January 2022 | Vol. 2

ACOUSTIC EMISSION WORKING GROUP[AEWG]
Annual Newsletter of Acoustic Emission Developments and Ideas!

WELCOME NOTE FROM THE AEWG EXECUTIVECOMMITTEE!
We would like to welcome you all to the second issue of AEWG newsletter. We did not have the AEWG meeting in 2021 due topandemic; however, this newsletter provides an opportunity to share news with the AE community. We would like to thank thecontributing authors to the second issue of AEWG digital newsletter. We have worldwide cutting-edge research articles in
addition to international and academic/industry collaboration news. The content of this issue includes
Remembering Allen Green
Update on AEWG-63
AEWG Executive Committee Conference Participation: SHMII-10 Roundtable Discussion
Worldwide AE Research News: Europe, US, Japan and Egypt
International Collaboration on AE: Japan and Turkey
University-Industry Collaboration on AE Sensor
AE e-Textbook
News from AE Manufacturers
Conference and Meeting Announcements

Newsletter Designed by: Sarah Malik, Drexel University

REMEMBERING ALLEN GREEN
Allen T. Green, Acoustic Emission pioneer, of Sacramento, CA,passed away June 13, 2021. He was 87 and is survived by his wife,
Carolyn, by his four children, Keri, Leah, Brady and Natanya, andfour grandchildren. He was internationally known for his lifelong
devotion to acoustic emission research and development. After
graduating from University of Illinois with an aerospaceengineering degree (1956), he joined the Aerojet team thatsuccessfully used AE for steel and fiber-composite missile
motorcases, the first such an engineering achievement globally(1960-1970). It is remarkable that despite joining Aerojet project
mid-way, he was the lead author of their 1964 paper in Modern
Plastics (volume 41 (No. 11), 137). When you read it, you’ll findtechnologies well ahead of the vacuum-tube-to-transistor
generation, a wavelet-like spectrograph, for example. After a short
stint at Dunegan Research, Allen founded Acoustic Emission
Technology Corp. in 1972, guiding AE instrumentation
development, from laboratory units to multichannel industrial
installations. When AET Corp was eventually absorbed into a large
corporation (1991), he shifted to AE consultancy and distributing AE
instrument with Acoustic Technology Group, retiring from businessin 2009.
He was one of the founding members of Acoustic Emission
Working Group when it was formed in 1967. He served as its
Chairman in 1971-1972, covering the 7th to 9th AEWG meetings. His
AE reputation and business skills led to two successful international
conferences at Lake Tahoe in 1985 and 2007. Both of them also
filled AEWG coffer well. He also organized three other AEWG
meetings, five altogether; the most in the AEWG history. AEWG has
recognized his varied contributions with the Charter Fellow (1982),
the Gold Medal Award (1983) and the Special Recognition Award(2000), the latter for his lifetime AE achievement. He served as a
global AE missionary, giving an AE short course in Israel in 1983 andinvited lectures at two inaugural international conferences in Japan(1972) and in China (2011) among many others. These two
conferences continue today. Allen also served as Honorary
President of the Chinese conference. In addition to AEWG, he wasmember of ASNT (Fellow) and ASME (Fellow, Dedicated Service
Award). He will be dearly missed by his family, friends andcolleagues from around the world.
Kanji Ono, Tom Drouillard and Gordon Schneider

Further Information
AEWG News at http://aewg.org/
IIIAE News at http://iiiae.org/

AEWG-63
DATE TO BE DETERMINEDHOUSTON, TX
We are closely watching the pandemic. We are excited tosee some conferences started to be in person. We will
announce the dates of AEWG-63 in late January. Due tothe worldwide travel restrictions, we aim to have in person
and virtual participation options.
AEWG-63 will be hosted by Stress Engineering in Houston,
Texas. The meeting chair will be Napoleon Douglas.
The tentative schedule is as follows:(Monday) – Primer on Acoustic Emission in Oil and Gas Industry at
AM, Welcome
reception & Social at PM(Tuesday) – Technical presentations, panel discussions, session forvendorpresentations, dinner at PM(Wednesday) - Technical presentations, panel discussions, AEWG
business meeting
ending by 5:00pm, tourThank you toStress Engineeringfor Hosting!

