Optimal energy distribution in hydraulic hammer forging for minimizing total energy and forging load

Abstract

Hammer forging is an important manufacturing technology in heavy industry to produce high stiffness product. Forging using mechanical press produces the product by controlling the distance between dies whereas the hydraulic hammer forging utilizes the energy given by the sum of hydraulic energy and potential energy of die, and the product is then produced through several blows. The energy at each blow is conventionally determined through the trial-and-error method. The process to produce the product is simple and the response of hammer foundations and anvil is mainly discussed in the literature, but the optimal energy distribution to successfully produce the product is rarely discussed. In this paper, the optimal energy distribution in hydraulic hammer forging is determined using numerical simulation coupled with design optimization technique. To determine the optimal energy distribution through the process, multi-objective design optimization for minimizing both the total energy and the maximum forging load is performed. High dimensional accuracy is generally required in the forged product, and the underfill is handled as the design constraint. The numerical simulation in hydraulic hammer forging is computationally so expensive that sequential approximate optimization that response surface is repeatedly constructed and optimized is adopted to identify the pareto-frontier between the total energy and the maximum forging load. It is clarified through the numerical result that the total energy is drastically reduced without the underfill in comparison with the conventional one. The experiment is also conducted to examine the proposed approach.