1997 Fiscal Year Final Research Report Summary
A STUDY ON IMPACT FATIGUE OF HIGH-STRENGTH STEEL
| Project/Area Number |
08651099
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
船舶工学
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| Research Institution | OSAKA PREFECTURE UNIVERSITY |
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Principal Investigator |
KITAURA Ken-ichi OSAKA PREFECTURE UNIVERSITY ESSOR College of ENGINEERING ASSISTANT PROFESSOR, 工学部, 講師 (00081399)
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| Project Period (FY) |
1996 – 1997
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| Keywords | HIGH-STRENGTH STEEL / IMPACT FATIGUE STRENGTH / TRANSFORMATION BEHAVIOR / SMOOTH SPECIMEN / NOTCH SPECIMEN |
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| Research Abstract |
THE PUROPOSE OF THIS STUDY IS TO TRANSFORMATION BEHAVIOR AND FATIGUE STRENGTH OF IMPACT FATIGUE OF FOUR KINDS OF THE CIRCULAR BAR SPECIMENS OF HIGH-STRENGTH STEEL
FROM EXPERIMMENTAL RESULTS,THE CONCLUSIONS ARE SUMMARIZED AS FOLLOWS :
1) THE PROCESS OF LOE-CYCLE FRACTURE OF THE SMOOTH SPECIMEN AND NOTCH SPECIMEN (STRESS CONCENTRATION FACTOR Kt=1.7) OF MATERIALS CREEPTYPE AND CYCLIC BEHAVIOUR OF PERMANENT STRAIN epsilon IS ALMOST SIMILAR TO ORDINARY LOW-CYCLE FATIGUE BEHAVIOUR.
ITS PROCESS IS DIVIDED INTO THREE STAGES WHICH ARE INITIAL CREEP STAGE,CONSTANT CREEP STRAIN RATE (DELTAepsilon_c=depsilon/dN) STAGE AND ACCELERATIVE CREEP STAGE.
2) THE RELATION BETWEEN PLASTICITY STRAIN RATE DELTAepsilon_c AND DELTAepsilon_c IS GIVEN BY
DELTAepsilon_c=DELTAepsilon_c/T(a)
WHERE T IS THE DURATION OF MAXIMUM STRESS
3) THE RELATION BETWEEN DELTAepsilonc AND IMPACT TENSILE STREES sigma IS EXPRESSED BY
sigma/sigma_B =S (DELTAepsilon_c/epsilon_f)^<beta> (b)
WHERE sigma_B IS ULTIMATE STRENGTH OF THE MATERIAL,epsilon_f IS epsilon AT THE TIME OF FRACTURE UNDER STATIC TENSILE TEST AND beta AND S ARE EXPERIMENTAL CONSTANTS.
4) THE RELATION BETWEEN DELTAepsilon_c AND IMPACT FATIGUE LIFE N_f IS EXPRESSED BY
(DELTAepsilon_c/epsilon_f)N_f^m=C (c)
WHERE m AND C ARE EXPERIMENTAL CONSTANTS.
5) THE RELATION BETWEEN IMPACT TENSILE STRESS sigma AND CUMULATIVE DURATION OF MAXIMUM STRESS (N_f・T) IS APPROXIMATELY EXPRESSED BY
sigma(N_f・T)^n=D (d)
WHERE n AND D ARE EXPERIMENTAL CONSTANTS.
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