Journal of the Society of Materials Science, Japan
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
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Volume 41, Issue 465
Displaying 1-27 of 27 articles from this issue
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  • Polymer Alloys of Engineering Plastics
    Shin-ichi IZAWA
    1992 Volume 41 Issue 465 Pages 789-797
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.789
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  • Technical Topic
    1992 Volume 41 Issue 465 Pages 798-803
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.798
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  • Comparison of Fatigue Behavior of Polyamides with Different Molecular Structures
    Akihiko MORIKAWA, Takatoshi ISHIGAKI, Shuji TSUCHIKAWA, Shinichi KIMUR ...
    1992 Volume 41 Issue 465 Pages 804-807
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.804
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    In order to clarify the differences of fatigue behavior of polyamides with different molecular structures, the stress-controlled fatigue tests were carried out on polyamide 46, polyamide 66 and polyamide 6 by means of tension-tension type fatigue tester. Fatigue lifetime of polyamides 46 and 66 was longer than that of polyamide 6 under the stress amplitude investigated.
    Polyamides 46 and 66 showed a thermal (ductile) failure behavior in large stress amplitude region and a brittle failure at smaller stress amplitudes. Polyamide 6 showed only the thermal failure behavior at stress amplitude tested in this study. The transition stress level from termal to brittle failure for polyamide 46 was higher than that for polyamide 66.
    Fatigue lifetime of polyamide 46 under constant stress amplitude was found to be independent of test frequency, while that of polyamide 66 and 6 decreased with test frequency.
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  • Weldline Properties in Fiber Reinforced Polypropylene Injection Molded Plaques
    Kiyotaka TOMARI, Toshihiko HARADA, Hiroyuki HAMADA, Zenichiro MAEKAWA, ...
    1992 Volume 41 Issue 465 Pages 808-814
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.808
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    The strength properties of weldline part have been studied in fiber reinforced polypropylene injection molded plaques. Mechanical tests were carried out for two types of weldline, such as (1) weldline formed by counter flows from double gates, and (2) weldline formed by concurrent flows divided by an insert core in a cavity. Thin plaques were injection molded using either the double gate mold or the single gate mold with a circle insert core. Cylinder temperature and mold temperature were kept constant, and injection speed and holding pressure were varied within the appropriate range. The effects of “counter flow” type weldline on the strength depended on molding conditions, injection speed and holding pressure, while the “concurrent flow” type weldline was independent of the molding conditions. As the strengths of specimens with weldline, weld strengths, were almost same for both types of weldline, injection molding can be designed based on the weld strength using the double gate dumbbell tensile bars. Further the concurrent flow weld strength was influenced by the specimen geometry. The weld strength with a half of core hole contour reduced more remarkably than the one without it. Because the contour affected as a notch and induced the stress concentration. And near the hole, the difference of orientation angle along weldline, the local anisotropy, was larger, when the core diameter was wider. Thus, the weld strength of 20mm hole specimen was lower than that of 10mm hole specimens. These results indicate that geometries must be taken into consideration in order to estimate the properties of weldline.
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  • Mechanical Properties of Tetrafunctional Epoxy Resin Filled with Graphite Fluorides
    Katsutoshi TANAKA, Muneaki YAMAGUCHI
    1992 Volume 41 Issue 465 Pages 815-820
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.815
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    Several mechanical properties and morphology of tetrafunctional epoxy resins (Tetrad(R) D and X cured with hexahydrophtharic anhydride (HHPA), abbreviated as EP·D and EP·X) filled with graphite fluoride powders (GF) such as (C2F)n (C2F) and (CF)n (C1F) were studied using a Rheovibron, an Instron tester, a Vickers hardness tester, and a SEM. C2F and C1F were added to EP·D and EP·X up to 30wt%. C2F treated with six coupling agents (CA) was added to EP·D by 30wt%. The GFs were distributed randomly in all the specimens. The glass transition temperature (Tg) and the storage modulus (E') of all the GF-filled specimens became larger with increasing content of GFs. The filling effect of GFs on the E' of the EP·D and EP·X filled with GFs was smaller than of difunctional epoxy resin (Epikote(R) 828 cured with HHPA). The compressive strength values (σc) of the C1F-filled specimens were larger than those of the C2F-filled specimens. The Vickers hardness values (Hv) of the GF-filled EP·D increased and those of the GF-filled EP·X decreased remarkably with increasing content of GFs. The effects of coupling treatment of CAs for C2F on E', σc and Hv of the filled specimens were different depending upon the kind of CA.
