Papers by Huajiang Ouyang
A receptance-based method for predicting latent roots and critical points in friction-induced vibration problems of asymmetric systems
Journal of Sound and Vibration, Apr 1, 2009
This paper studies the latent roots and critical points of friction-induced vibration problems in... more This paper studies the latent roots and critical points of friction-induced vibration problems in which the stiffness matrix is asymmetric. The asymmetric terms are represented by a parameter or parameters related to the friction coefficient. As the parameter value increases, some latent roots of the asymmetric system change, and even become complex with positive real parts at a critical point, indicating flutter instability. A method is put forward for computing the latent roots and predicting the critical value of this parameter at the flutter instability boundary of the asymmetric system based on the receptance of the symmetric system. When measured receptances of the symmetric system (at those locations where friction forces would be acting in the corresponding asymmetric system) are available, the simulated numerical example shows that this method is efficient.
Discrete mass and stiffness modifications for the inverse eigenstructure assignment in vibrating systems: Theory and experimental validation
International Journal of Mechanical Sciences, Nov 1, 2012
ABSTRACT The inverse eigenstructure assignment in structural dynamics and control aims at determi... more ABSTRACT The inverse eigenstructure assignment in structural dynamics and control aims at determining the mass and stiffness parameters to ensure the desired dynamic behavior expressed in terms of the prescribed eigenstructure. Several methods have been developed for the solution of this problem in the past. However, in the techniques proposed so far, all the design variables are assumed to be continuous. In practice, some design variables can only be changed through discrete modifications since either standard mass modules or springs are available. The determination of the discrete optimal solution of the structural modification problem cannot be performed by simply rounding the continuous optimal solution to the “nearest” integer, since rounded solutions can be considerably far from the optimality. On the other hand, the total enumeration as a solution method is infeasible for medium and large scale problems. To overcome this limitation, in this work, the eigenstructure assignment is formulated firstly as an inverse eigenvalue problem within the frame of constrained nonlinear integer programming, and then is solved by means of a partial enumeration technique with a reduced number of iterations. The experimental validation of the method on a five-degree-of-freedom lumped-parameter rig demonstrates its capability to compute effective modifications meeting the prescribed requirements and satisfying all the constraints.
Pole assignment for control of flexible link mechanisms
Journal of Sound and Vibration, Jun 1, 2013
ABSTRACT Although the dynamics of flexible link mechanisms and manipulators is nonlinear, motion ... more ABSTRACT Although the dynamics of flexible link mechanisms and manipulators is nonlinear, motion and vibration control often relies on linear or piecewise-linear controllers based on linearized models in order to ensure real-time implementability. Keeping such an objective in mind, this paper proposes a general receptance-based method for pole assignment in flexible link mechanisms with a single rigid-body degree of freedom (dof) using a single control force (i.e. rank-one control). A chief advantage of the approach proposed is that it makes use of the second-order system model representation through the receptance matrix of the symmetric part of the asymmetric model. The asymmetric terms in the stiffness and damping matrices arise from the coupling between rigid-body motion and elastic motion. The proposed receptance-based formulation ensures numerical reliability and efficiency also for large dimensional and ill-conditioned system models originating from the simultaneous presence of high-frequency and weakly controllable oscillating modes, and of rigid-body motion low-frequency dynamics, which may also be unstable. The validation of the proposed technique is carried out by performing pole assignment through position and velocity feedback or acceleration and velocity feedback on a mechanism. Integral control is also introduced to improve the steady state system response. Numerical results indicate that the proposed method is more accurate and robust than two popular established methods.
Dynamic Instabilities and Spinning Discs
Dynamics of a moving oscillator and a truss structure considering separation and reattachment with impact
ABSTRACT The dynamic response of a stationary truss structure made of Timoshenko beams excited by... more ABSTRACT The dynamic response of a stationary truss structure made of Timoshenko beams excited by a moving oscillator is studied in this paper. The frequencies and modes of the truss are first obtained by the finite element method and then the modes are cast in an analytical form within each element through the element shape functions. Each component beam of the stationary structure is meshed with an adaptable number of Timoshenko beam elements. During its horizontal travel and vertical vibration, the oscillator may separate from the vibrating truss and subsequently may reattach to it with impact. Both separation and reattachment with impact are studied. It is found through simulated examples that they produce a noticeable difference in the dynamic response and multiple separation and impact events are possible at high speeds.
