Microstructural characteristics in tough pitch copper for revealing the work hardening region

Okayasu, Mitsuhiro,Taki, Tatsuya,Takasu, Satoshi,Takeuchi, Shuhei,Shiraishi, Tetsuro Techno-Press 2012 Advances in materials research Vol.1 No.4

To reveal localized plastic deformation zones in a tough pitch copper, the etching characteristics of a copper sample have been examined. The etching was carried out on a sample surface using an etchant consisting of 25 ml nitric acid solution and 75 ml water. To clarify the plastic deformation zone, the sample deformed plastically was heated to between $250^{\circ}C$ and $300^{\circ}C$ before the etching process. This is due to a change of the microstructure and crystal orientation in the plastic deformation zone producing recrystallized small grains. In this case, the plastically deformed zone is severely etched, whereas the undeformed zone is only slightly etched. Identification of the details of the deformation zone from the etching is further discussed.

Mechanical and wear properties of Cu-Al-Ni-Fe-Sn-based alloy

Okayasu, Mitsuhiro,Izuka, Daiki,Ninomiya, Yushi,Manabe, Yuki,Shiraishi, Tetsuro Techno-Press 2013 Advances in materials research Vol.2 No.4

To obtain bronze with good mechanical properties and high wear resistance, a new bronze (CADZ) is proposed on the basis of various fundamental information. The CADZ consists of the elements Al10.5, Fe4.2, Sn3.7 and Ni3.1, and its design is based on Cu-Al10.5 alloy. The Cu-10.5%Al is very hard and brittle. To obtain the high material ductility of the Cu-10.5%Al alloy, an attempt was made to add a few percent of Sn. Moreover, to make high strength of the Cu alloy, microstructure with small grains was created by the proper amount of Fe and Ni (Fe/Ni = 0.89). The mechanical properties of the CADZ sample have been examined experimentally, and those were compared with commercial bronzes. The tensile strength and wear resistance of CADZ are higher than those for commercial bronzes. Although the ductility of CADZ is the lower level, the strain to failure of CADZ is about 2.0~5.0% higher than that for the Cu-Al10.5 alloy. Details of the microstructural effects on the mechanical properties in the CADZ sample were further discussed using various experimental results.

Effects of loading conditions on the fatigue failure characteristics in a polycarbonate

Okayasu, Mitsuhiro,Yano, Kei,Shiraishi, Tetsuro Techno-Press 2014 Advances in materials research Vol.3 No.3

In this study, fatigue properties and crack growth characteristics of a polycarbonate (PC) were examined during cyclic loading at various mean stress (${\sigma}_{amp}$) and stress amplitude (${\sigma}_{mean}$) conditions. Different S vs. N and da/dN vs. ${\Delta}K$ relations were obtained depending on the loading condition. The higher fatigue strength and the higher resistance of crack growth are seen for the PC samples cyclically loaded at the higher mean stress and lower stress amplitude due to the low crack driving force. Non-linear S - N relationship was detected in the examination of the fatigue properties with changing the mean stress. This is attributed to the different crack growth rate (longer fatigue life): the sample loaded at the high mean stress with lower stress amplitude. Even if the higher stress amplitude, the low fatigue properties are obtained for the sample loaded at the higher mean stress. This was due to the accumulated strain energy to the sample, where severe plastic deformation occurs instead of crack growth (plasticity-induced crack closure). Shear bands and discontinuous crack growth band (DGB) are observed clearly on the fracture surfaces of the sample cyclically loaded at the high stress amplitude, where the lower the ${\sigma}_{mean}$, the narrower the shear band and DGB. On the other hand, final fracture occurred instantly immediately after the short crack growth occurs in the PC sample loaded at the high mean with the low ${\sigma}_{amp}$, i.e., tear fracture, in which the shear bands and DGB are not seen clearly.