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  • Influence of Gelling Condition on Mechanical Properties of Simultaneous Interpenetrating Polymer Networks from Epoxy Resin/Polybismaleimide Systems
    Katsuyoshi IISAKA
    1992 Volume 41 Issue 465 Pages 821-826
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.821
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    Simultaneous Interpenetrating Polymer Networks (SIN's) were prepared from epoxy resin and bismaleimide (BMI) under various gelling conditions of both resins. Dynamic mechanical and tensile properties were examined as a function of a gel-time ratio (Gt) of the epoxy resin to that of BMI for the SIN's with constant content of BMI and, for comparison, as a function of concentration of BMI for the truely simultaneous IPN's. The rubbery plateau modulus considerably increased with increasing BMI content, but it was not dependent on Gt. The modulus behavior with a content of BMI followed nearly the Budiansky's and Davies's equations. On the other hand, the Tα decreased with increasing Gt at Gt>0.5, while it was nearly constant at Gt<0.5. This suggests that the faster the polymerization rate is for the BMI component compared with the epoxy resin, the less the miscibility between both components is. The tensile strength was maximum at the condition of nearly simultaneous gelation. The maximum seems to yield from the most densification of molecular packing attained by the greatest molecular mixing.
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  • Release Behavior of Antibacterial Drugs from Hydrophilic Segmented Polyurethaneurea
    Yuko IKEDA, Shinzo KOHJIYA, Shoichi TAKESAKO, Shinzo YAMASHITA
    1992 Volume 41 Issue 465 Pages 827-833
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.827
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    Blood-compatible segmented polyurethaneureas were evaluated as drug delivery matrices using crystal violet (CV), benzethonium chloride (AC) and acrinol (AC) as model drugs. The polymers were synthesized from ABA-type triblock copolyethers as prepolymers, where A stands for poly (oxyethylene) and B for poly (oxytetramethylene). Microphase separation was observed in the polyurethaneureas, including drug-doped ones. CV dissolved more in the hard segment domains than in the soft segment matrix, whereas BC easily dissolved in the soft segment matrix. AC dissolved in both phases. The drug release behaviors from these polymer films were analysed by the exponent relation Mt/M∞=ktn, where k and n are constants and Mt/M∞ is the fraction of drug released until time, t. The constant k increased with poly (oxyethylene) content, i.e. with the increase of swelling in water. The constant n was found to be ca. 0.5 in many samples, which suggests that the release of drugs from these polymers is explained by the Fickian diffusion model. However, the mechanism became non-Fickian with the increase of swelling of the devices in CV and BC systems. This observation seems to be due to the heterogeneous dissolution of drug in the microphase separated structure.
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  • Durability of Epoxy Resin Coating in Some Inorganic Acid Environments
    Takayuki IGUCHI, Satoshi OKUDA
    1992 Volume 41 Issue 465 Pages 834-838
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.834
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    One of the definitions of lifetime of organic coating is considered as the time at which adhesion between the coating layer and its substrate is lost. In this paper, the durability of epoxy coating under several acidic environments was examined by the measurements of liqid penetration and adhesive strength.
    Coating resin degraded by a chemical reaction in concentrated acid, so the lifetime of coating decreased. On the other hand, epoxy resin itself was stable to water, but water penetrated into the epoxy resin layer. This water weakened the adhasive force between the coating layer and its substrate physically, and became one of the factors controlling corrosion of substrate. So the lifetime of coating was shortened. Consequently, the epoxy coatings had a long life in dilute acid.
