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1.
光弹条纹图像的全场相移技术   总被引:2,自引:1,他引:1  
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。  相似文献   

2.
李斌  杨国标 《实验力学》2013,28(2):180-186
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.  相似文献   

3.
钟振威  贺玲凤 《实验力学》2013,28(4):524-528
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。  相似文献   

4.
黄羽  计欣华  秦玉文 《力学季刊》2002,23(1):131-135
由Pindera等提出了等达因法导出了平面问题的三个应力分量,可以非破坏性测取受力物体内部的应力状态,是一种有效的光测技术,应力分量与等达因条纹级次的导数相关,为得到具有高测试精度的应力分量在等达因条纹测试中引入了双折射相移技术,文中提出了一种在散光激光入射光路中用加入一可调偏振片和一可调1/4波片实现散光图象双折射相移的方法,该方法设备简单,能保证总体光强的一致性。  相似文献   

5.
高速动态图像的采集技术   总被引:1,自引:1,他引:0  
佟景伟  张东升 《实验力学》1992,7(2):111-114
本文介绍一种新的高速动态图像的采集技术,它采用红宝石双脉冲激光器作光源,利用普通的图像处理设备,对受冲击载荷作用下的模型,在应力波传播过程中,可采集到光脉冲宽度在30~50毫微秒内的动态图像.本文详细介绍了该采集系统的采图原理以及对模型加载、双脉冲激光器的触发、延时和采图之间的时序和同步关系,并给出了模型受冲击载荷后,延时为30,40,50,60,70,80,90,100μs 时的光弹性等差线条纹图的快速采集实例.  相似文献   

6.
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.  相似文献   

7.
条纹灰度法在光弹性中能自动采集数据、分析和显示等色线条纹图。这种方法组合了光弹性和数字图象分析两种技术,这篇论文描述了一个Apple—Ⅱ微型计算机图象分析系统,它把等色线图分成256×256个图象元素(象素),每一象素将亮度转换成8—bit分辨率的视频讯号,在黑到亮之间产生256级灰度,灰度Z与条纹级数N在暗场时,它能写成N=(1/π)arcsin(AZ~(1/2r))其中A、r是常数。这种方法对相对迟后小于半波长的双折射特别有效,这篇论文中用两片玻璃模型研究弹性应力场,具有很好的分辨率,其结果表明对应力分析主应力差(σ_1-σ_2)有较高精度。  相似文献   

8.
全息干涉法和普通光弹性法相结合产生了全息光弹性法。与此类似,本文建议将散斑干涉法和光弹性相结合形成具有一定特点的散斑光弹干涉法。近十几年来,散斑干涉法得到了很快的发展,可以获得面内或离面位移,错位散斑干涉法则可获得位移梯度场。本文建议将光弹性透明模型置于双光束散斑干涉光路中,通过两次曝光法可以获得模型的应力条纹图案。但和全息光弹性法相比,只要选择合适的漫反射器,用散斑光弹干涉法可以获得不受等差线干扰的、单纯的等和线条纹图。同样的理由,也可以获得三维应力模型冻结切片的等和线条纹图。更有意义的是采用双光片散光穿透模型的散斑光弹性干涉法将有可能获得整体三维应力模型内部的绝对光程应力条纹图,这将为三维应力分析提供一种新的实验方法。  相似文献   

9.
光弹性等差条纹级数的识别   总被引:2,自引:1,他引:1  
本文根据光弹性和光干涉原理,提出了利用双波长测得的扣纹级数小数部分计算条纹全量的方法,并经计算和实验验证其正确性,它的精度取决于小数条纹部分的测量精度.本方法将为光弹性实验数据的自动采集提供了方便.  相似文献   

10.
本文将权矩阵作用于最小二乘法,以此作为从全场条纹图案确定混合型应力强度因子的解法。裂纹尖端附近光弹条纹环对于SIF估算值精确性的影响不是同一水平,如利用一个权矩阵,可以改进光弹性法的实验结果。  相似文献   

11.
A new method that combines phase shifting photoelasticity and transmission Coherent Gradient Sensing (CGS) is developed to determine the tensorial stress field in thin plates of photoelastic materials. A six step phase shifting photoelasticity method determines principal stress directions and the difference of principal stresses. The transmission CGS method utilizes a standard four step phase shifting method to measure the x and y first derivatives of the sum of principal stresses. These stress derivatives are numerically integrated using a weighted preconditioned conjugate gradient (PCG) algorithm, which is also used for the phase unwrapping of the photoelastic and CGS phases. With full-field measurement of the sum and difference of principal stresses, the principal stresses may be separated, followed by the Cartesian and polar coordinate stresses using the principal stress directions. The method is demonstrated for a compressed polycarbonate plate with a side V-shaped notch. The experimental stress fields compare well with theoretical stress fields derived from Williams solution for a thin plate with an angular corner.  相似文献   

