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用有限元法通过J积分计算了Ⅱ型试样的应力场强度因子K_Ⅱ·在此基础上,用高强度钢40CrNiMoA Ⅱ型缺口试样研究了疲劳和腐蚀疲劳裂纹形核的规律,并探讨了氢的影响.结果表明,疲劳裂纹不在最大剪应力位置(θ=80°)形核,而是在最大正应力位置(θ=-110°)形核,裂纹取向和最大正应力垂直(α=-80°)。如充氢或在水中腐蚀疲劳,则裂纹形核位置和取向发生了改变,即θ=-85°,α=-55°。动态充氢使缺口形成疲劳裂纹的门槛值从28.8降为10.2MPa·m~(1/2).当△K_Ⅱ较低时,腐蚀疲劳裂纹沿晶形核,这和空气中疲劳时完全不同.
The finite element method was used to calculate the stress field strength factor K Ⅱ of type Ⅱ specimen by J integral method. On the basis of this, the regularity of fatigue and corrosion fatigue crack nucleation was studied by using 40CrNiMoA Ⅱ notch specimen of high strength steel. (Θ = -110 °), the crack orientation and the maximum normal stress are perpendicular (α = 0 °). The results show that the fatigue crack does not nucleate at the maximum shear stress (θ = 80 °) -80 °). Such as filling hydrogen or corrosion fatigue in water, the crack nucleation position and orientation has changed, that is, θ = -85 °, α = -55 °. The threshold value of fatigue crack growth under dynamic charging is reduced from 28.8 to 10.2MPa · m ~ (1/2) when dynamic charging of hydrogen is carried out.When ΔK_Ⅱ is low, the corrosion fatigue crack is nucleation along the crystal nucleus, which is completely different from the fatigue in air.