A novel expansion forming process using soundless chemical demolition agent

Abstract

In this research, the volumetric expansion of soundless chemical demolition agent (SCDA) is proposed in sheet metal forming. First, a proper set-up was prepared to evaluate the volumetric expansion behavior of SCDA as a function of the ambient temperature, the water content in the mixture and the mixture weight. Expansion onset time and the volumetric expansion of SCDA were considered as the output parameters. Then, according to the obtained optimum values for the process parameters, a closed die was designed to test the capability of SCDA in sheet metal forming. Dome shaped parts made of St12 were produced and compared with Nakajima and hydraulic bulge tests. The results indicated that an increase in the ambient temperature from 25 ºC to 75 ºC led to an improvement in the volumetric expansion and the reduction in the expansion onset time. The increase of water content from 25% to 35% led to a reduction in the volumetric expansion and an increase in the expansion onset time. A rise in mixture mass from 100 g to 300 g improved the volumetric expansion, but decreased the expansion onset time. The forming limit diagram (FLD) was obtained through the Nakajima standard test. Moreover, comparing the similar strain paths, it was found that the dome-shaped parts can be produced by the proposed method with the most strain biaxiality. The application of the suggested methodology allows for greater strain values compared to those anticipated by the conventional Nakajima test prior to failure.