【作者】 朱爱珠；

【导师】 郭耀杰； 李正农；

【作者基本信息】 武汉大学 ， 结构工程， 2004， 硕士

【摘要】 钢材经过冷作硬化成型后，材料屈服强度会有明显的提高。而且，冷弯型钢作为经济型材，被越来越广泛地应用于工程实际中。我国现行《冷弯薄壁型钢结构技术规范》中考虑冷弯效应强度提高的设计公式，仅限于壁厚不超过6mm的冷弯薄壁型钢，对于厚壁情形则未能提出相应公式。目前，对于冷弯厚壁型钢冷弯效应的研究还比较少见。 本文通过对一系列冷弯方(矩)形管中截取的板件、短柱以及相应母材的冷弯效应进行系统试验，研究冷弯厚壁型钢冷弯效应对钢材强度、延伸率等力学性能的影响。其中，冷弯方(矩)形管中截取的板件包括平板和弯角板件两种；各种试件的壁厚有三种，分别为8mm、10mm和12mm。首先，通过板件的材性试验得到冷弯效应局部(弯角和平板)板件的强度提高。然后，运用国内外现行的相关规范公式计算方(矩)形管的全截面屈服强度，并将此计算值与短柱轴压试验的强度实测值作对比分析。最后，提出对我国《冷弯薄壁型钢结构技术规范》中，考虑冷弯效应强度提高的计算公式的修正函数，得到适用于我国冷弯厚壁型钢考虑冷弯效应强度提高的计算公式。进一步，通过大量反演计算，说明了该公式的适用范围较广泛，同时也证明了该公式的准确性与可靠性。 冷弯过程中产生的冷弯残余应力将对构件的刚度和稳定性造成不利影响。本文把冷弯加工过程分解成弯曲(加载)和回弹(卸载)两个过程分别加以分析。在冷弯效应试验研究的基础上，考虑材料经过冷作硬化过程强度的提高，得到弯曲过程的弯曲应力场；运用大型有限元软件ANSYS计算分析得到弯曲件的回弹应力场，将两个过程中产生的应力场迭加，得出合理又全面的冷弯厚壁型钢冷弯残余应力分布规律。 本文提出的考虑冷弯效应强度提高的厚壁型钢强度计算公式，可为钢结构规范中增加相关条文提供参考；本文提出的冷弯厚壁型钢考虑硬化后的残余应力分布，可作为进一步研究残余应力对构件稳定性及刚度不利影响的基础。更多还原

【Abstract】 Steel materials will be obviously hardened after the cold-formed process. And as kind of most economical formed material, cold-formed steel members are used in practical engineering more and more widely. In the existing code-Technical Code of Cold-Formed Thin-Walled Steel Structures, after considering the hardening of the cold-formed process, the strength design formula is only used for cold-formed thin-walled steel members, which means that the thickness of steel members is no larger than 6mm. However, the relational formula for thick-walled steel members has not been brought forward. Also, investigations of cold-formed effect on thick-walled steel members have been seldom reported.In this thesis, based on many experiments on wattles, stub columns and relational raw material, cold-formed effect of thick-walled steel members on the mechanical properties including strength, ductility, and so on, are studied respectively. The wattles and stub columns are all cut from cold-formed square (or rectangular) steel tubes. The wattles include flats and corners. Each kind of test samples has three thickness, they are 8mm, 10mm and 12mm respectively. Firstly, according to the experiments of wattles, the hardened strength of flats and corners are gained by considering the cold-formed effect. Then, based on the data results of flats and corners, correlative codes used overseas and in China are applied to calculate yield stress of the overall cross section of square or rectangular tubes. Also, the results of each calculation method and the results of the stub columns’ tests are compared and analyzed. Lastly, in order to gain a proper design formula in which the cold-formed effect on thick-walled steel members is considered, a modify function for the existing design formula in Technical Code of Cold-Formed Thin-Walled Steel Structures is brought forward. Furthermore, so many back calculations are made, which explains that the modified formula can be applied in rather wide areas. Also, veracity and reliability of the modified formula are also proved.Cold-formed residual stress resulted from the cold-formed process is a disadvantageous factor for stiffness and stability of steel members. In this thesis, the cold-formed process is divided into two stages: the being formed (or member’s loading) stage and the elastic restoration (or member’s unloading) stage. Based on the experimental results of the cold-formed effect, considering the hardening of steel members, stress fieldof the being formed stage is obtained. Then, using the ANSYS-finite element analysis software to imitate the elastic restoration stage, stress field of this stage is obtained, too. The reasonable and comprehensive cold-formed residual stress field of thick-walled steel members is achieved by adding the stresses of those two stages.After considering the effect of the cold-formed process, the strength design formula for cold-formed thick-walled steel members brought forward in this thesis provides advice for steel structure code to add relational content. Meanwhile, by thinking about the hardening, the residual stress field put forward in this thesis is also a foundation for further study on the disadvantageous effect of cold-formed residual stress to structures’ stability and stiffness.更多还原