This monograph examines the theoretical foundations of the spectral
method for fatigue life determination. The authors discuss a rule of
description of random loading states with the matrix of power spectral
density functions of the stress/strain tensor components. Some chosen
criteria of multiaxial fatigue failure are analyzed. The formula
proposed in this book enables readers to determine power spectral
density of the equivalent history directly from the components of the
power spectral density matrix of the multidimensional stochastic
process.