Effect of 8% lidocaine spray on the sensory and pain thresholds of the skin of the face and hands evaluated by quantitative sensory testing

Okayasu, Ichiro,Komiyama, Osamu,Ayuse, Takao,De Laat, Antoon The Korean Dental Society of Anesthsiology 2018 Journal of Dental Anesthesia and Pain Medicine Vol.18 No.6

Background: Recently, we examined the effects of 2% lidocaine gel on the tactile sensory and pain thresholds of the face, tongue and hands of symptom-free individuals using quantitative sensory testing (QST); its effect was less on the skin of the face and hands than on the tongue. Consequently, instead of 2% lidocaine gel, we examined the effect of 8% lidocaine spray on the tactile sensory and pain thresholds of the skin of the face and hands of healthy volunteers. Methods: Using Semmes-Weinstein monofilaments, QST of the skin of the cheek and palm (thenar skin) was performed in 20 healthy volunteers. In each participant, two topical sprays were applied. On one side, 0.2 mL of 8% lidocaine pump spray was applied, and on the other side, 0.2 mL of saline pump spray was applied as control. In each participant, QST was performed before and 15 min after each application. Pain intensity was measured using a numeric rating scale (NRS). Results: Both the tactile detection threshold and filament-prick pain detection threshold of the cheek and thenar skin increased significantly after lidocaine application. A significant difference between the effect of lidocaine and saline applications was found on the filament-prick pain detection threshold only. NRS of the cheek skin and thenar skin decreased after application of lidocaine, and not after application of saline. Conclusion: The significant effect of applying an 8% lidocaine spray on the sensory and pain thresholds of the skin of the face and hands can be objectively scored using QST.

A pilot study of pain-relieving effect of Goreisan in glossodynia with dry mouth symptoms: an open-label single-group study

Okayasu Ichiro,Mizuki Tachi,Sanuki Takuro,Kurata Shinji,Ayuse Takao 경희대학교 융합한의과학연구소 2021 Oriental Pharmacy and Experimental Medicine Vol.21 No.2

Goreisan might be a medicine to cure the pain caused by thirst and dry mouth symptom of glossodynia. All registered patients were treated with Goreisan by taking 7.5 g / day (min 3) for 2 weeks. Self-filled Visual Analogue Scale (VAS) and tongue perception test by nomo-filament. Furthermore, daily self-filled VAS evaluation was required patients’ home for two weeks during Goreisan administration. There was 57% of patients (8/14) showed “improved” after administration of 2 weeks Goreisan administration based on the criteria of 20% reduction of VAS compared to baseline. Self-filled VAS score was significant low (p = 0.006) at 2 weeks evaluation at second visit and remained lower level through 4 week observation periods compared to baseline value. QST significantly increased after 2 weeks administration of Goreisan (p = 0.008) and remained higher level through 4 week observation periods compared to baseline value. There was significant reduction of daily self-filled VAS patients’ home at day 3 and day 13 ~ day 14. (p < 0.05). There is a weak positive and negative correla-tion between Barometric pressure (hPa) and self-filled VAS scale (cm) in each patients. The administration of Goreisan for two weeks lead to significant reduction of pain perception based on the evaluation of Self-filled pain scale (VAS) and tongue perception test (QST). There is correlation between barometric pressure and self-filled VAS scale. This fact might indicate that Goreisan would be the alternative treatment for glossodynia patients. Goreisan would be a successful alternative treat-ment modality forglossodynia patients.Trial registration Current Controlled trials was registered with the UMIN Clinical TrialsRegistry (identifier: UMIN000035965, 02.21.2019).

Hydrogen Embrittlement of Austenitic Stainless Steels with Different Surface Treatments

Okayasu Mitsuhiro,Wen Hao,Kondo Ryutaro 한국강구조학회 2024 International Journal of Steel Structures Vol.24 No.3

This study evaluated the eff ect of surface conditions on the hydrogen embrittlement (HE) characteristics of SUS304 austenitic stainless steel, as SUS304 is one of the candidate structural materials for hydrogen energy systems. Various machining processes, including milling (ML), shot peening (SP), and cold rolling (CR), were employed to modify the surface roughness, internal strain, and microstructural characteristics of the test sample. Namely, this approach was conducted as the surfaceabsorbed hydrogen is related to eff ective hydrogen: a high internal strain was obtained in the entire CR area along with a rough surface, while SP and ML samples displayed high strain levels near the surface. The strain value was refl ected in the hardness level due to their work hardening and strain-induced martensite formation. Concerning this, the hardness values of CR and SP samples were higher than 6 and 2 times the as-received samples. The hydrogen content charged to the samples was contingent upon the strain level: higher strain corresponded to elevated hydrogen content, particularly in CR samples. Despite the notable high hydrogen content in CR samples, HE was not detected in the tensile test. Conversely, even with a low hydrogen content, severe HE was observed in all samples during the fatigue test. The susceptibility of stainless steel to HE proved sensitive to cyclic loading, wherein surface-absorbed hydrogen migrated to the crack tip during cyclic loading. Detailed discussions on the reasons for these observations are provided based on the experimental results.

