【摘要】 用楔形加载试样测定了裂纹顶端区正电子湮没多普勒加宽谱的S参数,并确定了试样充氢以后S参数的变化。经过标定,定出塑性区内的等应变曲线。充氢以后,使塑性内的等应变曲线向外扩展,在最大切应力方向发展最快。作者认为氢使塑性区内的位错增殖或可动位错滑移,同时产生空位。更多还原

【Abstract】 The plastic zone of crack tip of wedge opening loading specimens were studied by positron annihilation technique. The line-shape parameters of Doppler broadening of annihilating radiation were measured. The value of S parameters was calibrated by specimens with known amount of strain. Then the distribution of the plastic strain in the plastic zone as a measure of the density of defects was determined. Experimental results indicate:1. The dimension of plastic zone is exactly the same as that determined by fracture mechanics.2. The distribution of strain in the plastic zone is not homogeneous.3. There is a high strain area at the very tip of the crack.4. The strain in the plastic zone is increased after electrochemical hydrogenation. Iso-strain curves are expanded preferentially in the direction of greatest shear stress. It is concluded that hydrogen facilitates the propagation of dislocations or the sliding of movable dislocations and vacancies can generate at the same time.更多还原