Journal of the Society of Materials Science, Japan

Observation and Evaluation of Microcrack Propagation in Granite Fractured by Uniaxial Compression Test Using Fluorescent Resins

Hiromu KUSUDA, Takashi NISHIYAMA, Toshiaki SAITO

1995 Volume 44 Issue 502 Pages 851-855
Published: July 15, 1995
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.44.851

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Uniaxial compression test is a useful method of determining the mechanism of rock failure. However, the direct observation of microcracks during the propagation of stress-induced cracks is difficult, since it is usually difficult to distinguish these microcracks from those by other sources during microscopic examination. In this study, the microcracks were visualized using a new fluorescent approach combined with image processing, and then the propagation of stress-induced microcracks was analyzed. The following results were obtained:
(1) Many hidden microcracks which were not detected under natural light, were visualized clearly via ultraviolet light. Most hidden microcracks were composed of intercrystalline cracks.
(2) Actual microcracks in the specimens can be represented realistically through several stages of image processing, such as Laplacian operator (matrix size=9×9) and line detection operator. After this operation, the quantitative analysis was performed.
(3) Microcracks found in the damaged specimens can be divided into three categories; microcracks parallel to the axial stress, microcracks normal to the axial stress, and microcracks inclined to the axial stress, based on the microcrack direction measured on image analysis. As rock failure proceeded, the microcrack length in all directions decreased gradually. At the ultimate stage of rock failure, the microcracks parallel to the axial stress increased rapidly, while those normal or inclined to the compressive axis showed no remarkable change. The occurrence of microcracks demonstrated by image analysis agreed with the P-wave velocity determined by the usual method. It was concluded that the reduction of P-wave velocity is mainly caused by an increase in microcracks parallel and inclined to the axial stress observed under microscopy using fluorescent resins.

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Deformation Characteristics of Sedimentary Soft Rock Evaluated by Field and Laboratory Tests and Full-Scale Behaviour

Kenzo OCHI, Tatsuya TSUBOUCHI, Fumio TATSUOKA

1995 Volume 44 Issue 502 Pages 856-861
Published: July 15, 1995
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.44.856

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A 50m deep shaft, an adit and a tunnel were excavated for research purpose in a sedimentary soft rock deposit (mudstone). The stiffness of the mudstone was back-calculated from the field data as a function of strain, which was compared with that obtained from the field and laboratory stress strain tests. The Young's modulus values were very similar to each other when the strain level-dependency of stiffness (or shear stress-dependency) without incorporating the effect of discontinuity evaluated by the triaxial compression tests is considered.

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The Salinization and Slaking of Egyptian Mokattam Limestone

Chikaosa TANIMOTO, Kiyoshi KISHIDA, Eiichi ONUMA, Kunio MORI

1995 Volume 44 Issue 502 Pages 862-868
Published: July 15, 1995
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.44.862

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The Great Sphinx-Giza, Egypt was carved out of Middle Eocene limestone formations. The upper part of the statue, including the neck and the head, consists of soft and marly formations (named Maadi Formation). They are highly porous and cavernous showing the evidence of having been greatly affected by water erosion. At present, the Great Sphinx as one of the most important World Heritages is being seriously subjected to aggressive deterioration of limestone members.
Since it was not possible to employ any specimen sampled from the immediate site of the Sphinx, it was tried to investigate the process of deterioration of marly limestone in terms of Mokkatam Limestone (called Pyramid Stone) which is considered to be a little older than Maadi Formation. In the present study the process of recrystallization of salt substance on limestone surface and the transportation of salt and water through micro-pores were observed for the period of three months. The electron microscopic scanning was used to illustrate the pore-size, pore distribution and recrystallization of salt. The same test as described in this paper is recommended to be applied to the Maadi Formation for the feasibility study on the preservation of the Great Sphinx.

