Journal of the Society of Materials Science, Japan
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
Volume 27 , Issue 300
Showing 1-17 articles out of 17 articles from the selected issue
  • Shozo OKAZAKI, Hiroshi NAKAMURA, Toshiyasu TSUNENARI
    1978 Volume 27 Issue 300 Pages 816-822
    Published: September 15, 1978
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Fatigue tests were carried out on two kinds of high strength steel and three kinds of surface hardened steel under constant and variable stress amplitudes. The results obtained are summarized as follows;
    (1) On the 1%Cr-Mo steel the completely reversed variable stress amplitude test gives a shorter fatigue life than that estimated from the modified Miner's S-N diagram, but the completely tension variable stress amplitude test gives a longer life.
    (2) On the SNCM8 steel the second stress of no less than 40% of the fatigue limit affects the fatigue life under variable stress amplitude.
    (3) The fatigue behavior of the tufftrided steel changes depending on the kinds of materials or the dimension of specimens under variable stress amplitude.
    (4) On the SCM4 induction hardened or SNC21 carburized steel the scatter of the fatigue lives is large under constant stress amplitude, but their fatigue lives are longer under variable stress amplitude than those estimated from the modified Miner's S-N diagram.
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  • Takao NAKAGAWA, Yasushi IKAI, Hiroaki MIYAMOTO, Takeshi IMAI
    1978 Volume 27 Issue 300 Pages 823-828
    Published: September 15, 1978
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    The fatigue phenomenon of mild steel is characterized by the existence of fatigue limit and coaxing effect. Although many researches have been made from the viewpoint of strain ageing brought about by interstitial solute atoms of carbon and nitrogen, the effect of strain ageing on fatigue limit has not been fully understood.
    The objective of this work is to clarify the effect of strain ageing on the fatigue phenomenon. The experiments were undertaken from the viewpoint that fatigue is a competitive process of two mechanisms of damage and strengthening of the material. Two techniques were applied for this purpose. One was the measurement of the change in solute contents of C and N atoms by internal friction, and the other the reversion of Cottrell atmosphere.
    The experimental results are summarized as follows;
    It was recognized that there occurred strain ageing in the fatigue process. By removing the strain ageing effect, the specimen fractured even under the stress lower than the fatigue limit. Fatigue limit by suppressing the dislocation multiplication in the fatigue process became higher than the original value. It was also observed that, as the time rate of strain ageing increased at higher temperatures, the knee of S-N curve shifted to the smaller number of cycles.
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  • Tsuneshichi TANAKA, Shuji HATTORI
    1978 Volume 27 Issue 300 Pages 829-835
    Published: September 15, 1978
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    The initiation of hysteresis loop of low carbon steels in the fatigue process has been already proposed and developed by the present authors using a model based on the interaction between a dislocation and carbon atoms in the material.
    As one of a series of these researches, the present study is to investigate the effect of temperature on this mechanism. The testing temperature was selected from room temperature to 100°C, and the cylindrical specimens of alminium-killed 0.1% carbon steel were tested under push-pull load with the frequency of 0.2Hz.
    From the experimental results, it is shown that the initiation of the plastic strain amplitude is delayed with an increase in testing temperature in the range from 26 to 80°C. By the theoretical analysis, it is concluded that such behavior is mainly caused by the migration of carbon atoms to dislocation lines from the surrounding matrix during the fatigue process. And the calculations based on this model showed a good agreement with the trend of the experimental results.
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  • Takashi IWAYA, Yukihiko IBUKI
    1978 Volume 27 Issue 300 Pages 836-840
    Published: September 15, 1978
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Three kinds of steels; aluminum-killed, silicon-killed and rimmed steel, were tested. Some of the materials were heat treated before machining; the others, after machining. Tension-compression fatigue test were made on these materials under constant stress and manifold repeated stress at two stress levels.
    Observations were made on the effect of heating treatment and also on the hardness which varied before and after the fatigue test.
    The conclusions obtained are as follows;
    (1) Almost all S-N curves obtained have their knees at 5×106 repetition of stress cycles. The fatigue strength of the low temperature quenched rimmed steel is higher than that of the annealed killed steell.
    (2) The mean values Σn/N based on the Miner's law of alminum-killed and rimmed steels are larger than that of silicon killed steel.
    (3) In the manifold tests at two stress levels, the mean value of the relative hardness before and after testing is larger at the test in hi-lo-hi-lo…type than in lo-hi-lo-hi…type. The mean values Σn/N based on the Miner's law are larger in the hi-lo-hi-lo…type program test than in the lo-hi-to-hi …type.
