The strength evaluation method of welded joints for truck frames is studied by fatigue tests of actual-sized component models and small-sized component models. The following results were obtained from the tests. (1) The calculation method by FEM analysis for the stress intensity factor K of the welded joints is verified by the stress distribution and fatigue test results of component models. (2) Configurations of the fatigue fracture occurred at the root of the welds are clarified by actual-sized component models testing. Judging from these results, it was proven that the strength evaluation method mentioned in this report is valid in practical use for actual truck frames.
