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In this study, we propose a method for predicting welding deformation caused by multi-pass welding using the thermal elastic–plastic finite element method (TEP-FEM) by considering the interpass temperature. This method increases the interpass temperature, which has not been considered in the existing TEP-FEM, from 200 °C to 1000 °C, and simultaneously performs thermal and mechanical analyses. In addition, this method can also evaluate temperature history and the time it takes to weld. By predicting the welding deformation using this method, angular distortion prediction was reduced from 16.75 mm to 10.9 mm compared to the case where the interpass temperature was cooled to room temperature. Additionally, the deformation error was significantly reduced from 6.14% to 2.92% compared to that of the strain as directed boundary method used in a previous study. Additionally, our research demonstrated that interpass temperatures above 800 °C can result in increased deformation errors. In conclusion, it is essential to select an appropriate temperature to minimize deformation error. [ABSTRACT FROM AUTHOR]

The microstructural change and fracture by repeated gas nitriding and gas nitrocarburizing of SUS304 jig were investigated in this study. It was found that an oxide layer which was formed owing to high–temperature oxidation of the microstructure near the surface, was easily detached from the surface layer. Also, many micro voids in the oxide layer were observed. Beneath the oxide layer, a compound layer containing mainly nitrides was identified. A carbon diffusion region was observed in the matrix adjacent to the interface between the compound layer and the matrix. It was considered that the fine voids and uneven surfaces induced under loading stress during both treatments were the crack initiation points, which coalesced for the development of cracking. The fractured surface exhibits a sequence of brittle and ductile fracture patterns as the microstructure changes from the surface to the interior. [ABSTRACT FROM AUTHOR]

In this study, we propose a method for predicting welding deformation caused by multi-pass welding using the thermal elastic–plastic finite element method (TEP-FEM) by considering the interpass temperature. This method increases the interpass temperature, which has not been considered in the existing TEP-FEM, from 200 °C to 1000 °C, and simultaneously performs thermal and mechanical analyses. In addition, this method can also evaluate temperature history and the time it takes to weld. By predicting the welding deformation using this method, angular distortion prediction was reduced from 16.75 mm to 10.9 mm compared to the case where the interpass temperature was cooled to room temperature. Additionally, the deformation error was significantly reduced from 6.14% to 2.92% compared to that of the strain as directed boundary method used in a previous study. Additionally, our research demonstrated that interpass temperatures above 800 °C can result in increased deformation errors. In conclusion, it is essential to select an appropriate temperature to minimize deformation error.

Local dry underwater backward median pulse MIG welding (LDU-BMPMIG) was proposed in this study. The effects of different backward median currents on welding process stability, weld forming, microstructure, and mechanical properties of weldments were investigated comprehensively. The results reveal that the backward median current waveform effectively improved the welding stability. By calculating the approximate entropy of the voltage signal during welding, it is proved that the welding stability increases first and then decreases with the increase of the backward median current. The welding process stability was the most satisfied with the backward median current of 200 A. The quality of weld formation was consistent with welding stability. LDU-BMPMIG weldments exhibited fewer macroscopic defects and better overall morphology compared with LDU-PMIG weldment. The weldment microstructure was mainly composed of γ-austenite and δ-ferrite with different morphologies. The satisfied stability of the welding process contributed to improving the microstructure uniformity. The variation trend of tensile strength for LDU-BMPMIG weldments was approximately kept consistent with welding process stability. The weldment prepared by 200 A showed considerable mechanical properties with minimal fluctuation, which reached 97.58% of maximum average tensile strength, which meant the most excellent compared to the others. The experimental results can improve the stability of local dry underwater welding and provide a theoretical basis and technical support for the application of underwater welding. [ABSTRACT FROM AUTHOR]

