ESPI를 이용한 鎔椄剖에서 彈性計數 測定

Abstract

The problem of material property changing nearby welding zone due to large localized thermal stress within the narrow heat-affected zone has acknowledged by numerical analysis and mechanical manufacturing industries. The knowledge of the Young's modulus distribution in the welding zone is important in understanding the dynamic or static behavior and solving it. There are two main approaches by which the mechanical behavior under a loading can be inferred: experimental and theoretical. The numerical solutions such as finite element methods may not produce sufficiently accurate results for the evaluation of the mechanical behavior, because of the complexity of the material property nearby seam in welding. This research proposes the measurement technique of Young's modulus based on Electronic Speckle Pattern Interferometry(ESPI) and Euler-Bernoulli equation. General approach for the measurement of Young's modulus is tensile testing. However, extracting the small dog bond specimen nearby welding zone is one difficult problem and it is the second problem that difficult to get the accurate property with the small specimen because of the sensitive boundary condition of testing machine. ESPI is one of laser speckle interferometry with the advantage of non-contact, high-resolution and whole-field measurement. The technique has been developed as a common measurement method for vibration and surface displacement. In vibration analysis, whole-field mode shape (surface displacement distribution) at a resonance frequency is visualized by ESPI with image processing device. And also the maximum surface displacement distribution from ESPI is a clue to find the resonance frequency at each vibration mode shape. The cantilever, Euler-Bernoulli beam, is tested to find resonance frequencies, from which the Young's modulus can be determined using Euler-Bernoulli equation. Five cantilevers with 5 mm width from welding seam are analyzed to estimate the Young's modulus. The experimental works and the analysis show that the property of the nearest sample from seam is much higher than that of standard sample. The simple technique based on ESPI gives Young's modulus of thermal-affected welding zone with high accuracy and the detailed properties can give sufficiently accurate results in theoretical approach.