Question

What is the most frequently failed (engineering) product that you have observed in your life? Be specific about your failed product. If you are given a chance to redesign and choose appropriate materials, how would you go about it?

Answer 1

One of the most frequently failed engineering product is "Brake discs" of automobiles.

The most widely used material for the braking system is cast iron. Friction from the brake pads and calipers causes the brake to become less efficient. If they are too worn down, it leads to dangerous brake failure. The possible wear of brakes are due to high temperatures produced due to braking action and compressive force on it. When brakes are applied it creates a layer of gas between the pad and rotor surfaces. Slotting or drilling the rotors helps to evacuate this gas and promote better pad/rotor contact and for the effective working of brakes.

For any vehicle that’s driven on the street and subject to stop-and-go driving, keeping the Brakes cool is an important function. So, the major factors to considered for brake material would be compressive strength, friction coefficient, wear resistance,thermal capacity and specific gravity. As we have already discussed mostly used materials are grey cast iron with a lot number of holes drilled in it.

Carbon/carbon brakes are used in fastest drag cars. This carbon is different from carbon fibers used for body of car panel.It’s a composite material consisting of carbon fibre reinforcement in a matrix of graphite that is very dense and takes extensive heat, pressure and time to form.If these carbon can be made in composite with the ceramics (which have excellent thermal resistant capability) we can acheive a better design of brakes. All though these type of composites are available the are too expensive. So if can produce sheets of these materials (like that of liners in engine cylinders) and develop a process to install them then it would be handy and one will have his own choice of choosing material for his application.