STICK–SLIP–SEPARATION ANALYSIS AND NON-LINEAR STIFFNESS AND DAMPING CHARACTERIZATION OF FRICTION CONTACTS HAVING VARIABLE NORMAL LOAD

1998 ◽  
Vol 210 (4) ◽  
pp. 461-481 ◽  
Author(s):  
B.D. Yang ◽  
M.L. Chu ◽  
C.H. Menq
Keyword(s):  
Normal Load ◽  
Stick Slip ◽  
Non Linear ◽  
Stiffness And Damping

Prediction of Resonant Response of Shrouded Blades With 3D Shroud Constraint

1998 ◽  
Author(s):  
B. D. Yang ◽  
J. J. Chen ◽  
C. H. Menq
Keyword(s):  
Relative Motion ◽  
Normal Load ◽  
Three Dimensional ◽  
Force Model ◽  
Resonant Response ◽  
Equivalent Stiffness ◽  
Stick Slip ◽  
Contact Plane ◽  
Blade System ◽  
Stiffness And Damping

In this paper, the 3D shroud contact kinematics of a shrouded blade system is studied. The assumed blade motion has three components, namely axial, tangential, and radial components, which result in a three dimensional relative motion across the shroud interface. The resulting relative motion can be decomposed into two components. The first one is on the contact plane and can induce stick-slip friction. The other component is perpendicular to the contact plane and can cause variation of the contact normal load and, in extreme circumstances, separation of the two contacting surfaces. In order to estimate the equivalent stiffness and damping of the shroud contact an approach is proposed. In this approach, the in-plane slip motion is assumed to be elliptical and is decomposed into two linear motions along the principal major and minor axes of the ellipse. A variable normal load friction force model (Yang and Menq, 1996) is then applied separately to each individual linear motion, and the equivalent stiffness and damping of the shroud contact can be approximately estimated. With the estimated stiffness and damping, the developed shroud contact model is applied to the prediction of the resonant response of a shrouded blade system. The effects of two different shroud constraint conditions, namely 2D constraint and 3D constraint, on the resonant response of a shrouded blade system are compared and the results are discussed.

Prediction of Resonant Response of Shrouded Blades With Three-Dimensional Shroud Constraint

1999 ◽  
Vol 121 (3) ◽  
pp. 523-529 ◽  
Author(s):  
B. D. Yang ◽  
J. J. Chen ◽  
C. H. Menq
Keyword(s):  
Relative Motion ◽  
Normal Load ◽  
Three Dimensional ◽  
Force Model ◽  
Resonant Response ◽  
Equivalent Stiffness ◽  
Stick Slip ◽  
Contact Plane ◽  
Blade System ◽  
Stiffness And Damping

In this paper, the three-dimensional shroud contact kinematics of a shrouded blade system is studied. The assumed blade motion has three components, namely axial, tangential, and radial components, which result in a three dimensional relative motion across the shroud interface. The resulting relative motion can be decomposed into two components. The first one is on the contact plane and can induce stick-slip friction. The other component is perpendicular to the contact plane and can cause variation of the contact normal load and, in extreme circumstances, separation of the two contacting surfaces. In order to estimate the equivalent stiffness and damping of the shroud contact an approach is proposed. In this approach, the in-plane slip motion is assumed to be elliptical and is decomposed into two linear motions along the principal major and minor axes of the ellipse. A variable normal load friction force model (Yang and Menq, 1996) is then applied separately to each individual linear motion, and the equivalent stiffness and damping of the shroud contact can be approximately estimated. With the estimated stiffness and damping, the developed shroud contact model is applied to the prediction of the resonant response of a shrouded blade system. The effects of two different shroud constraint conditions, namely two-dimensional constraint and three-dimensional constraint, on the resonant response of a shrouded blade system are compared and the results are discussed.

