改进的六步相移法确定等倾角与等差线相位

光弹性应力分析是一种重要的实验方法,确定等倾线参数和等差线参数是光弹法的关键。常用的六步相移法可以自动确定等倾线和等差线参数,但在求解等倾角时,由于不能避免等倾线相位图中耦合等差线的影响,会造成误差。针对这个问题,本文提出优化方案--多次载荷-六步相移法,实现在等倾线相位图求解中消除等差线的影响。通过处理对称受压圆盘在不同载荷、不同光场下得到的光弹图像,实现光弹性等倾线和等差线的自动判读,验证了所提方法的可行性。     

应力波和动光弹等差条纹的分析与判读

介绍了动光弹的基本原理，并从理论上回答了动光弹应用中的一些问题，如惯性力可否忽略等．并在总结回顾动光弹等差条纹级次判读方法的基础上，提出了把应力波理论与等差条纹分析判读相结合的方法，这样不仅使条纹判读的概念更清晰，而且可提高条纹分析和级次判读的准确性．     

光弹条纹图像的全场相移技术

本文详细分析了光弹性条纹图像的特点，利用图像处理技术，结合相移法及Ｔａｒｄｙ补偿法，实现了等倾线和等差线的全场相移，使得模型中任一点的主应力差值及第一主应力方向值可由计算机自动判读，实现了光弹性实验数据的自动处理。     

光弹等差线与等倾线参数的全场检测法

本文研究了一种自动获得全场等差线级数与等倾线参数角的方法.该方法是根据“相移”思想,利用数字图像处理技术,对光弹等差线图与等倾线图进行位相检测,经过去包裹处理,确定出全场各点的等差条纹级次与主应力方向角.最后通过典型实验,考核了这种方法的正确性与处理精度。     

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。     

图像的色彩分割技术在等差线处理中的应用研究

提出一种基于图像色彩分割的等差线提取新技术,即采用彩色图像卡和摄像机,以白光照射下应力模型在圆偏振光场中等差线条纹的颜色为标志,采用符合人类视觉特征的HSI颜色空间来表示图像的颜色特征,根据“最小色差准则”对等差线进行颜色聚类,实现等差线的快速、准确提取。     

斜拉桥塔锚固区光弹性应力分析与等倾线图像处理

本文采用光弹性冻结应力法，对独塔斜拉桥塔锚固区进行了应力分析，给出了有关截面的边界应力分布及主应力迹线，从而为优化工程设计提供了重要的参考依据。本文还提出了一种新的提取等倾线的方法──图像对数增强相减法，实现了等倾线与等差线条纹的分离，同时使条纹得到了细化，提高了处理等倾线的速度与准确度。编制了自动绘制主应力迹线的程序，利用它绘制了桥塔截面的次主应力迹线。     

非球面全息光弹性仪

引言1967年,Fourney首先提出全息光弹性法,即将全息干涉法与光弹性法相结合。后来,Hovanesion等人拍摄出等差线和等和线的组合条纹。1971年,O'Regan和Dudderar提出用石英旋光器分离两族组合条纹的方法,它能同时获得两族彼此分开的等差线和等和线。1973年,Chatalein又提出用法拉第旋光器分离组合条纹的方法。在全息光弹性法中 ...     

单像素成像的数字光弹研究

数字光弹是光测力学中进行应力分析的重要方法,其核心是通过数字图像处理的方式确定等倾线和等差线参数并获得对应的相位图.传统的数字光弹使用面阵相机拍摄得到光弹性条纹图像,但是通常在特殊波段尤其是在非可见光波段中适用的面阵相机普遍比较昂贵、制造成本也相对较高.本文提出在数字光弹中引入一种具有低成本、高成像质量优势的成像方法—...     

基于动态光弹性方法的冲击载荷作用下自由边界主应力研究

当物体在冲击载荷作用下,物体内部会产生应力波,研究应力波的传播过程及规律对研究物体受冲击载荷作用具有重大的意义.应力波在物体内传播时,在自由边界处产生的主应力状态对于理论求解和计算有着重要意义.采用动态光弹性方法,结合新型动光弹系统及相关实验设备采集物体在冲击载荷作用下的等倾线和等差线条纹图,通过分析等倾线的条纹,得出等倾线与自由边界相交所成角度不为0°或909,得出在物体自由边界处两个主应力均存在且不为零的结论.针对上述结果,采用电测方法进行验证,两试验结果相符合,方案可行且准确.     

