A Net Map Method on Vehicle Structural Fatigue Damage Analysis

In order to effectively use the vehicle road test load spectrum data and adjust road test specifications, a net map method on vehicle structural fatigue damage analysis is proposed, by taking the vehicle subframe as a study objective. This article consists of three parts. First part discusses that, the finite element analysis model of the vehicle subframe was built in ANSYS software, and its construction stress was calculated and analyzed under the action of lateral and longitudinal forces, respectively. The hot points on the control arm were determined, which could bring about fatigue damage. The location was identified as load testing point P, where strain rosette was pasted. Second part discusses that, the strain load of the subframe was measured under the condition of proving ground, eight kinds of roads that fall under combination roads were chosen in the proving ground and the vehicle speed was found to be different on each road. After finishing the data processing, and the pure signal of vehicle subframe was acquired. Using rain flow counting method, the load spectrum of the subframe was worked out, and load distribution histogram on the testing point was obtained. On this basis, according to local stress-life method and Miner standard and stress concentration correction factor, the fatigue damage analysis was completed for the subframe under the combination road and each of the enforced roads. Third part discusses that, the fatigue damage density and weight of each road conditions were calculated under the condition of each enforced road about subframe structure, and a net map that represented its closed area fatigue damage was drawn. In the net map, the central angle represents the damage weights on different road conditions and the radius length represents the damage density on each road. The results show that the network diagram can easily express the vehicle structural damage under the conditions of all the different combination of roads when the size of the central angle and length of radius were changed, vehicle structure damage relative to the change would be obtained by drawing a new net map. This method provided a convenient and effective way to analyze vehicle fatigue damage.