Journal of the Society of Materials Science, Japan

Materials Involving Fluorine

Akimasa TASAKA, Nobuatsu WATANABE

1979 Volume 28 Issue 309 Pages 457-470
Published: June 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.457

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Compression and Stress Relaxation of Copper Powders

Yoshiharu MORIMOTO, Takuo HAYASHI

1979 Volume 28 Issue 309 Pages 471-477
Published: June 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.471

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Experiments and theoretical analyses have been carried out on constitutive equations of copper powders. The results obtained are as follows.
(1) The stress-density relation of electrolytic copper powders is sensitive even to low strain rates of about 10^-2∼10^-5/sec in compression at room temperature. The higher the strain rate is, the larger the stress at the same density is.
Moreover, stress relaxation phenomena are affected by the history of loading processes. The compacted powders compressed by rather high strain rates show a larger stress relaxation. The compacted powders of lower density show larger stress relaxation.
(2) When the strain rate is changed in the compression process, the stress-density relation changes rapidly to the new one which coincides with the stress-density relation obtained by the constant strain rate test corresponding to the new strain rate.
(3) The above character of powders can be expressed by the three element elastic visco-plastic model, and the behaviour of powders of various loading history can be calculated by this model. The calculation agrees qualitatively with experiments.

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Effect of Microduplex Structure Size on Tensile Fracture Behavior of Steels with Ferritic-Martensitic Structures

Hideto SUZUKI, Takeshi KUNIO

1979 Volume 28 Issue 309 Pages 478-484
Published: June 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.478

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A study of the effect of microstructure on tensile property has been carried out on 0.25%C plain carbon steel (S25C) with duplex ferritic-martensitic microstructures. The variation in size of the microduplex structures makes a considerable difference in fracture strength σ_max of the material at room temperature. At σ_max stress level, a large crack formed by coalesence of n unit microcracks starts to extend unstably through the martensite at its tip. This fracture process suggests that the tensile strength of the present material can be estimated by the following equation.
σ_max=√6w_m/n(2d_f+w_m)σ_ym

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Effect of Mean Stress on Low-Cycle Torsional Fatigue Life of Piano Wires

Akio GENTSU, Keizo FUJITANI

1979 Volume 28 Issue 309 Pages 485-490
Published: June 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.485

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Although several ways have been proposed to predict low-cycle torsional fatigue life of metals under load controlled cycling conditions with mean stress, none of them is satisfactory for all materials and test methods.
In this study, in order to investigate the influence of mean stress on the fatigue life of piano wires in a constant load cycling test, the low-cycle torsional fatigue tests were carried out on 0.84% C piano wires under load controlled cycling conditions with various stress ratios.
The fatigue characteristic of each specimen was discussed and the fatigue fracture criteria, applicable to the load controlled fatigue test and given by the following equation, were proposed.
D=γ_po/γ_f+κ{1/C₀∫^N₀Δγ_p^adn+∫^N₀Δγ_c/γ_fdn}
κ=τ_0maxN₀/τ_maxN
where Δγ_p and Δγ_c are the ranges of plastic strain and permanent strain, respectively, dn is the infinitesimal increment of the number of strain cycles n, γ_p0 is the strain for the first cycle, a is a material constant, C₀ is the average value of the constant C₀ obtained from the equation 1/C₀∫^N₀Δγ_p^adn =1 when the mean stress is zero, N and τ_max are the number of cycles to fracture and the maximum stress when the mean stress is applied, respectively, N₀ and τ_0max are those at zero mean stress, and γ_f is the fracture strain in the static test.
From the test results, it was confirmed that the above equation is well applicable to the fracture life in low-cycle torsional fatigue tests with mean stress under load controlled conditions.

