Probabilistic Sizing of a Fatigue Crack on Type 304 Austenitic Stainless Steel from Eddy Current Signals

This Study Aimed To Probabilistically Evaluate The Size Of A Fatigue Crack On A Type 304 Austenitic Stainless Steel Flat Plate Using Eddy Current Signals. Three Fatigue Cracks, With Depths Ranging From 2 Mm To 5 Mm, Were Introduced Into The Plates Through A Four-Point Bending Test. After The Starter Notches For The Test Were Removed, Eddy Current Testing Was Conducted Using A Differential-Type Plus Point Probe At A Frequency Of 200 Khz To Collect Signals Caused By The Cracks. The Fatigue Crack Was Modeled As A Rectangular Continuous Domain With A Constant Width And Uniform Electromagnetic Properties. Since Mechanical Damage Transforms The Austenitic Phase Into The Martensitic Phase, Both The Conductivity And Permeability Of The Domain Were Explicitly Considered. The Depth And Length Of The Cracks Were Evaluated Using A Bayesian-Based Inverse Algorithm, Assuming The Electromagnetic Properties Of The Crack Were Either Known (Equal To Air) Or Unknown. When The Crack Was Modeled As Air, The Evaluated Crack Sizes Deviated Considerably From The Actual Sizes. In Contrast, Assuming The Electromagnetic Properties To Be Unknown Provided Better Evaluations With Quantified Uncertainty.