差厚拼焊管胀形减薄率不均匀性分析

Study on Nonuniformity of Thinning Ratio in Hydro-bulging of Tailor-welded Tubes with Different Thicknesses

结合有限元数值模拟和试验,研究差厚拼焊管胀形减薄率分布规律,并从应变状态和应变历史角度分析减薄率不均匀性产生的原因,进而研究厚度比、长度比及硬化指数n对减薄率分布的影响。结果表明差厚拼焊管胀形时薄、厚管不同部位始终处于不同的轴向应变状态,导致在发生相同的环向应变时,厚向应变分布不均。厚管愈靠近焊缝区域减薄率愈小,薄管愈靠近焊缝减薄率愈大。厚度比和硬化指数n对壁厚分布影响明显,厚度比越大、n值越低,胀形后薄、厚管的壁厚差越大;但厚度比影响主要集中在焊缝附近,n值影响整个胀形区的壁厚分布。

Thinning ratio distribution in hydro-bulging of tailor-welded tubes with different thicknesses are investigated by using Finite Element Method and experiment methods. Further, reasons of nonuniformity of thinning ratio and effects of thickness ratio, length ratio and strain-hardening exponent n on thinning ratio are investigated. It is revealed that due to the various axial strain and the same circumferential strain on the tube blank, the thickness strain is not uniform. On the thicker tube, the closer to the weld-seam it is, the less the thinning ratio will be. However, on the thinner tube, the closer to the weld-seam it is, the larger the thinning ratio will be. Thickness ratio and strain-hardening exponent n obviously influence the thickness distribution. The larger the thickness ratio and the less the strain hardening exponent n are, the larger the thickness difference between the thinner and the thicker tube will be. The thickness ratio mainly affects the thickness distribution near the weld-seam, while the strain-hardening exponent n affects the whole part.