Crashworthiness Optimization of Hydraulic Excavator Cab Roof Rail and Safety Prediction: Finite Element Analysis and Experimental Validation

Off-road trucks, tractors and earth-moving machines are at high risk of accidents involving falling objects or rollovers. Therefore, these machines need proper protective structures to protect operators. This study investigates the crashworthiness optimization of a hydraulic excavator cab roof rail based on an improved bi-directional evolutionary structural optimization (BESO) method considering two different load cases (a lateral quasi-static load and an impact load from the top of cab, respectively). In the crashworthiness optimization problem, a weighted summation of external works done by the two different load cases is treated as the objective function while the volume of design domain is treated as the constraint. A mutative weight scheme is proposed to stabilize the optimization and balance the two load cases. Finite element (FE) model is established and two prototypes are fabricated based on the optimal design. Explicit FE analysis is used to predict the performance of roll-over protective structure (ROPS) and falling-object protective structure (FOPS) under standardized laboratory test. The smooth evolution histories of reaction forces demonstrate the effectiveness of mutative weight scheme. The simulation-based test results for the ROPS and FOPS have a close agreement with the experimental test results. The accuracy and efficiency of the FE analysis are high enough to predict the behaviors of ROPS and FOPS under the laboratory tests.