Dynamic Response of Aerospace Materials Subjected to Extreme Environments

Abstract

An experimental investigation was conducted subjecting Hastelloy X plates to shock loadings. The study seeks to understand the structural response of these aerospace materials when subjected to a combination of high temperature and shock loading with different boundary conditions. First, an exhaustive series of experiments was conducted simultaneously subjecting Hastelloy X plates to extreme temperatures, in-plane tensile loading, and transverse shock loading. To achieve these loadings, a shock tube apparatus was used in conjunction with a novel hydraulic pre-loading fixture outfitted with propane flame torches. Experiments were carried out at peak shock loads of 1.7 and 3.1 MPa, temperatures up to 900°C, and in-plane tensile loads up to 80% of the yield strength of the material at the given temperature. High speed photography and Digital Image Correlation (DIC) was used to obtain full-field, three-dimensional deformation information during the event. It is evident that the addition of a tensile pre-load reduces the maximum deflection for all temperatures. However, further increasing the magnitude of a pre-existing tensile pre-load has diminishing returns at temperatures above 400°C. It was seen that the specimen experiences a decrease in resistance to deformation caused by a blast loading for temperatures until 800°C. However, at 900°C, the specimen’s resistance was observed to be greater than at 800°C. It was also observed that an indentation mode of deformation occurs at high temperatures in the case of 3.1 MPa peak load case but for no temperature in the 1.7 MPa peak load case. Next, a comprehensive series of experiments was conducted subjecting cantilevered Hastelloy X plates to extreme temperatures and oblique shock loadings. A shock tube was used to achieve consistent planar shock waves and was supplemented by four propane torches to obtain high specimen temperatures. To capture the deformation event, high speed photography was used in conjunction with DIC to attain full-field, three-dimensional deflections, velocities, and strains. Experiments were conducted at temperatures of 25°C, 400°C, and 800°C and shock angles of 0° (normal), 15°, and 30°. It is evident that an increase in temperature causes an increased magnitude in out-of-plane deflection and in certain cases causes the deformations to occur in mode II. It is also observed that increasing the angle of the specimen relative to the shock decreases the magnitude of out-of-plane deformation.