Yoshiko Shinhara

DETECTION AND EVALUATION OF DELAMINATION USING ACOUSTIC EMISSION METHOD IN THERMALLY SPRAYED COATING UNDER TENSILE STRESS

AE was measured under a static tensile load for the thermally sprayed ceramic coating in order to investigate the relationship between the detected m-value and the destruction (delamination) of the sprayed coating. This was an effective method to detect and evaluate the delamination of a sprayed coating based on the m-value, because changes of the m-value were closely related in thermally sprayed coatings. Stress level of the delamination analyzed by AE method was almost the same as that predicted by the ESPI method. The generation of delamination was confirmed by cross-section observation of the coating using both stress levels. Therefore, the ESPI method seems to be an effective way to define and evaluate the delamination of sprayed coating determine.

Nondestructive Detection of Delamination of Thermally Sprayed Material Using ESPI

Detection of delamination of a thermally sprayed coating on an SUS304 substrate was carried out nondestructively using electronic speckle pattern interferometry (ESPI) method in both static and cyclic tests at T=298 K and 873 K. Results showed that the surface strain of the coating becomes smaller than that of the substrate when delamination occurs from the interface of the substrate. Two parameters of critical strain of ε c and ε f, which correspond respectively for the static test and the cyclic test, are introduced to evaluate the existence of delamination according to the ε- σ s and ε-N curve. It is considered possible to evaluate the occurrence of delamination in cyclic tests using the static critical strain of ε c, instead of ε f.

MEASUREMENT OF THE SURFACE CONDITION OF A THERMALLY SPRAYED MATERIAL AND ITS THREE-DIMENSIONAL POSITION USING A LASER RANGEFINDER

This paper describes that a measurement method for the surface condition of a thermally sprayed object and its three dimensional position with a laser rangefinder. The feature of this rangefinder is to equip an image sensor which has the ability of simultaneously detecting the position of a light and the incident angle onto the sensor. Moreover, the sensor has an autonomous exposure time control function. Therefore, our laser rangefinder can detect the 3D positions of an object with unknown reflectance. We constructed the prototype system and did some experiments to verify the proposed method. The error of the 3D position measurement was Δz/z=0.7%. As concerns the detection of the surface condition, we could identify three types of surface roughness of a measured object with accuracy. The proposed method has great potential for a wide range of industrial inspections.

Nondestructive Detection of Crack and Delamination of Ceramics Coating on SUS304 Stainless Steel Using ESPI Method

An electronic speckle pattern interferometry (ESPI) method was applied to nondestructive detection of cracks and delaminations of ceramics coating (Al2O3/NiCr) on SUS304 stainless steel. A drop of surface strain on the coating was found when cracks in the coating or delaminations from the coating/substrate interface occurred.