works as follows: The signal excitation module 5 generates a uniform AC signal, which is supplied to the transmitting end of the signal input module 1 via wire 4 to induce electromagnetic induction, and its receiving end generates a uniform AC signal. The receiving end of the signal input module 1 is connected to the signal transmitting induction coil 8 via wire 4, exciting it to induce electromagnetic induction with the signal receiving induction coil 9, causing the signal receiving induction coil 9 to generate a uniform AC signal. The signal input signal of the signal receiving induction coil 9 is connected to the transmitting end of the signal output module 3 via wire 4, causing it to induce electromagnetic induction with the receiving end, generating an induced signal at the receiving end. The signal processing module 6 receives the induced signal output from the signal output module 3 and performs detection, AD conversion, and data processing. The host PC 7 obtains the relevant data from the signal processing module 7 via wire 4, and performs visualization and recording.

[0034] Furthermore, the outer diameter of the induction coil 12 Use 2cm wire diameter A 0.1mm flexible substrate 10 is constructed using a 10:1 polydimethylsiloxane material (i.e., the mass ratio of polydimethylsiloxane to the matching curing agent is 10:1), achieving a perfect match between the sensor's high elasticity and interfacial mechanical modulus. Modulus mismatch can easily lead to interfacial stress concentration and debonding under load, or cause strain transmission distortion due to localized stiffening effects. This matching design effectively avoids modulus mismatch problems, ensuring high linearity and excellent fatigue repeatability under stresses ranging from 0 to 1.1 MPa.

[0035] Furthermore, to reduce the impact of the sensor on the propellant column, the thickness of the sensing flexible substrate 10 is [increased / decreased]. The 2mm diameter is consistent with the circular outer frame of the signal transmitting induction coil 8 and the signal receiving induction coil 9 to avoid extreme shear stress on the edges when under pressure, which would cause stress concentration at the edges. Finally, silicone sealant is used for bonding.

[0036] Furthermore, Figure 5 This is a schematic diagram of the signal input module 1. In this application, the signal input module 1 and the signal output module 3 have the same structure. Figure 5 As shown, both the signal input module 1 and the signal output module 3 include: a pair of flexible planar coils; each flexible planar coil includes: a signal coil 15 and flexible covering layers 14 disposed on the upper and lower surfaces of the signal coil 15; two signal interface terminals 16 are disposed on the signal coil 15; the signal coil 15 is wound with a planar annular spiral structure, and its center is a hollow design with the number of internal turns removed.

[0037] Specifically, the flexible cover layer 14 is made of polyimide, the signal coil 15 is made of copper, and the signal interface terminal 16 uses an RF IPEX interface. The signal coil 15 is wound with a planar annular spiral structure. The outer diameter and inner diameter of the signal coil refer to the straight-line distance passing through the geometric center of the coil, connecting the outer edge of the outermost conductor to the edge of the innermost hollow area.

[0038] In this application, the outer diameter of the signal coil 16 With inner diameter The ratio is 2:1, which is used to remove the number of internal turns that contribute very little to electromagnetic mutual inductance but increase parasitic resistance, thereby optimizing the quality factor and magnetic field distribution of the coil, effectively resisting signal attenuation during cross-shell transmission, and ensuring communication stability.

[0039] In this application, the winding method of the signal coil 16 is different from that of the induction coil 12. In the inductive flexible interface stress sensor, since the working distance between the signal transmitting induction coil 8 and the signal receiving induction coil 9 is extremely small (the thickness of the inductive flexible substrate is 2mm) and they do not directly undertake the task of cross-shell communication, the induction coil 12 is wound with full turns to maximize the mutual inductance, ensuring that it can convert the small plate spacing deformation into a significant electrical signal and guarantee the high sensitivity of the sensor; while the cross-shell signal coil 15 is limited by the physical obstruction of the thick shell, and the magnetic field of the central turns cannot be effectively penetrated. The hollow design with a 2:1 ratio of internal turns can effectively improve its communication efficiency.

