Monday, July 22, 2024
Zhongqing Su, Ph.D.
Chair Professor of Intelligent Structures and Systems
Head of Department of Mechanical Engineering
The Hong Kong Polytechnic University
Plenary Title: Femtosecond Laser-enabled Nondestructive Material Characterization and Applications in Picosecond Acoustofluidics
Abstract: Path-breaking advances in ultrafast laser technology have shed new light on optical–acoustic coupling and opened up intriguing application prospects. In this talk, we will report on a new nondestructive evaluation framework based on ultrafast laser ultrasonics, from fundamental theory to implementation details. Making use of the ultrashort acoustic wavelength of laser-generated ultrasound, the femtosecond-laser-enabled ultrasonics techniques have enabled super high-resolution material characterization at the nanoscale. The approach has been experimentally demonstrated by characterizing the monocrystalline semiconductor wafers which are of a high degree of anisotropy, and imaging interior features of an opaque, stacked micro-system, three-dimensionally and contactlessly. In addition, we also present some new application paradigms of the ultrafast laser in picosecond acoustofluidics research. We develop a photoacoustic tweezer, integrating the merits from optical and acoustic tweezers. Via a transient thermoelastic coupling, the pulsed ultrafast laser irradiates a substrate through liquid, to trigger ring-shaped travelling photoacoustic waves and generate acoustic radiation forces for manipulating tiny particles in the liquid, also in a noncontact manner.
Biography: Prof. Zhongqing Su is the Chair Professor of Intelligent Structures and Systems and Head of the Department of Mechanical Engineering at The Hong Kong Polytechnic University (PolyU). He is the current Editor-in-Chief of the journal Ultrasonics, holds the Changjiang Chair Professorship, and has been the Vice President of the Hong Kong Society of Theoretical and Applied Mechanics since 2023. He is an elected Distinguished Fellow of the International Institute of Acoustics and Vibration. He earned his PhD in 2004 from the School of Aerospace, Mechanical and Mechatronic Engineering at The University of Sydney, Australia, where he also completed his postdoctoral training under the "Australian Research Council – Australian Postdoctoral Fellowship" before he joined PolyU. His research interests span the area of ultrasonics, structural health monitoring (SHM), wave propagation, nondestructive evaluation, smart materials and advanced composites. He was/is the Chair of a number of key international conferences in the field, including the 7th Asia-Pacific Workshop on SHM (Hong Kong, 2018), the SPIE Conference on Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2023 (Long Beach, the United States, 2023), and the SPIE Conference on Health Monitoring of Structural and Biological Systems XVIII (Long Beach, the United States, 2024).
Tuesday, July 23, 2024
Christian Boller
Chair of NDT & Quality Assurance (LZfPQ)
Saarland University
Plenary Title: Living with Degradation without Compromising Integrity - or The Increasing Significance of NDE in Structural Mechanics
Abstract: Non-Destructive Testing (NDT) followed by Non-Destructive Evaluation (NDE) is a field of science being comparatively younger than structural mechanics. Driven by physics in general and here specifically solid-state physics and electromagnetism NDT has developed not only as a technique but also as a science of which structural engineering and hence structural mechanics has gradually taken advantage of. The first step in that regard has been the detection of damage such as cracks, which is the most common application of NDT today. This has allowed cracks and hence degradation in engineering structures to be tracked from a specific detectable crack size onwards. In combination with fracture mechanics NDT has allowed the Damage Tolerance (DT) principle to be introduced. The DT principle has become one of the most important pillars of light weight design, specifically in aviation, and this despite the significant effort and cost involved. "Living with cracks without compromising structural integrity" became a reality as a principle about 75 years ago and with this a significance of NDT. NDT has had originally two major roles: 1) The detection of degradation (i.e. cracks) and 2) The characterization of materials in terms of production quality control. The combination with fracture mechanics has allowed prognostics to be performed and with this the aspect of evaluation, being the incubation of what we consider NDE to be today. Further disciplines of increasing importance for NDE over the past decades has been sensor technology and computation science. With this, visions are on the way to become reality, which are headed under expressions of Structural Health Monitoring (SHM) and NDE 4.0.
The significance of NDT/NDE in structural mechanics is not limited to light weight design only. Where light weight design has rather a secondary importance is in civil engineering. However, even here NDT/NDE gains significantly importance. A major reason for this is the fact that the original design life of civil infrastructure is set to 50 or maybe 100 years. However, regular visual inspections reveal that much of this infrastructure looks still to be in good shape when reaching this design life and replacement might not be advisable for economic as well as environmental reasons. The infrastructure may therefore have an additional operational potential compared to what was originally assumed during design. To take advantage of this potential much of this infrastructure is therefore "redesigned" and this with the help of NDT/NDE and the introduction of DT principles. Furthermore, advanced NDT/NDE is not limited to the detection of material separation or material loss only but also allows other mechanisms of material degradation to be evaluated such as plasticity, martensitic transformation, or dislocation movements. With this a new scale of quantification of materials’ degradation is on the way to be introduced, which further enhances the potential of prognostics and hence the application of the DT principle.
