# US 2023/0266274 A1 · Identifying Structural Defect Geometric Features From Acoustic Emission Waveforms

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- Number: US 2023/0266274 A1
- Document ID: US20230266274A1
- Status: Published application
- Kind: A1
- Application number: 18/298,508
- Filed: 2023-04-11
- Published: 2023-08-24
- Earliest claimed: 2017-03-13
- Assignees: University of South Carolina
- Applicants: University of South Carolina
- Inventors: Victor Giurgiutiu; Jingjing Bao; Banibrata Poddar; Md Yeasin Bhuiyan
- Web page: https://patentgrep.com/patent/US20230266274A1

## CPC

- G01N 29/14: using acoustic emission techniques {(echo of particles G01N29/046; measuring mechanical vibrations or acoustic waves in solids in general G01H1/00)}
- G01N 29/2437: {Piezoelectric probes}
- G01N 29/4454: {Signal recognition, e.g. specific values or portions, signal events, signatures}
- G01N 29/46: by spectral analysis, e.g. Fourier analysis {or wavelet analysis (spectral signal processing per se G06F17/14)}
- G01N 2291/0231: Composite or layered materials
- G01N 2291/0232: Glass, ceramics, concrete or stone
- G01N 2291/0258: Structural degradation, e.g. fatigue of composites, ageing of oils
- G01N 2291/0289: Internal structure, e.g. defects, grain size, texture
- G01N 2291/2634: cylindrical from outside
- G01N 2291/2693: Rotor or turbine parts
- Y02B 10/30: Wind power
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS

## Abstract

The current disclosure determines if structural faults exist and extracts geometric features of the structural faults from acoustic emission waveforms, such as crack length and orientation, and can evaluate the structural faults online, during normal operation conditions.

## Claims

### Claim 1

A method for identifying features of a fatigue crack, comprising:
analyzing emission waves from a fatigue crack;
applying external excitation to the fatigue crack;
capturing at least one echo emanating from the fatigue crack caused by the external excitation;
generating at least one secondary emission wave that emanates from the fatigue crack;
analyzing amplitude and frequency of the at least one secondary emission wave; and
establishing an initial fatigue crack fingerprint for the fatigue crack and comparing the initial fatigue crack fingerprint to a subsequent fatigue crack fingerprint to analyze fatigue crack progression.

### Claim 2 (depends on 1)

The method of claim 1, further comprising identifying at least one geometric feature of the fatigue crack from analysis of the at least one secondary emission wave.

### Claim 3

The method of 2, further comprising identifying fatigue crack length and crack tip locations as part of the at least one geometric feature.

### Claim 4

The method of 2, wherein frequency dependent patterns in polar plots identify the at least one geometric feature of the fatigue crack.

### Claim 5 (depends on 1)

The method of claim 1, further comprising establishing a library of signal signatures paired with fatigue crack geometries.

### Claim 6 (depends on 5)

The method of claim 5, wherein modeling and scanning laser vibrometry are used in association with time signal analysis are used to establish the library of signal signatures.

### Claim 7

Creating a library of acoustic emission waveforms linked to crack geometric features comprising:
generating structural vibrations in a test material;
generating excitation signals and applying same to the test material;
collecting first acoustic emission signals generated by the test material; measuring surface vibration and displacement in the test material;
obtaining a frequency response of the test material to the excitation signals; extracting surface relative displacement to determine multiple candidate frequencies for acoustic wave detection;
exciting the test material with at least one candidate frequency and collecting at least one second acoustic emission signals from the test material;
analyzing the at least one second acoustic emission signal to extract at least one signal signature associated with fatigue crack geometric features; and
forming a library of features wherein the at least one signal signature is associated with fatigue crack geometric features; and
establishing an initial fatigue crack fingerprint for the fatigue crack geometric features and comparing the initial fatigue crack fingerprint to a subsequent fatigue crack fingerprint to analyze fatigue crack progression.

### Claim 8 (depends on 7)

The method of claim 7, wherein the structural vibrations are generated by internal and external excitation sources.

### Claim 9 (depends on 8)

The method of claim 8, wherein the internal excitation is provided by piezoelectric wafer active sensors.

### Claim 10

The method of claim of 8, wherein the external excitation is created by a mechanical shaker.

### Claim 11 (depends on 7)

The method of claim 7, further comprising identifying at least one geometric feature of a fatigue crack from analysis of the at least one second acoustic emission.

### Claim 12 (depends on 11)

The method of claim 11, further comprising identifying fatigue crack length and fatigue crack tip locations as part of the at least one geometric feature of the fatigue crack.

### Claim 13 (depends on 12)

The method of claim 12, wherein frequency dependent patterns in polar plots identify geometric features of the fatigue crack.

### Claim 14

A method for ensuring structural integrity comprising:
receiving acoustic emissions from a structure;
analyzing the acoustic emissions to determine if structural faults exist in the structure; and
wherein when at least one structural fault exists, establishing an initial structural fault fingerprint for the structural fault and comparing the initial structural fault fingerprint to a subsequent structural fault fingerprint to analyze structural fault progression.

### Claim 15 (depends on 14)

The method of claim 14, wherein analyzing the acoustic emissions compares structural vibration resonance frequencies and mode shapes.

### Claim 16 (depends on 14)

The method of claim 14 wherein, for structural faults found within the structure, a stress field is created.

### Claim 17 (depends on 16)

The method of claim 16 wherein the structural fault is a fatigue crack.

### Claim 18 (depends on 17)

The method of claim 17, further comprising analyzing the stress field around a fatigue crack tip to calculate resonance frequencies related to fatigue crack opening.

### Claim 19 (depends on 17)

The method of claim 17, wherein at least one geometric feature of the fatigue crack located within the structure is revealed by the analysis of the stress field.