In this study, an investigation into the impact of heat transmission in the welded junction of SUS304 pipe has been carried out with the use of a numerical method. An investigation was carried out by employing ANSYS’s static structural tools in conjunction with the software package’s thermal transient analysis. Based on the heat flow on the welding point, where the temperature reaches 507 °C within 200 mm of the end of the welded pipe, an examination into the efficiency of heat transfer has been carried out. This analysis was based on the heat flow on the welding point. As the total heat flux approaches 7.02e6 W∙m–2, studies have been conducted on the topic. There have been three types of directional heat flux measurements made (X, Y, and Z), with the numerical findings indicating that the X direction produces the most variable heat flow readings. These checks were performed in a variety of settings. These were chosen as the correct paths to go since they led directly to the source of the warmth. whereas the Z-axis permits the minimum amount of heat flow throughout the board. The damaged area identified on the trees that were still standing was factored into the calculation. To calculate the amount of residual stress, the Von Mises stress was applied repeatedly during the whole procedure. This tactic ended up being employed. Due to the tension caused by the pipe’s increased bending radius, the piece of pipe located 200 mm from the pipe’s distal end is the most vulnerable. The value was calculated to be 2.49e6 Pa when the temperature was increased to 500 °C. [ABSTRACT FROM AUTHOR]

In this investigation, numerical analysis of square butt, butt with V-groove and T-weld joint configurations have been performed to estimate transient temperature distributions and residual stresses. A computational welding simulation based on a prescribed temperature approach was used that works on thermal load input derived from temperature analysis. In the thermal analysis, welding heat source or torch temperature was considered as the prescribed value of temperature, which helps in simulating real welding conditions. The inclusion of filler metal in the numerical analysis replicates the real welding phenomenon, which provides temperature distribution along the true distance of the joints. The maximum temperature was observed at the weld pool area and decreased in parabolic shape toward the base metal. Residual stresses were measured along the selected path (in the mid of plates) that comprises node-to-node variation of stresses in both longitudinal and transverse directions. von Mises and Tresca stress criterion was adopted to show accumulated stresses in the weld joints. It was observed that stresses accumulated in the different configurations of weld joints were below the yield strength 210 MPa of SUS304 steel. Peak values of stresses were observed at weld beads and in the nearby regions. [ABSTRACT FROM AUTHOR]

In order to prove the validity of prediction of penetration depth using Hablanian plot, we have compared experimentally obtained penetration depths with those predicted by Hablanian plot and linear multiple regression analysis. The experimental results with ∼1200 data points were obtained from bead‐on‐plate welding tests by the laser job shop. Stainless steel plates and four types of industrial CW lasers were used in these tests. From linear multiple regression analysis, it was found that dominating factors were laser power, welding speed, and spot diameter. On the other hand, we can predict the penetration depth using the 3th‐degree polynomial fitting curve (standard curve) expressed by Hablanian plot with two dimensionless parameters. The fitting difference between the standard curve and a data point results in the error of prediction. From Hablanian plot, it showed (1) that this fitting difference was dependent on some factors (such as laser power, welding speed, power density, and penetration depth), (2) that the fitting difference was, respectively, negative and positive in the lower and middle welding speed ranges, and (3) that the penetration depth could be precisely predicted by correcting the fitting difference in welding speed from the standard curve compared to the results predicted by linear multiple regression analysis. [ABSTRACT FROM AUTHOR]

Stainless steels (SUS) and dual-phase (DP) steels have tension-compression asymmetry (TCA) in mechanical responses to full loading cycles. This phenomenon can significantly influence sheet metal forming of such metals, however, it is difficult to describe this behaviour analytically. In this research, a novel analytical method for asymmetric elastic-plastic pure bending using the Cazacu–Barlat 2004 asymmetric yield function is proposed. It only uses material parameters in tension along with an asymmetry coefficient related to the yield function. Bending operations of SUS304 and DP980 are investigated as two case studies. In the pure bending for both SUS304 and DP980, moment–curvature diagrams are analytically obtained. Furthermore, linear and nonlinear springback behaviours of SUS304 are analytically investigated. Moreover, using the analytical model as a user-defined material, a numerical model is developed for both steels under pure bending. In the V-bending case of SUS304 with and without TCA effects, the springback behaviours of the material are investigated numerically. In addition, considering friction effects, the analytical method is further modified for predicting springback behaviours in the V-bending of 16 types of SUS304 with various strengths are determined. All the analytical and numerical results have good agreement with those experimental results from literature for validation. [ABSTRACT FROM AUTHOR]