[0040] In this embodiment of the application, the outer diameter of the signal coil 15 With inner diameter The wire diameters are 6cm and 3cm respectively. Using a 0.2mm thickness, it has good flexibility, small weight and thickness. These characteristics enable it to perfectly fit the complex curved surface of solid rocket motors and seamlessly embed into the fragile bonding interface between the liner and the propellant grain. This avoids local stress concentration caused by the sensor as a rigid foreign object and fundamentally eliminates the risk of interface debonding induced by the sensor itself, thus realizing in-situ, non-destructive and high-fidelity stress monitoring.

[0041] Figure 6 This is a schematic diagram showing the bonding positions of the signal input module and the signal output module inside and outside the solid rocket motor, as shown in the diagram. Figure 6 As shown, in the pair of flexible planar coils of signal input module 1, one flexible planar coil serves as the transmitter and is placed outside the solid rocket motor housing 17, while the other serves as the receiver and is placed between the liner 18 and the propellant grain 19; in the pair of flexible planar coils of signal output module 3, one flexible planar coil serves as the transmitter and is placed between the solid rocket motor liner 18 and the propellant grain 19, while the other serves as the receiver and is placed outside the solid rocket motor housing 17; the pair of flexible planar coils of signal input module 1 and signal output module 3 are both placed coaxially opposite each other.

[0042] Specifically, signal input module 1 and signal output module 3 each include two planar flexible coils. The two planar coils (transmitter and receiver) of signal input module 1 are respectively positioned outside the solid rocket motor casing 17 and between the liner 18 and the propellant grain 19, coaxially facing each other. Similarly, the two flexible coils (transmitter and receiver) of signal output module 3 are respectively positioned between the solid rocket motor liner 18 and the propellant grain 19 and outside the casing 17, coaxially facing each other. This coaxial positioning ensures that the receiver is located on the central axis where the spatial magnetic flux density is strongest, maximizing the electromagnetic coupling efficiency across the casing and guaranteeing that electrical signal changes caused by minute stresses can stably penetrate the casing and be accurately acquired.

[0043] Furthermore, both the inductive flexible cover layer 11 and the flexible cover layer 14 in this application are made of the same non-elastic material, which includes any one of polyimide, polyvinyl chloride, and polyethylene terephthalate. The inductive interface terminal 13 and the signal interface terminal 16 both use radio frequency IPEX interfaces.

[0044] Experimental example: This experimental example demonstrates the following simulation of the induction coil 12 of the inductive flexible interface stress sensor 2: Based on the symmetry of the electromagnetic topology in both the power supply and communication processes, and aiming to maximize the energy transfer efficiency across the shell, the geometric parameters of the power supply coil group and the communication coil group are kept consistent. The excitation coil and induction coil parameters within each group are set to be identical. A three-dimensional independent simulation model of the induction coil group is established using multiphysics finite element software, as shown below. Figure 8As shown, the finite element simulation model of the coil assembly consists of four parts: an air domain, a solidified shell, an excitation coil, and an induction coil. The air domain is a cube with a side length much larger than the outer diameter of the coil. At the center of the air domain is a square plate with a thickness of 3 mm, which is used to simulate the non-metallic shell of a solid rocket motor. The excitation coil and the induction coil are coaxially attached to the upper and lower sides of the shell, respectively.

[0045] In finite element simulation, performing precise geometric modeling for each turn of the coil leads to a geometric increase in the number of meshes, significantly consuming computational resources. Therefore, this application employs a coil domain approach to treat the coil as an equivalent model. The coil region is defined as a homogeneous multi-turn model. This method does not establish geometric entities for individual wires but treats the coil region as a single conductive domain. By setting the number of turns, wire cross-sectional area, and fill factor, the induced current distribution is automatically allocated in the physical field. Transforming the complex geometry of a single-turn wire into a single conductive domain significantly reduces the difficulty of mesh generation while maintaining the accuracy of electromagnetic field calculations.