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Effect of Cold Work on Fatigue Crack Propagation Rate Regarding to the Accumulated Plastic Strain Rate

Yasuyoshi FUKUI, Shigetomo NUNOMURA

1979 Volume 28 Issue 309 Pages 491-496
Published: June 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.491

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Fatigue crack propagation test were performed on single edge-notched pre-strained 7075-T6 aluminum alloy specimens. The similarity between the effect of pre-strain and that of stress ratio on fatigue crack propagation rate was confirmed by taking the acccumulated plastic strain rate, which involves not only the accumulated plastic strain in the monotonic plastic zone but also the plastic pre-strain. An analytical expression was proposed to explain the effect of pre-strain (i. e., the effect of cold work) quantitatively together with the effect of stress ratio. The applicability of this expression was evaluated by examining the effects of cold work and stress ratio on fatigue crack propagation rate of 7075-T6 aluminum alloy and various alloys determined previously.

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Effect of Pre-Strain on Fatigue Crack Propagation in Low-Carbon Steel

Keisuke TANAKA, Toshihiko HOSHIDE, Shuji TAIRA

1979 Volume 28 Issue 309 Pages 497-503
Published: June 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.497

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The concepts of crack closure and J integral were applied to analyze the effect of pre-strain on fatigue crack growth in low-carbon steel, which was monotonically pre-stretched to 15 percent plastic strain and cyclically pre-strained to about the half of the total fatigue life. The treatment of pre-strain did affect considerably the relation between the growth rate and the stress intensity factor. On the other hand, no significant effect was found when the rate was correlated to the effective range of stress intensity factor in the cases of small scale yielding. For both small and large scale yielding situations in all cases of pre-straining treatments examined, the growth rate was found to be a single-valued function of the crack tip opening displacement range or the J integral range. The mechanistic aspect of fatigue crack growth mechanisms was discussed based on the experimental results.

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Influence of Stress Concentration on Spread of Strength and Fatigue Life in FRP

Taichi FUJII, Zenichiro MAEKAWA

1979 Volume 28 Issue 309 Pages 504-509
Published: June 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.504

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The fiber reinforced plastics (FRP) have recently been attracting general attention as a light weight structural material. It is important in design of FRP structural components to establish a general concept which can account for those properties peculiar to composite materials. Moreover, an engineer often confronts some problems when he tries to design complex full scale structures from the design data obtained from small scale characterization tests on laboratory specimens. The estimation of structural reliability from labolatory data requires at least the following three penalty factors involved in the determination of the design stress in the component: The scale effect, the shape effect and the complexity factory. These factors were reported by Halpin for graphite-epoxy and glass-epoxy laminates.
In this study, static tensile and cyclic loading were imposed on the specimens with a single and multiple holes as well as without it. The relations between the breaking strength or fatigue life and the shape or complexity effect were discussed in plain-woven glass fiber cloth reinforced plastics. The results computed with a consideration of extreme statistics and stress concentration showed a good agreement with the experimental data.

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Effect of Impact Velocity on Fracture Surface of Mild Steel

Toyomitsu SENDA, Masanori ICHIRYU, Makio AIBARA

1979 Volume 28 Issue 309 Pages 510-516
Published: June 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.510

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A gun type impact testing machine was built as a trial, which could fracture a specimen at any velocity higher than the impact velocity of the Charpy impact test. The effect of impact velocity on the fracture surface of mild steel was studied by the electron fractography. The main results obtained are as follows.
(1) The thickness of the dimple nucleation area at four edges of the fracture surface became thinner with increasing impact velocity. The dimples nucleation area on radial area decreased with the impact velocity.
(2) The number of the dimple whose minor axis was smaller than 2μm increased with the impact velocity, but the number of the dimple whose minor axis was larger than 2μm was constant.
(3) The nucleation rate of twins observable at the radial area increased, the nucleation rate of the river pattern at the edge of the cleavage facet decreased and the cleavage facet became larger with increasing impact velocity.

