Cryogenic temperature testing

Cryogenic Temperature Tests of Glass Matrix Compositions , 14 Annual Conference on Composites and Advanced Ceramic Materials. Pt 2, Ceramic Engineering and Science Proceedings, vol. 11, Wiley, Hoboken, N. J., Sept. 2008. 

It is possible to design a hydrostatic test in such a way that it probably will be a proof test of the vessel. This usually requires, among other things, that the test be run at a temperature as low as and preferably lower than the minimum operating temperature of the vessel. Proof tests of this type are run on vessels built of ultrahigh-strength steel to operate at cryogenic temperatures. 

Evans et al. [43] carried out 4 MeV electron irradiations of 14 different epoxy resins at 77 K which were selected from a large number of resin systems after screening tests on thermal shock at cryogenic temperatures [44]. The results of flexural tests show that most of these irradiated resins possess only moderate resistance to radiation. Takamura and Kato [45] tried to irradiate the bisphenol-A type epoxy resins with various hardeners at 5 K in a fission reactor and reported that the compressive strength of these epoxy resins decreased sharply after a combined neutron and y-ray irradiation equivalent to a dose of about 107 Gy. 

The research and development efforts on polymer materials for fusion reactors have been intensified in recent years. Some polymers and composites are able to withstand the radiation doses in excess of 108 Gy even at cryogenic temperatures. Furthermore, international research projects on organic insulators used for fusion magnets are currently in progress. As one of the important subjects, the combined effects of intense radiation and thermal cycling are being tested. 

Tests of notched specimens (Figure 26) and determination of notch sensitivity coefficient (K) show that, despite thickness of rolled semiproducts, the Kt coefficient (for a dendritic structure) is less than K2 (for a nondendritic structure) by 20—25% for room and cryogenic temperatures. Thus, K2 > 1.5 for plates and K2 = 1 for thick sheets, which indicates their full insensitivity to a notch. 

For reduced cost and complexity, it is desirable to use commercially available aluminum-fiber pressure vessels for insulated pressure vessels. However, commercially available pressure vessels are not designed for operation at cryogenic temperature. A series of tests has been carried out to verify that commercially available pressure vessels can be operated at cryogenic temperature with no performance losses. All analysis and experiments to date indicate that no significant damage has resulted. Future activities include a demonstration project in which the insulated pressure vessels will be installed and tested on two vehicles. A draft standard will also be generated for obtaining certification for insulated pressure vessels. 

In fact, it is not possible to make the necessary measurements for these tests at temperatures approaching absolute zero. Instead, heat capacity data at cryogenic temperatures (but still well above 0 K) are extrapolated to 0 K and higher temperature data on phase transformations can be used indirectly as shown in Figures 6.7a and 6.7b. This approach is possible because changes in thermodynamic functions of state such as S depend only on the initial and final states, not on the process used to connect these states. 

The data presented in Figs. 5, 6, 7, and 8 should be considered typical of the lovv-tem-perature mechanical properties of commercial 0.005- and O.OlO-in.-diameter Nb-25 %Zr superconductor wires. In view of the difficulties involved in testing extremely small-diameter wires at cryogenic temperatures, as well as the limited number of samples tested, it would be erroneous to consider the data design minima. As design guide information, however, the data are significant. 

Until recently, data on the fatigue behavior of materials at cryogenic temperatures have been sparse, and information of this type for nonmetallic materials has been practically nonexistent. A preliminary search of published data revealed only a limited amount of information on fatigue characteristics of materials at cryogenic temperatures. Most of these data have been derived from flexural fatigue tests, and apply almost exclusively to metals. 

Atiswer by Author No. In order to obtain meaningful data, full size gaskets (12-30 in. dia.) should be tested at cryogenic temperatures. This is expensive and could not be included in a program of this type. Eventually such tests will be conducted. 

Wang SS, Chim ES-M, Socie DF. Stiffness degradation of fiber-reinforced composites under uniaxial tensile, pure torsional, and biaxial fatigue at cryogenic temperature. In Composite materials testing and design. ASTM STP 787 EB 1982. pp. 287-301. 

Shindo Y, Takahashi S, Takeda T, NaritaF, Watanahe. Mixed-mode interlaminar fracture and damage characterization in woven fahric-teinforced glass/epoxy composite laminates at cryogenic temperatures using the finite element and improved test methods. Eng Fract Mech 2008 75 5101-12. http //dx.doi.Org/10.1016/j.engfracmech.2008.07.009. 

Horiguchi K, Shindo Y, Kudo H, Kumagai S. End-notched flexure testing and analysis of mode U interlaminar fiacture behaviour of glass-cloth/epoxy laminates at cryogenic temperatures. J Compos Technol Res 2002 24 239-45. http //dx.doi.org/10.1520/CTR10930J. 

Kang et al. [28] report a space-qualified FBG system that uses FBG sensors to monitor the strains in a filament-wound CFRP tank during pressure testing. Mizutani et al. [27] describes a space-qualified on-board FBG system used to monitor the strain on a CFRP composite LH2 tank installed on a reusable launch vehicle (RLV) test article. The FBG sensors were installed on the CFRP composite tank with UV-cured polyurethane adhesive that showed good performance at cryogenic temperatures. The system (which weighs less than 2 kg) was installed, flown, and tested on the RLV typical recorded data are shown in Figure 16.15. 

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