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  • Aqueous Solutions, Bioscience and Biotechnology at High Pressure
    Yoshihiro TANIGUCHI
    1992 Volume 41 Issue 465 Pages 839-848
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.839
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  • Variations of Strain and Stress in the Vicinity of Crack Tip due to Crack Closure and Measurement of Crack Closure Points
    Chobin MAKABE, Hideo KANESHIRO, Shin-ichi NISHIDA
    1992 Volume 41 Issue 465 Pages 849-854
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.849
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    The local stress and strain in the vicinity of crack tip were calculated by means of a finite element method to examine the measuring method of crack closure points. The fatigue crack closure behavior affected the local stress σx of cracking direction much more than the local stress σy, of loading direction in the vicinity of crack tip. The diagram between the nominal stress σ representing cyclic loading and σx had some inflection points. One of them well coincided with the crack opening point. However, some undesirable inflection points due to plastic constraint or crack blunting etc. were also found on the σ-σx diagram. On the other hand, the diagram between σ and the local shear stress τ in the vicinity of crack tip was found to have clear inflection points related to the crack closure behavior. It is expected that the crack closure points can be measured easily with an adequate strain function in the vicinity of crack tip.
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  • Microstructure and Mechanical Properties of Polycrystalline MgO Prepared by Hot-forge Processing
    Toshihiko NISHIDA, Hideaki FUJIOKA, Katsumi ADACHI, Kazuyori URABE
    1992 Volume 41 Issue 465 Pages 855-860
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.855
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    Ultra fine MgO powder prepared by oxidation of Mg vapor was encupslated in a Mo mold with dimensions of O.D.30φ-I.D.10φ×30hmm. The mold was preheated at 1300°C for 10 minutes, and then, immediately press-forged under uniaxial compressive load. The particle size of the starting powder (0.001μm) grew to 0.3-0.4μm during the preheating, but the grown particles were broken down by the mechanical fracture effect in the press-forge process and a dense polycrystal with smaller grain size (0.1-0.15μm) was obtained by a masstransport mechanism. However, the polycrystalline MgO obtained did not show satisfactory mechanical properties, because of some stored internal stress around the grain boundary. A polycrystalline MgO with good mechanical properties was obtained after annealing the press-forged body at a relatively low temperature of 800-1000°C for few hours to remove the strain. An attempt was made to understand clearly the above experimental results. It was also emphasized the importance to develope a new technique for sintering the ultra fine ceramic powders.
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  • Deformation Mechanism of KCl Single Crystal by Spherical Indentor
    I. Indentation with Steel Ball
    Shinzo KOBAYASHI, Hideto KUSUNOKI, Sei MIURA
    1992 Volume 41 Issue 465 Pages 861-866
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.861
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    The indentation test is probably the simplest method of estimating the strength of material under the frictional condition that the asperity tips are pressed into other body and that wear debris are scratched between two bodies. With the advancement of techniques of revealing dislocations in crystals, it has been thought possible to obtain a right understanding of the deformation in the material with a single crystalline structure caused by indentation.
    In the present study, KCl single crystal was indented with a steel ball to examine the dislocation structures associated with indentation at various loads. The slip systems and the range of deformed area were investigated in detail on the indented surface and on its cross section by using a dislocation etching technique.
    The results obtained are as follows:
    (1) The deformed area on the indented surface consists of a circular high dislocation density area and the area of comparatively low dislocation density shaped like wings and extended in the ‹110› and ‹100› directions.
    (2) Dislocation patterns on the indented surface and on its cross section consist of etch pit rows that belong to the {110}90 and {110}45 planes, respectively.
    (3) The plastic deformation range is affected by the diameter of indentor under comparatively high loads, but not under exceedingly low loads.
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  • Deformation Mechanism of KCl Single Crystal by Spherical Indentor
    II. Scratch with Steel Ball
    Shinzo KOBAYASHI, Hideto KUSUNOKI, Sei MIURA
    1992 Volume 41 Issue 465 Pages 867-873
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.867
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    In case that two surfaces of machine elements which have surface roughness produced by grinding or turning are scratched each other, the wear occurs by repeated scratches between asperity tips or wear debris. Therefore, in order to elucidate the mechanism of friction or wear, the deformation mechanism caused by scratching of minute asperities should be revealed.