[0046] The AC frequency domain solution was performed using the "Magnetic Field" physics interface in the finite element method software. The outer surface of the air domain was set as a magnetically insulated boundary, forcing the magnetic field lines to be confined within the computational domain. For the excitation coil, it was configured as a "homogeneous multi-turn coil," a constant voltage AC excitation was applied, and a reference operating frequency was specified. The induction coil was also configured as a "homogeneous multi-turn coil," but the circuit terminals were set to an open circuit state, and the current was set to 0, to extract the effective value of the pure induced open-circuit voltage.

[0047] Because the electromagnetic field gradient changes drastically in the near-field region and tends to flatten out in the far-field region, the model adopts a method such as... Figure 9 The meshing strategy employed combines global free meshing with local high-density refinement. A larger-sized free tetrahedral mesh is used in the air domain, significantly reducing the total number of nodes while ensuring computational convergence, thus saving computational memory and time. High-density mesh refinement is applied to the coil domain and adjacent shell regions, accurately capturing the skin effect and proximity effect of the high-frequency alternating magnetic field on the coil conductor surface. This ensures extremely high numerical resolution for magnetic flux calculations spanning the 3mm shell gap, thereby guaranteeing the realism and reliability of the output voltage solution.

[0048] In a cross-shell wireless transmission system, the geometric topology of the induction coil directly determines its core lumped parameters, such as self-inductance, AC internal resistance, and cross-shell mutual inductance, thus affecting the system's induced voltage. This experimental example, based on an established independent coil group model, uses the controlled variable method to investigate the influence and underlying mechanisms of coil turns, line width, line spacing, and inner diameter on the system's output characteristics, while keeping the excitation signal parameters (frequency 1MHz, input voltage amplitude 10V) constant.

[0049] (1) Analysis of the influence of the number of turns of the induction coil Maintain line width Line spacing Keep the number of turns constant. The number of turns was increased from 10 turns to 60 turns in increments of 5 turns. Simulation results show the effect of the number of turns on the induced voltage. Figure 10 As shown. Simulation results show that when the number of coil turns... As the number of turns gradually increases from 10 to 60, the induced voltage at the receiving end exhibits a significant non-linear monotonically increasing trend. Specifically, in the range with fewer turns, the voltage increase slope is extremely steep; however, when the number of turns exceeds 30, the voltage growth curve gradually flattens out. Increasing the number of coil turns is equivalent to increasing the spatial superposition of the alternating magnetic field, directly leading to cross-shell mutual inductance. The significant improvement in [the efficiency / performance] enhances the induced electromotive force. However, with [the improvement / performance]... With the increase in [unclear], the total length of the excitation coil's wires is significantly extended, and the coil's DC internal resistance and self-inductance [unclear]. Both exhibit a rapid, non-linear increase. This dramatic increase in high-frequency inductive reactance severely limits the excitation current in the primary circuit. At higher turns, the excitation current... The benefits from the decline gradually offset the gains from mutual inductance. The increased gains lead to a slowdown in the increase in output voltage, which eventually reaches saturation.

[0050] (2) Analysis of the influence of wire diameter Maintain number of turns Line spacing Keep the wire diameter unchanged. The wire diameter is increased from 0.1 mm to 0.6 mm in increments of 0.1 mm. Simulation results show the effect of wire diameter on output. Figure 11 As shown in the figure. Simulation results show that as the wire diameter increases from 0.1 mm to 0.6 mm, the output voltage increases from approximately 3.7 V to 5.3 V, exhibiting an overall approximately linear positive correlation growth trend. The change in wire diameter mainly affects the high-frequency impedance characteristics of the system. Under 1 MHz high-frequency excitation, due to the skin effect, the alternating current mainly flows in the surface layer of the conductor. Increasing the wire diameter not only directly increases the cross-sectional area of ​​the conductor and reduces the DC resistance, but more importantly, it significantly increases the effective conductive perimeter of the high-frequency current, greatly weakening the AC impedance increment caused by the skin effect. Under a constant input voltage, the reduction in the internal resistance of the primary excitation coil enables the circuit to generate a larger excitation current, producing a stronger primary magnetomotive force, thereby significantly increasing the trans-shell induced voltage.

