13th International Conference on Fracture June 16–21, 2013, Beijing, China -5- chemical composition, mechanical properties at elongation and environmental conditions of tests are given in [33]. L=1000 mm t=6.1 mm D=219 mm 61 mm a=3.05 mm r=0.15 mm r=3.05 mm 45o * T, hours Holding pressure p=20 bars Burst pressure p=p* Applied pressure, bars T=96 hours 12bar min dT dp = 12bar min dT dp = Figure 4. Tubes- Specimen for test Figure 5. Burst tests of the model specimens made from Ukrainian tube: a - elastoplastic failure; b – catastrophic brittle fracture. TFiugbuerse‐s4p.ecimens have a longitudinal notch on the outer surface and their geometry is given in Pipes were tested until burst according to the test sequence described in Figure 5. T-stress distribution indicates that T stress is negative and increases with internal pressure (see Fig.6). Test results showed that burst pressure for test in methane is equal 118 bar pmax = and burst pressure for test in hydrogen is equal 122bar pmax = . Therefore, there is no gaseous hydrogen effect on the strength of notched pipes for considered testing conditions. At this critical pressure effective T-stress Tef is equal to – 22.268 MPa. This negative value indicates a relatively low constraint. Figure 6. Evolution of T- stress versus distance over ligament. Pipe submitted to internal pressure. Diameter 400 mm thickness 10 mm (pressure 50-80 bars)
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