Dynamic Responses of Crack Welded Pipe Based on Frequency Response Function (FRF) for Fault Detection

Abstract

Welding technique is one of the most important and often used methods for joining metals in industry. Welded joints are used in almost every industry depending on various applications and where the permanent joints with high strength are deemed necessary. Some of the applications are used in structural supports, automotive joints, piping industries, pressure vessels etc. Welded joints, particularly in the welded pipe structure have a complex non-linear behavior which may be due to the material’s geometry or the contacts itself at the joints. However, cracksin a structure can happen either at the interfacial contacts or in the material of the components. The cracks may change the dynamic properties of the structure such as natural frequency, mode shapes and structural performance that may lead to premature failure to the structure. Therefore, this paper presents a crack detection method using a vibration-based damage detection techniqueusing the frequency response function (FRF) data. A combination of the numerical model and physical welded pipe structure with and without cracks in pipe structure will be investigated using the experimental modal analysis (EMA). A finite element analysis (FEA) utilizing HyperMesh Version 13.0 software has been utilized to model the scheme. A validation procedure is also employed to detect the presence of cracks in the welded pipe structure based on the FRF data from the parameter values used in both the benchmarked and cracks models. The comparison of the with/without cracks welded pipe structure has revealed that the effect of the FRF between with/without cracks welded pipe structure is clearly influenced by the stiffness reduction in the crack structure.