1. A computer tool for dimensioning tractor protective structure based on mechanical modeling and full-scale tests
- Author
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Al Bassit, L., Tricot, N., Technologies et systèmes d'information pour les agrosystèmes (UR TSCF), Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), and Irstea Publications, Migration
- Subjects
[SDE] Environmental Sciences ,OPERATOR SAFETY ,FALLING OBJECT PROTECTIVE STRUCTURE ,TRACTORS IN USE ,[SDE]Environmental Sciences ,REAR ARCH ROLL-OVER PROTECTIVE STRUCTURE ,TRACTOR PROTECTIVE STRUCTURES - Abstract
International audience; To ensure the safety of operators working in the farms and in the agricultural holdings, the employment regulations demand that self-propelled vehicles be equipped with protective structures. Two types of protective structures are often fitted on agricultural tractors and agricultural self-propelled vehicles (ISO 26322-1:2008): the Roll-over protective structures (ROPS) and the Falling object protective structures (FOPS). The presence of the ROPS is currently obligatory by the French labor code while the presence of the FOPS is mandatory only if a potential risk of falling objects exists. However, when a new need emerges on a farm, for example the need to lift loads, the tractor is often modified, here, by installing a front loader. As a result, the risk of object falling on the conductor, which was very low before, becomes significant. The protective structures of a new designed machine require proof of compliance before being introduced to the market (article R4313-1 of the French labor code). For this reason, these structures undergo a standardized full scale destructive test to prove its resistance and its ability to protect the conductor (OECD 2017). This destructive test procedure is very costly and unsuitable for custom-made FOPS, which are manufactured individually. In the case of the in service tractors for which manufacturers do not offer FOPS device, there is no certified method to evaluate the performance of a designed FOPS, other than this destructive procedure (Directive 2009/144/EC –Annex II). Some studies and software have been developed by institutions like INAIL (Italie) and Irstea (France), (Inail 2011) and (Irstea 2004), aiming to offer methods for designing and implementing Roll-over protective structures for the in service tractors which are built without commercial ROPS. The research team (Mangado, Arana, Jarén, Arazuri & Arnal 2007) proposes a method of calculation to design easy carrying ROPS, adaptable for all tractor models lacking this kind of protective structures. With the same aim, (Harris 2008) develops a Cost-Effective ROPS (CROPS) with a prediction method to evaluate the performance characteristics of these ROPS. The importance given to ROPS is justified by the high percentage of serious accidents which was related to the lack of this type of protective structures, compared to other fatal accidents related to agricultural machines (Loringer & Myers, 2008). Irstea software of ROPS dimensioning was upgraded in 2014 (Al-Bassit, Langle, Sayegh & Tricot 2014) to include the possibility to add a FOPS to the ROPS proposed by the software. Other than that, FOPS design and test alternatives have been poorly studied by researchers. The purpose of the work described in this paper, which has been funded by the French agricultural ministry, is to develop a computer tool to be used as a guide to help in designing and implementing FOPS, on the in-service tractors, with a performance similar or close to that of the certified ones. After a statistical study and a categorization of the protective structures fitted on the tractors in use sold in Europe, the focus is mainly on the agriculture tractors equipped with a rear arch ROPS without FOPS. Some of the FOPS architectures proposed to be assembled on this type of ROPS, have been considered and discussed. One of these architectures is selected as the principal solution for tractors equipped with rear arch ROPS, it consists of a cantilever roof clamped on the ROPS. In this paper, the methodology used to establish the computer tool is developed. The tool checks the possibility to equip a tractor with a cantilever FOPS, based on the tractor’s qualitative and quantitative data characteristics, measured and provided by the user. It selects the detailed architecture of FOPS that is adequate to this tractor, dimensions the different parts to be manufactured and gives the user the steps necessary to form and fix the cantilever roof. An examination and a categorization of the rear arch ROPS fitted to the tractors in service are carried out. The main geometric parameters characterizing these ROPS are identified; twenty two categories are taken into account. A decision algorithm, based on the geometric parameters of the tractor and its ROPS, is established. It allows choosing the architecture of the attaching link between the FOPS roof and the ROPS. Thirty-six different architectures are taken into account. A FOPS validation study, based on numerical modeling and full-scale impact tests, is carried out to ensure the performance of the structures being proposed by the computer tool: -Numerical simulations using finite elements method is used to compare the static behavior of different FOPS alternative designs, as well as to compare the static behavior of the main categories of rear arch ROPS attached to loaded FOPS roof. Numerical modeling, using ANSYS software, identified the least favorable ROPS to the implementation of a cantilever roof, from both rigidity and displacements points of view. -Full-scale impacts with falling object were carried out according to kinetic energy prescribed in the standardized procedure. The impacted structures are manufactured taking into account the least favorable configurations, dimensions and conditions. These experimental tests provided the scope of validity of the proposed structures. This is implemented in the decision algorithm to provide the user with designed structures similar in performance to those FOPS which passed the standardized full-scale test successfully. The developed computer tool proposes detailed FOPS design for tractor equipped with rear arch ROPS. Validation tests are currently in progress, being carried out by a limited number of users, before distribution to the public.
- Published
- 2017