The 16th biennial Conference on Engineering Structural Integrity Assessment (ESIA16) is fast approaching and, for the first time, is being held online via TEAMS. If you have not already done so, there is still an opportunity to book your place(s) across any or all of three afternoons on October 6, 7, and 8. The conference comprises five invited speakers per day who will be giving presentations on a wide range of topics based around the themes of New and Novel Methods (Oct 6, pm), Challenges and Developments in Various Industries (Oct 7, pm), and Developments Relating to Fatigue (Oct 8, pm). For an overview of the speaking agenda, please download this flyer. To register please visit our ESIA16 events page.
Here, presented in abstract form, is what you can expect from our carefully selected team of structural integrity experts.
October 6
SESSION 1: NEW AND NOVEL METHODS
Chair: Professor Bo Chen
Co-Chair: Dr Yin Jin Janin
Professor Bruce Drinkwater, University of Bristol, UK
What Can Ultrasonic Arrays Tell Us About Cracks?
Ultrasonics is one of the most widely used non-destructive testing methods due to its ability to receive signals from defects hidden deep within engineering structures. This talk reviews the recent dramatic increase in the use of ultrasonic arrays, capable of forming accurate and intuitive images of the interior of the structure. The high resolution now possible in array images means that smaller defects can be detected and their shape extracted. The ever increasing power of computers means that the full matrix capture dataset can be captured and analysed to extract the maximum available information. Of particular importance is the defect scattering behaviour, as this is the fingerprint that encodes the properties of the defect. All this new information then feeds into the structural integrity assessment process, leading to more accurate remaining life predictions.
Dr Zahra Sharif Khodaei, Imperial College London, UK
Structural Health Monitoring in Aerospace
Structural Health Monitoring (SHM) is a remote non-destructive inspection technique that enables instantaneous maintenance request when the system’s health falls below a predefined level of confidence. The concept of SHM is to continuously monitor the state of a structure with permanently installed sensors and allow for maintenance action to be carried out only when a threat to the structures’ integrity is detected. The application of SHM to aircraft structures aims to bring the maintenance from the fleet level to managing individual aircraft’s airworthiness and moving away from the scheduled based maintenance (SBM) to condition-based maintenance (CBM). The potential of SHM has also been recognized for future space missions, to significantly improve the safety and reliability of the flight and lower the cost of re-use vehicles. However, these applications are extremely challenging for two main reasons: the harsh aerospace operational environment and the high level of safety requirements imposed by the aerospace industry. This talk aims to present the developments of the SHM for aerospace application and to address some of the existing challenges and their proposed solutions for the uptake of the SHM systems in real structures under operation.
Professor Erik Schlangen, Delft University of Technology, Netherlands
3D-Printing for Construction at Different Scales
3D printing is the new method for construction of concrete elements and structures. The material to be used for printing is completely different than the conventional concrete for construction. Designing and optimising materials for this purpose with excellent properties during printing, but also in the final product, is still a challenge. Different approaches leading to different final products will be presented as well as methods for improving ductility of the printed material and increasing bond strength between the layers. 3D printing can also be used on a smaller level by printing fibres or micro-reinforcement or creating material shapes and structures with special properties. Several ideas for this will be discussed. The final aspect that will be presented is the use of printing to create smart structures by adding sensing or self-healing capacity to a structure in certain locations.
Professor John Stairmand, Jacobs, UK
The Role of Digital Twins in Structural Integrity
Digital twins technology offers support to the efficient management of complex systems by establishing a digital representation of an asset, and then using that model to support management of the plant by reference to its measured and predicted performance. There are different concepts of how digital twin thinking can be applied to structural integrity, ranging from fundamentally-based predictions of material properties and in-plant degradation, through to coarse system-level representations. The presentation will set out: the benefits of a digital twin approach; case studies of digital twin models that have been developed for the nuclear industry; and caveats regarding what is currently achievable using digital twin representations. The presentation will close by setting out some suggestions for future technology developments to support adoption of digital twin approaches.
Dr Tomas Martin, University of Bristol, UK
Further Understanding of Creep Cavitation Initiation Using Correlative Microscopy
Many important degradation mechanisms for structural integrity start at microscopic defects within a material. For example, creep at high temperatures and stresses begins with the formation of small cavities at grain boundaries and interfaces that evolve over time into larger cracks and eventual failure. The difference in length scale between the initial microstructural feature that initiates the process and the overall size of the component makes it hard to connect the origins of a failure back to its origin. In this talk, recent work using a combination of microscopy techniques, machine learning and correlative datasets will be presented to explore how microstructural observations at nano- and micro-metre length scales can be mapped over millimetre-sized areas, to give insights on the statistical distribution of defects, damage and stresses across a component. A methodology will be described to combine observation of cavities and precipitation from high-resolution electron microscopy and orientation from electron backscatter diffraction, combined with engineering modelling of the stress state. Examples will be shown from ex-service and laboratory creep tests of how combining this microstructural information across larger length scales can give new insights into the formation and evolution of creep cavitation.
