Topology optimization in ROPS-safe design process of operator cabin for forestry, agricultural and construction machinery

Abstract

ROPS (roll over protective structure) and FOPS (falling objects protective structure) today are mandatory elements of every modern operator cabin for forestry, agricultural, construction and other machinery. This passive safety structures, integrated into cabin, can save life of the operator during rollover and heavy objects falling accident. Usually this structures consists of a supporting frame, capable of withstanding all the loads, which are occurring in machine accident. These elements, besides their main purpose, should satisfy additional requirements: not to cut operator visibility range, allow wide doorway for working and emergency doors and so on. Also initial design style solution restricts possible arrangement for load-bearing elements of the ROPS. Last decades in ROPS design process engineers extensively use explicit finite element technique to predict behavior and fitness of the ROPS structure by numerical simulation of rollover loads. This greatly reduce the costs of experiments, allowing to exclude dozens and hundreds of poor solutions at early stage of design without building expensive prototypes. However, uneven search of construction solution, even with support of numerical simulations, can be very time consuming. This work describes two-stage optimization technique, including topology and parametric optimization, which significantly reduce amount of structure variants, analyzed in ROPS design process. Therefore, optimization is an alternative to convenient way of inheritable and intuitive way of design. Topology optimization method with specially built finite element model of the forestry machine cabin used to find the most beneficial loadpaths for ROPS load bearing. Then, simplified shell-beam finite element model built, using results of topology optimization, and a parametric optimization technique used to find optimal cross-sections dimensions for main load-bearing elements of the protection structure. Finally, detailed shell model of the whole cabin elaborated and verified using standard explicit finite element simulations of all ROPS loadcases. Final simulations proved the strength of the designed ROPS structure and give confidence in successful experiment tests. The main advantages of the described two-stage optimization technique are significant reduction of considered variants due to exclude of inappropriate solution in advance, initial design style solution is not changed.