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Heterogeneous Permeability Profile and Localized Flow in Fractured Rocks

Michito SHIMO

1995 Volume 44 Issue 502 Pages 869-873
Published: July 15, 1995
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.44.869

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This paper describes a relationship between heterogeneous permeability profile and the geometry of localized flow paths based on a laboratory experiment. A 30cm cube of chert containing multiple sets of natural fractures is used for the study. Each of the six faces of the block is divided into 25 hydraulically isolated subpanels, i.e. 150 subpanels in total, which are connected to a separate flow line for control or monitoring. The pressure and flow responses under different boundary conditions are inverted to provide information on the spatial variation of hydraulic conductivity. It has been shown that, because of the wide variation in permeability, the limited number of high permeability zones are creating localized flow paths which controll the overall flow characteristics in a fractured chert block.

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Improvement in Accuracy of Seismic Traveltime Tomography by Adding a Priori Information as Constraints on Velocity Reconstruction

Toshiki WATANABE, Kenji FUJIMOTO, Koichi SASSA

1995 Volume 44 Issue 502 Pages 874-879
Published: July 15, 1995
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.44.874

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A constrained velocity reconstruction method was developed by use of a priori information to improve the accuracy of seismic traveltime tomography. Constraints are required to reduce the reconstruction error caused by the non-uniqueness of nonlinear inverse problems. In this method, the lower and the upper limits of the velocity (slowness) values are given to each cell to constrain the velocity (slowness) of the cells. These values are estimated by use of a priori information such as the results of other geophysical testings and the geological knowledge of the site. The allowable range of the velocity limitation is to be varied according to the reliability of the estimation. At first, slowness of each cell is assigned by using a usual inversion technique. If the slowness of some cells violates the given constraints, the slowness of such cells is fixed to the boundary value of the limitation. The contribution of these cells to ray-paths is removed. Then the traveltime or the traveltime residual is redistributed to the rest of cells. This process is to be repeated until the slowness of all cells satisfies the constraints. It is quite easy to implement this method of constraints for any types of inversion technique. The result of numerical simulations shows that both the time residual and the reconstruction error are considerably reduced by applying constraints on velocity reconstruction. This method is quite practical for the application to field data, because one can easily take geophysical and geological knowledge into tomography analysis.

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Application of Neural Network to Processing of Seismic Reflection Data

Yuzuru ASHIDA

1995 Volume 44 Issue 502 Pages 880-884
Published: July 15, 1995
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.44.880

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The present paper proposes an algorithm for data processing of reflection seismic data by use of a neural network. The algorithm of neural network was applied to the reading of the first break, the recognition of waveform in seismic trace and the automatic picking of the result of the constant velocity scan among various data processing techniques. A layered network with training by the error back propagation algorithm was used.
As a result of model studies, it was clarified that the proposed algorithm performed the first break reading, the waveform detection and the automatic picking of velocity with good accuracy.

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Application of Acoustic Emission Technique for Estimation of Initial Stress

Koji HATA, Kazutoshi MICHIHIRO, Hisaya YOSHIOKA, Kozo SUGIHARA

1995 Volume 44 Issue 502 Pages 885-890
Published: July 15, 1995
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.44.885

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A Large scale underground cavern, such as an underground power station, can be designed and executed rationally, if the initial stress condition of the site is known. Authors have carried out fundamental studies on the detection of initial stress using Acoustic Emission technique (Kaiser effect) by which the stress history of a rock mass can be estimated. In this paper, the characteristics of Kaiser effect on rock material have been investigated and the two or three dimentional principal stress condition has been estimated. It has been found that (1) the stress determined by the Kaiser effect is not always identical to the maximum stress of rock; (2) the Kaiser effect is a time-dependent phenomenon; (3) the initial stress estimated by AE method is not always equal to the initial stress estimated by the overcoring method in some field measurements.

