摘要
基于粒子群优化算法及Newton-Raphson迭代方法的数字图像相关粗-细搜索方法,该文观测了单向压缩砂样变形破坏过程中的变形场及侧向位移的分布及演变规律。该方法对于应变达到10%~15%时适用,对于位移的大小没有限制。研究发现,当载荷不大时,砂样的变形就变得不对称、不均匀,砂样一侧呈弧形,而另一侧呈S形。当狭窄的应变局部化带出现之后,在砂样两侧位于相同高度上,有的测点的水平方向位移发生了加速。位移矢量增量的演变经历了4个阶段：第1阶段为均匀的压缩变形阶段;在第2阶段,应变不均匀分布区内部的位移增量呈现连续的变化,属于非均匀的变形阶段;在第3阶段,应变局部化带两侧的点向相反的方向运动,而带内的位移增量基本向下;在第4阶段,应变局部化带一侧的点快速沿带发生错动,而另一侧的位移增量则不明显。随后,宏观剪切裂纹面马上形成。
For measuring the strain and displacement fields and the distribution and evolution of the lateral displacement of sand specimens under uniaxial compression during the deformation and failure processes,a digital image correlation method with coarse-fine search ability based on the particle swarm optimization algorithm and the Newton-Raphson method is used.The method is applicable for the case that the strain is in the range of 10%~15% and arbitrary magnitude of displacement.Under small loads,the asymmetric and non-uniform strain distribution within the specimen is observed.One lateral side of the specimen is arc,and another side exhibits an S-shape.After a narrow strain localization band with higher strains is generated,the horizontal displacements of some monitored points with the same height at two sides of the specimen rapidly increase.The evolution of displacement increments undergoes four typical stages.At the first stage,the deformation is compressive and uniform.At the second stage,the continuous displacement increment distribution is found within the zone where the strain is non-uniform.At the third stage,the deformation within the strain localization band is compressive and at its two sides of the band the displacement increment directions of points are different.At the fourth stage,at one side of the band,the displacement increment directions of points are parallel to the band and at another side the displacement increment is negligible.Thereafter,macroscopic shear fractures are formed.
出处
《工程力学》
EI
CSCD
北大核心
2013年第4期184-190,共7页
Engineering Mechanics
基金
国家自然科学基金项目(50974069)
国家重点基础研究发展计划项目(2010CB226803)
辽宁省高等学校优秀人才支持计划项目(LJQ2011030)
关键词
砂样
单向压缩
侧向位移
应变局部化带
非均匀性
数字图像相关方法
粗-细搜索方法
sand specimen
uniaxial compression
lateral displacement
strain localization band
nonuniformity
digital image correlation method
coarse-fine search method
