2. Facets of material behaviour: mechanical behaviour of materials

In the previous blog we talked about how there are various facets to material behaviour. We are interested particularly in the mechanical aspects. What do we mean by the mechanical behaviour of materials?

Basically mechanics is the study of movement of objects. In many situations would like to know where a particular object will be at a later time. For example,  when a football is struck for a pass, we may want to move towards and intercept it during a game. It appears that humans (and most other animals) are very good estimating this movement in many simple cases. However, when the motion of an object is more complicated, such as the path of a person walking on a spinning carousel, a more careful description is required.

As a first step, it was proposed by Newton that the motion of bodies is determined by a quantity called "force" acting on them. To be more precise, the change in velocity of an object in a given time is due to the direction and quantity of the force acting on it. Based on this description it's possible to calculate the positions of objects ranging from trucks on highways to planets in the solar system.

So far we've been talking about the motion of "rigid bodies". That is, while the whole body may move from place to place, the parts of the body don't change their positions relative to each other. Such a process is called the deformation of a body. Bodies do deform quite often and we need to be able to describe that as well. For example, if a basketball is bounced on the ground, it moves without deformation till it touches the ground. During contact with the ground it actually changes shape and becomes flatter. During this time, the parts of the basketball are moving relative to each other and the basketball deforms. The study of such a process is called the Mechanics of Deformable Bodies. 

In the next blog, I will describe how deformable bodies are studied.

From the teacher we learn one part...

This is nice subhashitam (wise saying) in samskritam which I like a lot.

The student learns one fourth from the teacher, and one fourth from own intelligence.

One fourth is learnt from one's friends and a fourth with the passage of time.

This tells us about how we learn. We learn from our teacher. But then we need to continue to think about what we have learnt. Our innate intelligence does some more work for us in this process. We also then need to discuss what we have learnt with our friends and classmates. They will usually say things differently and this gets us thinking and to understanding. Finally, we are able to understand things over time which we may not have at the time of learning. So there is no reason to be frustrated if we can't understand things right away. Also, even if we did think we understood something, we usually get a different perspective and maturity of understanding over time. We need to approach our learning with patience.

1. Facets of material behaviour: introduction

My research area is in understanding the mechanical behaviour of materials. In the course of the next few blogs, I will try to describe what we know and what remains to be studied in this research area.

Materials are the basis of civilisation. In fact, the kinds of materials humans use has even been used to classify the various historical eras of humankind. For example, societies which used primitive stone tools were called Palaeolithic (from Paleo - old + Lithic - stone). They were followed by stone using societies which were more sophisticated and were called Neolithic. These were followed by the bronze ages and Iron Age (from about 1300 BCE). Even now we still use Iron and steel the most. However, the current age is sometimes also called the Silicon age due to the wide use of this material in fabricating computer chips. Steel is still the most common structural material.

We use different facets of material behaviour for various purposes. We may burn materials to obtain heat and their chemical behaviour becomes important then. We may use materials for their ability to reflect light to make mirrors and their optical properties become important. Or we may use materials to keep the cold out and their thermal properties play a key role. Alternatively, we use materials to conduct electricity based on their electrical properties. But, perhaps most importantly, we use materials to support things (tables, chairs, buildings, aeroplanes) and their mechanical behaviour is the important aspect to understand for these purposes.

In each of the above facets of material behaviour, we are constantly trying to do better. Can we get more heat from burning less material? Can the optical properties be made to last longer? Can we keep the cold out with lighter material? And so on. Engineers are constantly looking out for something better all the time.

In the next blog, I will describe some more detailed aspects of the mechanical behaviour of materials and what we are looking for.