Friction-Induced Squeak of Ceramic-on-Ceramic Hip Implants: A Stability Design Criteria

2012 ◽  
Author(s):  
Mark Sidebottom ◽  
Manish Paliwal
Keyword(s):  
Computer Aided Design ◽  
Acoustic Analysis ◽  
Femoral Stem ◽  
Coupled System ◽  
Stick Slip ◽  
Audio Data ◽  
Mathematical Analyses ◽  
The Stability ◽  
Parametric Analyses ◽  
Ceramic On Ceramic

Friction-induced squeaking has been reported in 1–10% of patients who have a ceramic on ceramic total hip replacement, which is a subject of annoyance. The goal of this study was to investigate the possible factors attributing to the hip squeak, and understand the underlying phenomenon. The investigation involved acoustic, modal, and mathematical analyses. Acoustic analysis involved extracting and analyzing audio data from the videos files of squeaking ceramic hips. The audio data was transformed from the time to frequency domain using Fast Frequency Transform (FFT) using MATLAB. This allowed the identification of the squeal frequencies. Modeling involved 3-D rendering of the hip implant (femoral stem, head, cup liner, and the cup shell) using computer-aided-design software. Mathematical analysis involved the investigation of the role of the frictional stick-slip phenomenon of the metal shell and ceramic liner on squeal using a 2-DOF mathematical model. Mass, stiffness properties, and coefficient of friction of the components were incorporated to study the limit cycle using MATLAB/Simulink, which is an indicator of the stability of the system. Modal (Numerical) analysis involved the evaluation of the modal frequencies of the components using ANSYS, to investigate their contribution to squeal. Acoustic analysis of the squeal frequencies showed that the range of squeal frequencies of the coupled system ranged from 1500–3000 Hz, which concurred well with the literature. Modal Analysis showed the metallic shell’s resonant frequency at 4600 Hz. The parametric analyses using the 2-dof model showed that a stable system was approached as the stiffness of the liner was increased. The increase in mass of the shell resulted in larger limit-cycles. Increased stiffness of the shell proved to stabilize the system for most loading conditions.

scholarly journals A Theoretical Model for the Transmission Dynamics of the Buruli Ulcer with Saturated Treatment

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Ebenezer Bonyah ◽  
Isaac Dontwi ◽  
Farai Nyabadza
Keyword(s):  
Human Population ◽  
Reproduction Number ◽  
Buruli Ulcer ◽  
Coupled System ◽  
Model Parameters ◽  
The Public ◽  
Treatment Function ◽  
Medical Facilities ◽  
The Stability ◽  
Saturated Treatment

The management of the Buruli ulcer (BU) in Africa is often accompanied by limited resources, delays in treatment, and macilent capacity in medical facilities. These challenges limit the number of infected individuals that access medical facilities. While most of the mathematical models with treatment assume a treatment function proportional to the number of infected individuals, in settings with such limitations, this assumption may not be valid. To capture these challenges, a mathematical model of the Buruli ulcer with a saturated treatment function is developed and studied. The model is a coupled system of two submodels for the human population and the environment. We examine the stability of the submodels and carry out numerical simulations. The model analysis is carried out in terms of the reproduction number of the submodel of environmental dynamics. The dynamics of the human population submodel, are found to occur at the steady states of the submodel of environmental dynamics. Sensitivity analysis is carried out on the model parameters and it is observed that the BU epidemic is driven by the dynamics of the environment. The model suggests that more effort should be focused on environmental management. The paper is concluded by discussing the public implications of the results.

Friction Induced Vibrations in Aircraft Disk Brakes

1997 ◽  
Author(s):  
Lisle B. Hagler ◽  
Per G. Reinhall
Keyword(s):  
Friction Coefficient ◽  
Multiple Scales ◽  
Primary Resonance ◽  
Rotational Model ◽  
Stick Slip ◽  
Numeric Simulation ◽  
Constant Friction ◽  
The Stability ◽  
Rotor Stiffness ◽  
Friction Induced Vibration

Abstract This paper presents a detailed analysis of the dynamic behavior of a single rotor/stator brake system. Two separate mathematical models of the brake are considered. First, a non-rotational model is constructed with the purpose of showing that friction induced vibration can occur in the stator without assuming stick-slip behavior and a velocity dependent friction coefficient. Self-induced vibrations are analyzed via the application of the method of multiple scales. The stability boundaries of the primary resonance, as well as the super-harmonics and sub-harmonics are determined. Secondly, rotational effects are investigated by considering a mathematical brake model consisting of a spinning rotor engaging against a flexible stator. Again, a constant friction coefficient is assumed. The stability of steady whirl is determined as a function of the system parameters. We demonstrate that only forward whirl is stable for no-slip motion of the rotor. The interactions between chatter, squeal, and rotor whirl are investigated through numeric simulation. It is shown that rotor whirl can be an important source of the torsional oscillations (squeal) of the stator and that the settling time to no-slip decreases as the ratio of the stator to rotor stiffness is increased.

