Plenary Lecures

Plenary Lecture 1

Wednesday 7th December(Day 1) 10:40 – 11:30 Room A-B


Department of Mechanical Design,
School of Mechanical Engineering,
Pusan National University

Title: Elastic guided wave based NDT/SHM for improvement of material reliability

Abstract : A reliability of all industrial materials relies on maintenance conducted in pre-service and in-service stage. The key to successful maintenance depends on the implementation of reliable inspection technique. A numerous inspection methods from NDT to SHM have been widely applied in various industries. However, there have been many technical challenges for the field application such as accessibility issue and large scale of structure to be inspected and so on. It is highly demanded to develop cost and time effective inspection technique to overcome them. In addition, assurance in data interpretation must be also enhanced. Guided wave based NDT-SHM technique is a promising alternative which is of a great concern. In this presentation, the physical principals of guided wave and various field applications will be presented. Leading edge research fields such as visualization and diagnosis in conjunction with AI will be also introduced.

Biography : Professor Younho Cho was born in Seoul, South Korea. He received his B.S at the department of mechanical engineering, Yonsei University South Korea and M.S subsequently in the graduate school of Yonsei university in the major of fatigue of fracture. He earned Ph.D at the engineering science and mechanics department in the Pennsylvania State University, U. S in major of ultrasonic guided wave NDE/SHM. He is a full professor in the school of mechanical engineering, P(B)usan National University, South Korea. He also spent years at Penn State University and Northwestern University, U.S as research and visiting professors, respectively.
His research includes ultrasonic wave modeling, guided wave tomography, long range NDE/SHM and nonlinear ultrasonic wave applications. He has given keynote and invited speeches via a number of major academic/society meetings in related fields such as the 17th WCNDT (Durban, South Africa, 2012), the 15th APCNDT (Singapore, 2017), FENDT conferences, SPIE, ASA (the Acoustical Society of America) etc. He has served as the president of the 20th WCNDT to be held at Seoul, South Korea in June 2020 and an associate editor for the journal, “Ultraonics” over 7 years. He is a member of executive committee of ICNDT (International Committee of NDT) chairing its WG on “NDE Education and Research” and a board member of ICU (International Congress of Ultrasonics). He is also a vice president and fellow of KSNT (Korean Society for Nondestructive Testing) and a board member of KSME (Korean Society of Mechanical Engineers).

Plenary Lecture 2

Wednesday 7th December(Day 1) 11:30 – 12:20 Room A-B

Masanobu Kubota

Professor and principal investigator,
International Institute for Carbon Neutral Energy Research (WPI-I2CNER),
Kyushu University.

Title : Creep in high temperature hydrogen (Tentative)

Abstract : Virtual zero GHG emission by 2050 is very challenging target. Utilization of high-temperature hydrogen will play a key role in the effort to achieve this ambitious goal. It is known that hydrogen can deteriorate material strength at ambient and sub ambient temperatures (hydrogen embrittlement). On the other hand, there are experimental results and theoretical predictions that no hydrogen embrittlement occurs at high temperature because of weak interaction between hydrogen and defects in the material at high temperature. Nevertheless, reduced creep life in hydrogen at elevated temperature is reported. Regarding the mechanisms that hydrogen affects creep life, it seems that there are no definitive discussions. In this presentation, the result of the creep test of SUS304 austenitic stainless steel and SUY-1 pure iron in hydrogen at 600℃ will be shown. Then, the mechanism of the reduced creep life in hydrogen is discussed based on the examinations of the experimental results and the analysis of an analytical creep deformation model.

Biography : Masanobu Kubota is the professor and principal investigator of the International Institute for Carbon Neutral Energy Research (WPI-I2CNER) at the Kyushu University. He holds Doctor in Engineering from Kyushu University. He worked at the Department of Mechanical Engineering at the Kyushu University as the assistant professor from 1996 until 2010 and the professor from 2010 until 2014. Then, he moved to I2CNER as the professor. He is known for his research on the fracture and fatigue of engineering steels and alloys with current interests focused on hydrogen embrittlement, mitigation of hydrogen embrittlement by gas impurities, creep in high temperature hydrogen and chemomechanical effect under fretting. He received outstanding paper awards in 2005 from the Society of Material Science, Japan and in 2006 from the Japan Society of Mechanical Engineers. Recently, he has devoted to expanding collaboration with other research fields such as theoretical chemistry and material physics and published several hydrogen embrittlement papers with interdisciplinary approach.

