论文部分内容阅读
用有限元法计算了Ⅱ型缺口前端的应力场和应力场强度因子KⅡ。结果表明,最大正应力和最大三向应力所在位置(θ=-110°)和最大剪应力位置(θ=80°)并不重合;最大正应力的指向和缺口延长线成α=10°。实验表明超高强度钢Ⅱ型缺口试样能产生氢致滞后开裂,在水溶液中也能发生应力腐蚀。氢致裂纹和应力腐蚀裂纹都在最大三向应力所在位置形核,但裂纹的取向并不和该处的最大正应力垂直,而是指向该处的剪应力方向。如果没有氢,则裂纹在最大剪应力所在位置处形核,并沿最大剪应力方向扩展,即开裂角α=5°。无论是氢致滞后开裂,还是应力腐蚀,Ⅱ型试样的规一化门槛应力强度因子均比Ⅰ型试样的相应值要高,断口形貌则和Ⅰ型试样的基本相同。
The finite element method was used to calculate the stress field and stress field strength factor K Ⅱ at the front of type Ⅱ notch. The results show that the positions of maximum normal stress and maximum triaxial stress (θ = -110 °) and maximum shear stress (θ = 80 °) do not coincide with each other; the maximum normal stress points to the extension of the notch at α = 10 °. Experiments show that high strength steel Ⅱ notch specimens can produce hydrogen induced hysteresis cracking, stress corrosion can occur in aqueous solution. Both hydrogen induced cracks and stress corrosion cracks are nucleated at the location of the maximum three-way stress, but the crack orientation is not perpendicular to the maximum normal stress there but to the direction of the shear stress there. If there is no hydrogen, the crack nucleates at the position of the maximum shear stress and expands along the direction of the maximum shear stress, that is, the cracking angle α = 5 °. Whether it is hydrogen-induced delayed cracking or stress corrosion, the normalized threshold strength factor of Type II specimens is higher than that of Type I specimens, and the shape of the fracture surface is basically the same as that of Type I specimens.