용접된 판의 진동특성에 관한 연구

Abstract

Precise analysis for the vibration is critical at the initial design stage of the structure in order to prevent fatigue fracture. Fatigue fracture caused by resonance is the most fatal factor among other negative effects of vibration on structures. And the local structures of the ship and offshore structure can be occurring a large vibration response by adjacent external forces. Welding is the main method of manufacturing a structural product that could be applied to shipbuilding, construction, automobile and other industrial fields. And welding could change the rigidity and mass of a structure that is highly critical to determine the natural frequencies. So despite that, the variation of natural frequencies by welding shall be critically considered at the basic design process of local structures, it is hardly seen. In this study, Impact test and Fast Fourier Transform(FFT) was applied to assess the natural frequency of welded and unwelded plate which is one of the most basic structural member. And three parameters of specimen are considered at the investigation of the FFT results: i) Thickness, ii) Support boundary condition, iii) Welding direction. Based on the results, the qualitative variation trend of natural frequencies by welding on plate is observed. And it can be applied to find the quantitative numerical values of welding effect.