动态光测弹性力学研究(二)

四、动光弹中几个根本问题在动光弹中有三个根本问题: (1)动态应力—光学定律;(2)动态条纹值的确定;(3)动态条纹级次的确定。 1.光学—应力定律动光弹中的应力—光学定律与静态是否相同,Frocht等人在1953—57年间作了大量的试验研究,证明在线弹性状态下动应力—光定律与静态是一致的,这就给动光弹建立了最根本的定律。但Frooht未提变形速度限制。如变形速度超出某极限值,或材料处于弹塑性状态,则上式不成立了。     

弹光和电光级联的组合相位调制型椭偏测量术

利用弹光调制器的偏振调制优势,提出了将弹光调制器和电光调制器级联的组合相位调制型椭偏测量术。该技术采用单光路实现信号探测,通过切换电光调制器的两个工作状态,并结合数字锁相信号处理技术来完成样品反射光的p分量和s分量的幅值比Ψ和相位差Δ的全范围高精度测量。对提出的新型椭偏测量原理进行了分析,搭建了相应的实验系统。完成了弹光调制器的调制电压峰峰值和相位调制幅值关系的定标,定标结果优于99.05%,然后还采用系统初始偏移值的方法对实验系统进行了校准。最后,运用该系统对石英玻璃反射样品进行了实验分析,得到的Ψ和Δ的测量精度分别优于0.08°和0.81°。实验结果显示系统校准有效地消除了电光调制器和弹光调制器的剩余双折射引入的测量误差;数据采集和处理时间均在ms量级。提出的测量技术具有宽光谱测量、工作稳定、重复度高、测量速率快、成本相对较低和系统便于工业自动化集成的潜在优势。     

弹支瓦阶梯推力轴承动特性研究

本文研究了作者提出的弹支瓦阶梯推力轴承的动特性及系统阻尼特性。本文及［１］的研究表明这种新型轴承不仅具有良好的承载特性，并且具有良好的动特性及系统阻尼特性．     

JGT-1型激光散光光弹仪的设计

激光散光光弹仪是一种新型的实验应力分析仪器,本文着重介绍了该仪器在设计中考虑的一些光学和机械系统方面的问题,另外对散光光弹性法的基本原理也作了简单介绍。     

双头弹速度测量系统研究

提出了一种基于数据采集卡配合光幕传感器的双头弹速度测试系统,详细地阐述了测量系统的组成与测量原理;采用相关算法分析双头弹穿过光幕靶传感器的输出信号,提高了弹丸时间间隔值求取精度。经实弹射击测试验证,该测量系统具有测量精度高、抗干扰能力强和操作简便等特点。     

火箭布雷训练弹的设计与应用研究

分析了火箭布雷训练弹研制与应用中存在的问题,提出了面向实战应用的火箭布雷训练弹功能需求。设计了新型训练弹系统软硬件结构框架,探讨了新型火箭布雷训练弹的工作机理,开发出了可以与实装进行数据通信、随时可以开展训练、通过三维效果展现布雷效果的新型训练系统,该研究成果解决了部队在训练学习过程中难以开展实弹训练的困难,具有较高的推广应用价值。     

基于光纤干涉系统非接触冲击波速度测试

根据轻气炮冲击波速度测试实验的特点与需求,提出一种新型可适用于强冲击实验的全光纤非接触速度测量技术:设计大孔径双胶合透镜组取代传统自聚焦透镜作为光收发装置,以提高系统回光抗偏转能力;应用全反棱镜改变传统测试光路,保证光探头的重复使用,以适应弹道测试系统的需求;引入直流检测端,为干涉条纹的信号处理和系统内触发提供便利。利用该方法在轻气炮速度测速试验中测量轻气弹飞行速度,其测量结果与经验值吻合。该新型冲击波速度测量技术实现了对被测体较长时间段的速度测试,其设备结构简单、灵敏度高、适应性强,可广泛应用于各领域。     

三滚轮整体加载旋转工况光弹流试验机设计及实验

弹流润滑的光干涉法必须采用透明材料,而一般玻璃等透明材料不能承受高的拉应力,且局部柔性加载技术较为困难,制约着有限长线接触光弹流实验的开展。为了弥补目前对有限长线接触光弹流实验研究的不足,设计了一种三滚轮整体加载旋转工况光弹流试验机,并对滚子的弹流油膜形状进行了初步的实验。实验表明,该试验机可以有效地工作在旋转工况下,测量滚子类线接触弹流润滑接触表面的油膜形状及其变化情况,为今后相关弹流润滑成膜机理的理论研究提供有效的实验数据。     

采用粘度可控高水基液润滑的高速动静压陶瓷滑动轴承主轴设计

高速主轴作为高速高精密加工机床的关键技术,直接决定着机床的各项工作性能.文中提出一种对粘度一轴承间隙寻优,从而实现主轴高性能的高速高精密主轴设计方法,并设计出新型绿色、粘度可控的高水基液作为润滑剂,随后通过采用动静压陶瓷滑动轴承的高速主轴热弹流数值计算,确定了润滑剂粘度及主轴系统相关结构参数,最终完成了该高速主轴的结构设计.     

