Structural Optimization And Forging Process Analyses Of Large Hydraulic Loader Rocker Arm

Rocker arm is the key stress component of the large hydraulic loader,which plays a key role on the service life and safe reliability of the loader.At present,rocker arm prepared by casting process has an severe influence on the safe reliability of loader as its greater weight and low mechanical properties.As a result,the casting rocker arm already can’t meet the requirements of large-tonnage loader.Forging not only has good size features,but also higher intensity.Rocker arm forging instead of casting is the effective way and will be the inevitable trend for guaranteeing the safe reliability of loader.However,the bulk of rocker arm is great is up to5.8×107 mm3,and its weight is up to 400 kg.Due to complex forging process,it can’t simply and directly produced by forging process.Therefore,the study on optimization design of rocker arm structure and simulation of forming process by FEA method has an important instruction significance for actual production.The research taking forming process of rocker arm as study subjects,the corresponding improvement was carried out based on the differences of design principles between castings and forgings.With the purpose of weight reduction,the static analysis of rocker arm was carried out and the optimization design of rocker arm structure was done with NCGA,which under the conditions of unchanging dimensions of rocker arm,as well as satisfying stiffness and strength.The deformation behavior and constitutive equation were studied of rocker arm material 35 MnB steel by hot compressive tests in the 790~1190℃temperature and 0.01~10s-1 strain rate ranges using thermo-simulator system Gleeble 1500 D.The forging process of rocker arm was analyzed based on the optimization design of its structure.The forging process for the rocker arm was simulated by rigid-plastic finite element method.The maximum stress and deviation of optimized rocker arm are 211.24 MPa、0.95 mm,and still smaller than its maximum allowable stress and deviation under the maximum load condition.The weight of optimized rocker arm was reduced 20.12%,which achieved the goal of optimization.The stress,strain,temperature field,and load curve of hammer were gained by rocker arm forming simulation.The forming die and the trimming die were designed based on the forging simulation,structural feature,and forging process of rocker arm.And the rocker arm was produced by forging hammer.Forging rocker arm filled fully,no visible flaws,the feasibility of the forging process was proved.This study provides theoretical basis for structural optimization of rocker arm and improvement of the actual forging process.