Abstract: The lifetime NF (number of cycles to failure) of a metallic structure such as a soldered joint or the like is determined by three simple, rapid tests. The first is to determine creep displacement rate vs. load (stress). Next, from the same data, the slope of the matrix creep displacement vs. load (stress) curve is determined. A third test is to obtain load (stress) relaxation over a short period of time from a load (stress) in the matrix creep displacement region. The matrix creep displacement per cycle (CPS) is then derived by plotting matrix creep displacement rate vs. time and integrating the area under this curve.