Journal of the Society of Materials Science, Japan
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
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Volume 45, Issue 1
Displaying 1-23 of 23 articles from this issue
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  • Overview of the Recent Airplane's Accidents Related to the Fatigue Cracks and Revised (Draft) Fatigue Standards of FAA
    Genkichi FUJIWARA
    1996 Volume 45 Issue 1 Pages 2-8
    Published: January 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.2
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    This article describes the findings of research for some recent transport airplane's accidents related to fatigue cracks. One is a B747SR's accident due to crack initiating at the fastener holes (to say Multiple-Site Damage). The other describes the crash of UAL's DC10-10 (N1819U), in Sioux City, Iowa, U. S. A., on July 19, 1989, which experienced a catastrophic failure of the No. 2 tail-mounted engine during cruise flight. The third explains the in flight separation of the No. 2 engine and engine pylon from B747-100F, shortly after departure from Anchorage International Airport, Anchorage, Alaska, on March 31, 1993. As a result of investigation for B747-100F's accident, National Transportation Safety Board made some important recommendations (One is to amend the design load requirements of Title 14 Code of Federal Regulations Part 25 to consider multiple axis loads encountered during severe turbulence) to the Federal Aviation Administration. Also, current aging airplane service data have identified that there are more cracked airplanes with increasing fleet edge, and possibly several fatigue cracks in some of the cracked airplanes. Especialy, MSD helped focus the attention of the aeronautical field on the problems of operating an aging transport airplanes. Therefore, FAA proposed to rivise the Advisory Circular No. 25·571-1A (Damage tolerance and fatigue evaluation of structure) on 3/5/1986. This article describes one operator's viewpoint on the means to maintain the safety of aircraft structures in consideration of the revised structural fatigue evaluation standards.
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  • Overview of the Recent Airplane's Accidents Related to the Fatigue Cracks and Revised (Draft) Fatigue Standards of FAA
    Genkichi FUJIWARA
    1996 Volume 45 Issue 1 Pages 9-15
    Published: January 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.9
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    This article describes the findings of research for some recent transport airplane's accidents related to fatigue cracks. One is a B747SR's accident due to crack initiating at the fastener holes (to say Multiple-Site Damage). The other describes the crash of UAL's DC10-10 (N1819U), in Sioux City, Iowa, U.S.A., on July 19, 1989, which experienced a catastrophic failure of the No.2 tail-mounted engine during cruise flight. The third explains the in flight separation of the No.2 engine and engine pylon from B747-100F, shortly after departure from Anchorage International Airport, Anchorage, Alaska, on March 31, 1993. As a result of investigation for B747-100F's accident, National Transportation Safety Board made some important recommendations (One is to amend the design load requirements of Title 14 Code of Federal Regulations Part 25 to consider multiple axis loads encountered during severe turbulence) to the Federal Aviation Administration. Also, current aging airplane service data have identified that there are more cracked airplanes with increasing fleet edge, and possibly several fatigue cracks in some of the cracked airplanes. Especialy, MSD helped focus the attention of the aeronautical field on the problems of operating an aging transport airplanes. Therefore, FAA proposed to rivise the Advisory Circular No.25·571-1A (Damage tolerance and fatigue evaluation of structure) on 3/5/1986. This article describes one operator's viewpoint on the means to maintain the safety of aircraft structures in consideration of the revised structural fatigue evaluation standards.
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  • Effects of Artificial Small Defect and Graphite on Torsional Fatigue Strength of Ductile Cast Iron
    Masahiro ENDO
    1996 Volume 45 Issue 1 Pages 16-20
    Published: January 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.16
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    Reversed torsion and rotating bending fatigue tests were performed on JIS FCD400 using both smooth and defect specimens containing an artificial hole whose diameter ranges from 100 to 500μm.