Effects of cyclic loading on fatigue properties of austenite stainless steel

Mitsuhiro Okayasu,Hironobu Fukui 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.9

Fatigue properties of stainless steels have been investigated by various researchers. The present work examined fatigue properties undervarious cyclic loading conditions to determine the significant factors of loading condition to fatigue strength (se). From this approach,no clear frequency effects on the S-Nf relation were detected, but clear R-ratio effects were identified on fatigue strength. A higher R-ratioyielded higher se, and a clear correlation was observed between R-ratio and endurance limit. A different trend was observed for the S-Nfcurve when the stress value on the ordinate of the S-Nf relation was plotted using the maximum tensile stress (smax). However, the S-Nfcurves obtained overlaid each other when using stress amplitude (sa) instead of smax. Fatigue properties were analyzed further using severalrelations proposed previously, such as modified Goodman relation. In this case, the fatigue data obtained were clearly approximatedby an elliptical relation. Severe microstructural damage arising from plastic deformation was observed in the sample fractured under theR = −1 condition, where striation was a main failure mode. In contrast, no clear microstructural damages were observed in the samplesfractured at R = 0.1 even when a higher maximum tensile stress was applied (e.g., smax = 60% sUTS), where ripple-like failure was thedominant feature.

The effects of artificial asperities on crack closing behavior in quenched and tempered medium carbon steel

Mitsuhiro Okayasu,Zhirui Wang 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.10

To better understand the effect of an asperity on crack closure behavior, K-CMOD relations were examined using artificial asperity/wedge, inserted into the fatigue crack in a three point bending specimen made of a hardened medium carbon steel. Experimental results revealed that the unloading phase of the K vs. CMOD curve exhibited a concave shape if soft artificial asperity (Al alloy) was inserted,signifying acceleration in the CMOD decrease at zero applied load. This was mainly related to elastic and plastic deformation in the wedge material during the unloading process. On the contrary, the linear unloading portion of K vs. CMOD was obtained as hard asperity (high carbon steel) was employed, which specified deceleration in the CMOD decrease at zero applied load, where the only elastic deformation in the asperity was affected. From their unloading curves, the severity of crack closure or ?Keff value was found to be related to the strength of the asperity material. The values of ?Keff were examined in two different ways, e.g., (i) the remote displacement method and (ii) the adjusted compliance ratio method (ACR). The ?Keff value, measured using both approaches, decreases with increasing wedge strength, such as hardness and yield strength. The rate of reduction in <Keff was, however, changed depending on the manner of ?Keff examination, in which the ?Keff decreased at a higher rate for the compliance ratio method and at a lower rate for the remote displacement method. The reason for this is discussed in the present work.

Newly developed walking apparatus for identification of obstructions by visually impaired people

Mitsuhiro Okayasu 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.6

In this work, two visual systems to help visually impaired people walk were developed: the first is a white cane with a non-contact detection system, and the second is a three-dimensional (3D) visual system. In place of the sense of sight, the sense of touch, either via vibration or of pins, can relay information on objects and obstacles around people. In a white cane non-contact detection system, two sets of ultrasonic sensors and vibrators, respectively, are employed to indicate the positions of both low- and high-level obstructions in front of the visually impaired person. When objects are detected by the sensor, the vibrator is strongly activated. In this system, the range of obstruction detection can be adjusted between 0.5 m and 5.5 m. By comparison, the 3D visual system uses two different components, an infrared camera sensor to detect obstructions and a tooling apparatus, incorporating a number of 1 mm diameter pins, by which their 3D shapes are derived. The pins are arranged in a 10×10 matrix and move longitudinally between the retracted and extended positions based on the depth data between the infrared sensor and the obstruction. Pins are elongated individually, so that each pin tip represents a specific area of the outer surface of the object. This tactile 3D image can provide effective object information.

Polysulfamide Acid Membranes and their Water-Free Proton Conductivity

Teruyuki Okayasu,Takahiro Tago,Hiroyuki Nishide,Hiroko Endo,Atsuo Sonai 한국고분자학회 2006 한국고분자학회 학술대회 연구논문 초록집 Vol.2006 No.10