Simulation and Experimental Study on a New Successive Forming Process for Large Modulus Gears

A successive tooth forming process for producing large modulus spur gears(m>2.5 mm)is firstly proposed in this paper to break the restrictions of large forming load and large equipment structure of traditional plastic forming.It contains the preforming stage and the finishing stage.In the first stage,the die with a single-tooth preforms gear teeth one by one through several passes.In the second stage,the other die with multi-teeth refines the preformed teeth into required shape.The influence of total pressing depth and feed distribution in preforming stage on final forming quality is analyzed by numerical simulation,and the reasonable process parameters are presented.Successive tooth forming experiments are carried out on the self-designed gear forming device to verify the optimal simulation results.Gears without fold defects are well formed both in simulations and experiments,proving the feasibility of this method.Compared with the whole die forging process,the new technology has advantages of smaller load and simpler tooling,which shows a good potential for manufacturing large modulus and large size spur gears.

Unequal-thickness billet optimization in transitional region during isothermal local loading forming of Ti-alloy rib-web component using response surface method

Avoiding the folding defect and improving the die filling capability in the transitional region are desired in isothermal local loading forming of a large-scale Ti-alloy rib-web component（LTRC）. To achieve a high-precision LTRC, the folding evolution and die filling process in the transitional region were investigated by 3 D finite element simulation and experiment using an equal-thickness billet（ETB）. It is found that the initial volume distribution in the second-loading region can greatly affect the amount of material transferred into the first-loading region during the second-loading step, and thus lead to the folding defect. Besides, an improper initial volume distribution results in non-concurrent die filling in the cavities of ribs after the second-loading step, and then causes die underfilling. To this end, an unequal-thickness billet（UTB） was employed with the initial volume distribution optimized by the response surface method（RSM）. For a certain eigenstructure, the critical value of the percentage of transferred material determined by the ETB was taken as a constraint condition for avoiding the folding defect in the UTB optimization process,and the die underfilling rate was considered as the optimization objective. Then, based on the RSM models of the percentage of transferred material and the die underfilling rate, non-folding parameter combinations and optimum die filling were achieved. Lastly, an optimized UTB was obtained and verified by the simulation and experiment.