Journal of the Society of Materials Science, Japan

Characteristic of Ceramics

Masanaga KUNUGI

1979 Volume 28 Issue 311 Pages 683-688
Published: August 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.683

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Stress Concentration due to Spheroidal Inclusion

Mamoru SHIBATA, Kanji ONO, Tadahisa NAKAMURA

1979 Volume 28 Issue 311 Pages 689-698
Published: August 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.689

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Heat of Sorption Estimated from Temperature Dependence of Relative Vapor Pressure of Wood

Hajime OKAMOTO, Ken'ichi ITOH

1979 Volume 28 Issue 311 Pages 699-704
Published: August 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.699

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Two sets of widely refered data on the equilibrium moisture content of wood, one by U.S.D.A., Forest Products Laboratory and the other by R. Keylwerth, were examined for the temperature dependency by applying the Clapeyron-Clausius equation. The apparent differential heat of sorption and the related quantities were compared with the literature values obtained by calorimetry. The difference was found to be too great to be neglected for approximation. The effect of sorption hysteresis upon the apparent differential heat was also estimated from the data in literature, and the result was comparable in its extent to the above mentioned discrepancy. On the contrary, the data of Stamm and Loughborough obtained by their “oscillating desorption” method were proved to be in accordance with the calorimetric data.

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Properties of Composite Plywood with Particleboard Core Produced by Vertical Pressing Technique

Ryozo HAMADA, Etuko NAGAO

1979 Volume 28 Issue 311 Pages 705-710
Published: August 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.705

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In order to obtain informations about utilization of particleboard as a substitute for the core of plywood, an oriented particleboard was prepared by a vertical pressing method similar to that used in making extrusion particleboard and then a composite plywood was made with both faces of veneer and a core of the oriented particleboard. The effects of preparation conditions such as the board density, kinds of binder, resin content and orientation of particles on the properties of particleboard were investigated. The physical properties and durability of the composite plywoods having variously reconstituted particleboard cores were examined. From the experimental results it was proved that the particleboard produced by the vertical pressing technique had excellent strength and dimensional stability in the direction parallel to the grain of particles, and the properties of the composite plywood made of a core of oriented particleboard and faces of veneer were comparable to those of plywood.

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Treeing Deterioration at the Surface of Electrical Insulating Materials

Tadao IKEJIRI

1979 Volume 28 Issue 311 Pages 711-717
Published: August 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.711

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Is this paper, the fundamental properties of trees at the surface of synthetic resins during application of intermittent high voltage at commercial frequency were investigated. The growth of trees at the surface of various insulating materials was also discussed from a view point of utilizing it as a way to evaluate tracking resistance of materials.
The growth of trees occured during the voltage application was large in PVC resin, medium in Polyester glass etc. and small in Silicone glass. In every resin, the growth of trees increased abruptly at the initial period of voltage application, and then slowed down with time.
The growth of trees also increased with applied voltage in a manner of a concave curve rising upward, for all resins. The same trend was observed when the electrode gap length was increased.
When a high frequency voltage was superimposed, the growth of trees showed a tendency of increasing with superimposed frequency and the effect of accelerating deterioration was observed. However, this effect varied more or less with the kind of resin used.
The variation in growth of trees agreed fairly well with the results obtained by the conventional tracking resistance tests.

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Mechanism of Deformation of Particulate Materials as Markov Process

Ryosuke KITAMURA

1979 Volume 28 Issue 311 Pages 718-724
Published: August 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.718

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In this paper, the micrometric approach which can establish the constitutive relations of particulate materials such as sands is described. In this approach the motion of particles in particulate materials is assumed to be a Markov Process which is one of the well-known stochastic processes. This assumption is reasonable because the irregularities of the particles in both size and shape, and the complicated fabric of particulate materials are considered to prohibit the deterministic approach to the motion of individual particles in the particulate materials.
First, the Markov Process is explained briefly and the basic equation of the Markov Process is derived. Secondly, the Markov Process is applied to the mechanical behaviors of particulate materials, and the concepts of potential berrier and potential slip plane are introduced in order to determine the coefficients in the basic equation of the Markov Process. Thirdly, the strain of particulate materials is derived by averaging the motion of particles. Finally, the stress-strain relationship obtained from the micrometric approach is compared with the result of the drained triaxial compression test on Toyoura Sand. It is shown that this approach is very valuable in order to analyse the various mechanical behaviors of particulate materials comprehensively.

