Issue 35

J. Kramberger et alii, Frattura ed Integrità Strutturale, 35 (2016) 142-151; DOI: 10.3221/IGF-ESIS.35.17 142 Focussed on Crack Paths Damage and failure modeling of lotus-type porous material subjected to low-cycle fatigue J. Kramberger ( http://orcid.org/0000-0001-9112-1091 ) K. Sterkuš S. Glodež University of Maribor, Faculty of Mechanical Engineering Smetanova 17, SI-2000 Maribor, Slovenia janez.kramberger@um.si, klemen.sterkus@student.um.si , srecko.glodez@um.si A BSTRACT . The investigation of low-cycle fatigue behaviour of lotus-type porous material is presented in this paper. Porous materials exhibit some unique features which are useful for a number of various applications. This paper evaluates a numerical approach for determining of damage initiation and evolution of lotus-type porous material with computational simulations, where the considered computational models have different pore topology patterns. The low-cycle fatigue analysis was performed by using a damage evolution law. The damage state was calculated and updated based on the inelastic hysteresis energy for stabilized cycle. Degradation of the elastic stifness was modeled using scalar damage variable. In order to examine crack propagation path finite elements with severe damage were deleted and removed from the mesh during simulation. The direct cyclic analysis capability in Abaqus/Standard was used for low-cycle fatigue analysis to obtain the stabilized response of a model subjected to the periodic loading. The computational results show a qualitative understanding of pores topology influence on low-cycle fatigue under transversal loading conditions in relation to pore orientation. K EYWORDS . Porous materials; Low-cycle fatigue; Damage; Finite element analysis. I NTRODUCTION enerally, porous materials are relatively new class of materials with low densities and novel physical, mechanical, thermal, electrical and acoustic properties. These materials present a unique opportunity for adopting in light- weight structures, for energy absorption, for thermal management, and for acoustic absorption [1, 2]. Existing applications are in the mechanical, aerospace and automotive domains [3]. Significant research has been performed regarding optimal manufacturing methods for porous metal material. Current manufacturing methods enable to create various metal foams, either open-celled or closed-celled foams with varying regularity, isotropy and density, perlite metal composites, metallic hollow sphere structures, APM structures etc. [4]. Main factor which affects mechanical properties of porous material is pore structure. For example, porosity of conventional metal foam is high, while mechanical strength is low [5]. On the other hand, lotus-type manufacturing method is capable to produce lotus-type material, which has different pore structure in comparison with metal-foams. The porosity of lotus-type metal is lower and pores are cylindrical and oriented in one direction (Fig. 1). Structural properties of lotus-type porous material depend upon the manufacturing method, cell size and morphology [6]. G