MEASUREMENT AND ANALYZING SYSTEM OF DEFORMATION AND STRESS IN SOIL-BIN TEST

阐明土体的变形和应力状态对农业机械的研究具有重要意义。本文研究了通过观测土槽透明墙内的数百个标记物(直径约5 mm)的运动来测量土体变形的标记法的实际应用。本项目取得了以下成果：1.车轮行驶试验是在土槽中进行的，将细长的直杆埋入与标记相对应的位置。试验结束后，对标杆的位移和杆件的位移进行了比较。结论：1.在黑色圆心(直径5 mm)的中心印一个白色正方形(单边长1 mm)，背面有一个尖端的涤纶打标机是合适的。采用4,800个像素点排成一列的线移相机，并开发了图像分析软件，实现了对标记物位移的在线测量和显示表达，具有较高的精度。编制了应变增量和应变分布的自动计算程序，将标记位移代入相邻标记形成的三角形或正方形有限元的协调方程中。将应变增量代入到本课题组提出的土体弹塑性本构方程中，开发了次加载面模型的应力自动计算程序。

It is of importance for the study of farm machinery to elucidate state of deformation and stress in soils. The practical use of the marker method in which soil deformation is measured by observing the movement of several hundreds of markers (about 5 mm diameter) attached inside the transparent wall of soil-bin is studied in this research project. The following results are obtained in the project.1. The wheel traveling test was done in the soil-bin, burying thin straight rods in positions corresponding to markers. After the test the displacements of markers and those of rods are compared with each other. It is concluded that the polyester-made marker in which a white square (1 mm in one side) in the center of black circle (5 mm diameter) is printed and has a tip on the behind would be suitable.2. The on-line measurement and display-expression of marker displacements was realized with a satisfactory precision by using the line-shift camera in which 4,800 photo-elements are arranged in a line and developing the software for analyzing the pictures.3. The automatic calculation program for strain increment and strain distribution was made, in which marker displacements are substituted into the compatibility equation for the triangle or square finite elements formed by the adjacent markers.4. The automatic calculation program for stress was developed by substituting the strain increments into the elastoplastic constitutive equation of soils which is proposed by the head investigator and called the subloading surface model.