    Although this material has numerous spheroidal graphites in the structure, the effect of interaction between defects on the fatigue limit was so small that the fatigue limit of specimen containing an artificial hole was predicted from √area for the hole and the Vickers hardness of matrix by the equation that was proposed in this study assuming steels with a single defect. The fatigue limit of smooth specimens in torsion was controlled by graphites and the lower bound of the scatter was well predicted substituting the size of the maximum graphite, √areamax, for √area in the equation. The value of √areamax may correspond to the allowable defect size of this material.
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  • Low-Cycle Fatigue Behavior of Notched Low-Carbon Steel Components
    Akihiro MORIMOTO, Atsushi SAITO, Eiichi MATSUMOTO, Jun MATSUSHIMA
    1996 Volume 45 Issue 1 Pages 21-25
    Published: January 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.21
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    Large structures are usually constructed using the conventional low-carbon steel and often contain many kinds of discontinuous cross sections or initial defects. The fatigue cracks commonly initiate at these sites under repeated loadings. So, the estimation of low-cycle fatigue life of the notched components is significantly important in the design of structures.
    In this study, the low-cycle fatigue tests were carried out using the smooth round bar specimens and the notched plate specimens machined from the hot rolled low-carbon steel sheets of SM400A, SM400B and SM490A. After analyzing the experimental data, the estimating method of low-cycle fatigue life of notched specimens was proposed.
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  • Corrosion Fatigue Behavior of Chromium Nitride Coated Steel
    Kazuaki SHIOZAWA, Kou MOTOBAYASHI, Masaru SONOBE
    1996 Volume 45 Issue 1 Pages 26-31
    Published: January 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.26
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    Chromium nitride (CrN) has good properties, such as high hardness, good wear resistance, relatively good adhesion of the film and an attractive color, in addition to corrosion resistance. The superior properties of CrN thin film may be useful to surface improvement of metals. In order to investigate the effect of CrN coating on the corrosion fatigue behavior of metals, cantilever-type rotating bending fatigue tests were carried out in 3% saline solution by using the round-bar specimens of 0.37% carbon steel coated with CrN by a physical vapor deposition method. Obvious improvement of corrosion fatigue strength was observed for the CrN coated specimens, as compared with those without coating. Also, it was observed that the improvement of corrosion fatigue strength depended on the thickness of coated film, because small pores and pinholes in the coating were produced during coating process and these defects decreased with increasing film thickness. The quantitative evaluation of defects in the coating film was made from the current density determined by the electrochemical polarization method. The open pores in the coating acted as a small anode area which accelerated the corrosion of base metal, and the corrosion fatigue strength was controlled by the defect size in the coating.
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  • Fatigue Behavior of Stainless Steel Coated with Plasma-Sprayed Ceramics in Physiological Saline Solution
    Tadaaki SATAKE, Mikio SUGANO, Jun KISIMOTO, Hirotaka MASAKI
    1996 Volume 45 Issue 1 Pages 32-37
    Published: January 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.32
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    To evaluate the potential of prosthetic application, the SUS316L stainless steel rod specimen coated with plasma-sprayed Al2O3 deposits has been fatigued in a physiological saline solution (0.9% NaCl solution). Fatigue tests were conducted in push-pull loading under the stress ratio of R=-1 and frequency of 2Hz. In the Al2O3 sprayed specimen, fatigue cracks preferentially originated from craters which were formed on the surface of substrate metal by grit blasting, and extended into the bulk of substrate metal. It was considered that a main fatigue crack had grown into plasma-sprayed coating when the coating was unable to accommodate its deformability to the largest displacement of crack opening at the substrate metal surface. It is said that the plasma-sprayed coating can keep the substrate metal from corrosive attack during the initial growth stage of fatigue crack subsequent to its initiation. Microfractography showed that the stage IIb in the fatigue crack growth rate diagram, characterized by more than 50 percent fatigue striation mode in the fraction of fracture surface, appeared in the higher region of ΔK values for the Al2O3 sprayed specimen. The crack growth rate in the stage IIb was lower in the Al2O3 sprayed specimen than in the non-sprayed one. This was thought to be responsible for the prolongation of fatigue life in the Al2O3 sprayed specimen.
