後方応力を制御した高炭素鋼伸線材の表層除去による機械的性質の究明

Electric field-induced bending in ferroelectric ceramics has attracted considerable interest recently, but the mechanisms of this phenomenon are not fully understood. In this work, we show that electric field-induced bending deformation can be observed in (Ba,Sr)TiO3 ceramics with different concentrations of SrTiO3. Experimental results, such as reduction in bending deformation by removing surface layers and increasing ceramic thickness, suggest that this phenomenon can be well explained by the polarized surface layer mechanism, a key mechanism for the flexoelectric response in ferroelectric ceramics. The variation in bending deformation behaviors with ceramic compositions and temperature was further measured, and the results also support the surface layer mechanism. Our results indicate that the magnitude of the applied electric field is also an important factor affecting the bending behavior of the ceramics due to the modification of the polarization state of bulk when the field is higher than the coercive field of the ferroelectric ceramics. Our study provides a deeper understanding of the electric field-induced bending phenomenon in ferroelectric ceramics.

The impact of various cooling environments on the distribution of macroscopic residual stresses in near-surface layers of ground steels

<strong class="journal-contentHeaderColor">Abstract.</strong> We propose a z-coordinate algorithm for ocean models which, thanks to the insertion and removal of surface layers, can deal with an arbitrarily large tidal oscillation independently of the vertical resolution. The algorithm is based on a classical two steps procedure used in numerical simulations with moving boundaries (grid movement followed by a grid topology change, that is insertion/removal of surface layers) which leads to a stable and accurate numerical discretization. With ad-hoc treatment of advection terms at non-conformal edges that may appear due to insertion/removal operations, mass conservation and tracer constancy are preserved. This algorithm, called z-surface-adaptive, can be reverted, as a particular case when all layers are moving, to other z-surface-following coordinates, such as z-star or quasi-z. With simple analysis and realistic numerical experiments, we compare the surface-adaptive-z coordinate against z-star and we show that it can be used to simulate effectively coastal flows with wetting and drying.

The argon fluoride excimer laser emits radiation in the far ultraviolet part of the electromagnetic spectrum (193 nm). Each photon has high individual energy. Exposure of materials or tissues with peak absorption around 193 nm results in removal of surface layers (photoablation) with extremely high precision and minimal damage to non-irradiated areas. This precision is confirmed in a series of experiments on cadaver eyes and the treatment of 25 eyes with anterior corneal disease (follow-up 6 to 30 months). Multiple zone excimer laser superficial keratectomy is considered the treatment of choice for rough, painful corneal surfaces. All patients in this group were pain-free postoperatively. Where good visual potential exists, ablation of a single axial zone is recommended and results in improved visual acuity and reduction of glare. A hyperopic shift was noted in this group.

ATTENTION has frequently been directed to the plasticity of crystals of rocksalt when immersed in water. Some see the cause of the plasticity in the removal of surface layers with their cracks and defects. Others suppose that water penetrates the crystal lattice and acts as a lubricant. It is interesting to observe the behaviour of crystals in a state of recent formation from solution or melt. For this purpose I have made some experiments with sylvine (KC1).

A technique is developed for the correction of the depth distribution of residual stresses measured by an X-ray method with allowance for their relaxation upon the removal of surface layers. This technique is applied to the study of a D16 aluminum alloy strip subjected to shot-blasting metal forming. This technique can be used to estimate the distribution of residual stresses across massive parts after various types of treatment.

A 200 kV ion accelerator, with a PIG source for accelerating ionized gases, was coupled to a 500 kV transmission electron microscope in order to investigate the effects of helium irradiation on the development of microstructure in candidate fusion reactor first wall material. The microstructural evolution in nickel and in type 316 stainless steel bombarded by 80 keV helium ions was monitored via video recordings. The effect of specimen thickness and temperature and the effect of plastic deformation during irradiation was considered. In order to conduct these experiments a quantitative load-elongation hot tensile stage was constructed with a capability for monitoring specimen current continuously during the experiment. It was found that surface exfoliation and blistering may occur in specimens thinner than the mean projected range of helium ions. However, in the thinnest specimen regions, surface layer removal is replaced by the bending of individual grains. Blistering apparently can occur when underpressurization of bubbles exists. Plastic deformation during helium ion irradiation can lead to denuded layers adjacent to some grain boundaries and can produce removed surface layers whose thickness is several times greater than the project mean range of the incident helium ions.

Molar-incisor hypomineralisation (MIH) is a problematic and costly condition. Caries remineralising agents are often recommended for MIH management despite the lack of evidence that these lesions have the capacity for increasing their mineral content. Following surface layer removal ± NaOCl pre-treatment and 14-day exposure to a CPP-ACFP solution at pH 5.5, MIH lesions were analysed using transverse microradiography and polarised light microscopy. Lesions were highly variable but treatment with the remineralising solution increased mineral content (1,828 ± 461 vol% min·µm, %R = 17.7 ± 5.7) and porosity decreased demonstrating the proof of concept that the mineral content of developmentally hypomineralised enamel can be improved after eruption.

This study evaluates the effect of post-manufacturing treatment on the compressive performance of additively manufactured components. The components were thin cylindrical shells with an aspect ratio of 25:1 manufactured using laser powder bed fusion and that were then surface treated by means of sandblasting or turning. The as-printed and subsequently surface treated samples were uniaxially compressed until failure to depict the effect of the surface condition on the compressive mechanical behavior. The results show that as the surfaces became smoother via sandblasting, the average peak strength for buckling load improves negligibly (0.85%), whereas this effect reaches 6.5% upon surface layer removal via turning. Through microstructural investigation and co-relating this with an understanding of processing conditions existing in manufacturing itself, this effect is seen to be linked to contour scanning causing softening of the surface region in a component.

