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Hunt, R. M.

Publications and source records attributed to Hunt, R. M..

6 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Joining techniques for a reduced activation 12Cr steel for inertial fusion energy

At Lawrence Livermore National Laboratory, we are developing a reduced activation ferritic martensitic steel that is based on the ferritic martensitic steel HT-9. As a part of the development of this steel, we tested a series of welding processes for characterization, including conventional welds (electron beam, tungsten inert gas, and laser) as well as solid-state welds (hot isostatic pressing). We also heat treated the joints at various temperatures between 750 °C and 1050 °C to find a suitable normalization scheme. The modified HT-9 reduced activation ferritic martensitic steel appears highly suitable to welding and diffusion bonding. All welds showed good quality fusion zones with insignificant cracking or porosity. Additionally, a heat treatment schedule of 950 °C for one hour caused minimal grain growth while still converging the hardness of the base metal with that of the fusion and heat-affected zones. Also, modified HT-9 diffusion bonds that were created at temperatures of at least 950 °C for two hours at 103 MPa had interface tensile strengths of greater than 600 MPa. The diffusion bonds showed no evidence of increased hardness nor void formation at the diffusion bonded interface.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2013

Fatigue cracking of a bare steel first wall in an inertial confinement fusion chamber

Inertial confinement fusion power plants will deposit high energy X-rays onto the outer surfaces of the first wall many times a second for the lifetime of the plant. These X-rays create brief temperature spikes in the first few microns of the wall, which cause an associated highly compressive stress response on the surface of the material. The periodicity of this stress pulse is a concern due to the possibility of fatigue cracking of the wall. We have used finite element analyses to simulate the conditions present on the first wall in order to evaluate the driving force of crack propagation on fusion-facing surface cracks. Analysis results indicate that the X-ray induced plastic compressive stress creates a region of residual tension on the surface between pulses. This tension film will likely result in surface cracking upon repeated cycling. Additionally, the compressive pulse may induce plasticity ahead of the crack tip, leaving residual tension in its wake. However, the stress amplitude decreases dramatically for depths greater than 80–100 μm into the fusion-facing surface. Crack propagation models as well as stress-life estimates agree that even though small cracks may form on the surface of the wall, they are unlikely to propagate further than 100 μm without assistance from creep or grain erosion phenomena.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS1985

Human factors of intelligent computer aided display design

Design concepts for a decision support system being studied at NASA Langley as an aid to visual display unit (VDU) designers are described. Ideally, human factors should be taken into account by VDU designers. In reality, although the human factors database on VDUs is small, such systems must be constantly developed. Human factors are therefore a secondary consideration. An expert system will thus serve mainly in an advisory capacity. Functions can include facilitating the design process by shortening the time to generate and alter drawings, enhancing the capability of breaking design requirements down into simpler functions, and providing visual displays equivalent to the final product. The VDU system could also discriminate, and display the difference, between designer decisions and machine inferences. The system could also aid in analyzing the effects of designer choices on future options and in ennunciating when there are data available on a design selections.

Hunt, R. M.↗