[0051] (3) Analysis of the influence of line spacing Maintain number of turns wire diameter Keep it the same, change the line spacing The line spacing is increased from 0.1 mm to 0.6 mm in increments of 0.1 mm. Simulation results show the effect of line spacing on output. Figure 12 As shown in the figure. The results indicate that when the wire spacing increases from 0.1 mm to 0.6 mm, the induced voltage increases almost linearly. First, with a fixed number of turns and inner diameter, increasing the wire spacing directly leads to a macroscopic expansion of the overall outer diameter of the coil. For planar helical coils, a larger overall aperture means a smaller divergence angle of the generated magnetic field lines in space, enabling the effective magnetic flux to be projected over a greater axial distance. When crossing a fixed shell thickness of 3 mm, the magnetic field coupling cross section of the large-aperture coil is larger, resulting in a higher mutual inductance coefficient. Second, increasing the wire spacing effectively weakens the proximity effect caused by the mutual compression of alternating magnetic fields between adjacent conductors, further reducing the high-frequency AC equivalent resistance of the coil and improving the excitation efficiency.

[0052] Meanwhile, to ensure high yield of the prototype and its practical engineering application value, the geometric parameters of the coil must be designed to strictly match the standard flexible printed circuit board (FPCB) process specifications. For the standard 1oz copper-thickness FPCB process, considering the precision limits of photolithography etching and the side etching effect, the minimum wire diameter of the planar spiral coil... and minimum line spacing All traces must be limited to 4 mil (approximately 0.1 mm) to avoid broken wires or short circuits due to solder bridging. To allow the coil center tap signal to be led out to the back, a center via must be provided. The mechanical drilling process requires a minimum inner diameter of 0.1 mm and a minimum outer diameter of 0.3 mm for the via, and an insulation gap of 0.1 mm must be maintained between the via edge and the innermost trace. Considering the subsequent milling, depaneling, and thermal expansion and contraction tolerances of the FPCB, a safety insulation and anti-peeling distance of at least 0.3 mm must be reserved between the outermost trace of the coil and the physical edge of the substrate. Based on the above extreme process constraints, this study compresses the conductor size to the process limit in order to obtain the maximum number of magnetic flux linkage turns.

[0053] Based on comprehensive calculations and layout, the final geometric parameters of the induction coil in this application are determined as follows: number of turns. wire diameter Line spacing Simulation results show that, under these parameters, the cross-solid rocket engine casing interface stress sensing and wireless power supply communication system has higher accuracy and sensitivity in monitoring the interface stress of solid rocket engine casings.

[0054] This application also provides a method for monitoring the interface stress of a solid rocket motor casing, comprising the following steps: Step 1: Under the initial state of no interfacial stress, obtain the initial reference voltage of the system. , ;in, The inductance coefficient of signal input module 1. The sensing coefficient of the inductive flexible interface stress sensor 2 under the condition of no interface stress is given. The inductance coefficient of the signal output module (3); Step 2: When the solid rocket motor bonding interface is subjected to stress, causing deformation of the induced flexible substrate, the real-time output voltage of the system is acquired again. , ;in, The sensing coefficient of the inductive flexible interface stress sensor 2 under stress. Step 3: Based on the system's initial reference voltage With real-time output voltage Determine the real-time output voltage change of the system. ; ; Step 4: Based on the real-time output voltage change To determine the changes in the interface stress of the solid rocket motor casing.

[0055] Specifically, based on the principle of electromagnetic induction, the system provided in this application can be simplified to a series connection of three sets of induction coils, wherein signal input module 1 is the first set of induction coils, and the induction coefficient (the ratio of output signal to input signal) is... The signal transmitting induction coil 8 and the signal receiving induction coil 9 of the inductive flexible interface stress sensor 2 form the second set of induction coils, with an induction coefficient of [missing value]. Signal output module 3 is the third set of induction coils, with an induction coefficient of... In the embodiments of this application, the overall inductance coefficient of the system is... It can be defined as the product of the induction coefficients of the three sets of induction coils, that is... .

