It can be used to calculate the effect of a tiny crack in an aeroplane wing, an iceberg hitting a ship, and even a bullet on a human body.
Peridynamics (PD) is a computational technique to predict and track fractures or cracks in materials such as metals and composites.
It’s still in its infancy in the UK and the University of Strathclyde hosts what's believed to be the world’s first ever Peridynamics Research Centre.
Although the technique is becoming popular in the United States and China, it has yet to gain a real foothold in Europe and the UK. But husband and wife team Dr Erkan Oterkus and Dr Selda Oterkus, Director and Co-Director of the centre within Strathclyde’s Faculty of Engineering, want to change all that.
Erkan, who did his post-doc at NASA Langley and moved to Glasgow in 2012, said: “PD is an emerging research area and Strathclyde is one of the leading places.
“When we started working on PD, there were only a few people in the world working in this area so it turned out that we are pioneers.
“There are some other classic techniques such as Molecular Dynamics (MD) and Finite Element Method (FEM). But one is for too small scale and one is for too large. PDs fits in between and is suitable for all scales. It’s very difficult for people to change their mind sets but we are trying to reach people and say it has advantages with respect to these classical techniques.
Doctors of structures
The word ‘peridynamics’ comes from the combination of two Greek words, with ‘peri’ meaning ‘around’ or ‘surrounding’ and ‘dynamics’ meaning ‘force’.
The continuum mechanics formulation was originally developed by Dr. Stewart Silling in 2000. The intention is that its governing equation is always valid whether there is any discontinuity – like cracks or fracture - in the structure or not.
Selda said: “We are like doctors. But instead of regular doctors who are looking after human beings, we are interested in the health of all types of structures, like aeroplanes, ships and buildings and we want to ensure they are healthy and fit for purpose.”
She says that just like human bodies, these structures can be subjected to external loads and stresses and added: “If you push something, that means you’re applying some loading on that structure and if you push too hard you can break it, it is under stress and can fracture.
“It’s like if you have a cup of cold water, and you put it under hot water, it can crack.
“You can have a cup with a small crack but it doesn’t mean it will break completely but it can propagate under certain conditions.
“With PD, we look at under what conditions this crack will propagate so we can have a full understanding of whether it will cause a problem or not or whether you can safely ignore it, or prevent it getting worse.
“Just one small crack can mean you lose your aeroplane. The implications are massive.”
We are like doctors. But instead of regular doctors who are looking after human beings, we are interested in the health of all types of structures, like aeroplanes, ships and buildings and we want to ensure they are healthy and fit for purpose.
PD can be used to not only assess potential damage to the ship, but to the ice as well, which is also fracturing when it hits the structure.
It’s important to know how it does this so you can make a better prediction of its effect on both sides and ultimately design ships which can withstand collisions which could cause significant damage, even sinking the ship. The obvious one here is of course the Titanic.
Collaborations with industry
Projects at the centre have involved collaborations with industry, with computer controlled simulations as well as the human element used by a team of researchers.
One project has examined how PD can be used to calculate how well ship structures are able to withstand icebergs.
Dr Oterkus, who is also a Reader (Professor) in Marine Structures, and who co-authored the first book on PD which was recently translated and published in Chinese, added: “The problem in using the Arctic region for sailing is that there’s ice there. It may not be a huge amount but even small pieces can cause damage to ships.
"PD can be used to not only assess potential damage to the ship, but to the ice as well, which is also fracturing when it hits the structure.
"It’s important to know how it does this so you can make a better prediction of its effect on both sides and ultimately design ships which can withstand collisions which could cause significant damage, even sinking the ship. The obvious one here is of course the Titanic."
Another project supported by the U.S. Air Force is examining the fundamental aspects of PD.
The centre has a three year ongoing project, which is in its second year.
Erkan added: “In PD there is an important parameter called the horizon. If you imagine that every person in the world is a point and we are somehow interacting with each other.
The horizon parameter is used to determine this range of interaction and the U.S. Air Force specifically asked us to determine the size of the horizon. We are investigating how we can do that, depending on the scenarios.
But the emerging research technique is still to be fully accepted in this country and Selda added: “The UK is still hesitant about using this computational technique and so there are funding challenges, but the applications of PD are enormous.
“It can be used to predict the effect of underwater explosions such as from a mine, and the resultant shock wave that hits your structure, showing how the damage would spread.
“It can be used to calculate the potential damage caused by a missile being fired and could even be used to calculate the damage a bullet would do to a human body.
“It can save lots of money by predicting the effects of corrosion on a structure – from small beginnings, it can spread and cause collapse.”