The Fatigue Analysis package provides a comprehensive set of programs for the fatigue test engineer. The package is implemented as a set of analysis modules which run within the DATS environment. This allows the ease of use of DATS Worksheets and the power of DATS BASIC to be utilized to process data in a quick efficient manner.

Fatigue analysis may be broadly categorized under the following headings:

• Cycle Counting
• Component Data (Material Selection)
• Life Prediction

The first and one of the most important stages is to collect a sufficiently long representative signal of the strain imposed on the structure. Typically signals are recorded from strain gauges sited near to a critical part of the component. After the signal is digitized, using DATS acquisition, then the data manipulation stage begins by finding the peaks and troughs (turning points). This data can then be analyzed with one of the many life prediction functions in the DATS Fatigue package. However, before using a life prediction procedure it is necessary to select the material database. The combination of the turning points and the material data means the components life prediction can now be made.

Fatigue life estimation may be divided into three classes all of which are based upon an increment of fatigue occurring for every stress-strain cycle. Of course in some circumstances the increment is zero. For example, is there is a large mean compressive stress (a 'negative' stress in the usual sense) and the stress strain cycle is such that the stress remains negative throughout the cycle then it is often assumed that no damage occurs.