Quadratic Cohen representations in spectral analysis of serration process in Al-Mg alloys

Important from mechanical point of view the Portevin-Le Chatelier serration phenomenon is being characterized by a complicated spectral profile. As a typical example of nonstationary processes it demands a special treatment allowing to follow the evolution of energy of stress fluctuations as a function of strain. The authors suggest the utilization of a compact system of quadratic transformations, known as Cohen class, as a technique enabling the reliable analysis of serration processes. In this elaboration a comparison of the application of various Cohen decompositions to analyze frequency bands has been introduced.