利用X射线测定小半径圆弧面切向残余应力的方法

Measurement of Tangential Residual Stress of Circular Notch with Small Radius by X-Ray Diffraction

在小半径圆弧面切向残余应力的X射线衍射测量中,对于每个名义Ψ0角,X射线照射区域各点的实际Ψ0角是连续变化的。为了便于分析,本文建议采用X射线吸收因子恒定的侧倾法进行测量。在此条件下,本文的推导结果表明,当入射线X射线束的中心与试件待测区域的中心重合时,能够测得的各名义Ψ0角的平均衍射角2θ与sin2Ψ0之间存在线性关系,并且可以利用测定平板试样残余应力同样的公式计算切向残余应力σφ。在实际测量中,上述两个中心不可能完全重合。为此,可以利用本文推荐的成对正、负Ψ0线性拟合和双侧取点抛物线拟合两种方法来选择名义Ψ0角,并进行数据处理。半径分别等于1.5、2.5和5.0mm的三根圆柱形喷丸试样的试验结果说明,上述两种方法都可以给出正确的切向残余应力测量结果。

When measuring tangential residual stress of a small radius cambered surface by x-ray diffraction, the actual Ψ0 of the area irradiated by X-ray is not a constant. In order to conveniently analyze the tnagential stress in this area, the side-incline method was adopted. In this method X-ray absorption factor kept constant. The results of this paper indicate that when the center of X-ray beam coincide with that of the sample, the linear relationship exists between average diffraction angle 2θ and sin^2 Ψ0 by that every nominal Ψ0 can be tested, and the formula of residual stress in flat sample can be used to calculate tangential residual stress σφ. In actual measurement, those two centers can not completely coincide. This paper put forward to two methods, pairing ±Ψ0 linear fitting and Ψ0 on both sides parabolic fitting to determine the nominal Ψ0 and to process data as well. The three cylindrical peening samples, whose radius were 1.5, 2.5 and 5.0mm, respectively, were tested, and accurate tangential residual stress can be obtained by those two method.