Analysis Of Stresses And Deformation For Weld-Based Remanufacturing Of Coupler Knuckle

Coupler knuckle is an important component of the buffer device for traincoupler. Long-term use will cause the serious wear cracks or even scrapping onthe S-surface of coupler knuckle. Therefore it's practically useful to repair worncoupler knuckles by GMAW-based remanufacturing technology, and study thestress, deformation process and optimize the depositing path to improve therepair quality. In this paper, the thermal process, stress and deformation in theremanufactuing process of coupler knuckle (13A type) with the typicaldepositing path are studied, and the depositing path is optimized by analyzingthe thermal process, stress and deformation in different depositing processeswith different depositing paths.The thermal-mechanical coupled finite element models of repairing thecoupler knuckles were prensented using the software Msc.Marc. Due to theproblems, such as large dimensions, complex structure, large number of elements,nonlinear variation of material properties with different temperatures, difficultyin the convergence of calculation, intricate boundary conditions, the longcalculated time and so on, the life and death element method was adopted toactivate elements along the depositing paths gradually, and the contact bodieswere used to effectively decrease total number of elements and improvecalculation speed. Meanwhile, the verified experiments were carried out, and thethermal cycles and residual stresses at typical locations were measured. Aftercomparison, simulation results agreed with experiments, verifing the modelcreated.Distribution rules of the temperature and stress filed in the remanufacturingprocess along the long edges from inside to outside was revealed, and theresidual stress distribution and deformation was studied. Results reveal thatformer pass has preheating effect on later passes, and the later pass has postheatingeffect on former pass. Thermal accumulation effect increased with thenumber increase of the depositing pass. Besides, post-heating effect can releasesome stress of former passes. The residual stress is larger in the concave face ofS-surface, where the restraint is higher, than that in the convex face. And thelocal maximum stress appears in the depositing region of the last pass.After comparing the effects of different cladding paths on the thermalprocess, residual stress and deformation, conclusions are drawn as follows: Fromthe view of temperature distribution, the depositing path along long edges fromoutside to inside is better for cooling down of S-surface than that from inside to outside, and the depositing path along the short edges is the worst. From the viewof stress field distribution, the local high stress distributes in the region aroundthe last pass. In the critical region of S surface of the coupler knuckle, thedeposing path along short edges show the least traverse residual stress, and thatalong the long edges from outside to inside is better than that along the longedges from inside to outside. From the view of the deformation, all depositingprocesses meet with deformation requirement. The above results suggest themost appropriate remanufacturing path. That is the depositing path along thelong edges from outside to inside, with a waiting time 20s between adjacentdepositing. With this depositing path, it's effective to avoid large stressconcentration at the inside corner of S-surface, reduce the probability of fatiguecracks and improve remanufacturing quality.