Evaluation of Cracks in Metallic Material Using a Self-Organized Data-Driven Model of Acoustic Echo-Signal

Xudong Teng,Dong Zhang,Xin Zhang,Yuantao Fan

doi:10.3390/app9010095

Abstract

Non-linear acoustic technique is an attractive approach in evaluating early fatigue as well as cracks in material. However, its accuracy is greatly restricted by external non-linearities of ultra-sonic measurement systems. In this work, an acoustical data-driven deviation detection method, called the consensus self-organizing models (COSMO) based on statistical probability models, was introduced to study the evolution of localized crack growth. By using pitch-catch technique, frequency spectra of acoustic echoes collected from different locations of a specimen were compared, resulting in a Hellinger distance matrix to construct statistical parameters such as z-score, p-value and T-value. It is shown that statistical significance p-value of COSMO method has a strong relationship with the crack growth. Particularly, T-values, logarithm transformed p-value, increases proportionally with the growth of cracks, which thus can be applied to locate the position of cracks and monitor the deterioration of materials.

Highlights

Nonlinear ultrasonic behaviors, such as harmonics, mix frequencies, and the resonance frequency shift, have been proven to be sensitive to structure imperfections and early degradation of materials [1,2,3,4,5,6]
Four cracks distributed along the length direction of a steel specimen were investigated, and the crack’s growth was further discussed in details, which is probably accord with the mechanisms involved in contact acoustic nonlinearity and hysteretic nonlinearity. Both Numerical simulation and experimental measurements showed that consensus self-organizing models (COSMO) models are effective in NDT inspection, as well as health monitoring for regular metallic structures
A 0.5 MHz continuous sinusoidal signal with signal‐noise ratio (SNR) of 15 dB was applied as the exciting signal

Summary

Introduction

Nonlinear ultrasonic behaviors, such as harmonics, mix frequencies, and the resonance frequency shift, have been proven to be sensitive to structure imperfections and early degradation of materials [1,2,3,4,5,6]. Four cracks distributed along the length direction of a steel specimen were investigated, and the crack’s growth (produced using fatigue testing [26]) was further discussed in details, which is probably accord with the mechanisms involved in contact acoustic nonlinearity and hysteretic nonlinearity. Both Numerical simulation and experimental measurements showed that COSMO models are effective in NDT inspection, as well as health monitoring for regular metallic structures. Based on a uniformity test of z-scores over an area, the resulting p-value of this test is obtained to estimate whether the inspected contains any micro-flaws

Numerical Simulation

Schematic

Experimental Measurement

Four sections embedded cracks minimum sum was chosen in the metric

It in is shown of

Conclusions