Journal of the Society of Materials Science, Japan

Underwater Concreting Work for Large Scale Offshore Structure

Satoshi KASHIMA, Kozo HIGUCHI, Mitsushige SAKAMOTO, Ryota OKADA

1992 Volume 41 Issue 460 Pages 1-10
Published: January 15, 1992
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.41.1

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Preferential Orientation of α Phase With the Matrix of β' Single Phase in Cu-41.7%Zn Alloy

Susumu IKENO, Masaru AOKI, Kenji MATSUDA, Yasuhiro UETANI, Shizuo TADA

1992 Volume 41 Issue 460 Pages 11-16
Published: January 15, 1992
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.41.11

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The characteristic form of α phase, which always exists as a pair of plates when produced by decomposition of the matrix of β' phase, was examined by using an embossing method and SEM observation. A prominent feature of the α phase was utilized to determine the habit plane of α phase to the matrix plane. A straight line appeared at the center of the triangular α phase as one of the feature, and this center line was almost parallel to the (002) band of SEM-ECP from the β' matrix. At the (001) plane of β' matrix, there are two kinds of α phase that could be divided by the inclination angle to the (011) band of SEM-ECP, and they were separated away by an angle of about 4° each other. At the (011) plane of β' matrix, each plate of α phase pair was inclined about 7.3° from the (011) band of SEM-ECP from the β' matrix. From the results mentioned above, it is concluded that the habit plane of α phase to β' matrix exists near {5, 27, 29}_m plane of the matrix.

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Superplastic Behaviour of 5083 Aluminium Alloy Bearing 0.12wt% Zr

Hajime IWASAKI, Yasuyuki MASAKI, Kenji HIGASHI, Sinji TANIMURA, Taichi ...

1992 Volume 41 Issue 460 Pages 17-22
Published: January 15, 1992
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.41.17

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Superplastic behavior of 5083+0.12Zr alloy was investigated in the temperature range from 783 to 843K and in the strain rate range from 8×10^-5 to 3×10^-3S^-1 at constant strain-rate tensile test. Maximum elongation of 580% was obtained at 823K and at strain rate of 1×10^-4S^-1, where m value retains its initial value of 0.5 up to a large strain of 1.3 and where minimum cavitation occurs. The large elongation is due to stable deformation caused by retaining the initial m value up to large strain. The alloy showed strain hardening which is induced by dynamic grain growth. Dynamic grain growth rate increased with decreasing strain rate. Decreasing of m value with true strain may be attributed to decreasing grain boundary caused by cavitation and grain growth.

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Time Dependent Characteristics of Proposed Constitutive Equation Covering Wide Range of Strain at High Strain Rate

Hidefumi DATE

1992 Volume 41 Issue 460 Pages 23-27
Published: January 15, 1992
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.41.23

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In this paper, the time dependent characteristics of the constitutive equation proposed previously was investigated by comparing the experimental time history of strain with the numerical one. The proposed constitutive equation is a new form in which the logarithmic or the power law type is superimposed upon the Malvern type and the strain rate hardening exponent or the coefficient in both equations is a function of strain. The numerical analysis of one dimensional longitudinal impact using the constitutive equation was performed by the characteristic line method.
A long rod of lead was collided with a hardened target at various velocities up to 100m/s longitudinally and the deformation process of the specimen was recorded using an image-converter cemera in this experiment. The data in the photograph were read off by a CCD camera system containing a cursor generater. The results show that the time history of strain obtained in the numerical analysis is in good agreement with the experimental one in the region where one dimensional deformation occurred. It is apparent that the proposed constitutive equation predicts the practical material property in a wide range of strain at high strain rates.

