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

阐明土壤的变形和应力状态对农业机械的研究具有重要意义。本课题研究了标记法的实际应用，该方法是通过观察附着在土仓透明壁内的数百个标记（直径约5mm）的运动来测量土壤变形。在该项目中获得了以下结果：在土仓中进行车轮行走试验，在相应标记的位置埋设细直杆。试验结束后，将标尺位移与棒材位移进行对比。结果表明，在黑色圆圈（直径5毫米）的中心印上一面为1毫米的白色正方形，背面有一个尖端的聚酯制标记是合适的。利用4800个像元排成一条线的线移相机，开发了图像分析软件，以满意的精度实现了标记位移的在线测量和显示表达。3 .编制应变增量与应变分布的自动计算程序，将相邻标记构成的三角形或方形有限元的标记位移代入相容方程。将应变增量代入首席研究员提出的土弹塑性本构方程，即下加载面模型，开发了应力自动计算程序。

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.