Parametric Study of Fatigue Crack Growth in a Finite Plate

Fatigue crack propagation is an undesirable phenomenon that may lead to catastrophic failures in many components and structures, therefore it is important to understand its underlying mechanics. To that effect, systematic parametric studies of fatigue crack propagation laws are interesting to determine how fatigue life varies with the constants that define the mechanical behavior of a given material in a fatigue situation, such as the Paris’ law constants, fracture toughness (Kc) or the stress range ??. The parametric studies performed in the present work assess the influence of several parameters, assuming that failure occurs when K>Kc, but also when all the material ahead of the crack is yielding. It was found that m and C, the Paris’ law parameters, are the most influential parameters in terms of fatigue life. The present study should help future designers when choosing materials for components or structures subjected to cyclic loads.

Wall pressure fluctuations induced by a single stream jet over a semi-finite plate

This work provides an experimental investigation into the interaction between a jet flow and a semi-finite plate parallel to the jet. Wall pressure fluctuations have been measured in a high compressible subsonic regime and for different distances between the jet and the plate trailing edge. The experiment has been carried out in the ISVR anechoic Doak Laboratory at the University of Southampton, using wall pressure transducers flush mounted on the plate surface. Signals were acquired in the stream-wise direction along the jet centreline and in the span-wise direction in a region close to the trailing edge. The radial position of the flat plate was fixed very close to the jet axis to simulate a realistic jet–wing configuration. The plate was moved axially in order to investigate four different jet-trailing edge distances and to include measurements upstream of the nozzle exhaust. The acquired database was analyzed in both the frequency and the time domains providing an extensive statistical characterization in terms of spectral uni– and multi–variate quantities as well as high order statistical moments. A wavelet analysis was performed as well to investigate the time evolution of the wall pressure events.