New equipment and method for measuring welding residual stress in Francis runner

The high welding residual stress in the welded joint in the outlet of blade is one of the major reasons leading to the fatigue failure of Francis turbine runners. The welding residual stress test in as-welded and after post-weld heat treatment has been the necessary process during the manufacture of the runner. The test precision and efficiency have an important influence on the manufacture quality and schedule of runner. According to the structural characteristics of the runner,new test equipment was developed,and the welding residual stress test method for Francis runner was determined. The experimental results show that the test results could truly reflect the distribution of welding residual stress in the runner before and after heat treatment. The new test equipment and method could be applied to the test of welding residual stress in Francis runner with high precision and efficiency.