Separation Of Damage Research Articles

Acoustic Emission analysis of a comprehensive database of wire breaks in prestressed concrete girders

Acoustic Emission (AE) analysis has been established as a valuable monitoring technique for detecting wirebreaks, for example, in assessing the risk of Stress Corrosion Cracking (SCC) in older prestressed concrete bridges. A broad knowledge of the characteristics of the damage signal is crucial to reliable detection and subsequent classification. For this reason, extensive experiments were carried out on six prestressed concrete girders from three different bridges susceptible to SCC. Of these girders over 382 wirebreaks were provoked under a variety of boundary conditions, and a database of 2700 signals was collected. Typical AE features were calculated from the signals and used for analysis. For classification purposes reference data from real traffic noise and rebound hammer impacts were added to the database. The distributions of wirebreak features were found to be generally similar for all girders. Further, the local bonding conditions between the wire and the grout at the break location showed to affect the signals respective energy, which was mainly released below 50 kHz. The best separation of damage and noise signals was found for amplitude, energy, and RMS. Statistical parameters were extracted for use in deriving valid thresholds for monitoring applications.

Damage Separation in a Bipolar Junction Transistor Following Irradiation With 250-MeV Protons

Irradiation of 2N5339 n-p-n bipolar junction transistors (BJTs) with either 250-MeV protons or 10-keV X-rays shifts the input characteristics to lower values of $V_{\mathrm {BE}}$ while degrading the current gain and drive current. The degradation is consistent with increased recombination in the neutral base and emitter–base (E–B) depletion region. A decrease in collector current following proton irradiation suggests that recombination in the neutral base is significant. At a given ionizing dose, degradation is worse for proton irradiation than for X-ray irradiation due to the presence of displacement damage and a higher charge yield. A comparison of degradation produced by the two radiation sources suggests that ~40% of the excess base current resulting from 250-MeV proton irradiation is due to ionization damage. When compared with previous results for other devices, these results suggest that ionization-to-displacement damage ratios in bipolar devices may increase with proton energy in a way that is consistent with trends in charge yield and non-ionizing energy loss (NIEL).