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Relationship between Stress and Strain in Polyethylene Foam

A Consideration of Compressive Properties Based on a Simulation Model

Takamasa NAKAJIMA, Ryouske NOGAMI, Yoshiharu TERAGISHI, Toshio TAKADA

1992 Volume 41 Issue 460 Pages 28-33
Published: January 15, 1992
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.41.28

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Knowledge of the relationship between stress and strain in polyethylene foam is indispensable to design the products in which polyethylene foam is used. However, few studies have been made on this relationship.
In this paper, a simulation model was assumed with consideration of the buckling, the property of gas and so on, in order to express the relationship between stress and strain in the process of compressing. Then, compressive tests were performed to verify this model. The main results obtained are as follows.
(1) The present model could express the relationship between stress and strain as evidenced by the results of compressive tests under the condition of a constant speed.
(2) The relationship between the shape of stress-strain curve and three parameters of this model, that is young's modulus E, dispersion of buckling load α and buckling load β, became clear.
(3) The relationship between density and each parameter of E, α and β could be approximated by simple equations.
(4) This model could explain the reason why the values of parameters E, α and β are changed by the preceding loading condition.
(5) The relationship between cushioning properties and parameters became clear by the method of static evaluation.

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Evaluation of Anisotropic Extension Property of Coated Plain-weave Fabrics and the Application to Membrane Structures

Hirokazu MINAMI

1992 Volume 41 Issue 460 Pages 34-40
Published: January 15, 1992
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.41.34

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The biaxial stress-strain curves of PTFE-coated glass fiber (specimen A) and PVC-coated polyester fiber (specimen B) plain-weave fabrics were measured by maintaining the ratio of warp stress/fill stress at 1/1, 2/1 and 1/2. The extension curves, especially that of specimen A, showed peculiar high nonlinearity which was evident in the fill extension curves consisting of the parts of very small slope in the lower stress region and of steep slope in the stress region later. For the precise and practical structural analysis of membrane structure, the author presented a method of multi-step-linear approximation to the extension curves measured on many stress ratio conditions corresponding to a variety of biaxial deformation states in the real structure. The least square method was applied, and the error, which results from the approximation of elastic constants in the constitutive equation for each secant line through the extension curve, was made to be minimum in this method. By applying the method, the three-step-linear approximation was conducted on the specimens and the errors were evaluated. According to the result of the approximation, the accuracy was good for the practical application but was not so sufficient about the fill extension curve of specimen A. However, it can be generally said that the present method can be applied for the elastic structural analysis of membrane structures.

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Influences of Charging Position and Composition of SMC Sheet on Tensile Strength Properties of an SMC Panel for Automotive Structural Component

Seiichi ITSUTSUJI, Takehito FUKUDA

1992 Volume 41 Issue 460 Pages 41-47
Published: January 15, 1992
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.41.41

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Tensile strength tests of SMC panels used for an automotive structural component were conducted by changing the charging positions of SMC sheet and its compositions such as low profile additives and fillers. Three kinds of SMC sheets with different types of low profile additives and different amounts of fillers were prepared. Three of charging positions of such SMC sheet were the central part (M), the flat part (F) and the side of ribs and bosses (R) of a metal mold. Test specimens were cut out from these nine kinds of SMC panels. The cutting directions of tensile specimens were perpendicular (90deg. directional specimens) and parallel (0deg. directional specimens) to the rolling up direction of SMC sheet. Statistical analysis of data obtained from tensile tests was carried out based on the concept of two-parameter Weibull distribution. Analysis results are summarized as follows;
(1) For SMC panels molded at charging positions F and R, strength of 0deg. directional specimen is from 2 to 3 times as high as that of 90deg. directional specimen. On the other hand, for SMC panels molded at M, there is little difference between them.
(2) In case of low profile additive of poly-vinyl acetate system, the flow pattern of fibers is inclined not to be uniform and the fracture strain is less than that in the case of styrene butadiene system.
(3) The tensile strengths of SMC panels tend to become lower as the amount of filler of CaCO₃ increased.

