| Project/Area Number |
60550047
|
|---|
| Research Category |
Grant-in-Aid for General Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Research Field |
機械材料工学
|
|---|
| Research Institution | The University of Electro-Communications |
|---|
Principal Investigator |
ICHIKAWA Masahiro The University of Electro-Communications, 電気通信学部, 教授 (80017334)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
TAKAMATSU Tohru The University of Electro-Communications, 電気通信学部, 助手 (00106890)
AKITA Satoshi The University of Electro-Communications, 電気通信学部, 講師 (60017390)
|
|---|
| Project Period (FY) |
1985 – 1986
|
| Project Status |
Completed (Fiscal Year 1986)
|
| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1986: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1985: ¥1,500,000 (Direct Cost: ¥1,500,000)
|
|---|
| Keywords | Fatigue Crack Growth Rate / Constant <DELTA> K Test / Electric Potential Method / Statistical Variability / 信頼性工学 |
|---|
| Research Abstract |
The purpose of this investigation is to clarify <DELTA> K dependence of variability of the fatigue crack growth rate da/dN by conducting statistical fatigue crack growth tests under the condition of constant <DELTA> K, and to estabilish the probabilistic formulation of da/dN, where <DELTA> K is the stress intensity range. The condition of constant <DELTA> K was attained using the contoured double cantilever beam specimen. The material used was the high strength steel HT60. 4 to 6 specimens were tested at each of six levels of <DELTA> K. In all 31 specimens were tested. da/dN was measured using DC electric potential method. In order to automize measurement and data processing, an automatic crack length measurement system using micro-computer was developed. Various efforts were made to attain high accuracy of measurement. For obtaining an effective method for analysis of the experimental data under constant <DELTA> K, the privious data under the condition of increasing <DELTA> K were reanalysed. The analysis showed that it was appropriate to regard variability of da/dN as composed of the two components : inter-specimen variability and intra-specimen variability. Next, the experimental data under constant <DELTA> K was analysed. First, variability of da/dN was decomposed into inter-specimen variabity and intraspecimen variabity using the method of analysis of variance. It was found that variability of da/dN under constant <DELTA> K was also composed of the above two components. Then, <DELTA> K dependence of these two components was examined. Neither inter-specimen variability nor intra-specimen variabity showed clear dependence on <DELTA> K, and thus, both the components could be regarded as consatnt independent of <DELTA> K. From the above result, it is concluded that an appropriate probabilitistic formulation of da/dN is to randomize C and to treat m as constant, when Paris's law da/dN = C( <DELTA> K)m is applied at each point in materials.
|
