Fatigue tests and life estimation of Incoloy alloy 908

Journal Article · Sun Jun 01 04:00:00 EDT 1997 · Advances in Cryogenic Engineering

OSTI ID:476726

Feng, J; Toma, L S; Jang, C H; Steeves, M M ^[1]

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1. Massachusetts Institute of Technology, Cambridge, MA (United States)

Incoloy{reg_sign} alloy 908* is a candidate conduit material for Nb{sub 3}Sn cable-in-conduit superconductors. The conduit is expected to experience cyclic loads at 4 K. Fatigue fracture of the conduit is one possible failure mode. So far, fatigue life has been estimated from fatigue crack growth data, which provide conservative results. The more traditional practice of life estimation using S-N curves has not been done for alloy 908 due to a lack of data at room and cryogenic temperatures. This paper presents a series of fatigue test results in response to this need. Tests were performed in reversed bending, rotating bending, and uniaxial fatigue machines. The test matrix included different heat treatments, two load ratios (R=-1 and 0.1), two temperatures (298 and 77 K), and two orientations (longitudinal and transverse). As expected, there is a semi-log linear relation between the applied stress and fatigue life above an applied stress (e.g., 310 MPa for tests at 298 K and R=-1). Below this stress the curves show an endurance limit. The aged and cold-worked materials have longer fatigue lives and higher endurance limits than the others. Different orientations have no apparent effect on life. Cryogenic temperature results in a much high fatigue life than room temperature. A higher tensile mean stress gives shorter fatigue life. It was also found that the fatigue lives of the reversed bending specimens were of the same order as those of the uniaxial test specimens, but were only half the lives of the rotating bending specimens for given stresses. A sample application of the S-N data is discussed.

• DOE Contract Number: FC02-93ER54186
• OSTI ID: 476726
• Report Number(s): CONF-950722--
• Journal Information: Advances in Cryogenic Engineering, Journal Name: Advances in Cryogenic Engineering Vol. 42A; ISSN 0065-2482; ISSN ACYEAC
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
66 PHYSICS
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
CRACK PROPAGATION
FATIGUE
INCOLOY ALLOYS
ITER TOKAMAK
MECHANICAL TESTS
NIOBIUM BASE ALLOYS
SERVICE LIFE
STRESS ANALYSIS
SUPERCONDUCTORS
TEMPERATURE DEPENDENCE
TENSILE PROPERTIES
TIN ALLOYS