To address the key manufacturing challenges such as severe columnar crystal growth trend and heterogeneous composition of molten pool, which caused by the rapid water cooling in local dry underwater welding (LDUW), the ultrasonic vibration assisted local dry underwater welding (U-LDUW) was innovatively proposed in this study. The phase structure and distribution, grain structure characteristic, microhardness, and tensile property of SUS304 weldments fabricated by LDUW and U-LDUW were investigated and compared comprehensively. The obtained results demonstrated that the stirring action on the molten pool was realized by the external ultrasonic vibration, which accelerated the ferrite morphology evolution from skeleton to lath, and more ferrites were remained in the austenite matrix. Compared with LDUW, the ultrasonic vibration facilitated to break the dendritic crystals, with the ultrasonic power of 800 W, the grain refinement was the maximum 32.1% and the proportion of the small-dimension (less than 20 µm) grains was increased from 53% to 67%. The ultrasonic vibration also contributed to the grain boundary transformation from low-angle to high-angle and increased the proportion of the recrystallized grains from 10% to 15%. With the increase of ultrasonic power, the microhardness, ultimate tensile strength, and elongation were increased first and then decreased, that of U-LDUW weldment were increased by 16.3%, 23.3% and 55.5% than that of LDUW. The results of this work provide a novel process method to enhance the comprehensive performance of LDUW weldments and expand the application of LDUW in repairing large-scale underwater structures. [ABSTRACT FROM AUTHOR]

Presence of adsorbed water on the solid surface gives significant influences on the tribological phenomena. This study aims to elucidate how the difference in surface roughness of austenitic stainless steel influences the amount of adsorbed water. Firstly, the necessary time for the adsorbed water to saturate on the surfaces with different roughness when relative humidity (RH) changed was determined by weighing method. Then, the saturated adsorbed water amount at different RH % was determined for the surfaces with different roughness. It was clarified that the rougher surfaces tend to require longer time for water adsorption to achieve the saturation level and adsorb more amount of water compared with smoother surfaces. • The amount of adsorbed water increases with the increase of surface roughness. • The amount of adsorbed water increases with the increase of environmental humidity. • The dependence of adsorbed water on relative humidity showed 3 phases. • Estimated thickness of adsorbed water was large enough to exert mechanical influences. [ABSTRACT FROM AUTHOR]

The magnetic abrasive finishing (MAF) process is an ultra-precision surface finishing process. In order to further improve the finishing efficiency and surface quality, the MAF process using an alternating magnetic field was proposed in the previous research, and it was proven that the alternating magnetic field has advantages compared with the static magnetic field. In order to further develop the process, this study investigated the effect on finishing characteristics when the alternating current waveform is a square wave. The difference between the fluctuation behavior of the magnetic cluster in two alternating magnetic fields (sine wave and square wave) is observed and analyzed. Through analysis, it can be concluded that the use of a square wave can make the magnetic cluster fluctuate faster, and as the size of the magnetic particles decreases, the difference between the magnetic cluster fluctuation speed of the two waveforms is greater. The experimental results show that the surface roughness of SUS304 stainless steel plate improves from 328 nm Ra to 14 nm Ra within 40 min.

Stainless steels (SUS) and dual-phase (DP) steels have tension-compression asymmetry (TCA) in mechanical responses to full loading cycles. This phenomenon can significantly influence sheet metal forming of such metals, however, it is difficult to describe this behaviour analytically. In this research, a novel analytical method for asymmetric elastic-plastic pure bending using the Cazacu–Barlat 2004 asymmetric yield function is proposed. It only uses material parameters in tension along with an asymmetry coefficient related to the yield function. Bending operations of SUS304 and DP980 are investigated as two case studies. In the pure bending for both SUS304 and DP980, moment–curvature diagrams are analytically obtained. Furthermore, linear and nonlinear springback behaviours of SUS304 are analytically investigated. Moreover, using the analytical model as a user-defined material, a numerical model is developed for both steels under pure bending. In the V-bending case of SUS304 with and without TCA effects, the springback behaviours of the material are investigated numerically. In addition, considering friction effects, the analytical method is further modified for predicting springback behaviours in the V-bending of 16 types of SUS304 with various strengths are determined. All the analytical and numerical results have good agreement with those experimental results from literature for validation.

