Journal of the Society of Materials Science, Japan

Damage Mechanics

Continuum Mechanics Approach to Damage and Fracture of Materials

Sumio MURAKAMI

1982 Volume 31 Issue 340 Pages 1-13
Published: January 15, 1982
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.31.1

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Comparison in Fatigue Crack Growth Rate between In-Plane Bending and Cyclic Torsion

Shoji HARADA, Kiyotsugu OHJI, Keiji OGURA

1982 Volume 31 Issue 340 Pages 14-17
Published: January 15, 1982
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.31.14

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Fatigue crack growth under multiaxial loading is of importance in engineering practice. In order to examine the effect of stress biaxiality on the fatigue crack growth rate, torsional (biaxial) and uniaxial bending fatigue tests were carried out in this study by using a tough-pitch copper. The experimental results showed that in the case of torsional fatigue the compressive non-singular stress acting parallel to the direction of the initial cracked plane considerably accelerated the mode I crack growth rate in comparison with the result of the uniaxial bending fatigue test.

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Effects of Film Forming Conditions on the Strength of a Cross-Oriented Polyethylene Tubular Film

Michio SUDO

1982 Volume 31 Issue 340 Pages 18-21
Published: January 15, 1982
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.31.18

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Relationship was investigated between the conditions for producing multi-layer film with transversely stretched high density polyethylene tube as the inner layer and vertically stretched polyethylene tube as the outer layer, and various properties such as impact resistance, propagation tear resistance, etc.. Production conditions which will meet the requirements for heavy-duty bag were obtained. The results obtained are summarized as follows:
(1) Low density polyethylene used for the outer layer gave a higher impact resistance and propagation tear resistance compared with high density polyethylene.
(2) With increasing the thickness of the film, the impact and propagation tear resistance increased. Thickness between 100-140 microns will be sufficient for heavy-duty uses. Whether the inner layer thickness should be increased or the whole thickness should be increased will be determined in connection with other properties.
(3) The increase of vinyl acetate contained in ethylene vinyl-acetate co-polymer used as the intermediate layer reduced propagation tear resistance. It is recommended to use ethylene vinyl-acetate co-polymer containing 5-6% vinyl acetate.
(4) With increasing the thickness of the outer layer, impact resistance was lowered. The ratio in thickness of the intermediate to the outer layer should be 7 to 3 in principle.
(5) Increase in draw ratio of the outer layer led to higher propagation tear resistance in the vertical direction. The draw ratio of 1.1 to 1.3 is recommended.
(6) It is suggested that the bond strength of the inner layer with the outer should not be too high in order to increase propagation tear resistance.

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On the Corrosion Tubercles of Iron Rust in Aerated Neutral Boric-Borate Buffer Solutions

Masaki YASUDA, Fumio HINE

1982 Volume 31 Issue 340 Pages 22-27
Published: January 15, 1982
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.31.22

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Formation of corrosion tubercles on carbon steels were carried out in the aerated neutral solutions composed of boric-borate buffer (0.01M) and water with some suspensions of CaCO₃ and CaSiO₃ powders at pH=7.5-8.8. The solutions containing NO₂^-, CrO₄^2-, or HS^- of less than 50ppm in concentration were also examined. The solution temperature was at 60-65°C.
The tubercles thus formed were classfied into three types: the active passive, the general corrosion, and the sulfide initiative, depending on the potential. The active passive-type tubercles formed at the potential range where the second peak of current appeard on the anodic polarization curve. On the other hand, the general corrosion-type tubercles grew at the potentials where general corrosion of steels tested appeard. In the latter case, calcium scale deposited on the steel surface, but the corrosion spots formed partially at which the scale deposition was insufficient.
The mechanism for the sulfide initiative-type tubercles is unclear whereas it forms certainly in aerated and neutral solutions containing HS^- at the potential range -0.50 to -0.55V vs. Ag/AgCl.

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Work Index of Dry and Wet Grindings

Yoshiteru KANDA, Masahiro HASEGAWA, Michitaka SUZUKI, Hiroshi GUNJI, T ...

