1999 Fiscal Year Final Research Report Summary
Crack progress characteristic of steel in air and corrosive environment
| Project/Area Number |
09450178
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
構造工学・地震工学
|
|---|
| Research Institution | Daido Institute of Technology |
|---|
Principal Investigator |
KOTOGUCHI Hisao Daido Institute of Technology,Engineering, Professor, 工学部, 教授 (60047305)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
MIKI Toshihiro Daido Institute of Technology,Engineering, Professor, 工学部, 教授 (90137175)
MIZUSAWA Tomisaku Daido Institute of Technology,Engineering, Professor, 工学部, 教授 (60113081)
|
|---|
| Project Period (FY) |
1997 – 1999
|
| Keywords | Fracture mechanics / Crack progress / Corrosive environment / Fluctuating load / 疲労破面 |
|---|
| Research Abstract |
3)Crack progress characteristic of two stage fluctuating load (1) The crack opening and closing stress at an excessive load at the fluctuating load decreases compared with that of the constant load examination. (2) That is, the crack opening and closing stress at a high-level load is ruled by the correspond stress at a low-level load. (3) At the fluctuating load, there are a lot of progressing cracks of the crystal grain field compared with the constant load. This could be confirmed from the SEM observation.
2)Micro-rack behavior of steel under salt water environment (1) The different of the load level remarkably influenced the crack progress behavior under the salt-water environment. (2) The micro-crack area does not exist under the corrosive environment when the load is small either. (3) The crack generation time is controlled by the stress condition under the salt-water environment , the crack progress driving force accounts for 85% of the full load. On the other hand, it was about 75% under an atmospheric environment. That is, the crack growth rate becomes early under the salt-water environment.
The research results are as follows:
1) Crack progress characteristic of single and both sides' amplitude (1) When stress ratio R is R>O region, the crack growth rate quickens because the crack progress driving force increases as R increases. (2) For stress ratio<O region,the crack opening and closing stress is corresponding to a neutral stress of the load. (3) All amplitudes in the tension side work as crack progress driving force. (4) There is a straight-line relation between the value of the crack opening and closing stress/the total amplitude stress and the stress ratio R.
|
