发光光弹性涂层荧光信号强度的影响因素

为提高发光光弹性涂层方法中涂层的荧光信号强度,以液态E-44型环氧树脂为光弹性材料、罗丹明B为荧光染料,制作了新、旧两种不同结构的发光光弹性涂层.通过对新、旧两种结构发光光弹性涂层受465nm光波激发时荧光发射光谱的比较,说明新的发光光弹性涂层结构比原有发光光弹性涂层在提高测量信号强度方面的优势,测量结果还表明:发光光弹性涂层测量信号的强度提高还与合理选择涂层中荧光染料浓度、荧光信号发射波长有直接关系.     

基于染料的光弹性涂层方法回顾与展望

光弹性涂层法是最常用的实验应变分析测试技术之一,但其实际应用受到诸如准备时间长、基底加强效应、复杂的数据后期处理等固有局限性的影响。近年来,出现了两种通过在光弹性聚合物材料中添加非发光染料或发光染料的新的光弹性涂层制作方法。这种基于染料的光弹性涂层使新方法能够克服上述传统光弹性涂层法应用中的许多局限性,并有望成为重要的应变测量工具。论文回顾了这两种新的基于染料的光弹性涂层方法的提出与发展过程,分别介绍了两种测量方法的实验装置、基本原理及一些实际应用,总结了两种新方法各自的优点与不足。最后指出了基于添加发光染料的发光光弹性涂层的未来发展方向和技术改进。     

复合材料光弹性分析的工程方法

本文在推导均衡光弹性复合材料应力(应变)—光定律的基础上,导出了均衡光弹性复合材料的近似应变—光定律。然后加以推广,提出适用于一般光弹性复合材料的近似应变—光定律.精度分析及实验验证表明:作为工程计算,在采用本文推荐的参数时,光弹性复合材料可视作各向同性材料进行光弹性分析。     

复合材料光弹性分析的近似方法

本文提出了一种用于光弹性复合材料的简化应变——光学定律。按照这一简化定律。模型材料的主应变差和主应变方向只要利用光弹性实验测出的等差线与等倾线即可求得。些是一种正交异性光弹性分析的近似方法,这一方法所得结果与实验数据比较,最大误差在10％左右。由于采用简化应变——光学定律使得正交异性光弹性分析工作大为简便,因此它是一种适合于工程应用的近似方法。     

一种动光弹模型材料的制作方法及其应用

基于#618环氧树脂、甲基六氢苯酐、促进剂DMP-30、环氧树脂消泡剂四种原料,提出制作光弹性模型的新配方和新方法,并利用单轴压缩实验、电测法和动态光弹法分别测定了制作的光弹模型的动态力学参数。新方法工艺简单,制作周期短,对人体无害。制作的光弹模型初始应力小,表面光洁,质地均匀,透光性好,光学灵敏度高,具有良好的机械加工和切削性能。通过三点弯曲梁冲击实验,得到了清晰的光弹等差条纹图像,验证了该配方和方法制作的模型可以应用于动态光弹性实验。     

Computer aided photoelasticity by an optimum phase stepping method

In this paper an automated photoelastic method based on the phase stepping technique is described. It provides full-field maps of the isoclinic parameter and the relative retardation. The technique is based on processing six images of a photoelastic specimen acquired using plane and circularly polarized light. The number of acquisitions and the type of polariscope used in this approach have been chosen with the aim at reducing the influence of quarter wave plate errors and obtaining raw photoelastic data in a periodic form suitable for easy applications of automatic unwrapping routines.     

