Issue 42

M. Kowalski, Frattura ed Integrità Strutturale, 42 (2017) 85-92; DOI: 10.3221/IGF-ESIS.42.10 86 Figure 1 : Wavy interface line in steel – titanium bimetal. Fatigue properties of clad materials are subject of the lower number of studies than other topics combined with explosive technology. Some scientific and technical information concerning fatigue resistance and behavior can be found in fallowing papers [10,11,15]. Fatigue curves for bimetallic materials are presented in [11,12]. In the case of building fatigue curves for multilayer materials difficulty can be related to stress inhomogeneity caused by different Young’s modulus of joint metals. Problem can be extended to the uniformity of mechanical properties in the particular layers of joined materials. Studies performed on steel titanium bimetallic plates exhibited inhomogeneity of basic mechanical properties [17]. Taking into account some assumption which will be described later bimetallic material can be split on fallowing sections: sections of base and clad materials and the interface section zone characterized by substitute mechanical properties (Fig. 2). Figure 2 : Interface zone location Stresses calculated on the basis of mechanical properties of each section can be used in finite element method or in characterization of fatigue properties. The main aim of this paper is presentation of experimental fatigue test results carried out on specimens made of steel-titanium bimetal subjected to cyclic tension-compression loading. The experimental research results in presentation of mechanical properties and demonstration of strain based fatigue characteristics. M ATERIAL PROPERTIES pecimens used in study were cut from the bimetal plate carried out in the explosive welding process of the S355J steel and the titanium Grade 1. Material was heat-treated after the welding process. Heating took place for 90 minutes at 600°C and then the material and a furnace were cooled to 300°C (at cooling velocity 100°C/h). The final cooling stage was carried out in the calm air. Mechanical properties and of joined materials are presented in Tab. 1. Material Mechanical properties R e , MPa R m , MPa E, MPa G, MPa  , - A5, % S355J2 382-395 598-605 220000 84000 0.3 24-34 Grade 1 189-215 (R02) 308-324 100000 38000 0.39 43-56 Table 1 : Mechanical properties of steel S355J2 and titanium Grade 1. S