In order to ascertain the superior characteristics of PCBN tool for hardened material machining, to promote the cutting performance and efficiency of a mold manufacturing, to investigate the wear mechanism of the cutting tool, and to investigate the dimensional accuracy and surface finish of the machined molds, SKD11 die steel and the polycrystalline cubic boron nitride are used as the workpiece and tool materials, respectively, in this study for turning experiments. After some proper surface layers removed from the workpiece in the experiment, the tool wear was measured through the toolmaker’s microscope and the roughness of the machined surface was measured by the roughness measuring instruments. So that, the associated sampling data prepared for training pattern of a neural network can be obtained. Besides, the noise-mediator was used to detect cutting noise during each surface layer removal for the cutting performance judgment in the machining processes additionally. An assessment model of cutting process is thus developed using a neural network system if the reliable and sufficient data is taken from the experiments. Based on the developed neural network, the complicated relationships between the cutting parameters (cutting speed, depth of cut and feed rate) and the cutting performance (surface roughness, tool wear and cutting temperature) can be clearly clarified. The best surface roughness of 0.29μm Ra is obtained from these experiments under the cutting conditions of d =0.2mm, f =0.05mm/rev and V=120m/min. This surface quality is equivalent to the manufacturing process of chemical-mechanical polishing (CMP), and the surface roughness of 0.2~0.5μm Ra may be attained by CMP. The CMP is always applied to high precision surface processing such as the valve piping and connector components in semiconductor/LED manufacturing.

CEMS study of fracture surfaces in SAE 4340 steel

ABSTRACTMolten salt flameless oxidation of graphite is one of the prospective methods of irradiated graphite waste processing. Molten salts are capable to retain a considerable part of radionuclides, to neutralize acidic off gases, moreover spent salts could be vitrified on completion of the process. We have used thermodynamic modelling to assess the efficiency of molten salt oxidation of graphite. Equilibrium compositions of both the melt and the off gas were calculated depending on graphite content and temperature. The feasibility of decontaminating the irradiated graphite of its near-surface layers using complete molten salt oxidation was investigated in a series of laboratory experiments. As the molten salt medium used to oxidize irradiated graphite we have investigated lithium, potassium and sodium carbonates. Sodium sulphate, boron oxide, barium and potassium chromates were also used as oxidizers. Tests were carried out at 870–1270 К. The efficiency of decontamination of graphite blocks has been assessed based on the activity of 137Cs and 60Со in the samples before and after molten salt oxidation. Data obtained demonstrated the feasibility of decontamination by molten salt removal of near surface layers on irradiated graphite blocks. Decontamination rate and efficiency depend on oxidizers used and temperature of process.

In this study, AISI 321 austenitic stainless steel samples were surface treated using severe shot peening (SSP) with 1 000 % and 1 300 % coverages. Microstructural features including the grain size, phase transformation, and formation of sub-surface microcracks were investigated at the rough top surface and about 40 μm depth (top surface after grinding and removal of initial rough surface layer created by SSP). In addition, microhardness variations were thoroughly analyzed in-depth. Experimental results demonstrated that for both 1 000 % and 1 300 % coverages, the microstructures of top surface and 40 μm depth are respectively composed of equiaxed nano-grains and lamella-shaped cells; however, enhanced imparted strain in the case of 1 300 % coverage leads to the formation of considerable amounts of strain-induced martensite (α′) phase in the surface layers and consequently, due to strength increase and lack of deformability, some microcracks are created in the sub-surface layers (up to 20 μm depth).

This paper presents results of pitting corrosion resistance of TIG (autogenous and with filler metal) and A-TIG welded lean duplex stainless steel S82441/1.4662 evaluated according to ASTM G48 method, where autogenous TIG welding process was applied using different amounts of heat input and shielding gases like pure Ar and Ar+N2 and Ar+He mixtures. The results of pitting corrosion resistance of the welded joints of lean duplex stainless steel S82441 were studied in as weld conditions and after different mechanical surface finish treatments. The results of the critical pitting temperature (CPT) determined according to ASTM G48 at temperatures of 15, 25 and 35°C were presented. Three different surface treatment after welding were applied: etching, milling, brushing + etching. The influence of post weld surface treatment was studied in respect to the pitting corrosion resistance, basing on CPT temperature. Research on TIG welding of lean duplex stainless steel S82441/1.4662 showed a clear influence of the applied shielding gas mixtures, where the addition of 5 to 15% N2 to Ar virtually no effect on the level of resistance to pitting corrosion, only 5% N2 addition has a positive effect, while use of a mixture of 50% Ar + 50% He compared with welding at 100% Ar atmosphere, can significantly reduce the resistance to pitting corrosion. Definite good results were obtained during TIG welding with the participation of activation flux (A-TIG). The weld surface of lean duplex stainless S82441/1.4662 obtained in A-TIG welding without the addition of filler metal has a much lower tendency to pitting corrosion than traditional welds made by TIG method. Pitting corrosion resistance of welds made by A-TIG improved with the increase of the heat input in the tested range of welding current 100-200 A. It was also found that the intensity of the occurrence of pitting does not affect the method of cleaning welds after welding, but the mechanical removal of a thin surface layer of metal significantly reduces their intensity.

Use of the clayey cover of bauxite deposits of the Amazon region for geopolymer synthesis and its application in red ceramics