Solid Rocket Motor Grain Research Articles

Reliability analysis of the solidification cooling of solid rocket motor grain material.

The reliability of solid rocket motor grain structure during solidification cooling is analyzed. First, a three-dimensional parametric modeling of the grain is carried out by ANSYS finite element software. The dangerous point and dangerous moment can be obtained based on the transient and dynamic thermo-structure coupling under the cooling condition. Moreover, the maximum equivalent strain and temperature values are extracted. Second, a dual neural network model is established based on the probability distribution of the copula function and specific parameters. Finally, the instantaneous reliability during the solidification cooling process of the grain is calculated. Then, the dynamic reliability analysis is realized. The proposed method reduces the computational cost of dynamic reliability of grain structure, demonstrating its applicability in practical engineering problems. Furthermore, comparing the results of the proposed method with the MCS method demonstrates that the proposed method has high computational accuracy.

Engineering evaluation method for adaptability of SRM to low-temperature operation

In view of the adaptability of the solid rocket motor (SRM) to work at low temperatures, an engineering evaluation method is proposed. A test method that can characterize the low-temperature ignition bearing capacity of the SRM is designed and put forward. At the same time, a comprehensive evaluation method for the adaptability of the SRM to work at low temperatures is proposed. It is combined with the numerical simulation analysis of the structural integrity of the SRM grain. The evaluation results obtained by this method are in good agreement with the SRM low-temperature test results. It can provide a basis for the reliability design and engineering development of the SRM low-temperature operation.

Calculation of Instantaneous Reliability of Grain Structure Under Small Samples

Under the condition of small sample, the performance parameters’ interval quantization and instantaneous reliability calculation of solid rocket motor grain structure are researched. Two important mechanical properties of material: Relaxation modulus and Poisson’s ratio are obtained by experiments of grain material. Since the data of parameters obtained are a small sample, the method of gray theory is used to mine the experimental data. It realizes the uncertainty quantitative analysis of grain material performance parameters and obtains the quantitative interval of performance parameters. Considering that the evidence theory can directly attribute probabilistic mass to the set or interval, the instantaneous reliability of grain structure is analyzed based on the evidence theory. By establishing the relationship between failure surface and the frame of discernment, and using the belief function and plausibility function to obtain the upper and lower bound probability distribution of structural reliability and failure probability, the instantaneous reliability probability interval of structure is obtained.

Numerical Simulation on Structural Integrity of Grain with Large Increased Area Ratio for Solid Rocket Motor

To evaluate the structural integrity of a type of solid rocket motor grain with a largely increased area ratio using free-loading modified double-base grain, the Schapery integral nonlinear viscoelastic constitutive equation with damage is derived, and the numerical simulation model of solid rocket motor grain is constructed. According to the mission profile of the grain during the equipment period, the numerical simulation research on the mechanical response characteristics of the grain under three typical working conditions, namely, platform vibration, underwater explosion impact, and ignition pressurization during the launch is carried out. The simulation results show that under the three typical working conditions, the grain will not produce structural damage and defects, and the mechanical response of the grain under the platform vibration and explosion impact load is far less than that under the launch ignition pressurization. The ignition pressurization should be considered in the grain structural integrity design of this type or similar structure solid rocket motor.

Identification of Viscoelastic Parameters for Composite Propellant by Indentation Technique

AbstractA method for identifying the relaxation modulus or creep compliance of composite propellant based on indentation technique is proposed, which can rapidly and nondestructively measure the mechanical properties of solid rocket motor grain in storage. According to viscoelastic indentation theories, a constitutive model for conical indentation is derived to predict the mechanical parameters of composite propellants. The indentation test with different loading rates and the traditional tensile stress relaxation test for a certain PBT composite propellant were carried out to verify the feasibility of the proposed method. The results show that the prediction results calculated by the constitutive model are in good agreement with the load‐displacement curves of the indentation test, and the mechanical parameters identified by the constitutive model are similar to those parameters fitted by the tensile stress relaxation test. Relevant methods and conclusions can provide a reference for structural analysis and storage life prediction of solid rocket motors.

The Numerical Simulation Method of the Slot Crack Groups’ Effect Analysis for Solid Rocket Motor Grain

This study is aimed at the stability and effect of the crack groups in the solid rocket motor (SRM) grain when it was launched at normal temperature. Based on the nearly incompressible viscoelastic finite element method, several cracks were preset in a critical location along with the dangerous point of the back slot. The singular crack elements at the tips of crack groups were established to calculate the J -integral. With the position of the cracks, the J -integral of the various crack tips was, respectively, calculated to prejudge its stability and the group effect. Finally, the experimental measured critical J -integral J IC was compared with the numerical simulation result. The results showed that in the collinear crack groups, the enhancement effect of the main crack was caused by the nearest second crack, and the significant shielding effect of the main crack was occurred in the noncollinear crack groups. Moreover, the experimental result showed that the numerical method had high accuracy.

