Aspects regarding the increase of the protection level of the falling-object protective structures (FOPS) by using the post-critical behavior of the support elements

Abstract

For earth-moving machinery which are operated in areas with danger of falling objects on its cabin, an important performance requirements imposed on the machine is the protection of the human operator in case the cabin is hit by a falling object. As a result, the mechanical system formed by the cab’s strength structure and its supporting elements must have the ability to dissipate high impact energies, so that the deformed system does not penetrate the deflection limiting volume (DLV). In general, the support on the chassis of the falling-object protective structures is rigid, so almost all impact energy is dissipated in the deformation of the cabin’s strength structure. The present article proposes that most of the impact energy be dissipated in the post-critical deformation of some dissipative removable supporting elements interposed between the chassis of the machine and the falling-object protective structure. In addition, the article proposes the numerical evaluation of the post-critical behavior of the analyzed mechanical system, using finite element analysis. The first part of the article briefly presents the main regulations in the field of falling-object protective structures, as well as the methods of approaching the evaluation of the performances imposed on these structures, with their advantages and disadvantages. Following are given the main aspects of the optimal modeling of structures for numerical analysis of their behavior, the particularities of numerical evaluation of post-critical behavior and some constructive solutions of dissipative elements. The final part of the article is dedicated to a case study and the author’s conclusions.