Non-linear stress analysis for the bolt connections of a chisel tine using finite element method.

Deep tillage tools are one of the primary components of agricultural equipment which experience high level soil reaction forces during tillage operations. These forces may cause plastic deformation or failure which is undesirable for tillage machines/tools. In particular, fasteners such as bolt connections, which are utilised in the fastening of structural elements to the tillage tool’s framework, may become a key point for possible machine failure during tillage operations. Therefore, prediction of the stress distribution or likely failure point of the bolt connections during tillage operations is a very significant issue. In this context, advanced computer aided engineering (CAE) methodologies, which have been applied successfully in design and manufacturing operations in many industries for many years, may be useful in the design process of tillage tools to prevent failures of the machine elements. However, these methodologies have not become mainstream practice for agricultural machinery design and manufacturing operations. In this study, the focus is on the determination of the stress distributions on the preloaded bolt connections of a chisel tine using advanced CAE applications. A three-dimensional (3D) solid model of a chisel tine and its framework fasteners were modelled using a commercially available 3D solid modelling design software package. Subsequently, the operating conditions of the chisel were simulated and the stress distributions of the bolt-nut couples of the tine connection group were determined through finite element analysis (FEA) with non-linear contact definitions using a commercially available FEA code. Simulation results showed that even though partial stress accumulations were seen on the bolts, these would not cause any plastic deformation or failure. For the final evaluation, safety factors of the fasteners were calculated according to the material yield point. Maximum safety factor was 3.18 for bolt number 4 under maximum loading conditions of the tine. It was commented that lower quality bolts could be used there. This study has improved the understanding of the CAE methodology for the design of agricultural machinery elements and contributes to further research into the development of agricultural machinery design, aided through the utilisation of advanced CAE tools.