Multiobjective Optimization Method of Solid Rocket Motor Finocyl Grain Based on Surrogate Model

To improve the performance of a solid rocket motor (SRM), a multiobjective optimal design method that can consider the structural integrity, internal ballistic performance, and loading performance of the SRM was proposed based on parametric modeling and surrogate modeling technology. Firstly, the parametric modeling technology was introduced into the field of structural integrity analysis for a high-loading SRM, based on which the influences of load and geometric parameters on the maximum von Mises strain of the SRM grain were analyzed, which effectively improved the sampling speed and prediction accuracy of the surrogate model. Combining the calculation models of the combustion surface area and volume loading fraction of the SRM, the Pareto optimal solution set was obtained based on the NSGA-II algorithm. Under the constraints of the optimization model, the maximum von Mises strain can be reduced by up to 26.72% and the volume loading fraction can be increased by up to 1.83% compared with the original. In addition, the optimal design method proposed in this paper is significantly superior in efficiency, capable of reducing both the single sampling time by more than 95% and the number of numerical simulations from 20,000 to 400, and the average prediction deviation is only 1.87%.

Automated Defect Analysis System for Industrial Computerized Tomography Images of Solid Rocket Motor Grains Based on YOLO-V4 Model

As industrial computerized tomography (ICT) is widely used in the non-destructive testing of a solid rocket motor (SRM), the problem of how to automatically discriminate defect types and measure defect sizes with high accuracy in ICT images of SRM grains needs to be urgently solved. To address the problems of low manual recognition efficiency and data utilization in the ICT image analysis of SRM grains, we proposed an automated defect analysis (ADA) system for ICT images of SRM grains based on the YOLO-V4 model. Using the region proposal of the YOLO-V4 model, a region growing algorithm with automatic selection of seed points was proposed to segment the defect areas of the ICT images of grains. Defect sizes were automatically measured based on the automatic determination of defect types by the YOLO-V4 model. In this paper, the image recognition performance of YOLO-V4, YOLO-V3, and Faster R-CNN models were compared. The results show that the average accuracy (mAP) of the YOLO-V4 model is more than 15% higher than that of the YOLO-V3 and Faster R-CNN models, the F1-score is 0.970, and the detection time per image is 0.152 s. The ADA system can measure defect sizes with an error of less than 10%. Tests show that the system proposed in this paper can automatically analyze the defects in ICT images of SRM grains and has certain application value.

Hydrogen peroxide – A promising oxidizer for rocket propulsion and its application in solid rocket propellants

This paper discusses the potential use of hydrogen peroxide as oxidizer for solid rocket propulsion. While hydrogen peroxide is a liquid in normal conditions, it may be used in solid rocket motor grains. Use of hydrogen peroxide of HTP class (High Test Peroxide) is proposed. It has been known for many decades but its utilization has been historically limited to liquid propellants. Until recently is application even in liquid state in rocket propulsion for space and defence has been limited due to storability and safety issues. With the availability of new grades of HTP with higher purity and concentrations, enhanced performance, safety and storability are possible. This results in HTP being considered for a wide range of rocket propulsion systems: as oxidizer in bipropellant and hybrid propulsion systems, as well a monopropellant. To ensure proper analysis of the potential of using HTP in next-generation solid rocket propellants, this paper reviews existing rocket propulsion applications of HTP. Modern use requires high performance and common current composite propellant compositions utilize ammonium perchlorate (AP) as oxidizer, what has several disadvantages, which are discussed. Alternative oxidizing compounds include ammonium dinitiramide (ADN), ammonium nitrate (AN), hydrazinium nitroformate (HNF), hexanitrohexaazaisowurtzitane (HNIW) and several other secondary explosives. Key properties of solid propellant oxidizers are listed and discussed. The need for further alternatives, despite numerous recent advances in solid rocket oxidizer technology is justified. The global push forward high performance green propulsion is one of the main motivations behind considering HTP for solid rocket propulsion. Theoretical performance of solid rocket motors using solid grains containing a high mass fraction of HTP is presented. This includes performance considering several fuels and additives and different oxidizer loadings. Up to date concepts of using hydrogen peroxide in solid propellants are reviewed. Solid cryogenic propellants using hydrogen peroxide are mentioned, but focus is given to solid propellants which could ensure flexible operations, thus use in state-of-the-art solid rocket motors. Challenges of HTP application as an oxidizer for solid propulsion are listed. This includes a discussion concerning its reactivity, thus limited compatibility with organic materials. Recommendations for further experimental work are proposed. Potential technology applications are listed with explanations why these particular niches may benefit from utilization of the new solid propellant technology.

