Factor of Safety in Natural Systems
Duration: 4 hours
Target Audience: Engineers, product designers, R&D managers, corporate heads
Factor of safety in design is a dimensionless number which is the ratio of material strength to design load. Nature's designs are based on "principle of generosity", not on "principle of economy". Two eyes, two ears, ten thousand taste buds, decoupling of cochlea and vestibular canals, two kidneys are all based on a factor of safety of 2 or more. Brain is designed on a principle of redundancy. There were people who lived even when their brains were damaged much. In the case of human heart, the motor-pump set that works non-stop for about 70 years, the factor of safety is enormous. For example. in the case of heart, factor of safety is built in the following ways:
- Atriums contract in case of disease narrows valve openings.
- Left ventricle keeps pumping even if 50% of its muscle mass is dead.
- Right ventricle can be completely dispensed with; still blood will flow to the lungs.
- If valves become leaky, heart pumps harder to compensate (Hydraulics).
- If the valves are leaky, heart pumps extra blood to compensate.
- Valves can be dispensed with: The pumping action is to move the blood forward, rather than backward.
- In case of low blood flow, sympathetic nerves and hormones may spur the heart muscle to pump more.
- If SA node fails, AN node takes over.
Outline of Lecture
In this lecture, the concept of factory of safety, and the principle of generosity will be illustrated with various examples from nature.