AEWG EXECUTIVE COMMITTEEPARTICIPATED SHMII-10
ROUNDTABLE DISCUSSION

Roundable Discussion

ANTONIOS KONTSOS
Professor
Dept. of Mechanical Engi­n eering and Mechanics
Drexel University+1 (215) 895 2297
antonios.kontsos@drexel.edu

Three members of the AEWG Executive Board including Chair Dr. Didem
Ozevin, Vice-Chair Dr. Valery Godinez and Secretary Dr. Antonios Kontsos
were among the panelists of a round table discussion on Nondestructive
Evaluation (NDE) of Structural Materials which took place in the 10th
International Conference on Structural Health Monitoring of Intelligent
Infrastructure (SHMII-10), an online event organized by the University ofPorto, Portugal, in June 30th-July 2nd, 2021. The discussion in this roundtable focused on NDE and its use in Structural Health Monitoring (SHM)
via the combination of diagnostics data obtained by nondestructive testing(NDT) with prognostics information created by both physics-based
simulations, as well as data-driven machine learning and artificial
intelligence methods (ML/AI). Issues related to data management, use of
NDE data in reliable numerical modeling (e.g., using the Finite Element
Method) in addition to coupling NDE with modern ML & AI methods indigital twin operations, were discussed. The AEWG representatives in thisround table provided further comments in cutting-edge issues such as theuse of modern NDE sensor technologies in Industrial Internet of Things(IIoT) applications in SHM. An additional topic explored in this discussion
involved the role of Acoustic Emission in the emerging NDE 4.0 paradigm,
a term used in parallel with the transformative Industry 4.0 concept, whichis part of the growing digital transformation processes implemented
worldwide.

RECENT ADVANCES IN AE MONITORING OF
CORRODING REINFORCED CONCRETESTRUCTURES
PROF ELS VERSTRYNGE & DR.CHARLOTTE VAN STEEN
Materials and Constructions Division, Department of Civil
Engineering
KU Leuven, Belgium

Research Spotlight

Corrosion of the reinforcement is a major deterioration process in existing reinforced concrete (RC)structures. It causes large economic losses and jeopardizes the structural safety. The process starts
internally and the steel section loss is accompanied by the formation of corrosion products. These exert apressure on the surrounding concrete, eventually leading to concrete cracking and spalling. The AE
technique is a valuable method for corrosion damage detection, as it allows to monitor internal damage
progress in the structure before damage can be observed on the surface.
Current research at the Materials and Constructions group at KU Leuven focuses on detection, localization,and characterization of corrosion-induced damage in RC. An extensive experimental program is
performed on three samples scales, and data processing protocols are integrated in an AE analysis toolbox.
Tests include accelerated corrosion tests on small samples, concrete prisms and beams, as well as on-sitemonitoring on bridge girders. AE results are validated with other NDT techniques, such as crack width
measurements and X-ray computed tomography, the latter in collaboration with the XCT Core Facility at
the Materials Engineering Department at KU Leuven.
The test program has shown that the AE technique is able to successfully detect corrosion damage inreinforced concrete. However, dedicated filtering proved to be necessary to reliably localize andcharacterize AE sources. Therefore, a post-processing protocol is developed which significantly improves
the localization results. The corrosion
process as well as concrete cracking canbe identified from cumulative AE curves,and characterized from signal-based
analysis. Moreover, it is shownthat the AE technique is able todetermine the onset of concrete
cracking earlier thana visual inspection. Finally, asignal-based clustering algorithm
is developed for automaticcharacterization of AE sources.
Further Reading: Van Steen, C.,
Verstrynge, E. (2021). Degradation
Monitoring in Reinforced Concretewith 3D Localization of Rebar
Corrosion and Related Concrete
Cracking. Applied Sciences, 11 (15),
Art.No. 6772. doi:
10.3390/app11156772

AE STUDY ON SEISMOLOGYJESSE HAMPTON, PHD
Assistant Professor
Geomechanics and Damage Group (GeoD) geod.wisc.edu
Geological Engineering, Civil and Environmental Engineering
University of Wisconsin-Madison
jesse.hampton@wisc.edu

