Nondestructive Testing of “Thick” Aerospace Honeycomb Structures Using Through-Transmitted Ultrasonic Guided Waves

The idea of using guided elastic waves for the purpose of assessing the fitness for service of aerospace composite structural materials is not new. “Pure” longitudinal or shear waves cannot exist in layers whose thickness dimension is of the order of an ultrasonic wavelength

Nondestructive Testing of “Thick” Aerospace Honeycomb Structures Using Through-Transmitted Ultrasonic Guided Waves

The idea of using guided elastic waves for the purpose of assessing the fitness for service of aerospace composite structural materials is not new. “Pure” longitudinal or shear waves cannot exist in layers whose thickness dimension is of the order of an ultrasonic wavelength.</p

Modelling the radionuclide transfer from bedrock to surface systems at Forsmark site (Sweden)

Quaternary sediments and soils at the Forsmark site (Sweden) would constitute the last barrier for radionuclide migration interposed between a deep repository of high level nuclear wastes (HLNW) and surface ecological systems. The retention capacity of these sediments is evaluated by means of reactive transport simulations. Two different scenarios have been modelled: (1) Inflow of deep fluids carrying radionuclides into shallow aquifers hosted in the carbonate glacial till, and (2) Inflow of deep fluids carrying radionuclides into organic matter-bearing clays. The model results predict that caesium is very efficiently retained in both scenarios for periods longer than 3000 years due to the strong affinity of this ion with the frayed edge sites of the illite layers. Strontium is also retained via cation exchange in illite and, in a lesser extent, via co-precipitation in calcite. The retention efficiency for strontium, however, quickly decreases to 0 after 1000 years. Uranium is retained in both scenarios with retention efficiencies higher than 40% at long term (>3000 years) due to precipitation of amorphous uraninite and adsorption on Fe(III) oxyhydroxides. Radium is only retained in the till aquifer since co-precipitation with barium sulphate does not occur in the clay porewater

Flexible impulse transfer using a Newton's Cradle-inspired catheter: A feasibility study

A major challenge during minimally invasive surgery is transfer of high forces through small, flexible instruments, such as needles and catheters, because of their low buckling resistance. In this study, we determined the feasibility of using a Newton's Cradle-inspired catheter (patented) to transfer high-force impulses. Exerting a high-force impulse on the tissue increases the critical buckling load and can prevent buckling. The system comprised an input plunger onto which the impulse is given, a (flexible) shaft filled with Ø2 mm stainless steel balls, and an output plunger to transfer the impulse to the target tissue. In the proof-of-principle experiment, the effect on efficiency of clearance (0.1, 0.2, and 0.3 mm), length (100, 200, and 300 mm), shaft type (rigid vs. flexible), curve angle (0, 45, 90, 135, and 180°), and curve radius (20, 40, 60, and 100 mm) was determined. The catheter delivered forces of 6 N without buckling. The average impulse efficiency of the system was 35%, which can be further increased by optimizing the design. This technology is promising for high-force delivery in miniature medical devices during minimally invasive surgery.Accepted Author ManuscriptMedical Instruments & Bio-Inspired TechnologyMechatronic Systems Desig