消除边界效应对Sachs测试影响的实验研究

EXPERIMENTAL RESEARCH ON ELIMINATING THE BOUNDARY-EFFECT INFLUENCE ON THE SACHS TEST

为节省测试材料,提高自增强厚壁管残余应力镗削测试(Sachs)精度和测试效率,首次提出并采用了最短测试长度的最佳边界结构的测试方法和截面数据处理方法,在测试长度为12mm的测试边界加工不同形式的空刀槽,经实测分析,选取最佳边界结构.采用沿管外壁环向均布4点径向对称贴应变片,取其各测点的均值,作为该测试截面的测试数据,避免了由管体的不同心度。不圆度、壁厚不均对测试精度的影响,保证了测试数据的准确性和稳定性,测得了管体实际残余应力沿壁厚分布值,求出了边界效应系数r及其分布曲线与方程,消除了边界效应影响,测试精度提高5％～10％,测试效率提高13倍,节省测试材料75％,为自增强厚壁管残余应力镗削测试提供了准确而可靠的新技术和新方法。

The new test methods of the optimum-boundary form and the test-data processing are put forward and used for the first time with the shortest test length in the test (Sachs) of the residual stresses on the autofrettaged tube for saving the test material and achieving test precision and efficiency. Different boundary forms are designed and machined at the boundary between the test length (12 mm) and extended length of the autofrettaged tube. The optimum-boundary form H is chosen by testing and comparing it with the test data of the different boundary forms. The test influence on the Sachs due to the difference in concentricity, circular and thickness of the tube is avoided by processing the test-section data that is tested by sticking 4 pieces of strain flakes equally and symmetrically around the outside surface of the tube, taking the average test data at each test point along the radial of the tube in Sachs, which guarantees the accuracy and stability of the test data. So the real distribution of the residual stresses on the autofrettaged tube is tested accurately. The boundary-effect coeficients η are evaluated. The formulas about ηt and ηkc are set up. The boundary-effect influence is eliminated, test accuracy is improved by 5%-10%, test efficiency is raised by 13 times, and test material is saved by 75%.