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  • Effect of Thermal History on Tensile and Fatigue Crack Growth Properties of a Cryogenic Austenitic Stainless Steel Forged at Room and Liquid Helium Temperatures
    Shinji KONOSU, Tomohiro KISHIRO, Ogi IVANO, Yoshihiko NUNOYA, Hideo NA ...
    1996 Volume 45 Issue 1 Pages 38-42
    Published: January 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.38
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    By using forging of a newly developed austenitic stainless steel (12Cr-12Ni-10Mn-5Mo-0.2N), a candidate material for the support structure of superconducting magnets for thermonuclear fusion reactors, the effects of a sensitizing heat treatment (24 hours at 650°C, followed by water quenching) on tensile and fatigue crack growth properties (crack closure behavior) at room and liquid helium temperatures were clarified. As a result, it has been found that although the sensitizing heat treatment has virtually no effect on both tensile and fatigue crack growth properties at room temperature, a decrease in tensile total elongation and an increase in fatigue crack growth rate relative to the effective stress intensity factor range due to such heat treatment are evident at liquid helium temperature. This is believed to be due to the difference in microscopic cracking path. Fracture occurs transgranularly in a solution treated material, whereas fracture occurs mainly along the grain boundaries in a sensitizing heat treated material. Furthermore, it has been ascertained that, at liquid helium temperature, the fracture surface profiles of fatigue cracks are much more serrated and the crack-opening load increases, due to sensitizing heat treatment.
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  • Effect of Shot Peening on Fatigue Strength of Ti-6Al-4V Alloy at Elevated Temperatures
    Yozo KATO, Shinzaburo TAKAFUJI, Masaki KIRIYAMA
    1996 Volume 45 Issue 1 Pages 43-47
    Published: January 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.43
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    (1) The fatigue strength of the unpeened specimens of Ti-6Al-4V alloy was found to be 490MPa, 430MPa, 410MPa and 440MPa at 20°C, 250°C, 350°C and 450°C, respectively. The respective values for the shot peened specimens were 620MPa, 520MPa, 440MPa and 260MPa. The fatigue strength was definitely increased by shot peening at 20°C, 250°C and 350°C, and the increments were about 27%, 21% and 7%, respectively. The fatigue strength, however, was remarkably decreased by shot peening at 450°C, and its decrement reached about 41%.
    (2) The fatigue strength of the specimen shot-peened and then electro-polished was 470MPa at 450°C. The fatigue strength greatly increased from 260MPa to 470MPa after polishing. The value of 470MPa is comparable to 460MPa of the fatigue strength of the unpeened specimen.
    The decrease in fatigue strength due to shot peening at 450°C may be explained as follows. The compressive residual stress in the near-surface region induced by shot peening disappear during fatigue cycling at 450°C, but the great surface roughness due to shot peening still remains, which reduce the fatigue strength of the shot peened specimen.
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  • Observation of Rolling Contact Fatigue Damage of Polycarbonate Specimen
    Chobin MAKABE, Takeshi SUZUKI, Hideo YARA, Tateki YAFUSO
    1996 Volume 45 Issue 1 Pages 48-54
    Published: January 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.48
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    Crack initiation and growth in polycarbonate specimens under lubricated rolling contact loading were observed with a monitor microscope, and their failure mechanisms were investigated. When a fatigue crack initiated at the contact surface, the crack tip lay in the plane of the maximum shear stress in the first stage of crack growth. Next it turned the direction perpendicular to the maximum principal stress direction. In this case, pitting type failure occurred due to the crack extension. Butterfly type failure occurred after secondary crack extension due to the concentration of shear stress around the cracked region. The shear mode growth of cracks was observed when the cracks initiated at the side surface of the specimen. In this case, flaking type failure occurred. It was found that the failure mechanism of the present specimen correlated well with the crack extension mode and different mechanisms were observed in the formation of pitting, flaking and butterfly patterns.
