Issue 39

O. Daghfas et alii, Frattura ed Integrità Strutturale, 39 (2017) 263-273; DOI: 10.3221/IGF-ESIS.39.24 265 (a) (b) (c) (d) Figure 2 : (a) Loading Direction of cutting (b) Electronic extensometer (c) Tensile test machine and (d) acquisition chain. Experimental set The test is carried out on a hydraulic press (SHIMADZU) that has a maximum load capacity of 30 kN (Fig. 2 (c)), class 0.5 BS EN ISO-1 [15]. A chain acquisition (see Fig. 2 (d)) allows recording the strain as a function of stress. The loading speed is 4MPa.s-1. Two electronic extensometers are used to measure the strain rate according to the width and the thickness along the tensile test (Fig. 2(b)). Experimental results Experimental database contains three tensile curves and their experimental Lankford coefficients (r 0° , r 45° and r 90° presented in Tab. 1). Experimental tensile curves of 7075-T7 in three directions 0°(RD), 45° (DD) and 90°(TD) from the rolling direction are presented in Fig. 3. Uniaxial tensile tests taken for three orientations to the rolling direction reveal the nature of anisotropy in this material where strengths and ductility vary with orientation in the plane of the sheet. Fig. 3 shows similar yield strength and plastic deformation characteristics in the rolled RD and DD directions until 11.5% in strain. The TD direction has a similar yield strength but different hardening characteristics and lower elongation (8%). This result exhibit a marked tensile anisotropy. Fig. 3 indicate that the 7075 in temper T7 is defined by maximum percentage elongation along the rolling direction and minimum value along the transverse direction.