三机部召开光弹性学术会议

三机部于去年召开了光弹性试验学术讨论会。出席会议的有各工业部门、中国科学院、高等学校共63个单位。会议交流资料58篇。报告内容涉及普通光弹性、光弹性涂层法、热光弹性、激光全息光弹性、光弹性在断裂力学方面的应用、     

三机部召开光弹性学术会议

三机部于去年召开了光弹性试验学术讨论会。出席会议的有各工业部门、中国科学院、高等学校共63个单位。会议交流资料58篇。报告内容涉及普通光弹性、光弹性涂层法、热光弹性、激光全息光弹性、光弹性在断裂力学方面的应用、     

国内外近期学术会议消息

国内部分1.光弹性试验技术交流会主办单位:第三机械工业部。地址:无锡. 会期:1978年5月20-28日. 内容:对普通光弹性法、光弹性涂层法、热光弹性法、激光全息光弹性法、光弹性在断裂力学中的应用,以及光弹仪器、光弹模型材料等方面问题进行了交流和讨论。     

《实验应力分析》 赵清澄、石源主编,科学出版社出版,1987.

本书内容包括电测和光测两大部分。光测部分除常规的光测技术之外,还涉及动光弹、热光弹、光塑性及焦散线法等,并把光测法在断裂力学中和生物力学中的应用作为两个专题     

光测力学的光载波研讨会在扬州举行

根据国家教委高校师资培训计划,南京工学院力学研究室和江苏农学院水利及农业工程系于1986年11月23日～30日在扬州市联合举办了光测力学的光载波研讨班。来自全国的四十余名同志参加了研讨。南工徐铸教授和上海城建学院王汝鹏高级工程师担任主讲教师。他们向大家介绍了国内外光测力学的光载波研究概况;系统讲解了光载波方法的基本原理以及光载波在光测力学上的具体应用。研讨班在载波光弹性、载波散斑法、载波全息干涉法及图象处理等方面安排了实验。     

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     

全国光弹性材料学术会议

全国光弹性材料学术讨论会于1980年9月在青岛召开.会议围绕三个中心问题进行了交流:(1)光弹性材料能测试的方法;(2)光弹性材料的质量问题;(3)型型制造技术及工艺等.此外还交流了贴片材料的制造工艺以及三向激光全息材料、热光弹材料、光塑     

全国光弹性材料学术会议

全国光弹性材料学术讨论会于1980年9月在青岛召开.会议围绕三个中心问题进行了交流:(1)光弹性材料能测试的方法;(2)光弹性材料的质量问题;(3)型型制造技术及工艺等.此外还交流了贴片材料的制造工艺以及三向激光全息材料、热光弹材料、光塑...     

对阎石、易军同志《对<用偏振全息术分离绝对程差条纹>一文的浅析》一文的答复

1.关于偏振全息术与一般全息术的区别 1)一束参专光的全息术只能记录物光的振幅和位相,不能记录它的偏振状态,故无法使物光的偏振状太再现出来.而用两束正交偏振参考光的偏振全息术,不仅可以记录物光的振幅和位相,还能把物光的偏振状态记录下来并能使之再现,从信息量的多寡来说,偏振全息术是能够把物光全部信息(振幅、位相和偏振状态)都记录下来并能使之再     

对光测力学教学工作的实验和体会

光测力学这门课对我来说,既是老课,又是新课。早在1968年我校力学专业成立后,光测力学课就随之开始了。从当时到现在,课程内客、教学对象和要求都发生了变化,具体说来就是:从古典的光测弹性力学到现代光测力学,从力学本科生的光测力学     

基于神经网络和遗传算法的光塑性图像处理

本文论述了神经网络、遗传算法结合起来在光塑性图像处理中的应用 ,以楔横轧工序的光塑性图像处理为例 ,三次投射时光塑性图像中各点都有对应的等差线条纹级数和等倾线角度 ,首先利用神经网络建立起图像参数与等效应变之间关系的数学模型 ,然后用遗传算法对图像参数进行优化 ,优化结果与实际情况吻合良好。由此证明神经网络、遗传算法完全可以较好地优化光塑性图像参数 ,并应用于光塑性图像处理领域     

结构分析的光塑性法

本文围绕光塑性的模型理论、模型材料和应力—光学规律等基本问题的研究工作进行论述,提出一个可供实际应用的结构分析的光塑性方法,并在实际中作了初步应用。     

Loaded and unloaded optical response of polyester model materials

The optical behavior of mixtures of rigid and flexible polyester resins when loaded and unloaded under constant strain-rate and varying test temperature are characterized. New evidence about the photoplastic method of analyzing deformed but unloaded models is presented through experiments with tensile or compressive uniaxial specimens, diametrically compressed disks and beams under pure bending, which were analyzed during loading, unloading and after being unloaded.     

Photovisco-elastoplastic behavior of polycarbonate material under creep and tension tests

Polymers are widely used as photomechanical models of a prototype material (often a metal). Photoplasticity is one of the methods used in order to show the behavior of plastic materials stressed beyond the linear elastic limit. To illustrate this process we have analyzed the photovisco-elastoplastic behavior of polycarbonate as a photoplastic material. In this paper a technique for local and simultaneous measurement of birefringence and principal strains is presented. The mechanical and optical properties, at room temperature, have been evaluated by means of uniaxial tension tests. A series of creep tests has been carried out in order to study the photovisco-elastoplastic behavior of polycarbonate. In two different experiments we analyzed nonlinear birefringence and the amplitude of the corresponding strains. We could thus evaluate the distribution of strains and the distribution of uniaxial stress for each birefringence state and vice versa.     

