The Simplified Model Test (SMT) approach is an alternative creep-fatigue evaluation method that no longer requires the use of the damage interaction diagram, or D-diagram. The reason is that the combined effects of creep and fatigue are accounted for in the test data by means of a SMT specimen that is designed to replicate or bound the stress and strain redistribution that occurs in actual components when loaded in the creep regime. However, creep-fatigue experiments on SMT key feature articles are specialized and difficult to perform by the general research community. In this paper, two innovative SMT based creep-fatigue experimental methods are developed and implemented. These newly-developed SMT test methods have resolved all the critical challenges in the SMT key feature article testing and enable the potential of further development of the SMT based creep-fatigue evaluation method into a standard testing method. Scoping test results on Alloy 617 and SS 316H using the newly developed SMT methods are summarized and discussed. The concepts of the SMT methodology for creep-fatigue evaluation are explained.

We theoretically investigate the evaporative cooling of cold rubidium atoms that are brought close to a solid surface. The dynamics of the atom cloud are described by coupling a dissipative GrossPitaevskii equation for the condensate with a quantum Boltzmann description of the thermal cloud (the Zaremba-Nikuni-Griffin method). We have also performed experiments to allow for a detailed comparison with this model and find that it can capture the key physics of this system provided the full collisional dynamics of the thermal cloud are included. In addition, we suggest how to optimize surface cooling to obtain the purest and largest condensates.

We investigate theoretically how cold atoms, including Bose-Einstein condensates, are scattered from, or absorbed by, nanotubes with a view to analysing recent experiments. In particular, we consider the role of potential strength, quantum reflection, atomic interactions and tube vibrations on atom loss rates. Lifshitz theory calculations deliver a significantly stronger scattering potential than that found in experiment and we discuss possible reasons for this. We found that the scattering potential for dielectric tubes can be calculated to a good approximation using a modified pairwise summation approach, which is efficient and easily extendable to arbitrary geometries. Quantum reflection of atoms from a nanotube may become a significant factor at low temperatures, especially for non-metallic tubes. Interatomic interactions are shown to increase the rate at which atoms are lost to the nanotube and lead to non-trivial dynamics. Thermal nanotube vibrations do not significantly increase loss rates or reduce condensate fractions, but lower frequency oscillations can dramatically heat the cloud.

The Simplified Model Test (SMT) is an alternative approach to determine cyclic life at elevated temperature and avoids parsing the damage into creep and fatigue components. The original SMT concept [1] considered that the effects of sustained primary stress loading could be safely neglected because the allowable local stress and strain levels were much higher than the allowable sustained primary stress levels. This key assumption is critically evaluated on Alloy 617 using internal pressurized cylindrical SMT specimens at 950 °C. The impact of combined internal pressurization and displacement-controlled creep-fatigue loading on the SMT cycle life is demonstrated at different strain ranges. The effect of primary load on the SMT design method is discussed.

This study investigates carbon nanotube textiles as advanced personal protection equipment for firefighters and first responders. Carbon nanotubes are lightweight, flame resistant, and possess high mechanical and thermal properties. Carbon nanotubes are also thermally anisotropic, meaning they easily conduct heat along the axis of an individual tube, and are relatively insulating across the tube's diameter. By recognizing this anisotropic behavior, heat transfer through a layer of aligned carbon nanotubes in a garment can be partially redirected to a cold reservoir thereby protecting the wearer from heat stress and exhaustion. Finite element models were developed to simulate a carbon nanotube layer embedded in a firefighting garment and thermally connected to a cold reservoir. Simulation showed that under heat stress conditions, firefighter skin temperature was considerably reduced by the cooling layer.

Elastic follow up significantly influences the creep and creep-fatigue life of structural components in elevated temperature service. As such, assessing the amount of follow up a component sees under a given loading history is critical in properly designing a component for high temperature use. Current methods for quantifying elastic follow up based on an elastic follow up factor use simple constitutive models and are available only for simple component geometries. This work describes a method for assessing the follow up factor, as a function of position and time, from a finite element simulation. The method recovers the simple, analytic solutions for simple geometries and material models but can also provide follow up factors for complicated components, loading histories, and material models. We use this new method to assess the range of follow up factors in a variety of prototypical high temperature structural components. This information can be used to improve design methods by better understanding the magnitude of follow up present in typical high temperature components. The method can also be used to support new design methods that require time-dependent point values of the follow up factor across a component.

The existing Class A metallic materials qualified for ASME Section III, Division 5 rules for high temperature nuclear reactors, are not optimized for corrosion resistance when exposed to corrosive reactor coolants such as molten salts, and molten lead and lead-bismuth eutectic. Introducing new corrosion-resistant materials into the Code would be a lengthy and expensive process for long design lifetimes, requiring long-term creep test data. A near-term alternative solution might be to allow designers to clad the existing Class A materials with thin layer of some corrosion-resistant material. However, the current ASME Section III, Division 5 rules provide no guidance on evaluating cladded components against the Code creep-fatigue or strain limits requirements. This necessitates the development of design rules for cladded components that do not require long-term testing of clad materials. Depending on the difference in mechanical properties, the influence of clad on the long term response of the structural system can be significant or negligible. This work focuses on developing design rules for cladded components with a clad material that does not accumulate significant inelastic deformation compared to the base material. This work proposes to treat such clad materials as linear elastic. Sample calculations including finite element analyses of a representative molten salt reactor heat exchanger tube without and with clad were performed to verify the proposed approach. Finally, a complete set of design rules for components with noncompliant clad material is proposed.