T. Adachi

Ishinomaki Senshu University, Ishinomachi, Miyagi, Japan

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Publications (5)2.66 Total impact

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    ABSTRACT: A testing method under creep-fatigue interaction conditions has been proposed as the ASTM standard E2714-09. In accordance with the ASTM standard, round bar smooth specimens have been recommended as a testing specimen. Additionally, creep-fatigue crack initiation and growth life are usually defined as the attainment of a specific rate of decrease in the maximum tensile stress or the modulus of elasticity ratios. However, these criterions of crack initiation and growth life on ASTM standard are not characterized in terms of physical crack size. In this study, the creep-fatigue crack initiation and growth tests for P92 were conducted using circular notched round bar specimens. An attempt is made to measure the crack length during the tests by the direct current potential drop method, which results in the establishment of a high accuracy crack length measurement. Additionally, the life of creep-fatigue crack growth was characterized by linear cumulative damage law combined with the Qconcept which has been proposed as fracture parameter to describe the life of creep crack growth.
    Journal of ASTM International 01/2012; 9(1):103956. DOI:10.1520/JAI103956
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    ABSTRACT: In components under static creep loading condition, the multiaxial stress fields appear due to the plastic constraint and they produce a more brittle type cracking behavior. From a practical standpoint, the characterizations of creep crack growth rates under the multiaxial stress field are important to improve the methods for creep life extension. In this paper, creep crack growth tests were conducted using round bar specimens with sharp circular notches for tungsten-added 12%Cr ferritic heat-resistant steel (W12%Cr steel), and the effect of multiaxiality on creep ductility and creep crack growth rate were investigated. Furthermore, three-dimensional elastic-plastic creep finite element analyses were conducted to clarify the effect of multiaxiality on creep crack growth.
    Journal of Engineering Materials and Technology 01/2009; 131(1). DOI:10.1115/1.3026544 · 0.96 Impact Factor
  • A. T. · Jr Yokobori · R. Sugiura · M. Tabuchi · A. Fuji · T. Adachi · T. Yokobori ·
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    ABSTRACT: A circular notched round bar specimen produces multi-axial stress field when uni-axial stress is applied in the axial direction. This stress field is produced in practical component structure. Therefore the characterization of creep crack growth rate under this condition is important for practical use. In this paper, developed 12Cr ferritic heat resistant steel was noticed. High temperature creep crack growth tests were conducted for a circular notched specimen for 12Cr ferritic heat resistant steel. And in order to investigate multi-axial stress state of a circular notched specimen, we have conducted 3D FEM analysis. The stress multiaxiality of a circular notched specimen increased as compare with that of CT specimen. Q* parameter which predicts creep crack growth rate is derived for this specimen. On the bases of this Q* parameter, the algorithm of predicting the life of creep growth is proposed.
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    ABSTRACT: Using a round bar circular notched specimen for Cr-Mo-V steel and the proposed equation predicting crack length on the basis of electric potential drop method, the creep crack growth tests were previously conducted to investigate the effect of multi-axial stress on creep crack growth rate (CCGR). In this paper, more detailed experiments and analyses on the creep crack growth were conducted and the Q* parameter which characterizes CCGR for this circular notched specimen was derived. Furthermore, using the Q* parameter, the prediction law of creep crack growth life was also derived.
    Materials at High Temperatures 05/2004; 21(2):95-100. DOI:10.3184/096034004782749962 · 0.42 Impact Factor
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    ABSTRACT: It is important to evaluate the effect of multiaxial stress conditions on initiation and growth of creep cracks, when the laboratory data are subsequently applied to structural components under the same or similar stress state. The round robin tests of creep crack growth using circular notched specimens of 1CrMoV steel at 538 and 594 °C and 12CrWCoB steel at 650 °C were conducted by the Japanese VAMAS TWA25 group. The effect of notch depth and specimen size, i.e. stress multiaxiality on crack growth properties was investigated. The test procedure including criteria for crack length measurement by electric potential drop was established. The circular notched specimens fractured intergranularly and showed different crack growth behaviour from that of a CT specimen due to the multiaxial stress field. The creep crack growth rate for the same C* value increased as the ratio of the notch depth to specimen diameter, i.e. stress multiaxiality increased. The Q* evaluation method based on the thermally activated process can also be applied to the circular notched specimen.
    International Journal of Pressure Vessels and Piping 07/2003; 80(7):417-425. DOI:10.1016/S0308-0161(03)00096-6 · 1.28 Impact Factor