# Need help for easy modal analysis of a beam!

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 July 13, 2010, 16:57 Need help for easy modal analysis of a beam! #1 New Member   yo Join Date: May 2010 Posts: 1 Rep Power: 0 Hi, Johan, french student based at TORONTO for a internship. I want to have the free vibration of a beam... So it seems easy! I have a big mistake with any results given by ansys but I dont know what wrong in my input: system: beam damped damped element type: beam3 real constant: AREA =1 IZZ=1/12 HEIGHT=1 Material model: DENS=8E-6 EX=1E7 PRXY=0 Section: centroid B=1 H=1 Modeling: line from (0.0.0) to (10.0.0) Loads displacement on keypoints (0.0.0) and (10.0.0) Meshing with 100 nodes.. Results: ***** INDEX OF DATA SETS ON RESULTS FILE ***** SET TIME/FREQ LOAD STEP SUBSTEP CUMULATIVE 1 11434. 2 31088. 3 55904. 4 59692. Using Brick model with the same geometry I have the same transverse results: ***** INDEX OF DATA SETS ON RESULTS FILE ***** SET TIME/FREQ LOAD STEP SUBSTEP CUMULATIVE 1 10925. "2 10925." 3 28372. "4 28372." "5 36566." 6 51930. So to analyze the result I undimension the frequency thank to the formula: (big_omega)^2=rho*A0/(E0*IZ0)*L0^4 *omega^2 with big_omega the free frequencies undimensioned here I use rho=8E-6 A0=1 E=1E+7 IZ0=1/12 L0=10 And I should also find the famous result: big_omega1=22.39 big_omega1=61.67... and not big_omega1=3.542 big_omega1=9.63.... So I really dont understand and I'm lock for 3days now and nobody can help me! Thanks for all Ps: ANSYS 12.0 used....

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