Strength and sensibility

A metallurgist by training,Ram chose research over a career that would have meant staring at a blast furnace in a steel mill day in and day out. A PhD from Brown University under Subra Suresh—now director of the National Science Foundation,USA—further reinforced his interest in the strength of materials. For several years now,he has been working with esoteric materials that find applications in niche sectors like defence and high-end sports goods—work that earned him the prestigious Shanti Swarup Bhatnagar Prize in the engineering category this year.

Ram drops another cup,this time on a greyish block that looks like sponge but feels rigid like metal. Incredibly,the cup doesn’t break,instead landing with a slight totter and stabilising almost immediately on the surface. This porous aluminium block belongs to a relatively new class of materials called metallic foams and has energy absorbent properties that make it attractive to the automobile and defence industries. When stress is applied to the material,it can compress to a fraction of its size,thereby absorbing the energy of the impact. “Israel wants to use this material to protect their buildings from blast attacks,” says Ram,who has subjected the material to gunshots and other extreme stresses to understand its properties.

His claim to fame,however,is his work on another class of materials known as bulk metallic glasses (BMG),or ‘Liquidmetal’. BMGs are amorphous metal alloys that are stronger than steel and have a high elasticity. When small metal balls are dropped simultaneously on a slab each of BMG,steel and titanium,the balls die out fast on steel and titanium,but keep bouncing for several seconds longer on the BMG,indicating its high resilience. “The very first application of BMG was in golf clubs—in fact,when the first BMG clubs were made,they were banned on the grounds that they gave golfers undue advantage,” says Ram,who has contributed significantly to understanding how BMGs deform and break. Today,BMG finds its pride of place in limited edition Omega watches and Vertu phones. It may one day be used to make intricate jewellery and armour-piercing missile heads,Ram says.

The Department of Materials Engineering at IISc has large test rigs that can generate forces up to 100,000 Newtons (1 Newton is roughly the force of gravity on an apple or a similar-sized object) and small ones that Ram uses for nanoindentation,a process in which a material is poked with a force of something like a millionth of a Newton,resulting in nanometer-sized displacements. Ram has been using this method to study the mechanical properties of biological materials such as bone and dentine but also to understand how pharmaceutical compounds such as aspirin deform. The technique can be used to distinguish between polymorphs—crystal forms with different molecular arrangements. Since only one polymorph is usually approved for use as a drug,nanoindentation could significantly help in quality control in the pharma industry,which now uses x-ray crystallography to study atomic structure. Says Vikram Jayaram,chair of the department,“People are discovering that the mechanical response of cells and tissues tells us a lot about their function or lack thereof. Ram has used very powerful,small scale methods of poking things that allow him to probe the response on a scale of a few nanometers. In the context of the exploding field of bio-engineering,this may be the

way forward.”