Research Spotlight

Quantifying the interaction between microcracks has far-reaching implications in the fields of damage mechanics,
fault mechanics, induced seismicity, and many others. The interaction between microcrack localizations inrock/concrete impacts the progression and evolution of fracture development and eventual macro-scale fracture
coalescence. In damage mechanics, quantifying the influences of fracture interactions can increase the accuracy ofeffective property predictions via constitutive frameworks and continuum-scale models (e.g., macro-scale effective
stiffness of a material due to the existence, and interaction, of microcracks). In subsurface engineering (e.g., deep Earthgeothermal), induced seismicity is an active area of research, where the interaction and causative mechanisms ofrupture are difficult to interpret.
The GeoD group is actively working in both the areas of damage mechanics and induced seismicity associated with
subsurface engineering. To that end, a recent discovery has shown, for the first time at the laboratory scale, thetriggering/triggered relationships between individual microcrack events near and far from one another in space andtime. A topology analysis typically used for seismic catalogs attributing to the seismogenic structures is introduced
into the analysis of the AE releasing structure, i.e., the AE-genic zone. This method identifies the most probable
trigger for of a concurrent event by seeking one of its previous events having formed the minimal event-pair metricwith that concurrent event in normalized time and space. This model seeks violation of the null hypothesis that events
are occurring randomly with a rate given by the Gutenberg-Richter law. A topological network can be built
dynamically for an entire rock fracture process upon the real triggering-triggered relationships for the subsequently
occurring new events from the AE genic zone. The figure shows one result from the AE analysis on a Carrara marble
specimen containing a pre-cut flaw, where individual events induce non-local microcrack localizations in a cascading
and chain-reaction type phenomena. Here we see the progression of triggering where triggered microcracks canmigrate within one fracture system (a), traverse across the large-scale flaw (b), traversing back and forth between
upper- and lower-fracture systems (c), and progressively migrate across the flaw (d).
The discovery of nonlocal triggering at the lab-scale has direct implications for understanding stress chains andfuture work can be used to better interpret field-scale seismicity. We are actively working in damage mechanics andinduced seismicity in geothermal environments.

Further Reading: Xiong g, Q., & Hampton, J. C. (2020). Non‐local
triggering in rock fracture. Journal of Geophysical Research: Solid
Earth, 125, e2020JB020403. https://doi.org/10.1029/2020JB020403.

NON-CONTACT AE MEASUREMENT SYSTEM AND ITSAPPLICATIONTAKUMA MATSUO
Associate Professor
Department of Mechanical Engineering
Meiji University
e-mail: matsuo@meiji.ac.jp

Research Spotlight

A non-contact AE monitoring system is under development. The system consists of a digitizer with areal-time noise reduction function developed in our laboratory and an air-coupled ultrasonic sensor.
By reducing the noise, it is possible to detect weak AE signals, even by using air-coupled ultrasonicsensors, which are less sensitive than contact-type AE sensors. Example applications of this system aregiven below.
1. Measurement of AE signals generated by bending fatigue in a rotating component: The fatigue
monitoring of rotating components during operation is difficult because the attachment of a sensor to
the surface of the rotating components is difficult. Therefore, AE signals excited with the initiation andpropagation of cracks resulting from rotating bending fatigue were measured using the system being
developed. When a contact-type AE sensor was installed on the bearing housing, AE could be detected
only just before fatigue failure; however, the developed system was able to detect AE signals at an
earlier stage.
2. Detection of packing error occurring during the packaging of cookies: Product packing errors are aserious problem in food factories because of food safety issues. In particular, small pieces of baked
products often cause packing errors in factories that produce baked goods when the products arewrapped with a cover film and the film is sealed. In this study, the developed system was used to detect
AE signals caused by packaging errors by placing the sensor above a film. It was possible to detect AE
signals excited by the fracture of small pieces of cookies caused by the packaging film.
3. Non-contact remote AE detection system using a drone equipped with a sensor: Mounting thesensor of the developed system on a drone made it possible to develop a flight-type AE measurement
system that can be used for monitoring at high altitudes. The noise reduction function reduced thenoise generated by the drone blades, and the system could detect AE signals with stable sensitivity,
even during drone flight. It was then possible to detect AE signals excited by the rust fracture on a steel
plate with the system in flight.
In the future, it is planned to design a sensor shape to improve the sensitivity and develop an optimalnoise reduction algorithm to create a system that can measure AE in various locations.

Developed system(left), Overview of the drone-based system (center) and Waveform and its frequency
spectrum detected by developed system with drone from rust fracture of steel plate (right).

