Abstract
Methods for reducing weight of structural elements are important for a sustainable society. Over the recent years ultra high strength steel (UHSS) has been a successful material for designing light and strong components. Sandwich panels are interesting structural components to further explore areas where the benefits of UHSS can be utilized. The specific properties of sandwich panels make them suitable for stiffness applications and various cores have been studied extensively. In the present work, bidirectionally corrugated UHSS cores are studied experimentally and numerically. A UHSS core is manufactured by cold rolling and bonded to the skins by welding. Stiffness is evaluated experimentally in three-point bending. The tests are virtually reproduced using the finite element method. Precise discretization of the core requires large amounts of computational power, prolonging lead times for sandwich component development, which in the present work is addressed by homogenization, using an equivalent material formulation. Input data for the equivalent models is obtained by characterizing representative volume elements of the periodic cores under periodic boundary conditions. The homogenized panel reduces the number of finite elements and thus the computational time while maintaining accuracy. Numerical results are validated and agree well with experimental testing. Important findings from experimental and simulation results show that the suggested panels provide superior specific bending stiffness as compared to solid panels. This work shows that lightweight UHSS sandwiches with excellent stiffness properties can be manufactured and modeled efficiently. The concept of manufacturing a UHSS sandwich panel expands the usability of UHSS to new areas.
Highlights
There is an increasing requirement from the global market for lightweight structures to reduce energy consumption and emissions, and to keep the product development costs low and the lead times short
In order to investigate the necessity of periodic boundary conditions (PBCs) for the present work, a comparison is made between homogeneous boundary conditions (HBC) and PBC for both the illustrative example in Fig. 6 and the Type A core
The response is independent on the number of unit cells used in the representative volume element (RVE) which indicates that periodicity is maintained under the PBC used in this work
Summary
There is an increasing requirement from the global market for lightweight structures to reduce energy consumption and emissions, and to keep the product development costs low and the lead times short. Steel is commonly used in many sectors because of its favorable relationship between price and strength. It is not considered a light material, its strengths can be utilized to manufacture products of low weight. Ultra high strength steel (UHSS) is attractive for weight reduction. UHSS is used for body in white parts due to its high strength and in many cases high ductility. UHSS is often considered for passive safety components due to high crashworthiness. Presshardening is a hot stamping operation combined with a quenching step resulting in components with mainly martensitic microstructures and thereby high strength and very high shape accuracy.
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