Tube-shaped Specimens Research Articles

Hyena and ‘false’ sabre-toothed cat coprolites from the late Middle Miocene of south-eastern Austria

ABSTRACT An association of eighteen coprolites (specimens 01–18) and one isolated coprolite (specimen 209,210) were found in a vertebrate fossil-rich paleosol at the Gratkorn site (south-eastern Austria; late Middle Miocene). The specimens consist mostly of calcium phosphate (apatite) and a matrix formed by microglobules. Coprolites 01–18 show cylindrical and spherical morphologies and are considerably smaller than the tube-shaped specimen 209,210, in which no inclusions were observed. In contrast, coprolites 01–18 contain numerous, highly altered bone fragments (sub-mm-sized long bones and several mm-sized trabecular bone remains) as well as hair imprints, plant detritus and palynomorphs. Based on composition, morphology, size, microstructure, and inclusions, and considering the body fossil record of this site, we assume the hyaenid Protictitherium and the barbourofelid Albanosmilus, as producers of coprolites 01–18 and 209,210, respectively. The preserved bone remains in specimens 01–18 suggest that Protictitherium fed on small vertebrates, but possibly also cracked bones of medium-sized animals. The hair imprints found were either from the hyaenid itself or its prey, while the plant material was probably ingested accidentally. The lack of inclusions in specimen 209,210 is related to the presumably hypercarnivorous diet of Albanosmilus, which was certainly the apex predator in this biome.

Non-destructive characterization of internal surfaces in Laser Powder Bed Fused Inconel 718 channels prior and after post-treatment

The effect of surface finishing treatments for inner surfaces of additvely manufactured Inconel 718 specimens were analyzed using X-ray computed tomography (CT). The tube-shaped specimens were built by Laser Powder Bed Fusion (LPBF) at different build orientations and the inner surface characteristics such as roundness, equivalent diameter, 3D curvature distribution and distance to nominal surface as radial roughness for internal channels, both in the primary “as built” condition and after the subsequent treatment, were evaluated.

Equal-Channel Angular Pressing of Thin-Walled Copper Tube

During the last decade, materials with high strength-to-weight ratio have been in demand for industrial usage. Various severe plastic deformation methods such as SE process and HPTT process for tube-shaped specimens have been proposed and experimented. The common difficulty among these SPD techniques for producing tube-shaped specimens is theirs expensive and complicated setups. It is ideal to introduce a new method based on the simplicity of setup and low cost to produce thin-walled (R/t > 10, where R is the radius and t is the tube wall thickness) UFGed tube-shape component. Based on this conception, a new technique has been proposed and experimented. In this work, thin-walled copper tube specimens with 1 mm wall thickness and 23 mm diameter have been successfully ECAPed up to four passes through two different fundamental routes (BC and C) with the die channel angle of 90° using flexible polyurethane rubber pad. Hardness measurements on both annealed and ECAPed tubes show that 90 % increase in hardness value and also 200 % reduction in the grain size were achieved after four passes. Furthermore, the thickness measurement taken from several locations of the tube indicated that the process did not change the dimension of the deformed specimens.

Shear flexoelectric coefficient μ1211 in polyvinylidene fluoride

Defined as a strain gradient-induced electric polarization, flexoelectricity exists in all dielectric materials. The coefficient that exists between the strain gradient and the electric polarization defines the flexoelectric coefficient tensor. The tensor components along the longitudinal and transverse directions have been studied widely. However, little progress has been reported on flexoelectric properties in the shear direction to date. In this work, a novel method for measurement of the shear flexoelectric coefficient μ1211 of polyvinylidene fluoride is presented. An experiment is conducted on a tubular unpolarized specimen, where shear strain gradient is generated along the radial direction by applying torque to the ends of the tube-shaped specimen. Dynamic torque is exerted on specimens with a static bias value and at different frequencies. The generated shear strain gradient is calculated via finite element analysis and the corresponding induced electrical polarization is measured using a charge amplifier. The shear flexoelectric coefficient μ1211 is found to have an average value of 7.318 × 10−10 C/m at room temperature. The experimental results show good agreement with the theoretical predictions and indicate the potential value of this material property for electromechanical device fabrication.

