a
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a is the viscous damping component and also known as mass damping
Specified only if viscous damping is dominant, such as in underwater applications, shock absorbers, or objects facing wind resistance.
If beta damping is ignored, a can be calculated from a known value of x and a known frequency w: a = 2xw (pick the most dominant response frequency to calculate a).
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b is the hysteresis damping component and also known as stiffness damping.
Inherent property of most materials.
Specified per material (as material property DAMP) or as a single, global value (BETAD).
If alpha damping is ignored , b can be calculated from a known value of x and a known frequency w: b = 2x/w (pick the most dominant response frequency to calculate b).
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To Specify Both a and b Damping
Since there are two unknowns, assume that the sum of a and b damping gives a constant damping ratio x over the frequency range w1 to w2. This gives two equations from which we can solve for a and b.
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