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无裂纹扭转试样充氢后在恒定的扭矩作用下能产生氢致滞后开裂。顺时针扭转时裂纹面和扭转轴成45°;反时针扭转则沿-45°面产生裂纹。计算表明,如果氢原子在α-Fe中的应变场是非球对称的,则氢原子的应变场和扭转应力场之间存在有互作用能,而且在45°面(顺时针扭转时)上具有极小值。这就将导致氢原子向45°面扩散和富集,当其浓度达到临界值时就会引起氢致滞后开裂。对于充氢的缺口或预裂纹扭转试样(即Ⅲ型裂纹)上述结论也成立。
Hydrogen-induced hysteresis cracking can be produced under constant torque by a crack-free torsion specimen after filling with hydrogen. Clockwise twist crack surface and torsion axis at 45 °; anti-clockwise twist along the -45 ° surface cracks. Calculations show that if the strain field of hydrogen atoms in α-Fe is aspherical symmetric, there exists an interaction energy between the strain field of hydrogen atoms and the torsional stress field, and at the 45 ° plane (clockwise) Minima. This will cause hydrogen atoms to diffuse and enrich toward the 45 ° surface and cause hydrogen induced hysteresis cracking when their concentration reaches a critical value. The above conclusion also holds true for hydrogen-charged breaches or pre-cracked torsional specimens (ie Type III cracks).