A New FEM Approach for Simulation of Metal Foam Filled Tubes

Abstract

The combination of thin metal cases or tubes with a filling made of metal foams is interesting and promising for many applications in mechanical engineering. Components made of an outer hollow thin compact metal structure and a cellular lightweight core are especially suited to energy absorption applications. In order to allow for an efficient product/process design with a concurrent engineering approach, reliable and computationally affordable\ud finite element method (FEM) calculations are required by both product and process engineers.\ud The structural performance of these complex composite parts must be numerically predicted, in order to find the optimal combination of outer structure and metal foam properties.\ud While FEM simulation at large deformations of bending, crushing, etc. of thin sheets and tubes is state of the art, the accurate FEM simulation of the mechanical behavior of metal foams cannot be considered fully established. In this paper the three most common\ud methods for FEM simulation of metal foam materials are discussed: (a) homogenization approach, (b) realistic reconstruction of tomographic data, and (c) repetition of standard\ud unit cells. A new effective approach is proposed, suited for simulation of composite, metal foam filled, structures of realistic dimensions. The approach is based on meshing the metal foam by replicating a unit cell made of 32 triangular shell elements, and then by randomizing the nodal position in order to emulate the intrinsic homogeneity of foam morphology.\ud The method is validated by means of different experimental tests. The results show that the proposed method correctly predicts the behavior of foam structures in axial compression.\ud The method slightly overestimated the actual load registered in three point bending tests. \ud Several improvements are described and discussed in the paper, such as randomization of nodal positions of the mesh, in order to reduce the overestimation of forces. An FEM approach for the simulation of large deformations of metal foam filled metal structure (e.g., tubes) suited for the design of realistic large dimensions structural components has been presented. The proposed method shows some innovative features with respect to the available scientific literature, such as a configuration based on octahedral unit cells with low number of triangular shell elements. Randomization of nodal positions of each unit cell has\ud been implemented as a method for better representing the intrinsic variability of metal foams and for reducing the stiffness of the simulated structure

Metamodeling Based on the Fusion of FEM Simulations Results and Experimental Data

“…In order to design and optimize this kind of structures, numerical simulations are needed, but they are time consuming due to the complexity of physical phenomena involved in the deformation and collapse of hollow cells. Furthermore the approximation of the real bending process, since not all factors involved are taken into account, can be very rough [13]. On the other hand, experiments are usually available in limited numbers, due to the high cost of the materials involved.…”

Development and implementation of an effective constitutive model for architected cellular iron-based shape memory alloys: Pressure dependency and transformation-plasticity interaction

“…The model was used to simulate the effects of the material properties and geometry parameters on the “indentation load versus displacement” curve. Later, Strano (2011) used FEM to predict the structural response of metal foam filled tubes under compression. Their key idea was to mesh the metal foam by replicating a UC made of 32 triangular shell elements and then randomize the position of the nodes so as to mimic the intrinsic variability of the foam morphology.…”

Efficient Design-Optimization of Variable-Density Hexagonal Cellular Structure by Additive Manufacturing: Theory and Validation

“…These natural cellular materials have inspired the design of engineered cellular structures such as lightweight structure, wave absorption materials, and the cores of sandwich panels [3][4][5][6][7][8][9][10]. Perhaps the most prominent feature of cellular structures is their low relative density, which leads to material savings and weight reduction in products.…”