Abstract
To clarify the influence of specimen twisting caused by residual stress introduced during spraying of thermal barrier coatings (TBCs) on Young's modulus measured using gradient of load-strain curve by four-point bending test, both finite element analysis and four-point bending test were employed. The result of finite element analysis showed that the strain distribution of the specimen at longitudinal direction was affected by specimen twisting angle. The load-strain curve at the center of the specimen showed almost linear relationship, and influence of twisting angle was negligibly small. The gradient of the curve at the surface center of the specimen was almost independent of specimen twisting angle, and the gradient of load-strain curvature within 0.5 % irrespective of specimen twisting angle. The result of four-point bending test showed that the accuracy of Young's modulus was improved by using four-point bending jig with pin rotation and limiting the measuring load range. The Young's modulus of TBCs measured by strain gauge method was almost independent of coating thickness, and those measured by deflection method increased for smaller coating thickness, but showed almost stable value for laser coating thickness.