Three materials SUS304, 9% Ni steel and Al 5083-O alloy, which are considered possible candidate for International Maritime Organization (IMO) type B Cargo Containment System, were studied. Monotonic tensile, fatigue, fatigue crack growth rate and Crack Tip Opening Displacement tests were carried out at room, intermediate low (-100 °C) and cryogenic (-163 °C) temperatures. The initial yield and tensile strengths of all materials tended to increase with decreasing temperature, whereas the change in elastic modulus was not as remarkable. The largest and smallest improvement ratio of the initial yield strengths due to a temperature reduction were observed in the SUS304 and Al 5083-O alloy, respectively. The fatigue strengths of the three materials increased with decreasing temperature. The largest increase in fatigue strength was observed in the Al 5083-O alloy, whereas the 9% Ni steel sample showed the smallest increase. In the fatigue crack growth rate test, SUS304 and Al 5083-O alloy showed a decrease in the crack propagation rate, due to decrease in temperature, but no visible improvement in da/dN was observed in the case of 9% Ni steel. In the Crack Tip Opening Displacement (CTOD) test, CTOD values were converted to critical crack length for the comparison with different thickness specimens. The critical crack length tended to decrease in the case of SUS304 and increase for the Al 5083-O alloy with decreasing temperature. In case of 9% Ni steel, change of critical crack length was not observed due to temperature decrease. In addition, the changing material properties according to the temperature of the LNG tank were analyzed according to the international code for the construction and equipment of ships carrying liquefied gases in bulk (IGC code) and the rules of classifications.

• High-performance printed circuit heat exchanger is fabricated by EAM. • Both filling height and profile are significantly improved by using current. • Recrystallization occurs due to the synergistic effect of deformation and current. • Dynamic recovery occurs and dislocation packing relieves at high-density current. • Current promotes homogeneous deformation due to elimination of 〈1 0 1〉 texture and rotation of 〈1 1 1〉 texture. The printed circuit heat exchanger (PCHE) with arrayed microchannel structures is ideal for the extreme thermal management of hypersonic flight vehicles. Electrically assisted manufacturing (EAM) has a remarkable predominance in fabricating microchannels on sheet metals. By conducting EA micro-embossing experiments at current densities of 20, 25, and 40 A/mm2, respectively, the filling behavior and microstructural evolution of SUS304 sheets under the influence of current were elucidated in this study. The results indicated that a higher current density shortens the initial extrusion stage's duration and facilitates the material flow transition to the filling stage. Moreover, the current can simultaneously enhance the filling height and profile quality by minimizing the stress and stress differential in the deformation region of the filling section. The results of electron backscatter diffraction (EBSD) demonstrated that recrystallization occurs due to the synergistic effect of deformation and current. The degree of recrystallization in different regions of the filling section has a huge discrepancy. The region beneath the tooth exhibits considerable recrystallization and contains abundant refined grains. At the current density of 20 A/mm2, a number of dislocations accumulated in the deformed grains, and the filling section mainly consisted of 〈1 1 1〉 fiber texture and 〈1 0 1〉 deformation texture. In the process of continual dynamic recovery and recrystallization, dislocation packing relives at the current density of 40 A/mm2, which is one reason for the increase in filling quality. The 〈1 1 1〉 texture and 〈1 0 1〉 deformation texture are weakened and rotate as the forming temperature rises. Additionally, the 〈1 0 1〉 texture transforms into a 〈0 0 1〉 recrystallized texture. The diminished 〈1 0 1〉 deformation texture, the rotated 〈1 1 1〉 texture, and the appearance of 〈0 0 1〉 recrystallized texture enhance the homogenous strain distribution of the filling section, which is an additional explanation for the improvement of filling quality at high-density current. Based on the above results, a high-performance PCHE prototype with a pressure bearing capacity of 23 MPa and a heat transfer coefficient of 22 kW/(m2·K) was manufactured by EAM, confirming that the EAM technique is capable of achieving high-quality and eco-friendly fabrication of the enhanced microchannels. [ABSTRACT FROM AUTHOR]