Modeling of Friction Contact and Its Application to the Design of Shroud Contact

1997 ◽  
Vol 119 (4) ◽  
pp. 958-963 ◽  
Author(s):  
B.-D. Yang ◽  
C.-H. Menq
Keyword(s):  
Friction Force ◽  
Normal Load ◽  
Harmonic Balance Method ◽  
Forced Response ◽  
Effective Stiffness ◽  
Force Model ◽  
Stick Slip ◽  
Friction Forces ◽  
Friction Joint ◽  
Stiffness And Damping

Designers of aircraft engines frequently employ shrouds in turbine design. In this paper, a variable normal load friction force model is proposed to investigate the influence of shroudlike contact kinematics on the forced response of frictionally constrained turbine blades. Analytical criteria are formulated to predict the transitions between stick, slip, and separation of the interface so as to assess the induced friction forces. When considering cyclic loading, the induced friction forces are combined with the variable normal load so as to determine the effective stiffness and damping of the friction joint over a cycle of motion. The harmonic balance method is then used to impose the effective stiffness and damping of the friction joint on the linear structure. The solution procedure for the nonlinear response of a two-degree-of-freedom oscillator is demonstrated. As an application, this procedure is used to study the coupling effect of two constrained forces, friction force and variable normal load, on the optimization of the shroud contact design.

Non-linear imaging and characterization of atherosclerotic arterial tissue using combined SHG and FLIM microscopy

2015 ◽  
Vol 8 (4) ◽  
pp. 347-356 ◽  
Author(s):  
Riccardo Cicchi ◽  
Enrico Baria ◽  
Christian Matthäus ◽  
Marta Lange ◽  
Annika Lattermann ◽  
...  
Keyword(s):  
Arterial Tissue ◽  
Non Linear

Energy Balancing Method to Identify Nonlinear Damping of Bolted-Joint Interface

2016 ◽  
Vol 693 ◽  
pp. 318-323 ◽  
Author(s):  
Xin Liao ◽  
Jian Run Zhang
Keyword(s):  
Dry Friction ◽  
Harmonic Excitation ◽  
Joint Interface ◽  
Damping Factor ◽  
Viscous Damping ◽  
Bolted Joint ◽  
Energy Balancing ◽  
Stick Slip ◽  
Non Linear ◽  
Linear Damping

The interface of bolted joint commonly focuses on the research of non-linear damping and stiffness, which affect structural response. In the article, the non-linear damping model of bolted-joint interface is built, consisting of viscous damping and Coulomb friction. Energy balancing method is developed to identify the dry-friction parameter and viscous damping factor. The corresponding estimation equations are acquired when the input is harmonic excitation. Then, the vibration experiments with different bolted preloads are conducted, from which amplitudes in various input levels are used to work out the interface parameters. Also, the fitting curves of dry-friction parameters are also obtained. Finally, the results illustrate that the most interface of bolted joint in lower excitation levels occurs stick-slip motion, and the feasibility of the identification approach is demonstrated.

Characteristics in Response Integration and Bifurcation of a Forced Duffing Oscillator

2007 ◽  
Author(s):  
Jang-Der Jeng ◽  
Yuan Kang ◽  
Yeon-Pun Chang ◽  
Shyh-Shyong Shyr
Keyword(s):  
Applied Sciences ◽  
Phase Plane ◽  
Duffing Oscillator ◽  
High Order ◽  
Chaotic Motions ◽  
Integration Algorithm ◽  
High Order Harmonic ◽  
Stiffness And Damping

The Duffing oscillator is well-known models of nonlinear system, with applications in many fields of applied sciences and engineering. In this paper, a response integration algorithm is proposed to analyze high-order harmonic and chaotic motions in this oscillator for modeling rotor excitations. This method numerically integrates the distance between state trajectory and the origin in the phase plane during a specific period and predicted intervals with excitation periods. It provides a quantitative characterization of system responses and can replace the role of the traditional stroboscopic technique (Poincare´ section method) to observe bifurcations and chaos of the nonlinear oscillators. Due to the signal response contamination of system, thus it is difficult to identify the high-order responses of the subharmonic motion because of the sampling points on Poincare´ map too near each other. Even the system responses will be made misjudgments. Combining the capability of precisely identifying period and constructing bifurcation diagrams, the advantages of the proposed response integration method are shown by case studies. Applying this method, the effects of the change in the stiffness and the damping coefficients on the vibration features of a Duffing oscillator are investigated in this paper. From simulation results, it is concluded that the stiffness and damping of the system can effectively suppress chaotic vibration and reduce vibration amplitude.

Towards non-linear inversion for characterization of time-lapse phenomena through numerical modelling

2003 ◽  
Vol 51 (4) ◽  
pp. 285-293 ◽  
Author(s):  
A. Abubakar ◽  
P.M. van den Berg ◽  
J.T. Fokkema
Keyword(s):  
Numerical Modelling ◽  
Time Lapse ◽  
Linear Inversion ◽  
Non Linear
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