Investigations For The Development Of A Single Use Shape Memory Alloy Spacecraft Valve PDF Download

It is shown that NiTi shape memory alloys are sensitive to thermal cycling above As and irradiation with neutrons and protons under certain conditions. The effects are highly depending on the material composition and the thermal treatment. Cycling and irradiation are decreasing and thermal aging is increasing the phase transformation temperatures. The design of the NO valve is closely oriented on the NC design with the only exception of a new designed notched pipe to be able to implement a sealing solution. The sealing solutions are selected as a combination of a soft and hard sealing partner. This is either realized by using synthetic materials or a soft metal coating. The only suitable solution for coating titanium is found to be an intermediate layer out of platinum and a final layer of gold. This is creating the problem of the combination of dissimilar metals which can be resulting in a galvanic corrosion effect. The characterization of the actuators is showing that the behavior is an a range which was expected from earlier tests. There is one new effect at the stress free elongation during the first cycle. The actuators are showing a negative two way effect which has to be investigated further. The results of the first screening of the sealing solutions showed surprising results. The synthetic poppets showed the best results with the only drawback of the lack in compatibility. The titanium solution achieved great results and might be a promising candidate after it is improved. With the gold coated poppet it was not possible to achieve sufficient leakage rates. It is therefore necessary to improve the coated surface to reach better sealing capabilities.*****It is shown that NiTi shape memory alloys are sensitive to thermal cycling above As and irradiation with neutrons and protons under certain conditions. The effects are highly depending on the material composition and the thermal treatment. Cycling and irradiation are decreasing and thermal aging is increasing the phase transformation temperatures. The design of the NO valve is closely oriented on the NC design with the only exception of a new designed notched pipe to be able to implement a sealing solution. The sealing solutions are selected as a combination of a soft and hard sealing partner. This is either realized by using synthetic materials or a soft metal coating. The only suitable solution for coating titanium is found to be an intermediate layer out of platinum and a final layer of gold. This is creating the problem of the combination of dissimilar metals which can be resulting in a galvanic corrosion effect. The characterization of the actuators is showing that the behavior is an a range which was expected from earlier tests. There is one new effect at the stress free elongation during the first cycle. The actuators are showing a negative two way effect which has to be investigated further. The results of the first screening of the sealing solutions showed surprising results. The synthetic poppets showed the best results with the only drawback of the lack in compatibility. The titanium solution achieved great results and might be a promising candidate after it is improved. With the gold coated poppet it was not possible to achieve sufficient leakage rates. It is therefore necessary to improve the coated surface to reach better sealing capabilities.