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1.
云纹干涉与钻孔法测量搅动摩擦焊接头的残余应力   总被引:1,自引:0,他引:1  
亚敏  戴福隆  吕坚 《实验力学》2002,17(Z1):165-170
搅动摩擦焊是90年代出现的一种新型焊接技术,特别适用于熔化焊接性差的有色金属等材料.搅动摩擦焊接头的残余应力分别具有高应力梯度的特点,传统的应变片钻孔法不能满足测量要求.本文结合云纹干涉法与钻孔法的技术,得到了铝合金薄板搅拌摩擦焊接头残余应力沿深度和沿垂直焊缝方向的分布.  相似文献   

2.
用云纹干涉法测复合材料的固化残余应变   总被引:1,自引:0,他引:1  
云纹干涉法是研究复合材料变形的一种有效方法.本文讨论了用云纹干涉法测量复合材料的固化残余应变,获得了试件表面的位移条纹图,并用电测方法加以验证。  相似文献   

3.
相移云纹干涉法与盲孔法相结合检测复合材料的残余应力   总被引:1,自引:0,他引:1  
常红  姚河省  侯丽丽 《力学季刊》2006,27(3):511-514
本文应用相移云纹干涉法与盲孔法相结合检测纤维增强复合材料的残余应力。盲孔法是工程中被广泛应用的测定残余应力的方法之一,相移云纹干涉方法可得到孔边任意一点的位移信息。由于正交各向异性复合材料在弹性主方向不发生拉剪(或剪拉)耦合效应,所以通过适当读取孔边特殊点的位移,可方便地得到残余应力值。  相似文献   

4.
应用云纹干涉法测量冷挤压孔周残余应力分布   总被引:4,自引:0,他引:4  
本文就冷挤压加工后紧固孔周的残余应力测量问题进行了研究。文中提出了径向切割法以释放欲求剖面的周向残余应力;采用高灵敏度的云纹干涉法测量残余应力释放后引起的附加变形;用载波错位法获得高反差的应变条纹图。  相似文献   

5.
刘欣  周伯明  亚敏  戴福隆 《实验力学》2002,17(Z1):74-80
本文利用单光束楔形镜云纹干涉法代替传统的双光束云纹干涉法进行位移场和应变场的测量.单光束云纹干涉法具有光路简单,不受环境干扰等特点.本文将云纹干涉法的波前理论与近代光学信息技术有机地结合起来,对单光束干涉系统进行了分析,得到了记录的光强和再现的位移应变公式.利用该系统,得到了三点弯矩形梁的全场位移条纹图和应变条纹图.  相似文献   

6.
瓷修复体界面断裂行为的模拟实验研究   总被引:1,自引:0,他引:1  
方如华  王冬梅 《力学季刊》2002,23(3):302-310
本文利用云纹干涉法和云纹干涉--有限元混合法,对瓷修复体的模拟双材料模型界面断裂问题进行了实验研究。用云纹干涉和数字错位云纹干涉法测量带边裂纹的双材料四点简支梁在剪切作用下界面表面的剪应变分布及界面两侧局部表面的位移场,实验表明,由于界面两两侧材料力学性质不同,表现出界面剪切断裂问题的非称性和裂尖附近复合型断裂的特点;用云纹干涉法和有限元法相结合的混合法对粘接界面角点应力奇异性进行研究,并对角点附近应力应变场作了分析,得到了应力奇异指数与边界楔角,载荷的关系,证明了用界面应力强度因子Kf来描述界面端部区域应力分布的公式,并得到了双材料界面端部区域的应力应变分布情况。本文的实验结果为进一步研究口腔金瓷修复体界面的优化设计提供了基础,同时也说明云纹干涉法对于双材料界面断裂行为的研究是有效的。  相似文献   

7.
SiC/Ti-15-3复合材料基体与增强体之间的热膨胀系数存在显著差异。在复合材料制造过程中经高温冷却后,在基体与增强体的界面会产生热残余应力场。此残余应力场对复合材料的力学性能会产生重要的影响。本文运用纤维推出法推出部分SiC纤维后,采用显微云纹干涉法在细观尺度研究了上述界面处的热残余应力,得到了分辨率较高的云纹图,并由此计算出了孔边处的残余应力。用有限元软件对界面热残余应力进行了数值模拟分析。实验结果表明,显微云纹干涉法可以用来测量直径为0.1 mm左右的纤维界面附近的残余应力场,在此尺度下,使用显微云纹干涉法比用电子束云纹法更方便。  相似文献   

8.
钻孔法和光栅应变花测试复合材料的残余应力   总被引:3,自引:0,他引:3  
残余应力对材料、结构的疲劳强度和使用寿命等性能的影响早已为人们所熟知,由于它的大小、方向和分布随制造加工或处理方法不同而有很大的随机性,国内外对它的研究很重视。对于各向异性的复合材料,随着加上生产制造过程及工艺参数的不同,其中的残余应力的大小、方向等就更加复杂。从国内外对残余应力的研究中,可以看出大多数都着重于实验研究。本文应用钻孔法和云纹干涉技术的成果,针对残余应力测试中的特点,尤其是在利用钻孔法和云纹干涉技术测试残余应力时存在的问题,在目前绝大多数云纹干涉技术所使用的正交光栅的基础上,提出并研制出一种三个方向的光栅,即在原来 0°、90°两个方向光栅上,再加上一个 45°方向的光栅,在进行云纹干涉测试时,一次加载时就可以同时测试出三个独立的位移场:u场、v场和s场,利用这三个位移场就可以得到相应的三个应变:ε0、ε90和ε45,进而可以计算得到相应的应力。  相似文献   

