47 research outputs found
Development of microslip friction models and forced response prediction methods for frictionally constrained turbine blades
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Nonlinear Free Vibration of Curved Double Walled Carbon Nanotubes Using Differential Quadrature Method
No full textNonlinear Transverse Vibrations of a Beam with Multiple Breathing Edge Cracks
No full textOne step beyond the studies of transverse vibration of beams with a breathing edge crack is the verification of the theoretical crack beam models with an experimental test set up. Beams with a single breathing edge crack can be used as a specimen for the experimental test. However, there is no assurance against the unexpected additional cracks in the specimens, whichmay cause unexpected results. Therefore, in this paper nonlinear transverse vibration of a beam with multiple breathing edge cracks is considered as a preliminary study. The breathing effect of the cracks are modeled as piecewise linear stiffness and a harmonic force is applied to the cracked beam. Galerkin'sMethod is applied with multiple trial functions and nonlinear differential equations obtained are solved by using harmonic balance method with multi harmonics. Utilizing the developed model, effects of crack parameters and crack locations are studied
Nonlinear Vibrations of a Flexible L-shaped Beam Using Differential Quadrature Method
No full textFlexible L-shaped beams are integrated sub-components of several navy and space structures where overall response of the system is affected by these structures. Hence, an understanding of the dynamical properties of these structural systems is required for their design and control. Recent studies show that the dynamic response of beam like structures undergoing large deformation is nonlinear in nature where phenomenon such as jump and chaotic response can be detected. In this study, nonlinear free vibrations of L-shaped beams are studied using a continuous beam model with a focus on the internal resonance of these structures. Nonlinearity considered is due to large deflection of the beams (geometric nonlinearity). Hamilton principle and Euler Bernoulli beam theory are used to obtain the nonlinear equations of motion. The differential quadrature method (DQM) is utilized to discretize the partial differential equations of motion in spatial domain, which resulted in a nonlinear set of ordinary differential equations of motion in time domain. Harmonic balance method is used to convert the ordinary differential equations of motion into a set of nonlinear algebraic equations which is solved numerically. Numerical simulations, based on the mathematical model, are presented to analyze the nonlinear responses of the L-shape beam structure
Functional Series TARMA Models for Non-stationary Tool Vibration Signals Representation and Wear Estimation
No full textThis article addresses the problem of tool wear estimation using vibration signals. Time dependent time series models are suitable for extraction of time varying dynamics embedded in the non-stationary signals. A version of non-stationary time series known as Functional Series Time dependent AutoRegressive Moving Average (FS-TARMA) is employed for estimation of tool vibration signals and identification of the dynamics of tool/holder system. The obtained models associated with different levels of tool wear are compared by using characteristic quantities calculated based on model parameters. In this method, called model parameter-based method wear is estimated using a feature that is a function of model parameter vector obtained from FS-TARMA models. The advantage of this method over the ARMA metric employed in a previous study is that it does not violate the non-stationarity assumption of signals. The results of this study demonstrate that the FS-TARMA models with model parameter-based method provides higher accuracy in wear estimation compared with ARMA counterpart and also FS-TARMA with ARMA metric
Vibration Fatigue Analysis of a Cantilever Beam Using Different Fatigue Theories
No full textIn this study, vibration fatigue analysis of a cantilever beam is performed using an in-house numerical code. Finite element model (FEM) of the cantilever beam verified by tests is used for the analysis. Several vibration fatigue theories are used to obtain fatigue life of the cantilever beam for white noise random input and the results obtained are compared with each other. Fatigue life calculations are repeated for different damping ratios and the effect of damping ratio is studied. Moreover, using strain data obtained from cantilever beam experiments, fatigue life of the beam is determined by utilizing time domain (Rainflow counting method) and frequency domain methods, which are compared with each other. In addition to this, fatigue tests are performed on cantilever beam specimens and fatigue life results obtained experimentally are compared with that of in-house numerical code. It is observed that the accuracy of the damping ratio is very important for accurate determination of fatigue life. Furthermore, for the case considered, it is observed that the fatigue life result obtained from Dirlik method is considerably similar to that of Rainflow counting method
