GB/T 38822-2020 in English
VALIDMetallic materials- Creep-fatigue test method
- Issued on:2020-06-02
- Implemented on:2020-12-01
- File Format:PDF
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《GB/T 38822-2020金属材料 蠕变-疲劳试验方法》由TC183（全国钢标准化技术委员会）归口，TC183SC4（全国钢标准化技术委员会力学及工艺性能试验方法分会）执行，主管部门为中国钢铁工业协会。
Introduction
Standard Background and Technology Evolution
With the increasing reliability requirements for high-temperature materials in fields such as nuclear power and aviation, creep-fatigue interaction research has become key. GB/T 38822-2020 systematically established a composite damage test standard system for the first time based on the integration of GB/T 2039-2012 creep test and GB/T 15248-2008 fatigue test methods.
Core term definitions
| Terms | Definition | Measurement method |
|---|---|---|
| Dwelling time | The period of time during which the force/strain remains constant | Timer recording |
| Inelastic strain range | The sum of plastic strain and creep strain | Extensometer measurement |
| Crack formation | The process of visible crack initiation in the specimen | Stress drop method determination |
Key requirements for test equipment
Based on class=instrument>electronic testing machine as an example, the following must be met:
- Force control accuracy ≤1%FS, in line with JJG 556 requirements
- Temperature gradient of heating system ≤2℃ (three-stage temperature-controlled resistance furnace)
- Extensometer meets GB/T 12160 Grade 1 accuracy, contact force <0.2N
Comparison of specimen preparation specifications
| Parameters | Cylindrical specimen | Hourglass specimen |
|---|---|---|
| Gauge diameter | 5±0.005mm | 5±0.005mm |
| Surface roughness | Ra≤0.2μm | Ra≤0.4μm |
| Applicable scenarios | Conventional test | High strain buckling prevention |
Implementation suggestions
- Temperature control: It is recommended to use S-type thermocouple and calibrate regularly according to JJG 141
- Data acquisition: ≥200 data points per cycle, with an additional 50 points in the load holding section
- Failure judgment: It is recommended to use a stress drop of 10% as the crack formation standard
Typical application case
A nuclear power plant steam pipeline The test of class=instrument>P92 steel at 600℃ showed that when the holding time increased from 0 to 10min, the fatigue life decreased by 42%, proving that creep damage accelerates material failure.
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