報告書番号

T99033

タイトル（和文）

渦電流法に基づくガスタービン動翼の非破壊損傷評価 -－ 第1報： 数値解析による検査法の最適化 －-

タイトル（英文）

Eddy-current Techniques for Nondestructive Assessment of Land-based Gas Turbine Blades― Part 1: Numerical Modeling for Optimizations of Eddy-current inspection ―

概要 （図表や脚注は「報告書全文」に掲載しております）

ガス・蒸気タービンのコンバインドサイクル火力発電において，タービン動翼の余寿命評価のための非破壊検出法の開発が望まれている．本研究では有限要素法を用いて，き裂および劣化に対する渦電流試験の信号を予測するための順問題解析手法，信号からき裂形状および劣化を推定する逆問題解析手法を開発した．開発した数値解析手法を用いて，渦電流試験による1100℃級ガスタービン初段動翼検査の最適な測定条件(励磁・検出方式，試験周波数)を明らかにした．数値解析により得られた結果に基づき，推奨検査法として取りまとめた．

概要 （英文）

There has been a growing need in recent technology gas and steam turbines in combined cycle to assess the remaining life of aging components. It is also required the nondestructive assessment be more accurate in maintaining combined cycle plants. This report describes the development of a simulator solving forward and inverse problems under eddy current testing, and parametric studies of inspection parameters for 1100 ℃-class turbine blades in terms of test probe capabilities, frequencies and signal interpretation. The simulator is based on a differential formulation constructed with a magnetic vector potential and 3-dimensional edge-based finite-element modeling methods. Numerical predictions for eddy current responses are in excellent agreement with the corresponding experimental measurements, and demonstrate the potential of the code. Using the simulator, optimal sensor types and test frequencies have been determined in terms of identification of conductivity and thickness, selectablity between surface and buried cracks, identification of crack profiles, detection of multiple cracks. Some useful recommendations have been made to design an in situ inspection system.

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