摘要
正确认识不同数字图像相关(DIC)方法的应变计算结果的差异有助于该方法的正确使用。岩土材料变形破坏过程中应变场的准确测量对于正确认识岩土材料的变形破坏机理具有重要的意义。利用自主研制的平面应变模型加载及观测系统,在垂直方向位移控制加载条件下开展了平面应变含孔洞土样(受内压和侧压作用)变形破坏过程实验研究。利用两种DIC方法(即中心差分方法和局部位移场最小二乘拟合方法)计算了应变场。与此同时,还根据清晰剪切带所处位置布置了曲折测线,并在其两侧布置了平直测线,详细地比较了两种DIC方法的应变计算结果的差异。发现了下列结果:随着纵向应变的增加,含孔洞土样最大剪切应变的分布由均匀分布向不均匀分布转化,并最终导致含孔洞土样发生贯穿土样的剪切破坏;2条平直测线上最大剪切应变不相等,剪切带内变形程度大于带外。利用局部位移场最小二乘拟合方法能较好地获得含孔洞土样孔洞表面附近的应变,当计算窗口=5×5个点时,应变更准确、平滑性更好,而利用中心差分方法获得的应变误差较大,且无法获得土样孔洞表面附近的应变。
Strains obtained by different digital image correlation(DIC)methods are different.To use the DIC method accurately,it is necessary to obtain a full understanding of differences of strains obtained by different DIC methods.Accurate measurements of strains during the deformation and failure process of geomaterials are especially important to obtain the deformation and failure mechanism accurately.Using the developed loading and measuring system for the plane strain model,measurements of the deformation and failure process of clay specimens with holes in plane strain are conducted under displacement-controlled loading in the vertical direction,in which clay specimens are subjected to internal and lateral pressures.The least-square fitting of the local displacements and the central difference method are used to calculate strains.Meanwhile,the monitored curve lines are arranged according to positions of clear shear bands,and monitored straight lines are arranged at both sides.Differences of two kinds of methods mentioned above are studied in detail.The following results are found.With an increase of the longitudinal strain,the distribution of the maximum shear strain becomes non-uniform from uniform.Eventually,clay specimens are subjected to intersecting failures.The maximum shear strains at two straight monitored lines are different.Strains in shear bands are greater than that outside shear bands.Using the least-square fitting of the local displacements strains in the vicinity of the hole surface can be accurately measured,and when the calculating window includes 25 points,strains are smooth and accurate.However,strains in the vicinity of the hole surface can’t be measured using central difference method,and the errors of strains are great.
作者
王学滨
张博闻
董伟
侯文腾
Wang Xuebin;Zhang Bowen;Dong Wei;Hou Wenteng(Institute of Computational Mechanics,Liaoning Technical University,Fuxin,Liaoning 123000,P.R.China;College of Mechanics and Engineering,Liaoning Technical University,Fuxin,Liaoning 123000,P.R.China)
出处
《地下空间与工程学报》
CSCD
北大核心
2020年第2期567-576,共10页
Chinese Journal of Underground Space and Engineering
基金
国家自然科学基金(51874162)
辽宁省百千万人才工程(2017)。
关键词
数字图像相关方法
中心差分方法
局部位移场最小二乘拟合方法
剪切带
含孔洞土样
应变
破坏过程
digital image correlation method
central difference method
least-square fitting of the local displacements
shear band
clay specimen with holes
strain
failure process
