厚壁方矩形管冷弯效应对比分析

Comparative analysis on Strain Hardening of Thick-wall Cold Formed Steel Tube with Square and Rectangular Hollow Section

为了对厚壁型钢管的冷弯工艺改进、性能分析、结构强度设计和数值模拟结果的验证提供重要依据,进行了冷弯厚壁钢管上截取的平板件、弯角件、母材和相应方、矩形截面短柱的力学性能试验研究,获得了短柱全截面屈服强度相对于母材强度的提高值。分别运用北美等国厚壁冷弯型钢规范、国内薄壁冷弯型钢规范以及相关文献中的修正规范,对我国厚壁冷弯方矩形型钢管全截面强度进行设计和对比分析。结果表明:因冷弯工艺不同,国外公式计算的结果高于国内短柱实测值,国内厚壁冷弯型钢的强度设计不能照搬现有的国外厚壁冷弯型钢设计规范;国内薄壁公式能否适用要视型钢的冷作硬化效应程度决定;原料的强屈比和冷弯应变程度越大,则冷作硬化效应越大;焊接热使板件受到低温"退火"的作用不可忽略,其常常导致竖直配辊冷弯厚壁矩形型钢时,两竖直侧平板件强度低于母材。

In order to provide important data for technology improvement,character analysis,structural strength design and validation of numerical simulation of thick-wall cold formed steel tube,experiments concerning on mechanical properties of the flat portion,corner portion,virgin steel and full section stub columns were performed.Increased yield value of the whole cross section of stub columns caused by strain hardening was obtained accordingly.Strength gain from cold work was calculated by consulting the specifications in North American,China and reference [5] for the design of the cold formed steel structural members respectively.Comparative analysis was carried out on the calculated and measured strength values.Results show that the calculated strengths of stub columns by the specification made abroad are higher than the experimental data.This mainly owes to the difference of cold-forming technology between home and abroad.Specification established by North American isn＇t applicable for thick-wall cold formed steel tube in China,while whether that established by China can be directly applied to thick-wall cold-formed steel tube depends on strain hardening of the tube.The bigger ratio of strength to yield strength of virgin steel and deformation are,the bigger strain hardening is.Heating effect on the flat portion induced by welding usually reduces tensile strength of the flat portion bilateral to a value lower than that of virgin steel for vertically cold-formed thick-wall rectangular steel tube,and this can＇t be ignored.