A Study on the Improvement of Measuring the Residual Stresses in Weldment using Blind-hole Drilling Technique

Abstract

본 연구는 응력장이 균일하지 않는, 용접부의 잔류응력을 측정하기 위하여 현재 널리 이용되는 Blind-hole Drilling기법에 수정된 보정합수를 적용함으로 개선을 시도했다.

용접부의 응력장은 균일응력장과 선형적으로 변하는 응력자으이 서로다른 응력장으로 단순화 할 수 있다. 현재의 방법은 균일응력장의 보정을 위하여 사용되며 유한요소법으로 계산된 변형률에 Drilling으로 인한 이완된 변형률의 비인, 수정계를 준다.

유한요소 해석으로 얻어진, 선형적으로 변하는 응력에 대한 변형장은 균일응력장의 보정으로부터 얻어진 수정계수에 의해 조절된다. 압축응력과 인장응력의 교차점으로부터의 거리의 영향을 고려함으로, 이 거리의 함수로서, 보정곡선이 구축된다. 용접부의 최종 응력장이 Iteration Schemes과 연계하여 보정곡선을 이용함?막? 정확히 계측된다.

This study tried out the improvement of the blind-hole drilling rechnigue to measure residual stresses in weldments where stress fields are not uniform by application of the modified calibration function to the current method.

The stress fields in selded structure are very complex, but those in butt jointed weld specimen are simplified by two different stress fields-uniform and linearly varying. The current method is used for calibraion of the uniform stress field and gives the correction factor which is the ratio of released strains due to drilling to the strains from FEM caculations.

The strain fields of linearly varying stress fields obtained by FEM calculations are adjusted by the correction factor from calibration of the uniform stress field. By considering the effects of distances of the hole from the interface of compressive and tensile stresses, the curves for calibration constants as a function of this distance are constructed by calibration.

Final stress fields of weldments are mesured accurately using calibration curves in conjunction with the iteration schemes.

This study tried out the improvement of the blind-hole drilling rechnigue to measure residual stresses in weldments where stress fields are not uniform by application of the modified calibration function to the current method.

The stress fields in selded structure are very complex, but those in butt jointed weld specimen are simplified by two different stress fields-uniform and linearly varying. The current method is used for calibraion of the uniform stress field and gives the correction factor which is the ratio of released strains due to drilling to the strains from FEM caculations.

The strain fields of linearly varying stress fields obtained by FEM calculations are adjusted by the correction factor from calibration of the uniform stress field. By considering the effects of distances of the hole from the interface of compressive and tensile stresses, the curves for calibration constants as a function of this distance are constructed by calibration.

Final stress fields of weldments are mesured accurately using calibration curves in conjunction with the iteration schemes.