DYNAMIC DESIGN ANALYSIS METHOD SHIPBOARD SHOCK USING LSDYNA
DYNAMIC DESIGN ANALYSIS METHOD (SHIPBOARD SHOCK USING LS_DYNA) STEP 1. Modal Analysis and Assessment (LS_DYNA) STEP 2. Coefficient Computational Phase (User VB Code) STEP 3. Response Spectrum Analysis (LS_DYNA) EQUIPMENT TO BE SHOCKED FRONT PANEL REMOVED REAR PANEL REMOVED
LOAD DIRECTIONS AT FEET OF INSTRUMENT BOX Four Loading Scenarios 1. 2. 3. 4. X direction only Y direction only Z direction only Combined XYZ direction Z Y X
DYNAMIC DESIGN ANALYSIS METHOD
Numerical Analysis Numerical Methods - Vibrational Analysis – Response Spectrum Analysis Doing A Response Spectrum Analysis Given Damping Ratio
NB NRL : Naval Research Laboratory
Page 1 of 2 Z Y X NB Data required for User VB Code to calculate the INPUT SPECTRUM came from this document.
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STEP 1. MODEL ANALYSIS AND ASSESSMENT (Modal Frequencies from LS_DYNA) INPUT An LS_DYNA MODAL ANALYSIS keyword FE model OUTPUT The eigout text file and d 3 eigv family of graphic binary files
STEP 1. MODEL ANALYSIS AND ASSESSMENT (Modal Frequencies from LS_DYNA) OUTPUT INPUT
STEP 1. MODEL ANALYSIS AND ASSESSMENT (Modal Effective Mass from LS_DYNA) OUTPUT
STEP 1. MODEL ANALYSIS AND ASSESSMENT (Modal Analysis run time data)
STEP 2. COEFFICIENT COMPUTATION PHASE (Dynamic Design Analysis Method) INPUT Script file “script. txt” defining scenario parameters The “eigout” text file LS_DYNA output file from Step 1. OUTPUT “freq_accel_x. txt, freq_accel_y. txt and freq_accel_z. txt” files containing Significant modes versus acceleration for each direction
STEP 2. COEFFICIENT COMPUTATION PHASE (DDAM Code Visual Basic – Input Files ) Script File (Scenario definition) eigout file (modal frequencies and effective modal masses)
STEP 2. COEFFICIENT COMPUTATION PHASE (DDAM User Visual Basic Code )
STEP 2. COEFFICIENT COMPUTATION PHASE (Significant Effective Modal Mass/Acceleration from User Visual Basic Code- Output) (40 th mode) (43 th mode) NB Using 40 modes X Direction Using 43 modes Y Direction Using 47 modes Z Direction To calculate the INPUT SPECTRUM for Step 3 (Total Effective Mass) (47 th mode) (Total Effective Mass)
STEP 2. COEFFICIENT COMPUTATION PHASE (Modal Mass/Acceleration User Visual Basic Code - Output) 47 th mode 43 th mode 40 th mode
STEP 2. COEFFICIENT COMPUTATION PHASE (Text Files – User Visual Basic Code Output) e. g. (output) 21. 31384, 130. 6188 33. 1474, 203. 1387 37. 27663, 228. 4303 38. 50516, 235. 9657 43. 21374, 264. 8285 54. 61352, 334. 6909 76. 95773, 471. 6232 101. 0269, 619. 1266 112. 7488, 690. 9637
STEP 3. RESPONSE SPECTRUM ANALYSIS (Shock Response Analysis from LS_DYNA) INPUT 1. A LS_DYNA RESPONSE SPECTRUM ANALYSIS keyword FE model 2. The d 3 eigv family of graphic files 3. INPUT SPECTRUM in the form of *DEFINE_CURVE constructed from the freq_accel_x. txt, freq_accel_y. txt and freq_accel_z. txt files OUTPUT 1. A single PEAK acceleration, velocity, displacement and stress for any point on the FE model
STEP 3. RESPONSE SPECTRUM ANALYSIS (Shock Response from LS_DYNA - Input) An estimate of damping NB NRL : Naval Research Laboratory Use existing d 3 eigv family of files from STEP 1. NB 100 modes required to get to the frequency range of 250 Hz INPUT SPECTRUM calculated from the freq_accel_x. txt, y or z text files generated from STEP 2.
STEP 3. RESPONSE SPECTRUM ANALYSIS (Shock Response from LS_DYNA - Output) PEAK VON MISES STRESS (Pa) LOAD DIRECTIONS X LOAD DIRECTIONS Y LOAD DIRECTIONS Z LOAD DIRECTIONS X: Y: Z
STEP 3. RESPONSE SPECTRUM ANALYSIS (Shock Response from LS_DYNA - Output) PEAK X DISPLACEMENT (m) LOAD DIRECTIONS X LOAD DIRECTIONS Y LOAD DIRECTIONS Z LOAD DIRECTIONS X: Y: Z
STEP 3. RESPONSE SPECTRUM ANALYSIS (Shock Response from LS_DYNA - Output) PEAK Y DISPLACEMENT (m) LOAD DIRECTIONS X LOAD DIRECTIONS Y LOAD DIRECTIONS Z LOAD DIRECTIONS X: Y: Z
STEP 3. RESPONSE SPECTRUM ANALYSIS (Shock Response from LS_DYNA - Output) PEAK Z DISPLACEMENT (m) LOAD DIRECTIONS X LOAD DIRECTIONS Y LOAD DIRECTIONS Z LOAD DIRECTIONS X: Y: Z
STEP 3. RESPONSE SPECTRUM ANALYSIS (Shock Response from LS_DYNA - Output) PEAK X ACCELERATION (m/s^2) LOAD DIRECTIONS X LOAD DIRECTIONS Y LOAD DIRECTIONS Z LOAD DIRECTIONS X: Y: Z
STEP 3. RESPONSE SPECTRUM ANALYSIS (Shock Response from LS_DYNA - Output) PEAK Y ACCELERATION (m/s^2) LOAD DIRECTIONS X LOAD DIRECTIONS Y LOAD DIRECTIONS Z LOAD DIRECTIONS X: Y: Z
STEP 3. RESPONSE SPECTRUM ANALYSIS (Shock Response from LS_DYNA - Output) PEAK Z ACCELERATION (m/s^2) LOAD DIRECTIONS X LOAD DIRECTIONS Y LOAD DIRECTIONS Z LOAD DIRECTIONS X: Y: Z
STEP 3. RESPONSE SPECTRUM ANALYSIS (Response Spectrum Analysis run time data)
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