Construction of 6061-T6 aluminum alloy constitutive model based on hot bulging test and study on the non-isothermal hydroforming process

摘要

Due to the high requirements of drawing equipment and process, it is relatively rare in the field of aluminum alloy sheet forming to introduce soft or sticky fluid medias as soft mold into the course of hydroforming with a non-isothermal condition that maintaining the temperature of high pressure liquid differs to the ones of molds. Consequently, in this paper, the material stress-strain curve in the temperature range is obtained by the bidirectional tensile hot bulging test which contains compress to sheet's thickness, and can best meet the characteristics of non-isothermal hydroforming in mechanics compared with unidirectional hot stretching. Based on analysis of stress-strain of 6061-T6 aluminum alloy, its constitutive equation on the basis of an original model of processing hardening rate is established for finite elements numerical simulation, and a highly accurate setting range of forming temperature can be confirmed to provide guidance for practical manufacturing accordingly. Result of the study suggests, by applying the constitutive model mentioned above, simulation on non-isothermal hydroforming can reach a desirable effect; The non-isothermal condition set reasonably causes an enhance to the junction of straight wall and round corner, and a deduce of thickness reduction rate simultaneously, limit height increases as a result. Besides, the fluency of blank located in the flange improves to a great extent when its temperature is well set. The position of the 1 mm wall thickness constant line of the workpiece is further reduced, so that the forming quality of the workpiece is remarkably improved.