Summary Report. Fatigue Failure and Fracture Mechanics of Graphites for High Temperature Engineering Testing Reactor.

Ishiyama, Shintarou; Oku, T.; Eto, Minoru

doi:10.3327/jnst.28.472

Cited by 6 publications

(2 citation statements)

References 11 publications

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“…This heater would need to undergo a rigorous vibration analysis tailored to the desired launch environment in order to be considered a launch candidate design. Expected thermal stresses are within the fatigue limit of graphite (<50% of ultimate strength), 28 so failure due to thermal cycling is not likely to occur. Previous life tests of hollow cathodes constructed using graphite cathode tubes also suggest that graphite is well-suited to the mechanical and thermal loading inherent in cathode operation.…”

Section: Lifetime Estimationmentioning

confidence: 99%

Multi-kilowatt-class heaters for large hollow cathodes

Wordingham

Taunay

Choueiri

2018

Review of Scientific Instruments

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Heater materials and geometry are analyzed to address the requirements of large lanthanum hexaboride hollow cathodes. Larger hollow cathodes are capable of increased discharge currents but require higher heater powers to ignite. Existing cathode heaters suffer from material interactions and increased failure rates at high temperatures and are currently not viable for high-power operation; graphite heaters can provide order-of-magnitude increases in heater power and operational life simultaneously. Two models, a simplified circuit model and a finite-element model, were developed to predict the heater operating temperature and resistance. The operational life of the heater was estimated using a vacuum sublimation model. A graphite heater was fabricated and tested using a large-diameter lanthanum hexaboride hollow cathode to demonstrate feasibility as a high-power heater material. The prototype has repeatedly achieved cathode ignition and was tested at up to 4.5 kW of heater power. Heater voltage and current were measured prior to ignition and used to calculate the heater resistance. The measured resistance is within 8% of the predicted value for the circuit model and within 2.5% of the finite-element prediction. At cathode ignition temperatures, the vacuum sublimation model predicts an order-of-magnitude increase in operational life as compared to existing cathode heaters; for a peak surface operating temperature of 1500 °C, the vacuum sublimation model predicts a 1%-loss life of approximately 400 kh.

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Section: Lifetime Estimationmentioning

confidence: 99%

Multi-kilowatt-class heaters for large hollow cathodes

Wordingham

Taunay

Choueiri

2018

Review of Scientific Instruments

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“…Price [5] führte eine der ersten systematischen Untersuchungen über die Schwingfestigkeit von Reaktorgraphit bei axialer zyklischer Belastung und einer Reihe von Lastverhältnissen (R-Werten) durch. Ergebnisse von umfangreichen Untersuchungen der Lebensdauer und des Ermüdungsrisswachstums sind von Ishiyama und Mitarbeitern beschrieben [6]. Das Ermüdungsver-halten von feinkristallinem isotropem Graphit bei Wechselbiegebelastung und periodischer schlagartiger Belastung [7], sowie die Anwendbarkeit von linearen Schadensakkumulationsrechnungen auf Zweistufen-Ermüdungsversuche [8] ist ebenfalls in der Literatur beschrieben.…”

Section: Introductionunclassified

Ermüdungsverhalten und Dauerfestigkeit von Graphit und Aluminium – infiltriertem Graphit

Papakyriacou¹,

Mayer²

2006

Mat.-wiss. u. Werkstofftech.

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cycles. The open porosity of Graphite (10-11 Vol.-%) was infiltrated with the aluminium alloy using the squeeze casting infiltration method, which led to an increase of the bending strength by 50 %, increase of tensile strength by 30 % and increase of stiffness by 15 %. Fully reversed tension-compression loading of FU2590 delivers a mean endurance limit at 10 9 cycles at the normalized maximum stresses (i.e. maximum tension stress of a cycle divided by the static strength) of 0,65AE0,03. Mean numbers of cycles to failure of 10 4 were found in fully reversed bending tests at the normalized maximum stress of 0,78. The infiltrated material shows approximately 30 % higher cyclic strength in reversed bending tests, and the mean endurance limit under tension compression loading increases by 15 %. The increased endurance limit of the infiltrated material is caused by the increased stiffness. The increased toughness of graphite due to the infiltration with aluminium is of additional beneficial influence at the higher cyclic stresses investigated in reversed bending tests and in static tests.

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