Checking corrosion to prolong the life of metals



Dhiraj Kumar Singh, who grew up in landlocked Ghaziabad, has always been fascinated by the
sea. And so it comes as no surprise that the research project he is pursuing at the IITB-Monash
Research Academy could have a huge bearing on the ocean-worthiness of mammoth structures
in saline water like ships and oil rigs.

Offshore structures susceptible to stress corrosion cracking

The Academy is a collaboration between India and Australia that endeavours to strengthen
scientific relationships between the two countries, and graduate research scholars here study
for a dually-badged PhD from both IIT Bombay and Monash University, spending time at both
institutions to enrich their research experience.

Dhiraj’s project—under the guidance of Prof S K Maiti, Prof Raman Singh, and Prof Tanmay K
Bhandakkar—is called ‘Modelling and Experimental Studies of Hydrogen Assisted Stress
Corrosion Cracking (HASCC) in Steel Weldments’.

HASCC causes premature failure in many metals used in engineering construction, explains
Dhiraj. “It occurs due to the combined effect of corrosion-assisted hydrogen generation and
stress-strain environment in the metal. The assessment of crack growth rate under such
conditions is critical to assess the safety and life of machines and structural components,
particularly in the marine and petrochemicals industries.”

Dhiraj is closely studying the interaction between the evolved hydrogen and the stress-strain
field, so as to be able to predict crack propagation in structural steel and its load-bearing

Finite element based modelling of crack propagation under HASCC

Modelling crack propagation under HASCC is challenging because crack propagation and
hydrogen diffusion influence each other; hydrogen concentration affects the fracture strength
of metal, and the stress field influences the hydrogen diffusion kinetics. The most popular
mechanisms to explain how hydrogen affects the fracture properties of metals are Hydrogen
Enhanced Decohesion (HEDE) and Hydrogen Enhanced Localised Plasticity (HELP).

Steel weldment, on the other hand, presents a complicated problem because of the existence
of three distinct material zones—base metal, heat affected zone (HAZ) and the weld centre. Not
much modelling and experimental studies have been reported in this area, precisely why Dhiraj
is excited.

“Welding has a vital role in engineering construction and is widely employed in the marine
industry, petrochemicals and process plants, hydrogen fuel storage and transportation, etc.” he
says. “Industry can benefit hugely by my work. Not only in design and development, but also to
help prevent catastrophes during operations and work out maintenance schedules. I plan to
propose reliable numerical models for HASCC crack growth prediction. Though experiments
cannot be entirely eliminated, accurate modelling can help reduce them to a significant extent.
This will help industries to predict fracture behaviour of structures quickly at a reduced cost.”

Watching Dhiraj’s progress closely is the Academy’s CEO, Prof Murali Sastry, who says, “The
IITB-Monash Research Academy is an exciting chapter in Indian-Australian relations that will see
both countries creating binding links. This will enable us to tackle the research challenges that
lie ahead and generate some long-lasting high impact outcomes for society. Dhiraj has
exhibited immense potential—he joined our PhD programme with just a BTech qualification.
I’m sure we will hear a lot about his work in the years to come.”

Research scholar: Dhiraj Kumar Singh, IITB-Monash Research Academy

Project title: Modelling and Experimental Studies of Hydrogen Assisted Stress Corrosion
Cracking in Steel Weldments

Supervisors: Prof S K Maiti, Prof Raman Singh, Prof Tanmay K Bhandakkar

Contact details:

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.