Suggested fix – add a little plastic into the formulation or increasing the stiffness of the components.
I think we will have to leave the rest to the biomedical engineers!
Analysis of squeaking on ceramic hip endoprosthesis using the complex eigenvalue method
A finite element model of the ceramic hip endoprosthesis system is established with ABAQUS 6.7. The generation mechanism of squeaking is studied using the complex eigenvalue method which allows for a stability analysis of the system under friction coupling. Numerical results reveal that a ceramic hip endoprosthesis system has a strong propensity of unstable vibration when the friction coefficient of ceramic bearings reaches to a critical value, which is considered to be the most likely mechanism for squeaking.
In the present study μ = 0.15 is proved to be a critical value, below which there is no instability of the system.
Furthermore, the resonance of the femoral components at a frequency of 3177 Hz is found to be the source of the unstable vibration in squeaking. On the basis of the etiology of squeaking, two methods for suppressing squeaking are proposed.
One method is adding ultra-high molecular weight polyethylene (UHMWPE) damping material in acetabular components, the other is imposing reasonable fixed stiffness on acetabular components.
Simulation results show that both methods are effective for increasing the critical friction coefficient from 0.15 to 0.22 and 0.32, respectively, which improve the stability of the ceramic hip endoprosthesis system to a great extent.
► A finite element model of the ceramic hip endoprosthesis system is established with ABAQUS 6.7. ► We reveal the mechanism of squeaking in ceramic hips with the complex eigenvalue method. ► System is likely to become unstable when the friction coefficient reaches to a critical value. ► The resonance of the femoral components is found to be the source of the squeaking. ► Adding damping and changing fixed stiffness on acetabular components can suppress the squeaking.
Keywords: Ceramic hip endoprosthesis system; Squeaking; Complex eigenvalue extraction; Friction; Self-excited vibration
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