锅炉弯管缠绕式冷弯成形工艺及其回弹的数值模拟

建立了锅炉弯管缠绕式冷弯成形的有限元数值模拟模型,对管子绕弯成形工艺的预压变形补偿、缠绕弯曲成形和释放模具后的回弹三个阶段进行了系列全面的模拟计算.分析得到了管子弯曲后的应力及塑性应变分布特点,管子弯曲椭圆度和减薄率随着顶镦力和预压量等不同弯制参数的变化规律,管子壁厚对弯曲成形质量的影响,管子弯曲成形的回弹特性等.研究表明:弯曲应力主要集中在弯曲起弯段;对于一定的管子规格存在顶镦力的一个最优值,使得管子的弯曲质量最为理想;相对壁厚大的管子弯曲质量较好;管子回弹角约为0.05rad,相对壁厚对其无明显影响.

Numerical Simulation for Twisting Cold Bending Process and Spring-back of Boiler Pipe

A FEM simulation model for twisting cold bend forming of boiler pipe was established.The three processes of pipe bend forming were simulated by the numbers in the round,including prepressing for deformation compensantion,twisting bending and deformation spring-back of pipe after releasing mould.Many significant aspects for boiler pipe bending were analyzed,comprising the distributing characteristics of stress and plastic strain of pipe after bending;the effects of different forming parameters such as boost force and prepressing value on the cross-section ellipticity and the ratio of wall-thickness reduction of pipe after forming;the bending results comprising of several load-cases in which the relative wall-thickness of pipe model were different and the spring-back law of pipe bending.It showes that: the bending stress of pipe mainly concentrated on initial portion of bending before spring-back;there was an optimum value of the boost force that makes the bending quality of pipe optimal;the bigger the value of the relative wall-thickness of pipe was,the better the bending forming of the pipe was;the spring-back angle of pipe bending approximated 0.05rad,which was independent of the relative wall-thickness of pipe.