    From the view point that it is effective to use single crystal of metallic or nonmetallic material to study this problem from the microscopic approaches on dislocation levels, in this study a smooth surface of KCl single crystal was scratched with a spherical indentor. As the scratch directions ‹110› and ‹100› were chosen. The deformation mechanism was discussed by observing the dislocation patterns on the scratched surface and on its cross section.
    The results obtained are as follows:
    (1) The width of the scratched track was larger in the ‹100› scrach than in ‹110› scratch, whereas the range of plastic deformation was larger in ‹110› scratch.
    (2) The plastic deformation produced by scratch was composed of a continuous pattern of the deformations produced by indentation.
    (3) The active slip system of dislocations was mainly {110}90, ‹110› on the scratched surface and {110}45, ‹110› on the cross section perpendicular to the surface, respectively.
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  • Deformation of KCl Single Crystal by Spherical and Pyramidal Indentors
    Shinzo KOBAYASHI, Tatsuya OKUI, Sei MIURA
    1992 Volume 41 Issue 465 Pages 874-879
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.874
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    In order to elucidate the mechnism of friction and wear, it is necessary to have a knowledge on deformation in materials produced by invasion of sharp projections or wear particles.
    In this study, the cleaved faces of KCl single crystal were indented with a steel ball or a Vickers diamond indentor. The deformation and hardness around the indentation were examined from macroscopic viewpoints, and the dislocation patterns were observed from microscopic one. The results obtained are as follows:
    (1) The indents formed on the indented surfaces with a ball or a pyramid were not perfectly circular nor square in shape due to the crystal anisotropy.
    (2) The appearances of the pile-up and sink-in around indents were clarified.
    (3) The strain hardening around the indent was more active in the ‹110› direction than in the ‹100›.
    (4) The deformed area on {100} face with a ball or pyramidal indentor consisted of a high dislocation density range and a wing shaped area of comparatively low density extended along the ‹110› and ‹100› directions.
    (5) The hardness and the dislocation density were related each other.
    (6) The etch pit patterns in the cleaved cross section were observed on {110}45 faces.
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  • Analytical Study of the Effect of Interfacial Slip on Stress Singularity on Interface of Bonded Material
    Masato MURATA, Yoshihiko MUKAI, Hideki HIRAMATSU
    1992 Volume 41 Issue 465 Pages 880-886
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.880
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    The effects of plastic deformation and interfacial slip on stress singularity near an interfacial crack and the end of bonded joint were studied by FEM with bond elements which had a feature of stress field on an interfacial plane. The results obtained are as follows: The solutions obtained by FEM coincided with the analytical ones using an image stress function proposed by other investigators. In the case that plastic deformation was induced near the interfacial crack tip, the singularity term decreased with work hardening coefficients. In addition, when a slip deformation occurred at the bonded interface, the analytical solutions by FEM approached to those of a homogeneous body. On the other hand, the stress singularity field near the end of bonded material disappeared by slip deformation.
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  • Elastic-plastic Analysis on the Growth of an Interfacial Crack
    Shigeru AOKI, Xue-Fu LUO
    1992 Volume 41 Issue 465 Pages 887-891
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.887
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    An elastic-plastic finite element simulation of the growth of a crack on an interface between dissimilar materials was performed. The small scale yielding condition was assumed and the bonding strength of the interface was taken to be large. The Gurson's constitutive equation for elastic-plastic porous materials and the Tvergaard's element vanish technique, in which an element is vanished when the microvoid volume fraction reaches a critical value, were employed. The results obtained are as follows:
    (1) The J1c (the value of J-integral at crack initiation) for an interfacial crack is much lower than that for a crack in a homogeneous material.
    (2) The crack grows in a softer material near the interface remaining a bit of the material on the interface.
