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Materials Engineering Group
 


Research / Completed Projects / Jeffery Tan

Jeffery Tan - Finished Project

I am from Malaysia. I recently finished my PhD thesis, it is entitled “Residual stress relaxation in cold-worked holes due to fatigue loading”.

Before I began my PhD, I gained a first degree in Aerospace Engineering at the University of Putra in Malaysia. My current project is of great interest to me as it is a continuation of my degree, specialising in a subject area which is directly related.

 

Choosing The Open University

I am delighted and feel very privileged to study in OU because it provides me the opportunity to work with leading materials scientists in my topic. I believe the OU is the one of the few best places in UK that can offers excellent learning experiences in theoretical, numerical and experimental aspects of materials engineering. The research environment is extremely vibrant coupled with innovative ideas and plenty of industrial-oriented topics. The research facilities such as laboratory equipments, computational codes, analytical softwares and library services are very impressive.

Also, you will be very surprised how friendly OU student community is. You always meet some nice funny people to talk to about interesting things. There are also plenty of social events throughout the year to meet people from different backgrounds and countries – and it is very international!

I enjoy living in Milton Keynes because it provides great quality of life – with lots of green plants on everywhere you go; it is very clean and quiet; excellent red ways for cyclists and pedestrians. Many buildings in the MK City have contemporary architectural designs that are totally different to most other traditional cities in UK . The countryside is pleasantly serene and well conserved.

Research Project

The main aim of my project is to study the effect of residual stress redistribution due to fatigue-aging and crack formation on cold-worked holes in aerospace metals, and how it affects the fatigue life of aerospace structures in services. My research areas include non-destructive stress measurement by neutron, synchrotron X-ray and laboratory X-ray diffraction techniques. This involves travelling to various European countries to use their stress diffractometers.For example, the Engin-X machine at ISIS at Oxfordshire, the X-ray synchrotron ID31 machine at ESRF (The European Synchrotron Radiation Facility) in Grenoble, France, the E3 machine at BENSC (The Berlin Neutron Scattering Center) and the X-ray machines here in the Department.

I am also performing finite element simulations to provide insight into the cold-working process and crack growth of my sample. The finite element data can be very useful to see what happened, and also to complement my experimental results. Within the framework of linear elastic fracture mechanics, I have also developed a generalised Green’s function model. The model is capable of calculate stress intensity factors under biaxial loading, specifically devised for cracked holes (and some other applications in flawed welded plates).

Collaboration

I mainly carry out my research independently under brilliant guidance from my supervisors; I am also collaborating with two American companies: StressWave, Inc in Seattle and South West Research Institute in Texas .

Real-life applications of this project

Compared to conventional mandrel cold-working technology, this novel technique I am studying requires minimal operating cost as 1) it can be easily automated for greater production efficiencies; 2) it eradicates the cost of disposable tooling, thus is environmentally friendly. This new technique is expected to have profound market applications in aircraft, railroads, ground vehicles, medical devices, ships, and industrial machinery.

However, the knowledge of residual stress associated with the fatigue and fracture behaviour in cold-worked fastener holes of this new technology is still limited, although the preliminary laboratory fatigue tests have provided positive results. Therefore I hope my project will provides further scientific insight how this new technique enhance the service life of metallic structures under detrimental fatigue loading.

Research Supervisors Professor Lyndon Edwards and Dr Mike Fitzpatrick


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