1982 Volume 31 Issue 340 Pages 28-31
Published: January 15, 1982
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.31.28

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Recently the authors proposed the following experimental formulas expressing the zero order increasing rate constant of mass fraction less than a size x, K_x, during dry and wet ball mill grindings.
Dry: K_x(D)=0.019H_V^-0.47(W_S/W_B)^-1.5(x/x_f)(x_f/x_o)^0.7
Wet: K_x(W)=0.05H_V^-0.47(W_S/W_B)^-1.0(x/x_f)(x_f/x_o)^0.5
On the other hand, Work Index W_i proposed by Bond was inversely proportional to the ball mill grindability G_b·p^0.82 and G_b·p was proportional to K_x·W_S.
From these results, it was found that the difference of Work Index W_i between dry and wet grindings was expressible by the following equation.
W_i(W)/W_i(D)={0.38(W_S/W_B)^-0.5(x_f/x₀)^0.2}^0.82

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Some Applications of Global J Scalar to Three-Dimensional Cracks

Shiro KUBO, Kiyotsugu OHJI

1982 Volume 31 Issue 340 Pages 32-38
Published: January 15, 1982
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.31.32

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In a previous paper J-integrals of a three-dimensional crack embedded in a linear or nonliner elastic material were discussed. J-integrals of three-dimensional cracks proposed so far were classified into three categories; local J vector, local J scalar and global J vector. A new parameter, global J scalar, was also proposed which was defined by using a kind of crack extension vector. The characteristics and the interrelation of these four J-integrals were discussed. It was shown that the global J scalar plays a very important role in the understanding of J-integral of three-dimensional cracks.
In this paper some applications of the global J scalar were made. The results obtained are as follows:
(1) Rice's J-integral and Knowles-Sternberg's M- and L-integrals were derived from the global J scalar as its special cases. The global J scalar is a generalized form of J-, M- and L-integrals. Some extensions of M- and L-integrals were made by using the global J scalar.
(2) As one of the simplest applications of J-integral of three-dimensional cracks, two expressions of J-integral at the tip of an axi-symmetric crack were obtained by using the local J-vector and the global J-vector. Many expressions, including these two expressions, were also derived using the global J scalar.
(3) An application of the global J scalar to an arbitrary three-dimensional crack was presented. An economical method to determine the distribution of value of J-integral along the crack front was proposed.

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Fractographic Inspection of Aluminum in Air and Vacuum

Toshiji KUROBE, Haruo TOMIZU

1982 Volume 31 Issue 340 Pages 39-44
Published: January 15, 1982
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.31.39

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Fractographic inspections have been conducted to know the failure mechanism of a aluminum which was subjected to stress cycling under the pressure range from the ambient pressure to 10^-5 Torr. The topography of fracture surface has been examined by an optical and electron microscopy, and the chemical state and/or its properties have been analyzed by using ESCA and X-ray microanalyzer. The deterioration of fatigue strength in air has been discussed on the basis of the mechanisms of chemical and physical adsorption of the constituent gas in air to the fresh crack surface.
The fracture surface appearance photographed by camera has shown that its morphology of specimen tested in air was very rugged, while it was relatively smooth in high vacuum pressure level over 10^-3Torr. The dark deposits were observed on the fracture surface of the air-tested specimen, but not on the vacuum-tested one. The surface inspections by an X-ray microanalyzer indicated that the amount of oxygen molecules adsorbed on the fracture surface changed drastically in the region of 10^-2 to 10^-3Torr. The analytical survey by ESCA showed a marked signal of chemical shift from aluminum metal to aluminum oxide in the air-tested specimen, but not so in the vacuum tested one. These physico-chemical effects may have a great influence on the degradation of fatigue strength of aluminum in air.

