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STRUCTURAL ANALYSIS OF SOUNDING ROCKET FINS
Presenter: Aris Iturbe Hernándeza Daniel Alejandro Hernández Záratea, José Luis Xancopinca Trejoa, David Cisneros Gonzáleza, Sergio Raúl Rojasa, Gerardo Saucedo Zárateb aUniversidad Aeronáutica en Querétaro, Colón, Querétaro C.P , México bINMUE A.C President Contact:
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INTRODUCTION - Many problems could cause a sounding rocket breakage
INTRODUCTION - Many problems could cause a sounding rocket breakage. - One of them is the possible failure of their structural components Analysis of the bending-torsion flutter in sounding rocket fins a) b) Lenght 6 m Empty Weight 51 kg Total Weight (loaded) 115 kg Thurst > 4000 Nf Time propulsion 28 seg. Max. Speed km Max Height 70-90 km Range 24 km (86 degrees) Supersonic parachute 95 km/hr waterland SPECIFIC OBJECTIVES Determine the flutter velocity. Simulation of rocket trajectory. Determine a safe operating range rocket. Calculate the critical relation that may permit a systematic separation of safe and unsafe fins. Determine the natural frequency response of the fin subjected to bi-directional vibratory movement. Obtain a numerical model to simulate de natural frequency response of the fin subjected to bi-directional vibratory movement. Fig. 1 a) Sounding Rocket JFCR-200A, INMUE A.C, Sounding Rocket JFCR-200A characteristics INMUE-UNAQ
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METHODOLOGY Bending-Torsion Criterion End Start
Mission simulation (Obtain max. rocket velocity) Design plans JFCR 2000A Flight Data sheet Geometric Parameters Definition Flutter velocity calculation Comparative between rocket velocity and flutter velocity Is abs( Vrocket- Vflutter) > 0 Yes No Determine the biggest positive difference of abs( Vrocket- Vflutter ) Is it possible to modify the geometry? Change of material to augment flutter velocity of the biggest difference Change geometric parameters to augment flutter velocity of biggest difference Generate design plans and CAD figures of modified fin Modal analysis with laser vibrometer Modal analysis with numerical software (FEM) Generate analysis report End METHODOLOGY Bending-Torsion Criterion This allows us to determine the fins performance in a rocket. Leaving this study as a first step aero-elastic analysis. Diagram presents the a methodology for rocket fins analysis under dynamic and static conditions.
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BENDING-TORSION CRITERION
Considering: Static pressure = Stagnation Pressure 1. Material can not be changed ---> Geometry can be changed 𝑉𝑓 a 2 < 3.77x ∗ 𝑃 P0 ∗ 𝛌+1 2 2. Material can be changed ---> Geometry can not be changed 𝑉𝑓 a 2 < 5x x106 3. Parameters can not be changed 𝑉𝑓 a 2 < 3.77x ∗ 𝑃 P0 ∗0.9564 Based on the TN 4197 NACA Report
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DESIGN PLANS MODELS MISSION SIMULATION JFCR 2000A DATA SHEET
Fig. 3 Variables evolution during rocket´s mission Fig. 2 Design plans of the fin Rocket velocity at different altitudes JFCR 2000A DATA SHEET Designed following Normative: ECSS-E-ST-10-02C
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MODELS FLUTTER VELOCITY CALCULATION GEOMETRIC PARAMETERS DEFINITION
Theoretical: Safe climb operational range on NACA TN 4197 report Root Chord 21 in Tip Chord 12 in Semispan 9 in Root thickness 3/8 in Tip Thickness 1/4 in Taper Ratio 0.899 [1] Panel Aspect Ratio 0.55 [1] Table 1. Fin geometric characteristics Root Chord Tip Chord Semispan 𝑉𝑓𝑙=𝑎∗ 𝐺 𝐴 𝑡 𝑐 3 ∗ 𝐴+2 )(( 𝜆+1 2 ))( 𝑝 𝑝 𝑜 𝐆 Shear Modulos. 𝐀 Panel Aspect Ratio 𝐭 Thickness 𝐜 Root Chord 𝛌 Taper ratio 𝐩 Pressure at a given altitude 𝐩 𝐨 Standard Pressure 𝐚 Speed of sound at a given altitude 𝐕𝐟𝐥 Speed in which flutter may occur for a given state of the rocket Symbols for flutter speed equation. Fig. 4 Principal Geometric Parameters
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MODAL ANALYSIS WITH LASER VIBROMETER
MODELS-RESULTS MODAL ANALYSIS WITH LASER VIBROMETER Fin´s material: Aluminum 6061 T6 Excellent joining characteristics, good acceptance of applied coatings. Combines relatively high strength, good workability, and high resistance to corrosion; widely available Figura 7. Experimental Setup. Natural Frequency Hertz I 145 II 298 III 456 IV 713 Table 2. Experimental model solution Figura 6. Rocket fin with reflectors and accelerometer Fig. 5 Aluminum 6061-T6 mechanical properties
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MODAL ANALYSIS WITH NUMERICAL SOFTWARE (FEM)
MODELS- RESULTS MODAL ANALYSIS WITH NUMERICAL SOFTWARE (FEM) Table 3. FEM Model Solution Frequency [Hz] Modes number Figure 8. Total Deformation evolution
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CONCLUSION X Aluminum 6061-T6
Shear Modulus psi 1.04 3.7e6 From contrast the numerical and experimental values. The critical mode to cause failure is: 3, 713 [Hz] From current values for X and material: Aluminum 6061-T6 is recommended to use different material, options: titanium alloy but low density, composites materials, X Mode Natural Frequency Experimental FEM % Error I 145 182 25 II 298 276 7 III 456 487 6.8 IV 713 767 7.5 𝑋= 𝐴 𝑡 𝑐 3 ∗ 𝐴+2
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New material consideration (higher shear modulus)
FUTURE WORK Adapt the numerical model to experimental model with mesh adapting and constrains. New material consideration (higher shear modulus) Classify vibrating rocket components and estimate their frequency Simulation of the aerodynamically forces over the fin corrected with presented methodology
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THANK YOU
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BACK UP To Prevent fluttering are several ways, one of them is
Decouple the movement of bending and twisting Modifying the distribution of mass to move the center of gravity close to the center of rotation
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