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  • Motohisa HIROSE, Norihiko HASEGAWA, YOZO KATO
    1978 Volume 27 Issue 300 Pages 841-846
    Published: September 15, 1978
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Precracked specimens of a low temperature quenched rimmed steel were fatigued in rotating bending. Stage-II precracks were introduced by cyclic stressing at a overstress level to the length of 500μm. The specimens were aged under cyclic stressing at understress levels for 106 to 107 cycles (dynamic strain ageing) or statically aged at 100°C for 40 minutes or at room temperature for 24 to 48 hours corresponding to 5×106 to 107 cycles and for 6 weeks (static strain ageing), and then fatigued at the same overstress level as before.
    The main results obtained are summarized as follows:
    (1) Dynamic strain ageing contributes to the decrease in propagation rate but hardly to the increase in critical propagation stress of the precrack.
    (2) Static strain ageing at room temperature for 24 to 48 hours influences both the propagation rate and the critical propagation stress to the same extent as dynamic strain ageing.
    (3) Static strain ageing at room temperature for 6 weeks and at 100°C for 40 minutes makes a greater contribution to the decrease in propagation rate and the increase in critical propagation stress than the above other strain ageing treatments.
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  • Shigeki KOE, Hiroshi NAKAMURA, Toshiyasu TSUNENARI
    1978 Volume 27 Issue 300 Pages 847-852
    Published: September 15, 1978
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    In order to estimate the crack initiation life of notched specimen, it is necessary to obtain the stress or strain at the notch root. For this purpose, Neuber's equation and Stowell's equation have been proposed, but the measured strain at the notch root does not always correspond to the strain calculated with these equations.
    So, some elasto-plastic analysis by FEM on side notched plates were carried out by using various stress-strain relations, and a new empirical equation which can well represent these calculation results is proposed as follows.
    (Kt-1)/(Kσ-1)-1=2.4{Kε-1)/(Kt-1)-1}
    where Kt, Kσ and Kε are the elastic stress concentration factor, the plastic stress concentration factor and the plastic strain concentration factor, respectively.
    Besides, it was shown that the fatigue test results for S15C steel were in good agreement with the fatigue life estimated with this equation.
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  • Makoto KIKUKAWA, Masahiro JONO, Masaharu ADACHI
    1978 Volume 27 Issue 300 Pages 853-858
    Published: September 15, 1978
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    Fatigue crack propagation tests were carried out on a pure iron and a grain oriented silicon iron by using a specially designed testing apparatus in a scanning electron microscope. It was found from the tests on the poly-crystalline pure iron that surface cracks showed different behaviors depending on the grains. So it seems difficult to estimate the fatigue crack propagation mechanism under plane strain condition from observations of the surface crack propagation behaviors.
    On the other hand, in the case of the grain oriented silicon iron nearly plane strain condition could be realized up to the specimen surface by selection of loading axis to the specific orientation of the material. From the sequential observations of crack opening and closure behavior on this material, the mechanism of Mode I type fatigue crack propagation was confirmed to be an alternating slipping-off process at the crack tip apex.
    Quantitative evaluation of a relation between crack tip opening displacement (CTOD) and crack growth length was given by considering the slip direction, the crack tip angle and the amount of rewelding.
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  • Hideo KOBAYASHI, Yukio KAWADA, Hajime NAKAZAWA
    1978 Volume 27 Issue 300 Pages 859-864
    Published: September 15, 1978
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    A fatigue test has been performed on pure titanium using round bar specimens and hollow cylindrical specimens under rotating bending and reversed torsion, respectively. Then the initial stage of fatigue cracking has been investigated by means of electron microfractography and of fracture mechanics.
    The main results obtained are as follows:
    (1) The crystallographic facets of Stage 1 cracking are found in the case of rotating bending but not found in the case of reversed torsion.
    (2) The criterion of transition from Stage 1 to Stage 2 cracking can not be expressed only by the stress intensity factor in the case of rotating bending.
    (3) The transition of macroscopic fracture appearance from shear mode to tensile mode occurs simultaneously together with the change of fractographic appearance from Stage 2a to Stage 2b in the case of reversed torsion. The criterion of transition can be expressed by the stress intensity factor.
