Visteon Low Cycle Bending Fatigue

Little information is available concerning low cycle fatigue analysis of 8620-gear steel. The primary area of interest in industry is in the high cycle fatigue range (10,000 + cycles). Developing stress-life, S-N, curves is the most widely used approach to understand and quantify metal fatigue. This method is most effective within the elastic range of the material. This elastic range is generally more than ten thousand cycles to failure, such as in a power transmission application. However, in a low-cycle range, where the stresses can cause some instances of plastic deformation, a stress-life method of testing and analysis does not work. In these low-cycle, high stress and strain applications, a strain-based method of testing and analysis is more appropriate

The testing procedure studied is a four-point bending test, which will provide pure bending forces. The four point bend test is used with a notched bar as the specimen to approximate the behavior of the steel in helical and spur gears. In the gears, the highest stresses are found near the tooth root area. Notching the test bar with a cavity the shape of the gear tooth root approximates the stresses in an actual gear.