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Anisotropy of Fatigue Deformation Behavior of Titanium in Vacuum and in Air

Mikio SUGANO, Noriyoshi UMETSU, Tadaaki SATAKE

1992 Volume 41 Issue 460 Pages 48-54
Published: January 15, 1992
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.41.48

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To study the fatigue behavior of the cold-rolled titanium plate (KS40) with the texture of the major orientation of (0001) [1010]±30°, the plane bending fatigue tests have been carried out on the specimens (0.3mm thick) cut out parallel (LT) and perpendicular (TL) to the rolling direction, respectively. The tests were conducted in vacuum (1.33×10^-3Pa) and in air at the resonant frequency of about 600Hz for the second-order mode of oscillation. Comparison of the TL with the LT specimens showed that in air the anisotropy was discernible in S-N curves and fatigue crack growth behavior, but hardly in vacuum. In air, the TL specimen had fatigue strength and fatigue crack growth properties greater than the LT specimen and the fracture surfaces appeared more brittle in the TL specimen. It seemed that the character of fatigue behavior in air could be connected with the crystallographic conditions for deformation: the ease of slipping or twinning shear. In vacuum, the specimens raised temperature in themselves up to 45K above room temperature, when cyclically stressed at σ=±201MPa, and fractured in ductile modes. Common microstructure around fatigue cracks was characterized by cell structure both in vacuum and in air, although numerous twins were contained in the specimen prior to fatigue tests. The cells were developed more in vacuum than in air. The results obtained were discussed in connection with the plastic deformability enhanced by internal heating during fatigue testing from the crystallographic points of view.

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Effect of Grain Boundary on Fatigue Life of Aluminum Bicrystals

Ken ATAGI, Fukuji INOKO

1992 Volume 41 Issue 460 Pages 55-60
Published: January 15, 1992
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.41.55

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In order to examine the effect of grain boundary on fatigue life, aluminum bicrystals with a longitudinal boundary were prepared by the Bridgman method. They were tested by a bending fatigue testing machine under the constant strain amplitude of 0.13% and cyclic frequence of 30.4Hz. The results obtained were as follows:
(1) The fatigue life decreased with increasing the saturation moment, M_s, at N=10³.
(2) The existance of grain boundaries in aluminum bicrystals possibly shortens the fatigue life.

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Influences of Defects upon the Fatigue Strength of Si₃N₄ Ceramics

Hiroshi HOHJO, Katsushi SARUKI, Akira YAMADA

1992 Volume 41 Issue 460 Pages 61-67
Published: January 15, 1992
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.41.61

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Microstructure of engineering ceramics, especially the distribution of defects and the density, sometimes varies with the lot of manufacture. For this reason, it is important to investigate the influences of the microstructure upon the mechanical properties.
In this study, the rotating bending fatigue tests were carried out on two lots of Si₃N₄ ceramics, and the influences of the defects and density upon the fatigue strength were investigated. Bulk densities of lots A and B were 3.02g/cm³ and 3.16g/cm³, respectively. Average static bending strength of lot B was about 20 percent higher than that of lot A due to the differences in defects distribution and fracture toughness. However, the two lots scarcely differed in rotating bending fatigue strength. This is considered to be because the fatigue strength largely depends on the size and kind of defects.
Fatigue strength was predicted on the basis of a fatigue datum in the case when the fracture origin was the largest pore defect. Crack propagation rate was assumed to be in proportion to the power of the stress intensity factor. Consequently, when the fracture origin was a pore defect with inclusion or a micropore cluster, the fatigue strength was higher than the predicted value, in most cases. Therefore, the fatigue life prediction based on pore defects leads to reliable estimation.

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Crack Initiation Life of 304 Stainless Steel Notched Specimen at Elevated Temperature

Hiroyuki TAKAHASHI, Takashi KAWAKAMI, Tetsuro UNO, Kenichi TAKAKURA, K ...

