Simulation of impact energy in functionally graded steels Ali Nazari a , Jamshid Aghazadeh Mohandesi b,⇑ , Mehdi Hamid Vishkasogheh b , Mohammad Abedi b a Department of Technical and Engineering Sciences, Islamic Azad University (Saveh Branch), Iran b Department of Mining and Metallurgical Engineering, Amirkabir University of Technology, Iran article info Article history: Received 24 October 2010 Received in revised form 12 November 2010 Accepted 14 November 2010 Available online 13 December 2010 Keywords: Functionally graded steel Impact energy Crack arrester Crack divider Finite element simulation abstract Charpy impact energy of functionally graded steels produced by electroslag remelting composed of graded ferritic and austenitic layers together with bainite or martensite layers has been studied. Number and type of constituent phases of composites are the most important factors affecting impact energy in crack divider configuration. In crack arrester configuration, this mostly depends on the notch tip position and the distance of notch tip with respect to the bainite or martensite layers. Finite element method has been conducted to simulate impact energy of composites. A relatively good agreement between experi- mental results and the results obtained from simulation was observed. Ó 2010 Elsevier B.V. All rights reserved. 1. Introduction Charpy V-notch (CVN) impact test is a widely used test on notched specimens which are submitted to the impact of a ham- mer with the given kinetic energy [1]. Some researchers have tried to mathematically model Charpy impact behavior of monolithic materials [2–6]. Although some of these models seems promising, but none of these works show realistic results because of their sim- plifications and assumptions. Therefore, several works have been carried out focusing on evaluating impact behavior utilizing more accurate instrumented Charpy impact test [2,3,7–13]. Also, some models have been recently proposed to model Charpy impact behavior using neural network [14,15]; these models are at their infancy and need to be extended. A comparatively good method has been developed to predict Charpy impact behavior of materials by numerical modeling spe- cially using finite element method (FEM). Among those are FEM modeling of Charpy impact energy of different materials especially structural steels [4,16–26]. Mathur et al. [19] have presented a 3D analysis of failure modes in the Charpy V-notch specimens. Tverg- aard and Needleman [24] have analyzed the effect of weld orienta- tion in Charpy specimens by 3D simulation. Hong et al. [25] performed the Charpy test with notch position varied within HAZ and reported that the absorbed energy is influenced by notch posi- tion with respect to various microstructures and it was reduced as notch position approach to the base material. Jang et al. [26] have simulated Charpy impact energy of heat affected zone with differ- ent notch tip positions. Very few fracture experiments, particularly dynamic fracture, of FGMs have been reported. Among them, crack tip deformation and fracture parameter history in functionally graded glass-filled epoxy were evaluated for low velocity impact loading by Rousseau and Tippur [27]. Guo and Noda [28] studied the dynamic response of a functionally graded layered structure with a crack crossing the interface with in-plane impact loading condition. Xu et al. [29] investigated the plane strain problem of semi-infinite cracks in an infinite functionally graded orthotropic material with opening and in-plane shear impact loading modes. Bezensek and Hancock [30] studied the toughness of laser welded joints of low alloy steel under mode I and mixed mode configuration along with Charpy impact tests. Functionally graded steels have been produced by electroslag remelting process (ESR) [31]. Studies on transformation character- istics of FGSs produced from austenitic stainless steel and plain carbon steel has revealed that as chromium, nickel and carbon atoms diffuse at remelting stage, alternating regions with different transformation characteristics are created. When appropriate arrangement and thickness of original ferritic ( _ a) and original austenitic ( _ c) steels is selected to make electrodes, composites with graded ferrite and austenite regions together with bainite or martensite layers may be made as follows [31]; ð _ a _ cÞ el ! R ðabcÞ com ð _ c _ a _ cÞ el ! R ðcMcÞ com 0927-0256/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.commatsci.2010.11.019 ⇑ Corresponding author. Address: Department of Mining and Metallurgical Engineering, Amirkabir University of Technology, 424, Hafez Avenue, Tehran, Iran. Tel.: +98 21 64542963; fax: +98 21 66405846. E-mail address: agazad@yahoo.com (J. Aghazadeh Mohandesi). Computational Materials Science 50 (2011) 1187–1196 Contents lists available at ScienceDirect Computational Materials Science journal homepage: www.elsevier.com/locate/commatsci