ACOUSTIC EMISSION WAVE PROPAGATION IN COMPLEXSANDWICH PANELSAHMED HESHAM ABDULAZIZ, PHD
Assistant Professor
Design and Production Engineering Department
Center for Sound, Vibration and Smart Structures (CVS3)
Faculty of Engineering - Ain Shams University - Egypt
Email: ahesham@eng.asu.edu.eg
Website: https://eng.asu.edu.eg/staff/ahesham

Research Spotlight

The honeycomb sandwich panel is usually used in the design of wind turbine blades and aircraft wings due totheir excellent mechanical properties such as stiffness to weight ratio, and high compressive strength. It
consists of two thin stiff plates with embedding aluminium honeycomb core between them. Due to thecomplexity of that structure, it poses many challenges for acoustic emission technique to be used on windturbine blades that consist of such panels. Therefore, it is important to understand the AE wave propagation
mechanism in such structures.
Recently, and through a PhD joint supervision research project between the Center for Sound, Vibration andSmart Structures in Egypt and Cardiff University Structural Performance Laboratory in the UK under thesupervision of Prof Karen Holford and Dr John McCrory, the acoustic emission wave propagation wasstudied on a honeycomb sandwich panel consisted of two uni-directional fiber glass plates and aluminium
honeycomb core. The study was conducted using Hsu-Nielsen technique and laser vibrometry scanning.
Furthermore, the study considered the estimation of AE through-thickness propagation from one plate to theother, which is a real-world monitoring problem for situations where AE instruments are only permitted on
one surface such as inside the airfoil of wind turbine blades.
The results of this study show that the AE wave mechanism is Lamb wave with its distinguished symmetric(So) and asymmetric (Ao) modes. Some wave energy is transmitted through the aluminium honeycomb fromone plate to the other. This causes AE wave energy leakage into the cells and as a result to this phenomenon
the symmetric mode of the Lamb wave attenuation becomes severe. Furthermore, the “Insertion Loss” isintroduced to quantify the effects of thehoneycomb core on the wave propagation.
Interestingly, it is hypothesisedthat this departure from the usual,fiber-direction-dependant velocity
profile of the So mode in the fiber
glass plate is affected by thehoneycomb layer ribbon
direction.

.

Further Reading: Ahmed H
Abdulaziz, Mohamed Hedaya,
Adel Elsabbagh, Karen
Holford, John McCrory,”Acoustic Emission Wave
Propagation in Glass Fibre
Aluminium Honeycomb
Sandwich Structures”, Journalof Composite Structures, vol.
(277), (December 2021).

INTERNATIONAL COLLABORATION:
JAPAN AND TURKEY
THE DEVELOPMENT OF NON-DESTRUCTIVE DAMAGE EVALUATION METHODS FORINSPECTING WATER INFRASTRUCTURE
A joint research project between Japan and Turkey will be fundedby the Japan Society for the Promotion of Science under theFund for the Promotion of Joint International Research:
Fostering Joint International Research program. The research
focuses on the development of non-destructive damage
evaluation methods for inspecting water infrastructure inearthquake prone countries. Acoustic Emission and Machine
Learning methods will be of particular interest in the joint study.

International
Collaboration"Water infrastructure" represented by “agricultural water” and“water and sewage” is an indispensable infrastructure for humansociety. Damage accumulation in these structures may lead to
failure during an earthquake which may result in such problems
as water supply disruptions, agricultural losses, contamination
due to sewage leakage and so on. Therefore, robust and reliabledamage monitoring and detection methods are in need to assess
these structures. For this purpose, laboratory and field tests will
be carried out on concrete by utilizing AE and Machine Learningalgorithms will be used for damage evaluation from AE data.
Numerical studies will also be carried out for simulating the
behavior.
The research team consists of 6 researchers, Prof. Tetsuya Suzuki and Prof. Kazunari
Inaba from Niigata University, Dr. Yuma Shimamoto from Tokyo University ofAgriculture and Technology, Prof. Toshiaki Iida from Iwate University, Japan, Prof.
Ninel Alver and Dr. Sena Tayfur from Ege University, Turkey. The project duration is
40 months starting from December 2021.
Preliminary results ofthe project: Stresslevels estimated by the
random forest method
using clustered AE
activities of freezedamaged Ishikarigawa
concrete samples
under uniaxial
compression tests

UNIVERSITY-INDUSTRY COLLABORATION:UIC AND MISTRAS GROUP
MEMS ACOUSTIC EMISSION SENSORS
Prof. Didem Ozevin received an NSF Partnership for
Innovation Technology Transfer (PFI-TT) funding to bring
MEMS AE sensors into commercial level. Dr. Valery Godinez
from MISTRAS Group is the entrepreneur mentor to develop atechnology transfer plan. Dr. Talha Khan, post-doctoral
researcher at UIC, involved the project as the technical lead.
Mass manufactured, low-cost and low-power MEMS acoustic
device will transform the AE sensing technology into the next

UniversityIndustry
Collaborationlevel. The innovation will be benefitted by installingvoluminous sensors into structural systems for detecting theinitiation and the progression of damage before they become
critical to structural integrity. In this research, the sensors are
manufactured using a thin-film piezoelectric layer sandwiched
between the pad metal layer and the doped silicon layer.
Aluminum nitride is used as the piezoelectric material. New
generation design has the series connection of piezoelectricresonators ranging from 100 kHz to 700 kHz.

