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2	Passive Vibration Suppression Passive vibration suppression Implemented by several technologies Accurate design and analysis methods exist Has been proven in many applications If the problem can be solved passively, it will probably be less expensive and complex than active methods If active methods are required, well-designed passive methods can greatly ease the burden of active systems
3	Overview of the Effects of Passive Damping
4	Damping Terminology
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6	Techniques Used for Passive Damping Viscoelastic Materials (VEM) Polymers Rubbers Pressure sensitive adhesives Urethanes Epoxies Enamels Viscous Fluids Silicone oil Other oils Grease
7	Overview of Several Passive Loss Mechanisms
8	Viscoelastic Material Damping Shearing of viscoelastic material dissipates vibrational energy as heat Viscoelastic materials have low shear modulus but high loss factor Shear modulus 20 to 10,000 psi Loss factor up to 2 or more (Measure of energy dissipation capability) Properties are both temperature and frequency dependent Single treatment can damp relatively wide frequency range
9	Viscoelastic Material Testing at CSA
10	Viscous Devices Typically, these force fluid through a precision orifice or annulus Moderately sensitive to temperature Effective over relatively narrow frequency bandwidths Velocity-dependent damping
11	Passive Magnetic Damping Operating Principle Eddy currents in moving conductor dissipate energy Advantages True linear viscous damping Almost temperature invariant Common, space-qualified materials (no fluids) Large damping constant in compact device Simple, robust construction Good for TMD’s, strut dampers, and isolators
12	Particle Damping Advantages Broad useful temperature ranges Not mode/frequency specific Non-outgassing Variety of loss methods Impact (particle-particle & particle/cavity) Friction (particle-particle & particle/cavity) Caveats Empirical based design Amplitude dependent behavior Behavior is also dependent on cavity orientation to local quasi-static acceleration field Multiple other parameters can influence damping performance
13	Piezoelectrics for Passive Damping Resistor shunted piezoelectrics produce frequency dependent material properties much like VEM’s Resonant shunted piezoelectrics add an extra mode to the system, just like a TMD. However, it counters potential strain energy instead of kinetic energy. Modal strain energy determines optimal location
14	Constrained- and Free-Layer Damping Constrained-Layer Treatment
15	Discrete Damping Devices Tuned-Mass Damper (TMD) High damping for single mode Small weight penalty Resonant motion amplification device Can be retrofit Link, Strut, or Shear Strap Dampers Useful for damping and shifting troublesome modes Small weight penalty Joint or Interface Dampers Small weight penalty Low damping Design issues
16	Passive Damping Design To achieve damping, two conditions must be met: Significant strain energy must be directed into the damping mechanism for the modes of interest Energy in damping mechanism must be dissipated
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18	Vibration Isolation and Damping for the Hubble Space Telescope
19	SoftRide Whole-Spacecraft Vibration Isolation
20	SoftRide Isolation Systems Proven in Flight
21	SUITE: Satellite Ultraquiet Isolation Technology Experiment
22	Summary Passive damping and isolation are very effective, if properly designed Analysis and design tools have been developed and proven Select the proper passive technology to fit the application Use active solutions only when performance improvements warrant an active solution A good passive design should be integrated into all active solutions