Application of holography to photoelasticity

This paper discusses the exploratory application of holography to photoelasticity. It is shown that the two-beam holographic method may be used to record the birefringent pattern of a standard two-dimensional photoelastic specimen. A special type of polariscope is required. A discussion is presented of the various arrangements required to produce isochromatic, isoclinic, isopachic and combined isopachic and isochromatic fringe patterns. The three-dimensional nature of the holograph is utilized to separate the principal stresses by means of oblique incidence. Both normal- and oblique-incidence fringe patterns are recorded on a single hologram. A brief discussion of the extension to the dynamic case is presented.     

A new method of resolving transient stresses in dynamic holophotoelasticity

A method which allows the simultaneous separation of the isochromatic and isopachic fringes for transient plane-stress problems is presented. A double pulsed ruby laser and a terbium glass Faraday rotator is employed to resolve the transient isochromatic and isopachic patterns. Separated fringe patterns for a structural component are recorded at nine different instants after impact loading. The dynamic material-fringe values of isochromatics and isopachics are obtained within the experiment. Finally, dynamic stresses distributed along a section at different time intervals are resolved.     

混合光载波法分离动静态主应力

本文将等差载波位相调制原理与夹层全息术结合形成的混合光载波法,可同时获得等差载波条纹图与混合载波条纹图.对混合载波纹图进行光学付里叶变换,利用空间滤波技术可将等和载波条纹从中分离出来.利用图象处理技术实现了对两种载波条纹图从预处理到应力计算的自动化处理.将混合光载波法应用于动态全息光弹性,分离了动态主应力. 文中还提出了一个经济实用的大尺寸载波片制作技术.     

Computer-simulated stress-optic patterns

A new method for producing theoretical fringe patterns using a small real-time computer interfaced to analog equipment is presented. The method applies equally well to isochromatic, isopachic or interferometric stress patterns of any stress field for which the analytical solution is known.     

A neoteric interferometer for use in holographic photoelasticity

A shortcoming of the conventional holographic interferometer used in photoelasticity is that, for the double-exposure cases, the resulting fringe patterns are a complex combination of conventional isochromatic and isopachic fringes. This paper describes a holographic interferometer that may be used to obtain separate but simultaneous isochromatic- and isopachic-fringe patterns for photoelastic models in states of plane stress. The method requires a model with a partially reflecting front surface. Isopachics, which are proportional to the thickness change, are recorded using holographic interferometry from the transmitted light. The isochromatics are obtained from the transmitted light by conventional means. General equations relating the surface displacement of the specimen to the observed fringe patterns are developed, and examples of static and dynamic loadings are shown.     

A simple method for the digital determination of the photoelastic fringe order

A new and simple approach to the digital determination of a photoelastic fringe order using two different loads is proposed. The relationships between the intensity values of light and the isochromatic fringe orders generated from two different loads are derived. The scheme used for the automated determination of the total fringe orders of a full-field photoelastic fringe pattern is described. The usefulness of this method is demonstrated using two isochromatic fringe patterns under two different loads. Extra filters are not needed in the proposed method as in the case of the two-wavelength method.     

Interpretation of fringes in stress-holo-interferometry

Previous studies had concluded that stressholo-interferometry patterns consist of the independent superposition of the isopachic family (with half-order fringe shifts) and the isochromatic family. It is shown here that this interpretation is not always valid and can result in serious errors in some cases. In particular, it is demonstrated that the position, and even the existence of the fringes, are affected by the interaction of the isopachics and isochromatics. This effect is most pronounced when the two families of fringes are nearly parallel and of approximately the same spatial frequency. The independent superposition interpretation is most accurate when the two families of fringes are orthogonal, whatever the ratio of spatial frequencies might be. These properties are illustrated using computer-generated holographic interference patterns.     

复合型裂纹应力场的研究及其应力强度因子的全息光弹性测定

本文应用复变函数解法,等出复合型中心裂纹板弹性应力场的精确解及主应力和与主应力差的精确表达式。通过与各自的奇异表达式比较,得到了主应力和与主应力差的远近场关系图谱。利用这些图谱以及全息光弹性试验所获得的远场等和线与等差线条纹,就能确定裂纹尖端的应力强度因子 K_Ⅰ,K_Ⅱ。实例表明:本法概念清晰、演算简便、精度较高。     

反射全息干涉和反射光弹性方法应用于应力波传播

在应力波传播过程中,半无限平面的聚酯模型在一个截面上的主应力分布解被实验所确定。应力波由摆式重锤的冲击所产生。应用两个外部适当的触发装置触发一个双脉冲红宝石激光器(0.5焦耳/每脉冲)。模型的一个表面做成全反射面,利用对这个表面的反射式全息干涉法和通过模型的另一表面的反射式光弹性法可以记录冲击后不同时间延迟的等和线与等差线条纹图。