| Title | A Vibrating Reed Technique for the Study of Corrosion Fatigue in Geothermal Steam |
|---|---|
| Authors | Howard, R.L. |
| Year | 1980 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | |
| Abstract | The principles and operation of a method to study corrosion fatigue behaviour in geothermal steam is described. The system utilises separated steam at 10 bar pressure to excite resonant vibration in a reed specimen of test material. The high frequency and precise stress amplitude control provides for fatigue endurance data to be accumulated more rapidly and with a higher degree of reliability than w a s possible using the conventional rotating bending technique. The sensitivity of the resonant frequency to the onset of metallurgical changes within the specimen has enabled crack initiation to be identified and crack propagation velocity to be derived. The use of the facility to terminate f at i g u e tests in the early stages of crack development has made it possible to study incipient fracture surfaces by high resolution electron microscopy. The free vibration of the system lends itself to amplitude decay methods of capacity measurement. The engineering and metallurgical significance of these data is discussed wi th particular reference to the mechanism respons ible for corrosion fatigue crack initiation. |