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The strength of a radiator support frame impacted by a free-falling engine hood was examined in the present study with the use of the 3-D finite element simulations. The entire engine room of a recreational vehicle was modeled for the analysis. In order to obtain a reasonable computation time, approaches for selecting an optimum element size and cleaning the unacceptable geometries in the CAD model were studied. The penetrations and perforations occurred in the finite element mesh were detected and solved by an efficient method. In addition, the proper use of hourglass control and mass scaling to reduce the computation time without losing the accuracy of the simulation was investigated. A theoretical model was also proposed in the present study to calculate the instantaneous angular velocity of the free-falling engine hood at the incipient impact to the radiator support frame, which was used in the simulation to further reduce the computation time.

The deformation mechanics of springback phenomenon in the V-bending of sheets was investigated by the finite element analysis. The axial stress distribution in the bent sheet was classified into three zones: the bending zone under the punch corner (zone I), unbending zone next to the bending zone (zone II), and the stress-free zone (zone III). The effects of the stress distributions in these three zones on the springback were examined in detail, and it was found that the stress distribution in zone 2 plays an important role in reducing the springback. A reverse bend approach was also proposed to reduce the springback in the V-bending process. The efficiency of the proposed approach was demonstrated by the finite element simulations, and was validated as well by the experiments conducted in the present study.

The three-dimensional finite element analysis was performed for the investigation of wrinkling that occurred in the stamping processes of tapered square cups and stepped rectangular cups in the present study. An interesting characteristic of these two types of wrinkling is that the wrinkles are found at the draw wall that is relatively unsupported. In the stamping process of a tapered square cup, the effect of process parameters, such as the die gap and blank-holder force, on the occurrence of wrinkling was analyzed using the finite element simulations. The simulation results show that the larger the die gap, the more serious is the wrinkling problem, and such a wrinkling cannot be suppressed by increasing the blank-holder force. In the analysis of wrinkling that occurred in the stamping process of a stepped rectangular cup, an actual production part that bears this type of geometry was examined.