A study of the dynamic nolophotoelasticity light rotation method

A method which allows simultaneously separating the isochromatia and isopachic fringes for transient plane-stress problems is presented. A set of double pulsed ruby laser and a terbium glass Faraday rotator are used. The double-order timing methods applied in the synchronous system of the impact load and trigger cine jit. Separated fringe patterns of a structure component are recorded a nine different instants after impact loading, and the dynamic material-fringe values of isochromatics and isopachics are obtained by experiment. Finally, dynamic stresses distributed along a section at different instants are resolved.     

Photoelastic experimental hybrid method for fracture mechanics of anisotropic materials

In this paper, the isotropic and anisotropic photoelastic experimental hybrid methods for fracture mechanics are developed. Using the photoelastic experimental hybrid method, it is demonstrated that one can precisely obtain stress intensity factors and separate the stress components of isotropic and anisotropic plate problems from the only isochromatics.     

光弹性测量等色线计算机数字图像色谱仿真

应用平面应力-光学定理,计算各点的光程差;应用色彩的RGB原理以及光程差和RGB之间的换算关系,将每个点的光程差换算成RGB值;利用等色线原理,采用VB编写程序,将具有相同RGB值的点按不同的色谱绘出等色线,实现了在载荷作用下光弹性测量等色线计算机数字图像色谱仿真,虚拟再现构件光弹性实验所得到的等色线。对复杂结构,特别是内部存在各种构造孔洞的构件,通过该技术可迅速获得构件全场等色线的分布,为进行结构设计和优化的光弹性实验提供了一种直观的数字化可视技术,同时为高等院校实验力学课程提供了一个虚拟的光弹性实验平台。     

Absolute determination of the isochromatic parameter by load-stepping photoelasticity

A new approach to full-field automated photoelasticity is presented in which a circular polariscope is used to enable the isochromatic phase value () to be determined unambiguously and without input of a known isochromatic value obtained using an auxiliary technique. Values of cos are obtained from light-field and dark-field images for three loads of small incremental steps. Using a relatively straight-forward procedure, ramped phase maps for are produced which can be unwrapped using conventional techniques. The resulting distribution of is then found absolutely using information provided by which is the incremental change in the isochromatic phase value between the load steps. The results obtained for disk-in-compression tests presented here in comparison with theoretical solutions demonstrate that the technique is both simple to use and very accurate. A similar approach may be adopted using three wavelengths instead of three load steps.     

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…     

全息动光弹性旋光法研究

本文提出了一个在全息动光弹性瞬态平面应力问题中同时获得分离的等差线及等和线条纹并分解平面瞬态应力的方法。文中给出了框架在冲击荷载作用下不同时刻等差线及等和线的分离条纹图和某个截面不同时刻的动态应力分布。     

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.     

光弹性—数字散斑相关混合法在光弹条纹主应力分解中的应用

光弹性法是研究结构内部应力分布问题的一个有效方法.光弹性实验中,通常可以方便地得到等色线条纹图.确定了等色线条纹级数以后,为获得平面模型中任意点的应力完全解,需要借助其它方法给出一个补充方程.本文将光弹性法与数字散斑相关法相结合,提出一种用于光弹性法分离主应力的新方法:光弹性-数字散斑相关混合法.在理论研究的基础上,设计了光弹性-数字散斑相关混合法实验系统,并通过相应的三点弯曲实验对该方法和实验系统的有效性做出分析和论证.该研究为光弹全场应力分解以及动态光弹性-数字散斑相关混合法提供了理论和实验基础.     

数字光弹性法综述

将光弹性法与计算机图像处理技术相结合 ,来自动采集光弹性数据和分析应力的方法 ,称为数字光弹性法 ,与传统光弹性法相比 ,它可以进一步提高实验速度和精度。本文详细讨论了以下两个方面 :一是光弹性条纹的细化和倍增处理技术 ;二是自动确定光弹性参数的技术 ,包括相移法、傅立叶变换法、逐步载荷法、广谱分析法和RGB光弹性法等。通过对近二十年来国内外在这些方面的研究、应用和进展作了综述 ,认为采用白光的彩色域相移技术计算光弹性等倾角 ,结合采用白光源或三色光源的相移法来确定光弹性等色线级数 ,有望成为解决静态二维和三维冻结模型薄切片应力分析的最佳方法 ;另外 ,设计一种能实时和同步采集多幅条纹图的实验装置 ,通过相移法来自动获取动态光弹性数据 ,是数字动态光弹性法很有前景的发展方向