Abstract: A new microcomputer aided system (MAS) developed in our laboratory for measuring fatigue crack propagation (FCP) rates in corrosive environments is briefly introduced and some parts of algorithms for data processing are given. The MAS mentioned above has been successfully applied to measuring and processing the FCP rates of 40CrMnSiMoVA high strength steel in 3.5% NaCl solution. The test results and analysis show that the FCP rates curve in 3.5% NaCl solution comprises four phases, including a plateau. The existence of the plateau may be due to the process competition model of FCP in corrosive enviroment. The fracture stress intensity factor range in 3.5% NaCl solution is much lower than that in air because of the hydrogen pens-tration. It means that the effect of hydrogen embrittlement is serious.

Key words: corrosion fatigue, crack propagation, microcomputer aided measurement