Optimization Method of Segmented Grain Structure Based on Shortest Distance Proxy Model

The structural integrity of the grain is very important for the grain with complex geometry. Large section column structure has its particularity, differs from that of a single column, its length to diameter ratio is large and absolute meat the increase of the thickness, particles of geometric shape and size of the key factors to determine the gas production rate and its change rule of the engine, at the same time, the engine thrust and pressure change with time, particle size determines the volume and weight of the combustion chamber,Therefore, the particle design of solid rocket motor determines the quality design index of the engine to a large extent.In order to improve the efficiency of model optimization, an agent model is established in this paper. The prediction accuracy of the model depends on the distance between prediction points and sample points. The shortest distance hierarchical clustering algorithm is used to improve the prediction accuracy.Through the research, the comprehensive effect of the key factors affecting the structural integrity of the propellant and the law of the influence on the structure and safety margin of the propellant are obtained. The research method and law can provide support for the large solid motor grain design, and provide theoretical reference for the solid rocket motor grain structure multi-parameter optimization design.

Analysis of the stress state of solid propellant grains under internal pressure load

In order to determine the stress state of the solid rocket motor grain under the internal pressure load, based on the finite element numerical simulation calculation, the length and size requirements of the grain under the internal pressure simplified to a plane strain problem are obtained. Numerical simulation calculations are further carried out for the grains in plane strain state that meet the simplified conditions, and the radial and circumferential stress states of the grains are obtained. The numerical simulation results are compared with the viscoelastic theoretical solution of the grains under the same material parameters. The results show that when the aspect ratio exceeds 2.5, the axial strain is approximately 0, which can be equivalent to a plane strain problem. In addition, the analysis shows that under the action of internal pressure, the plane strain grains are in a bidirectional compression stress state with a radial and circumferential stress ratio of approximately 1:1. Finally, by comparing the numerical solution and the analytical solution, it is found that the relative error is within 3%, which verifies the correctness of the numerical simulation calculation results.

Failure correlation reliability analysis of solid rocket motor grain based on polynomial chaos expansion

Polynomial chaos expansion (PCE) method has better fitting capacity and rate of convergence than other traditional reliability analysis methods. This paper presents the failure correlation reliability analysis based on PCE for improving calculation precision and reducing computational cost. An example of solid rocket motor grain solidification and cooling is analyzed, and the failure correlation reliability between inner surface crack and insulation layer debonding is studied. Results show that an accurate failure correlation reliability analysis result can be obtained by proposed method, and the precision and efficiency of the proposed method are verified by comparing it with traditional methods.

A Viscoelastic Constitutive Model of Composite Propellant Considering Dewetting and Strain‐Rate and its Implementation

AbstractA reasonable constitutive model is the prerequisite to accurately estimate the mechanical behaviours of the composite propellant and the structural analysis of solid rocket motor grain. Through coaxial tensile tests, the viscoelastic properties of the solid propellant, especially dewetting, under actual loading is studied. The concept of dewetting point is proposed to describe the behaviour of dewetting. Based on the experimental results, a nonlinear viscoelastic constitutive model considering strain rate was applied to composite propellant and modified by the dewetting factor to extend the original one to a wide strain variation. Based on the updated Lagrangian approach, the incremented form of the constitutive model is deduced using the updated Kirchhoff stress tensors and strain tensors. By the numerical method and user defined material subroutine, the model is implemented to the 3D structural analysis of the grain during the ignition pressurization procedure. The model is validated by one set of experiments and further grain structural integrity analysis is carried out to study the influence of the pressurization rate and dewetting elongation.

Structural integrity analysis and experimental investigation for solid rocket motor grain subjected to low temperature ignition

The structural integrity of solid rocket motor(SRM) grain is severely tested owing to the combined action of low temperature and pressure load under the load case of low temperature ignition. The three dimensional finite element model of SRM was created to analyze the structural integrity of the SRM grain subjected to low temperature and ignition pressure based on three dimensional viscoelastic finite element method via MSC.Patran/Marc. Meanwhile, cold pressurization test was applied on certain SRM. The experimental result and numerical result were compared based on uncoupling principal of temperature and pressure. The result show that the safety factor of solid rocket motor grain is 2.46 which can meet the requirement of structural integrity. The experimental results are in good agreement with the simulation results. Relevant research methods and conclusions can provide reference for the design, analysis and test of SRMs.