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  • Correlation between Microstructure and Fatigue Behavior of Silicon Nitride Ceramics
    Hiroshi HOHJO, Akira YAMADA, Katsushi SARUKI, Nobuo KAMIYA
    1996 Volume 45 Issue 1 Pages 55-59
    Published: January 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.55
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    Microstructures of seven kinds of silicon nitride ceramics were quantified by electron cyclotron resonance plasma etching and sequential image analysis. And the correlations between microstructure and fracture toughness, intrinsic bending strength or cyclic fatigue crack growth exponent were estimated by using multiple regression analysis.
    The characterized microstructure parameters, composed of the mode and distribution of grain size, the fraction of needle-like grains and the amount of additives, were correlated to the experimental mechanical properties with high correlation coefficients. For improving the fracture toughness, intrinsic bending strength and cyclic fatigue crack growth exponent of silicon nitride ceramics at the same time, it may be effective to increase the needle-like grains, according to the weight factors of microstructure constituents.
    Fatigue crack growth passages in the materials with highest and lowest fatigue crack growth exponents were analyzed. As a result, in the material with a high exponent, crack arrest and bridging were more often caused by the intergranular fracture of needle-like grains. A larger amount of additives and a broader distribution of grain size make crack arrest and bridging tend to occur more often.
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  • Torsional Fatigue of SiC Whisker or SiC Particulate Reinforced 6061 Aluminum Alloys
    Hitoshi ISHII, Atsushi YANO, Keiichiro TOHGO
    1996 Volume 45 Issue 1 Pages 60-63
    Published: January 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.60
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    Torsional fatigue tests of SiC whisker or SiC particulate reinforced 6061-T6 aluminum matrix composite (SiCw/Al or SiCp/Al), fabricated by a high pressure infiltration method, were performed. From a comparison with the properties of the monolithic aluminum alloy, it became clear that the torsional fatigue strength of 6061Al alloy was increased by reinforcing either with SiC whiskers or SiC particulates. Unlike strong orientation dependency of the tensile strength or fatigue strength in rotating bending, no orientation dependency was observed in the torsional fatigue strength of the SiCw/Al with highly aligned whiskers. In the SiCp/Al, cracks both parallel and transverse to the axial direction of test piece were observed. On the other hand, cracks in the SiCw/Al were always formed parallel to the direction of aligned whiskers. That is, cracks parallel to the axis were observed in the L oriented specimen whose axis was parallel to the direction of aligned whiskers and cracks transverse to the axis were observed in the T oriented specimen whose axis was transverse to the aligned whiskers. Importance of shear deformation in initiating fatigue cracks was clarified.
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  • Fatigue Crack Growth Behavior of Alumina Short Fiber Reinforced Aluminum Alloy at Room and Higher Temperatures
    Tsuneshichi TANAKA, Hideaki NAKAYAMA, Shigeru YAMAMOTO, Yukiyoshi KOBA ...
    1996 Volume 45 Issue 1 Pages 64-71
    Published: January 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.64
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    In order to clarify the fatigue crack growth mechanism of an alumina short fiber reinforced aluminum alloy (FRM), fatigue crack growth tests were carried out at several stress ratios on the center cracked tension (CCT) specimens at room and elevated temperatures. Aluminum alloy, A6061-T6 was also used as a reference material. Comparison of fatigue crack growth rate curves determined for A6061-T6 and FRM specimens indicated that the effect of temperature on the crack growth rate curves was much smaller for FRM than that for A6061, and the crack growth property of FRM was superior to A6061 in the region of low crack growth rate including the threshold, when the comparison was made on Kmax and ΔK. By estimating the values of ΔKeff, it was shown that the fatigue crack growth rates of A6061 and FRM at each temperature were governed by ΔKeff and KmaxαΔKeff(1-α), respectively. Moreover, the detailed evaluation indicated that the fatigue crack growth rates of A6061 and FRM at different stress ratios and temperatures could be expressed by introducing new parameters, excepting in the threshold region, as follows:
    da/dN=C1{UR(1-R)/UR=0.1Kmax(Eσ0.2)-1/2}m1 for A6061
    da/dN=C2{{UR(1-R)/UR=0.1}(1-α)Kmax(Eσ0.2)-1/2}m2 for FRM
    where R is the stress ratio, UR is the crack opening ratio at stress ratio R, UR=0.1 is the value of U at R=0.1, E and σ0.2 are Young's modulus and 0.2% proof stress at each temperature, and C1, C2, m1 and m2 are material constants.
