Measurements of coating density using ultrasonic reflection coefficient phase spectrum

A nondestructive method to determine the density of coating has been proposed in this paper based on the ultrasonic reflection coefficient phase spectrum (URCPS). A model was set up first to represent the ultrasonic waves reflected from a coating system at normal incident, and the relation between the extremum of URCPS and the coating density was established to provide the principle of determining the density. The ultrasonic method was validated on a series of ZrO2-7 wt.%Y2O3 (YSZ) coatings with various density. The specimens were prepared by electric beam physical vapor deposit (EB-PVD). After deposition, the specimens were irradiated using high-intensity pulsed ion beam (HIPIB) at different ion current density of 100 and 200 A/cm2 to change coating density. The coating densities of as-deposited and post irradiation by HIPIB were derived to be 4940-5030, 5200-5320 and 5390-5470 kg/m3, respectively. The relative error between the coating density measured by the ultrasonic method and Archimedean principle ranging from 2.53% to 6.11%, indicates that the proposed ultrasonic quantification method provides a reliable nondestructive way to determine coating density.     

激光辐照热障涂层中平面应变问题的热弹性变分分析

 针对激光辐照热障涂层材料的平面应变问题，提出热障涂层热弹性分析的基本方程，对定常温度场给出级数形式解析解，并用最小余能原理和变分法分析了结构的热弹性应力场，研究了最大应力和界面应力的分布特征，并就一些物理参数的影响进行了讨论。结果表明，热障涂层的主要破坏因素为表面拉伸应力，界面应力相对较小，但在自由边界有集中现象，剥落应力大于剪切应力，是导致涂层破坏的重要原因。涂层厚度增加会改变厚度方向上的应力分布，界面应力向中心集中。