Oxidation behavior of austenitic stainless steels as fuel cladding candidate materials for SCWR in superheated steam

Oxidation behavior of austenitic stainless steels as fuel cladding candidate materials for supercritical-water-cooled reactor (SCWR), including three types of 15Cr–20Ni stainless steels (1520 SSs), in the temperature range of 700–780°C superheated steam have been investigated. Effect of temperature, dissolved oxygen (DO), degree of cold work (CW), and machined layer by cold drawing process on the oxidation kinetics assuming power-law kinetics are discussed. Characteristics of oxide layers and its relation to oxidation behaviors are also discussed. The effect of DO on the weight gain behavior in superheated steam at 700°C was minor for all specimens at least up to 200ppb DO. The tube-shaped specimens of 1520 SSs showed very good oxidation resistance at 700–780°C. There was no clear difference in the oxidation kinetics among the three investigated types of 1520 SSs. The machined layer formed at the tube surface has a significant role to mitigate oxidation in superheated steam. A fine-grained microstructure near the surface due to recrystallization by cold drawing process is effective to form the protective Cr2O3 layer. It has been suggested that since Cr diffusion in the outside surface of tubes is accelerated as a result of an increased dislocation density and/or grain refinement by cold drawing, tube specimens show very slow oxidation kinetics. Breakdown of the protective Cr2O3 layer and nodule oxide formation were partly observed on the tube-shaped specimens of 15Cr–20Ni SSs. The reliability of Cr2O3 layer has to be carefully examined to predict the oxidation kinetics after long-term exposure.

Influence of compressive load conditions and thickness on the two-way shape memory behavior in tube-shaped NiTi alloy

The two-way shape memory behavior of Ni55Ti45 was investigated to develop a tube-shaped NiTi actuator which could generate a large amount of force. The two-way shape memory effect (TWSME) was induced by thermal cycling under various amounts of constant compressive stress. Six specimens with the same outer diameter and different thickness were used to apply the TWSME to an actuator. A fast saturation tendency of the recovery strain was shown through training at each level of constant stress, after which the two-way shape memory strain was quantitatively measured during thermal cycling for each level of applied stress. From the results, the maximum two-way strain value was obtained after training at a constant level of stress and then decreased thereafter. In addition, the two-way strain was found to depend on the thickness of the tube-shaped specimen. All specimens could be divided into two groups depending on the rate of increase in the two-way strain. After two-way strain was obtained, the two-way recovery stress was measured to verify the performance of the sample as an actuator. The results showed that the two-way recovery stress behavior was similar to the two-way strain; if the optimal thickness of the specimen and the stress applied for training are used for the development of the TWSME, tube-shaped NiTi using the TWSME can replace one-way shape memory alloys.

Simulation of stress corrosion cracking behavior in a tube-shaped specimen of nickel-based alloy 600

Stress corrosion cracking (SCC) simulation code has been developed for the evaluation of SCC behavior in specimens in the shape of field components. The code utilizes numerical calculation of stress/strain states at a crack tip using finite element methods and a formula describing the crack tip reaction kinetics containing unknown environmental parameters. The applicability of this simulation code was investigated by applying the code to the evaluation of SCC behavior in a mock-up of a bottom mounted instrumentation tube for a pressurized water reactor subjected to complex stress/strain states. The results indicate that crack growth rate in a component suffering from certain environments can be estimated using the developed SCC simulation code with pre-determined unknown parameters, using the experimental crack growth rate data measured on other specimens in the same environment.

Application of induced current potential drop technique for measurements of cracks on internal wall of tube-shaped specimens

This paper presents the applicability of induced current potential drop (ICPD) technique to the detection and sizing of defects in objects with a shape of real components. The shape of tube was selected as one of the shape of real components and an ICPD sensor for the inspection of tube-shaped specimens was developed. The usefulness of the developed sensor was verified by experiments. Finite element analysis (FEA) was conducted to obtain calibration data to convert potential drop (PD) data measured using the sensor into the depth of defects. It was shown that the crack depths estimated based on measured PDs and FEA showed good agreement with the crack depths estimated by ultrasonic testing.

