Have you ever wondered how Emma Maersk, one of the world’s largest cargo ships, is able to withstand the fury of the ocean for decades without breaking down?
Or steel components used in power plants like steam generators, condensers and fuel cladding in nuclear reactors are able to withstand corrosion, which could lead to catastrophe?
The mega-ship, and many such engineering structures, spanning across different industries, are built to beat the ever-aggressive operating conditions with specialised materials and technologies.
Even so, the materials, many a times purpose-built, are not immune to damage. Hydrogen, ubiquitously present in environments, is one of the main constituents that accelerates damage. The damage occurs silently, even stealthily, and is furthered by corroding media and operating loads on the structures. This condition is termed as hydrogen assisted stress corrosion cracking (HASCC).
HASCC can lead to catastrophic failures without any notice or warning. It is practically impossible to keep hydrogen out of most materials, since it readily finds its way in either during manufacture (welding, casting, heat-treatment, electro-plating) or service (process gas, by-product of corrosion reaction).
The challenge, then, is to minimise, and if possible, eliminate hydrogen assisted stress corrosion cracking altogether. And Nilesh Raykar, a Research Scholar at the IITB-Monash Research Academy, is a man who relishes a challenge.
“Any advancement in the understanding of HASCC that can lead to the mitigation of the process or prediction of rate of growth of damage will have tremendous utility,” says Raykar, “which is what motivated me to take up a project, titled ‘Towards improved modelling of crack growth during hydrogen assisted stress corrosion cracking’ under the guidance of Professor S K Maiti from IIT Bombay, and Professor Raman Singh from Monash University.”
The IITB-Monash Research Academy, also known as the Academy, is a graduate research school located in Mumbai, India. It opened in 2008 as a joint venture between the Indian Institute of Technology, Bombay and Monash University. Students of the Academy study for a dual PhD from both institutions, spending time in both India and Australia, with supervisors from both IITB and Monash. The establishment of the Academy marks the first time that an Australian university has set up an extensive physical presence of this kind and scale in India.
“Strategies to control damage due to HASCC,” says Raykar, “involve mathematical formulation of the underlying physical processes—electrochemical reaction, hydrogen transport and crack propagation—and its solution through analytical or numerical techniques. These models are tailored to predict the load below which no crack growth occurs, or to estimate the crack growth rate to assess remaining life of a damaged component.”
Raykar’s research aims at providing a computational tool that can help estimate remaining life much quicker than is currently possible. He is confident that his research findings can be utilised at the design stage for reliability, as well as during service for remaining life estimation of the fabricated products.
As his research progressed, what Raykar found challenging and exciting in equal measure was that the study was interdisciplinary—it called for learning and understanding HASCC from the viewpoint of material science, chemistry, stress analysis, fracture mechanics, and computational mechanics.“The pain of designing and building the experimental set-up and the tensions and frustrations during the journey of developing the theoretical solutions were overwhelmed at the end by the joy of discovering hidden unity amongst the plethora of test results, unravelling of the truth behind the process and, above all, getting recognition from peers.”
Raykar has a wealth of work experience, and looks back fondly at the 19 years he spent in the product design department of a major Indian multinational engineering company, involved in manufacturing of world-class heavy-engineering equipment for the fertiliser and petrochemical industry. “Back then, we faced many corrosion-related issues. Most of these problems had no permanent solution due to a lack of understanding of the underlying mechanisms. So when I got a chance to conduct research in this field, I jumped at the opportunity.”
Will models such as these then lead to an improved engineering of Emma Maersk to combat the rage of the oceans? “Yes,” says Raykar, who is understandably excited about what the future holds. “The results from the work are encouraging enough to boost our confidence in an improved capability for prediction of the damage suffered by the critical structures. The improved model will be beneficial to a host of industries combatting HASCC, like marine, aviation, petrochemical and fertiliser process plants, and the nuclear and power sectors.”
So, go on, then take your next vacation on that cruise ship you always wanted to sail. And, when you find the vessel effortlessly negotiating the treacherous swells in the high seas, do remember to doff a hat to researchers like Raykar.
Research scholar: Nilesh Raykar, IITB-Monash Research Academy
Project title: Towards improved modelling of crack growth during hydrogen assisted stress corrosion cracking
Supervisors: Professor S K Maity, IIT Bombay and Professor Raman Singh, Monash University
Contact details: firstname.lastname@example.org
The above story was written by Mr Krishna Warrier based on inputs from the research student and IITB-Monash Research Academy. Copyright IITB-Monash Research Academy.