On-line Monitoring of SRM Grain Structure Based on embedded FBG Sensor

This paper proposes the use of FBG (Fiber Bragg grating) sensors for SRM (Solid Rocket Motor) grain structure continuous Structural Health Monitoring(SHM) as they are generally considered as the preferable solution in flammable and explosive environments, due to their electromagnetic interference immunity and their inherent electrical and explosion safe characteristics. The processes of SRM manufacturing(curing of propellant and demoulding) were monitored. The curing degree of the propellant can be monitored by wavelength change of the FBG sensors, and this provides a new monitoring method for curing of the propellant grain. The monitoring of the demoulding process shows that the sensor is very sensitive to the tensile and compressive stresses on grain and can be used for on-line monitoring of grain in a mechanical environment. In monitoring simulated debonding test, the failure process of crack initiation, expansion and direction all can be monitored by the FBG sensors. After the crack is produced, the location of the debonding can be determined by the variation of the different sensors.

Erratum to “Combined Acceleration Methods for Solid Rocket Motor Grain Burnback Simulation Based on the Level Set Method”

Erratum to “Combined Acceleration Methods for Solid Rocket Motor Grain Burnback Simulation Based on the Level Set Method”

Combined Acceleration Methods for Solid Rocket Motor Grain Burnback Simulation Based on the Level Set Method

A detailed study of a set of combined acceleration methods is presented with the objective of accelerating the solid rocket motor grain burnback simulation based on the level set method. Relevant methods were improved by making use of unique characteristics of the grains, and graphical processing unit (GPU) parallelization is utilized to perform the computationally intensive operations. The presented flow traced the expansion of burning surfaces, and then Boolean operations were applied on the resulting surfaces to extract various geometric metrics. The initial signed distance field was built by an improved distance field generating method, and a highly optimized GPU kernel was used for estimating the gradient required by the level set method. An innovative Boolean operation method, thousands of times faster than ordinary ones, was ultimately proposed. Performance tests show that the overall speedup was close to 15 on desktop-class hardware, simulation results were proven to converge to analytical results, and the error boundary was 0.25%.

ПРИМЕНЕНИЕ МЕХАНИКИ РАЗРУШЕНИЯ К ОБОСНОВАНИЮ ВЫБОРА РАЦИОНАЛЬНЫХ ВАРИАНТОВ КОНСТРУКТИВНЫХ ЭЛЕМЕНТОВ ЗАРЯДОВ РДТТ

ПРИМЕНЕНИЕ МЕХАНИКИ РАЗРУШЕНИЯ К ОБОСНОВАНИЮ ВЫБОРА РАЦИОНАЛЬНЫХ ВАРИАНТОВ КОНСТРУКТИВНЫХ ЭЛЕМЕНТОВ ЗАРЯДОВ РДТТ

Structural Analysis of Solid Rocket Motor Grain with Aging and Damage Effects

The nonlinear viscoelastic behavior of composite solid propellants is studied by using a three-dimensional thermoviscoelastic constitutive model. In this model, the effects of the time-dependent Poisson ratio, aging, damage, and thermoviscoelasticity are considered. Viscoelastic constitutive equations are numerically discretized into an incremental form by using integration algorithms. An Abaqus-based user material subroutine is presented, and a structural analysis module for solid rocket motor grain is built. Based on the analysis module, the structural responses of solid rocket motor grain are analyzed when subjected to typical loadings during its service life. Obtained results indicate that, differing from the classic linear viscoelastic model, the present model gives satisfactory numerical results closely consistent to the actual performance variation of the propellant. The designed structural analysis module could be applied to the structural analysis for practical solid rocket motors.

An Optimization Approach of SRM Sphere Slot Grain Design Based on Improved Differential Evolution Algorithm

The sphere slot is a 3D configuration of solid rocket motor (SRM) grain. Accompanied with multi-design-variable and strong constraints, its optimization is always a complicated problem. In this article, a methodology has been presented for the optimization of sphere slot grain configuration. Parameterized CAD model method and unsteady lumped parameter internal ballistic model are adopted to evaluate the performance of sphere slot grain to establish the optimization objective and constraint functions. An improved differential evolution algorithm incorporated with Oracle penalty function method is developed and applied on the optimization to solve global optimum solution converging difficulty of multi-variable constrained problem. The approach is validated by a small sphere slot SRM. The results illustrate it is effective method and has robustness and efficient capacity to explore the design space for global optimum solution of sphere slot grain.