13th International Conference on Fracture June 16–21, 2013, Beijing, China 4 Rp(MPa) Ft(kN) 1.2 0.67 Proof total Extension Rt(MPa) 95 95 The ratio of Yield strength 0.88 0.95 The ratio of tensile strength to Yield Strength 1.14 1.05 The yield strength σs and ultimate strength σb were calculated according the equation (1) as follow: 0 s s F A σ = ， 0 b b F A σ = （1） in which, Fs means the yield load, Fb means the maximum load and the A0 original cross section area of specimen. As the yield stress of the EQ70/56 has no yield step, it is very difficult to accurately determine its yield stress( which means it is difficult to determine the stress at the beginning of its yield step). Generally, It takes the stress, when it generate a specific permanent strain (usually 0.2%), as the yield stress [9]. At the beginning of the stress-strain curve, the stress proportionally rises against the strain, while its ratio is the elastic modulus. While the strain increased to 0.2%, plotted a straight line with a slope equaling to elastic modulus. The corresponding value to the intersection between the plotted line and the stress-strain curve was the equivalent yield stress. The outputs of the test were forces and deformations, which should be calculated to the inputs of the stress-strain curve. In the present test, the stress σ and strain ε were determined by the equation (2) as follow: σ=P/ S0, ε=δ/ L0 （2） According to the results of the test and calculated date, the stress-strain curve could be plotted as figure 1. Figure 1 The stress-strain Curve of EQ70/56 The maximum load could be calculated from the displacements and forces of the test, the results
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