respectively the mean volume and the total volume of shell elements adjacent to ith RSW. 2.3 Finite element model The procedure is applied to a full body-in-white of a car. MSC.Nastran [1] FE model having approximately 1,000,000 dofs is meshed with 119498 CQUAD4 and 3459 CTRIA3 shell elements, 793 CHEXA solid elements and 14092 CLEAS1 spring elements as shown in fig 2(a). The subparts are assembled along 382 interfaces containing a total of 2612 active spot welds represented by CBUSH type FE spot weld model [8]. Initial spatial spot welds distribution and interfaces are shown in fig 2. The number of RSWs and eigenfrequencies of this design will be taken as references to calculate the relative shifts in frequencies and the increase or decrease in the number of RSWs. (a) (b) Fig. 2 Body-in-white (a) finite element model (b) interface definitions (total interfaces: 382, total RSWs: 2612) The optimization procedure requires new spot welds to be added in the structure, thus we created a pool of 1494 (57% of the original model) candidate RSWs uniformly along the different interfaces that can be added as required. Note that the RSWs removed during the optimization process will be placed in the pool of the candidate RSWs and will thus can be reactivated again if necessary. Robust optimization and quality control in spot welded structures 301
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