1. IntroductionLarge dump trucks used for civil engineering work andmine, etc. receive various dynamic loads during travel. Ingeneral, the load that a truck receives from road surface istransmitted to the chassis, such as main frame, throughsuspension. In addition, inertial force of the body, etc. on whichearth or the like is loaded also acts on the chassis. Qualityconfirmation of conventional design of dump truck is performedduring design stage by means of static stress analysis, etc.,using NASTRAN, or FEM analysis software. The load andboundary conditions for static stress analysis are determinedbased on the measurement data obtained with actual machines.However, for newly developed model of new structure, whichis different from existing models, it is difficult to determinethe conditions that are critical for frames. To solve thisproblem, we have been struggling with utilization of kinematicalanalysis software ADAMS to obtain dynamic load from theresult of vehicle travel analysis. In many cases, vehicle travelanalysis is performed assuming a model where frame, body,tire, suspension, etc. are regarded as rigid bodies. We arestruggling also with the analysis method that regards frameas an flexible body in order to obtain more accurately the loadacting on frame1). Recently we developed the method forcomparatively easily calculating frame stress during travel,using finite element method software NASTRAN andkinematical analysis software ADAMS. We applied the methodto the rear frame of newly developed model of articulated dumptruck and compared the result with actual measurement data.As a result the effectiveness of our method was confirmed.2. Conventional Method and Problems2.1 Problem of setting boundary conditionThere are two methods to determine the conditions of loadand constraint for calculating frame stress on design stage: oneto determine from the load and stress data measured withactual machine and the other to determine from the kinematicalanalysis of vehicle with rigid model.With the former method, the conditions where high stressoccurs on frame do not necessarily coincide between newlydeveloped model and existing models. Especially when newlydeveloped model employs quite a new structure, it is difficultto predict from the load data of existing models. With thelatter method, though the load acting on frame can becalculated, it is difficult to determine which condition is criticalfor the stress of each part of frame.2.2 Problem of calculation procedureFig. 1 shows the procedure for analysis with conventionalflexible bodies. As is understood from this figure, there is alot of software to use, and their procedure and operation arecomplicated.
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