Issue 43

B. Saadouki et alii, Frattura ed Integrità Strutturale, 43 (2018) 133-145; DOI: 10.3221/IGF-ESIS.43.10 134 the precipitation hardened copper alloys offer cost saving and they are suitable for many industrial applications under various mechanical loading conditions. Cu-Ni-Si alloys strengthened by precipitation hardening are used in very wide range of electrical and electromagnetic applications. However, the cyclic circulation of alternating current induces fatigue failure during the high frequency electromagnetic applications [5]. Fatigue behavior of Cu-Ni-Si alloys has been investigated in few articles [6- 9]. In [6], authors investigated the microstructure of the material at different heat treatment states and its influence on the low cycle fatigue (LCF) and high cycle fatigue (HCF). They have noticed a softening effect of the copper alloy under LCF [6]. Goto et al. [8] studied the role of the Ni 2 Si curing compound in fatigue crack initiation and propagation mechanism and identified a localized fatigue behavior. Zhao et al. [9] agree that the curing compound in Cu-Ni-Si is coherent with the matrix. Consequently, the main mechanism of crossing the secondary phase (Ni 2 Si) by a sliding dislocation is shearing. Besides, the alloys studied are of a different chemical composition than that of proposed in this work. This work is proposed to determine the fatigue characteristics for a Cu-Ni-Si alloy known by its trade name of SICLANIC ® . The SICLANIC ® is also strengthened by the precipitation of the Ni 2 Si phase [10]. This alloy was mainly studied from a microstructure based investigation [11, 12]; while there exist few other studies with the focus on the mechanical aspects [13, 14]. However, fatigue properties of this alloy has never been reported before in the literature. Fatigue test results are often represented by probabilistic Wöhler curve using statistical method and this curve has been developed due to the dispersions of tests results. In recent years, Castillo and Fernández-Canteli worked on the statistical analysis of the S-N and E-N fatigue curves [15], and they extended the probabilistic model to the strain damage evaluation to estimate fatigue life prediction in many applications [16, 17]. In this study, the probabilistic model of ASTM E 739[18] is applied to estimate Wöhler curves. M ATERIAL AND EXPERIMENTAL PROCEDURES ICLANIC ® alloy used in this study has the chemical composition with 96.9 % of copper, 2.5 % nickel and 0.6 % silicon in weight percent. The material has been received in bars of 14 mm × 14 mm× 60 mm dimension. To optimize high cycle fatigue tests, we chose classical specimen shape with circular section according to the ASTM E466-07 standard (Fig. 1) at MOROCCO CETIM. The fatigue tests were carried out on an MTS biaxial hydraulic machine model 17 with imposed stress at a temperature of 20 °C. During the tests, the temperature was controlled using a thermocouple (Fig. 2). Solicitations were loaded in uniaxial cyclical mode, with a sinusoidal waveform, according to repeated tensile loads. (a) (b) Figure 1 : Fatigue specimen (a) schematic illustration showing the specimen geometry and (b) image of the actual fatigue specimen. S