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Analysis of Longitudinal Compressive Impact of Bar Obeying Malvern-Type Constitutive Equation

Shohachi WAKASUGI, Yoshihiro GOTO

1979 Volume 28 Issue 309 Pages 517-522
Published: June 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.517

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Plastic wave propagation and residual strain induced in a finite-length bar impacted longitudinally by an elastic bar were analysed by using Malvern's theory. The following function was assumed as the strain-rate-dependent function g(σ, ε) in the Malvern-type constitutive equation, σ being stress and ε strain;
g(σ, ε)=ABEexp(ξ/D)-1/Aexp(ξ/D)+B
where ξ is overstress, E is Young's modulus, A, B and D are parameters. This function represents the experimental results of the strain-rate-dependence of metals well. The effects of the form of the function g(σ, ε) and the values of the parameters on the calculated mechanical behaviours were presented. Some problems encountered in the numerical analysis by the difference method were pointed out and the way of overcoming them was proposed.

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Comparison between Experimental and Calculated Results of Longitudinal Compressive Impact Test of Aluminum

Shohachi WAKASUGI, Yoshihiro GOTO, Yuichi NISHI

1979 Volume 28 Issue 309 Pages 523-528
Published: June 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.523

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Cylindrical rods of annealed aluminum (250mm in length, 14mm in dia.) were subjected to impact at various velocities. Cylindrical rods of an SCM3 steel (250 and 750mm in length, 16.0mm in dia.) having high elastic limit were used as an impact bar and a stress bar.
The experimental results were compared with the analytical results obtained by using the constitutive equation of the Karman type and the modified equations of the Malvern type. The results calculated by the proposed strain-rate-dependent function agreed well with the experimental results.
The strain plateau, which can be obtained analytically from the Karman type equation, was not observed clearly in the experiment.

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Effect of Strain Rate on Yield Behavior of Cold Rolled Steel Sheets

Takashi WATANABE

1979 Volume 28 Issue 309 Pages 529-534
Published: June 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.529

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Yield behavior of low-carbon steel sheets (0.07%C) has been examined under the strain rate of 10^-4 to 10^-1/sec at room temperature using an Instron tensile machine. Stress-strain curves have been recorded by using a transient converter (NF, E-5001: 8bits×1024wards), since the response of a X-Y, T recorder is not sufficient for the measurements under high strain rates. The experimental results by the transient converter show that the upper and lower yield points appear clearly before the crosshead speed reaches to a given value of high strain rate. The transient converter is found most desirable in order to observe the yield behavior under high strain rates. The results also show another break point of the strain rate dependence of yield stress at the strain rate of ∼3 ×10^-3/sec, which is different from M. J. Manjoin (1944)'s strain rate i. e. ∼10^-1/sec. The strain rate dependences of yield stress, yield point elongation, and tensile strength in the range of high strain rate above ∼3×10^-3/sec are larger than those at lower strain rates. The yield stress is much more sensitive to the strain rate as compared with the tensile strength.

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Wear Properties of Polyvinyl Chloride

Osamu MAEDA, Yoshimitsu TAJIMA

1979 Volume 28 Issue 309 Pages 535-539
Published: June 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.535

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Sliding components of electrical communication apparatus, such as cams and dial switches are frequently used under discontinuous sliding conditions. Wear properties of plastics have so far been investigated under continuous sliding conditions, and have little been investigated under discontinuous sliding conditions.
In this paper, wear properties of polyvinyl chloride (PVC) were determined under discontinuous sliding conditions and the results were compared with those determined under continuous sliding conditions. Furthermore, the effect of lubricant content on wear property of PVC was examined under discontinuous sliding conditions.
The results obtained are summarized as follows;
(1) Under continuous sliding conditions, the wear volume of PVC increased linearly with sliding distance. However, the wear volume increased steeply when sliding distance exceeds a certain value.
(2) The wear volume of PVC determined under discontinuous sliding conditions agreed with the value estimated from the slope of the linear region observed under continuous sliding conditions.
(3) The wear volume of PVC decreased with increasing lubricant contents under discontinuous sliding conditions.

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Characteristics of Wood

1. Fine Structure of Wood Cell Wall

H. Harada

1979 Volume 28 Issue 309 Pages 540-546
Published: June 15, 1979
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.28.540

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