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  • Hiroshi MISAWA
    1978 Volume 27 Issue 300 Pages 865-870
    Published: September 15, 1978
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    To clarify the effect of stress amplitude below the fatigue limit on fatigue lives, two step and multi-fold program fatigue tests were carried out and the crack propagation behavior of cyclic stresses was investigated after pre-loading.
    The experimental results are summarized as follows.
    (1) The relation between the crack propagation rate and the crack length can be represented by
    dl/dn=10-(7.99-0.116σ)l(2.26-0.042σ)
    (2) If the crack propagation rate at the stress amplitude below the fatigue limit were estimated by the above relation from the crack propagation rate at the stress amplitude above the fatigue limit and the crack length, the fatigue lives of program fatigue tests at various stress amplitudes above and below the fatigue limit could be calculated. The experimental fatigue lives were compared with the calculated fatigue lives. The fatigue lives calculated by this way agreed with the experimental fatigue lives more exactly than those calculated by Miner's law or modified Miner's law.
    (3) The crack propagation rate in the initial period of the repetition of σ2 was faster than the estimated value, but with increasing the number of cycles of that stress, it became slower than the value estimated by the above equation.
    (4) The crack propagation rate of σ1 was not influenced by pre-loading σ2 when the fatigue crack was propagating at cyclic stress σ2. But when the fatigue crack became the non-propagating crack with icreasing the cyclic numbers of σ2, the crack propagation rate of σ1 was influenced by the preloading and became slower than the estimated value by the above equation.
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  • Ryoichi KOTERAZAWA
    1978 Volume 27 Issue 300 Pages 871-877
    Published: September 15, 1978
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    The effect of periodic overstressing on fatigue crack propagation was studied with circumferentially cracked specimens in rotating bending of low carbon steels (a rimmed steel and an Al-killed steel), a medium carbon steel, a high strength steel and an aluminum alloy. Some tests were conducted also with surface cracked specimens. A very small number of cycles of overstress applied intermittently during a very large number of cycling of under stress below threshold stress intensity Kth caused remarkable acceleration of crack propagation (about or more than one hundred times) in all materials tested except the high strength steel, indicating that Kth loses its physical meaning as the threshold for fatigue crack propagation under such variable stress conditions.
    The acceleration was more remarkable in materials of lower strength. A lower limit seems to exist in the value of understress that causes significant acceleration and the limiting value does not seem to vary appreciably with the strength of the material. Some discussions were made on the design criterion which takes account of the acceleration by understress.
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  • Toshiro YAMADA
    1978 Volume 27 Issue 300 Pages 878-883
    Published: September 15, 1978
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    It is important to predict the fatigue lives and endurance limits of metals under service loads, i. e., complex stress histories. Although the modified Miner's law has been applied sometimes to predict the fatigue lives of metals under service loads in general, it is not adequate to do so accurately and can not predict the endurance limits under service loads. In the present study, a new prediction method for fatigue lives and endurance limits of metals under service loads was developed.
    The fatigue damge FN' produced in the N'-th cycle of stress σ can be expressed as follows: FN' =Aσα·exp(-mσpN'), where Aσα is the basic fatigue damage and exp (-mσpN') represents the change of fatigue damage due to strain aging and other factors, α, A, m and p being material constants. Then the fatigue lives of metals N under service loads can be predicted by solving the equation: ∫N0FN'dN'=1, applying the material constants which can be obtained from the data of S-N curve.
    The fatigue lives of 0.11% C rimmed steel under programmed loading which included stresses lower than the fatigue endurance limit, were predicted by applying the new prediction methods. The material constants α, A, m and p were studied and the method of calculating α and A obtained from the test results through S-N curves was proposed. It was found that the predicted fatigue lives are in good agreement with the tested lives, when the adequate values of m and p are applied.
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  • Satoshi NISHIJIMA, Etsuo TAKEUCHI
    1978 Volume 27 Issue 300 Pages 884-889
    Published: September 15, 1978
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    From view point of obtaining statistical informations on the fatigue strength of welded joints, a series of fatigue tests were carried out under bending stress conditions on the polished smooth and notched base metal specimens and on the butt joint specimens prepared by arc welding with covered electrode. The results were represented as the P-S-N diagrams and discussed by analyzing the distribution of relative strength deviation values from the mean S-N curve of the population.