[0056] In actual monitoring, the stable and uniform AC voltage input to signal excitation module 5 is assumed to be... The real-time output voltage received by the system It can be represented as In the initial state without interfacial stress, the sensor's sensing coefficient is... The initial reference voltage recorded by the system is When the bonding interface is subjected to stress, causing deformation of the flexible substrate, the sensor's sensing coefficient changes accordingly. At this time, the real-time output voltage change This can be determined using the following model:

[0057] This application uses the above-mentioned product model to reduce the fixed cross-shell transmission loss ( and ) and dynamic sensor response ( Mathematically, they are clearly decoupled. Because... , , During the monitoring process, all values ​​are constants; therefore, the voltage change in the system output is constant. It depends entirely on the change in the sensor's sensing coefficient. (Right now This allows the final calculated voltage change signal to maintain a direct linear proportional relationship with the interface stress change, thus greatly simplifying the subsequent data calibration and solution process.

[0058] When compressive stress is generated at the bonding interface of a solid rocket motor, the flexible substrate 10 of the inductive flexible interface stress sensor 2 is heightened under stress. The reduction brings the signal transmitting induction coil 8 closer to the signal receiving induction coil 9, strengthening the electromagnetic induction between them, and increasing the overall induction coefficient of the system. Increase. Under stable and uniform AC signal excitation, the system outputs a signal greater than the initial voltage value under stress-free conditions. By analyzing and calibrating this signal, the stress change at the bonding interface of the solid rocket motor can be obtained.

[0059] When tensile stress is generated at the bonding interface of the solid rocket motor, the height of the inductive flexible substrate 10 under stress is [not specified]. The increase in coil size moves the signal transmitting induction coil 8 further away from the signal receiving induction coil 9, reducing the electromagnetic induction between them and increasing the overall induction coefficient of the system. The voltage is reduced. Under stable and uniform AC signal excitation, the system outputs a signal that is lower than the initial voltage value under stress-free conditions. By analyzing and calibrating this signal, the stress change at the bonding interface of the solid rocket motor can be obtained.

[0060] In this embodiment, a high-precision vertical press is used to apply a compressive stress of 0-1 MPa. The interfacial compressive stress value is applied gradually in increments of 50 kPa, ranging from 0 to 1.1 MPa, and held for 10 seconds at each stress. The sensor output voltage under each stress is precisely recorded using a multimeter. By calculating the voltage change caused by each applied stress, the compressive stress-output signal change curve of the sensor can be obtained as shown below. Figure 7 As shown.

[0061] The system and method provided in this application feature wireless power supply and communication capabilities, enabling a wireless monitoring solution for solid rocket motor interface stress monitoring. This significantly reduces damage to the solid rocket motor casing and simplifies monitoring wiring. Furthermore, both the transmission method and the interface stress sensor used in this system are based on the principle of electromagnetic induction, allowing for increased system sensing speed by raising the signal frequency, thus achieving high-speed monitoring.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A solid rocket motor casing interface stress monitoring system, characterized in that, include: Signal input module (1), inductive flexible interface stress sensor (2), signal output module (3), signal excitation module (5), signal processing module (6), host PC (7); The output end of the signal excitation module (5) is connected to the input end of the signal input module (1) via a wire (4), and the output end of the signal input module (1) is connected to the input end of the inductive flexible interface stress sensor (2) via a wire (4); the output end of the inductive flexible interface stress sensor (2) is connected to the input end of the signal output module (3) via a wire (4), the output end of the signal output module (3) is connected to the input end of the signal processing module (6) via a wire (4), and the output end of the signal processing module (6) is connected to the host PC (7) via a wire (4); The inductive flexible interface stress sensor (2) includes: an inductive flexible substrate (10), and a signal transmitting induction coil (8) and a signal receiving induction coil (9) located on the upper and lower surfaces of the inductive flexible substrate (10); the inductive flexible substrate (10), the signal transmitting induction coil (8), and the signal receiving induction coil (9) have a centrally symmetrical structure; and the external dimensions of the signal transmitting induction coil (8), the signal receiving induction coil (9), and the inductive flexible substrate (10) are matched, and the three are bonded together by silicone sealant; The signal transmitting induction coil (8) and the signal receiving induction coil (9) each include: an induction coil (12) and a flexible induction covering layer (11) disposed on the upper and lower surfaces of the induction coil (12). Two induction interface terminals (13) are disposed on the induction coil (12). The induction coil (12) is fully wound in a planar spiral structure.

