尺寸效应对固支直杆弯曲小试样蠕变性能评价的影响  

Effect of Specimen Size on the Creep Property Evaluation of Small Beam Specimen with Fixed Constraints

作　　者：王俊崎 余海洋 周帼彦[1] 王琼琦[1] 涂善东[1] Wang Junqi;Yu Haiyang;Zhou Guoyan;Wang Qiongqi;Tu Shantung(Key Laboratory of Pressure System and Safety(MOE),School of Mechanical and Power Engineering,East China University of Science & Technology,Shanghai 200237,China)

机构地区：[1]华东理工大学机械与动力工程学院承压系统与安全教育部重点实验室,上海200237

出　　处：《压力容器》2019年第1期1-9,23,共10页Pressure Vessel Technology

基　　金：国家自然科学基金项目(51675181);上海材料基因组工程研究院资助项目(16DZ2260604)

摘　　要：小试样蠕变技术在设备材料蠕变性能评估中具有潜在优势。固支直杆弯曲小试样蠕变方法因受力简单且能获得断裂数据而备受关注。由于固支直杆小试样相较于传统单轴拉伸试样十分微小,目前缺乏对其试样尺寸的标准化研究,使其工程应用受到很大局限。基于固支直杆小试样梁弯曲本构模型,采用有限元方法,模拟分析了不同试样横截面宽厚比和固定端结构尺寸下固支直杆弯曲小试样蠕变性能情况,进而与单轴试验结果对比得到与传统蠕变试验关联性最好的试样尺寸。研究结果表明,当试样横截面的宽厚比b∶2h在0. 5～2. 0范围内时,蠕变稳态位移速率与理论值误差较小;当固定端过渡段倾斜角在15°～45°之间时,试样不仅可以很好地描述固支直杆弯曲蠕变的力学响应,还能明显降低固定端倒角对蠕变的影响。最后得到两种与传统蠕变试验关联性最好的试样尺寸,分别为横截面宽厚比b∶2h=2∶1、过渡段倾斜角为30°和横截面宽厚比b∶2h=1∶1、过渡段倾斜角45°。Small specimen creep test has potential advantages in the creep property evaluation of equipment materials.Small beam specimen with fixed constraints has attracted much attention because of its simple stress and ability to obtain rupture data.As the small specimen is very small compared with the standard tensile specimen,there is a lack of standardization research on the specimen size,which greatly limits its engineering application.Therefore,based on the bending constitutive model of small beam specimens with fixed constraints,the influence of different ratio of width to thickness of the cross section and fixed end structure size on the creep property evaluation of the small beam specimen with fixed constraints was investigated using finite element method.Compared with the uniaxial test,the structure of the small specimen with the best correlation with the traditional creep test was obtained.The research results show that when the ratio of width to thickness of the cross section b∶2h was in the range of 0.5~2.0,the error between the creep steady displacement rate and the theoretical value was small.When the transition angle of fixed end was in the range of 15°~45°,the specimen not only could describe the mechanical response of bending creep of clamped beam more accurately,but also could significantly reduce the effect of fixed end chamfering on creep.Finally two types of specimens with best correlation with traditional creep tests were the one with the ratio of width to thickness b∶2h=2∶1 and the transition angle of 30°of the fixed end and the one with the ratio of width to thickness is b∶2h=1∶1 and the transition angle of 45°of the fixed end.

关 键 词：固支直杆 小试样 蠕变 尺寸效应 小变形 

分 类 号：TH142[一般工业技术—材料科学与工程] TH49[机械工程—机械制造及自动化]