A railway track dynamics model based on modal substructuring and a cyclic boundary condition
Journal of Sound and Vibration, 2011
This article presents a technique for modelling the coupled dynamics of a railway vehicle and the... more This article presents a technique for modelling the coupled dynamics of a railway vehicle and the track. The method is especially useful for simulating the dynamics of high speed trains running on nonlinear tracks. The main hypothesis is a cyclic system: an infinite track on which there is an infinite set of identical vehicles spaced at a regular interval of distance. Thus the main problems of the finite-length track models (e.g. the waves that reflect at the end of the track and interact with the vehicle; and the time interval of integration must be shorter than the track length divided by the velocity) are avoided. The flexibility of the method can be observed from the case studies presented in the present work: a vehicle passing over a hanging sleeper, and the vehicle–track dynamics for different ballast compaction cases. The results show the influence of the hanging sleeper gap on the wheel–rail contact forces, and the bending moment at the sleeper for different ballast compaction cases.
Nonlinear Dynamics, 2020
The friction-induced vibration of a novel 5-DoF (degree-of-freedom) mass-on-oscillating-belt mode... more The friction-induced vibration of a novel 5-DoF (degree-of-freedom) mass-on-oscillating-belt model considering multiple types of nonlinearities is studied. The first type of nonlinearity in the system is the nonlinear contact stiffness, the second is the non-smooth behaviour including stick, slip and separation, and the third is the geometrical nonlinearity brought about by the moving-load feature of the mass slider on the rigid belt. Both the linear stability of the system and the nonlinear steady-state responses are investigated, and rich dynamic behaviours of the system are revealed. The results of numerical study indicate the necessity of the transient dynamic analysis in the study of friction-induced-vibration problems as the linear stability analysis fails to detect the occurrence of self-excited vibration when two stable solutions coexist in the system. The bifurcation behaviour of the steady-state responses of the system versus some parameters is determined. Additionally, th...
Journal of Vibration and Acoustics, 2016
A mass–spring–damper slider excited into vibration in a plane by a moving rigid belt through fric... more A mass–spring–damper slider excited into vibration in a plane by a moving rigid belt through friction is a major paradigm of friction-induced vibration. This paradigm has two aspects that can be improved: (1) the contact stiffness at the slider–belt interface is often assumed to be linear and (2) this contact is usually assumed to be maintained during vibration (even when the vibration becomes unbounded at certain conditions). In this paper, a cubic contact spring is included; loss of contact (separation) at the slider–belt interface is allowed and importantly reattachment of the slider to the belt after separation is also considered. These two features make a more realistic model of friction-induced vibration and are shown to lead to very rich dynamic behavior even though a simple Coulomb friction law is used. Both complex eigenvalue analyses of the linearized system and transient analysis of the full nonlinear system are conducted. Eigenvalue analysis indicates that the nonlinear ...
Complex eugenvalue analysis and dynamic transient analysis in predicting disc brake squeal
Dynamics of a moving oscillator and a truss structure considering separation and reattachment with impact
The dynamic response of a stationary truss structure made of Timoshenko beams excited by a moving... more The dynamic response of a stationary truss structure made of Timoshenko beams excited by a moving oscillator is studied in this paper. The frequencies and modes of the truss are first obtained by the finite element method and then the modes are cast in an analytical form within each element through the element shape functions. Each component beam of the stationary structure is meshed with an adaptable number of Timoshenko beam elements. During its horizontal travel and vertical vibration, the oscillator may separate from the vibrating truss and subsequently may reattach to it with impact. Both separation and reattachment with impact are studied. It is found through simulated examples that they produce a noticeable difference in the dynamic response and multiple separation and impact events are possible at high speeds.
Separation between a beam with multiple elastic supports and a moving two-axle system
Dynamic Instabilities in Spinning Disks
World Scientific Series on Nonlinear Science Series A, 2000
Wear and Contact Simulation and Disc Brake Squeal
In the past, wear at the disc and pads interface of disc brakes has rarely been accounted for in ... more In the past, wear at the disc and pads interface of disc brakes has rarely been accounted for in a 3-dimensional finite element (FE) model for studying brake squeal. Thus, its effect on disc brake squeal is only possible to investigate through experimental methods. In the present paper, wear over time at the pads interface is simulated using a modified wear rate formula. Confirmation of the proposed wear formula is made against experimental results. The surface topographies of two brand new pairs of brake pads are measured. The contact tests using pressure-indicating films are carried out in order to capture static pressure distributions. The same brake pads are tested under several braking applications. For each braking application, the static contact pressure distribution is measured. The results are used to compare with the simulated results predicted by the FE model. To do so, the detailed 3- dimensional finite element model of a real disc brake is developed and validated throug...
