采用X射线衍射法测量铝合金3003基体材料表面残余应力中用到的衍射角。试验中，将等强度梁加载后表面产生的应力假设为“表面残余应力”，用传统电测法和X射线法分别测量加载后铝合金3003等强度梁的应力值。以电测值为参照，考察X射线法在衍射角为142°和156°时的应力测量值，并对其进行对比分析。试验表明，衍射角为142°时的测量结果存在非测量不当引起的测量非线性点。因此，X射线测铝合金3003宏观表面残余应力的最佳衍射角为156°。

The most suitable diffraction angle of 3003 aluminum alloy used for surface residual stress measurment was determined. The surface stress caused by the load is assumed to be "surface residual stress". The surface stress of loading 3003 aluminum alloy was analyzed by the traditional electrical measurment method and Xray stress measurement. With the electrical measurment method as reference, the measured values were abtained from the Xray diffraction method when the diffraction angle were 142° and 156°, and then compared with those obtained from electrical measurment method. The measurement results demonstrate that the diffraction angle at 156 ° is better than at 142 ° based on the assessment standards of the liner slope and the distribution of data. Thus, the optimum diffraction angle for Xray to measure the macroscopic surface residual stress of aluminum alloy 3003 is 156 °.