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1.
对于ARALL层板受硬物撞击所激发的应力波的传播问题,以粘弹性表征阻尼,采用一阶剪切理论在柱坐标系统中建立动力学方程组,寻求柱面波的解答,求得沿不同方向传播的应力波的相速度谱及衰减谱。采用动态实时实验技术,进行了大尺寸ARALL层板撞击应力波的实验研究。对比结果表明,不同方向弥散特性的理论预测与实测符合良好,衰减谱的测定离散性较大,其预测方法有待于进一步验证。 相似文献
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可视化技术及其在光测力学中的应用 总被引:2,自引:0,他引:2
本文探讨了可视化软件系统的开发及可视化技术在光测力学中的应用问题。介绍了我们开发的条纹图象处理软件系统的视—算一体化的图象处理功能;应力波传播的波前可视化;应力主方向的全场彩色显示;及单向拉伸实验的干扰的特征可视化 相似文献
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纤维增强复合材料高应变率拉伸实验技术研究 总被引:6,自引:0,他引:6
本文对基于分离Hopkinson杆的反射式纤维增强复合材料动态拉伸实验技术进行了研究讨论。对加载杆中可能影响拉伸应力波波形实验分析的所有干扰波进行了较系统地定量分析研究,认为产生于试样端头与加载杆界面处的两主要干扰波对希望得到的应力波的测量和判别具有严重的不利影响,因此拉伸实验设计必须避开该主干扰波的重叠影响。文中对动态拉伸实验装置、实验要求及信号采集等作了分析。根据对试验结果的分析,针对复合材料动态拉伸实验技术的若干问题提出了一些处理方法和建议,诸如干扰波的规避、冲击信号合理测点的选取、加载杆长度匹配、复合材料拉伸试样的设计要求以及加载连接等问题。这些方法和建议包括在加载杆特定段上贴应变片,考虑到实验的准确性一般不用反射波进行数据计算处理,尽量缩短试样标距等。 相似文献
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采用1级气炮加载技术和锰铜应力计多点测试技术,开展了C30混凝土在平板撞击条件下的冲击压缩实验研究。基于锰铜应力计实测的应力波形,研究了混凝土中冲击波的传播特性,结果显示冲击波的应力峰值随传播距离呈现明显的衰减特性,衰减过程可分为2个阶段。在早期阶段,卸载波没有赶上前面传播的冲击波,冲击波应力峰值衰减较慢,主要是混凝土材料的本构粘性效应所引起的;而后期阶段应力峰值的快速衰减则归因于混凝土材料的本构粘性效应、后续的来自飞片自由面的反射波追赶卸载、边侧稀疏波卸载及波传播的几何弥散效应的共同作用;另外,冲击波在混凝土中传播的升时也随着传播距离逐渐增大,即由强间断波逐渐转化为弱间断波。 相似文献
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利用等应变测试法获取了304及316L激光焊接焊缝材料的准静态应力应变曲线,发现焊缝材料
具有明显的细晶硬脆化趋势。利用SHTB技术对304、316L及焊接构件材料高温动态力学性能进行了研究。
根据动态实验数据对不锈钢304及316L母材应变率及温度相关的Johnson-Cook本构方程参数进行了拟合。
利用LS-DYNA建立了SHTB动态拉伸实验数值模型,发现了在应力波加载初始阶段由于结构效应及材料
阻抗不匹配引起的应力不平衡现象。通过动态实验与数值模拟相结合的方法确定了焊缝材料的应变率相关
本构参数。 相似文献
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We studied the dynamic response of a two-dimensional square packing of uncompressed stainless steel spheres excited by impulsive loadings. We developed a new experimental measurement technique, employing miniature tri-axial accelerometers, to determine the stress wave properties in the array resulting from both an in-plane and out-of-plane impact. Results from our numerical simulations, based on a discrete particle model, were in good agreement with the experimental results. We observed that the impulsive excitations were resolved into solitary waves traveling only through initially excited chains. The observed solitary waves were determined to have similar (Hertzian) properties to the extensively studied solitary waves supported by an uncompressed, uniform, one-dimensional chain of spheres. The highly directional response of this system could be used as a basis to design granular crystals with predetermined wave propagation paths capable of mitigating stress wave energy. 相似文献
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Nelson N. Hsu 《Experimental Mechanics》1974,14(5):169-176
Stress-induced optical birefringence in transparent materials has long been a common technique of stress analysis. Although
stress-induced acoustic birefringence was discovered more than 20 years ago, its development and actual applications are still
limited. This paper will look at the similarities and differences between the propagation of light waves in photoelastic materials
and the propagation of ultrasonic waves in deformed solids. Critical comparisons of the experimental methods employed in photoelasticity
with those available in modern ultrasonic measuring technique show why previous studies on ultrasonic measurement of stresses
were not very successful.
A new experimental technique is devised for using ultrasonic waves for stress analysis. The technique employs a single rotatable
10-MHz shear transducer as the transmitter and receiver of ultrasonic pulses. The enlarged display of the 10-MHz modulated-pulse
pattern of reflected echoes provides a convenient way to determine the directions of principal axis of the stress within ±3
deg. The pulse-echo-overlap method is used to measure the absolute velocities of the two principal shear waves. The difference
in principal stresses is then calculated from the velocity measurements. Test results of common structural-aluminum and steel
specimens under uniaxial compression show a linear relation between the velocity changes and the applied stress. Ultrasonic
measurements of stress distribution in a 6.35-cm diameter, 1.9-cm-thick aluminum disk under diametric compression are also
reported.
