Abstract
Friction stir channelling (FSC) is one of the most promising innovations based on the friction stir concepts. FSC uses a non-consumable tool, similar to that used to perform the friction stir welding (FSW) process, to produce continuous and integral channels, with any path, in monolithic aluminium alloys components in a single step. This paper presents the mechanical behaviour of friction stirred channel components in particular the fatigue resistance of the channels analysed. Finite element analyses were performed taking into account the maximum stress values applied in experimental fatigue tests of the aluminium components. The energy release rate for different crack lengths was obtained using the software ABAQUS. The fatigue crack growth curve was established according to the Paris Law, and the crack propagation direction was calculated using the maximum tangential stress (MTS) criterion. During the analysis it was observed that the critical areas are located in the vicinity of the channels corners, as it was observed in the fracture surfaces of the experimental fatigue test results.
Highlights
The disruptive nature of the friction stir welding (FSW) process has led to many developments from the research and technological development institutions and industry
From the global analysis of the fatigue test results is possible to conclude that friction stir channelling (FSC) specimens exhibit a very low fatigue strength comparing to the unprocessed base material, even though they have no defects
A thicker closing layer contributes to longer fatigue crack propagation periods, it has been observed that for FSC specimens, the crack propagation period is residual when compared with the number of cycles required for crack initiation
Summary
The disruptive nature of the friction stir welding (FSW) process has led to many developments from the research and technological development institutions and industry. Whether one is considering a crack between a base material and a coating [8], a crack between to dissimilar material joined by friction stir welding [9] or a crack between two non-metallic materials [10], crack propagation rate on the interface will always be higher This is attributed by Shah et al [11] to the mismatch in the Young’s modulus between the different materials. Studying the crack propagation along material interfaces is a complex mater and requires the use of different fracture parameters, as the energy release-rate, when considering crack propagation between to different elastic layers [11] or friction stir welds [9]. Considering the alternative version of the Paris Law in eq 6, the elapsed number of fatigue cycles for a given crack increment can be calculate This iterative process was used to predict fatigue crack propagation behaviour on the materials interface
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