Experimental and Analytical Study of the Hysteretic Behaviour of Bolted Joints
Volume 2, 2004
This paper presents the experimental results of a single joint rig subjected to torsional excitat... more This paper presents the experimental results of a single joint rig subjected to torsional excitation and the analytical models for representing the experimental results. A bolted joint connecting two beams is shaken at the resonant frequency and the time-domain data and the resultant hysteresis loops of the torque versus the relative angular displacement of the joint are obtained. Damping behaviour evolving from linear viscous type to nonlinear friction type is clearly seen. Both the Jenkins element model and the Bouc-Wen model are used to fit with the hysteresis loops of the experimental results. The capability of the two models in representing experimental hysteresis loops is discussed.
Moving loads and car disc brake squeal
Noise Notes, 2004
Dynamics of multi-span continuous plate structures traversed by moving loads considering separation and reattachment
Modal Approach for Forced Vibration of Beams with a Breathing Crack
Key Engineering Materials, 2009
This paper presents a method for the vibration of a beam with a breathing crack under harmonic ex... more This paper presents a method for the vibration of a beam with a breathing crack under harmonic excitation. The infinitely thin crack is characterised by a parameter that takes into account the shape and the depth of the crack. The closed- and open-crack states are both modelled by a modal approach: two sets of equations of motion cast in the modal coordinates of their individual mode shapes. The state change (from closed to open or vice versa) involves the calculation of the modal coordinates associated with the new state from the modal coordinates of the previous state. By imposing the continuity of displacement and velocity the beam at the instant of the state change, the matrix that transforms the modal coordinates from one state to the other is determined and proved to be the Modal Scale Factor matrix. This analytical approach takes advantage of exact nature and mathematical convenience of beam modes and is time-efficient. Forced vibration at various values of crack parameter is...
Delayed-reference anti-swing control of overhead crane systems
ABSTRACT This paper presents a non-time based control strategy for the simultaneous path-tracking... more ABSTRACT This paper presents a non-time based control strategy for the simultaneous path-tracking and swing control of overhead crane systems. The model of the system has four degrees of freedom (dofs): two dofs describe the crane motion, while a two-dof swing angle is associated to the suspended load motion. The basic idea behind the suggested control scheme, named delayed reference control (DRC), is to make the path reference of the crane a function of the difference between the time and a variable which plays the role of a time delay. This latter, which is affected by the measured oscillation, is properly calculated on- the-fly in order to reduce the swing phenomenon. The fundamental difference between the proposed scheme and the traditional ones is that it allows exerting the oscillation control while ensuring an accurate tracking of the desired path through space and the coordinated motion of the crane dofs. A significant advantage of the DRC scheme is its ease of implementation. As a matter of fact it can be employed by simply adding an outer loop to standard crane position controllers, as long as they ensure high dynamic response. The effectiveness of the proposed control scheme is demonstrated through numerical results.
Brake Squeal: Complex Eigenvalue versus Dynamic Transient Analysis
SAE Technical Paper Series, 2007
Engineering technical paper: Brake Squeal: Complex Eigenvalue versus Dynamic Transient Analysis.
Finite element analysis of wear and its effect on squeal generation
Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2008
In the past, wear at the pad interface of disc brakes has rarely been accounted for in studies of... more In the past, wear at the pad interface of disc brakes has rarely been accounted for in studies of brake squeal using the finite element method, and its effect on disc brake squeal has been investigated largely through experimental methods. In the present paper, wear taking place at this interface over time is simulated using a modified wear rate formula. The surface topographies of two new and unworn pairs of brake pads are measured. The same brake pads are tested under braking applications of three time durations. For each braking application, the static contact pressure distribution is measured using pressure-indicating film. The results are used to compare with the simulated results predicted by the three-dimensional finite element model of a real disc brake. The paper also investigates squeal generation due to the above braking applications using complex eigenvalue analysis that is available in a commercial software package. It is found that the predicted unstable frequency is v...
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Papers by Huajiang Ouyang