1992 Volume 41 Issue 460 Pages 68-73
Published: January 15, 1992
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.41.68

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In order to rationalize the creep-fatigue damage tolerant design of a fast breeder reactor (FBR), it is very important to determine the relationship between the creep-fatigue damage of components having stress concentration and the creep-fatigue life obtained by smooth specimens.
In the present study, creep-fatigue tests were carried out on 304 stainless steel notched specimens, simulating the case of FBR component. The bending load was applied at 600°C under a condition of local strain control. During the tests, the damage progress in the notch bottom, from crack initiation through propagation, was continuously recorded on microscope photographs. The stress-strain behavior obtained by inelastic analysis was compared with the test results. The creep-fatigue damage value for the crack initiation was calculated by using the linear damage rule. The main conclusions are as follows.
(1) Micro-cracks initiated in an early stage. A sufficient life, however, remained until macro crack initiation.
(2) As the creep influence became significant, damage occurred over an extensive region.
(3) The stress-strain behavior in actual components was estimated accurately with inelastic analysis, based on the constitutive equations derived from smooth specimen tests.
(4) Estimation according to the linear damage rule with creep and fatigue failure data obtained by smooth specimens shows that it is possible to predict conservatively the macro crack initiation life of stress-strain concentration parts.

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Correlation between Crack Propagation Behavior and Variation of Cumulative Fatigue Damage under the Two-Step Stress Loading of 70/30 Brass

Kenji MATSUDA, Yukitaka MURAKAMI, Shigeru SHINOZAKI

1992 Volume 41 Issue 460 Pages 74-79
Published: January 15, 1992
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.41.74

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The correlation between crack propagation behavior and variation of cumulative fatigue damage under the multiple repeated two-step stress loading of 70/30 brass was investigated. The experimental results were compared with those of a medium carbon steel (0.46%C) which were obtained in the previous study.
Relationship between crack length and cycle ratio (Σ(n_H/N_H)+(n_L/N_L)) under two-step stress loading for 70/30 brass was similar to that under constant amplitude test of σ=σ_H, that is, almost independent of various combinations and frequency of the overstress σ_H and understress σ_L. The values of cumulative fatigue damage D based on the Modified Miner Rule for 70/30 brass were approximately equal to 1.0 regardless of the combination of σ_H and σ_L contrary to the case of 0.46%C steel in which D had the values much smaller than 1.0 for a certain combination of σ_H and σ_L. Possible reasons such as the crack initiation behavior from the crack tip and the existence of strain aging in carbon steels for different behaviors between 70/30 brass and a medium carbon steel are suggested.

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Resistance to Fatigue Crack Propagating along Weld Interface of Carbon Steel/Carbon Steel Friction Welded Butt Joint

Hideaki NAKAYAMA, Yoshio OH-UE, Kohzo OKITA, Masatoshi ARITOSHI

1992 Volume 41 Issue 460 Pages 80-86
Published: January 15, 1992
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.41.80

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In order to evaluate the resistance to growth of fatigue cracks propagating along the weld interface of friction welded butt joints composed of carbon steel/carbon steel, a series of fatigue crack growth tests were carried out on S25C/S25C and S45C/S45C joints under three different cyclic load conditions. To investigate the effect of residual stress distribution in the specimen introduced in friction welding process on the crack growth behavior, two types of CCT plate specimens with a thickness of 2mm were prepared for respective carbon steel joints; one was the specimen as welded and another was the residual stress relief treated specimen. And the results of these joint specimens were discussed in comparison with those of the annealed CCT base metal plate specimens. First of all, whole crack growth behavior was investigated under increasing ΔK condition, and then the dependence of crack growth rate on the weld interface location was studied under a constant ΔK condition, and finally the ductility of the weld interface was evaluated indirectly through the observation of crack growth retardation behavior induced by the application of single static over-load during crack growth under constant ΔK. The results indicate that the residual stress does not play an important role on the fatigue crack growth of the joints, and metallurgical feature of the weld interface governs the fatigue crack growth behavior of the joints. And, the decrease in crack growth rate of the joint specimens by the application of the over-load is less than that of respective base metals, which indicates that the ductility of the weld interface of both joints is less than that of respective base metals.