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  • Effects of Short Fiber Reinforcement and Mean Stress on Tensile Fatigue Strength Characteristics of Polyethersulfone
    Harumi FURUE, Katsunobu NONAKA
    1996 Volume 45 Issue 1 Pages 72-78
    Published: January 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.72
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    In order to characterize the fatigue strength of injection moulded advanced thermoplastics, such as Polyethersulfone (PES), short glass fiber reinforced PES and short carbon fiber reinforced PES, fatigue tests were conducted under tension-tension cyclic loading (stress ratio, R=0.1-0.7) at 23±1°C and 50±5%RH. The effects of repeated stress amplitude, mean stress, characteristic of matrix and the kind of reinforced short fibers on the fatigue strength were investigated. The behavior of fatigue fracture in short fiber reinforced thermoplastics and matrix resin was also investigated on the basis of the fractographic examination of fatigue fracture surface.
    The results are summarized as follows. (1) The influences of repeated stress amplitude and mean stress on the fatigue characteristic of PES series were revealed. (2) It was found that the effect of short fiber reinforcement on fatigue strength characteristic is high, and carbon fiber is more effective than glass fiber. (3) The short fiber reinforcement of those materials was also discussed on the basis of the fractographic examination.
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  • Development of Fatigue Crack Monitoring System
    Kengo MORINO, Chiaki HIWA, Yasushi IKAI
    1996 Volume 45 Issue 1 Pages 79-84
    Published: January 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.79
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    A new method for monitoring fatigue life under service load is proposed and examined experimentally. Through FEM strain analysis around a crack under stress, the best positions to attach strain-gages are chosen, where one gage is put parallel-wise close to a crack and the other is put away from the crack. By observing the product of two gage outputs, the crack propagation prosess is monitored, since the signal changes from positive to negative corresponding to the crack length, independent of stress amplitude. An electrical circuit is designed, and examined under fatigue tests. The circuit proved to be successful to detect a critical fatigue crack in the range from 72 to 99% of the fatigue life depending on the distance between the crack and the gage. The circuit costs about one tenth of a strain meter.
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  • Sizing of Fatigue Crack on Free Surface by Use of Bottom Reflected Tip Echo
    Kasaburo HARUMI, Masanori UCHIDA, Junnichi OOSHIMA, Yasuhiro AIKAWA
    1996 Volume 45 Issue 1 Pages 85-88
    Published: January 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.85
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    The precise sizing technique of a fatigue crack height was explained in the previous paper. The accuracy of this method is about 0.2mm, about 1/10th of that of the conventional ultrasonic testing, and it will be effective for fracture mechanics. However, the ultrasonic flaw-detector used was HITACH DT-2200 which is not commercially available. So, a request has been received to use an ultrasonic digital equipment available in the market. In the present study, such an equipment was tried and the accurate results were obtained from the original unrectified wave shape. Since it is a easy technique even for the fracture mechanic engineers, this new technique will be useful for fatigue crack growth tests.
