Question

What properties are desirable when designing a spinal implant? What about for the outer casing of a submarine?

Answer 1

Spinal implants have been manufactured from titanium alloys and polyetheretherkrtone(PEEK) .Titanium alloys are preferred for spinalimplants because of their superior biocampatabilitry and MRI compatability.ASTM F1717,ASTM F 2077 and ASTM f 2267 are the specific technical references for the design validation of spinal implants.As per the standards the only required loading conditiuons are compression and torsion loads while the bending moments of flexion extension and lateral movements are important for the biomechanical evaluation of spinal implants.Spinal implants are used to stabilize the unstable spine caused by trauma or degenerative intervertebral disk.Recently vanadium free CP titanium is being used for spinal implants.

The outer part of the submarine is called as outer casing or outer hull or light hull which actually forms the shape of the submarine.Most submarine have two hulls ,one is inside and other is outside.The outer hull is waterproof,and the innerhull is called as pressure hull.Pressure hull of a submarine maintains the integrity with the difference between outside and inside pressure at depth.The pressure hull is generally made of thick high strength steel. The light hull or outer hull is usually made of thin steel plates,as it has same pressure on both the sides.The outer case is waterproof.The outer case can be used to mount equipments,which if attached directly to the pressure hull could cause unnecessary stress.If the submarine is damaged,the light hull takes some of the damage and doesnot compromise the vessels integrity as long as the pressure hull is intact.