Real-time quantitative imaging of failure events in materials under load at temperatures above 1,600 °C

Abstract

Ceramic matrix composites are the emerging material of choice for structures that will see temperatures above ~1,500 °C in hostile environments, as for example in next-generation gas turbines and hypersonic-flight applications. The safe operation of applications depends on how small cracks forming inside the material are restrained by its microstructure. As with natural tissue such as bone and seashells, the tailored microstructural complexity of ceramic matrix composites imparts them with mechanical toughness, which is essential to avoiding failure. Yet gathering three-dimensional observations of damage evolution in extreme environments has been a challenge. Using synchrotron X-ray computed microtomography, we have fully resolved sequences of microcrack damage as cracks grow under load at temperatures up to 1,750 °C. Our observations are key ingredients for the high-fidelity simulations used to compute failure risks under extreme operating conditions.

Effect of boundary conditions on the evolution of lattice strains in a polycrystalline austenitic stainless steel

“…included sample-to-sample differences [20], difference of plastic strains created from loading up for each sample and thermal strains/stresses introduced in each sample during air quenching [21] can also change the lattice strains in materials significantly. The current in situ constant load creep results are also different to the in situ neutron diffraction creep experiments conducted by Rao et al [11] in spite of similar macroscopic creep strain (*0.62%) generated from similar duration (12 h) of primary creep stage.…”

A rotational and axial motion system load frame insert for in situ high energy x-ray studies

“…One solution for rotation of a sample with in situ mechanical testing has been to attach a load frame to the top of a rotation stage. [32][33][34][35] This solution is not practical for the current experimental requirements, as the location of the near field detector (∼5 mm from the specimen) would limit the rotation range of the load frame to a small angular window beyond which the support columns would cause interference. At the same time, simple ad hoc arrangements have demonstrated the possibility and value of in situ loading that is compatible with near field measurements.…”

Structure recognition from high resolution images of ceramic composites

“…Research on 3D imaging of SiC-based composites under load can reveal how microscopic damage influences strength and toughness of materials [1]. In order to maximize material strength, continuous fiber bundles are woven into the ceramic, and oriented along primary load paths.…”

“…Assessing the scale, geometry and structural composition of such materials is of paramount importance to quantify strength, to monitor crack propagation and to guarantee engineering safety [1,2]. In order to retrieve internal structure of solid objects and evaluate their properties, materials have been examined using computed microtomography (µ-CT) generated at light sources.…”