Xiaoyuan Lou

Effect of Ethanol Chemistry on Stress Corrosion Cracking of Carbon Steel in Fuel-Grade Ethanol

Abstract A systematic study was carried out to understand the effect of ethanol chemistry (chloride, water, pHe, and oxygen level) as well as other controlling parameters on the stress corrosion cr...

Film Breakdown and Anodic Dissolution during Stress Corrosion Cracking of Carbon Steel in Bioethanol

The stress corrosion cracking (SCC) behavior of X-65 carbon steel was investigated in simulated fuel-grade ethanol (SFGE) using the slow strain rate test method, potentiodynamic polarization, electrochemical impedance spectroscopy, open-circuit potential, and potentiostatic current monitoring. Results indicate that crack initiation on carbon steel in the SFGE environment is associated with plastic deformation in the material, which leads to a surface film breakdown. The competition between active anodic dissolution and repassivation ahead of the crack tip controlled the propagation of these cracks in SFGE. Within the anodic dissolution range, both crack density and crack growth rate in the through-thickness direction increased as the potential increased. The applied cathodic potential eliminated the SCC in this system. The mode of SCC for the carbon steel in aerated SFGE was predominately transgranular.

Properties of leaky and degenerate modes in a prism–film coupler with waveguide structure

A laser beam can be efficiently fed into a planar thin film by means of a prism–film coupler. The properties of the cavity modes, the coupling efficiency, the optimum coupling condition, etc. of the prism–film coupler can be explained using the theory developed by Tien and Ulrich [P. K. Tien and R. Ulrich, J. Opt. Soc. Am. 60, 1325 (1970)]. Based on multiple scattering and multiple wave interference, we propose a theory of the two modes referred to as the leaky and degenerate modes. The properties of the two kinds of modes, such as positions, linewidths, angular spectrum of the leaky mode, and the degenerate mode spectrum are studied in detail. This theory gives an excellent explanation of the underlying origin of light wave propagation in the prism–film coupler.

Effect of Chloride Transients on Crack Growth Rates in Low Alloy Steels in BWR Environments

The objective of this study was to quantify the effect of chloride transients on stress corrosion cracking of pressure vessel low alloy steels. Two heats of reactor pressure vessel steel were evaluated at various chloride concentrations in both NWC and HWC environments. The tests showed that low alloy steels can exhibit a delayed cracking response during a chloride transient. The delayed response is attributed to the concentrating and dilution processes of anionic impurities inside the crack. The crack can maintain its original growth rate for a certain period after the chemistry change. The effects of chloride concentration, stress intensity factor (K) and periodic load cycling on the crack incubation and growth in low alloy steel will be discussed. The results from this work will provide a direct input to development of a crack growth model for low alloy steels, water chemistry guidelines and effects of chloride transients on crack growth.