After a general view regarding the interaction of NDT/NDE and structural mechanics the presentation will give some practical examples on how to get the different disciplines involved merged to what is currently described as NDE 4.0 as a concept. It will further address various issues faced and likely to be solved when looking at the practical application of structural integrity assessment, not just for traditional metals but also for other material types being applied.
Biography: Prof. Dr.-Ing. Christian Boller studied civil engineering at the Technical University of Darmstadt/Germany and received an engineering doctoral degree in the field of material mechanics and fatigue life evaluation from the same institution in 1987. Having been active in the field of materials technology at Battelle-Europe in Frankfurt/Germany for a few years, he moved into the aircraft development division of MBB Military Aircraft (today Airbus) in 1990, where he became the chief engineer aerostructures in 1998. In 2003 he was appointed the chair of 'Smart Structural Design' at the University of Sheffield/UK. From 2008 until 2020 he was director of Fraunhofer IZFP. Since 2008 he holds the chair for Non-Destructive Testing and Quality Assurance (LZfPQ) at Saarland University. He is also the director of the NDT master course programme at Dresden International University (DIU) since 2013. In 2014 he was appointed a visiting professorship at the School of Aeronautics of Nanjing University of Aeronautics and Astronautics (NUAA) in Nanjing/China. He is the author and co-author of more than 300 publications including "Materials Data for Cyclic Loading" (1987) and "Encyclopaedia on Structural Health Monitoring" (2008) both a 5- volume compendium each. He is also one of the central organizers of the "European Workshop on Structural Health Monitoring" and the "Symposium on NDT in Aerospace".
Wednesday, July 24, 2024
Eric L. Jones, Ph.D
Chief, Materials State Awareness Branch
Materials & Manufacturing Directorate
Air Force Research Laboratory
Plenary Title: Material State Awareness – Challenges & Opportunities from the DAF Perspective
Abstract: In the 1970s, the Air Force incorporated a damage tolerance approach in its structural integrity programs to estimate the remaining life and/or calculate risk for structural components on aircraft. Nondestructive evaluation/inspection (NDE/I) methods have been successfully used to detect damage before it grows to a critical size which makes the damage tolerance approach possible. The damage tolerance approach is the cornerstone for ensuring the safety of the Air Force fleet. While NDE/I techniques for traditional aerospace materials (composites, metals) are well established, demands for future system capabilities require emerging materials such as high temperature composites, refractory metals, and additively manufactured polymers and metals. In addition, to streamline aircraft manufacturing there is a push to use bonded composite structures and joints. These emerging materials create a challenge as they have not been used extensively in structural applications of current platforms, therefore the development of new NDE/I approaches will be needed to understand the material state. The Materials State Awareness (MSA) Branch of the Materials and Manufacturing Directorate of the Air Force Research Laboratory (AFRL) is developing nondestructive capabilities to assess the degradation of these emerging materials. The foundation of the MSA Branch's research activities is nondestructive characterization, advanced signal processing and data analytics, and material validation which is all integrated to create a model-enabled materials representation to understand the material state. The overview will highlight previous successful NDE/I technology developments as well as a synopsis of current technical initiatives led by the MSA Branch. The overview will also address the strengths and limitations of current nondestructive techniques and the developments being planned to ensure they can address the challenges as emerging materials are introduced to the DAF fleet.
Biography: Dr. Eric Jones is the Chief for the Materials State Awareness Branch, Composite, Ceramic, Metallic, and Materials Performance Division, Materials and Manufacturing Directorate, Air Force Research Laboratory, Air Force Materiel Command, Wright-Patterson Air Force Base, Ohio. Dr. Jones leads the development, demonstration, and transition of nondestructive evaluation (NDE) methods for Air Force and Space Force applications. His research interests and technical experience includes microstructure/property relationships of ceramic matrix composites (CMC); full field strain measurement techniques (DIC) to determine damage evolution in CMCs; and oxidation of ultra-high temperature ceramics (UHTC) using laser heating. Dr. Jones received a Bachelor of Science, Masters, and Ph.D. in mechanical engineering from North Carolina A&T State University. He is a member of technical societies to include the American Society of Mechanical Engineers (ASME) and the American Ceramic Society (ACerS) and has been a past participant in the CMH-17 CMC Working Group.