Papers by Keyword: Coating-Substrate

Abstract: Based on thermo-elastic regime, ultrasound can be generated by modulated laser pulse. When laser-generated ultrasound technology is applied to measure the thickness of coating and study the coating characters, even analysis the effects of coating during detecting the cracks and voids of the substrate, it is shown that it’s a very efficiency technology. When measuring the coating thickness, it can control the accuracy scope at the nanoscale; the relative error is under 2% for single layer coating, under 10% for double layer coating. As to coating characters, for example, Young modulus, Poisson's ratio etc, according to BP Neural network algorithm, use the nonlinear map relationship between material parameter and laser generated ultrasound wave forms to get these coating characters reversal. Studying the dispersion characteristic of the coating-substrate system can analysis effects of coating to defects detecting that coating absorbs large energy which leads to faster heat conduction speed than uncoated sample, but have smaller surface wave amplitude. All these are shown that laser-generated ultrasound technology can realize high-precise measurement and have an extensive use in the field of nondestructive testing.

Abstract: The crack problem for a functionally graded orthotropic coating-substrate structure under an in-plane load is studied. The orthotropic coating is assumed to contain a crack perpendicular to the interface. Integral transform method is used to obtain singular integral equation. Stress intensity factors (SIFs) are evaluated. The influences of orthotropic material constants and the geometry parameters on SIFs are analyzed.