实时三维数字图像相关方法在材料力学教学中的应用1)

*东南大学土木工程学院,南京 210096

APPLICATION OF REAL-TIME 3D-DIC METHOD IN TEACHING MATERIAL MECHANICS1)

SHAO Xinxing,*,2), CHEN Jie*, MA Qinwei, HE Xiaoyuan*

*School of Civil Engineering, Southeast University, Nanjing 210096, China

School of Aerospace Engineering, Beijing Institute of Technology, Beijing 100081, China

 基金资助: 1)国家自然科学基金资助项目(11902074)国家自然科学基金资助项目(11827801)

Abstract

Experimental teaching is a crucial part of education in science and engineering colleges. To improve students understanding of theoretical knowledge substantially, it is of great significance in applying modern optical mechanics methods in experimental teaching. As two examples, this article carried out aluminum alloy tensile experiment and three-point bending experiment of beam model, using self-developed real-time three-dimensional (3D) digital image related methods to display teaching contents. This method can measure the three-dimensional shape and deformation of the surface of an object in real time, and intuitively reveal the deformation laws and mechanics principles in material mechanics. Practice shows that classroom presentations mobilize students' enthusiasm, and the combination of theory and experiment increase students' ability in analyzing problems. Compared with traditional electrical measurement methods, it has incomparable advantages.

Keywords： real-time three-dimensional digital image related methods; tensile experiment; three-point bending; experimental teaching; full-field measurement

SHAO Xinxing, CHEN Jie, MA Qinwei, HE Xiaoyuan. APPLICATION OF REAL-TIME 3D-DIC METHOD IN TEACHING MATERIAL MECHANICS1). MECHANICS IN ENGINEERING, 2021, 43(5): 776-782 DOI:10.6052/1000-0879-20-465

1 原理简介

1.2 相机标定

$Z_{C}\left[ {\begin{array}{*{20}c}x\\y\\1\\\end{array} } \right]=\left[ {\begin{array}{*{20}c}F_{x} & F_{s} & C_{x}\\0 & F_{y} & C_{y}\\0 & 0 & 1\\\end{array} } \right]\left[ {\begin{array}{*{20}c}X_{C}\\Y_{C}\\Z_{C}\\\end{array} } \right]={ A}\left[ {\begin{array}{*{20}c}X_{C}\\Y_{C}\\Z_{C}\\\end{array} } \right]$

图2

$T_{1\mbox{-}2}\cdot T_{w\mbox{-}1}= T_{w\mbox{-}2}$

1.2 三维数字图像相关方法

3D-DIC系统的硬件部分主要由相机、光源、三脚架和计算机组成。如图4所示。

2 教学实验步骤

(1)准备教学试样

(2)粘贴水转印[10]散斑并安装试样

(3)架设相机并调节相机参数

(4)相机标定

图10

(5)设置计算参数后进行加载和实时计算

(6)结合变形场数据学习材料力学基本方程

(7)实验报告撰写

3 实验和教学效果分析

3.1 铝合金拉伸实验效果

$\Delta l=\frac{F_{\rm N}l}{EA}$
$\varepsilon =\frac{\sigma }{E}=\frac{F_{\rm N}}{EA}$

3.2 梁模型的三点弯实验效果

$w=\frac{Fx}{48EI}(3l^{2}-4x^{2})\ \ (0\leqslant x\leqslant {l}/{2})$

4 结论

(1) 效果直观：实时三维数字图像相关方法直观地展示了实验过程中被测物的形变情况,在教学过程中可以根据变形实时地分析梁的受力状况,培养了学生进行受力分析的能力;

(2) 耗时短：在实验教学环节的工作中,与传统测量方法相比,省去了粘贴应变片和数据分析环节,缩短了实验周期;

(3) 操作简便：实验装置易操作,设备架设方便,上手快,散斑粘贴、相机标定、计算参数设定等均易操作。

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