April 7, 2008University of Minnesota PDR Satellite Structure Subsystem Structural and Vibrational Stress Analysis Presented By: Chris Matthews
April 7, 2008University of Minnesota PDR Analysis Overview Structural and Vibrational stress analysis proves design meets mission critical requirements –Isolate, possibly alter weak areas of satellite design Analysis performed using ANSYS Workbench 11.0 at Minnesota Supercomputing Institute –ProE geometric assembly converted to.iges files and imported into ANSYS –Given Help and Suggestions for meshing and analysis from a contact at Honeywell
April 7, 2008University of Minnesota PDR Analysis Priorities Stiffness of the structure critical requirement –>100Hz 1 st Fundamental Frequency is hard requirement Limit Acceleration Load Factors –AFRL decision makes loading omnidirectonal –20g loading results should satisfy 2.0 (yielding) safety factor if stiffness requirement is met Random Vibration and Acoustic Noise –Sine sweep and burst tests give idea for performance during AFRL random vibration test
April 7, 2008University of Minnesota PDR Simplification of Model for Analysis Done with consulting from an engineer at Honeywell Satellite solid model too detailed to mesh –Limited processing power and time Model heavy internal components as “bricks” or simple masses Suppress components that don’t affect the structural integrity –Solar panels, mounting plates, and spacers –Screw threading and indentations –Payload (electronics, sensors, computers)
April 7, 2008University of Minnesota PDR Meshing Conditions ANSYS auto-generates mesh based on input of element sizes –ANSYS picks element geometry type: octahedral (cube) or tetrahedral (pyramid) Specify different element sizes based on complexity of certain aspects of the design –Satellite panels: 0.4 cm –Torque Coils and Mounts: 2.0 cm –Component and Battery Box Bottoms: 0.5 cm –Component and Battery Box Lids: 2.0 cm –Component and Battery Box Sides: 2.0 cm
April 7, 2008University of Minnesota PDR
April 7, 2008University of Minnesota PDR Boundary Conditions Fixed Support: Lightband ring –Bottom Surface (ring) of Satellite doesn’t move –Interior surface of screw holes in ring also fixed
Loading Conditions Static Structural Conditions –20g acceleration loading along principal axes Applied as a body force at the center of gravity Modal Analysis Conditions –Vibrate structure at all frequencies between 0 and 1000 Hz Determines first 3 fundamental frequencies Harmonic Analysis Conditions –Vibrate the structure at 100Hz and at fundamental frequencies Look at stress and deflections caused by vibrations April 7, 2008University of Minnesota PDR Z X Y
Acceleration Load Results Direction:XYZ Load20g Minimum Saftey Factor Maximum Stress (MPa) Maximum Deflection (mm) Meets Requirements?Yes No! April 7, 2008University of Minnesota PDR
April 7, 2008University of Minnesota PDR
April 7, 2008University of Minnesota PDR
April 7, 2008University of Minnesota PDR
April 7, 2008University of Minnesota PDR
April 7, 2008University of Minnesota PDR
April 7, 2008University of Minnesota PDR
April 7, 2008University of Minnesota PDR
April 7, 2008University of Minnesota PDR
April 7, 2008University of Minnesota PDR
April 7, 2008University of Minnesota PDR
April 7, 2008University of Minnesota PDR
April 7, 2008University of Minnesota PDR Modal Analysis (Current Work) Issues with getting the modal analysis to solve –Simulation restarts itself (sign of error) –Tried restricting the analysis Restricting the range of frequency ANSYS sweeps Lowering the number of fundamental frequencies ANSYS tries to solve for Altering the conditions of contact surfaces We know from z-direction 20g loading that top panel will have largest deflection –Stiffen top panel by thickening isogrid bars from 0.4 to 0.6 centimeters
April 7, 2008University of Minnesota PDR Current Work Work (Cont.) Altering the top panel and running the simulations again under same conditions Refining the mesh and solving again –Change element sizes for finer mesh –Results should converge to accurate values Harmonic Analysis –More detailed solution of deflections and stresses caused by a certain frequency or multiple vibration frequencies applied to the structure
April 7, 2008University of Minnesota PDR QUESTIONS???