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  • In-situ Synthesis of Cu-based Composites by Combustion Reaction Using Cu-Zr-BN Powder Mixtures
    Hiroshi TSUDA, Hiroshi MABUCHI, Yutaka NAKAYAMA
    1996 Volume 45 Issue 1 Pages 89-93
    Published: January 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.89
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    The Cu-based composites are excellent candidates for applications that require high strength and good electrical conductivity. In the present study, using Cu-Zr-BN powder mixtures, Cu-matrix ceramic composites were made by the combustion reaction process, following sintering. As a result, Cu and Zr powders with BN powder reacted exothermically, and in-situ formed a mixture product which had a fine distribution of ZrB2 and ZrN particles in the Cu matrix. It was found that the composite materials obtained have good conductivity and high strength at both room and elevated temperatures. Therefore, the processing technique in the present investigation is of interest as a new process to make metal matrix composite materials.
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  • Effects of Cement Composition and Silica Content on Microstructure and Compressive Strength of Autoclaved Mortar
    Toshiyuki TAKAHASHI, Hiroyuki NISHITOMI, Seishi GOTO
    1996 Volume 45 Issue 1 Pages 94-100
    Published: January 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.94
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    Effects of cement composition and silica content on the microstructure and compressive strength of autoclaved mortar with silica powder were studied. The strength of autoclaved mortars prepared by mixing with portland cement and silica powder with low water cement ratio (W/S=0.25) was affected by the amount of silica powder. The maximum strength was obtained for the mortar with silica content where calcium hydroxide was completely consumed by the reaction with silica powder added. The correlation between formation of tobermorite and compressive strength of autocraved mortar was not clear. The excessive addition of silica powder resulted in the formation of gap between the silica particles and matrix, with decreasing in the strength of mortars. A correlation between pore volume and compressive strength was obtained when these gap did not exist.
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  • Characteristics of Bleeding, Freeze-Thaw Resistance and Watertightness of Concrete with Ferro-Nickel Slag Fine Aggregates
    Kazuo TOGAWA, Masami SHOYA, Katsuro KOKUBU
    1996 Volume 45 Issue 1 Pages 101-109
    Published: January 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.101
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    Many reports have been published on various properties of concrete with ferro-nickel slag fine aggregates, and it has been pointed out that the concrete with such aggregate showed the nearly same strength as that of normal concrete. A total of five ferro-nickel slag fine aggregates were examined in this study. The experiments were conducted by fixing the volumetric mixture ratio of slag 50%, except crushed air granulated slag used for single fine aggregates, to investigate the efficiency of chemical admixtures and the water demand in the ferro-nickel slag concrete as compared with those of natural sand concrete. In addition, the bleeding properties of those concretes were fully investigated. The reduction of unit water content, by applying a high range water reducer, could be expected to the same degree as that of normal concrete, which also resulted in the decrease of bleeding. The additions of blastfurnace slag, silica fume and lime stone powder pronouncedly improved the compressive strength and the bleeding of ferro-nickel slag concrete. And then, the freeze-thaw resistance was improved by the addition of lime stone powder, but hardly improved by the addition of silica fume. It can be considered that the watertightness of ferro-nickel slag concretes is the same as that of natural sand concrete.
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  • Physical Meaning of Creep Damage Parameters Evaluated from Distribution of Grain Boundary Cavities on Cross-Section
    Naoya TADA, Takayuki KITAMURA, Ryuichi OHTANI
    1996 Volume 45 Issue 1 Pages 110-117
    Published: January 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.110
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    In order to grasp the creep damage of polycrystalline heat-resisting alloys, creep damage parameters observed on the cross-section, such as the area fraction of cavities. A-parameter, fraction of cavities on grain boundary lines and the number of cavities in unit area, have frequently been used. Although they include the information of creep cavities, it is vague what they really represent in the spatial distribution of cavities. In this paper, the physical meaning of these parameters is investigated using a model distribution of cavities, and the dependences of parameters on the radius of cavities, on the number of cavities on each grain boundary facet, and on grain diameter are discussed.
