【作者】 雷振坤；

【导师】 云大真；

【作者基本信息】 大连理工大学 ， 固体力学， 2002， 博士

【摘要】 用光弹性实验处理实际问题时，在数据自动采集与处理中，如何获得单纯等倾线的问题仍是一大难点，此外就是如何进一步提高三维冻结模型薄切片的等色线定级精度问题也比较困难。根据白光入射时应力模型在偏振仪光学系统中的等色线条纹是彩色的特点，本论文采用彩色数码相机作为数据采集与输入设备，结合彩色信息图像处理和BP神经网络等新技术，对上述两个难题进行了系统的研究，获得以下成果： 在综合前人工作的基础上，提出获得全场单纯的等倾角相图的五步彩色相移法。其特点是在白光入射下平面偏振仪光学系统中，用彩色数码相机采集包括背景光强在内的不同偏振场设置下的五幅彩色图像，通过运算就可以得到[0—π/2]范围内的等倾角。用计算机仿真模拟和实验验证以及用复杂二维和三维工程应用问题作对比，可知本方法比其它方法要好。 在五步彩色相移法确定等倾角的过程中，主要误差源有起偏镜或分析镜的方位角不准确、模型因边缘效应而产生的初应力和平面偏振仪光学系统中的光强变化。本文提出它们影响五步彩色相移法的定量误差分析方法；提出控制各误差的具体指标；给出了避免或降低这些误差源影响的措施，为合理设计制造仪器、指导实验和保证实验结果的精度提供了依据。顺便指出，本文所提出的误差分析方法，对光弹性相移法都具有普遍意义。 提出基于BP神经网络的彩色域等色线自动定级法。其特点是通过BP神经网络建立图像中像素点的R、G、B颜色值与条纹级数N之间的非线性关系；可以准确地得到3级以内等色线条纹级数。本方法对提高条纹稀疏且无零级等色线的三维应力冻结模型薄切片的定级精度有重要作用。 要采用计算机自动处理光弹性条纹图像，仅有各种条纹图像分析处理算法是不够的，而必须将算法编制于软件之中。本文开发形成一套与计算机设备无关的数字光弹性图像处理软件，用来实现本文提出的数字光弹性方法。附加功能还有对径压缩圆盘理论仿真模拟、各种误差分析、相位去包裹和图像信息实时显示等，它为今后进一步开发奠定基础。更多还原

【Abstract】 In automatic acquisition and procession of the photoelastic data, there are some troubles about how to acquire single isoclimcs and to improve the precision of evaluating isochromatic fringe orders in the thin slice of the three-dimension model when the actual problems are solved by photoelasticity. Because color isochromatic fringes appear in the stress model based on a plane polariscope in white light, we studied the problems systematically by a digital camera as image inputting device, digital image processing technique and BP artificial neural network.Based on the work that has been reported before, a technique named five-step color phase shifting technique (FCPST) to acquire single isoclinics is presented. Relevant theory is derived and explicit conditions for directly determining the isoclinic parameter in the range of [0- 3i /2] are given. A color camera records five isoclinic images coupled with isochromatics from a plane polariscope with five different settings in white light, respectively. Computer simulations and experiments have been carried out with a circular disk under diametral compression and complex two-dimension and three-dimension engineering application problems. The results prove that the FCPST is better than the other phase shifting techniques (PST).Three main error sources are the variation of intensities, the orientation errors associated with the configurations of the polariscope and the initial stress existing in the model. A quantitative method is presented to analyze and estimate the influence of different error sources on the final isoclinic results calculated by FCPST or the other PST. Some guidelines and measures to control and decrease the influence of the errors on the results are given.An automatic order determination of color isochromatic fringe based on BP artificial neural network is presented. The complex function between isochromatic fringe orders and RGB gray values of the image pixels is described by BP artificial neural network. The technique can improve the precision of experimental stress analysis in three-dimensional photoelastic thin slices.In order to reduce photoelastic data from the digitized fringe image and to avoid the repetitive work, a photoelastic digital imaging software independent device is presented. Thesoftware has realized the techniques presented before and has other functions, such as the simulation of a disk under diametral compression, various error analysis, phase unwrapping, real-time display of image information, and so on.更多还原