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Laser Strain/Displacement Measurements for Fracture Mechanics Research

Keiji OGURA, Izuru NISHIKAWA

1995 Volume 44 Issue 502 Pages 891-898
Published: July 15, 1995
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.44.891

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Preparation and Some Properties of Dy-Containing β-Ca₃(PO₄)₂ Machinable Ceramics

Yasuo HIKICHI, Kazuhiro YASUDA, Ken-ichi MIYAZAWA, Kazuaki HANDA, Tosh ...

1995 Volume 44 Issue 502 Pages 899-904
Published: July 15, 1995
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.44.899

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The mixed powders of β-Ca₃(PO₄)₂ (TCP) and DyPO₄ with mole ratios (Dy/TCP) 0-1.0 were uniaxially dry-pressed at 50MPa to disks or bars, before cold isostatic pressing at 100MPa. The specimens were fired at 1000-1400°C for 10min-20hrs in air. The phases observed in the fired specimens above 1250°C were α-TCP and HAp for Dy/TCP mole ratio=0-0.01, α-TCP, Dy-containing β-TCP and HAp for Dy/TCP ratio=0.05, Dy-containing β-TCP and HAp for Dy/TCP ratio=0.10-0.35, and Dy-containing β-TCP, DyPO₄ and HAp for Dy/TCP ratio=0.40-1.0. The upper solubility limit of Dy in β-TCP was reached when the Dy/TCP ratio was 0.33. The relative density≥95% was achieved when the Dy/TCP ratio was 0.10-0.25 above 1300°C (3hrs). The maximum relative density was 97% at 1300°C, over 98% at 1350-1400°C when the Dy/TCP ratio was 0.18. The sintered specimens (relative density≥95%) could be machined using metallic gravers or dental burs. The reason why the Dy-containing β-TCP ceramics are machinable seems to be due to the easy transgranular fracture of β-TCP grains doped with Dy. The three-point bending strength and Vickers' hardness of the bars sintered at 1300°C for 3hrs were in the range 30-50MPa and 2-3GPa, respectively, when the Dy/TCP ratio was 0.10-0.25. However, increasing firing temperature over 1350°C tended to decrease the bending strength because of grain growth. The linear thermal expansion coefficients were within 11-12×10^-6/°C (-900°C). The citric solubility%, which was determined under the condition of 1g of Dy-containing β-TCP powder (fired at 1300°C for 3hrs) and 150ml of 2% citric acid solution at 20°C for 1h, was about 95% when the Dy/TCP ratio was 0.05-0.33.

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Analysis of Single-Layered Corrugated Core Sandwich Plate by Homogenization Method

On the Application of Homogenization Method to Composite Structures with Only Planar Periodicity

Naoki TAKANO, Masaru ZAKO, Noboru KIKUCHI

1995 Volume 44 Issue 502 Pages 905-910
Published: July 15, 1995
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.44.905

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The effectiveness of the homogenization method for the analysis of composite materials has been shown since it was firstly introduced in the 1970's. As this method is applicable to periodic problems only, however, some important engineering problems remain unsolved. Those problems are, for instance, honey-comb sandwich plates and panels with reinforcing ribs, which are not periodic in the thickness direction. In this paper, the application of the homogenization method to those problems is discussed. As a pratical example, stress analysis of single-layered corrugated core sandwich plates is presented. A method to homogenize its complicated geometry to a simple solid model, to get the homogenized material constants, and to calculate the microscopic stress is proposed.

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Analysis of Viscoelastic Behavior of Fiber Composite Materials with Time Dependence of the Interface

Ken-ichi HIRASHIMA, Ryota HASHIZUME

1995 Volume 44 Issue 502 Pages 911-915
Published: July 15, 1995
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.44.911

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This paper treats viscoelastic interface problems for unidirectionally reinforced fiber composite materials. The analytical solutions of the effective axial shear modulus and the creep compliance of cylindrical fiber composites are obtained by using several typical models of linear viscoelastic behavior for the cases that shearing stress occurs at a circular viscoelastic interface under venous forces such as tensile force, bending, torsion and so on.
It is assumed that the behavior of linear viscoelastic interface can be expressed by Kelvin, Standard and Burgers models. Then, the constitutve equation of fiber composites is formulated and its analytical results are obtained by the correspondence principle between elasticity and linear viscoelasticity.
It is proved that the results by Standard, Maxwell and Kelvin models are reduced from the Burgers model with specialized mechanical coefficients. The effects of the interface thickness on the shear modulus and the creep compliance are shown by many graphical representations.

