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Meet The Expert: Yanhui Zhang

Mon, 02 November, 2020

Yanhui Zhang is a Consultant in Fatigue Integrity Management at TWI. He joined TWI with a background in metallurgy, having graduated from the University of Science and Technology Beijing in 1982 with a bachelor’s degree, before gaining a PhD from the Open University, UK in 1992.

He worked as a postdoctoral researcher at Cambridge University where he investigated Ni-based superalloys before joining TWI in 2001.

Yanhui’s expertise includes fatigue design, fatigue and creep life evaluation, engineering critical assessment, fatigue and creep testing, and failure investigation. Experienced in establishing relationships between mechanical properties and microstructures of materials, he has published over 60 academic papers in journals and at international conferences, most as the principal investigator.

We took some time to find out more about Yanhui and his work with TWI.

Can you tell us a little bit more about your work with TWI?

As a consultant, I am responsible for developing business, providing consultancy and managing projects for TWI membership companies. Since a large part of our business is associated with the oil and gas sector, my fatigue experience also covers the influence of corrosive environments including seawater, CO2, H2S, H2 and elevated temperatures. Since I joined TWI, I have managed more than 120 projects including three joint industry projects (JIP) and a collaborative project, which had successfully developed a new fatigue damage sensor called the ‘CrackFirst sensor.’

Different from most other companies, TWI provides a lot of research opportunities. I am interested in doing research as I consider this can help provide a better consultancy service to our Industrial Member companies. I supervise several PhD students in collaboration with Cambridge, Brunel, Coventry and Manchester Universities, covering different research topics such as low temperature transformation welds, fatigue performance of welds under variable amplitude loading, and fatigue evaluation of additive manufacturing materials containing defects. I am also happy to help academic journals and international conferences by reviewing the papers submitted. For example, just for the International Journal of Fatigue, I have reviewed 23 papers so far.

In addition, I am also actively involved in standards activities. I am a panel member of several standards committees, including BS 7910 (Guide for Assessing the Acceptability of Flaws in Metallic Structures), BS 7608 (Fatigue Design Guidance for Welded Structures) and BS ISE/101/06 (Fatigue Testing of Metals and Metal Matrix Composites).

Are there any notable projects that you have been involved with since you joined?

I enjoyed working on all the projects I have managed, but the most notable projects, I think, would be the collaborative project, sponsored by DTI, to develop a fatigue damage sensor called ‘CrackFirst.’ It was based on the fracture mechanics concept and several academic and industrial organisations were involved in that investigation. The sensor was successfully developed during that project. It won an award from the Worshipful Company of Scientific Instrument Makers and the sensor was later licenced to the Strainstall company for further development and commercialisation.

Another interesting project was a JIP to investigate fatigue performance of full-scale girth welded pipes at low stress in loading spectrum. A method for fatigue testing of pipes under variable amplitude loading in resonance machines was successfully developed. Based on the results of that project, the slope transition position of the fatigue design curves have been revised in the new version of the British Standard BS 7608:2014.

What are the current challenges with fatigue testing for industry, and how does TWI work to solve these?

Industries always seek fatigue data with a high level of quality. Testing of small specimens is relatively cheap and quick. However, this often involves some assumptions and produces uncertainties in the following fatigue analysis. Examples include the change of local geometry of components and residual stress relaxation when a small specimen is being extracted from a large welded sample. Therefore, full-scale testing is always preferred to simulate the actual loading conditions, either for design or validation, although this often proves to be expensive.

It is a challenge to design and develop full-scale testing capacities for different applications. In response to membership company demands, TWI’s design team had developed many bespoke full-scale testing capacities, including fatigue testing of full-scale pipes, with a diameter up to 36inch, using resonance bend rigs, fatigue testing of full-scale mooring chain lines of large diameters in seawater, full scale testing of polymer lined pipes under different loading conditions involving high strain, internal pressure, cyclic loading and aging at elevated temperature, fatigue testing of full-scale girth-welded pipes in sour environment, and the fatigue testing of full-scale tubular joints under either axial or bend loading.

What is the best thing about working for TWI?

I think it is the mixture of both engineering and research. In addition to solving real problems by managing single client projects, TWI staff also have the opportunity to carry out research through either core research projects (CRP), exploratory projects or collaborative projects. TWI encourages staff to attend international conferences to increase TWI’s reputation in the areas of research, to exchange ideas with colleagues around the world, build networks with other academics and experts in the similar field of studies all around the world, and to share thoughts on recent advances and technological breakthroughs.

Having gone through the academic route and now working at TWI, why do you think it is important for young people to study science and engineering?

Study of science lays a sound foundation for future work. It trains peoples how to use scientific thought, method and inquiry to come to their research and decisions. The study of engineering brings together scientific, creative and problem-solving skills. Studying science and engineering helps young people have a wide range of career choices. Take the area of my work as an example, by studying materials science, people can understand how the microstructure of a metallic material affects fatigue performance, how a fatigue crack can initiate from a component and develop under cyclic loading, and how to mitigate the risk of fatigue failure.

Study of these disciplines also helps to generate curiosity and innovative ideas in work. As a professional engineer, they need to tackle real problems and find the best solutions. It demands creative, imaginative and logical thinking.

Finally, what do you like to do in your spare time away from work?

I used to play badminton twice a week. Given the current COVID-19 situation, we cannot play it now. Instead, I have now started to learn to play saxophone online. I enjoy playing it and I hope I can play with my friends after the coronavirus is over.

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