Academic literature on the topic 'Miniaturized CT specimen'

Reactor pressurized vessel (RPV), which determines the lifetime of the nuclear power plant (NPP), is mainly forged using A508-3 steel in China. In order to meet the requirement of the small specimen test technique in the nuclear application, the fracture toughness of A508-3 steel was tested under-100°C using 1/4 CT specimens, and analyzed using Master Curve according to ASTM E 1921. In this work, the relationship of the KIC and the distance between the cleavage crack initiation site and the front of the fatigue crack is studied, and the transition temperature T0 of A508-3 is-98.7 oC, which is quite close to the test temperature.

Neural activity that occur during motor movement, speech, thought, and various other events can be observed in the form of brainwaves composed of synchronized electrical pulses emitted from adjoining communicative neurons. Observations of these brainwaves have been made possible through neurodevices, which can detect changes in electrical and/or mechanical parameters. For decades, the field of neuroscience has been enriched by the utilization of neurotechnologies at the microscale, which has begun to gain further enhancement with the introduction of nanotechnology. For example, microelectrodes were initially used for only extracellular measurements, but over the past decade, developments have been made to also record intracellular signals. Likewise, nanoknives, which gained popularity due to their versatility, can now be used for both fabricating bio-Micro-Electro-Mechanical Systems (MEMS) and also as a neurosurgery tool. Thus, considerable efforts have been made over the years to make micro- and nanosystems reliable, accurate, and sensitive to neural activity. In the late 20th century, several sophisticated technologies, including magnetic resonance imaging (MRI), computed tomography (CT), and intracranial pressure (ICP) monitoring have been integrated with MEMS. Furthermore, existing biotechnologies are being miniaturized at both the system and component level. For example, there is a remarkable interest in the field of neuroscience to utilize microfluidic technology as a diagnostic tool using specimens such as cerebrospinal fluid (CSF). Microfluidic devices are also employed as biocompatible drug delivery systems to target cells, tissues, and organs. This paper summarizes the recent developments in micro- and nano-scale neurotechnologies, including devices, fabrication processes, detection methods, their implementation challenges, in neural stimulation, monitoring, and drug delivery. This review discusses recent developments in micro and nanotechnologies, fabrication methods, and their implementation in neuroimaging, neurostimulation, monitoring of neural activities, and neural drug delivery.

This master´s thesis deals with the evaluation of fracture behavior of ODS steel MA956 at high temperature range. This behavior was tested by using miniaturized CT specimens, on which were performed experiments to measure of ductile crack growth resistance curves (J-R curves). The value of the fracture toughness was determined from these J-R curves. Fracture properties were consequently evaluated by using fractographic analysis of the fracture surfaces. Structural properties of material was identified by hardness measurement and analyzed by metallographic methods. Results of the measurements show drop of the fracture toughness with respect to the increasing temperature.

The use of miniature compact tension (mini-CT) specimens for fracture mechanics was experimentally demonstrated to allow the characterization of ferritic steels in the transition regime. In particular, the master curve transition temperature T0 can confidently be determined according to the ASTM E1921 standard using mini-CT specimens. This means that specimen size effect is well taken into account if loss of constraint is limited by restricting the test temperature range to remain below the allowed maximum loading level. In the upper shelf ductile regime, where stable crack growth occurs, a number of challenges should be overcome to use such a geometry to derive the crack resistance curve, or JR-curve, transferrable to a structure. Indeed, despite a large scatter, the experimental data on several materials suggest a size effect that underestimates the crack resistance when reducing specimen size. The crack resistance behavior of several reactor pressure vessel materials was investigated with square-sized ligament compact tension specimens of various size ranging from 1 inch-thickness (B = 25 mm) to the smallest thickness (B = 4.2 mm) of the mini-CT. The main objective of this paper is to estimate the crack resistance behavior of RPV steels that would be obtained with a standard 1T-CT specimen by using mini-CT with the appropriate specimen size correction. After a series of scaling attempts that were not successful, based on a simple dimensional analysis, a simple analytical formulation based on specimen thickness and ligament is suggested to account for specimen size effect for the CT geometry. Reasonable agreement could generally be found on a number of RPV materials between crack resistance measured with mini-CT and standard 1T-CT specimens.

The tendency to reduce specimen size for fracture toughness characterization of structural materials is gaining a spectacular interest in particular for irradiated materials. Indeed, the miniaturized compact tension (mini-CT) with a size of 10×10×4.2 mm is becoming very popular. With such a small volume, a large number of mini-CT specimens can be extracted from broken Charpy impact specimens and therefore makes this geometry very attractive and consequently several round robin exercises are organized to qualify this geometry. SCK•CEN has gained a lot of experience since the first usage of this geometry more than a decade ago. This geometry was qualified and tested in both unirradiated as well as irradiated condition. This paper overviews the SCK•CEN experience using the mini-CT geometry for fracture toughness characterization. In particular, it discusses the reliability of this geometry in comparison to large specimens such as the precracked Charpy and compares the advantages and limitations of such a geometry to derive some recommendations.