12.
《力学快报》2022,12(6):100380
The quantitative characterization of the full-field stress and displacement is significant for analyzing the failure and instability of engineering materials. Various optical measurement techniques such as photoelasticity, moiré and digital image correlation methods have been developed to achieve this goal. However, these methods are difficult to incorporate to determine the stress and displacement fields simultaneously because the tested models must contain particles and grating for displacement measurement; however, these elements will disturb the light passing through the tested models using photoelasticity. In this study, by combining photoelasticity and the sampling moiré method, we developed a method to determine the stress and displacement fields simultaneously in a three-dimensional (3D)-printed photoelastic model with orthogonal grating. Then, the full-field stress was determined by analyzing 10 photoelastic patterns, and the displacement fields were calculated using the sampling moiré method. The results indicate that the developed method can simultaneously determine the stress and displacement fields.  相似文献   

13.
This paper presents a new scattered-light photoelasticity technique which may be called the double-light-beam measurement method. Principal-stress directions and relative retardations related to the principal-stress differences can be measured at any point within an ordinary three-dimensional photoelastic model by this method. This method does not need double loading and the quantities to be measured depend only on the relative light intensity. Moreover, the output signals alternate, providing improved accuracy and stability. If supported by an appropriate program-control and digital processing system, the double-light-beam method can be used to quickly determine the internal stress distribution in ordinary three-dimensional photoelastic models.  相似文献   

14.
This paper describes an automatic measurement method for the stress analysis of a three-dirnensional photoelastic model having the rotation of the principal stress by scattered-light photoelasticity using unpolarized light. The relative phase retardation and the principal stress directions of a linear retarder for a distance in the solid model are expressed in terms of measurable Stokes parameters. The method was used for measurements on a frozen stress sphere under diametral compression.  相似文献   

15.
The method of measurement of a three-dimensional photoelastic model with rotated principal axes has not yet been fully experimentally established. It is known that a three-dimensional photoelastic model can be reduced to an optically equivalent model. In this paper, the optically equivalent model is realized from a stratified model consisting of two layers of the frozen stress model. The secondary principal stress direction and the relative phase retardation of the frozen disk model in the stratified frozen stress model are determined for the entire field from Stokes parameters obtained by scattered-light photoelasticity using unpolarized light. The accuracy of these values is confirmed by a comparison with results only from the frozen stress disk model.  相似文献   

16.
A new instrument capable of the full-field separation of principal stresses on the surface of a component is presented. The instrument combines the techniques of thermoelastic stress analysis and reflection photoelasticity in a single optical head, permitting the simultaneous capture of both data from the same point of view. A single strain witness coating is employed for the acquisition of both the thermoelastic and photoelastic data, which is both birefringent under applied stress conditions and opaque at the infrared wavelengths to which the thermoelastic analysis system is sensitive. This enables the combined technique to be performed continuously from the same surface during loading. The performance of the new instrument is validated in the analysis of a classical laboratory specimen of known geometry. Separated stress data from the experiment is compared to simulated data, demonstrating that the accuracy of the stress separation technique is comparable to that of the individual thermoelastic and photoelastic techniques, and it is concluded that combined thermo-photo-elasticity is a powerful tool for the experimental separation of principal surface stresses.  相似文献   

17.
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.  相似文献   

18.
Design and evaluation of the poleidoscope: A novel digital polariscope   总被引:1,自引:0,他引:1  
The goal of recent research in digital photoelasticity has been fast, reliable, and accurate full-field photoelastic data that will allow the technique to play a valued role in assessing material and structural integrity. A novel design for a polariscope that allows simultaneous capture of multiple images is described, and a prototype instrument is evaluated using both transmission and reflection photoelasticity. The design offers the potential for real-time data acquisition and processing of high-speed events, using a number of different approaches to digital photoelasticity. The evaluation of the instrument arranged for the phase-stepping method demonstrated that it was capable of providing results of comparable quality and accuracy to manual analysis and more conventional methods of acquiring phase-stepped images.  相似文献   

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