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Fatigue Crack Growth Characteristics of STS42 Steel at Elevated Temperature

Hideo KOBAYASHI, Haruo NAKAMURA, Eiichi KODAMA

1992 Volume 41 Issue 460 Pages 87-93
Published: January 15, 1992
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.41.87

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Fatigue crack growth characteristics and the fatigue crack closure in a STS42 steel for nuclear piping were investigated at temperatures around 288°C (from room temperature up to 400°C). Within the temperature range tested, the crack growth rate, da/dN, was well described in terms of the effective stress intensity factor range. An apparent difference in da/dN-ΔK relation is due to the crack closure. At 100°C, a thin stable oxide film (Fe₃O₄) on the fracture surfaces works as wear protection and the production of fretting oxide debris (Fe₂O₃) is prevented. As a result, da/dN at 100°C is faster than those at room temperature and at 288°C due to the lack of crack closure.
The resistance to oxidation at 288°C for STS42 was inferior to those for A508-3 and 304. However, such characteristic in STS42 promotes an occurrence of crack closure which has a favorable effect on fatigue crack growth resistance.

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Effect of Stress Wave Form on Crack Growth Initiation Behavior of Delayed Failure under Cyclic Mixed Mode I and II Loading Conditions

Nobuki HIRUTA, Mitsuo KIDO

1992 Volume 41 Issue 460 Pages 94-100
Published: January 15, 1992
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.41.94

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The crack growth initiation behavior in delayed failure under superposed cyclic mode II stress of various stress wave forms was investigated on the precracked specimens of Ni-Cr-Mo steel quenched and tempered at 673K. When the range of mode II cyclic stress intensity factor ΔK_II was superposed on the static stress intensity factor K_I, the crack growth initiation time t_g decreased with an increase in ΔK_II, the degree of which increased with an increase in applied stress increasing period at a constant frequency; i.e. t_g decreased most under cyclic load with positive saw tooth wave, followed by those with negative saw tooth wave and trapezoid. The intergranular fracture ratio ψ of crack growth initiation surface was affected little by stress wave forms of ΔK_II. The reason why the crack growth initiation time t_g decreased when the stress wave form of mode II had a long stress increasing period seems to be that the corrosive reaction is activated during the stress increasing period, since the protective film in the vicinity of crack tip is destroyed mechanically by cyclic stress.

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Analysis of Thermal Stability of AAS Resin in Injection Molding

Hisashi KOHKAME, Hideki ASANO, Masao GOTO, Yasushi MIYANO

1992 Volume 41 Issue 460 Pages 101-105
Published: January 15, 1992
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.41.101

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Acrylonitrile-acrylic elastomer-styrene terpolymer (AAS resin) was developed to improve weatherability of acrylonitrile-butadiene-styrene terpolymer (ABS resin). To compare thermal stability of both resins, test pieces of AAS and ABS resins were injection molded at various temperatures and the Izod impact value of the resulting moldings was measured. A study was then made to find the relationship between this value and deterioration of the resins. AAS resin was molded at temperatures from 180°C to 280°C. The impact value of the resulting moldings was almost constant for temperatures up to 260°C, with the first major decrease occuring at 280°C. In contrast, the impact value of conventional ABS resin moldings constantly decreased as the molding temperature elevated. To explain this phenomenon in the both resins, two types of test program steps were undertaken:
(1) The cause of the change in characteristics of the AAS resin was first determined by: obtaning its stress-strain curve in a high-speed flexural strength test; measuring its infrared absorption spectrum; and determining its flow properties with a constant-pressure extrusion type rheometer;
(2) The distribution of elastomer in the resin was observed with an electron microscope. It was found that the decrease of impact values of both resins at high temperatures is caused by deterioration of the elastomer. Also, it was found that the different relationships between the impact value and molding temperatures for AAS and ABS resins are due to the difference between the rates of thermal degradation of the acrylic elastomer and butadiene elastomer.

