An Experimental–Numerical Approach for Modelling the Mechanical Behaviour of a Pneumatic Tyre for Agricultural Machines

Alexandros Sotirios Anifantis,Marco Bietresato,Maurizio Cutini

doi:10.3390/app10103481

Abstract

The mechanical behaviour of an agricultural tyre is a matter of extreme interest as it is related to the comfort of operators, to the adherence of agricultural machines, and to the compaction of agricultural soil. Moreover, the deformability of the tyres plays a fundamental role in vehicle stability in terms of side rollover. The behaviour of a loaded tyre during its deformation is complex, due to the combined contributions of the carcass components, the tread rubber and the air contained within it. Therefore, this study proposes an experimental–numerical approach for the mechanical characterization of agricultural tyres based on real-scale experiments and matches these results with a finite-element (FE) model. The tyre flattening in the elastic field has been described using two coefficients (Young’s modulus “E”, Poisson’s ratio “ν”), whose values have been identified with an iterative FEM procedure. The proposed approach was applied to two different tyres (420/85 R24 and 460/85 R34), each one inflated at two different pressures (1.0 bar and 1.6 bar). Young’s modulus was appreciated to be highly variable with the inflation pressure “p” of the tyres. Furthermore, the response surface methodology was applied to find two mathematical regression models, useful for studying the variations of the tyre footprint dimensions according to the type of tyre. This simple approach can be applied in other simulations without suffering any loss of accuracy in the description of the phenomenon.

Highlights

In recent decades, agriculture has faced a gradual transition towards higher working speeds for all machines involved and greater use of transport-oriented farm tractors, due to a constantly-increasing demand for higher productivities and lower costs
A centralized system to control the inflation pressure of agricultural tractor tyres according to the soil and working conditions was developed and tested in [15], and a wireless power charger for the pressure sensors was the object of another recent contribution [16]
FE model, it was possible to verify a hypothesis of linearity of the flattening varying the pressure between the two operating limits investigated experimentally (1.0 bar, 1.6 bar), simulating the vertical loading of a tyre inflated at 1.3 bar, and the linearity of the deflections of the FE model varying its elastic coefficients, using elastic coefficients derived from the coefficients at 1.0 bar and 1.6 bar

Summary

Introduction

Agriculture has faced a gradual transition towards higher working speeds for all machines involved and greater use of transport-oriented farm tractors, due to a constantly-increasing demand for higher productivities and lower costs. There are several aspects involved, from the capability for the tyres to limit energy waste while rolling (efficiency), to the capability of accomplishing successfully the tasks for which they are intended and/or which they are requested to complete (effectiveness). In this regard, the most important technical demands concern the conciliation of two only-apparently antithetical aspects involving the tyres: the safety and the performance of the vehicle when it operates both on the road and in the field. A centralized system to control the inflation pressure of agricultural tractor tyres according to the soil and working conditions was developed and tested in [15], and a wireless power charger for the pressure sensors was the object of another recent contribution [16]

Objectives

Methods

Results

Conclusion