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The aim of this study is to develop an analytical solution to the deformation profile of hydroforming pre-bend process, which will be in turn fed into finite element simulation code for subsequent hydroforming simulation. The conventional approach of using FEM to simulate pre-bending is extremely time consuming in terms of both CAE work and computer running, and can not meet the cycle time required for product development and manufacturing. This is part of a series work for pre-bend modeling, with the focus here on the practice without the use of an inner mandrel, and the tube is free to ovalize during the process. Since only a portion of the tube is undergoing the bending operation, the ovalization magnitude of the tube cross-section is not longitudinally uniform due to the end constraints provided by the undeformed portion of the tube.

Long fiber reinforced plastics (LFRP) have exhibited superior mechanical performance and outstanding design flexibility, bringing them with increasing popularity in the automotive structural design. Due to the injection molding process, the distribution of long fibers varies at different locations throughout the part, resulting in anisotropic and non-uniform mechanical properties of the final LFRP parts. Images from X-ray CT scan of the materials show that local volume fraction of the long fibers tends to be higher at core than at skin layer. Also fibers are bundled and tangled to form clusters. Most of the current micromechanical material models used for LFRP are extended from those for short fibers without adequate validation. The effect of the complexity of long fibers on the material properties is not appropriately considered. Thus, modeling of these materials is lagging behind the material manufacturing and design development, which in turn limits their further development.