一种散光图象双折射相移的方法

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。     

液体双折射方法及其在流场测量中的应用

本文研究了流体双折射的实验方法及双折射液体的基本性质。计论了两种力学—光学关系式之间的一致性。从理论及实验上证实了用流体双折射方法进行二维流场测量的优越性。提出了实验数据的处理方法。给出了几种流场的等色线图。定量分析了两个流场。     

等达因图象的自动采集与识别

文中提出了一种机机械扫描系统．小功率激光器、图象板、相移元件、微机和程序软件组成的等达因图象自动采集与处理系统，用灰度值比较的思想实现了等达因图象的跟踪采集。提出了四幅图象相移法实现等达因图象的自动识别。系统能快速、实时、精确和全自动地实现等达因图象的记录和分析。给出与物体内各点应力状态一一对应的位相图。并用来研究了其他实验方法困难的局部三维效应问题。     

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。     

用焦散线—内插法确定光学各向异性材料的应力强度因子

本文采用内插法,将光学各向异性材料——双折射材料的焦散线问题转化成为“光学各向同性”材料的问题,进而用改进的 J.F.Kalthoff 方法来确定双折射材料应力强度因子 K_Ⅰ和 K_Ⅱ.文中以聚碳酸脂、环氧树脂为例进行了具体讨论,将得到的结果及文[7]中的结果一起与相应的理论计算值进行了比较.     

DCM 相位梯度提取技术在光力学图像信息识别中的应用

为解决相位去包裹对光力学图像处理的影响问题,本文将一种直接从数字编码傅立叶变换或相移条纹图中逐相素提取相位梯度的方法应用于光力学图像信息识别中。该方法是一个广泛应用于光纤传感器中的微分正交乘法器(DCM)的正、余弦相位检波技术。这一技术算法简单,不需计算反正切,不受相位去包裹方法标准的限制,非常适于应用在以相位梯度作为最终所需识别的信息的光力学图像处理中。本文以载波等达因条纹图应力场计算及四幅图相移等达因法求板的接触应力为例,对该技术在光力学图像信息识别中的应用进行了论证。     

超声纯横波法测试45#钢的内部应力

声各向同性的金属材料在应力作用下,材料表现出声各向异性,这是用声弹性法分析材料内部应力的基础。本文用垂直于应力方向传播的超声纯横波对45#钢进行测试,测试时横波的偏振化方向分别平行和垂直于应力方向。实验结果表明:材料在拉、压应力作用下,相互正交的两超声纯横波的声速都发生了变化,且声各向异性因子与应力成线性关系。利用此关系可测试材料内部应力,提供了一种无损测试材料内部应力的方法,另外本实验方法也可以对材料内部残余应力进行评估。实验中利用回振法测量声速,可测量声速的微小变化,精度高。     

焦散线法对双折射材料断裂性能的研究

提出了双折射材料Ⅰ-Ⅱ混合型裂纹问题焦散线的形成原理,讨论了μ(=K_I/K_I)及光学各向异性系数ξ对焦散线形状及其几个特征量的影响,得到了双折射材料应力强度因子K_Ⅰ、K_Ⅱ的求法.以聚碳酸脂、环氧树脂为例,确定了它们在不同裂纹及不同载荷条件下的应力强度因子K_Ⅰ、K_Ⅱ.     

双折射主切片法研究热历史对有机玻璃残余应力分布的影响

本文应用双折射主切片法研究了热历史对有机玻璃残余应力分布的影响。研究表明:淬火有机玻璃残余应力的分布规律与玻璃型号、冷却方式无无关;残余应力的数值取决于淬火冷却速率。退火能大幅度降低淬火有机玻璃内的残余应力,消除程度取决于退火温度和保温时间。在测定淬火有机玻璃残余应力方面,本文所推荐的双折射主切片法不仅远优于现有的只能定性和半定量的表面应力测量方法,而且优于能定量的剥层法和双折射次切片法。     

频域滤波及相移技术在ESPI中的应用

本文针对电子散斑条纹颗粒性强这一特点,采用频域同态滤波技术,对ESPI 条纹进行了滤波处理,实验表明,该方法对改善 ESPI 条纹质量非常有效.另外,本文还推出了一种自行设计的新型相移器,它结构简单,操作简便,并且稳定性好,可适用于各种光力学干涉光路.文章最后使用双光束电子散斑法,应用以上技术,对一个带方孔板的平面应力模型的面内位移进行了定量分析.     

3D stress local nondestructive analysis in the middle plane of a plate

The Isodyne technique based on the scattered light scanning from a thin laser beam can be used to obtain the information inside the loaded object in the room temperature nondestructively, so it is a very powerful technique in 3D stress analysis. The problems are how to interpret the information and how to get sufficient information from the few interference fringe. Birefringence phase shift technique can distinguish the fringe orders automatically and enrich the information in 256 gray levels between maxim and minim light intensity. In the paper the Isodyne birefringence phase shift method with an oblique incidence and equilibrium equation is presented, by which the 3D stresses in the middle plane of a plate with U shape notch are separated successfully. The project supported by the National Natural Science Foundation of China under the Grant No. 1380345     

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。     

Photoviscoelasticity on a microsecond time scale

A previous paper¹² has described the optical calibration of photoviscoelastic materials on a microsecond time scale. In this paper, attention is given to the experimental determination of the two-dimensional plane-stress field in a body subjected to arbitrary loads. Symmetry of load and geometry is not assumed. Since the stress state depends on the history of fringe order and isoclinic angle, these basic data must be recorded. Due to nonlinearity in the material studied, the photoviscoelastic data were limited to fractional fringe orders. This introduced problems of initial birefringence and polariscope imperfections. Techniques are described which correct for these imperfections and allow for acquiring and analyzing the basic photoviscoelastic data.     

Photoviscoelastic stress analysis of a plate with a central hole

An epoxy resin containing excessive plasticizer was developed and characterized. The material, which deforms viscously at room temperature, has optical properties that depend on stress and strain. A tensile specimen was prepared from the epoxy resin so that the mechanical and optical properties of the epoxy resin could be characterized. The elastic and plastic behavior was determined at 37°C using tensile stresses between 4 and 26 MPa. The birefringence was also recorded as a function of time and stress. From these results, a photoviscoelastic constitutive equation was constructed to describe the dependence of the birefringence on stress and strain. The constitutive equation was then applied to study the deformation of a tensile specimen containing a central circular hole. By using the isochromatic fringes in combination with the isoclinic, the time-dependent variation of the stress field in the specimen was solved.     

频率向导的单幅散斑条纹图位相提取方法

提出一种基于条纹频率向导的单幅散斑条纹图位相提取技术,可对一般的散斑条纹图进行自动化位相提取. 该方法利用加窗傅里叶运算求得散斑条纹图的条纹频率,并在条纹频率的向导下对散斑条纹图的位相进行提取. 数值模拟和实验结果证实了这一方法的有效性.      

Incremental forming: an integrated robotized cell for production and quality control

The present work proposes the integration of a incremental forming robotised system with an optical measurement device (robotised too) formerly developed for quality control purposes of processes and products. A parallel kinematics robot moves a spherical punch according to a predefined path, deforming a gridded sheet metal that is scanned by a couple of cameras moved by a second robot. As a result of the post-processing of the acquired images, accordingly to the so called grid method, the strain distribution can be computed, and the quality of the forming process can be assessed. The system is completed by a projector and four fixed cameras, that permit to evaluate the final shape of the formed part by means of the fringe projection and phase shift techniques.