Plenary Lecture 3

Thursday 8th December(Day 2) 09:00 – 9:50 Room A-B

Hongjun Yu

Professor and supervisor of PhD students,
Harbin Institute of Technology

Title : Domain-independent interaction integral method for fracture of nonhomogeneous and multi-interface materials

Abstract: In linear elastic fracture mechanics, the stress intensity factors (SIFs) and T-stress are the most important fracture parameters characterizing crack-tip singular stress fields. The conservation integrals such as J-integral, M-integral and L-integral are extremely attractive because they are easily incorporated into the finite element analysis without requiring any special treatment of the crack-tip region. Rice’s J-integral is the most prevalent due to its clear physical meaning and path-independence for homogeneous media. A shortcoming of the J-integral is that it cannot distinguish between contributions due to crack opening and those due to shear for a mixed-mode crack.
In 1977, the concept of the interaction integral is developed based on the J-integral through superimposing a designable auxiliary field on the actual field. With the aid of designability of auxiliary field, mode-I SIF and mode-II SIF can be decoupled easily for a crack in single materials or at a bi-material interface. The implementation of the I-integral mainly experienced three periods. 1) In the last quarter of the twentieth century, the interaction integral was developed for homogeneous materials. 2) In the 2000s, the interaction integral was successfully applied to nonhomogeneous materials. 3) In the past decade, the domain-independent interaction integral (DII-integral) was proposed for multi-interface materials. The DII-integral does not contain material gradients and it is domain independent for material interfaces. Apart from the successful application in linear elastic materials, the interaction integral has been extended to many functional materials with complex interfaces, including piezoelectric materials, magneto-electro-elastic materials, ferroelectrics, ferromagnetics and micropolar materials.

Biography : Hongjun Yu is currently a full professor and supervisor of PhD students at Harbin Institute of Technology. He obtained his B. Sc. Degree (2004), Master (2006) and Ph. D (2010) in engineering mechanics from Harbin Institute of Technology. He worked as a Research Fellow of the Japan Society for the Promotion of Science (JSPS) at Kyoto University (2013-2015) and as an Alexander von Humboldt (AvH) Research Fellow at TU Bergakademie Freiberg (2015-2017). He is focusing on fracture mechanics of nonhomogeneous materials, particulate composites, piezoelectric and ferroelectric materials. He has published more than 50 SCI-papers in the international journals including J. Mech. Phys. Solids, Acta Mater., Int. J. Solids Struct., Mech. Mater., Compos. Sci. Tech., Eur. J. Mech. A-Solids, Eng. Fract. Mech., Int. J. Fract., J. Appl. Mech.-T ASME, Script Mater., Compos. Struct. et al.

Plenary Lecture 4

Thursday 8th December(Day 2) 09:50 – 10:40 Room A-B


Professor (Emeritus)
School of Mechanical Engineering

Yeungnam University

Title : Fretting wear mechanism

Abstract:Fretting, which is a special type of wear problems, is defined as small amplitude tangential oscillation along the contacting interface between two materials. In nuclear power plants, fretting wear caused by flow induced vibration (FIV) can make a serious problem in a U-tube bundle which is located in steam generators and nuclear reactors. Finite element model for elastic contact wear problems were performed to demonstrate the feasibility of the finite element method to the fretting wear problems. Substructure method is also developed based on the verification. The development of a test rig – fretting wear simulator – is demonstrated for the purpose of elucidating the fretting wear behavior under actual conditions of a steam generator in a nuclear power plant, qualitatively and quantitatively. The realistic condition of a steam generator of high temperature up to 300O C, high pressure up to 150 MPa, and water environment could be achieved. Recent approaches such as limiting shape of contact profiles and wear accumulation would be discussed based on contact mechanics. Recent approach of analytic study of fretting wear will be discussed.

Biography:Young S. Chai graduated from the Seoul National University in 1979 where he got a Bachelor degree in a Nuclear Engineering, and, in 1981, received M.S. in Mechanical Engineering from KAIST, Korea. In 1990, he obtained a Ph. D. degree from the University of Texas at Austin in Engineering Mechanics. He has been a professor at School of Mechanical Engineering in Yeungnam University, Korea since 1981. His research interests include friction and wear, stress analysis, and interfacial fracture mechanics. Currently he is a professor emeritus at Yeungnam University, Korea.