NASTRAN Forced Vibration Analysis of Rotating Cyclic Structures

Elchuri, V.; Smith, G. C. C.; Gallo, A. M.

doi:10.1115/1.3269173

Cited by 6 publications

(2 citation statements)

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“…Many researchers have used cyclic symmetry to analyze a whole structure based on a single-sector FEM. 10,11,[22][23][24] Note that in Bladh et al's work, 11 the definition and application of the real Fourier matrix and a pseudo-block-diagonal matrix, which are used in this section, are well explained.…”

Section: Application To a System Subject To Design Changesmentioning

confidence: 99%

Vibration Modeling of Bladed Disks Subject to Geometric Mistuning and Design Changes

Lim¹,

Castanier²,

Pierre³

2004

45th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics &Amp;amp; Materials Conference

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In this paper, a new reduced-order modeling technique is presented for bladed disks that feature large, geometric deviations from a nominal design. Various finite-element-based reduced-order models (ROMs) have been proposed in the literature for bladed disks with small blade-to-blade differences, called mistuning. Many of these techniques rely on the fact that mistuned-system normal modes can be effectively represented using a linear combination of the normal modes of the nominal (tuned) system. However, when the mistuning or geometric deviation is large, the number of tuned-system normal modes required to describe the mistuned-system normal modes increases dramatically. In this work, a method for large mistuning is formulated by employing a mode-acceleration method with static mode compensation. By accounting for the effects of mistuning as though they were produced by external forces, a set of basis vectors is established using a combination of tuned-system normal modes compensated by static modes. The obtained basis vectors approximately span the space of the mistuned-system modes without requiring a much more expensive modal analysis of the mistuned system, and they provide much better convergence than tuned-system normal modes. Furthermore, in order to extend the method to higher frequency ranges, quasi-static modes, in which inertia effects are included, are employed in place of static modes in the modeacceleration formulation. It is seen that ROMs based on the new technique are extremely compact, yet they accurately capture the vibration response of bladed disks subject to geometric mistuning or design changes.

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Section: Application To a System Subject To Design Changesmentioning

confidence: 99%

Vibration Modeling of Bladed Disks Subject to Geometric Mistuning and Design Changes

Lim¹,

Castanier²,

Pierre³

2004

45th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics &Amp;amp; Materials Conference

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“…Based on the nominal design, a bladed disk assembly is a rotationally periodic structure. If it is assumed that each sector is identical, then the theory of cyclic symmetry may be used to analyze the dynamics of the entire structure based on, say, a finite element model of one sector (Joseph, 1981;Elchuri et al,1984;Hitchings and Singh, 1987). In practice, however, there are small differences among the structural properties of individual blades -due to manufacturing tolerances, material deviations, and non-uniform operational wear.…”

Section: Introductionmentioning

confidence: 99%

Reduced Order Modeling and Vibration Analysis of Mistuned Bladed Disk Assemblies With Shrouds

Bladh

Castanier

Pierre

1998

Volume 5: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation;

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This paper presents important improvements and extensions to a computationally efficient reduced order modeling technique for the vibration analysis of mistuned bladed disks. In particular, this work shows how the existing modeling technique is readily extended to turbomachinery rotors with shrouded blades. The modeling technique employs a component mode synthesis approach to systematically generate a Reduced Order Model (ROM) using component modes calculated from a Finite Element Model (FEM) of the rotor. Based on the total number of degrees of freedom, the ROM is typically two or three orders of magnitude smaller than the FEM. This makes it feasible to predict the forced response statistics of mistuned bladed disks using Monte Carlo simulations. In this work, particular attention is devoted to the introduction of mistuning into the ROM of a shrouded assembly. Mistuning is modeled by projecting the mistuned natural frequencies of a single, cantilever blade with free shrouds onto the harmonic modes of the shrouded blade assembly. Thus, the necessary mistuning information may be measured by testing individual blades.

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Bladed Disks

Rao¹

2011

History of Mechanism and Machine Science

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NASTRAN Forced Vibration Analysis of Rotating Cyclic Structures

Cited by 6 publications

References 0 publications

Vibration Modeling of Bladed Disks Subject to Geometric Mistuning and Design Changes

Vibration Modeling of Bladed Disks Subject to Geometric Mistuning and Design Changes

Reduced Order Modeling and Vibration Analysis of Mistuned Bladed Disk Assemblies With Shrouds

Bladed Disks

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