Crack-healing behavior of structural ceramics under the conditions of tensile stresses and high temperatures
| Project/Area Number |
15360047
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Materials/Mechanics of materials
|
|---|
| Research Institution | Yokohama National University |
|---|
Principal Investigator |
ANDO Kotoji Yokohama National University, Energy & Safety Engineering, Professor, 大学院・工学研究院, 教授 (40017992)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
TAKAHASHI Koji Yokohama National University, Energy & Safety Engineering, Associate Professor, 大学院・工学研究院, 助教授 (90334630)
NAKAO Wataru Yokohama National University, Energy & Safety Engineering, Research Assistant, 大学院・工学研究院, 助手 (60361870)
|
|---|
| Project Period (FY) |
2003 – 2004
|
| Project Status |
Completed (Fiscal Year 2004)
|
| Budget Amount *help |
¥14,500,000 (Direct Cost: ¥14,500,000)
Fiscal Year 2004: ¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 2003: ¥12,500,000 (Direct Cost: ¥12,500,000)
|
|---|
| Keywords | Crack-healing / Ceramics / Silicon nitride / Alumina / Mullite / Bending strength / Fatigue strength / Stress intensity factor |
|---|
| Research Abstract |
In this study, Si_3N_4/SiC, alumina/SiC and mullite/SiC composites having excellent crack-healing ability were selected to be test materials. Being introduced a surface-crack of 100 μm, they were then carried out the crack-healing treatment at elevated temperatures raging from 800 to 1200℃ to be applied tensile stress. Based on the strength of the specimens crack-healed under stress, crack-healing behaviors under stress were investigated. From the obtained results, the following conclusions were derived.
1.The heat-treated specimens have same strength as smooth specimens. The cracked specimens could crack-healed under the tensile stress that is 70 to 80% strength of the cracked specimens. The specimens crack-healed under stress had the same strength as the heat-treated smooth specimen at the crack-healed temperature. Moreover, the crack-healed part had enough high strength, because fracture initiation was mostly outside the crack-healed part.
2.The critical condition to be able to heal the pre-crack was estimated from the equation of the stress intensity factor expressed by Newman-Raju and the stress intensity factor of the residual stress for every specimen.
3.The specimens crack-healed under static and cyclic stresses had enough high static and cyclic fatigue strengths at the crack-healing temperature. These values corresponded to 70-80% fracture strength of the crack-healed specimens.
Based on the above conclusions, it is confirmed that Si_3N_4/SiC, alumina/SiC and mullite/SiC composites used in this study can heal cracks initiated in service if the temperature, stress and atmosphere conditions were adjusted.
|
Report
(3 results)
Research Products
(25 results)
