30CrMnSiA材料疲劳损伤的激光检测及其细观机理

Fatigue Damage Detection and Micromechanism Analysis of 30CrMnSiA Materials Using Laser

利用激光反射衍射谱面光强随疲劳损伤试样表面逐步粗糙化而变化的原理，用一种非接触、非破坏的间接疲劳损伤检测方法，对３０ＣｒＭｎＳｉＡ材料轴线平行于轧制方向（Ｌ）和垂直于轧制方向（Ｔ）两种不同试样进行拉——拉非对称循环疲劳损伤检测，证明谱面光强比Ｋ对疲劳损伤是敏感的；损伤变量Ｄ（Ｋ）和疲劳循环次数Ｎ的关系曲线大致可以分为疲劳损伤的减速、线性和加速损失区，从而对材料进行疲劳损伤检测并对其疲劳寿命进行估计；同时对扫描电镜图像分析得出衍射光强比变化所对应的疲劳损伤细观机理。

ln this paper, the authors make use of a physical quantity, the intensity ratio K of laser diffraction spectrum, directly connected with surface roughness of metals, and define a fatigue damage parameter D(K). The detection of tension tension non symmetry fatigue damage of 30CrMnSiA is proceeded, the results of the test show the method is reliable. Moreover, the micromechanism of fatigue damage in different fatigue cycles is investigated by the use of the scaning eletron microscope. Analysis of the test results gives: (1) The intensity ratio K of laser diffraction spectrum is sensitive to fatigue damage of metal materials, especial at the beginning of fatigue. The method needs non contact, non damage, simple equipment and convenient measurements. (2) The curve relating N to D(K) can be divided into three regions, decelerated(AB region), linear (BC region) and accelerated (CD region). 90% of the life belong to the decelerated and linear regions. (3) The metallographic observation indicates that the variation of intensity ratio K is result from the surface roughening. The AB region is correspond to strain adjustment region which slip bands appear and reach the saturation state. In the BC region, the microcrack and microvoid are initiated. propagated and got together. The CD region is the region which cracks growth and intensity ratio reductoin are raped, and so the fatigue damage happens. [HJ5”:*4/9](4) Compare with two kinds of specimens, the mechanic properties (including fatigue life) of the specimen which axis is parallel to the rolling direction (T) are better than that which axis is perpendicular to the rolling direction (L).