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  • Fracture Toughness and Transition of Fracture Behavior of Silicon Nitride at Elevated Temperatures
    Nobuyuki MIYAHARA, Yoshiharu MUTOH, Kohei YAMAISHI, Tsuneo OIKAWA
    1992 Volume 41 Issue 465 Pages 892-898
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.892
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    Fracture toughness tests were carried out on HIP-sintered silicon nitride at elevated temperatures. The fracture toughness gradually decreased with an increase in temperature up to 1200°C. In the temperature range from 1200°C to 1275°C, a steel-like brittle-to-ductile transition of fracture toughness was observed: the fracture toughness rapidly increased from 4MPa√m to 8MPa√m. Above these temperatures, stable crack growth was observed. From the detailed observation of the stable crack growth region, β-Si3N4 particles were found to be oriented in the tensile direction. The stable crack growth occurred accompanying with bridging and pulling out of β-Si3N4 particles. The transition behavior of fracture toughness results from the transition of fracture mechanism from the stresscontrolled intergranular fracture to the pulling-out of β-Si3N4 particles with shear deformation of intergranular glass phase. The transition temperature was thought to be consistent with the softening point of the intergranular glass phase. The same transition behavior of fracture mechanism was found in the bending strength test.
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  • Fracture Toughness Evaluation of Mullite (3Al2O3·2SiO2)Having Three Different Microstructures
    Tatsuo SAKAI, Asish GHOSH, Richard C. BRADT
    1992 Volume 41 Issue 465 Pages 899-905
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.899
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    The fracture toughness of stoichiometric mullite samples having three different microstructures was examined by using the chevron-notched specimen technique and Vickers indentation method. The results obtained by these procedures were compared with each other, mainly focussing on the applicability of the current equations for the fracture toughness evaluation by the indentation method. Among them, the most preferable equation was finally confirmed along with some fundamental requirements to measure the fracture toughness through this convenient technique. Furthermore, the effects of microstructure on the crack growth resistance and the fracture toughness were discussed based on the experimental results.
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  • Monte-Calro Simulation of the Tensile Strength in a Unidirectional Fiber Reinforced Metal Matrix Composite Including the Effect of Dynamic Behavior Caused by Fiber Breaks
    Koichi GODA, Koichi KITAHARA, Hideharu FUKUNAGA
    1992 Volume 41 Issue 465 Pages 906-912
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.906
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    A Monte-carlo simulation technique was applied to investigate how the dynamic behavior caused by fiber-breaks affects the tensile failure process and the tensile strength of unidirectional fiber reinforced metals. A shear-lag model was used as the stress analysis method, and the solution for the equation of motion was obtained by the semi-discrete analysis. Such an analysis technique was taken into the simulation procedure, based on the rmin method as proposed in the previous report. Conditions of uniaxial tension in a mono-layer of boron-aluminum composite were simulated fifty times and compared with the case in which the fibers break statically. The results showed that many of the simulated failure processes are quite the same as in the case of the static fiber-breaks, but some of the failure processes indicate the more noncumulative mode. Also, the average of the simulated tensile strengths did not change appreciably and the coefficient of variation increased slightly, in comparison with the case of the static fiber-breaks.
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  • Crack-Tear-Strength Property of Coated Plain-Weave Fabrics
    Hirokazu MINAMI, Hiroshi TOYODA, YUNG Wu
    1992 Volume 41 Issue 465 Pages 913-919
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.913
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    The crack-tear-strength properties of coated plain-weave fabrics, specimen A (PTFE-coated glass fiber fabric) and specimen C (PVC-coated polyester fiber fabric), were investigated by uni/bi-axial tensile testing using the specimens which had the breadth of 20-40cm and the initial crack length of 2a=0.5-5.0cm at the center. The crack-tear-strength, Tp, to 2a=1cm, where Tp was defined as the maximum tensile stress measured during the crack propagation, decreased abruptly to less than 50% of the uniaxial tensile breaking stress. Tp in the warp of specimen A with 2a=0.5-5.0cm on the biaxial stress condition was lower than that on the uniaxial stress condition, but it was opposite for specimen C. The coating materials did not affect the value of Tp. Further more, it was discussed that either the authors' or Racah's equation could be used as the mathematical expression of 2a-Tp curve measured.
