Combined experimental/analytical modeling using component mode synthesis

Martinez, David R.; Carne, Thomas G.; Gregory, D.L.; Miller, A. Keith

doi:10.2514/6.1984-941

Cited by 61 publications

(31 citation statements)

References 3 publications

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“…It appears that the only drawback to that representation for modal synthesis or structural loads analysis is the difference in format compared to the widely used Craig-Bampton method. Martinez, Carne, et al 6 overcame this inconvenience by observing that the MacNeal and Rubin representation could be cast in a form similar to the Craig-Bampton formulation, thus facilitating practical use of the residual flexibility technique. As described in Ref.…”

Section: = a T G C Afmentioning

confidence: 97%

Residual flexibility test method for verification of constrained structural models

1994

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A method is described for deriving constrained modes and frequencies from a reduced model based on a subset of the free-free modes plus the residual effects of neglected modes. The method involves a simple modification of the MacNeal and Rubin component mode representation to allow development of a verified constrained (fixed-base) structural model. Results for two spaceflight structures having translational boundary degrees of freedom show quick convergence of constrained modes using a measurable number of free-free modes plus the boundary partition of the residual flexibility matrix. This paper presents the free-free residual flexibility approach as an alternative test/analysis method when fixed-base testing proves impractical. NomenclatureA -transformation matrix for flexibility F = external force vector G = flexibility matrix G r = residual flexibility matrix H = mass matrix associated with residual flexibility K = stiffness matrix K = reduced stiffness matrix M = mass matrix M = reduced mass matrix m = number of retained modes plus boundary coordinates TV = number of coordinates in unreduced structure n = number of retained or measured modes n b = number of boundary coordinates q = generalized displacement vector T = transformation matrix to reduce structure coordinates u = physical structure displacement vector $ = mode shapes w,12 = natural frequencies Subscripts b = boundary coordinates c = constrained structure / = flexible structure / = interior coordinates n = retained modes R = rigid body r = residual Introduction D EVELOPMENT of a dynamic model of a constrained structure having acceptable fidelity requires a modal survey test of the physical structure and subsequent improvement of the model using test data. Constrained-boundary or fixedbase testing has historically been the most common approach for verifying constrained mathematical models, since the boundary conditions of the test article are designed to match the actual constraints in service.Unfortunately, there are a number of difficulties involved with fixed-base testing, making the approach impractical in some cases. As stated in Refs. 1 and 2, it is not possible to conduct a truly fixed-base test due to coupling between the test article and the fixture. In addition, it is often difficult to accurately simulate the actual boundary constraints, and the cost of designing and constructing the fixture may be prohibitive.Alternate free-boundary test methods for deriving constrained modes have been investigated for use when measurement of fixed-base modes proves impractical or undesirable. The mass-additive technique 1 ' 2 is an interesting approach that shows promise, though large sets of free-free modes are required for some structures. Blair and Vadlamudi 3 presented a useful method for model improvement where the minima of the interface response functions were used to assess model adequacy in the interface regions. This data in combination with the free-free mode set was used to obtain a Shuttle-constrained space telescope model for loads analysi...

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Section: = a T G C Afmentioning

confidence: 97%

Residual flexibility test method for verification of constrained structural models

1994

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“…The free modes of a structure are much easier to obtain experimentally, but they are known to constitute a poor basis for substructuring predictions [14], as nicely illustrated in [15]. Better results are obtained when the free modes are augmented with residuals to account for the flexibility of out of band modes, as pioneered in [14,16,17]. However, the residual terms are weakly represented in the measurements and can be difficult to accurately measure, and one must typically apply many additional inputs to obtain a full set of residual flexibilities.…”

Section: Introductionmentioning

confidence: 97%

Experimental modal substructuring to estimate fixed-base modes from tests on a flexible fixture

Allen

Gindlin

Mayes

2011

Journal of Sound and Vibration

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“…There has been interest in being able to couple experimental and analytical substructures for a long time [1], but difficulties in the experimental methods prevented the common use of experimental substructures. There has been a resurgence of interest in experimental dynamic substructures in the past few years that has been demonstrated by the number of papers and sessions at IMAC.…”

Section: Introductionmentioning

confidence: 99%

Wind Turbine Experimental Dynamic Substructure Development

Mayes

2012

Topics in Experimental Dynamics Substructuring and Wind Turbine Dynamics, Volume 2

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Structural dynamic development of modern wind turbines is important for control and to maximize the fatigue life of the wind turbine components. Modeling can be used in development to aid designs. In some cases an experimental dynamic model, or substructure, may be cheaper to develop and more accurate than an analytical model. Some applications for which dynamic substructures could be useful for wind turbine development are presented. Recent advances have provided renewed interest in the topic of experimental dynamic substructures. A focus group has been formed in the Society for Experimental Mechanics to advance the experimental dynamic substructures technology and theory. Sandia National Laboratories has developed two identical test beds to enable the focus group to advance the work. The system chosen was an Ampair 600 wind turbine with a fabricated tower and base. Some modifications were made to the system to make it more linear for initial studies. The test bed will be available for viewing in the technology booth of the IMAC exposition. A description of the turbine and modifications will be presented. Initial measurements on the full system will be described. Organizations already performing experiments on the test bed are the UK Atomic Weapons Establishment,

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Combined experimental/analytical modeling using component mode synthesis

Cited by 61 publications

References 3 publications

Residual flexibility test method for verification of constrained structural models

Residual flexibility test method for verification of constrained structural models

Experimental modal substructuring to estimate fixed-base modes from tests on a flexible fixture

Wind Turbine Experimental Dynamic Substructure Development

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