Issue 40

Z. Zhang et alii, Frattura ed Integrità Strutturale, 40 (2017) 149-161; DOI: 10.3221/IGF-ESIS.40.13 153 Plastic energy accumulation during the cyclic loading By ignoring the energy dissipation such as acoustic emission, electric and magnetic energy dissipation, then Eq. (9) could be simplified as below:            W t D t Q t (13) In which    Q t is the thermal energy increment,    D t could not be got directly but could be achieved by calculating the total energy increment and thermal energy increment. E XPERIMENTAL DESIGN AND SETUP Sample description he sample in this study is a steel plate with two elliptical cutouts both on top and bottom of the plate. The dimension of the sample is 280x160x5 (mm). The centers of these two elliptical holes and the major axis of the ellipse are located on the top and bottom boundary, respectively, as shown in Fig.1. Obviously, the opening area of the holes depends on the opening parameters of a and b, where a is the length of semi-major axis and b the length of minor semi-major axis. The ratio value of a/b is set as a constant of 2, while the opening areas are set different for comparison. As shown in Tab. 2, the opening ratio, defined as the ratio of the opening area to the area of the steel plate, is set as 10%, 15%, 20%, and 25% to get the final optimal opening parameter. Specimen Opening ratio a/mm b/mm SPA10 10% 53.42 26.71 SPA15 15% 65.42 32.71 SPA20 20% 75.54 37.77 SPA25 25% 84.46 42.23 SPB10 10% 106.84 53.42 SPB15 15% 130.84 65.42 SPB20 20% 151.08 75.54 SPB25 25% 168.92 84.46 Table 2 : Parameters of Shearing couple beam damper. The samples are made of Q235 steel, with Young’s modulus E =2.07e5MPa and poisson’s ratio  =0.3. Tensile test of standard sample selected in the same batch was conducted to find the actual yield strength, the constitutive model achieved in the test is shown in Fig.2. SPA SPB Figure 1 : Coupling beam damper with top and bottom openings. T