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

Abstract

This paper presents an 'As-Measured Model' of a blended blisk, built upon the measurement of the true geometry of the blisk by the 3D optical scanning technology. This high-fidelity model aims to account for the variances of blade frequencies and mode shapes within the real blisk in the presence of both the blend repair and inherent geometry mistuning due to manufacturing, etc. An improved mesh updating strategy is proposed to adapt a seed blisk finite element model to the measured geometry. The resultant 'as-measured model' is therefore able to accurately represent the measured blade-to-blade geometry variances. The classical blade detuning test in combination with a novel 'correction' procedure is employed to experimentally evaluate the 'blade-alone' frequency mistuning pattern in the real blisk. Experimental verification of the 'as-measured model' demonstrates that it is able to not only capture the 'blade-alone' frequency and mode shape variations due to both the blend and intrinsic blade geometry variances, but also to reproduce the global dynamics of the blended blisk with acceptable accuracy.

Sector Mode Assembling Reduction Technique for High-Fidelity Blisk Models with Geometry Mistuning

“…The methodologies of constructing the AMM will be briefly revisited hereafter. For complete details, readers are referred to the authors' recent research work [15].…”

“…An improved mesh updating strategy incorporating a "premorphing" step is therefore proposed by the authors in Ref. [15] in order to override the potential problem of spurious node projection. As shown in Fig.…”

“…In the previous paper [15] the authors have demonstrated that the AMM is able to capture not only the blade-alone frequency and mode shape variations due to both the blend and intrinsic blade geometry variances, but also the global dynamics of the blended blisk with acceptable accuracy. For the sake of brevity, this topic is not covered in this paper.…”

“…These high-fidelity models have been also utilized for determining the sensor locations in an optimal sense [11,12], more accurate fluid dynamic simulations [13], etc. More recently, the concept of "as-manufactured model" has been extended in a single blade [14] and a full blisk [15] undergoing blend repairs, respectively. All these research efforts align with the digital twin philosophy that the digital representations of the real aeroengine parts, converted from the precise geometry measurement data, enable to evaluate and monitor the products' performance through the life cycle in an effective way.…”

“…II. This novel reduction technique will be applied to a high-fidelity blisk model with incompatible blade meshes due to a single blend repair, which was recently constructed upon the measured blade geometries by 3D optical scanning system [15]. Performance of the SMART approach will be fully addressed by comparison with the full-order FE model analysis results in Sec.…”