Generation of forming limit curve of Ti-6Al-4V alloy sheet by various methods and loading conditions

The use of titanium alloys, which stand out with their superior properties such as high strength, thermal stability, and corrosion resistance, has become widespread in industrial applications in the last two decades. Ti-6Al-4V draws attention as the most widely used type among titanium alloys. Ti-6Al-4V alloy is used in critical applications such as gas turbines in the energy and aviation industries, and joint implants in the medical field. In this master's thesis, the forming limit curve (FLC) of Ti-6Al-4V alloy, which has limited formability at room temperature, was produced. Two different methods including the Nakajima and the hydraulic bulging tests were used in the process. Pulsating, which is known to increase formability, was also used during the hydraulic bulging tests. The FLC found by the hydraulic bulging test shifted upwards by 23.7% when pulsating was applied. In addition, it was observed that the FLC produced by the Nakajima test reached higher levels than the one from the hydraulic bulge test, and the reasons for this were investigated by running a case study. It has been seen that damage is delayed due to friction in the Nakajima test. Cylindrical parts were made by female-die hydroforming, in which friction is dominant, and strain distribution was measured on these parts. These strain measurements confirmed the Nakajima test FLC. Spherical domes were fabricated by hydraulic bulge method to verify the FLC determined by the hydraulic bulge test. This process was performed with both monotonous and pulsating loading. The measured strain distributions were examined, and the results confirmed the FLC obtained by the hydraulic bulge test. In addition, the strain distributions of the spherical dome produced with pulsating loading increased as in the FLC obtained with pulsating loading. Consequently, the Nakajima test FLC is usable in sheet metal forming processes with dominant friction effects, the FLCs developed by the hydraulic bulge tests are valid for hydroforming processes and pulsating forming provides a significant increase in formability.