| The outer cylinder of landing gear is the main load-bearing component of aircraft during takeoff and landing and commonly made of forging workpiece,it plays a crucial role in the safety of one flight.With the production of 800 MN hydraulic press in China,the production and processing of the outer cylinder of landing gear for large aircraft in the world began to transfer to China.The material of the outer cylinder Landing gear is generally ultra high strength steel,the forging temperature of this kind of material is high,the thermal effect on the mold is greater,because of some local structures overheating,the forging die often get softening and creep fatigue,which lead to huge losses to the enterprise.The structure of the outer cylinder of landing gear forgings is complex and it has many branch structures,so it is necessary to design a multi-station die forging process,if the design of intermediate workpiece is reasonable,the forging quality will be greatly improved,the forging die life,process stability will also be greatly improved.In this paper,the effects of two kinds of flash structures of mold on the final forging process are analyzed by using the forging finite element software DEFORM.Simulation experiment shows that,on the condition of the same flash bridge structure parameters,the storage bin of the flash on one side of the mold has greater metal flow resistance effect than the surge bin symmetrical distributed of flash structure,so in the same circumstance of die shut height,the surge bin in one side of the mold has bigger forging forming force and better filling property;As for the top and bottom die with big difference in stress and temperature,the design of storage bin on the mold of small stress and low temperature risen will balance the life of upper and lower die,so as to improve the mold life with high stress.The influence of the structural parameters of the mold flash on the forming process was analyzed,and the influence of the structural parameters of the flash on the forming performance of the forging,the maximum temperature of the die and the forging forming force was determined.By analyzing the three-dimensional shape of the blank and simulating the pre-forging process,the problems existing in the pre-forging process are found and summarized:(1)the blank design is unreasonable,the middle Convex platform is too high,and the blank processing is difficult;(2)the flash volume of pre-forming process is larger,which lead to waste of much material.By optimizing the design of blank twice,the convex block was changed from the original rectangular section to trapezoidal section,and the processing difficulty of blank was reduced.About 50 kg material is saved,which improve the utilization of raw materials.it is found that the blank has the characteristic of axial symmetry through the analyzing the structure of the blank.The forging process of blank can be subdivided into three steps: the first step is to compress the middle convex of the blank,the second step is to process the triangular part of blank,and the third step is to draw the length and square the blank.Through numerical simulation,the variable of the middle convex platform of the blank was determined,and the die closing height of the first anvil in the second step was optimized.Through theoretical calculation and numerical simulation,the first die closing height of the third step is determined.The minimum strain-effective of the blank was 0.204,the average strain-effective was0.814,and the blank deformation degree was uniform. |
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