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  • Stress Corrosion Cracking of SUS316 Steel Single Crystal with Potentiostatic Slow Strain Rate Technique
    Hitoshi UCHIDA, Shozo INOUE, Toshihiro OHIDO, Keiji KOTERAZAWA
    1992 Volume 41 Issue 465 Pages 920-925
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.920
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    The stress corrosion cracking (SCC) of SUS316 steel single crystal was investigated with the potentiostatic slow strain rate technique. The smoothed specimens oriented for [001], [101], [111] and 0.50 in Schmid factor were prepared, and the susceptibility of each specimen to SCC was evaluated from the nominal stress-strain curve in a boiling 42% MgCl2 solution at 416K.
    The results indicated that the SCC under the open circuit condition occurred at the strain rate of 2.38×10-5S-1 and below, and the tensile strength and the elongation decreased with decreasing strain rate. The potential range for SCC appeared above -400mV vs. SCE which was nearly the critical potential for cracking. The uneven general corrosion occurred when the potential was shifted to more noble values. The susceptibility index to SCC defined by comparing with the nominal stress-strain curve in noncorrosive oil was almost constant in all single crystals. Thus, the resulting susceptibility was less dependent on the tensile axis orientation in comparison with the constant loading-tests. The fracture surface with coalescent steps was formed by the crack growth along ‹211› direction on {210} plane, regardless of test conditions.
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  • Effect of Ageing at 475°C and 750°C on Tensile Properties and Fracture of (α+γ) Two-Phase Stainless Steel
    Hiroyuki OGIYAMA, Tetsuro SHIRAISHI, Hitoshi TSUKUDA
    1992 Volume 41 Issue 465 Pages 926-932
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.926
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    The effects of ageing at 475°C and 750°C on tensile properties were studied using (α+γ) two-phase stainless steel having different duplex structures.
    The main results obtained are as follows;
    (1) On ageing at 475°C, 0.2% proof stress and tensile strength increased remarkably and ductility did not decrease so much for the fine grained specimens. In the coarse grained ones, however, ductility decreased remarkably with the ageing. These results are closely related to the fact that α phase deformed by slip for the fine grained specimens irrespective of the ageing whereas deformation mode changed from slip to mechanical twin with the ageing for coarse grained ones and therefore each specimen showed the different fracture mechanism.
    (2) On ageing at 750°C, 0.2% proof stress and tensile strength increased and ductility decreased remarkably for the fine grained specimens while strength and ductility did not change so much for the coarse grained ones compared with the fine grained specimens. These results are quite different from the behaviors for the case of ageing at 475°C, that is, grain refinement did not improve the ductility of specimens when aged at 750°C. The results are related to the fact that the formation of σ phase from α phase during the aging at 750°C was accelerated by the grain refinement and then the fracture process showed the initiation of cleavage cracks in σ phase followed by the coalescence of these cracks.
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  • Effect of Shot Peening on Delayed Fracture of High Strength Steel
    Yoshihiro WATANABE, Norihiko HASEGAWA, Michio INOUE
    1992 Volume 41 Issue 465 Pages 933-938
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.933
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    A study was made on the effect of shot peening on delayed fracture of high strength steel at a level of 1300MPa and 1400MPa. To investigate this effect, three types shots, having different hardness and mean diameter, were prepared to make the different residual stress distribution in the bending type specimen. Using these shots, specimens were peeved by an air type shot peening device. It was confirmed that the delayed fracture resistance of each shot peened specimen was improved compared with those of as quenched and tempered specimens due to an increase in compressive residual stress. By measuring the displacement of moment arm, it was found that this result was caused mainly by a prolonged incubation period to crack initiation, the reason of which would be that the compressive residual stress defended hydrogen entry in metal.
