I keep meaning to ask. Which solid material has the smallest elastic modulus? This solid material would also have the slowest speed of sound.
Some sort of rubber suggests itself, but which rubber? If possible should be linear elastic with reasonable strength.
Just spotted one web reference that suggested a marshmallow. ?
mollwollfumble said:
Just spotted one web reference that suggested a marshmallow. ?
Wonder what they are like for soundproofing?
Aerogel?
Depending on what you mean by “reasonable” strength I’d guess (from strongest to weakest):
Solid rubber
Rubber foam
Something marshmellowy
Let’s stick to solid rubber for the moment.
According to one silicone supplier it is possible to get down to or below 10 on the “Shore A durometer” scale of hardness. According to wikipedia that translates to 0.05 MPa or less for Young’s modulus. Tensile strength is about 3 MPa. If (which may be possible) it is possible to get 5 on the Shore A scale then that translates to 0.02 MPa for Young’s modulus.
Compare that with about 10000 MPa for Young’s modulus for wood. 0.03 MPa for the Young’s modulus of marshmallow is in the same ballpark. Tensile strength of marshmallow exceeds 0.015 MPa, that’s still in the linear elastic range.
mollwollfumble said:
I keep meaning to ask. Which solid material has the smallest elastic modulus? This solid material would also have the slowest speed of sound.Some sort of rubber suggests itself, but which rubber? If possible should be linear elastic with reasonable strength.
Four applications for this, related.
1) Conveyor belts that stop and start suddenly, such as on supermarket check-outs and brain scan devices. These can have high stop-start accelerations that topple objects on top or cause them to vibrate. Using a low low elastic modulus material would greatly reduce these high accelerations and allow implementation of “critical damping” to get the best possible compromise between acceleration and maximum speed.
2) Robots. Using a material with a low elastic modulus attached to the stepper motor would play a similar role to the low elastic modulus of muscles, tendons and ligaments in animal bodies. Motion would be far less jerky and also with a fully elastic low elastic modulus material could cut robot power consumption for dynamically moving robots (as opposed to piecewise static) by an enormous factor.
3) Feathered flapping wing flying machine. A trouble with feathered flying machines is getting the feathers to rotate to let air through on the upstroke and stop airflow on the downstroke. Attaching the shaft bearing in an elastic material with a very low elastic modulus would allow the rotation to work automatically on air pressure without much loss of energy – the energy is stored on each stroke and then released in the elastic material between strokes.
4) Turbine for a sustainable energy source. When turbine blades are fixed in orientation then they are optimised for a specific wind or water speed. By fixing the blade shafts in a low elastic modulus material they can be designed so that the orientation changes with wind or water speed to close to the optimum orientation without need for any specific motor control of blade angle.