Effect of Cooling Load on the Safety Factor of Propellant Grains

Chu, Hung Ta; Chou, Jung-Hua

doi:10.2514/1.b34579

Cited by 12 publications

(5 citation statements)

References 10 publications

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“…)a nd low temperatures (< 253 K) [3][4][5].H owever,u pt on ow,t here is limited information available on the behaviors of solid propellants under those loading conditions. Based on the test results at low strain rates (< 1s À1 )a nd the time-temperature superposition principle (TTSP), the mechanical properties of solid propellants over ac onsiderable rangeo ft ime and the structurali ntegrity of propellant grain have beena nalyzed [6,7].N evertheless,i ti ss till difficult to predict the mechanical properties of solid propellants during ignitiono fS RM at low temperatures and more effectively analyze the structural integrity of propellant grain.…”

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confidence: 99%

Experimental Investigation on High Strain Rate Tensile Behaviors of HTPB Propellant at Low Temperatures

Wang¹,

Hu²,

Guang³

2015

Propellants Explo Pyrotec

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[a] 1IntroductionThe reliability of as olid rocketm otor (SRM),w hich serves as the propulsion system and the key component of atactical missile, is extraordinary important. The performance of such motori si nfluenced largely by the structural integrity of propellant grain [1].H owever, it is difficult to analyze the structurali ntegrity of propellant grain becauses olid propellant is viscoelastic in nature and its mechanical properties and fracture mechanisms are highly strain-rate and temperature dependent [2].T herefore,f or reliable propellant grain structurali ntegrity analysis it is very importantt ok now the behaviors of solid propellantu nderv arious loading conditions.During ignition of SRM for the tactical missiles at low temperatures, the propellant faces the challenget oa djust to high strain rates (1-10 2 s À1)a nd low temperatures (< 253 K) [3][4][5].H owever,u pt on ow,t here is limited information available on the behaviors of solid propellants under those loading conditions. Based on the test results at low strain rates (< 1s À1 )a nd the time-temperature superposition principle (TTSP), the mechanical properties of solid propellants over ac onsiderable rangeo ft ime and the structurali ntegrity of propellant grain have beena nalyzed [6,7].N evertheless,i ti ss till difficult to predict the mechanical properties of solid propellants during ignitiono fS RM at low temperatures and more effectively analyze the structural integrity of propellant grain. Previous researches have shown that it is very difficult to studyt he mechanical properties of materials at strain rates ranging from 1t o1 0 2 s À1[8].T he lower strengthm akes it hardert oc onduct the uniaxial tensile test on solid propellant undert hosel oading conditions. However,R en et al. [9] have statedt hat at the same temperature and strain rate, it is easier for solid propellant to fail because of the tensilel oading, rather than the compressivel oading.T herefore, test methods are required that are beyondt he usual uniaxialt est to study the tensile behaviorso fs olid propellant at highs train rates (1-10 2 s À1)and low temperatures (< 253 K). Solid propellant based on hydroxyl-terminated polybutadiene (HTPB) binderh as become the workhorse propellant in present-day SRM worldwide [10].I ts high strain ratet ensile behaviors have beens uccessfully studied in our previous work basedo nt he tests at strain rates lowert han 14.14 s À1 [11].H owever,t he effects of strain rate and temperature on the tensile mechanical properties and fracture mechanisms of the propellant at higher strain rates are still unclear.M eanwhile, the effects of other influencingf actors )a nd temperatures (233-298 K) using an INSTRONt estingm achine. Scanning electron microscopy (SEM) was employedt oo bserve the tensile fracture surfaces. Experimental results indicate that strain rate, temperature and test environment remarkably influence the tensile behaviors of HTPB propellant. The stress-strain curves exhibitt hreed ifferent shapes.T he elastic modulus and maximum...

