Abstract
Composite work tools have many components, and complex shapes when compared to standard tools such as rotaries and plows. In addition, the component durability for the tools is critical because the load varies severely according to the soil conditions. This study predicts the fatigue life of the hub bearing in composite work tooling. The loads acting on the tools were measured based on field tests, and the loads acting on the hub bearing were derived using the load reconstruction method. The static safety factor and fatigue life of the hub bearing, loads, and contact stress acting on the inner and outer raceways and presence of truncation were analytically predicted based on the derived loads. The fatigue life of the bearing changed depending on the preload amount of the hub bearing. The bearing life was more than 3000 h for preloads of less than 40 μm, which satisfied the target life of 1200 h. The load acting on the inner and outer raceways of the bearing decreased and then increased as the preload amount of the bearing rose. The bearing contact area, maximum contact stress, and number of balls increased as the load applied to the hub bearing rose. The fatigue life, load, contact stress, and static safety factor of the hub bearing met all requirements, and no truncation occurred on the inner and outer raceways of the bearing. The test verified the achievement of the target life of 1200 h and confirmed that there was no breakage, cracking, or deformation of the bearing.
Highlights
A farm tractor is a machine for various farm jobs by installing attachments such as a rotary and a plow in the vehicle’s power take-off (PTO) or a three-point hitch system
Changes in the loads applied to the inner/outer raceways of the two rows of bearings according to the preload of the hub bearing, the maximum contact stress, and truncation, and the static safety factor of the bearings according to ISO 76 were identified [17]
All the static safety factor and fatigue life of the bearing, the loads on the inner/outer raceways, contact stress, and truncation satisfied the requirements according to ISO 76 and 281 even under loads applied to the hub bearing, that is, test load conditions [16,17]
Summary
A farm tractor is a machine for various farm jobs by installing attachments such as a rotary and a plow in the vehicle’s power take-off (PTO) or a three-point hitch system. In the case of the hub bearing used for smooth rotation of the disk harrow in composite working implements, severe misalignment occurs because of combined loads acting on the disk harrow, and there are difficulties in lubrication because of poor working environments This misalignment dramatically affects the accuracy of the fatigue life of the bearing predicted through the ISO standard. This method is very easy to measure when the torque meters are installed on the tractor’s wheels, but it is necessary to reduce the measurement error of wheel speed in order to measure the transmitted output power exactly It may differ slightly from the actual load since it is assumed that the measured load is the same as the tractor’s tractive force and this load is applied to all components of the working implement. The predicted fatigue life of the bearing was verified through a life test
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