Fatigue Analysis Of The Clamparm Of The Forging Manipulator

The statistical data show that 50-80%of failure of mechanical components was caused by fatigue fracture.There are many difficulties to estimate fatigue life of heavy-load manipulator,because of the big size,complex load cases and uncertain stress concentration areas.Therefore,finite element(FE) simulation is of great importance to evaluate the fatigue life of the key components of the heavy-load manipulator.Forging manipulator is a typical type of heavy-load manipulator,which is the main assistant equipment of the heavy forging press machine over 10,000 tons.The fatigue fracture accidents of its clamparm often occur.The purpose of this paper is to fully understand fatigue performance of the clamparm.First,the history of development of fatigue analysis,fatigue FE analysis,and fatigue problems of the forging manipulator were discussed.And then the fatigue-resistant design methods,the uniaxial and multiaxial fatigue theories and the influence factors of the fatigue strength were summarized.Based on the fact that the worst load case took place in the actual forging process,the main forging procedure of stretching was simulated by the explicit nonlinear dynamic analysis,from which the load spectrums for fatigue analysis of the clamparm were obtained.Finally,the procedure of fatigue analysis of the key components of the forging manipulator was established by the means of the FE fatigue analysis method.An overall fatigue analysis of the clamparm was performed, including the global and detailed analysis,crack initiation to growth,with and without flaws. The main conclusions are as follows:(1) The explicit nonlinear dynamic analysis can simulate the realistic forging process. Not only the displacement and the stress,but also the force acted on the forging manipulator used as the load spectrum input for fatigue analysis of the clamparm,can be obtained.(2) The stress-life fatigue analysis can be used to determine the dangerous load cases and areas of structures.For the clamparm,the most dangerous situation is the rectangular cross-section workpiece forged at the location close to the forging manipulator,and the dangerous area is around the comer with stress concentration.(3) The results of the multiaxial fatigue assessment show that the most dangerous part of the clamparm is subjected to proportional multiaxial load.Thus,Hoffman-Seeger biaxial stress-strain model should be applied for the fatigue life assessment.The inherent flaws of the structure,which have great effect on the fatigue life,should be strictly controlled.