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confidence: 99%

Experimental Investigation on High Strain Rate Tensile Behaviors of HTPB Propellant at Low Temperatures

Wang¹,

Hu²,

Guang³

2015

Propellants Explo Pyrotec

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“…It was found that thermal expansion and contraction during the curing and cooling down processes was the most significant factor in the generation of residual stresses [ 6 ]. This involves the first three aforementioned factors, which have been extensively investigated using the finite element method (FEM) due to its significant economy, efficiency and accuracy [ 7 , 8 , 9 ]. However, chemical shrinkage cannot be neglected; the research shows that the residual stresses due to chemical shrinkage may contribute up to 30% of the total residual stresses in composites [ 10 ].…”

Section: Introductionmentioning

confidence: 99%

Numerical Analysis of Curing Residual Stress and Strain in NEPE Propellant Grain

Xie

Zhou

et al. 2023

Polymers

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In order to investigate the formation mechanism of the residual stress and residual strain in a nitrate ester plasticized polyether (NEPE) propellant grain during the curing and cooling process, the temperature, curing degree and stress/strain of the NEPE propellant grain during the curing and cooling process were analyzed via ABAQUS finite element software. The results indicate that there is a temperature gradient in the NEPE propellant grain during curing at 50 °C. The maximum temperature difference is about 5 °C and the maximum temperature is located on the center of propellant grain. At the end of curing, the temperature in the interior of the grain tends to be uniform. The curing degree in the NEPE propellant grain during the curing process has the same trend as temperature. The residual stress/strain of the NEPE propellant grain during the curing and cooling down processes are mainly composed of curing shrinkage stress/strain in the curing process and thermal stress/strain in the cooling down process. The curing shrinkage stress and strain in the curing process account for 19% and 31% of the whole process, respectively. The thermal stress and thermal strain in cooling down process account for 75% and 69% of the whole process, respectively. The thermal stress and thermal strain in the curing process can nearly be ignored. The residual stress and residual strain calculated by the traditional method is larger than that obtained in this paper. The maximum deviation of the residual stress and residual strain are about 8% and 17%, respectively.

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“…For SRMs, safety and integrity evaluation are crucial. While most analyses focus on the impact of temperature loading [10,11], ignition pressurization [12][13][14], and aging effect [15][16][17] on the grain of SRMs, relatively few studies have been conducted on integrity analysis of SRMs based on residual strain, and an evaluation system has not yet been formed.…”

Section: Introductionmentioning

confidence: 99%

Strain Prediction of Grain in Solid Rocket Motor under the Pressure Curing Molding Technology

Zhang,

Wang,

et al. 2023

International Journal of Aerospace Engineering

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The residual strain generated in grains during the propellant manufacturing process can significantly impact the safety and stability of solid rocket motors. Pressure curing molding technology has been employed as an effective approach to mitigate residual strain. This research paper focuses on deriving a strain prediction function for grains based on continuum mechanics, taking into account the influence of pressure curing molding technology. The accuracy of the prediction function is verified through finite element analysis. The results show that the proposed function accurately predicts strain distribution at critical positions within the grains. And the effects of curing pressure and the elastic modulus of the case on residual strain are analysed. Specifically, for a given material of case, an optimal curing pressure is identified that minimizes residual strain in the grains. Moreover, it is observed that materials with lower hoop elastic modulus, such as composites, tend to require lower optimal curing pressures. The outcomes of this study provide valuable guidance for grain shape design and the selection of optimal curing pressure.

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Effect of Cooling Load on the Safety Factor of Propellant Grains

Cited by 12 publications

References 10 publications

Experimental Investigation on High Strain Rate Tensile Behaviors of HTPB Propellant at Low Temperatures

Experimental Investigation on High Strain Rate Tensile Behaviors of HTPB Propellant at Low Temperatures

Numerical Analysis of Curing Residual Stress and Strain in NEPE Propellant Grain

Strain Prediction of Grain in Solid Rocket Motor under the Pressure Curing Molding Technology

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