Resistive Ballooning Modes in Three-Dimensional Configurations

1982 ◽  
Vol 37 (8) ◽  
pp. 848-858 ◽  
Author(s):  
D. Correa-Restrepo
Keyword(s):  
Growth Rates ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Coupled System ◽  
Small Constant ◽  
Ballooning Mode ◽  
The Stability ◽  
The Magnetic Field ◽  
Symmetric Systems ◽  
The Ideal

Resistive ballooning modes in general three-dimensional configurations are studied on the basis of the equations of motion of resistive MHD. Assuming small, constant resistivity and perturbations localized transversally to the magnetic field, a stability criterion is derived in the form of a coupled system of two second-order differential equations. This criterion contains several limiting cases, in particular the ideal ballooning mode criterion and criteria for the stability of symmetric systems. Assuming small growth rates, analytical results are derived by multiple-length-scale expansion techniques. Instabilities are found, their growth rates scaling as fractional powers of the resistivity

Thermal Instability of Sliding and Oscillations Due to Frictional Heating Effect

1988 ◽  
Vol 110 (1) ◽  
pp. 69-72 ◽  
Author(s):  
I. L. Maksimov
Keyword(s):  
Thermal Instability ◽  
Initial Conditions ◽  
Frictional Heating ◽  
Interface Temperature ◽  
Heating Effect ◽  
Stick Slip ◽  
Instability Development ◽  
The Stability ◽  
Sliding Dynamics ◽  
Sliding Instability

The stability of sliding has been studied, taking into account frictional heating effect and friction coefficient dependence upon the interface temperature and sliding velocity. The collective—thermal and mechanical—sliding instability has been found to exist; instability emergence conditions and dynamics (both in linear and nonlinear stages) have been determined. It is shown that both the threshold and the dynamics of thermofrictional instability differ qualitatively from the analogous characteristics of “stick-slip” phenomenon. Namely, the oscillational instability behavior due to the energy exchange between thermal and mechanical modes has been found to occur under certain initial conditions; the velocities range has been determined for which collective sliding instability may occur whereas the stick-slips would be not possible. The nonlinear analysis of instability evolution has been carried out for pairs with the negative thermal-frictional sliding characteristics, the final stage of sliding dynamics has been described. It is found that stable thermofrictional oscillations can occur on the nonlinear stage of sliding instability development; the oscillations frequency and amplitude have been determined. The possibility has been discussed of the experimental observation of new dynamical sliding phenomena at low temperatures.

Research on INS-Aided GNSS Carrier Tracking Loop in High Dynamic Circumstance

2013 ◽  
Vol 464 ◽  
pp. 215-221
Author(s):  
Xin Long Wang ◽  
Chuan Jun Li ◽  
Xing Cheng Li
Keyword(s):  
Dynamic Environment ◽  
Coupled System ◽  
Tracking Performance ◽  
Tracking Loop ◽  
Loop Control ◽  
Closed Loop Control System ◽  
Loop Control System ◽  
Tightly Coupled ◽  
High Dynamic ◽  
The Stability

GNSS receiver will produce a large Doppler shift in high dynamic environment, thus causing lock-lose of the tracking loop. INS-aided GNSS tightly coupled system can improve tracking performance in high dynamic environment by introducing the Doppler information estimated by INS. Through analyzing by the theory of closed loop control system theory and numerical simulation of the INS-aided carrier tracking loop, the results show that INS-aided carrier tracking loop can obviously improve the stability of carrier tracking performance and anti-jamming ability of the satellite navigation receiver in high dynamic circumstance.

scholarly journals Vibro-acoustic analysis of a trapezoidal cavity with a clamped flexible wall

2018 ◽  
Vol 37 (4) ◽  
pp. 801-815 ◽  
Author(s):  
Yuan Wang ◽  
Jianrun Zhang ◽  
Xinzhou Zhang ◽  
Bo Wu
Keyword(s):  
Acoustic Analysis ◽  
Coupled Model ◽  
Coupled System ◽  
Coupling Theory ◽  
Incident Plane ◽  
Resonance Frequencies ◽  
Modal Coupling ◽  
Cavity Coupling ◽  
Flexible Wall ◽  
Matching Degree

The coupled model between trapezoidal cavity and its clamped flexible wall is developed using classical modal coupling theory. Based on the coupled model, the resonance frequencies of coupled system are obtained and compared with the corresponding uncoupled one. Meanwhile, the reason for the variation of resonance frequencies of coupled system modes is analyzed in detail. Then, the response of coupled system is investigated using the acoustic potential energy in the cavity and panel vibration kinetic energy when it is excited by an incident plane wave outside of the cavity. Coupling coefficient between trapezoidal cavity and its clamped flexible wall is proposed to assess the modal matching degree between them. It is shown that the coupling selection is not satisfied except in the axis direction which is parallel to the inclined wall. In addition, a rectangular cavity with a clamped flexible wall is also considered and compared with that of the trapezoidal one.

scholarly journals Stability of PDF Controller With Stick-Slip Friction Device

1997 ◽  
Vol 119 (3) ◽  
pp. 486-490 ◽  
Author(s):  
Jia-Yush Yen ◽  
Chih-Jung Huang ◽  
Shu-Shung Lu
Keyword(s):  
Control Algorithm ◽  
Controller Design ◽  
System Model ◽  
Pole Placement ◽  
Order System ◽  
Stick Slip ◽  
Precision Control ◽  
Experimental Works ◽  
The Stability ◽  
Control Accuracy

This paper presents the precision control of drive devices with significant stick-slip friction. The controller design follows the Pseudo-Derivative Feedback (PDF) control algorithm. Using the second order system model, the PDF controller offers arbitrary pole placement. In this paper, the stability proof for the controller with stick-slip friction is presented. On the basis of this proof, the stability criteria are derived. The paper also includes both the computer simulation and the experimental works to confirm the theoretical result. The experiments conducted on a Traction Type Drive Device (TTDD) shows that control accuracy of as high as ±1 arc – second is achieved.

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