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  • Fabrication of Hydroxyapatite Sheet by a Sol-gel Method and Its Ion-exchange Characterictics
    Suguru SUZUKI, Hideki NAKANE, Masanari OHSHIMA, Minoru TAKAHASHI, Yasu ...
    1992 Volume 41 Issue 465 Pages 939-944
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.939
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    Fabrication of hydroxyapatite (HAp) sheets was attempted by the sol-gel method. The sol, the starting material, was prepared with 5% sodium alginate solution and sodium diphosphate. The sol sheet was dragged out 0.5-2.0mm thick on a glass plate with a chromatographic sheet maker and subjected to an ion-exchange process in the solution consisting of Ca(CH3COO)2 and CaCl2. The gel sheet, after calcium substitution, was fired at 900-1200°C for 1h. The gel sheet ion-exchanged simultaneously from both sides maintained its shape after firing but became uneven. Therefore, it was tried to produce a flat sheet on an alumina plate by a dip-coating method. The thickness of the sheet was proportional to the number of repeated runs consisting of dip-coating, ion-substituting and firing. The fired HAp can remove Pb2+ ions in a strong acidic solution of pH 3 and pH 2 containing Pb2+ ions.
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  • Evaluation of Corrosion Characteristics of Plasma-Spray Ceramic Coated Steel
    Yuji KIMURA, Takayoshi YAGASAKI, Toshio YOSHIOKA, Motoi KANAZAWA
    1992 Volume 41 Issue 465 Pages 945-950
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.945
    JOURNAL FREE ACCESS
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    To make clear the performance of plasma-sprayed ceramic coating, several investigations concerning degradation characteristics including tribological and adhesive strength are being conducted these days. In this paper, corrosion characteristics of plasma-sprayed ceramic coating, which is used for various applications as thermal barrier and antierosive coatings, were evaluated from electro-chemical view points. As a result, it was recognized that the zirconia top coat layer contained a lot of pores and cracks. The corrosion damage of plasma-sprayed ceramic coating was brought about by the anodic dissolution of under coat NiCrAlY layer at the boundary between the zirconia top coat and the under coated layer.
    Various electrochemical examinations about the corrosion characters of plasma-sprayed ceramic coating indicated the following facts. Under freely corroding conditions, plasma-sprayed ceramic coating has little contribution to improve the corrosion characteristics of matrix metals, especially in 3% NaCl aquerous solution. Therefore, for evaluating the corrosion resistance of plasma-sprayed ceramic coating, the anodic dissolution by corrosive media, which come into the boundary layer through open voids in the top coat ceramic layer, is extremely important.
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  • Measurement of Fatigue Crack Opening and Closing Points in Thin Plate Specimen and It's Difficulties
    Chobin MAKABE, Hideo KANESHIRO, Shin-ichi NISHIDA, Tateki YAFUSO
    1992 Volume 41 Issue 465 Pages 951-956
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.951
    JOURNAL FREE ACCESS
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    The measurement of fatigue crack tip opening and closing points in a machine element with complicated shape is expected to involve difficulties. In the present study, the measurement of crack opening and closing points in a center notched thin plate was carried out by the unloading elastic compliance method and the strain interference method, and the application of these methods to an actual machine equipment was discussed. The strain measurements were carried out at several positions around the notch and crack for the purpose of determining crack opening and closing points. When the bending of the specimen arises during a push-pull fatigue process, the measurement of crack opening and closing points becomes more difficult unless the proper measuring position is chosen. However, when the strain function consisting of strains measured at two diffent positions on the same longitudinal axis is used in the case of strain interference method, the crack opening point can easily be measured with sufficient accuracy.
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  • Strength Evaluation and Safety of Machine/Structure
    3. Case Examples on Strength and Safety Evaluation of Machine/Structure 3·3 Rollingstock-Axle, Fablicatde Truckframe-
    K. Toyama, S. Koe, A. Iwamura
    1992 Volume 41 Issue 465 Pages 957-962
    Published: June 15, 1992
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.41.957
    JOURNAL FREE ACCESS
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