新型X光成像系统及其性能分析

本文设计了新型的X光成像系统，它的核心部件X光影像增强器是一个混合型器件。该成像系统具有数字化、大视野成像和可移动的优点，成像视野在6-15英寸连续可调。在文中，对这种新型成像系统的成像性能进行了定量的评价，并给出了系统所成的图像。结果表明新型X光成像系统的性价比高，可以广泛应用在机场安检、工业探伤、无损检测等领域。     

A study of the development of the stress optic law of photoelastic experiment considering residual stress

Photoelastic experiment has two significant problems. The first problem is manufacturing a model specimen for complicated shapes of structures. The second problem is residual stress contained in the photoelastic model material. In this paper, the stress optic law that can be effecitvely used on photoelastic model materials with residual stress is developed. By using the stress optic law as developed in this research, we can obtain good results in photoelastic experiments using model material in which residual stress is contained. It is assured that the stress optic law developed in this research is useful. Therefore, it is suggested that the stress optic law considering residual stress can be applied to the photoelastic experiment for the stress analysis of the composite materials or bi-materials in which the residual stress is easily contained.     

A study on the development of photoelastic experimental hybrid method for colour isochromatics (I)

Isochromatics obtained from photoelastic experiment shows the stress distributions of the full field of a structure under load. Therefore, stress distributions of the structure can be read at a glance through isochromatics. Many experimental data can be obtained from isochromatics which are then used in various photoelastic experimental hybrid methods for stress analysis. Monochromatic light has however, until now been used in the photoelastic experimental hybrid method to produce black and white isochromatics. The use of black and white isochromatics in photoelastic experimental hybrid method for black and white isochromatics requires high fringe orders in order to obtain sufficient experimental data for photoelastic hybrid techniques. Accordingly, this paper develops the photoelastic experimental hybrid method for color isochromatics in which a fringe order of 1 is enough to gather the experimental data of the photoelastic experimental hybrid method. The method was applied to validate stress concentration problems. Experimental results from this study indicated that the photoelastic experimental hybrid method for color isochromatics is more precise than the photoelastic experimental hybrid method for black and white isochromatics. The use of few fringe orders in photoelastic experimental hybrid method for color isochromatics can offer significant advantages in stress analysis of real components using reflective-type photoelastic experimental method.     

A study on the development of photoelastic experimental hybrid method for colour isochromatics (II)

Using the photoelastic experimental hybrid method, we can obtain stress intensity factors and separate the stress components near the crack tip of any material under various loading conditions from only isochromatics. However, monochromatic light has, until now been used in the photoelastic experimental hybrid method to produce black and white isochromatics. The existing photoelastic experimental hybrid method using black and white isochromatics requires high order fringes to obtain sufficient experimental data for photoelastic hybrid techniques. If a photoelastic experimental hybrid method for colour isochromatics is developed, isochromatics with a maximum fringe order of 2 will be adequate for gathering the necessary experimental data for stress analyses using photoelastic hybrid techniques. Therefore, in this work, photoelastic experimental hybrid method for colour isochromatics of a crack problem was developed, and its superiority demonstrated by comparing its results with the results from black and white isochromatics. The use of few fringe orders in photoelastic experimental hybrid method for colour isochromatics is an important feature of this method. Because of this feature, this method, specifically the reflection type photoelastic method where low fringe orders are produced compared to the transmission type photoelastic method, can be widely used in stress analysis of real components.     

A Photoelastic Method for the Study of Cage Strain in a Rolling Element Bearing

A technique has been developed by which interpretable photoelastic stress patterns can be obtained from rolling element bearing cages while operating under conditions of various speed and load. The test specimen utilized in this study was a 130 mm bore cylindrical roller bearing. A layer of bire-fringent plastic was cemented to the outboard side of the cage of the bearing by means of a reflective adhesive. This plastic material was illuminated by means of high intensity polarized light. This light passed through the birefringent plastic material, was reflected by the reflective adhesive and passed back again through the birefringent material and through another polaroid filter (analyzer). A high speed camera was located behind this second polaroid filter. High speed motion pictures were taken of the photoelastic stress patterns produced in the birefringent material as the test bearing was rotated under radial load. Photoelastic stress patterns recorded on the high speed motion picture film were analyzed and resulted in the determination of the stress distribution along a radial section of the cage.     

