Natural Frequency Changes due to Severe Corrosion in Metallic Structures

Gillich, Gilbert-Rainer; Praisach, Zeno Iosif; Iancu, Vasile; Furdui, Horia; Negru, Ionica

doi:10.5545/sv-jme.2015.2674

Cited by 26 publications

(16 citation statements)

References 8 publications

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“…The effects of various defects on the vibration characteristics of structures and rotor systems have always been of great significance among researchers, and related works are reported in the literature. Gillichet al [ 20 ] developed two kinds of mathematical relations for predicting frequency changes due to the two main effects of corrosion—loss of mass and decrease in stiffness. Shekar and Prabhu [ 21 ] studied the effect of coupling misalignments on the vibration characteristics of a rotor-bearing system.…”

Section: Introductionmentioning

confidence: 99%

Effect of Corrosion on the Natural and Whirl Frequencies of a Functionally Graded Rotor-Bearing System Subjected to Thermal Gradients

et al. 2020

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Corrosion causes a loss of material resulting in the reduction of mass and stiffness of a component, which consequently affects the dynamic characteristics of any system. Fundamental frequency analysis of a corroded functionally graded (FG) rotor system, using the finite element method based on the Timoshenko beam theory, was investigated in the present paper. The functionally graded shaft consisting of an inner metallic core and an outer ceramic layer was considered with the radial gradation of material properties based on the power law. Nonlinear temperature distribution (NLTD) based on the Fourier law of heat conduction was used to simulate the thermal gradient through the cross-section of the FG rotor. The finite element formulation for a functionally graded shaft with a corrosion defect was developed and the dynamic characteristics were investigated, which is the novelty of the present work. The corrosion parameters such as length, depth and position of the corrosion defect in the shaft were varied and a parametric study was performed to investigate changes in the natural and whirl frequencies. An analysis was carried out for different power indexes and temperature gradients of the functionally graded shaft. The effects of corrosion were analysed and important conclusions are drawn from the investigations.

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Section: Introductionmentioning

confidence: 99%

Effect of Corrosion on the Natural and Whirl Frequencies of a Functionally Graded Rotor-Bearing System Subjected to Thermal Gradients

et al. 2020

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“…Starting from kinetic energy conservation [11] we can write the equivalent mass contribution for each segment of the weld beam: …”

Section: Weld Beam Behavioral Modelmentioning

confidence: 99%

Integrity evaluation concerning vibrations of a welded structure

et al. 2017

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Abstract. In this paper, a predictive model that describes the structural behavior in the absence and presence of damage, and anticipates the modal parameter changes, is introduced for weld structures. Degradation of engineering structures in the welds or HAZ due to damage affects their safety by reducing the stiffeners of structural components. In this paper was considered the kinetic energy distribution which reflects the mass participation, and the modal strain energy distribution which take into consideration the stiffeners reduction. The relation is successfully proved against FEM simulation results.

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“…In previous research [15][16][17][18], the authors developed robust techniques for assessing transverse or complex-shaped cracks for beams and plates, regardless of the structure's boundary conditions. All these techniques are based on the natural frequency shifts and evaluate the severity by energetic methods.…”

Section: Introductionmentioning

confidence: 99%

The effect of a crack near the fixed end on the natural frequencies of a cantilever beam

Tufiși¹,

Gillich²,

Aman³

2019

Vib. proced.

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The paper examines how a transverse crack near the fixed end of a beam affects the natural frequency drop. It is known that the decrease in the frequency due to a crack depends on the position of the damage and its severity. This happens because the slice of the beam on which the crack is located changes its stiffness. Consequently, the damaged beam is no longer able to store the identical amount of energy as the healthy one. In addition, the field of stresses and deformations on an extended area around the crack is disturbed. This alteration can manifest freely for most positions of the crack along the beam. For this case, there is a direct relationship between the defect position and the frequency change, given by the modal curvature of the beam. Close to the fixed end, the field of stress and deformation is hindered on one side of the crack by the fixed end condition. In this way, the crack will produce a lower frequency drop compared with what it is expected. We performed simulations to obtain the frequency drop if the crack is located very close to the fixed end. With these values, we plot the regression curve and estimate the frequencies which should result for a crack located exactly on the fixed end of the beam if symmetric fields of stress and strain are possible. The results are necessary because the frequency drop characterizes the damage severity, further used in the damage detection processes.

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Natural Frequency Changes due to Severe Corrosion in Metallic Structures

Cited by 26 publications

References 8 publications

Effect of Corrosion on the Natural and Whirl Frequencies of a Functionally Graded Rotor-Bearing System Subjected to Thermal Gradients

Effect of Corrosion on the Natural and Whirl Frequencies of a Functionally Graded Rotor-Bearing System Subjected to Thermal Gradients

Integrity evaluation concerning vibrations of a welded structure

The effect of a crack near the fixed end on the natural frequencies of a cantilever beam

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