【作者】 胡宗文；

【导师】 王元清；

【作者基本信息】 清华大学 ， 土木工程， 2010， 硕士

【摘要】 国内建筑行业迅猛发展使得钢结构厚板的应用越来越广泛。钢板随着厚度的增大,其应力应变状态、中心偏析现象和可焊性等因素迅速恶化,导致其韧性变差。同时,寒冷地区的建筑业扩张使得结构钢材的低温冷脆现象日益突出。钢板厚度增大和低温环境二者共同作用则会造成钢结构脆性断裂的问题更加严重。本文对钢厚板的脆性断裂倾向进行了有限元分析,试验研究了钢厚板及连接焊缝低温下力学和韧性性能,总结影响规律,进而提出钢结构厚板防止脆性断裂的实用选材方法。主要研究内容和成果如下:（1）对60mm¹50mm厚Q345含缺口受拉厚板缺口尖端的弹塑性应力场进行了有限元和理论分析,获得了厚板缺口尖端应力场的分布规律,特别是对钢厚板的脆性断裂倾向性作了较深入的研究。（2）对60mm¹50mm厚Q345钢板进行了低温下力学性能试验（含Z向性能）、冲击韧性试验和三点弯断裂韧性试验,得到不同力学指标和韧性指标关于低温影响、厚度影响和沿厚度不同位置性能差异的变化规律,同时进一步研究了韧性指标的韧脆转变温度。（3）对150mm厚Q345钢板对接焊缝进行了低温下的冲击韧性和三点弯断裂韧性试验研究,得到焊缝区和热影响区的冲击韧性指标A_kv和断裂韧性指标CTOD有关低温影响和沿厚度方向性能差异的相关变化规律,进而对焊缝韧脆转变温度作进一步研究。（4）在冲击韧性试验结果的基础上,从低温的规定程度、厚度因素的影响以及韧脆转变温度这三方面对现有规范的钢结构防脆断选材方法进行了补充和完善;在断裂韧性试验结果的基础上,提出了钢厚板断裂安全性分级评定方法（按断裂韧性由好到差分为1、2、3三个级别）,并在此基础上定量化,得到基于断裂韧性指标的钢厚板防脆断定量选材方法。更多还原

【Abstract】 With construction industry developing rapidly in domestic, structural steel thick plate is used more and more widely. Thickness increase leads to the deterioration of stress and strain state, center segregation and weldability, which causes the toughness performance to get worse. Meanwhile, the construction expansion in the cold region makes more structural steels work at low temperature, which results in brittle fracture of structural steel thick plate more serious. This paper makes FEA analysis on brittle fracture tendency of steel thick plate, does an experimental study on the mechanical and toughness properties of steel thick plate and its butt weld at low temperature, and then puts forward selection methods of structural steel thick plate against brittle fracture. The main conclusions are as following:（1） This paper makes FEA and theoretical analysis on elastic and plastic stress field of the crack tip of 60mm-150mm Q345 thick plate in tension, obtains the distribution law of stress field of the crack tip, and especially studies on the brittle fracture tendency deeply.（2） This paper does experimental study on mechanical properties, impact toughness and fracture toughness of 60mm-150mm Q345 thick plate at low temperature, obtains the relevant variation of mechanical and toughness index with low-temperature effect, thickness effect and location difference along the thickness direction, and then researches into the ductile-brittle transition temperature of toughness index.（3） This paper does experimental study on impact toughness and fracture toughness of butt weld of 150mm Q345 thick plate at low temperature, obtains the relevant variation of A_kv and CTOD of weld area and heat-affect zone with low-temperature effect and location difference along the thickness direction, and then researches into the ductile-brittle transition temperature. （4） this paper, basing on impact toughness index (A_kv), supplement the current selection methods against brittle fracture of steel structures from three aspects: low temperature level, affect of thickness and ductile-brittle transition temperature; the paper also puts forward an evaluation method of fracture security level of steel thick plate basing on fracture toughness index （CTOD）, and after quantitative processing, finally gets an improved selection method against brittle fracture of steel thick plate.更多还原