Construction and performance experiment of load test system for half axle of combine harvester

Abstract: Half axle is an important part of a walking system in a combine harvester; the damage from half axle is generally fatigue failure, which has a direct effect on the reliability and stability of the combine harvester. Minority combine harvester manufacturers have half axle fatigue test rigs, and most of the loads on the fatigue test rig are set artificially, thus it cannot accurately predict fatigue life of half axle in absence of comprehensive consideration of various alternating loads. Fatigue life analysis and fast in doors simulation of the load fatigue test on the basis of load spectrum can provide the basis for the improvement of half axle. Improvement of fatigue performance of half axle is conducive to the competitiveness of the products on the market at home and abroad. It is not a suitable solution to use traditional shaft or disc torque sensors to test the torque of half axle, because the half axle is closed in the transmission. Operating environments of combine harvesters are complex, and half axles often bear a complex alternating load which puts forward higher requirements on the stability and reliability of the performance of the load test system. To provide a precise and comprehensive load-time course for the compiling of load spectrum of the half axle of a combine harvester, the complex and alternating load signal in typical working conditions must be acquired accurately. Based on an analysis of working characteristics and the construction features of chassis of combine harvesters, a wireless load test system was put forward in this paper by choosing reasonable torque and rotation speed sensors and data acquisition systems composed of hall sensors, rotation speed signal acquisition modules, resistance strain gauges, power modules, torque signal acquisition modules, wireless routers, computers, and software for signals test and analysis. In order to exclude the influence of measured value of torque signals by bending moment, axial force, and temperature, a reasonable arrangement of resistance strain gauges was designed. The load test system does not need to transform the structure of the gearbox and it is easy to install. The structure of half axle is redesigned so torque acquisition module terminals can be connected to the leads of resistance strain gauges. Mounting brackets of double modules and positive & negative hall sensors were manufactured to set up torque signal acquisition modules and hall sensors. In this system, wireless Wi-Fi communication technology was used to transmit the load signal of the torque and rotation speed of the half axle wirelessly. In order to test the performance of the wireless load test system and acquire the load signal of the torque and rotation speed of the half axle precisely in typical working conditions, the Julong 280 type tracked combine harvester was chosen as the experimental prototype to do load testing experiments in the field with the wireless load test system, after debugging the system in the laboratory. It showed that the data acquired is reliable and the performance of the wireless load test system is reasonable and feasible after processing and analyzing the torque and rotation speed signal of half axle.