An experimental study on dimensional accuracy, surface quality, and hardness of Ti-6Al-4 V titanium alloy sheet in hot incremental forming

In this study, an electrical heater device that employs alternative electrical current was designed and used to perform the sheet incremental forming process at elevated temperatures. The main advantage of the new device over the existing designs is the use of alternate current electricity which makes the process safer for the operator, requires less expensive equipment, and is more available than the direct current electricity. In this device, the electrical current passes through the tool and generates the maximum heat at the sheet-tool interface. The device was mounted on an incremental forming setup, and the temperature was measured during the forming process. The temperature measurements showed that the device was able to effectively raise the sheet temperature. Furthermore, Ti-6Al-4 V sheets were incrementally formed into a few basic important shapes: conical frustum, variable wall angle conical frustum, and pyramidal frustum. The effect of different process parameters on the dimensional accuracy, surface quality, and workhardening of the fabricated workpieces was studied. The results showed that the highest deviation from ideal geometry occurs at the workpiece tip, and it considerably decreases a few millimeters away from the tip. In addition, the roughness of the inner surface where the tool contacts the workpiece is greater than the outer surface. Micro-hardness test results also showed that the hardness increased from flange to vertex of the workpiece where larger plastic deformation and hence more workhardening is expected to occur.