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How a Mechanical Engineer Is Powering Through Solid Mechanics

Poonam Kumari. Credit: The Life of Science

Not too long ago, on March 31, 2016, tragedy struck a busy junction in Kolkata. A bridge that was under construction suddenly collapsed, killing 26 and injuring several others. Experts from a fact-finding committee recently stated that it was due to a combination of faulty design, bad quality raw material and inadequate supervision. Dr Poonam Kumari, a researcher in mechanical engineering, who I met at her office in the Indian Institute of Technology, Guwahati (IITG), brought up this episode to stress on how important her field is.

Kumari now works on ‘smart’ materials, especially piezoelectric materials. These are materials that have the property of generating electricity when a load is applied on them. The principle of piezoelectricity is nothing new; it’s likely we have encountered it frequently, whether it is in quartz watches which use the property to keep time, or the microphone in laptops which use it for voice recognition, or ultrasound machines in hospitals.

More recently, piezoelectricity has made news as a clean form of energy. Kumari informed me about a railway station in Tokyo whose displays are powered by people walking on floor tiles that utilise piezoelectricity. There have been reports of similar uses upcoming in the rest of the world, too. “Our analyses can predict how the material will behave if you apply this much pressure – how much voltage will come when different kinds of geometry are used. This topic is still not completely researched.”

The strength of equations

Kumari’s investigations fall under the domain of solid mechanics, the study of how solid materials get stressed and deformed when a load is applied on it. “If we are sitting on a chair, we are applying a load on it,” she elaborated. “[Before it’s usage is okayed,] we have to find out whether this chair will break or not. These are the kind of questions my research area addresses.” For this, she doesn’t need to build hundreds of versions of a solid material to test them against various stresses. She does this all by building mathematical models.

Mathematical models involve a set of ‘governing equations’. Just like a point or a line or a circle can be expressed in the form of an equation based on its position and other characteristics, any solid material too can be described in the form of an equation based on its various features. Let’s say Kumari wants to study how suitable a type of steel is for the aerospace industry. The governing equations that Kumari comes up with will be able to accurately describe how the steel will behave when one or more parameters are tweaked – for example, will the steel hold if it is amalgamated with some new material? The more complex the equation, the more accurate a representation of reality that model is, ie the higher the chances are that the prediction is correct. That’s why Kumari prefers three-dimensional equations. “In 2D and 1D analysis, we make too many assumptions – for example we may assume the thickness is constant… 3D analysis considers the body as a whole – the whole chair, for example. 3D is the closest to experimental,” she said.

Modelling a piezoelectric plate. Credit: The Life of Science

Kumari uses computer languages like FORTRAN and software like MATLAB to make and solve these equations. Each time she solves the equations for a material, she has succeeded in predicting the behaviour of that material. These equations are then used as guidelines on-ground by application engineers who make products with those materials: builders use them to calculate if a 10-storey building will withstand an earthquake, car companies use them to design crash tests, and so on.

During her PhD at IIT Delhi, Kumari worked on her guide’s consultancy project for Bharat Petroleum Corporation Limited (BPCL) who was in the process of installing a giant oil container underground. “It was huge – 70 metres long and 8 metres diameter. The oil would be inside that container under the earth and they needed us to analyse whether it will burst under oil pressure or earth pressure. We optimised the container diameter and length for the given pressure loading and boundary condition.”

The Kolkata bridge collapse is a grim reminder of the need for such collaborations between application engineers and researchers like Kumari. The temptation to compromise on advised procedures and quality of material may be high when deadlines loom, but the price to pay is much worse, as was seen. “These are all important criteria. Accidents happen due to wrong calculations or not following the calculations,” she warned.

I walked out of IITG that evening, with a renewed sense of gratitude for the engineering sciences. Now I knew that my trust in all infrastructure – the floors I walk on, the vehicles I ride in – came from nothing more than blind confidence that the engineers involved in its design got their calculations right, and that the builders were faithful to the guidelines provided to them.

Credit: The Life of Science

Myths about mechanics

According to Kumari, a big misconception about mechanical engineering is that it requires those who pursue it to possess physical strength. What is important is a knack for numbers. “Everything is calculation… there is a lot of numerical work involved and this is the main thing. If someone is good in maths, then they can go for mechanical,” she revealed.

Busting this myth is especially crucial, agreed Kumari, for the sake of young female students who are discouraged from pursuing the field. Since she joined IITG in 2013, there have been only one or two girls in the BTech Mechanical Engineering batches (there is currently one girl in the final year batch and another in the second year batch). “In MTech there are two or three girls, but in PhD we have around 10,” she said. She recalled how she overcame the resistance she faced when she secured admission for mechanical engineering at a college in the town of Bhiwani in Haryana. “Every teacher said ‘oh mechanical is very tough. Don’t go, there are no girls…’. But my principal asked me not to worry. He said maybe here in north India girls don’t prefer this field but if you go to south India, classes are filled with girls. He said nobody resists mechanical and civil in places like Karnataka.”