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Low-Cycle Fatigue of Pre-Strained Pure-Aluminium

Kenji SHOWAKI, Kiyoshi MATSUURA

1982 Volume 31 Issue 340 Pages 45-50
Published: January 15, 1982
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.31.45

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The effect of pre-strain on the behavior of lattice defects during cyclic straining was analysed theoretically. In order to ascertain the propriety of the results obtained, wires of cold worked aluminium were further cyclically strained in torsion with a constant strain amplitude at 77K or R. T.
The dislocation density during cyclic straining was given as a function of cumulative strain by
ρ_m=(1-f)ρ_pre+f(α₂/β₂)²[1-(1-ρ_pre^1/2β₂/α₂)e^-β₂γ/2]2 0≤f≤1
where ρ_m: mean dislocation density, ρ_pre: mean dislocation density in pre-strained metal, α₂, β₂: constants.
A detailed model for cyclic peak stress vs. cumulative strain response was developed from this equation, on the assumption that the amount of strain hardening is proportional to square root of the mean dislocation density. For cyclic straining with the condition of ρ_pre>(α₂/β₂)², the dislocation density decreases gradually with the number of cycles to(α₂/β₂)². Metals therefore show the behavior of fatigue softening.
The concentration of point defects C_i in pre-strained metal during cyclic straining at low temperatures such as 77K, is as follows:
C_i=C_s[1-1-ρ_pre^1/2β₂/α₂/K₂-β₂/2(K₂e^-β₂γ/2-(β₂/2-ρ_pre^1/2K₂β₂/α₂/1-ρ_pre^1/2β₂/α₂)e-^K₂γ)]
C_s=K₁α₂/K₂β₂
where K₁, K₂: constants.
The density of lattice defects calculated from the above equations agreed with that estimated through resistivity measurements on fatigued specimens at 77K.

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Effect of Sheet Thickness on Retardation Behaviour of Fatigue Crack Propagation of Low Carbon Steel

Keiro TOKAJI, Zenji ANDO, Toshio IMAI, Kunihiko MORIKAWA

1982 Volume 31 Issue 340 Pages 51-56
Published: January 15, 1982
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.31.51

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The effect of sheet thickness on the fatigue crack propagation behaviour was studied by using the specimens of low carbon steel with different thickness (2mm and 8mm) under the condition of stress ratio R=0 and frequency f=10Hz.
Under the constant load-amplitude-tests, the fatigue crack propagation rate was not affected by sheet thickness and the effective stress intensity factor range ratio, U, measured on the specimen surface increased with increasing stress intensity factor range, ΔK.
Both of the specimens indicated the delayed retardation behaviour following a single tensile overload application, and the affected crack length, l^*, in the thin specimen was larger than that in the thick specimen. Retardation behaviour could be classified by the effective, stress intensity factor range, ΔK_eff.
The midsection of sheet thickness in the thick specimen as well as its surface indicated the same delayed retardation behaviour. It seems that this behaviour depends strongly on the stress state at the crack tip.
The value of l^* was markedly larger than the calculated plastic zone size. However, the hardened zone ahead of the crack tip measured by a micro Vickers hardness tester (25g) showed a good agreement with l^*.

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Effect of Environments on Fatigue Crack Propagation of SNCM 439 under Two-Step Varying Load

Masaki NAKAJIMA, Yozo KATO, Motohisa HIROSE, Norihiko HASEGAWA

1982 Volume 31 Issue 340 Pages 57-63
Published: January 15, 1982
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.31.57

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The effect of two-step varying load on the fatigue crack propagation of SNCM 439 was investigated in room air, distiled water and 3.5% NaCl solution. A small number of cycles at higher stress level were applied periodically during a large number of cycles at lower stress level than the fatigue limit. After each cycling, the crack growth was measured and the growth rate was compared with that at each steady stress amplitude.
The conclusions are as follows;
(1) 2 cycles at higher stress only caused the acceleration of crack growth at higher stress side. On the other hand, in all other cases the acceleration was not observed.
(2) In the application of the linear cumulative damage concept, the cumulative damage life extended remarkably compared with the life at steady stress.
(3) The similar tendency above mentioned of crack propagation behavior also appeared in corrosive environments.
(4) It is confirmed that the crack propagation behavior depends on the number of cycles at higher stress in one program unit.