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Three-Dimensional Intelligent Finite Element Method for Design of Composite Structures

Design of Symmetric Laminates by Shell Element

Masaru ZAKO, Tetsuya TSUJIKAMI

1995 Volume 44 Issue 502 Pages 916-920
Published: July 15, 1995
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.44.916

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A computer program of the three-dimensional intelligent finite element method by using shell element has been developed in order to obtain the optimum fiber orientation and the optimum stacking sequence of laminate composites. In this paper, the strength of laminate is set as the design object. As the numerical example, the determination of fiber orientation in each layer of a laminated plate under uniformly distributed pressure has been carried out. The optimum fiber orientation and the optimum stacking sequence are obtained from the material database until the strength satisfies the design object by computer. As the result, it is recognized that the proposed method is very useful for the structural design of composites.

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Development of Three-Dimensional Finite Element Method for Composite Materials Based on Damage Mechanics

Masaru ZAKO, Tetsuya TSUJIKAMI, Naoki TAKANO, Takuya TSUMURA

1995 Volume 44 Issue 502 Pages 921-926
Published: July 15, 1995
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.44.921

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A computer program of the three-dimensional finite element method for composite materials based on damage mechanics has been developed. There are many kinds of fracture pattern in composite materials. Especially, the progression of fracture caused by out-of-plane and shearing deformation is very complex. The effect of these fracture patterns on the mechanical behavior must be considered for the design and analysis of fracture behavior of composites. The consideration of damage mechanics has been introduced into the proposed program in order to treat above mentioned behaviors. A numerical procedure with new concept for the constitutive equation with damaged elements is introduced in this paper. As an example, the mechanical behavior of laminate under three point bending was analyzed by the developed computer program. The computational results concerning the fracture pattern agreed well with the experiments. Consequently, it can be recognized that our proposed program is very useful for structural design and analysis of mechanical behavior for composite structures.

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Observation of Grinding Damage and Bending Strength of Ceramics

Katsushi SARUKI, Akira YAMADA

1995 Volume 44 Issue 502 Pages 927-932
Published: July 15, 1995
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.44.927

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Grinding damage of ceramics was observed on sialon by the Pd pregnation method. The procedure of the method is spreading of Pd solution, loading up to 1/3 of fracture load, drying, fracturing and analyzing of the fracture surface by EPMA. The specimens mainly used were rectangular bars (3×4×36mm) ground transversely with #600 and #140 grindstones, and round bars (φ4×36mm) ground circumferentially with #600 and #325 grindstones. Bending strength was obtained by subjecting the specimens to a 4-point loading test (inner span 10mm, outer span 30mm). The examination revealed that the grinding damage to the specimens mentioned above was the creation of some cracks in the depth range of 4-50μm. The relation between the fracture stress σ_f and the equivalent crack length a_e is shown by an upward convex curve on logarithmic paper. The curves are expressed by eqn. K_IC=σ_f√π(a_e+a_e0) or eqn. K_IC=σ_f(a_e+r)·√π/{a_e+(r/2)}, where K_IC is a fracture toughness value, a_e0 is an equivalent latent crack length, and r is a microstructure parameter. The experimental results correspond well to these equations by using 14-15μm as a_e0 and 8-9μm as r, which are about twice as large as the values for a natural pore defect.