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  • Thermal Stress and Strength Reliability of Heater for Cathode Ray Tube
    Toshiaki ARATO, Hideki SHINOHARA, Hiroshi MIYATA, Nobuyuki KOGANEZAWA, ...
    1996 Volume 45 Issue 1 Pages 118-124
    Published: January 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.118
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    CRT heater has a complex structure which is composed tungsten double spiral coil and Al2O3 insulating film on the coil surface. For the strength evaluation of the heater, thermal stress under operating conditions was analyzed, and its material strength was experimentally obtained.
    Simplified analysis procedure by the finite element method is effective for a complex structure such as CRT heater. A simplified model was developed by keeping the same structural stiffness, which was useful for calculating the overall temperature distribution and deformation behavior of the heater. Thermal stress, which is an important factor in strength evaluation, was obtained by using a precise model of local structure. The analytical results showed that the highest temperature was attained in 20 seconds after current was turned on, and the uniform temperature distribution was found in the cross section of the heater. The maximum thermal stress of about 210MPa was attained and then it sharply decreased from the inside to the outside wall of the heater. The thermal stress obtained by the analysis and the strength of Al2O3 insulating film and tungsten wire determined experimentally were compared to evaluate the strength reliability of the heater.
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  • Development of Simple Thermal Fatigue Test Method Using Low-Thermal Expansion Restraining Holders
    Hajime IKUNO, Shogo IWANAGA, Yoji AWANO
    1996 Volume 45 Issue 1 Pages 125-130
    Published: January 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.125
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    A new test method of evaluating the thermal fatigue resistance of aluminum alloy has been developed. In this test method, a small test piece was clamped between a pair of holders consisting of low-thermal expansion materials, mainly Incoloy 904 superalloy. The test piece was alternately heated and cooled with constraining longitudinal thermal expansion. The compressive and tensile strains were generated during the heating and cooling periods, respectively. The total strain range was determined by the thermal expansion of the test piece and holders, and by the size and shape of the test piece. The initial strain could be controlled by changing the clamping temperature of the test piece. The temperature distribution along the test piece was within 5K. The total strain range was almost constant during the test in spite of softening of the material. Thermal stress and strain were quantitatively estimated using high-temperature strain gages by compensating the temperature dependence of the gage factor and elastic modulus of holders. By using this test method, it has been quantitatively clarified that decreasing total strain range and reducing porosity increased the thermal fatigue lives of JIS AC2B aluminum alloy castings.
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  • Measurement of Stress Intensity Factor under Mixed-Mode Loading by the Method of Caustics
    Yukio HIROSE, Masayuki SHOZU, Yuichi KAWAGISHI, Toshihiko SASAKI, Ken- ...
    1996 Volume 45 Issue 1 Pages 131-136
    Published: January 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.131
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    As one of optical methods, the method of caustics is useful for determining the stress intensity factor. In this paper, the method of caustics was applied to the specimens with an oblique crack. The results obtained are summarized as follows: (1) The method of caustics is a useful technique to determine the stress intensity factors KI and KII separately under mixed-mode loading. (2) The existing theory used for measurement of this method is effective only when the initial curve radius r0 is larger than the minimum initial curve radius r0min determined in this study. It is recognized that the value of r0min decreases as the ratio of KII to KI increases. (3) The 3-D stress field exists in the vicinity of crack tip, while the state of stress is nearly planestrain deformation in the case of mode I loading. In the case of mixed-mode loading, the state of stress is approximately plane-stress deformation as the ratio of KII to KI increases. (4) A correction is proposed to obtain the values of K from caustic images in the case of r0<r0min.
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  • Computer Simulation on Fracture of Engineering Materials at High Temperature
    III: Total and/or Remaining Life Assessment of Structural Material
    Kazunari FUJIYAMA
    1996 Volume 45 Issue 1 Pages 137-142
    Published: January 15, 1996
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.45.137
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