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Corrosion Fatigue of Mild Steel and Cr-Mo Cast Steel in Fresh Water and Corrosion Inhibition Using Inhibitors

Kenzo MIURA, Makoto KUMADA, Toshitsugu OHI

1982 Volume 31 Issue 340 Pages 64-69
Published: January 15, 1982
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.31.64

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In order to prevent corrosion damage, at present, corrosion inhibitor is added to the engine cooling water, as fatigue cracks appear on the surface of the water side of the cylinder cover in marine diesel engines. In the present study, rotating bending fatigue tests were carried out in fresh water similar to actual environments, and the damage from corrosion fatigue on the surface of the surface of the specimens, as well as the effect of the corrosion inhibitor in preventing corrosion fatigue were examined.
The S-N curves or S-T curves in fresh water levelled off but they began to descend again. It was found that the damage due to corrosion fatigue appeared distinctly over a long period even if the stress amplitude was low, and many corrosion pits and microcracks existed besides the main crack. A linear relation was obtained experimentally between the term (k-1) and the term (1/f_p), where k is the corrosion effect and f_p is the pitting factor. On the other hand, the corrosion fatigue strength in fresh water became equal to or greater than that in air when a sufficient amount of corrosion inhibitor over the critical concentration required for corrosion inhibition was added.

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Fatigue Behavior of Epoxide Resin Having Different Network Structures

Masaki SHIMBO, Mitsukazu OCHI, Takashi NAGASAWA, Seiichi YAMAMOTO

1982 Volume 31 Issue 340 Pages 70-76
Published: January 15, 1982
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.31.70

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The fatigue behavior of structural adhesives composed of a bisphenol type epoxide resin, aliphatic α, ω dicarboxylic acids HOOC-(CH₂)_p-COOH (p=2, 4, 8, 10), an amine-type accelerator and an amine-type catalyst was investigated by analyzing the results of fatigue tests, bulk properties and SEM of fractured surfaces of the systems. Ether type, ester type and the mixed type network structures were formed by using the amine catalyst and the carboxylic acids with and without accelerator.
On the basis of the above observations, the mechanism for improvement of fatigue strength was discussed in terms of the segmental structures, high relaxational ability, transformation of mechanical stress into heat, and restricted segmental motion for the cured systems.
A good correlation of the fatigue strength with the concentration of network chains, fracture energy or area of tanδ curve was found.

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Effects of Alloying Elements on Creep and Creep Rupture Properties of 20Cr-25Ni Heat Resisting Cast Steels

Tomohiro TSUCHIYAMA, Toshio FUJITA, Komei KASAHARA

1982 Volume 31 Issue 340 Pages 77-83
Published: January 15, 1982
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.31.77

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In order to develop a new heat resisting cast steel which has an excellent creep rupture properties and is free from the precipitation of sigma phase at the temperature range of 700°C to 800°C, the effects of Nb, Mo, W, and C on creep and creep rupture properties were studied on 0.45C-20Cr-25Ni cast steel.
The tensile properties at room temperature were not affected so much by alloying elements. The creep rupture strength became higher with increasing the amount of alloying elements but the excessive addition led to lower creep rupture strength at 700°C. The creep strength, however, became lower with increasing alloying elements. Thus, the creep rupture strength did not correspond to the creep strength. Creep rupture elongation became higher with increasing alloying elements. These results were attributed to the difference in precipitation morphology of eutectic carbide. From the present work, 0.45C-20Cr-25Ni-2Nb-2Mo-2W cast steel was found to have an excellent creep rupture properties.

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Influence of Cooling Rate on Eutectic Cell Structure and Mechanical Strength of Gray Cast Irons

Kaneo MIZUNO, Tatsuichi FUKUSAKO

1982 Volume 31 Issue 340 Pages 84-89
Published: January 15, 1982
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.31.84