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Effect of Microstructure on Fatigue Behaviour of Ti-15Mo-5Zr-3Al Alloy

Jian-Chun BIAN, Keiro TOKAJI, Masaki NAKAJIMA, Takeshi OGAWA

1995 Volume 44 Issue 502 Pages 933-938
Published: July 15, 1995
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.44.933

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The fatigue behaviour has been studied under rotating bending using the materials with three different microstructures (β grain sizes) of a Ti-15Mo-5Zr-3Al alloy which were solution-treated at 735°C (STA735), 850°C (STA850) and 1000°C (STA1000) followed by aging at 500°C. It was found that STA735 showed the highest fatigue strength, and in the materials solution-treated above the β transus, STA850 and STA1000, the fatigue lives decreased with increasing solution temperature i.e. β grain size but the fatigue limit was almost the same in both materials. Fatigue cracks were initiated as a consequence of slip deformation in STA735, while at β grain boundaries in both STA850 and STA1000. In particular, STA850 exhibited an interesting initiation behaviour in which cracks were initiated at the specimen surface at high stress levels, but subsurface crack initiation was observed at low stress levels. The growth rate of small cracks was almost identical for all the materials, indicating no influence of solution temperature. Therefore, the observed difference in fatigue strength was attributed to the resistance to crack, initiation of the microstructures studied.

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Influence of Solution Treatment on Rolling Contact Fatigue Strength of Mild Steel

Shun-ichi NOKUBO, Takashi FUKUI, Akira SAWAMOTO

1995 Volume 44 Issue 502 Pages 939-944
Published: July 15, 1995
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.44.939

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Studies on the characteristics of the rolling contact fatigue strength of mild steel which was solutiontreated and quenched at low temperature have been made. The rolling fatigue test was started immediately after the specimens were solution-treated at 700°C, 650°C or 600°C for 20 minutes and quenched into water bath. The test results of these stress aged specimens were compared with those of the age-hardened specimens after solution treatment and quenching at low temperature. The test was conducted by use of a Nishihara-type wear testing machine under pure rolling contact with lubricant.
The results obtained are as follows;
(1) The rolling contact fatigue strength of mild steel is markedly increased by the stress aging treatment as well as the age-hardening treatment.
(2) The maximum rolling contact fatigue endurance limit of the age-hardened specimens and the stress aged specimens, except the one subjected to solution treatment at 600°C, is shown by the following empirical formula; 3.6·Hv'-290.
(3) At the early stage of the rolling contact fatigue process, work hardening of the stress aged specimen occurs and the contact surface of the specimen becomes smooth.

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Fatigue Crack Growth Behavior of Alumina Short Fiber Reinforced Aluminum Alloy at Room Temperature

Tsuneshichi TANAKA, Hideaki NAKAYAMA, Shigeru YAMAMOTO, Yukiyoshi KOBA ...

1995 Volume 44 Issue 502 Pages 945-952
Published: July 15, 1995
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.44.945

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In order to clarify the fatigue failure mechanism of an alumina short fiber reinforced aluminum alloy (FRM), a series of fatigue crack growth tests were carried out under several stress ratio conditions on the center cracked tension (CCT) and compact tension (CT) specimens. The crack growth rate was observed for CCT specimens and the crack opening displacement was measured by using a clip gauge attached at the crack mouth of CT specimens. Aluminum alloy, A6061-T6 was also used as a reference material.
The comparison of fatigue crack growth rate curves determined on A6061-T6 and the FRM specimens indicated that FRM had low fatigue crack growth resistance in comparison with A6061-T6 alloy in the high crack growth rate region. And it was revealed that both the crack opening ratio and crack opening displacement of FRM were suppressed under a high stress ratio of R=0.7, due to the bridging effect of alumina short fibers. The fatigue crack growth rate of FRM was not governed only by the effective stress intensity factor range, ΔK_eff, contrary to the case of monolithic metallic materials. A detailed evaluation indicated that the fatigue crack growth rate of the FRM could be expressed by using both K_max and ΔK_eff as follows:
da/dN=C{(K_max)^α(ΔK_eff)^1-α}^m

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Mode I Fatigue Delamination for CF/PEEK Laminates Using Maximum-Energy-Release-Rate Constant Tests

