博士 / 國立臺灣海洋大學 / 系統工程暨造船學系 / 96 / In Taiwan, the material of stainless steel SUS630 is usually used in propulsion shafting system for high-speed crafts. Unfortunately, the pitting corrosion will be a main factor to effect the fatigue life cycle of the stainless alloy SUS630. In this study, the prediction model of the residual fatigue life cycle and the reliability have been established under the pitting corrosion condition for the propulsion shafting system of high-speed crafts.
In this study, the growth rate and tendency of pitting corrosion occurred in the stainless steel SUS630 specimen is estimated by the grey system theory through the ferric chloride acceleration corrosion test. Under such pitting corrosions, the prediction model of fatigue life has carried out by the results of the rotation bending tests on a set of specimen. Meanwhile, the constants of fatigue crack growth rate of SUS630 under pitting corrosions have been determined by means of the metallurgical graphs by SEM and the fracture surface analysis techniques. In the consequence of these processes, the residual fatigue life and the reliability of a pitting corroded stainless steel shaft can be assessed.
From the results of the pitting corrosion experiment, the tendency of growth rate of pitting corrosion of the SUS630 steel is pertaining to an exponential function with time. Based on the results of fatigue tests on the specimen with pitting corrosions, the residual fatigue life cycle is only 10-20% of that of the uncorroded specimen. By the fracture surface analyses of the SEM graphs, it has shown that the direction of fatigue crack propagation between the stages of crack propagation and abrupt fracture has only a 45° angle of change. In use of the Paris formula, the value of Δk is rated between 26 to 46, the material constants n is determined to be 3 and c is 4.4×10-15 for the stainless steel SUS630 shaft material.
The established model in the thesis can be applied to the preliminary design for propulsion shaft under the prescribed reliability index and estimate the allowable limitation of pitting corrosion depth and the residual fatigue life. Meanwhile, in the survey stage, this reliability model can be also applied to ascertain whether the shaft should be repaired or not, once the pitting corrosion depth is measured. Thus, the life cycle reliability and safety of the propulsion shaft system can be envisaged.
Key words: propulsion shafting system of high-speed craft, stainless steel SUS630, grey system theory, corrosion fatigue and reliability
| Identifer | oai:union.ndltd.org:TW/096NTOU5345001 |
| Date | January 2007 |
| Creators | Fong-Yuan Ma, 馬豐源 |
| Contributors | 王偉輝 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 250 |
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