Defect detection in mechanical systems is of critical importance in industrial applications, particularly for rotating components. This paper presents a model-based methodology for early online detection of mechanical faults using vibration analysis. The proposed approach is implemented in three main phases: model identification, optimal filter synthesis, and fault detection. A key advantage of this method is its ability to detect faults automatically, without requiring expert interpretation, and the possibility of putting it online or offline. This is achieved through a physics-based model of the system and an optimized implementation. Fault detection relies on analyzing the variance of the residual signal, defined as the difference between measured outputs and those estimated by the optimal filter. A fault is flagged when this variance exceeds a predefined threshold. The effectiveness of the method is demonstrated experimentally on a vibratory mechanical test bench equipped with gears. Validation is performed by comparing the results with expert assessments conducted during the experiments and with findings reported in the literature.
This paper presents an application of the Generalized Differential Quadrature Method (GDQM) to analyze the stability problem of a fluid-conveying conical pipe, clamped at both ends and resting on a Winkler elastic foundation. The main focus is on quantifying the impact of the rigidity of the elastic foundation on the critical fluid velocity, which is the velocity at which the pipe loses stability. A numerical solution was performed for a straight pipe conveying fluid with specified geometric and physical characteristics, where the rigidity of the elastic foundation and the density of the conveyed fluid were considered as parameters. The obtained results, visualized through graphical relationships between the critical velocity and the foundation's rigidity for various densities of the fluid, demonstrate the significant effect of elastic supports on the vibrational behavior and stability of the pipe. The validity of the presented GDQM approach is confirmed by comparison with results obtained using the Transfer Matrix Method (TMM), showing good agreement. The contribution of this paper lies in presenting a methodology for solving the differential equation describing the lateral displacements of conical piping systems, as well as in a critical assessment of the advantages and disadvantages of GDQM compared to established methods for the dynamic analysis of fluid-conveying pipes.
This paper presents a simulation-based study on the application of Independent Component Analysis (ICA) for separating idealized acoustic sources modeled as monopoles, dipoles, and quadrupoles. The work focuses on evaluating ICA performance in controlled synthetic configurations rather than experimental or real-world scenarios. Analytical models are used to generate pressure and particle-velocity fields for different multipole arrangements, which serve as input signals to the FastICA algorithm. Simulations include dipole cases (in-phase and anti-phase) and quadrupole configurations (lateral and longitudinal). Results show that ICA can recover the temporal structure and frequency content of the sources, despite the inherent amplitude-scaling ambiguities of the method. This study provides a preliminary assessment of ICA's capabilities in simplified acoustic environments and highlights its potential for future applications in noise analysis and source separation.
This paper presents a different approach for obtaining the eigenvalues of a combined system investigated previously. The mechanical vibration system in question consists of a horizontal Bernoulli-Euler beam carrying an axially vibrating rod with a tip mass at an intermediate location. In the context of the application of the Galerkin's procedure and assumed modes approach, the eigenfunctions of the fixed-free rod were previously used as trial functions in a study from the same authors [1]. As an alternative approach, the eigenfunctions of the rod with a tip mass are used as trial functions in this study. Using these eigenfunctions causes very fast convergence with a few numbers of trial functions to determine the eigenvalues. This fact is clearly demonstrated by means of tables and graphs as examples of Bernoulli-Euler beams with different boundary conditions. Also, the numerical results are compared with the values found by the finite element method (FEM), which can be considered as the exact eigenfrequencies of the system. This novel strategy accelerates the convergence rates. The efficacy of the method is demonstrated numerically. In addition, this study successfully demonstrates for the first time that when a continuous system is attached to the horizontal beam, the combined system has new eigenvalues between the original pair of the beam frequencies nearest to the eigenvalues of the attached continuous system, i.e., the axially vibrating rod with a tip mass.
The present work examines the influence of turbulent flow in pipeline systems at various fluid (water) flow rates, with an emphasis on the vibrations induced by this flow and the potential occurrence of resonance phenomena in specific sections of the pipe. To conclude, the study considers the VortexInduced Vibration (VIV) mechanism, associated with the periodic shedding of vortices in regions featuring geometric discontinuities such as elbows, tees, valves, reducers, and compares it with the natural vibration modes of the investigated system. A structural modal analysis of the piping system is conducted using AutoPIPE to identify the natural vibration modes and corresponding participation factors. Flow-induced excitation frequencies associated with internal fittings are estimated using Strouhal-based correlations under representative operating conditions. The proximity between excitation frequencies and structural natural frequencies is quantitatively assessed to identify vibration modes potentially prone to resonance. The results indicate that the first three and 11th vibration modes exhibit the greatest dynamic interaction influence under potential excitations. The proposed approach provides a practical, operational screening methodology for identifying vibration-resonance scenarios in existing piping systems.