Suitability of the photoelastic implementation of polymers with material birefringence

Scattered photoelastic techniques would gain considerable momentum through better understanding of the nature and response of the available photoelastic materials. The influence of the prevailing birefringent effect in the state of load-free polymers on the radiated scattered light energy is investigated. Six different photoelastic materials are considered. The impact of material birefringences on the quality of reading the fringe orders of the scattered radiation in a stressed photoelastic medium is explored. Spectral dependence of the modulation of light vectors in acrylic materials (Plexiglas) is illustrated. The advantage of this characteristic as a convenient means of compensation in scattered photoelasticity is pointed out. Acrylic sheets, a relatively cheap transparent polymer, seem to be suitable for scattered photoelastic analysis. The moiré technique might find application in determining fringe orders in a material such as Homalite-100. Replacing the primary beam by a primary sheet saves the cost and effort consumed in the scanning process. Paper was presented at the 1988 SEM Spring Conference on Experimental Mechanics held in Portland, OR on June 5–10.     

基于分子发光原理的光弹性涂层测量方法

在简单介绍分子荧光产生过程的基础上,系统介绍了新的光弹性涂层方法------发光光弹性涂层法的基本原理、涂层结构、系统组成及实验方法.由于新方法采用了气雾剂技术, 并通过在光弹性涂层中添加荧光染料,使新方法与传统的光弹性涂层方法相比, 具有如下优点: (1)更简单、快捷,特别是对于有复杂几何形状的构件; (2)只会引起较小的基底加强效应;(3)能提供更高的空间分辨率; (4)省去了条纹计数和位相去包裹的过程,简化了后续的数据处理过程; (5)发光涂层的发射光是漫射光,使得对曲面进行测量时有较高的相对强度.最后指出了新方法今后的研究方向及其在诸如产品设计流程中与有限元分析相结合等方面的广阔应用前景.      

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     

电子散斑和全息光弹法相结合测量透明材料的应力强度因子K1

全息光弹性中等和线是获得断裂力学中应力强度因子的一种有效方法之一。但用传统的全息光弹性方法获取等和线需暗房，要经过显影定影及再现，而且不能直接数字化使其应用受到限制。本文提出一种将全息光弹性与相移电子散斑干涉（Electric Speckle Pattern Interferometry，简称ESPI）有机结合的方法，不但克服传统全息光弹性的不足，而且使全息光弹性实现了数字化。文中将这一方法成功应用于有预制裂纹的三点弯曲试件上，定量求得其应力强度因子（Stress Intensity Factor，简称SIF）K1，而且实验值和理论值具有相一致的结果。     

On the role of material and optical properties in complete photoelastic analysis

Consideration of the laws of elasticity and optics allows the classification of photoelastic materials into several categories. Two types of photoelastic materials are studied experimentally in compressible and incompressible forms to decide in which category they belong. Two epoxies and three polyurethane rubbers are reported. Both epoxies were calibrated for their response to frozen stress, and one under live load. The rubbers were all calibrated under live load at ambient temperature. The results support an earlier hypothesis that the photoelastic response of incompressible materials is strain sensitive and cannot be used directly in the general three-dimensional case to determine normal stress without additional data.     

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.     

Dynamic crack curving and branching under biaxial loading

A 16-spark-gap camera was used to record the dynamic photoelastic patterns of ten centrally cracked, Homalite-100 specimens which fractured under ten initial biaxial-stress ratios ranging from 3.7 to 0, some of which do not exist in normal fracture specimens. The dynamic photoelastic patterns of curved cracks were used to verify the previously developed dynamic-crack-curving criterion. Cracks which immediately curved upon propagation in three specimens under abnormally high inital biaxial loading were used to verify the static counterpart of the dynamic-crack-curving criterion under these extreme loading conditions. A previously developed dynamic-crack-branching criterion was also verified by four dynamic photoelastic results involving cracks which eventually branched under the lower initial biaxial loading.     

