Cryogenic structure

Joining materials with different thermal expansion in a cryogenic structure which must stand repeated thermal cycles needs a careful attention to avoid stresses and breaking of the joint. In particular, the vacuum tightness at low temperature may be jeopardized. 

McClintock, R. M., and Hiza, M. J., Epoxy Resins as Cryogenic Structural Adhesives, Modem Plastics, June 1958. 

Vogt, T. Del Valle, H.F. (1994) Calcrets and cryogenic structures in the area of Puerto Madryn (Chubut, Patagonia, Argemtina). Geografiska Annaler 76A, 57-75. 

The high-modulus fibers listed in Table III are of most interest to designers of cryogenic structures. Typical fiber properties illustrate the important differences between the various types. 

L. I. Lysak, in Proceedings of Soviet-American Seminar on the Applied Problems of Low Temperature Materials and the Manufacture of Welded Cryogenic Structures, Kiev, USSR, in press (1978). 

In addition to requirements for the steels and alloys used in cryogenic structures, good weldability requires (1) resistance to metallurgical defects in the weld and heat-affected zone (HAZ), (2) stability of structural and physical-mechanical properties during welding, (3) the development of a special weld alloying system, and (4) the possibility of application of welding joints without post-heat treatment. 

The austenitic class of steels is particularly suitable for cryogenic structures. The main grades are 0X18H10 (similar to AISI 304), 0X17H13M2T (similar to AISI 316), and 0X25H20 (similar to AISI 310) steels. There are modifications of these steels, distinguished by low C or alloyed with N. 

Aluminum alloys are used in all cryogenic structural fabrications. 

In recent years, considerable success has been achieved in the field of the welding of cryogenic materials. Theoretical and practical bases for the solution of various production problems have been developed. Mechanized welding methods and the production of welded cryogenic structures will find many industrial applications. 

The linear elastic (X/c) fracture criterion with its inherent plane strain specimen size limitation cannot produce valid fracture toughness results on tough austenitic materials unless specimens of very large thickness are employed. These, in turn, are not representative of the cross-sectional thickness found in the majority of actual cryogenic structures. Furthermore, if a failure should occur, proper design would cause these structures or components to fail plastically (elastic plastic fracture), as opposed to catastrophically (linear elastic fracture). Therefore, all fracture toughness values were obtained via the elastic plastic (Jjc) fracture criterion and associated resistance curve test technique [ ]. 

SPECIFIC HEATS OF SOME CRYOGENIC STRUCTURAL MATERIALS I—Fe-Ni-BASE... 

Specific Heats of Some Cryogenic Structural Materials I— Fe-Ni-Base Alloys... 

An overall view of the basic tensile-test apparatus is shown in Fig. 1. To eliminate any interaction between the 12-T magnet and the surrounding room-temperature structure, the entire load frame of the tester is fabricated from nonmagnetic stainless steel. The crosshead, shown in the fully raised position in Fig. 1, is supported by two 5.3-m-long, 100-mm-diameter columns. It is raised and lowered by two hydraulic pistons and can be hydraulically clamped to the columns at any position. The column height was made sufficient to allow the cryogenic structure to be raised above the cryostat, the cryostat to be removed, and the structure then lowered back down for the sample to be changed. 

The cryogenic structure takes the sample tensile load in compression on three 38.1-mm-ODx28.6-mm-ID stainless steel cylinders. As shown in Fig. 1, these cylinders extend above the cryostat and return the load directly to the bottom of the crosshead. The sample grips are of the wedge-action type, constructed from 21-6-9 stainless steel. The grips and the cryogenic structure have been proof-tested to 100 kN. 

J. P. Bruner and D. A. Sarno, A Comparison of Three Steels for Cryogenic Service, paper presented at the Soviet-American Seminar on Applied Problems of Lx)w-Temperature Materials and Welding Cryogenic Structures. Kiev, USSR (1976). 

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