Modified Modal Domain Analysis of a Bladed Rotor Using Coordinate Measurement Machine Data on Geometric Mistuning

Abstract

Modified modal domain analysis (MMDA), a reduced order modeling technique, is applied to a geometrically mistimed integrally bladed rotor to obtain its natural frequen cies. mode shapes, and forced response. The geometric mistuning of blades is described in terms of proper orthogonal decomposition (POD) of the coordinate measurement machine (CMM) data. Results from MMDA are compared to those from the full (360 deg) rotor ansys model. It is found that the MMDA can accurately predict natural frequencies, mode shapes, and forced response. The effects of the number of POD features and the number of tuned modes used as bases for model reduction are examined. Results from fre quency mistuning approaches, fundamental mistuning model (FMM) and subset of nomi nal modes (SNM), are also generated and compared to those from full (360deg) rotor ansys model. It is clearly seen that FMM and SNM are unable to yield accurate results whereas MMDA yields highly accurate results.

A novel model reduction approach for blisks with blend repairs and small mistuning

“…For blisks with small geometric mistuning, the mode basis could be expanded by incorporating the cyclic modes of the different geometrically mistuned sectors [23,24]. In the Modified Modal Domain Analysis (MMDA) [25], the geometric variations are represented by a few Proper Orthogonal Decomposition (POD) features. The reduction basis is then constructed by a truncated cyclic modes of a 'tuned' blisk carrying a predominant POD feature.…”

“…Generally speaking, any pristine sector associated with a unique blade geometry should be treated as an independent sector type. It is also reported that the Principal Component (PC) Analysis [15,16] or Proper Orthogonal Decomposition (POD) [25] can capture the geometry variances of a group of blades by quite a few PCs or POD features. This enables to construct a reduced representation of the blade geometry variances by retaining only the predominant PCs or POD features of the blade geometries.…”

Blisk With Small Geometry Mistuning and Blend Repair: As-Measured Finite Element Model and Experimental Verification

“…Nevertheless, the traditional frequencymistuning approaches, assuming a unique frequency mistuning source, fail to account for the changes in blade mode shapes due to geometry variance. Therefore, this has been motivating the continuous researches in the modeling and analysis of geometrically mistuned blisks [10,11].…”

Generalized SAFE Diagram for Mistuned Bladed Disks

“…The intentional and random mistuning components both need to be experimentally characterized, after manufacturing the disk, for a design verification and a sensitivity analysis. Several methods for mistuning modelling and identification have been proposed in the literature, based on the model reduction approach [14,15]. The main techniques are Fundamental Mistuning Model (FMM) [16][17][18], Asymptotic Mistuning Model (AMM) [10,19], and Component Mode Mistuning (CMM) method [20][21][22][23][24].…”