October 7
SESSION 2: CHALLENGES AND DEVELOPMENTS IN VARIOUS INDUSTRIES
Chair: Mike Anderson
Co-Chair: Dr Michael Martin
Professor David Nash, University of Strathclyde, UK
Ensuring the Integrity of Endovascular Stent Graft Systems
The challenge of a successful endovascular abdominal aortic aneurysm repair system is to achieve effective long term seating and sealing between the device and the arterial wall. Research over the past 20 years, in partnership with Terumo Aortic, has seen the development of both advanced computational models and robust experimental validation of a ring stent device which exceeds the fatigue performance criterion set by industry and regulatory requirements. In this presentation, Professor Nash will review the approach to stent graft design and outline the steps taken to develop a series of high-fidelity computational models of the system which comprises a series of Nitinol ring bundles linked by fabric which are compacted into a delivery system and thereafter released and deployed into an arterial vessel. The computational approach and finite element models are validated by a series of experiments comprising a saddle-pull load deflection test for the ring stent model, a DIC bend test for the Nitinol material response, micro-CT testing for compaction strain validation and ring stent fatigue testing used to determine the fatigue safety limit. Finally, he will highlight some of the ongoing challenges around patient specific design and in-vivo validation and monitoring.
Professor Roderick Smith, Imperial College London, UK
Structural Integrity and Transport: The Evolving Challenges
Traditionally, focus on structural integrity issues associated with transport have largely been on fatigue, corrosion and wear. This need remains, but the last decade has seen a sharpening of awareness of the far-reaching implications of climate change. The recent train derailment accident at Stonehaven, Scotland, was caused by a landslip obstruction of the line. On the same morning, a major breach of the Union Canal washed away a section of the Edinburgh-Glasgow railway. Monitoring and inspection techniques for structures are now being deployed to anticipate similar occurrences in the future: a difficult, expensive and somewhat hopeless task for the many thousands of kilometers of mostly 150-year-old infrastructure. It could be argued that the same problems beset the road network. Simultaneously, the need to reduce CO2 emissions, increases demand to use new lighter materials in aircraft and to seek alternatives to carbon fuels. Cargo ships, the enablers of global commerce, cause engineering problems of size and construction methods and political problems of international complexities of ownership, flagging, operations, manning and insurance. The common link of this presentation will be the pressures brought upon us by climate change and the multiple consequences of both climate events and our efforts to ameliorate change.
Dr Michael Roy and Dr Yin Jin Janin, TWI, UK
Development of Nagra Nuclear Waste Disposal Canister, Material Selection, Closure Lid Design and Structural Integrity
In the past decade, TWI has been working together with Nagra (the Swiss national cooperative responsible for the disposal of radioactive waste) to develop design concepts for canisters for the disposal of Spent Fuel (SF) and High Level Waste (HLW) in a deep geological repository. The canisters must provide containment of radionuclides for more than 10,000 years. Several different canister designs have been investigated. A forged carbon steel canister is the current reference design. This presentation summarises the work carried out to determine the most appropriate material for canister manufacture, the welding process for the closure weld and the structural integrity performance during long-term disposal. An analytical study on the lid/weld design for the closure weld and final materials selection has been undertaken. The lid and closure weld designs were refined in order to avoid heating the nuclear waste above its allowable temperature during post-weld heat treatment (PWHT). Flaw assessments in accordance with the procedures and guidance given in BS 7910, along with finite element analyses (FEA), were used to identify the most suitable combination of PWHT and lid design such that the required canister lifetime is ensured.
Adam Bannister, HSE Science Division, UK
Structural Integrity Challenges for Re-Purposing the UK’s Gas Network for a Hydrogen Future
Hydrogen has the potential to contribute to decarbonisation targets as it has the capability to deliver low-carbon energy at the required scale. For this to be realised, the suitability of the existing natural gas pipeline networks and infrastructure for transporting hydrogen must be established. An overview of recent work aimed at defining the nature of the challenges and approaches to address these in the UK is given in this presentation. The implications of hydrogen on a range of material types will be covered. The changes in potential mechanisms of failure and examples of the types of components for which ongoing integrity needs to be demonstrated are described. The presentation concludes with some current examples of trials using hydrogen.
Eleanor Crossley, ONR, UK
ONR’s Regulatory Engagements on Advanced Manufacturing from a Structural Integrity Perspective
The UK nuclear industry is constantly evolving, with the possibility of Advanced Nuclear Technologies (ANTs) entering the nuclear industry in the coming years. ANTs include Small Modular Reactors (SMRs) and Advanced Modular Reactors (AMRs), the terms typically used in the UK to refer to Light-Water Reactor (LWR) and Generation IV Small Modular Reactors, respectively. In line with the Nuclear Sector Deal 2018, and the 2020 Energy White Paper, the Office for Nuclear Regulation (ONR) has been building its capability and capacity to regulate ANTs. As part of this programme, ONR has sought familiarisation with a wide range of technologies, and amongst others, the Advanced Manufacturing and Materials (AMM) projects funded by the UK Government Department for Business, Energy and Industrial Strategy (BEIS) through the AMM competition. In this context, advanced manufacturing technologies are considered to be either novel manufacturing technologies or a novel application of a technology in the nuclear industry. This presentation provides a summary of ONR’s regulatory development regarding advanced manufacturing technologies from a structural integrity perspective. The regulatory challenges identified by ONR for advanced manufacturing technologies are discussed.