SUS304 and SUS430LX stainless steels were subjected to cyclic voltammetry (CV) in EMI-TFSI ionic liquid containing water at 5.5, 30, and 5000 ppm at room temperature. Structural changes of the passive film during CV were characterized by AES and TEM/EELS. Passive films after CV were mainly composed of Cr and Fe oxides similar to that formed in aqueous solutions. The thickness and Cr cation fraction of the passive film increased with increasing number of CV cycles. Furthermore, much Cr concentrated and thinner passive films were formed with less water content in EMI-TFSI. It is concluded that SUS304 and SUS430LX stainless steel are corrosion resistant in EMI-TFSI ionic liquid with a small amount of water. [ABSTRACT FROM AUTHOR]

It is well-known that the fatigue process is different depending on various kinds of applied stresses. To prevent accidents caused by material degradation such as fatigue, it is important to know the difference between causes of the fatigue process, such as pulsating tension stress as opposed to plane bending stress. The relationship between fatigue damage and remnant magnetization has been extensively researched using a thin-film flux-gate (FG) magnetic sensor for semi-stable austenitic stainless steel (SUS304 or ANSI304). Therefore, in this paper, the difference between the fatigue processes by pulsating tension fatigue and plane bending fatigue was investigated using the remnant magnetization method with a specimen made of SUS304. The remnant magnetization method with the FG magnetic sensor was non-destructively able to clarify the difference between the fatigue processes of SUS304 and the applied stress. [ABSTRACT FROM AUTHOR]

In this study, the effect of the metal salt generation bonding technique on the strength of a direct-bonded SUS304 stainless steel interface was investigated. SUS304 stainless steel surfaces were modified by boiling in 50% formic acid, and direct bonding was performed at a bonding temperature of 1023-1123 K under a pressure of 147 N (for a bonding time of 900 s). After direct bonding, the specimens were subjected to the peel test for evaluating their strength. As a result of the surface modification, bonded joints were obtained at bonding temperature of 30 K lower than that required for the unmodified surfaces, and the peel strength was comparable to that of the maximum load. On the basis of the experimental results, it was established that metal salt generation processing is effective for removing oxide films on SUS304 stainless steel. [ABSTRACT FROM AUTHOR]

The purpose of this study was to achieve high performance and high function of an industrial product under low cost. The fatigue test of SUS304/S35C and SUS304/S55C friction welded joints with flash was investigated by the rotating bending fatigue test. The experimental results were as follows. (1) The broken part of friction welded joints of SUS304/S35C and SUS304/S55C was changed by amplitude stress, its part was toe of flash of S35C and S55C when amplitude stress was low. And, in the case of the high amplitude, it was specimen parallel part of SUS304. (2) The stress concentration factor of toe of flash of S35C and S55C was the increased with an increase in upset pressure. This tendency was slightly in the case of SUS304, and in the case of carbon steel, it was increased remarkably with increase of carbon. (3) When amplitude stress was low, the broken part of S35C and S55C joints was toe of flash, this fatigue strength was decreased remarkably with an increase in upset pressure. This main reason was the increased stress concentration factor. (4) When amplitude stress was high, the broken part of the SUS304 was the parallel part and the reason was that it was red hot. Heat occurred because of internal friction and low thermal conductivity. But this red-hot temperature was prevented completely by dropping water at 50 ml/min. (5) When the parallel part the length of SUS304 was < 25 mm, the amplitude stress broken by red-hot temperature was increased with a decrease in the parallel part length. [ABSTRACT FROM PUBLISHER]