Development of a Stress Corrosion Cracking Test Methodology Using Tube-shaped Specimens

Abstract Stress corrosion cracking (SCC) is one of the greatest concerns in nuclear aging and degradation, and studies on the measurement of stress corrosion crack growth rates (CGR) and the effects of environmental, material, and mechanical parameters on the CGR have been performed using mainly fracture mechanics specimens. However, the stress states for the fracture mechanics specimens are different from that of real field components and there is concern about the applicability of the data obtained from fracture mechanics specimens to the evaluation of SCC behaviors in real field components. In this study, in order to obtain SCC for specimens that have a similar shape of real field components under complicated stress states, an SCC test methodology using specimens in the shape of tubes was developed. Its effectiveness was verified by performing an SCC test using a mock-up of a bottom mount instrumentation tube of a pressurized water reactor (PWR) under a simulated PWR primary water environment. Intergranular SCC was created in the mock-up specimen using the developed SCC test methodology and SCC crack growth rate for the mock-up specimen was measured.

Enthalpy and temperature of the titanium alpha-beta phase transformation

The specific enthalpy and the temperature of the titanium α-β phase transformation were measured by a pulse-heating system operating in the millisecond time regime. The measurement technique is based on self-heating of a tube-shaped specimen from room temperature to the beta phase of titanium. A comparison between the measured phase transition temperature during heating and cooling of the specimen shows a difference of approximately 20 K. The temperature measured during the heating period is higher than the value obtained from the cooling cycle of the specimen. For the evaluation of the specific enthalpy of the alpha-beta transformation, the specific enthalpy versus temperature function of the beta phase of the heating period was extrapolated to the transition temperature obtained from the cooling cycle (1152 K). A total of 12 measurements on 3 tube-shaped specimens was made, an average value of 89.9 kJ⋅kg−1 was obtained for the specific enthalpy of the transformation. The reproducibility of the measured specific enthalpy at the beginning and at the end of the transformation was 0.5%. The reproducibility of the phase transformation enthalpy as difference between the beginning and the end was 3%. The extended measurement uncertainty (at a confidence level of 95%) is estimated to be ±6% for the specific enthalpy of the transformation and ±6 K for the transformation temperature.

Thermophysical Properties of Solid and Liquid 90Ti–6Al–4V in the Temperature Range from 1400 to 2300 K Measured by Millisecond and Microsecond Pulse-Heating Techniques

The heat capacity and electrical resistivity of 90Ti–6Al–4V were measured in the temperature range from 1400 to 2300 K by two pulse-heating systems, operating in the millisecond and microsecond time regimes. The millisecond-resolution technique is based on resistive self-heating of a tube-shaped specimen from room temperature to melting in less than 500 ms. In this technique, the current through the specimen, the voltage drop along a defined portion of the specimen, and the temperature of the specimen are measured every 0.5 ms. The microsecond-resolution technique is based on the same principle as the millisecond-resolution technique except for using a rod-shaped specimen, a faster heating rate (by a factor of 10,000), and faster data recording (every 0.5 μs). Due to the rapid heating with the microsecond system, the specimen keeps its shape even in the liquid phase while measurements are made up to approximately 300 K above the melting temperature. A comparison between the results obtained from the two systems with very different heating rates shows significant differences in phase transition and melting behavior. The very high heating rate of the microsecond system shifts the solid–solid phase transition from the (α+β) to the β phase to a higher temperature, and changes the behavior of melting from melting over a temperature range to melting at a constant temperature like an eutectic alloy or a pure metal.

HEAT CAPACITY OF TITANIUM IN THE TEMPERATURE RANGE 1500 TO 1900 K MEASURED BY A MILLISECOND PULSE-HEATING TECHNIQUE

Heat capacity of titanium in the temperature range 1500 to 1900 K was measured by a pulse-heating system, operating in the millisecond time regime. The measurement technique is based on selfheating of a tube-shaped specimen from room temperature to melting in approximately 500 ms and measuring current through the specimen, voltage drop along a defined portion of the specimen, and temperature of the specimen every 0.5 ms. A total of 12 measurements on 3 tube-shaped specimens was made. The reproducibility between individual measurements was 0.4%, between different specimens 0.7%. The extended measurement uncertainty (at a confidence level of 95%) is estimated to be 3%.