Plotting isoclinics for hybrid photoelasticity and finite element analysis

Displacement-based finite element method formulations are coupled with stress-based photoelasticity analysis. As the stress field is discontinuous at the interelement boundaries, the introduced smoothing procedure enables the generation of high-quality digital images acceptable for hybird experimental-numerical techniques. The proposed methods are applicable for the analysis of static and dynamic results of experimental photoelasticity.     

光弹性五步彩色相移法分析初应力对等倾角的影响

通过琼斯矩阵推导出一般平面偏振场的受初应力影响的光强等式，选用有边缘效应的直边、斜边和曲边三种常见边界形状的光弹性模型，用五步彩色相移法分析了初应力对等倾角的影响，这对正确评价和执行实验技术都有着积极的作用。     

提取等倾线的数字图象处理法

本文详细介绍了应用数字图象处理技术进行图象相除和图象相减,获取没有等色线干扰的、精确定位的和倍增信息的等倾线的全场分析方法,并作了典型验证实验,为光测弹性力学的改革提供了途径和理论依据。     

Real-time analysis of isochromatics and isoclinics using the phase-shifting method

This paper studies a new real-time phase-shifting method for the analysis of isochromatic and isoclinic parameters in photoelasticity. By rotating an analyzer at a constant rate and an output quarter-wave plate at a double rate of the analyzer and recording images by a CCD camera continuously, sequential images which brightness is integrated by sensors in a CCD camera during phase-shifting are obtained. Then, the distributions of the isochromatic and isoclinic parameters are obtained immediately and quantitatively using the proposed phase-shifting algorithm. The proposed method can be applied to high-speed inspection of optical elements or glass products. Also, it is expected that slowly varying time-dependent problems can be analyzed by the proposed method.     

Photoelastic Stress Analysis by Use of Hybrid Technique and Fringe Phase Shifting Method

0Introduction Photoelasticityisanopticalmeasurementmethodforstressanalysis.Itcanperformwhole field measurementduetotwo dimensionalsignalprocessingoflight.Alsoitcanperformnon contact measurementbecauseoftransmissionorreflectionoflightonaspecimen.Photoelast…     

光弹塑性等倾线角度的判读一法

本文提出并证明了一套测定光弹塑性模型中任一点的等倾线角度的方法     

Theoretical analysis and digital photoelastic measurement of circular disks subjected to partially distributed compressions

The disk in diametral compression has been quoted most frequently on developing conventional/digital photoelasticity to illustrate new theories and experimental techniques for several decades. Theoretically, the compression as a concentrated force is more conducive to analysis, but it is impossible to achieve such loading condition experimentally. The distributed compression on a finite area at rim is relatively closer to actual testing and it is complicated to seek an analytical solution. In this paper, we extend the work of Hondros to derive the full-field stress distribution of disk subjected to diametral distributed compression in an explicit functional form. The principal stress difference and principal stress orientation related to isochromatic and isoclinic fringes, respectively, are also expressed in a simple closed form. The maximum shear stress for the whole disk and the validity of using isochromatic fringes to interpret the maximum shear stress are discussed in detail. The isoclinic fringes are compared with theory, and the fringe multiplication isochromatic is compared with simulated image. All of the comparisons are in good agreement with respect to full field.     

光强和方位角误差对光弹性五步彩色相移法的影响

为了了解相移法中的各种参数所产生的误差对最终结果的影响 ,对一些主要参数做深入的误差分析是十分必要的。针对五步彩色相移法所用的白光入射平面偏振场的特点 ,只考虑光强、起偏镜和分析镜方位角所引起的误差影响就可以了。提出一个分析和评估这些误差源对五步彩色相移法确定等倾角参数所产生影响的方法 ,这对合理设计实验装置和执行正确的实验条件将起到积极的作用     

数字光弹性中五步彩色相移法及其应用

把相移法与光学彩色信息图像处理技术相结合,提出全场数字化确定主方向角的光弹性五步彩色相移法。其主要优点是采用最简单的白光平面偏振仪光学系统,由数码照相机采集五幅等色线与等倾线相互耦合的彩色条纹图,经计算机进行处理后,就可以得到[O～π／2]范围内单纯连续的等倾角相图;为了减少测量误差,在相移法中引入背景光强参与运算。对实验中存在的三种主要误差因素进行了定量分析,给出了具体的误差控制指标。用对径压缩圆盘问题的理论仿真模拟结果、基本实验和复杂平面及空间实际问题进行检验和对比,表明本方法是正确可行的。     

全场数字化测量光弹性等倾角的五步彩色相移法

通过把相移法与光学彩色信息图像处理技术相结合 ,提出了一种确定全场光弹性等倾角的五步彩色相移法。模型置于白光照射下 ,在起偏镜与分析镜不同设置的平面偏振光场中 ,用彩色数码照相机分别采集五幅等色线与等倾线相耦合的条纹图 ,根据相移法基本原理 ,就可以确定在 0～π/2范围内的等倾角。经过对径压缩圆盘的检验 ,实验结果与理论完全相符。该方法改进了单色光相移法的不足 ,对实验应力分析及其在工程结构强度设计中的应用将起积极的促进作用