Paper was presented at Third SESA International Congress on Experimental Mechanics held in Los Angeles, CA on May 13–18, 1973. 相似文献
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A device for measuring the velocity of ultrasonic waves: An application to stress analysis 总被引:3,自引:0,他引:3
In this paper we present a device for the practical application of an ultrasonic critical-angle refractometry (UCRfr) technique.
UCRfr is a technique for measuring the velocity of longitudinal, shear and Rayleight waves, developed to improve the traditional
ultrasonic methods for measuring the stress level in materials by means of acousto-elasticity. The technique consists of relating
the variations in wave propagation velocity to variations in the angle of refraction at the interface with a second medium.
Variations in the angle of refraction are determined on the basis of delay in receiving of the same wave at two different
points.
The study deals with the measurements of velocity changes of longitudinal wave due to uniaxial stress. In the present work
the effects of stress on aluminum and steel specimens have been studied.
Experimentation has show the potential of the technique for stress measurement; on the other hand, when the applied stress
is known, it allows the measurement of the acoustoelastic constants of longitudinal waves.
As regards measuring variations in velocity induced by stress, using this method it is possible, with a suitable choice of
the material the device is made of, to isolate the effects of stress on velocity from the possible effects of temperature. 相似文献
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Hu Chao Ma Xingrui Huang Wenhu 《Acta Mechanica Solida Sinica》1997,10(2):167-178
By using the complex variable method and conformal mapping,the diffraction of flexu-ral waves and dynamic stress concentrations in thick plates with a cavity have been studied.A generalsolution of the stress problem of the thick plate satisfying the boundary conditions on the contour of anarbitrary cavity is obtained.By employing the orthogonal function expansion technique,the dynamicstress problem can be reduced to the solution of an infinite algebraic equation series.As an example,the numerical results for the dynamic stress concentration factor in thick plates with a circular,ellipticcavity are graphically presented.The numerical results are discussed. 相似文献
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Using the complex variable method and conformal mapping, scattering of flexural waves and dynamic stress concentrations in
Mindlin's thick plates with a cutout have been studied. The general solution of the stress problem of the thick plate satisfying
the boundary conditions on the contour of cutouts is obtained. Applying the orthogonal function expansion technique, the dynamic
stress problem can be reduced into the solution of a set of infinite algebraic equations. As examples, numerical results for
the dynamic stress concentration factor in Mindlin's plates with a circular, elliptic cutout are graphically presented in
sequence.
The project supported by the National Natural Science Foundation of China 相似文献
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超声纯横波法测试45#钢的内部应力 总被引:1,自引:1,他引:1
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。 相似文献
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The propagation of stress waves in pyramids was studied photoelastically with the application of a laser-photomultiplier tube system and an internal polariscope for recording moving fringes. Dispersion and attenuation of stress waves were considered in a straight bar, a 5-deg pyramid, and a 20-deg pyramid made of Hysol 4290 epoxy plastic. In the straight bar and 5-deg pyramid, longitudinal waves propagate without any dispersion even though the waves attenuate as they progress down the models; in the 20-deg pyramid, however, the dispersion of the stress waves is quite significant. The distributions of the axial and radial stresses and the photoelastic fringe patterns obtained on the 20-deg pyramid show that the stress wave front is spherical with the maximum stress along the central axis of the pyramid. A one-dimensional theory of wave propagation without correction factors in a small-angle infinite cone compares well with the experimental results. 相似文献
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Dynamic photoelasticity in conjunction with high-speed photography was utilized in experiments to study the interaction of stress waves with a running crack. Experimental data were analyzed to study the effect of wave scattering about a moving crack tip. The results indicated a strong influence of stress waves on crack-propagation behavior and crack branching. 相似文献
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Zirka A. I. Malezhik M. P. Chernyshenko I. S. Sheremet G. P. 《International Applied Mechanics》2004,40(7):810-813
The stress wave field and the behavior of waves near the free boundary in an orthotropic plate and at the interface between two anisotropic media are studied. The results presented were obtained using the dynamic photoelastic method and optically sensitive fibrous models. Experimental data for impulsively loaded plates with various boundary conditions are analyzed 相似文献
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This paper presents a nondestructive stress evaluation technique using the ultrasonic interference spectrum of leaky Lamb
waves. By using a specific pitch-catch ultrasonic setup, the symmetric and antisymmetric modes of Lamb waves in a finite plate
are decoupled, leading to simple relationships between the modal frequency spacing of two adjacent modes in the interference
spectrum and the acoustic wave velocities that are functions of stress. As a result, the stress in the plate can be determined
by measuring the modal frequency spacing instead of the relative flight times to calculate the acoustic wave velocity. Extensive
experiments were carried out to verify the viability and robustness of the new technique using a simple testing system. It
has been demonstrated that the new technique is about 25 times more accurate than existing flight-time approaches using the
same testing system. The experimental results agree well with the results obtained by other ultrasonic methods using expensive
equipment. 相似文献