彩色光弹性干涉影像分析系统

自行开发的“彩色光弹性干涉影像分析系统”首先利用CCD成像和图像采集设备,将光弹图像以数字图像的形式存储到计算机,然后通过对存储的光弹图像进行处理,得到物体边界、等差线、等倾线等数据。最后根据这些数据,绘制出主应力迹线,并进行二维的和三维的应力分析。本文着重介绍了系统整体设计以及系统研制的难点问题(彩色光弹图像处理、主应力迹线的绘制等)。系统可以通过对彩色图像进行分解,应用目前已经比较成熟的灰度光弹图像处理技术,来完成彩色图像的处理;也可以直接应用彩色信息来确定条纹级数,进行相关处理。彩色图像能够比灰度图像提供更精确的图像信息,以满足高精度测量的要求。     

Photoelastic analysis of the singular stress field in a bimaterial wedge

This paper presents an experimental investigation of the singular stress field near the vertex of a bimaterial wedge using a digital photoelastic technique. Special attention is given to the casting of bimaterial wedge specimens and analysis technique for extracting stress intensity factors from photoelastic samples. Different bimaterial wedge specimens are made of two different photoelastic materials bonded through a special casting procedure and loaded in simple tension. A new multiple-parameter method is developed to obtain the stress intensity factor reliably from the isochromatic fringe patterns and the series representation of the stress field at the vertex of the wedge. Experimental results are compared with finite element predictions, and good agreement is observed.     

Construction of complex photoelastic models using thin molded-epoxy sheets

The construction and analysis of complex thin-shell photoelastic models are discussed. Examples of both two- and three-dimensional applications are presented. The first example concerns an investigation of the structural supports of a new and unique blastfurnace design. The second example is directly related to the design and analysis of complex thin-shell pressure vessels and manifolds. Existing laboratory techniques were used successfully to construct the photoelastic models. The construction method is basically an extension of the techniques previously associated with the contour-sheet method of preparing photoelastic coatings. As such, it does not involve new or untried concepts, but rather it extends the existing in-house capabilities of many laboratories.     

挤压凹模强度的光弹性与有限元优化综合分析

本文介绍用光弹性试验测定挤压凹模工作时承受的内压力分布规律,在此基础上作了凹模的有限元优化设计,最后进行了光弹性实验验证.这种综合分析方法为提高模具的承载能力、节省模具材料和改进模具结构设计提供了有益的经验.     

Stress field tomography based on 3D photoelasticity

A tomographic method for identification of stress fields based on 3D photoelasticity has been developed. A second order tensor field tomographic method based on the general inverse problem of 3D photoelasticity, previously developed by the authors, is found to be highly sensitive to errors in photoelastic observations. In this study a new tomographic method for stress field with fairly high robustness to errors in photoelastic observations has been developed by introducing both equilibrium condition and linear elasticity to the previously developed general tensor field tomographic method. This new stress field tomographic method expands unknown 3D stress distributions as a linear combination of independent set of basis functions and a new inverse problem is posed: identify the amplitudes of basis functions based on photoelastic observations. Just as the inverse problem of 3D photoelasticity, this newly posed inverse problem is also nonlinear and ill posed. Unlike conventional approaches to 3D photoelasticity, both these nonlinearity and ill-posedness are properly treated using a load incremental approach. Load incremental approach chops the nonlinear solution space into segments with unique solutions by conducting photoelastic observations at sufficiently small increments in external load. Validating both numerically and experimentally, it is shown that this new stress field tomographic method has sufficient robustness against errors in photoelastic observations and is applicable to experimental stress measurements.     

Experimental stress analysis in the design of a liquid-hydrogen pump rotor

A design optimization of the cross section of a high-speed rotor to pump liquid hydrogen was accomplished by means of photoelastic evaluations and model tests. The photoelastic models were rotated in the field of a polariscope with stroboscopic light synchronized to this rotation to evaluate the stresses. Differential radial growths were measured from model tests.     

Photoelastic modeling of the fracture of viscoelastic orthotropic plates with a crack

The well-known equations of photoelasticity of linear viscoelastic bodies are used to describe the photoelastic behavior of a viscoelastic orthotropic plate with a crack. Expressions for the stress intensity factors (SIFs) at the crack tip are obtained using photoelastic measurements. The time dependence of the SIFs is analyzed and shown to be determined by the angles between directions of the crack and tension