The relationship between dynamic stiffness and vibratin amplitude

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SUMMARY

The discussion centers on the relationship between dynamic stiffness and vibration amplitude, highlighting that dynamic stiffness decreases as vibration amplitude increases. This phenomenon is supported by experimental results and can be explained using the formula F=kX, where F is force, k is dynamic stiffness, and X is displacement. As displacement increases under a constant force, dynamic stiffness (k) must decrease. The conversation emphasizes the need for a theoretical explanation of why dynamic stiffness diminishes at higher amplitudes during dynamic testing.

PREREQUISITES
  • Understanding of dynamic stiffness and its calculation
  • Familiarity with the relationship between force, displacement, and stiffness
  • Knowledge of material properties and their testing methods
  • Basic principles of vibration analysis
NEXT STEPS
  • Research the mathematical derivation of dynamic stiffness in relation to amplitude
  • Explore the effects of material properties on dynamic stiffness
  • Study experimental methods for measuring force and displacement in dynamic tests
  • Investigate the implications of varying stiffness in engineering applications
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Mechanical engineers, materials scientists, and researchers involved in vibration analysis and dynamic testing will benefit from this discussion.

joannall
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many references tell that the dynamic stiffness will reduce when vibration amplitude increases. And the experimental result is just so. But why there is such rule?who can explain it theoretically?
 
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Are you assuming a constant force input? Think of F=kX over a broad range of frequencies, with k being your dynamic stiffness. if X increases with a constant F, the k has to decrease. Or maybe you are thinking of something different?
 
i think we should know which is the reason and which is the result. K is the property of materials or components, we can get it by testing force and displacement. of course, the force can't be constant in the experiment. that's to say, the force will increase with the increase of displacement, but their increasing rate are different. so K is different.but i can't explain why K get smaller at higher amplitude in dynamic test.

who can explain such phenomenon theoretically?
 

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