Fatigue, fracture, and life prediction criteria for composite materials in magnets
An explosively-bonded copper/Inconel 718/copper laminate conductor was proposed to withstand the severe face compression stresses in the central core of the Alcator C-MOD tokamak toroidal field (TF) magnet. Due to the severe duty of the TF magnet, it is critical that an accurate estimate of useful life be determined. As part of the effort to formulate an appropriate life prediction, fatigue crack growth experiments were performed on the laminate as well as its components. Metallographic evaluation of the laminate interface revealed many shear bands in the Inconel 718. Shear bands and shear band cracks were produced in the Inconel 718 as a result of the explosion bonding process. These shear bands were shown to have a detrimental effect on the crack growth behavior of the laminate, by significantly reducing the load carrying capability of the reinforcement layer and providing for easy crack propagation paths. Fatigue crack growth rate was found not only to be dependent on temperature but also on orientation. Fatigue cracks grew faster in directions which contained shear bands in the plane of the propagating crack. Fractography showed crack advancement by fatigue cracking in the Inconel 718 and ductile tearing of the copper at the interface. However, further away from the interfaces, the copper exhibited fatigue striations indicating that cracks were now propagating by fatigue. Laminate life prediction results showed a strong dependence on shear band orientation, and exhibited little variation between room temperature and 77{degree}K. Predicted life of this laminate was lower when the crack propagation was along a shear band than when crack propagation was across the shear bands. Shear bands appear to have a dominating effect on crack growth behavior.
- Research Organization:
- Massachusetts Inst. of Tech., Cambridge, MA (USA). Plasma Fusion Center
- Sponsoring Organization:
- DOE/ER
- DOE Contract Number:
- AC02-78ET51013
- OSTI ID:
- 6570667
- Report Number(s):
- DOE/ET/51013-285; PFC/RR-90-10; ON: DE91001663; TRN: 91-000104
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
MAGNETS
MATERIALS TESTING
ALCATOR DEVICE
BONDING
COMPOSITE MATERIALS
COPPER BASE ALLOYS
CRACK PROPAGATION
FATIGUE
FRACTURE PROPERTIES
SERVICE LIFE
STRESSES
THERMONUCLEAR REACTOR MATERIALS
ALLOYS
CLOSED PLASMA DEVICES
COPPER ALLOYS
FABRICATION
JOINING
MATERIALS
MECHANICAL PROPERTIES
TESTING
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
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