2. The solid rocket motor casing interface stress monitoring system according to claim 1, characterized in that, The inductive flexible cover layer (11) is made of a non-elastic material, including any one of polyimide, polyvinyl chloride, and polyethylene terephthalate; the thickness of the inductive flexible cover layer (11) is 2 mm.

3. The solid rocket motor casing interface stress monitoring system according to claim 1, characterized in that, The induction coil (12) has an outer diameter of 2 cm, a wire diameter of 0.1 mm, and a number of turns. Wire diameter and spacing .

4. The solid rocket motor casing interface stress monitoring system according to any one of claims 1-3, characterized in that, The signal input module (1) and the signal output module (3) each include: a pair of flexible planar coils; each flexible planar coil includes: a signal coil (15) and a flexible covering layer (14) disposed on the upper and lower surfaces of the signal coil (15); two signal interface terminals (16) are disposed on the signal coil (15). The signal coil (15) is wound with a planar annular spiral structure, and its center is a hollow design with the number of internal turns removed.

5. The solid rocket motor casing interface stress monitoring system according to claim 4, characterized in that, The ratio of the outer diameter to the inner diameter of the signal coil (15) is 2:1, and its wire diameter is 0.2mm.

6. The solid rocket motor casing interface stress monitoring system according to claim 4, characterized in that, Of the pair of flexible planar coils in the signal input module (1), one flexible planar coil serves as the transmitting end and is placed outside the solid rocket motor housing (17), while the other serves as the receiving end and is placed between the liner (18) and the propellant grain (19). Of the pair of flexible planar coils in the signal output module (3), one flexible planar coil serves as the transmitting end and is placed between the solid rocket motor liner (18) and the propellant grain (19), while the other serves as the receiving end and is placed outside the solid rocket motor casing (17). The pair of flexible planar coils are placed coaxially opposite each other.

7. The solid rocket motor casing interface stress monitoring system according to claim 4, characterized in that, The flexible covering layer (14) is made of a non-elastic material, which includes any one of polyimide, polyvinyl chloride, and polyethylene terephthalate.

8. The solid rocket motor casing interface stress monitoring system according to claim 4, characterized in that, Both the induction coil (12) and the signal coil (15) are made of copper. Both the sensing interface terminal (13) and the signal interface terminal (16) adopt the radio frequency IPEX interface.

9. The solid rocket motor casing interface stress monitoring system according to claim 4, characterized in that, The inductive flexible substrate (10) is made of 10:1 polydimethylsiloxane material, that is, the mass ratio of polydimethylsiloxane to the matching curing agent is 10:

1.

10. The monitoring method of the solid rocket motor casing interface stress monitoring system according to claim 1, characterized in that, include: Under the initial state of no interfacial stress, obtain the initial reference voltage of the system. , ;in, The inductance coefficient of the signal input module (1) The sensing coefficient of the inductive flexible interface stress sensor (2) under the condition of no interface stress is given. The inductance coefficient of the signal output module (3); When the bonding interface of the solid rocket motor is subjected to stress, causing deformation of the induced flexible substrate, the real-time output voltage of the system is acquired again. , ;in, The sensing coefficient of the inductive flexible interface stress sensor (2) under stress; According to the system's initial reference voltage With real-time output voltage Determine the real-time output voltage change of the system. ; ; Based on the real-time output voltage change To determine the changes in the interface stress of the solid rocket motor casing.

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