That’s all it took to reassure the studious Kumari, who had topped her way through school and was eager to lap up more knowledge. “I belong to a village called Manheru near Bhiwani. My father was in the Army. I studied in a government school for girls. I scored well in class 10 and my physics teacher urged me to take up science,” she remembered. That was a somewhat more adventurous choice for Poonam than it is for most of us. “No other student in that school chose science. I was the only student during physics, chemistry and math classes,” she laughed. “There was one chair for the teacher and one for me.”

Kumari continued to buck the trend in her village by choosing to pursue engineering. She claims that the field was still quite foreign to the people in her village. Her Hindi teacher, convinced of her potential, had to visit her home to persuade her parents to send her to college and invest in the relatively expensive course.

When Kumari finally sunk her teeth into the mechanical engineering course, she realised that all the fears were for nothing. “In the first semester, we go to the workshop but that is common across all streams of engineering. Even then, there’s no need to use your own strength na… we only use machines and equipments. It’s nothing special, we just take readings. It’s just like driving a car. Girls can drive cars, can’t they? Is there any difficulty in applying forces? I would like to say that all that matters is that you are good at maths.” And Kumari had no difficulty there since it was the subject she loved the most.

“There is no need to use your own strength in mechanical engineering. We only use machines and equipments to take readings. It’s just like driving a car. Girls can drive cars, can’t they? Is there any difficulty in applying forces?”

Clutching at success

After her BTech in 2004, Kumari did two six-month stints with companies in Gurgaon and Manesar. She is especially proud of her accomplishment at her second job, with a Japanese company FCC Rico, which manufactured clutches for two- and four-wheelers. “They hired me to start the first assembly line with women workers. Until then there were only men who worked in that company on the shopfloor. I recruited and trained 14 girls. I trained them to assemble the clutch and taught them what precautions to take.”

How did that go, I enquired. Kumari’s eyes lit up as she answered, “Can you imagine that our girls’ line was performing better than boys? While the boys assembled 1,500 pieces in a day, we did 1,800! The girls were so happy. Today, I think they are permanent employees there.”

Despite her short but successful run in the private sector, it didn’t take long for Kumari’s academic sensibilities to start tingling again. In 2015, she applied and got selected for an MTech in Applied Mechanics at IIT Delhi, an experience she described as “heaven”. “In the second semester, Professor P.C. Dumir took a lecture on solid mechanics, a subject I used to find difficult till then. He explained it so nicely that I decided that I would do solid mechanics for my MTech project.” Enamoured with this topic, Kumari continued this research as her PhD topic at IIT Delhi. She spent a total of seven years there, from 2005 to 2012, during which her mentors did more than train her technically. “As I was from Haryana, and from Hindi background, my English communication skills were not up to the mark. They guided me and helped me to develop.”

Kumari speaks at the 2017 Steel Congress in London. Credit: The Life of Science

 “They hired me to start the first assembly line with women workers. Until then there were only men who worked in that company on the shopfloor”.

Her guide, Professor S. Kapuria, advised Kumari to further her research with postdoctoral studies. That led her to Simon Fraser University in Canada for a year where she helped investigate why a piezoelectric material was not working as well as expected when used in a hydrogen engine the team was developing. Kumari highlighted how her education and career path is peppered with mentors. “Wherever I went – school or college – teachers were guiding me.”

Family support and gender bias

By the time she went to Canada, Kumari was married and already had her first child. During her year away from family, she came to realise something. “At home, I used to think that my family, children, were a hindrance to my research. But in Canada, though I was alone, I realised that I still could not fully concentrate or work for 16 hours a day just because I had all that time. My family was actually refreshing me. This is required. If not for them, I cannot work.” While in the end of her one-year stint in Canada, she applied for the opening at IITG and returned to join the institute.

Even if they had any initial apprehensions about her unconventional choices, Kumari’s parents were a big support all the way. One of her daughters stays with them and they have guaranteed her childcare support at any point in the future, too.

I asked Kumari if she has ever faced gender bias while on the job. Luckily, she has felt nothing but welcome in academia. She echoed countless other scientists interviewed by The Life of Science when she added that women have to do more work than men to demand the same amount of respect. “In companies, male colleagues may joke that she cannot do physical work,” she smiled. “But who cares about that! I know my capabilities.”

This piece was originally published by The Life of Science. The Wire is happy to support this project by Aashima Dogra and Nandita Jayaraj, who are travelling across India to meet unsung women scientists.