光弹性贴片中用宽条带法分离主应变的研究

在光弹性贴片法中，通常利用剪应力差法和斜射法来分离主应变。对于应变梯度不大的平面可以采用条带法来分离主应变，但其应用性较差。本文研究用宽条带法来分离主应变，使条带法得到了进一步的推广和应用，从而为解决复合材料、陶瓷材料等新型材料的表面应力测定问题提供了一种新的研究方法。     

Visualization of fluctuations in internal stress distribution of workpiece during ultrasonic vibration-assisted cutting

The aim of this study is to construct visualization system of stress distribution under ultrasonic vibration-assisted cutting condition in order to investigate the cutting phenomenon. The vibrating cutting edge is considered to be cause of dynamic change of cutting force at ultrasonic frequency. However, many researchers have explained the effect of ultrasonic vibration-assisted cutting by evaluating the time-averaged cutting force, because it is difficult to measure the dynamic cutting force by using dynamometers. In this study, the instantaneous stress distribution on workpiece was visualized by photoelastic method in combination of pulse laser emission synchronized with vibration of cutting edge. Orthogonal cutting test was carried out at low cutting speed relative to vibration speed of insert. A constructed photographic system divided the ultrasonic vibration period of 36.2 μs into 360 points and took one photograph frame at each point. By counting the number of criteria pixels which images the cutting stress, the intermittent cutting condition was evaluated. It was experimentally confirmed that the stress distribution under vibration-assisted condition showed the periodical change synchronized with insert vibration. Because these results are compatible with well-known vibration cutting theories, the imaging system is able to show the periodic change of stress distribution in ultrasonic frequency band. The intermittent cutting condition was affected not only feed speed but also depth of cut. The theory of relative motion between tool and workpiece is insufficient to explain these results. Therefore, remnants formed due to elastic deformation of the workpiece were examined. The vibration cutting dramatically reduced the elastic deformation and the vibration amplitude had effect on the amount of remnant thickness.     

发动机活塞光弹应力试验与有限元分析

依据发动机活塞的机械负荷,介绍了活塞光弹应力试验的模型制造和试验过程,建立了活塞有限元模型,分析了机械边界条件的施加方法.计算与试验结果很好地吻合,为发动机活塞的耦合分析和结构优化提供了可靠依据.     

A novel method for the evaluation of stress-optic coefficient of commercial float glass

The measurement of residual stress in float glass is important in glass industries as they affect their cutting quality. Photoelasticity can be used for residual stress analysis of float glass as they exhibit stress induced birefringence. Stress measurement using photoelasticity necessitates the knowledge of the stress-optic coefficient of float glass. Carrier fringe method in conjunction with digital photoelasticity is used for the photoelastic calibration of float glass. The conventional method of photoelastic calibration is improved to calibrate float glass with residual stress which eliminates the need for annealing them. The new method developed is self consistent as the results are verified by the reconstruction of the composite fringe pattern. The use of the improved method is recommended for calibration of float glass as it takes into account the residual stress in glass sample apart from its potential for automation.     

链轮受力的三维光弹试验研究

用三维光弹实验法对链轮齿的受力进行三维应力分析。确定了链轮齿应力场分布规律及轮齿的最大应力，找出轮齿的危险区域，最后提出了改进措施。     

A study on the analysis of O-ring under uniform squeeze rate and internal pressure by photoelastic experimental hybrid method

There are three kinds of loading conditions applied to the O-ring, The first loading condition is the case in which uniform squeeze rates are applied to the upper side and the lower side of the O-ring (the strain condition). The second loading condition is the case in which uniform squeeze rates are applied to the upper side and the lower side of the Oring and other squeeze rates are applied to the front side of the O-ring. The third loading condition is the case in which uniform squeeze rates are applied to the upper side and the lower side of the O-ring, other squeeze rates are applied to the front side of the O-ring, and internal pressures are applied to another front side of the O-ring(loading condition is the combination of stress condition and the strain condition). In this research, a new photoelastic experimental hybrid method under the third loading condition was developed and it was verified. The stresses of the O-ring under the third loading condition were analyzed by the new photoelastic experimental hybrid method developed in this research. The internal pressures applied to the O-ring were 0.98 MPa, 1.96 MPa, 2.94 MPa and 3.92 MPa. This paper was recommended for publication in revised form by Associate Editor Jooho Choi Jai-Sug Hawong received a B.S. degree in Mechanical Engineering from Yeungnam University in 1974. Then he received his M.S. degree and Ph.D. degree from Yeungnam University in Korea in 1976 and from Kanto Gakuin University in Japan in 1990, respectively. Prof. Hawong is currently a professor at the school of Mechanical Engineering at Yeungnam University, in Gyeongsan city, Korea. He is currently serving as an vise-president of Korea Society Mechanical Engineering. Prof. Hawong’s research interests are the areas of static and dynamic fracture mechanics, stress analysis, experimental mechanics for stress analysis and composite material etc.