New generation multi-frequency
MEM AE Sensor

OPEN ACCESSACOUSTIC EMISSION E-TEXTBOOK
Under the leadership of Dr. Ronnie Miller, a new AE eTextbook is being prepared. The book will have the following
chapters:
Chapter 1. Acoustic Emission Source Mechanisms
Author: Antonios Kontsos
Chapter 2. Wave Propagation in Solids
Author: Joseph Rose
Chapter 3. Finite Element Modeling of Acoustic Emission
Authors: Marvin Hamstad and Markus Sause
Chapter 4. Machine Learning and Data Mining Methods for
Acoustic Emission
Author: Arvin Ebrahimkhanlou
Chapter 5. Acoustic Emission Hardware and Software
Author: Valery Godinez
Chapter 6. Source Location of Acoustic Emission
Author: Ronnie Miller
Chapter 7. Standard Acoustic Emission Applications
Author: Ronnie K. Miller, Ph.D
Available chapters are open to access and review (use Forumsection) at AE e-Textbook

AE e-Textbook

NEWS FROM AE
MANUFACTURERS
The Vallen Systeme Dashboard is an add-on feature to theVallen structure health monitoring solution. It provides
external access to relevant measurement data without
direct log-on to the monitoring- or measurement system.
The automatic data upload to the dashboard server isrealized by Vallen Software VisualAE “Export Processor”
together with an upload program. The Export Processor is
integrated into the powerful and flexible data processing ofVisualAE. The Vallen Dashboard displays the information
in a user-defined layout. The dashboard can be easily
adapted and customized by the user. Information can bedisplayed in bar charts, scatter plots, heat maps, and line
charts. Alarm thresholds can be defined in the dashboard
and notifications about alarms and “on line” status of the
SHM system can be send automatically. Vallen Dashboard
is designed for access by Web browsers on PCs or mobile
devices. It can be hosted
on any Linux Ubuntu server.
Dashboard user management
allows the administrator to
manage the access andconfiguration rights in a
flexible way.

VALLEN SYSTEMEMISTRAS LAUNCHES SENSORIA ™ :A NEW PLATFORM FOR MONITORING
WIND TURBINE ROTOR BLADES
Through Acoustic Emission Technology and theSensoria™ Insights Data-Driven Web Application, Mistras’
Sensoria blade monitor empowers wind turbine blade
operators to gain complete visibility the condition andintegrity of the blades.
Sensoria includes advance AE hardware and newly
developed AE sensors permanently installed on each blade.
Sensoria Identifies different type of damage, visible andhidden, such as lighting strike damage, skin perforations,cracks, and delaminations.
For more Information visit https://sensoriawind.com

MISTRAS GROUPMONITORING BRIDGE SUSPENSIONCABLE AND STEELWORK BY IOT-AE

QINGCHENG AE
INSTITUTE

RAEM1, an IoT-AE system, was installed permanently on several
bridges for monitoring bridge suspension cables and steelwork
health, unattended and on-line 365 days per year. Any single wireof the bridge cable broken will be detected and reported to clientsby cellphone messages and displayed on the cloud server
immediately. The same applies to any steelwork cracking.

MORE INFO PLEASE CONTACT SALES2@AE-NDT.COM, QINGCHENG AE INSTITUTE.

CONFERENCE AND MEETINGS ON AE

Abstract due January 14, 2022
Website: https://www.ewshm2022.com/
Special session on AE

Abstract due March 31, 2022
Website: https://ewgae2022.si/AE DATA REPOSITORY

Create an account: https://figshare.com/
Request access: https://bit.ly/2XFROJx
Wait 3-5 days for access approval
Log in to Figshare and accept invite
Start uploading your data (any file accepted) with respective testing details(examples in Figshare titled 'Monotonic Testing' and 'Compact Tension
Fatigue Testing with AE')

Share & Access AE
Group Data!

CONTACT AEWG
Contact AEWG if you have any comments, questions
and news to share in next issue via email
executive_committee@aewg-us.org