Effect of the internal pressure in the rubber mandrel on the defects of the rotary draw bending process

In this study, aluminum alloy 3003 tubes underwent a rotary draw bending process. The bending was conducted using a rubber–oil combination mandrel and a constant die at a critical bending ratio of 1 and an angle of 90°. Thereafter, the effect of oil pressure on defects, such as outer thinning and wrinkles in the inner portion of the bend, was investigated. Results showed that the thinning in the outer part of the bend and the wrinkling in the inner part of the bend decrease with the increase in the oil pressure. However, the likelihood of cracking in the outer portion of the bend increases at high pressure levels.