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A study has been made on the cooling rate, eutectic cell structure and mechanical strength of round, square and triangular castings of different forms having the same sectional area. It was found that the cooling rate, even for the same sectional area, varied according to their forms and that it became greater in the order of round, square and triangular castings. The same was true with the number of eutectic cell and the mechanical strength. On the basis of these results, the following theory was established.
(1) The cooling rate of castings can be determined by the ratio of volume to surface area.
(2) A linear relationship, by the logarithmic graph paper, can be established among the nth power of modulus (M) of castings of different forms, the lapse of time (t), the cooling rate (V_s) and the number of eutectic cell (N). The relation can be expressed as t=AM^nf, V_s=BM^-nf, N=HM^-nf where A, B and H are constant and f value in each case becomes f≈1. The values of n obtained were 2.0 for a round bar, 2.3 for a square bar and 2.5 for a triangular bar.
(3) Among the cooling rate, the mechanical strength (tensile strength σ_B, Brinell hardness H_B) and the number of eutectic cell, the relationships σ_B=C₁V_s^f, H_B=C₂V_s^f, N=GV_s^f were obtained.
(4) Between the number of eutectic cell and mechanical strength, σ_B=J₁N^f and H_B=J₂N^f, where C₁, C₂ G, J₁ and J₂ are constant, were obtained.

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Protection from Tufftriding by Inorganic Coating

Chuji KAGAYA, Masanori KATO, Takeomi WASADA, Noboru EGAMI

1982 Volume 31 Issue 340 Pages 90-95
Published: January 15, 1982
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.31.90

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The anti-tufftride for ferrous materials was examined by applying inorganic coating on ferrous specimens. The coating was hardened at 150°C for 60 minutes. The coated specimens were water-cooled after soaking in the salt bath for 90 minutes, and tempered. Their microstructures were investigated.
The experimental results showed that the formations of compounds and the diffusion layer in the anti-tufftride zone of the specimen were very much restrained by the inorganic coating, and hardness increased very little. The inorganic coating was found to be very effective as anti-tufftride.

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Hardness of Creep Ruptured Specimens of 12% Cr Heat Resisting Steel and Its Application to the Residual Life Prediction

Tomohiro TSUCHIYAMA, Toshio FUJITA

1982 Volume 31 Issue 340 Pages 96-102
Published: January 15, 1982
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.31.96

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Creep rupture tests of 12% Cr heat resisting steel with various heat treatments were carried out, and the application of hardness of creep ruptured specimens for the residual life prediction was investigated.
Creep rupture strength was affected by the heat treatment condition at a short test duration, but the difference of creep rupture strength tended to diminish at a long test duration. The hardness of creep ruptured specimens had the same tendency with the creep rupture strength. In spite of the difference in heat treatments, the relation between the hardness of creep ruptured specimens and the applied stress was liner.
By assuming that the steel fractured when the hardness softened and approached to a critical value which was determined by the applied stress, the equation for calculating the creep rupture time was formulated. It was confirmed that the creep rupture time could be calculated precisely.

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Applicability of Indirect Tensile Test Method with Frame Specimens to Concrete

Mitsuru SAITO, Kazuo KURATA, Seiichi ARAKAWA

1982 Volume 31 Issue 340 Pages 103-108
Published: January 15, 1982
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.31.103

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Many indirect tensile test methods have been proposed for concrete, because the direct tensile test has various difficulties in applying it to concrete. However, the biaxial stress state and/or the sharp stress gradient occur in the specimens used in the usual indirect tensile tests. Therefore, it may be difficult to obtain tensile stress-strain curves of concrete by the usual indirect tensile tests. This study aims at examining the applicability of a tensile test method with frame specimens to concrete by clarifying the stress distributions in the specimens at loading by FEM analyses. The FEM analyses showed that the stress in the horizontal bar of frame specimen was uniform and uniaxial when a suitable shape of frame specimen was adopted. The experimental results showed that loading was extremely easy in the test method with frame specimens as compared with that of the other tensile test methods of concrete. It was also found that the tensile strength and the modulus of elasticity of concrete obtained by the method with frame specimens agreed with those obtained by the direct tensile test method. These facts suggest that the test method with frame specimens can conveniently be used in the fatigue and creep tests of concrete under tensile loading.

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Computer Aided Design on Composite Materials

VI. Mechanical Behaviour of Composite Materials Based on the Heterogeneous Structure under Uniaxial Load

T. Hirai

1982 Volume 31 Issue 340 Pages 109-115
Published: January 15, 1982
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.31.109

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