We have developed the automatic measurement system for corrosion fatigue crack in synthetic seawater and the micro-computer controlled corrosion fatigue testing system. These systems are combined with the electrohydraulic fatigue testing machine and the computer. In the automatic measurement system for corrosion fatigue crack length, the corrosion fatigue crack are automatically measured by using a d.c. potential drop method and the micro-computer. In the micro-computer controlled system, the fatigue testing machine is controlled by the micro-computer. Fracture mechanics parameters, such as ΔK, the crack opening level, ΔKeff and da/dN can automatically be calculated.
A d.c. potential drop method has been adopted to monitor the corrosion fatigue crack in seawater and has been connected with a micro-computer (Komai, 1986). Because the principle of d.c. potential drop method is simple, a specific apparatus does not need. It is also easy to treat the data using the micro-computer (Yagawa and Fukuda, 1983). Then, using a d.c. potential drop method, it may be possible to develop the corrosion fatigue testing system which operates correctly at high speed in seawater. In the present study, we have developed" the corrosion fatigue testing system in order to automatically measure a corrosion fatigue crack length in seawater. This system can make data treatment using a d.c. potential drop method and micro-computer which automatically controls an electro-hydraulic fatigue testing machine. We have confirmed that the developed fatigue testing system is available on the measurement of corrosion fatigue crack growth behavior in synthetic seawater.
Fig.1 shows the micro-computer controlled fatigue testing system developed in this study. This consists of 98kN electro-hydraulic fatigue testing machine(Saginomiya, Mode12602) and two micro-computers(Sanyo, S802 and NEC, PC9801vm). S802 micro-computer controlled the fatigue testing machine and PC9801vm micro-computer was used for the data treatment.