摘要
Nb3Sn超导复合股线在强磁场工程中有着重要的应用,其拉伸强度为保证和评估其长期服役安全的一个关键参数.论文从＂剪滞＂理论出发,利用基于Weibull/Possion统计理论的复合材料纤维断裂的Curtin-Zhou模型,较好地描述复合股线中Nb3Sn超导纤维碎片化过程,建立了分析超导复合股线统计拉伸强度和失效概率的模型.计算结果表明,青铜法Nb3Sn超导复合股线的拉伸强度随着初始损伤参数的增大而迅速减小;在4.2K服役温度下,当Weibull模量为8时,随着初始损伤参数的增加,股线的拉伸强度约从900MPa衰减至480MPa,与已有实验结果吻合良好;初始损伤参数约为1时,正规化方差最大.初始损伤和Weibull模量对Nb3Sn复合股线统计拉伸强度和失效概率函数的分布有着显著影响.
Nb3Sn superconducting composite strands have wide applications in high magnetic field engineering,and their tensile strength is a key parameter to assure and assess safety during long-time service.In this study,on the basis of the Curtin-Zhou model developed from the shear-lag theory combined with Weibull/Poisson statistics,the fragmentation of filaments in the inner layer of Bronze-processed Nb3Sn superconducting composite strand can be well described under the assumption of global load sharing,and an analytical model is proposed to obtain the statistic tensile strength and failure probability of these stands.In the present model,considering the brittleness of Nb3Sn compounds,the initial damage in the form of filament fracture,which can be easily caused due to the multi-step thermal treatment and forming process,is accounted for by aparameter in the damage evolution equation,and the influence of the initial damage parameter on the statistic tensile strength and the statistic variance as well as the failure probability is analyzed in detail.In addition,the effect of Weibull modulus on these statistic properties is also discussed sufficiently.The computation results show that when the initial damage parameter is increased,the statistic tensile strength drops sharply;and at the service temperature of 4.2 K,when Weibull modulus is equal to 8,the tensile strength decreases from 900 MPa to about 480 MPa,which coincides well with the experimental results;furthermore,as the initial damage parameter is nearly 1,the normalized variance reaches its maximum value.This research indicates that both the filament initial damage and Weibull modulus have strong influences on the statistic tensile strength and failure probability of Nb3Sn superconducting composite strands.The present analytical model is convenient for engineering applications and can provide a certain theoretical guidance for evaluating the safety and stability of ITER superconducting magnets.
作者
罗威
李飞
王梅
田东方
Wei Luo;Fei Li;Mei Wang;Dongfang Tian(College of Hydraulic and Environmental Engineering, China Three Gorges University, Yichang , 44300)
出处
《固体力学学报》
CAS
CSCD
北大核心
2018年第2期182-188,共7页
Chinese Journal of Solid Mechanics
基金
国家自然科学基金青年项目(11302119)资助
