Fatigue reverse loading

Although it is a modifying factor for (variable) actions, it is the main means of regulating such actions to allow for changes in material properties resulting from load effects, e.g. cyclic loads, fatigue or reversing loads, and impact loads. 

Fig. 10.21. Dependence of the fatigue limit for fully reversed loading R = —1) on the tensile strength in different material classes [113]...

Figure 10.19 Fatigue behaviour of diagonally plied samples loaded in tension or reverse loading (Bach/ECN).

An adequate description of material behavior is basic to all designing applications. Fortunately, many problems may be treated entirely within the framework of plastic s elastic material response. While even these problems may become quite complex because of geometrical and loading conditions, the linearity, reversibility, and rate independence generally applicable to elastic material description certainly eases the task of the analyst for static and dynamic loads that include conditions such as creep, fatigue, and impact. 

The specimen (R = 0, R = -1) demonstrate clear effects of corrosion fatigue (Fig. 6 and 7). There evidently is a good correlation of the fatigue strength reduction between the pulsating stress (R = 0, uniaxial) and the pulsating pressure loaded pipe specimen (Fig. 8). The reversed bending probes (R = -1, uniaxial) exhibit some deviations. 

---