Tag Archives: screw threads

Reasons I became an engineer: #3

Decorative image of photoelastic fringe pattern in section of jet engine componentThis is third in a series of posts reflecting on my path to becoming an engineer.  In the previous one, I described how I left the Royal Navy and became a research assistant at the University of Sheffield in the Department of Mechanical Engineering [see ‘Reasons I became an engineer: #2’ on May 3rd, 2023].  My choice of research topic was dictated by the need for a job because I had to buy myself out of the Royal Navy after they had sponsored my undergraduate degree and I needed a salary to allow me to make the monthly payments.  So, I accepted the first job that was offered when I went back to the University to talk about my options.  I worked on investigating the load and stress distributions in threaded connections with a view to designing bolted joints that would be lighter, stronger and with a longer life.  We used a combination of finite element modelling [see ‘Did cubism inspire engineering analysis?’ on January 25th 2017] and three-dimensional photoelasticity, which is an experimental technique that has fallen out of fashion [see ‘Art and Experimental Mechanics’ on July 17th, 2012].  I was fortunate because all of my work as a research assistant went into my PhD thesis which although not ground-breaking resulted in several journal papers [see ’35 years later and still working on a PhD thesis’ on September 16th 2020] and, with the help of personal contacts, a post-doctoral fellowship at the Medical School at the University of Calgary, Canada.  In Calgary, I worked on the design of experiments to measure the stress in the pericardium, which is a sac that surrounds the heart – still engineering but a major shift in focus from industrially-focussed mechanical engineering toward biomedical engineering.

Image: Fringe pattern in section of photoelastic model of jet engine showing distribution of stress from Patterson EA, Brailly P & Taroni M, High frequency quantitative photoelasticity applied to jet engine components, Experimental Mechanics, 46(6):661-668, 2006.

Turning the screw in dentistry

Dental implant surgery showing implant being screwed into placeTwo weeks ago, I wrote about supervising PhD students and my own PhD thesis [‘35 years later and still working on a PhD thesis‘ on September 16th, 2020].  The tedium of collecting data as a PhD student without digital instrumentation stimulated me to work subsequently on automation in experimental mechanics which ultimately led to projects like INSTRUCTIVE and DIMES.  In INSTRUCTIVE we developed  low-cost digital sensors for tracking damage in components; while in DIMES we are transitioning the technology into the industrial environment using tests on full-scale aircraft systems as demonstrators.  However, my research in automating and digitising measurements in experimental mechanics has not generated my most cited publications; instead, my two most cited papers describe the development and application of results in my PhD thesis to osseointegrated dental implants.  One, published in 1994, describes the ‘Tightening characteristics for screwed joints in osseointegrated dental implants‘; while, the other published two years earlier provides a ‘Theoretical analysis of the fatigue life of fixture screws in osseointegrated dental implants‘.  In other words, the former tells you how to tighten the screws so that the implants do not come loose and the latter how long the screws will survive before they need to be replaced – both quite useful pieces of information for dentists which perhaps explains their continued popularity.

Statistics footnote: my two most cited papers received five times as many citations in the last 18 months and also since publication than the most popular paper from my PhD thesis. The details of the three papers are given below:

Burguete, R.L., Johns, R.B., King, T. and Patterson, E.A., 1994. Tightening characteristics for screwed joints in osseointegrated dental implants. Journal of Prosthetic Dentistry, 71(6), pp.592-599.

Patterson, E.A. and Johns, R.B., 1992. Theoretical analysis of the fatigue life of fixture screws in osseointegrated dental implants. The International journal of oral & maxillofacial implants, 7(1), p.26.

Kenny, B. and Patterson, E.A., 1985. Load and stress distribution in screw threads. Experimental Mechanics, 25(3), pp.208-213.

Logos of Clean Sky 2 and EUThe INSTRUCTIVE and DIMES projects have received funding from the Clean Sky 2 Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme under grant agreements No. 685777 and No. 820951 respectively.

The opinions expressed in this blog post reflect only the author’s view and the Clean Sky 2 Joint Undertaking is not responsible for any use that may be made of the information it contains.

Image by володимир волощак from Pixabay.