Intergranular stress corrosion cracking (IGSCC) in type SUS304 stainless steels, tested under pressurized water reactor (PWR) primary water conditions, has been characterized with unprecedented spatial resolution using scanning electron microscopy (SEM) and novel low-energy (~3kV) energy dispersive X-ray spectroscopy (EDX). An advancement of the large area silicon drift detector (SDD) has enhanced its sensitivity for X-rays in the low-energy part of the atomic spectrum. Therefore, it was possible to operate the SEM at lower accelerating voltages in order to reduce the interaction volume of the beam with the material and achieve higher spatial resolution and better signal-to-noise ratio. In addition to studying the oxide chemistry at the surface of intergranular stress corrosion cracks, the technique has proven capable of resolving Ni enrichment ahead of some crack tips. Active cracks could be distinguished from inactive ones due to the presence of oxides in the open crack and Ni-rich regions ahead of the crack tip. Furthermore, it has been established that SCC features can be better resolved with low-energy (3kV) than high-energy (12kV) EDX. The low effort in sample preparation, execution and data analysis makes SEM the ideal tool for initial characterization and selection of the most important SCC features such as dominant cracks and interesting crack tips, later to be studied by transmission electron microscopy (TEM) and atom probe tomography (APT). [ABSTRACT FROM AUTHOR]

Abstract: Polishing is a finishing process used to improve surface integrity by reducing surface roughness and residual stress caused by other machining processes. The recently developed electron beam polishing method was used in this study to improve surface quality. In this process, an electron beam with a maximum diameter of 60mm was applied for a few microseconds to melt and evaporate a metal surface. Al6061 and SUS304 metal plates were prepared with different geometric patterns and subjected to electron beam polishing. The surface roughness of the patterned SUS304 metal plate was significantly improved. However, the surface roughness of the patterned Al6061 metal plate became worse. Although the surface hardness decreased by approximately 10% on the re-solidified layers on both types of plates, the contact angle increased due to changes in surface morphology. The microstructure variation after the electron beam irradiation was also examined and compared with the thickness prediction of the re-solidified layer for Al6061 and SUS304 metal plates. [Copyright &y& Elsevier]

Abstract: The dissimilar butt welded joint of reduced-activation ferritic/martensitic steel (RAF/M) F82H and austenite stainless steel (AISI304 (SUS304)) were studied by friction stir welding. The effect of the position of the steels and tool plunging was considered in order to prohibit the mixing of the F82H and SUS304. When the dissimilar butt welding was performed such that the F82H plate was on the advancing side and the tool was plunged on the F82H side, defect-free joints could be successfully fabricated. Optical microscopy and EDX analysis were used to characterize the dissimilar joint microstructures and the interface. It was confirmed that the dissimilar joint formed no mixed structure and inter-metallic compounds. [Copyright &y& Elsevier]

V-bending test was conducted for sixteen different lots of austenitic stainless steel alloys, SUS304. The tensile flow stresses of all alloys were nearly identical to each other in the rolling and transverse directions. We found that the springback angles of all alloys were approximately 20% larger in TD-bending than RD-bending, where RD- and TD-bending refer to the modes of V-bending in which the direction of the bending stress is parallel to the rolling and transverse directions of the sheet, respectively. In order to clarify the cause of the asymmetry of springback behaviour between TD- and RD-bending, in-plane tension and compression tests were carried out for one of the alloys and a tension-compression asymmetry was observed. Consequently, we conclude that the difference in the springback angles between RD- and TD-bending is mainly caused by the significant decrease of the flow stress in the rolling direction due to the Bauschinger effect. [ABSTRACT FROM AUTHOR]

A new monitoring method was proposed to study the mechanism of stress corrosion cracking (SCC). This method is a combination of the chloride droplet SCC monitoring system and the measurement system of continuous acoustic emission (AE) waveform, which were developed by our group. With the present method, the SCC was carried out on the thin plate of SUS304 stainless steel with a small MgCl2 droplet. The experiments show that the measured AE waveform had small amplitude and large noise component based on the time–frequency analysis of continuous waveform. A noise filtering parameter was applied to the measurement of continuous AE waveform. Cumulative AE events and peak amplitude distribution of two specimens were indicated similar tendency during testing time. Those AE signals may correspond to crack propagation and arrest. Therefore, the new SCC testing method of small MgCl2 droplet with high sensitivity AE monitoring demonstrated the analyzing capability of the SCC process. [ABSTRACT FROM AUTHOR]