Masaki HOJO, Shojiro OCHIAI, Takahira AOKI, Hidetaka ITO

1995 Volume 44 Issue 502 Pages 953-959
Published: July 15, 1995
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.44.953

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The near-threshold growth of delamination fatigue cracks under different stress ratios was investigated with unidirectional laminates made from ICI APC-2(AS4/PEEK). Tests of mode I delamination fatigue crack propagation were carried out by using double cantilever beam specimens. The crack growth rate decreased with crack extension under the constant maximum energy release rate (G_max-constant) test. The true growth law which is not affected by fiber bridging was obtained by the growth rate at zero-increment of the crack length from a series of G_max-constant fatigue test. Then, the increase of the crack growth resistance caused by fiber bridging was evaluated. Although the saturated level of this increase was almost the same for both the fatigue and static tests, the length of the saturation for this increase was much longer for the fatigue test than that for the static test. The differences of the crack growth behavior and the stress ratio dependency between the G_max-constant test and the conventional G_max-decreasing test were discussed on the basis of the mechanism consideration.

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Effect of Stress Ratio on Mode I Propagation of Interlaminar Fatigue Cracks in CFRP

Keisuke TANAKA, Hiroshi TANAKA, Tatsuya TSUJI, Kenjiro YAMAGISHI

1995 Volume 44 Issue 502 Pages 960-966
Published: July 15, 1995
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.44.960

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rowth behavior of mode I interlaminar cracks in a unidirectional carbon/epoxy laminate, Toray T800H/#3631, was studied under cyclic loading at different stress ratios. Under a constant value of the applied stress intensity range, ΔK_Iap, the crack propagation rate decreased with the crack extension due to crack-tip shielding by fiber bridging. The crack propagation rate was expressed by a power function of the maximum value of the crack-tip stress intensity factor: da/dN=C₀(K_{_Itip, max}/K_Ic)ⁿ, where C₀ and fracture toughness K_Ic are the material constants, while the exponent n strongly depends on the stress ratio. The reduction rate in K_Itip due to fiber bridging was determined only by the crack extension Δa, but not by the applied load or the stress ratio. The upper bound of the crack propagation rate can be estimated from the scatter of fracture toughness and the fiber-bridging effect of materials. Change in load amplitude has no influence on either the da/dN-K_{Itip, max} relation nor the reduction rate in K_Itip.

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Long Term Stability and Microstructure of Steam Cured High Strength Concrete with Ettringite Based Additives

Hiroshi MUGURUMA, Yoshihisa MATSUNAGA, Yoshiharu WATANABE, Etsuo SAKAI

1995 Volume 44 Issue 502 Pages 967-972
Published: July 15, 1995
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.44.967

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In this paper the microstructure and long term stability of steam cured high strength concrete with anhydrite or ettringite based additive containing anhydrite (EBA) are discussed. Concrete in which anhydrite alone was incorporated craked after 1 year. However, the use anhydrite with the optimum size of crystal grains to control the solubility rate of anhydrite and the additives (EBA) developed by combination of anhydrite and silicious materials, made it possible to produce a high strength concrete which has no crack after the lapse of about 14 years to confirm that the concrete can be stabilized over a long period. The impact strength of the high strength concrete with anhydrite and blast furnace slag is smaller than that of the one with anhydrite and silicious materials.
By adding EBA, anhydrite is decreased at the beginning of the reaction and at the same time AFt is increased. It is observed that larger needle like crystals of AFt grow in a pore. In addition, the hydration of alite is accelerated by EBA. So, the total pore volume of the hardened cement is remarkably decreased by incorporating EBA.

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Computer Simulation on Deformation of Engineering Materials at High Temperature

I: Metallo-Thermo-Mechanics -Theory and the Application to Some Engineering Processes Incorporating Phase Transformation-

Tatsuo INOUE

1995 Volume 44 Issue 502 Pages 973-980
Published: July 15, 1995
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.44.973

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