Tractor accelerated structural testing by means of the rainflow method.

The remarkable developments in agriculture in recent years and the needs of customers to improve machinery in order to meet the demands of such technological developments, have driven tractor manufacturers to reduce product life and, as a consequence, development costs. The sector in which the most significant efforts have concentrated on in the attempt to decrease such costs, is that of experimental testing, so as to validate the prototype of tractors. Presently, in fact, many tractor companies rely on tests based on experience that replicate a particularly unfavourable condition a defined number of times. These tests, even if long and costly, do not always faithfully reproduce the real use of the tractor. Therefore, field tests are also carried out to evaluate the prototype during real use, but it is difficult to perform such tests for a period of time long enough to be efficient. In this context, accelerated tests have been introduced, producing a certain damage to the structure in a reduced amount of time, replicating customer use. The goal of this paper is to define a methodology for the realization of accelerated tests on a tractor, through the reproduction of real customer tractor usage. A market analysis was performed to estimate the customer usage of a 80 kW power tractor. The tractor was instrumented with strain gauges able to record the most significant loadings on the main components. A series of measures were then taken to simulate the real use of the tractor. Subsequently, the rainflow matrixes of the signals were extrapolated and used to estimate the tractor loadings for 10 years of tractor life. Finally, there was an attempt to reproduce these loadings on proving grounds with special road pavements. The results obtained highlight the possibility of reproducing field loadings during road driving and that of carrying out tractor testing in a reduced timeframe.