We used to hydraulic form stainless steel bellows of many sizes. mainly for the nuclear industry.Quite straightforward .stacked rings with spacers,and capped top and bottom in a press to maintain pressure as diameter increases and hight reduces.

Jason,

I don't suppose I am breaking any secrecy rules, but the method is also used commercially by Rolls Royce for forming the large fan blades on their Trent engine series. Those blades are made in titanium alloy, hot formed and inflated to create the twist and shape on one operation.

Brian

At Vickers Weybridge, there was a 45 gallon drum of water. A male former was placed in the tank, a sheet of Aluminium placed on top of the former, a little bit of plastic explosive and detonator on top of that. Stand well back, boom. Water shot out of the top of the barrel and hey presto , hydraulic forming.
BobH

This topic interests me greatly and I have done a lot of research into the topic. A few days back I purchased a very old textbook from a secondhand book shop that is closing down and came upon an academic tome published in 1908. The contents are the lecture notes for the M.Mech qualification so it is rather heavy going. The chapters on hydraulics were fascinating. The previous chapters covered relative information such as tensile and compression stress of the various materials and the final section gives a worked example of a practical application.

The hydraulic jack required to lift a steel bridge section weighing 1,500 tons through 50 feet was needed to assemble the tubular pipe sections of the Conway Bridge for the railway line. The contractors were Robert Stephenson and Co. The writer runs through the design calculations in great detail and from the data it was shown that a cylinder of some 60 feet in length and having a bore of 1 foot the hydraulic pressure required needed was about 25,000 psi. The barrel wall thickness of course has to withstand this enormous pressure and needed to be 12-inches thick which gave a good safety margin. So basically a cylinder a yard in diameter with a 12-inch bore.

The choice of material was cast iron as this could be poured into a mould. This was done and the bore was machined, didn't say how, but it seemed to be no big problem in those days. The piston and seals were made and tested with the bore for a perfect seal and the whole lot taken to the site. On the first attempt of the lift when the pressure got to about 10,000 psi a problem occurred. Water was p*ssing out everywhere. At first glance it seemed some pipe or coupling was the culprit, but it wasn't the case. On repeating the pressurisation water sprayed out of the side of the barrel, not in one place but all along the barrel like a shower head.

Consultation with Sir (by now Lord) W G Armstrong, the hydraulics expert who had been left out of the loop, gave the answer. Cast iron is too porous and the cylinder should have been made from steel. With a steel cylinder it would only need 6-inch walls to withstand the pressure. This goes to prove that textbooks do have a place as it must have been a costly mistake at the time.