Abstract: Joining has been carried out between FCD450/SUS304 samples to investigate the influence of joining conditions on joint properties, by an impact-electric current discharge joining machine that can apply impact load and electric current simultaneously. High joint strength is achieved in samples joined under early or simultaneous start of electric current without pulse superimposition in relation to application of impact force. Fracture stress and area fraction of the actually joined portion at the FCD450/SUS304 interface increase with amount and period of electric current flow and with impact load, because joining state is improved at the joint interface. [Copyright &y& Elsevier]

Joining has been carried out between FCD450/SUS304 samples to investigate the influence of joining conditions on joint properties, by an impact-electric current discharge joining machine that can apply impact load and electric current simultaneously. High joint strength is achieved in samples joined under early or simultaneous start of electric current without pulse superimposition in relation to application of impact force. Fracture stress and area fraction of the actually joined portion at the FCD450/SUS304 interface increase with amount and period of electric current flow and with impact load, because joining state is improved at the joint interface. [Copyright &y& Elsevier]

High‐resolution transmission electron microscopy and electron energy‐loss spectroscopy observations were performed for the first time at surface films segregated by low temperature treatment from an amorphous layer made by a co‐sputtering deposition technique. It was confirmed that the layer was hexagonal boron nitride having c‐axis perpendicular to the material surface, presumably explaining its features of low occlusion and adsorption of gases as obtained from other experiments. In situ observation of layer growth under high intensity electron irradiation was also performed and it was observed that the layers grow by changing their bonding with different layers. [ABSTRACT FROM PUBLISHER]

The magnetic abrasive finishing (MAF) process is an ultra-precision surface finishing process. In order to further improve the finishing efficiency and surface quality, the MAF process using an alternating magnetic field was proposed in the previous research, and it was proven that the alternating magnetic field has advantages compared with the static magnetic field. In order to further develop the process, this study investigated the effect on finishing characteristics when the alternating current waveform is a square wave. The difference between the fluctuation behavior of the magnetic cluster in two alternating magnetic fields (sine wave and square wave) is observed and analyzed. Through analysis, it can be concluded that the use of a square wave can make the magnetic cluster fluctuate faster, and as the size of the magnetic particles decreases, the difference between the magnetic cluster fluctuation speed of the two waveforms is greater. The experimental results show that the surface roughness of SUS304 stainless steel plate improves from 328 nm Ra to 14 nm Ra within 40 min. [ABSTRACT FROM AUTHOR]

Structural materials such as stainless steel (SUS) in nuclear reactor are exposed by the environment of ionizing radiations so that their corrosion and degradation take place. These radiation effects depend strongly on the quality of radiation (energy, kind) around the materials. The metallic materials with various thickness have been examined in previous works on the radiation effects, but not with a common thickness. The different thickness would give the different radiation quality, leading to the different results of radiation effects on the materials. In this work, when radiation sources of 137Cs, 90Sr and 90Y were assumed to be put in the front of a plain SUS304 plate as a typical material submerged in water, energy spectra of secondary photons and electrons at the front and back sides of plate were simulated with changing the thickness of plate, and spacing between the source and plate by using a Monte Carlo calculation code of PHITS. In the case of 137Cs gamma-ray (monochromatic 662 keV), the energy spectra at the front side was smaller than those at the back side due to the existence of plate. Then the dependence of spectra on the plate thickness was observed more clearly at the back side than at the front side. In the cases of 90Sr and 90Y beta-rays (maximum 546 and 2284 keV), the energy spectra were clearly different from those in the case of gamma-ray. At the front side, the energy and flux of electrons were higher than those of photons. Also, the energy spectra of electrons and photons were not dependent on the plate thickness. At the back side, the energy and flux of electrons were much lower than those of photons reversely. It was clearly shown how the energy spectra of photons and electrons varied with the incident radiation type, the spacing, and the thickness. The average energies of secondary radiations were further estimated, and the changes of incident radiation to the secondary ones were discussed especially in terms of the lowering of radiation energy. • Oxidizing radiolysis products affect structural steels within their reachable region. • Primary radiations are converted to secondary ones with lower energies in the region. • The energy spectra of secondary radiations depend on the thickness of steel plate. • The energy spectra depend on spacing between the primary radiation source and plate. • The energy spectra at the front and back sides of plate become different each other. [ABSTRACT FROM AUTHOR]