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Evaluation of Fracture Toughness by Chevron V-Notch Method

Yoshihisa SAKAIDA, Hideo AWAJI, Hiromichi TAMIYA, Hiroshi NAKAO

1992 Volume 41 Issue 460 Pages 106-111
Published: January 15, 1992
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.41.106

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The chevron notch (CN) method has an advantage that the crack length need not be measured to estimate fracture toughness. The crack, however, should grow stably until the critical length to get the valid fracture toughness value, which was hardly attained by a conventional CN method. Therefore, a chevron V-notch (CVN) method has been developed to assure the stable crack growth by using a sharp V-notch technique. The sharp V-notch was machined by a V-shaped diamond cutting wheel.
The results obtained are:
(1) A stable crack extension was observed throughout until unstable crack extension occurs.
(2) The fracture toughness values evaluated by the CVN technique coincided very well with those by the single edge V-notched beam (SEVNB) method and those by the single edge precracked beam (SEPB) method.
(3) The fracture toughness evaluated by the CVN technique showed quite narrow scatter, whereas those by the conventional CN method with the notch width of 0.1mm showed wide scatter.

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Evaluation of Creep Rupture Properties with Miniature Test Specimen

Keiji SONOYA, Masaki KITAGAWA

1992 Volume 41 Issue 460 Pages 112-118
Published: January 15, 1992
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.41.112

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Evaluation of service reliability of components, particularly the remaining service lifetime of materials, has become a very important matter for thermal power stations and other plants. The remaining lifetime is usually assessed with a fair precision from aggravation of mechanical properties, especially that of creep characteristics. One difficulty here is that, if the precision of prediction is to be improved over what is available with today's in-situ nondestructive methods, one needs to take samples directly from operating machines, whereby one has to be satisfied with a small quantity of samples. This calls for establishment of a trustworthy method for evaluating creep rupture characteristics with a small number of small-size specimens.
The following observations and conclusions were made in the present study.
(1) The miniature specimen creep tester, developed here with a testing chamber maintained airtight with a pair of O-rings, performed quite well, in which the combined effect of internal Ar pressure and O-rings could be safely ignored.
(2) In Ar atmosphere to forestall oxidation, the rupture time obtained with the 2mm diameter miniature test specimens agreed quite well with that obtained with the 8mm diameter conventional test specimens.
(3) The effect of oxidation to degrade the rupture time became manifest above 600°C.
(4) The major cause of this degradation is an increase in true stress arising from the loss of material due to oxidation.

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Evaluations of Polarization and Impedance Behavior of Bare Surface by Scratching Electrode Method

Kenji YOSHIMI, Mitsuo KIDO

1992 Volume 41 Issue 460 Pages 119-125
Published: January 15, 1992
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.41.119

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Polarization and Impedance behavior for a scratched specimen of SUS304 were measured in sulfuric acid solution (pH 1.2). The results obtained are as follows.
(1) The size of impedance diagram for the scratched specimen in the vicinity of Flade potential became smaller than that for the non-scratched specimen, but the size for the scratched specimen in passive state became larger than that for the non-scratched specimen.
(2) The rate of change in impedance |Z| with time differed depending on chemical composition of specimen, but it did not change before and after scratching if the same material was used.
(3) It is considered that the change of anodic current density due to scratching represented the non-steady state reaction process immediately after scratching and the change of impedance represented the steady-state reaction process after that.
(4) A computer simulation in the vicinity of Flade potential using an equivalent electric circuit suggested that the charge transfer reaction, disslution reaction and film-formation reaction were markedly activated due to scratching.

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Present State and Prospects of Aggregates for Concrete

5. Arificial Aggregates and Their Use

H. Kawakami

1992 Volume 41 Issue 460 Pages 126-131
Published: January 15, 1992
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.41.126

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