Abstract
Abstract: In order to improve the fatigue performance of a welded A-type frame in a heavy off-road mining truck, a novel method was presented to implement lifetime and weight collaborative optimization while considering uncertainties in geometry dimension, material properties, and bearing load. The mechanical and cyclic material parameters were obtained from experimental work to characterize the base metal and the weldment. The finite element model of a welded A-type frame was constructed to analyze stress distribution and predict fatigue life, the force time histories of which were acquired from multi-body dynamics simulation. The simulated failure position and fatigue life had a good agreement with the actual results. Then, both structural lifetime and weight were considered as optimization objectives. The thickness of main steel plates and elastic and cyclic material parameters were chosen as uncertain design variables as well as main loads at connection locations. The fifty sample points in the light of Latin hypercube sampling method and its responses calculated by finite element analysis were supposed to build the approximation model based on the Kriging approximation method. After its fitting precision was guaranteed, the non-dominated sorting genetic algorithm II (NSGA-II) was utilized to find the optimal solution. Finally, the fatigue life of a welded A-type frame was increased to 2.40×105 cycles and its mass was lessened by 8.2%. The optimized results implied that good fatigue performance of this welded A-type frame needs better welding quality, lower running speed for downhill and turning road surface, and thicker front plates.
Highlights
The welded A-type frame of steering system is considered as one main bearing component for mining dump trucks
The fracture mechanics method firstly assumes that the crack or crack-like flaw exists in the weld metal, Appl
According to the optimized results, it was beneficial to this welded A-type frame when four absolute cyclic material parameters increased and four loads at extend fatigue life of this welded A-type frame when four absolute cyclic material parameters connection sites were decreased
Summary
The welded A-type frame of steering system is considered as one main bearing component for mining dump trucks. Its fatigue performance is seriously concerned when the truck runs on poor road surface with hundreds of tons of goods. This frame is welded with different thickness of plates; fatigue cracks often start from weld toe located at stress concentration areas [1]. There are several methods to predict fatigue life of a welded structure. These could be categorized into nominal stress [2,3], structural stress [4], local notch [5], and fracture mechanics approaches [6].
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