DOI 10.1515/htmp-2012-0108 High Temp. Mater. Proc. 2013; 32(2): 163 – 169 Josip Brnic*, Goran Turkalj and Sanjin Krscanski Experimental Research and Analysis of Non-alloy Structural Steel Response Exposed to High Temperature Conditions Abstract: This paper presents and analyzes the responses of non-alloy structural steel (1.0044) subjected to uniaxial stresses at high temperatures. This research has two important determinants. The first one is determination of stress-strain dependence and the second is monitoring the behavior of materials subjected to a constant stress at constant temperature over time. Experimental results refer to mechanical properties, elastic modulus, total elongations, creep resistance and Charpy V-notch impact energy. Experimental results show that the tensile strength and yield strength of the considered material fall when the temperature rises over 523 K. Significant decrease in value is especially noticeable when the temperature rises over 723 K. In addition, engineering assessment of fracture toughness was made on the basis of Charpy impact energy. It is visible that when temperature raises then impact energy increases very slightly. Keywords: non-alloy structural steel, material properties, creep behavior, high temperatures PACS ® (2010). 62.20.-x, 62.20.de, 62.20.Hg, 62.20.mm *Corresponding author: Josip Brnic: Department of Engineering Mechanics, Faculty of Engineering of University of Rijeka, Vukovarska 58, 51000 Rijeka, Croatia, E-mail: brnic@riteh.hr Goran Turkalj: Department of Engineering Mechanics, Faculty of Engineering of University of Rijeka, Vukovarska 58, 51000 Rijeka, Croatia, E-mail: Turkalj@riteh.hr Sanjin Krscanski: Department of Engineering Mechanics, Faculty of Engineering of University of Rijeka, Vukovarska 58, 51000 Rijeka, Croatia, E-mail: Sanjin Krscanski@riteh.hr 1 Introduction 1.1 Modern design of structures There are many factors influencing the final design of structures. Among these factors there are: the type of structure, required security, the purpose of the structure, material, loading, desired service life, production technol- ogy, production costs, etc. An adequate response to the fulfillment of any set of factors can be provided by a modern design based on a numerical analysis of struc- tures and computer aided design. The safety and cost of the structure depend on establishing the optimal dimen- sions of the structure elements [1]. In most structures, the primary function of a member is to support or transfer external loads that act on it, without failing [2]. Thus, for the purpose of structural analysis, it is necessary to model structure geometry and its behavior [3]. Modeling the structure with complex geometry and modeling its load and inelastic response is a very challenging subject. However, modern design must be based on the optimiza- tion of all elements and processes that contribute to it. Regarding the safety of any structure, the predicted service lifetime is a key issue [4]. Each engineering element or structure as a whole is designed and produced so as not to contain any crack. Defect can be detected by standardized test methods used at the end of a production cycle and process of assembling of structure parts. Nevertheless, en- gineering practice has shown that some failures may arise for various reasons, for example, defects can occur during welding processes, service behavior due to thermal attack or encountered stresses, etc. One of the most demanding tasks in engineering practice is an analysis of failures, i.e. to discover why and how structural component has failed, or in other words to discover the cause of failure origin and its expression form. The most common failure modes that are encountered in engineering practice are: yielding, corrosion, buckling, fracture, creep, etc., [5]. Inelastic strain that increases with time at constant stress is known as creep. The constant load and constant stress creep processes may be treated as the same if small strains are under consideration [6]. Usually, as it is known from liter- ature, creep process is appreciable above temperature of 40% of melting temperature [7]. Creep process is an im- portant subject discussed in this study. Also, more infor- mation about mechanical properties, creep behavior of similar materials and possible stress structural analysis can be found in Refs. [8–11]. Brought to you by | The University of York Authenticated | 194.27.128.8 Download Date | 6/3/13 12:38 PM