    The distribution in fatigue strength of the smooth base metal specimens was similar to that in Vickers hardness and skewed from the normal distribution, whereas those of the butt welded specimens were almost normal. The variation coefficient in fatigue strength was evaluated under reversed bending the smooth and notched base metal specimens both as about 2.8%, and for the welded specimens 5.0% under reversed bending and 7.3% under repeated bending. The variation in fatigue strength of the welded specimens was attributed in half part to that in the stress concentration due to the reinforcement. The variation introduced during fatigue crack propagation was sufficiently small compared with that for crack initiation in the base metal specimens.
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  • Shin-ichi TANAKA, Kozo HATSUNO, Shinji YAGUCHI
    1978 Volume 27 Issue 300 Pages 890-894
    Published: September 15, 1978
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    In order to investigate the statistical properties of fatigue strength of car-axle materials, the rotary bending fatigue tests have been carried out on smooth and press-fitted specimens made from the usual car-axle materials (SF55) and the actual car-axles.
    From these test results, the effects of mechanical properties, chemical contents and size on the statistical property of fatigue stength were investigated. Also the effect of a period in service as actual car-axle was investigated. Also, the relation between P-S-N curve of small size specimens and that of actual car-axle was examined, and a method of estimating statistical property of full size parts using the data of small size specimens was discussed.
    The main results obtained are as follows:
    (1) Failure fatigue life under constant stress amplitude is influenced considerably by the mechanical properties and chemical contents such as tensile strength, yield point, Charpy impact value, hardness and Si content, but slightly by the other elements. Fatigue life varies in proportion to the above effective elements.
    (2) The longer the period in service as actual car-axle, the shorter the failure fatigue life under constant stress amplitude is.
    (3) The size effect on the statistical property of failure fatigue life is small.
    (4) The statistical properties of fatigue life of small size press-fitted specimens are similar to those of full size car-axle.
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  • Shigetsune AOYAMA, Mitsufumi ITO, Shoji ASANO
    1978 Volume 27 Issue 300 Pages 895-901
    Published: September 15, 1978
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    The fatigue strength of iron casting is very sensitive to its microstructure, particularly the shape and distribution of graphite, which varies with the section size of casting. In the present study, the effect of section size on the fatigue strength was investigated in a rotating bending test, for two kinds of plain specimens cut from 20mm diameter cast round bars and 250mm cubic castings of flake graphite iron.
    Cast iron products are frequently used with cast skins. Therefore, the effect of surface conditions on the fatigue strength was also investigated. A completely reversed plane bending fatigue test was made for the spheroidal graphite iron plate specimens with shot blasted cast skin, with machined surface and with machined and shot peened surface.
    Furthermore, an attempt was made to examine the possibility of estimating the fatigue strength of the above-mentioned three kinds of iron castings by the method proposed previously. For this purpose, the reduction factor by graphite for the tensile yield strength was determined by the X-ray stress measurement technique and compared with that for the fatigue strength.
    The results obtained are as follows:
    (1) In the rotating bending test, the fatigue strength of 250mm cubic castings was about half of that of 20mm diameter cast round bars. The difference is mainly ascribed to the variations in shape and distribution of graphite.
    (2) In the reversed bending test, the endurance limit of the specimens with shot blasted cast skin was about 30% larger than that of the specimens with machined surface. However, the endurance limit of the latter was increased to the level of the former by the shot peening treatment.
    (3) The reduction factor by graphite for the tensile yield strength agreed mostly well with that for the fatigue strength, for the three kinds of cast irons investigated.
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  • Harumi FURUE, Shoji SHIMAMURA
    1978 Volume 27 Issue 300 Pages 902-907
    Published: September 15, 1978
    Released: June 03, 2009
    JOURNALS FREE ACCESS
    The fatigue properties of plastic materials have been studied for more than fourty years and a considerable amount of data have been accumulated in the past. However, an attempt to utilize the results as design data has not been made.
    In the present study, the past date of plain bending fatigue tests on rigid plastics and plastic composites were summarized, and the mutual correlations between the fatigue strength at 107 cycles and static bending strength, flexural modulus, static tensile strength or glass content in volume were investigated. The results show that the fatigue strength at 107 cycles can be well correlated with elastic modulus. Such correlation is useful for fatigue design of rigid plastics and plastic composites.
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  • 1978 Volume 27 Issue 300 Pages 908-912
    Published: September 15, 1978
    Released: June 03, 2009
    JOURNALS FREE ACCESS
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  • Task Group on Corrosion Testing and Evaluation
    1978 Volume 27 Issue 300 Pages 913-918
    Published: September 15, 1978
    Released: June 03, 2009
    JOURNALS FREE ACCESS
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