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Doctoral Defence Success for Changyi Yu

Mon, 26 September, 2022

NSIRC and Coventry University PhD Candidate Changyi Yu has passed his Doctoral Defence / PhD Viva.

Changyi's research aimed to develop a procedure to quantify the windows for polyethylene (PE) pipes and to eliminate the need for fusibility tests. The same method would also be used to quantify the level of windows in high-density PE (HDPE) pipes.

‘Effect of Insufficient Homogenisation during the Extrusion of Polyethylene Pipes on Butt Fusion Joint Integrity’

The main reason PE pipe material might not be of the required quality is insufficient homogenisation of pigmented resin, which results in features called ‘windows’. These windows are areas where there is a lack of carbon black.

Due to insufficient mixing of carbon black and HDPE, windows are categorised under one of the defects in HDPE pipes.

During the project, Changyi focused on analysing the failure mechanism of windows which influences the mechanical integrity of the HDPE pipe and butt fusion joints at the microscale level.

In addition, the research attempted to determine a critical window concentration level below which the mechanical integrity of the butt fusion joints is sufficient for industry applications.

Changyi Yu presents to Coventry University senior academics during a visit to TWI headquarters near Cambridge, UK. Photo: TWI Ltd
Changyi Yu presents to Coventry University senior academics during a visit to TWI headquarters near Cambridge, UK. Photo: TWI Ltd

By using image analysis for window quantifications, the results of the study provided a kind of defect in HDPE pipes which is currently ignored by the pipe industry, and gives a method to quantify the defects.

I appreciate all efforts and support given to me, especially by my academic and industrial supervisors. All colleagues in my section at TWI and the NSIRC staff were friendly and helpful

Changyi Yu

Changyi joined the Structural Integrity PhD programme in 2018 with supervision from Prof Xiang Zhang at Coventry University. He also received industrial supervision from Dr Amir Khamsehnezhad and Dr Mike Troughton from TWI Ltd. Funding support was provided by the TWI Core Research Programme.

Before beginning his journey as a PhD Student, Changyi graduated with BEng (Hons.) from Beijing University of Chemical Technology, before going on to complete an MSc in Polymer/Plastics Engineering with Loughborough University in the United Kingdom.

You can request more information about Changyi's industry focused research by contact us via email.

Visit the PhD Programme page to find out more about the course and view the latest opportunities.