摆辗成形后的摩托车启动齿轮三维塑性应变场的光塑性分析

本文叙述了采用聚碳酸脂材料模拟低碳钢和低碳合金钢一类金属的摩托车启动齿轮(下面陶称为端面齿轮)摆辗成形过程。运用光塑性法计算分析了氐形后的光塑性模型内部三维塑性应雯分布;对采用螺旋形轨迹和玫瑰线轨迹成形后的光塑性模型内部的三维塑性应变分布进行了分析比较。该方法已为摆辗最佳工艺参数的选择提供了有用的依据。     

花键轴冷挤压成形后的三维光塑性模拟研究

本文利用光塑性方法,以聚碳酸酯（Ｐｏｌｙｃａｒｂｏｎａｔｅ）为材料研究了矩形花键轴冷挤压成形过程,获得了花键挤压成形的三维塑性应变场分布,提出其变形的应变分布特征,并对典型截面的应变进行了计算分析;文中还通过对聚碳酸酯材料的实验,得到了使花键齿形充满的最佳坯料尺寸,为实际工艺生产优选出合理的工艺参数。     

Photoplastic stress analysis considering rate effect

The possibilities of cellulose acetate as a photoplastic model material used in the uniaxial tension test were presented by the authors in Ref. 1. Empirical formulas were proposed for photoplastic stress analysis considering the effect of strain rate and temperature. In this paper, the stress-strain-optic laws derived from the uniaxial tension test were confirmed precisely under the biaxial stress field. Consequently, the biaxial stress-strain-optic laws of cellulose acetate can be represented by simply substituting the difference of the principal stress and the difference of the principal strain into the terms of the stress and the strain in the empirical formulas for the uniaxial stress state, respectively. Therefore, the empirical formulas considering the influence of strain rate were obtained for the photo-viscoelastoplastic plane-stress analysis during the usual static loading. This method was applied to an elastoplastic problem of a finite plate with a circular hole under uniaxial tension. The distribution of stress and strain, the stress-concentration factors in the elastoplastic region and the development of the plastic region were obtained experimentally taking the rate effect into account. As a result, the stress on a minimum section in a model increased as head speed increased. On the other hand, the distribution of strain, the development of the plastic region and the stress-concentration factors were almost never influenced by head speed.     

The ductile fracture of polycarbonate

The fracture of a known ductile polymer (polycarbonate) is investigated. It is shown that polycarbonate obeys the Dugdale model of ductile yielding by comparing measured plastic-zone sizes and displacements to the theoretical predictions. Strain-energy release rates are calculated and the critical value is shown to be one or two orders of magnitude higher than critical values for brittle polymers. Photoelastic photographs of the fracture process are presented and it is shown that the photoelastic effect definitely enhances the definition of the yield zone. Microscopic photoelastic photographs are also presented which are used to give a new interpretation to the photoplastic effect. Finally, suggestions for future work are presented.     

Yield behavior of photoplastic materials

A mixture of flexible and rigid polyester resins has been used previously by Morris and Riley¹⁶ and by Zachary and Riley⁹ to model plastic deformations. The last of these papers furnished mechanical and optical properties under uniaxial tension and compression for several different mixture ratios of the polyester resins and also presents some results under multiaxial-stress conditions from thin cylinders under internal pressure. In a recent paper, Burger, Gomide and Scott¹⁴ used the rigid polyester resin at elevated temperature to model plastic deformations in upset rings; the behavior of the rigid polyester was verified with diametrically compressed disks and uniaxial-compression specimens. A very important similitude requirement for model to prototype scaling in photoplasticity work is that the macroscopic yield behavior of model and prototype materials must be the same. Thus, not only uniaxial tension and compression properties must be examined, but also yield properties under multiaxial-stress states have to be determined. The purpose of this paper is to provide additional information on the yield behavior of polyester mixtures which appear suitable for model studies of manufacturing methods such as rolling and extruding. For these processes, mixture ratio, test temperature and strain rate can be used to control the shape of the stress-strain curve and the yield behavior. The experimental procedure used to determine the initial yield locus of the photoplastic materials employed a new specimen geometry proposed by Arcan, Hashin and Voloshin¹⁸ which produces uniform biaxial-stress fields of opposite sign in one section of the specimen. Both polycarbonate and polyester materials were evaluated using this procedure and results are compared with those available in the technical literature.     

Three-dimensional strain distributions in upset rings by photoplastic simulation

The changes in internal diameter that occur when a hollow disk, or ring, is plastically deformed by axial compression have been proposed as a method for measuring interface friction during metal forming. The adoption of this test method has been delayed because the three-dimensional strains in such rings are not known. This paper describes how an experimental method using photoplastic simulation was used to obtain the three-dimensional strains for a particular ring geometry. It presents proot of highly nonuniform strains and also shows that the division between flow inward and flow outward occurs at different radii through the thickness of the ring.