9.
无损电测解析法测定焊接容器的残余应力   总被引:2,自引:1,他引:1  
张亦良  程咏梅 《实验力学》1994,9(4):367-375
本文从塑性增量理论出发,论述了无损电测解析法的基本原理和应用此法确定残余应力的基本步骤,并将其应用大型球罐的现场测量。其特点是在容器例行的水压试验中只需应用电阻应变片测量应变即可确定残余应力用此法所得结果同盲孔法所得结果进行了对比。表明具有一定的工程精度。  相似文献   

10.
戴福隆  卿新林 《力学学报》1993,25(2):193-200
本文将云纹干涉法与载波法、倍增技术相结合,提出一种位移场和应变场云纹干涉条纹倍增方法,该方法使得云纹干涉法测量灵敏度提高四倍以上。文中对该方法给出了严格的理论推导和实验验证。  相似文献   

11.
The physical and mathematical principles of the method of electrogas-and electrohydrodynamic conversion of electrical signals to pneumatic (hydraulic) signals and vice versa for control of gas and liquid jets and flows in electropneumohydraulic systems are considered. St. Petersburg State Technical University, St. Petersburg 195251. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 2, pp. 25–31, March–April, 2000.  相似文献   

12.
This paper describes a method of presentation of fatigue data on three commonly used aircraft materials, 2024-T3 and 7075-T6 aluminum alloys and normalized SAE 4130 steel, such that variations in fatigue strength with stress-concentration factor can be shown. Comparisons of the fatigue strengths of 2024-T3 and 7075-T6 aluminum are made for the most useful range of stress-concentration factors. Static-strength results of notched and unnotched specimens of the three materials are presented to show how the strength varies with some parameters of the stress concentration. Comparison of the data with one theory for the strength of cracked specimens was made.  相似文献   

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14.
STICTION AND ANTI—STICTION IN MEMS AND NEMS   总被引:6,自引:1,他引:6  
Stiction in microelectromechanical systems (MEMS) has been a major failure mode ever since the advent of surface micromachining in the 80s of the last century due to large surfacearea-to-volume ratio. Even now when solutions to this problem are emerging, such as self-assembled monolayer (SAM) and other measures, stiction remains one of the most catastrophic failure modes in MEMS. A review is presented in this paper on stiction and anti-stiction in MEMS and nanoelectromechanical systems (NEMS). First, some new experimental observations of stiction in radio frequency (RF) MEMS switch and micromachined accelerometers are presented. Second, some criteria for stiction of microstructures in MEMS and NEMS due to surface forces (such as capillary, electrostatic, van der Waals, Casimir forces, etc.) are reviewed. The influence of surface roughness and environmental conditions (relative humidity and temperature) on stiction are also discussed. As hydrophobic films, the self-assembled monolayers (SAMs) turn out able to prevent release-related stiction effectively. The anti-stiction of SAMs in MEMS is reviewed in the last part. The project supported by the Distinguished Young Scholar Fund of NSFC (10225209), key project from the Chinese Academy of Sciences (KJCX2-SW-L2) and National “973” Project (G1999033103)  相似文献   

15.
本文针对现代换热设备设计、两相流动与传热研究的需要,介绍了可供科研使用的水和水蒸汽物性计算方法,完善了计算程序。根据超临界锅炉设计中的超临界水的物性计算,两相流研究和换热设备动态特性研究中对物性导数计算的需要,提供了两个算例,并进行了定性分析。  相似文献   

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17.
The aerodynamic forces and flow structures of two airfoils performing “fling and subsequent translation“ and “translation and subsequent clap“ are studied by numerically solving the Navier-Stokes equations in moving overset grids. These motions are relevant to the flight of very small insects. The Reynolds number, based on the airfoil chord length c and the translation velocity U, is 17. It is shown that: (1) For two airfoils performing fling and subsequent translation, a large lift is generated both in the fling phase and in the early part of the translation phase. During the fling phase,a pair of leading edge vortices of large strength is generated; the generation of the vortex pair in a short period results in a large time rate of change of fluid impulse, which explains the large lift in this period. During the early part of the translation, the two leading edge vortices move with the airfoils;the relative movement of the vortices also results in a large time rate of change of fluid impulse, which explains the large lift in this part of motion. (In the later part of the translation, the vorticity in the vortices is diffused and convected into the wake.) The time averaged lift coefficient is approximately 2.4 times as large as that of a single airfoil performing a similar motion. (2) For two airfoils performing translation and subsequent clap, a large lift is generated in the clap phase. During the clap, a pair of trailing edge vortices of large strength are generated; again, the generation of the vortex pair in a short period (which results in a large time rate of change of fluid impulse) is responsible for the large lift in this period. The time averaged lift coefficient is approximately 1.6 times as large as that of a single airfoil performing a similar motion. (3) When the initial distance between the airfoils (in the case of clap, the final distance between the airfoils) varies from 0.1 to 0.2c, the lift on an airfoil decreases only slightly but the torque decreases greatly. When the distance is about lc, the interference effects between the two airfoils become very small.  相似文献   

18.
In this paper, we obtain the sufficient conditions under which there exists the fixed point of sum and product about concave and – convex operators in the positive cone of linear semi-order space, and the iterative procedure and error estimate can be given. The relation between eigenvalue and eigenelement will also be studied in this paper.  相似文献   

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