2025 June 2nd Week WBM News Recommendation - Fatigue Life Reduction

While one type of corrosion-generated hydrogen damage usually causes relatively sudden fractures, we know that another causes a continuous reduction in fatigue strength. In the book Fatigue Design (John Wiley & Sons, 1970) by Carl C. Osgood, he cites numerous tests showing how corrosion affects the fatigue strength of various metals. Ironic is that, with steel alloys, the stronger the alloy, the greater the reduction in fatigue life. One of the book's charts shows that a 60,000 psi steel has a 39 percent reduction in fatigue strength while, with identical conditions, a 130,000 psi steel has a 66 percent reduction. From a practical standpoint, there is good data showing that even a humid atmosphere will result in a significant reduction in fatigue strength and eliminating that surface corrosion is beneficial. (With this knowledge, we wrapped a series of 145,000 psi (1 GPa) machine shafts with vinyl tape and found a five-fold increase in average shaft life.) Most fatigue design involving steel alloys is based on a given fatigue strength that doesn't decrease after 106 or 107 cycles; however, corrosion will continually reduce the fatigue strength until the cyclically loaded part will eventually fail.