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A Study on Failure of Partially Thinned Pipes by External Pressure

Toshinobu SHIBATA, Hiroshi NAKAI, Kiyoshi FUJINAMI

1979 Volume 28 Issue 311 Pages 725-730
Published: August 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.725

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It is important to prevent the buckling of thin pipes caused by an external pressure in the heat-exchanger system of a pressurized water reactor. The design code in ASME Sec. III NB considers this point. However, the thickness of pipes is partially thinned down by steam-liquid flow in service, and in design step no consideration is being paid to such a partially thinned down pipe, though much attention should be paid on this point.
In this paper, the pressure at failure of a partially thinned pipe under an external pressure was studied. The experimental results show that the failure occurs at unexpectedly small pressure, if the thinned part has some expansion in area, and that the pressure at failure does not follow with the buckling equation given by elastic theory for thin cylinders.

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Analysis of Fracture Surface in Stress Corrosion Cracking of Austenitic Stainless Steel

Saburou KUWANO, Takeo OKI

1979 Volume 28 Issue 311 Pages 731-737
Published: August 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.731

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It was reported in the previous paper that the crack morphology of the stress corrosion cracking of 18-8 austenitic stainless steel in a boiling 42% magnesium chloride solution changed with applied stress level.
In this paper it was intended to attest that this transformation depends upon the stress intensity factor at the crack tip, and to inspect whether the crack propagation proceeds along a particular crystallographic orientation or not.
The ratio of intergranular cracking to transgranular one was measured on the single notched specimens fractured under various initial loads such as 300, 400 and 600kg.
The relation between the crack morphology and the stress intensity factor at the crack tip was also obtained, and the dependency of the crack propagation upon the crystallographic orientation was inspected by forming etch pits on the cracked surface of the specimen fractured under the initial load of 300kg.
The following conclusions were deduced from these experiments: The crack morphology transformed remarkably from transgranular cracking to intergranular cracking with increasing applied stress or the stress at the crack tip under the same applied stress, and the degree of transformation was highly connected with the stress intensity factor at the crack tip.
The transgranular cracking in the region of low stress was likely to be formed by crack growth along <110> direction on {110} planes, and the facets formed on this crack surface were likely associated with this dependency of crack propagation upon crystallographic orientation. These results indicate that this crack morphology was formed by the anodic dissolution of sessile dislocations and tearing by stress.

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Dynamic Fracture Toughness of Fiber Reinforced Polycarbonates (Temperature Effect)

Megumu SUZUKI, Masaharu IWAMOTO, Toshiyuki KAJIYA

1979 Volume 28 Issue 311 Pages 738-744
Published: August 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.738

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In order to study the dynamic fracture toughness of composite materials from a viewpoint of fracture mechanics, the dynamic fracture toughness, the absorbed energy and the velocity of crack propagation at initiation of crack growth were determined on glass fiber reinforced polycarbonate as a function of temperature by using a Charpy tester loaded with various instruments.
The results obtained are as follows: The dynamic fracture toughness and the absorbed energy for glass fiber reinforced polycarbonate increase with an increase in temperature. The increasing rate for the specimen of 30wt% fiber content, in which the mechanical and thermal properties are controlled by those of glass fiber, is smaller than that for the specimen of 10wt% fiber content, in which they are controlled mainly by those of matrix. The velocity of crack propagation decreases with an increase in temperature. The decreasing rate for the specimen of 30wt% fiber content is smaller than that for the specimen of 10wt% fiber content. By introducing a modified factor, φ, which represents the dependence of relative crack length, a/W, on absorbed energy, it is possible to estimate the dynamic fracture toughness from the measured energy. It can be found that the estimate values of dynamic fracture toughness are in good agreement with those calculated by another method.

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Influence of Surface Layer on Corrosion Fatigue Strength of Aluminum Alloy Prestrained by Pulling

Kazuaki SHIOZAWA, Sotomi ISHIHARA, Kazyu MIYAO

1979 Volume 28 Issue 311 Pages 745-751
Published: August 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.745

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In order to investigate the influence of tensile prestrain on the corrosion fatigue strength of metal, high cycle fatigue tests were carried out on aluminum alloy (2017) sheet specimens under completely reversed plane bending stress in laboratory air and in salt water (3.0% NaCl). The specimens were prestrained and the surface layer was removed by an electrochemical process. The results of these specimens were compared with those without surface removal. It is evident that the corrosion fatigue life of the specimen without surface layer is independent of the degree of tensile prestrain and is longer than that of the specimen with surface layer. In corrosion fatigue, the presence of surface layer is expected to decrease fatigue fracture resistance because the specimen becomes more sensitive to environment with increasing dislocation density and furthermore the rate of crack propagation through the surface is high in the presence of surface layer. On the other hand, the fatigue life in air is increased by the presence of surface layer because the work-hardening appears on the surface layer and in the inner part of the specimen by tensile prestrain.