October 8
SESSION 3: DEVELOPMENTS RELATING TO FATIGUE
Chair: Dr Catrin Davies
Co-Chair: Dr Jack Beswick
Professor Guozheng Kang, Southwest Jiaotong University, China
Uniaxial Rate-Dependent Ratchetting-Fatigue Interaction of Polyamide 6: Experiments and Life Prediction Methods
Rate-dependent whole-life ratchetting and fatigue failure of polyamide 6 (PA6) were explored first by conducting a series of stress-controlled uniaxial fatigue tests at room temperature. The experimental results demonstrate that ratchetting strain rate is sensitive to the variation of prescribed stress rate, and the whole-life ratchetting of PA6 presents a tri-staged evolution feature at high stress rate but a four-staged one at low stress rate. It is found that whether increasing the stress rate will be beneficial or detrimental to the total fatigue life is determined by the competition of resultant strain hardening and self-heating softening. Then, based on the experimental observation, a semi-empirical low-cycle fatigue life prediction model is constructed for PA6, where the stress-rate dependence of fatigue life is considered and a function to describe the nonlinear effect of stress rate on the fatigue life is obtained. The detrimental effect of ratchetting on the fatigue life is characterized by introducing a function of mean stress. Comparison with the experimental data shows that the proposed model presents a good prediction performance. Simultaneously, the neural network method is also used to correlate the low-cycle fatigue data of PA6 with the occurrence of ratchetting. The results show that the established neural network achieves better prediction performance.
Professor Feargal Brennan, University of Strathclyde, UK
The Management of Corrosion Fatigue in Offshore Wind Support Structures
The offshore wind industry has to date been a tremendous success and is now central to UK Government’s Energy plans for the coming decades. The pioneering developments have not been without their challenges and the presentation will discuss some historical issues which continue for legacy installations along with changes to standards and future challenges with a particular focus on corrosion and fatigue. The similarities and differences between offshore wind structures compared to other industries will be explored in the context of corrosion management strategies including inspection, monitoring, fitness for service evaluation and repair. The presentation will also look ahead to developments in the sector not least Power to X.
Dr Yan-hui Zhang, TWI, UK
Very High Cycle Fatigue of Welds and Its Implication to Fatigue Design
In fatigue design of welded components, most design codes/standards introduce a slope change from 3 to 5 at a certain fatigue endurance, which is widely assumed to correspond to N=107 cycles. This is based on the assumption that stress ranges below the slope transition point are not as damaging as predicted from the extrapolated S-N curve derived from data obtained at higher stresses. However, the existing S-N curves in the long life regime are based on deductive reasoning from a limited number of experimental results. This talk presents the results of two studies on fatigue damage of small stresses in loading spectrum: one on welded plates with two different weld details and the other on full-scale girth welded pipes. This presentation also reviews the current fatigue design standards/codes on this issue and discuss their inadequacies in fatigue design in the high cycle fatigue regime. Based on the review and analysis of the data collected, revision to the existing S-N curves to account for the effect of low stress fatigue damage on welded joints is proposed.
Dr Alice Cervellon, ENSMA, France
Orientation Dependence of Ni-Based Superalloys in the Very High Cycle Fatigue Regime
The influence of the crystal primary orientation on the fatigue life of Ni-base single-crystals (SX) superalloys has been studied in the very high cycle regime. Ni-based SX superalloys solidified in three orientations close to the <001>, <110> and <111> directions have been tested under fully-reversed conditions (R=–1) at 20 kHz and 750°C. It is shown that the difference in fatigue life between the <001> and <111> orientations cannot be entirely explained by the octahedral or maximal resolved shear stresses. Fracture surface observations and longitudinal cuts intercepting the main crack initiation site have been performed in order to characterize the crack initiation mechanisms leading to failure. The difference in deformation mechanisms that leads to an orientation effect in the VHCF regime of Ni-based SX superalloys will be presented.
Professor Janice Dulieu-Barton, University of Bristol, UK
Full-Field Imaging Techniques for Integrity Assessment of Composite Structures
Imaging techniques have the potential to revolutionise our approach to engineering design, offering new insight into material and larger system behaviour over a range of length and time scales. The recent relative reduction in cost of the camera systems and increased processing power to handle images, provides the opportunity for the techniques to be deployed at larger scales and realised industrially. A novel integrated imaging and loading system is being commissioned, known as Structures 2025, funded by the UK Engineering and Physical Sciences Research Council. Structures 2025 comprises a reconfigurable system, which can be used for the testing and assessment of a wide range of structures, under both static and fatigue loading. It has the potential to revolutionise traditional approaches to structural testing, certification and validation by providing hi-fidelity measurements in a realistic composite structure. In the presentation the technical steps to develop Structures 2025 are outline along with underpinning case studies that demonstrate the potential of using such a system on composite structures.