Structural strength calculations of the cab skeleton using FEA analysis and scenario approach methodologies

The problem and the task formulation

The manufacturer of cabs for agricultural machines encountered a problem of modernization � within a brief period of time � of a batch-scale cab so as to install it on more powerful and, hence, heavier machines.

Problem-solving technique

Using 3D design, we created a 3D model of a mass-scale cab skeleton. All procedures were performed under CAD/CAE/PDM. Then we determined the magnitudes, the duration and the directions of rated loads. 3D modeling and FEA analysis was carried out using I-DEAS Software by EDS Company.

The 3D model was used to make a required model of the cab skeleton, following which we used FEA solutions to make a range of stress and strain analysis, simulating overturn of the tractor leading to deformation in the calculated points of the skeleton as well as tensions in the beam materials and in welded joints.

The welded skeleton was calculated with due account of the material plasticity. Its specific feature was as follows: several different directional loads, variable in time, sequentially impact the skeleton, and they are applied to different surfaces; each sequential load must be applied to the skeleton bent by the residual plastic deformation from the previous load.

Our scenario methodology allowed us to make the entire calculations over a brief time and with a high precision, predicting behavior of the cab in case of the machine overturn and assessing its safety. The behavior scenarios were handed over to the client who analyzed the cab structure safety.

Results

The work performed allowed selecting very quickly the rolled shapes needed for a strong cab skeleton and testing the bearing capacity of the structure. The fact that full-scale tests were performed only during the final design phase enabled the client to save time and significant resources. It took three weeks to prepare load conditions and to make a three-dimensional model and calculations.

When the client performed full-scale testing of the cab, it turned out that their results confirmed our calculations and the skeleton had the predicted strength.