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Resistance of Cavitation Erosion on Hard Metal

Tsunenori OKADA, Norihide MAEKAWA

1979 Volume 28 Issue 311 Pages 752-758
Published: August 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.752

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To study erosion resistance of WC-Co alloy in various environments, cavitation erosion tests were carried out in ion-exchanged water, HNO₃ solution, HCl solution, NaOH solution and salt solution. The test results were compared with those of various steels and SUS 304 stainless steel in the same testing conditions.
In ion-exchanged water, the erosion resistance of WC-Co alloy was superior to that of bulk materials. The erosion damage of WC-Co alloy increased slightly with increasing cavitation intensity. Therefore, WC-Co alloy shows an excellent erosion resistance under severe cavitation conditions in comparison with other materials. In many cases, the weight loss due to erosion damage increased with the corrosion of cobalt binder phase. Especially, the weight loss of WC-Co alloy was larger than that of SUS 304 stainless steel in HNO₃ solution as well as in 10% NaOH solution.
It was also pointed out that the weight loss of WC-Co alloy may increase considerably in such liquid containing a small amount of corrosive substance as water for industrial use.

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Brittle Fracture of Notched Ductile Polymers

Ikuo NARISAWA, Masaru ISHIKAWA, Hiroyuki OGAWA, Takuo SATO

1979 Volume 28 Issue 311 Pages 759-764
Published: August 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.759

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To study brittle fracture of ductile polymers, tensile tests were conducted on cylindrical bars of polycarbonate, poly (vinyl chloride) and polyethylene with a circular round notch. The notchless specimens of these polymers fractured in a ductile manner after necking, but when the plastic constraint due to local yielding at the notch root became above a critical value they showed brittle fracture. Morphological observations revealed that the fracture origins were a microvoid for polycarbonate and poly (vinyl chloride) and a number of microcracks for polyethylene. They were considered to be nucleated by a hydrostatic stress component caused by plastic constraint ahead of the fully developed plastic deformation zone at the notch section.

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Fatigue of Non-Shrinkage Mortar

Shinzo NISHIBAYASHI, Kenji SAKATA, Shoichi INOUE, Kazuo HORIGUCHI

1979 Volume 28 Issue 311 Pages 765-770
Published: August 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.765

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Non-shrinkage mortar is being used effectively to fix shoes of bridges and base plates of machines. With the recent sharp rise in traffic volume, occasions on which non-shrinkage mortars are subjected to repeated loading are increasing more and more.
In this study, fatigue tests of six kinds of non-shrinkage mortar and plain mortar in compression were performed. Since the values of fatigue life of mortar and concrete are known to scatter widely, the fatigue test results were evaluated statistically.
The results suggest that the fatigue life of non-shrinkage mortar at each stress level follows a Weibull distribution or logarithmic normal distribution. No fatigue limit seems to exist for non-shrinkage mortar. However, the fatigue strengths of plain and non-shrinkage mortar, except B mortar, at 2 millions cycles can be estimated at about 60 percent of ultimate static strengths.

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Experimental Study on Consolidation Properties of Peat

Koichi AKAI, Yuzo OHNISHI, Ikuo YASUKAWA

1979 Volume 28 Issue 311 Pages 771-777
Published: August 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.771

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Structures such as a road constructed on peat continue to settle in many years and often produce serious differential settlements.
The mechanical properties of peat have been studied by many researchers, and the secondary compression is known to be predominant in the settlement. The prediction of settlement at the field based on the Terzaghi's consolidation theory has not been successful yet in many cases for peat.
This paper describes an experimental study to find out a more accurate method for predicting the field settlement. The results show that the consolidation settlement should be interpreted by strain, and the strain increase at the field seems proportional to the value determined in the laboratory by adopting the square law of the depth of the soil layer. Also the long-term settlement appears to be estimated from the laboratory test results by using the concept of Bjerrum.

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Cohesion of Powder Particles with Water

Rheological Property of Powder-Water-Oil System

Misao NISHINO, Masafumi ARAKAWA, Koji YAMATO

1979 Volume 28 Issue 311 Pages 778-783
Published: August 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.778

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In order to investigate the mechanism of cohesion of powder particles with water, rheological properties were examined for the system composed of powder and oil. The samples used here were spherical glass powders of three different particle sizes (19-77μ) and spherical copper powder (126μ). They were chosen as typical materials wettable with water (glass) and not so much (copper). The pastes with various fractions of powder and water in castor oil were prepared and the extruder was used to measure the stress under which the paste could pass through the nozzle.
It was found that only for the systems containing water the yield value exsisted in the apparent consistency curve. This yield value was considered to arise from the cohesive force of water bridge between particles. From the comparison of various models of cohesion of particles, it was possible to interpret the change in apparent yield value with water amount by the aggregate size and its porosity which depended on the wettability of particles.

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Characteristics of Wood

3. Wood in Relations to Moisture

M. Fukuyama

1979 Volume 28 Issue 311 Pages 784-790
Published: August 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.784

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