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1.
A general stress-optic law in a plate made of a single crystal with birefringence is developed, the plate has an arbitrary
crystallographic direction. From the general stressoptic law, a condition for obtaining stress distributions in the plate
under a plane stress state is derived. Some optical and mechanical properties when the plate is used as a photoanisotropic
model are also explained. Experiments on silicon beams in pure bending are performed by using an infrared photoelastic method.
Experimental results show that the stress-optic law is valid. The optical and mechanical properties of silicon beams are shown
in tables. 相似文献
2.
Transmission photoelastic patterns for generally and specially orthotropic beams and an isotropic beam are presented. Theoretical
isochromatic and isoclinic results for these beams, calculated from classical elasticity stress equations and stress-optic
laws, are also presented and compared with experiment. The agreement between the theory and experiment is excellent. For the
orthotropic beams, a stressoptic law which accounts for the effects of residual birefringence was used. The residual birefringence
observed for the composite used in this study is greater than one fringe order and results from a matrix residual tension
which is about one fourth of the resin's ultimate tensile strength. Finally, the influence of such a large residual birefringence
on beam and calibration photoelastic data is discussed in detail.
Paper was presented at the 1986 SEM Spring Conference on Experimental Mechanics, held in New Orleans, LA on June 8–13. 相似文献
3.
A method of producing transparent model materials for photo-orthotropic-elastic studies is presented. This material fabricated from glass fibers and a modified polyester matrix exhibits continuous relatively smooth fringe patterns which are linearly related to the state of stress. As such, the heterogenous material can be treated as a homogenous medium with orthotropic properties. Three photoelastic constantsf L ,f T andf LT are necessary to describe the photoelastic response of the orthotropic materials to a general state of stress. Methods are established for predicting these photoelastic constants from the properties of the constituents. These methods are based on stress proportioning between the fibers and the matrix and upon the linear summation of the retardation from each constituent. The relations derived forf L ,f T andf LT were verified experimentally and found to be in close agreement with measured values. A stress-optic law is derived on the basis of stress partitioning between the two constituents in a unidirectionally fiber-reinforced laminate. The adequacy of this stress-optic relation is confirmed by experimental verification. Comparison of this stress-optic relation with the expression advanced by Pih and Knight shows the validity of their initial concepts but the inadequacy of their partitioning functions. Detailed comparison of the stress-optic law with the analog relation proposed by Sampson shows excellent agreement. Indeed, the use of Sampson's stress-optic law is recommended and the law based on stress partitioning is to be considered as a fundamental theoretical proof of the Sampson relation. Finally, the applicability of Sampson's stress-optic law to bidirectionally reinforced materials was confirmed with a thorough experimental verification. 相似文献
4.
正交异性动态光弹性方法的几个基本问题的研究 总被引:2,自引:0,他引:2
文章对适用于动态研究的正交异性光弹性复合材料进行了分析,详细说明了光弹性复合材料中残余双折射的确定方法;基于静态下Hyer和Liu应力-光性定律,提出了正交异性动态应力-光性定律,并对正交异性材料的动态力学参数及动态光弹性常数给出了实用的标定方法;最后,利用三个单轴压缩试件(0°,90°及45°),采用动态应变测量方法,证实了单轴应力状态下正交异性动态应力-光性定律的正确性。 相似文献
5.
6.
N. K. Sinha 《Experimental Mechanics》1978,18(1):25-34
Thermal tempering is widely used to manufacture safety glass for economic as well as for certain safety measures. Laboratory investigations of the tempering process and the resultant strengthening effect are generally limited to rectangular specimens. Results are, therefore, appropriate for this particular geometry. This paper describes a simple stress-state model of a tempered flat glass specimen. the model, developed using photoelastic equations to determine the three-dimensional stress components, was used to predict the transient birefringence in a rectangular glass specimen subjected to uniform and symmetrical heat-transfer conditions, at a temperature where glass behaves as a perfect elastic material with no stress relaxation within the experimental time. A method of determining the coefficient of heat-transfer rate was then developed based on the analysis of the transient birefringence. This technique uses the glass specimen as an optical transducer, and does not affect, in any way, the natural flow of heat by forced convection or contact cooling. 相似文献
7.
8.
This paper describes an experimental method whereby the amplitude of cyclic stresses may be readily determined by time-averaged photoelasticity. Using an ordinary polariscope with a monochromatic-light source, ‘time-averaged isochromatics fringes’ are formed if the photographic film in the camera is exposed with an exposure time equal to one or several periods while the photoelastic model is undergoing steady-state cyclic loading. The fringe pattern depicts amplitudes of the oscillating stresses according to the zeroth-order Bessel function. These properties permit the determination of a time-averaged cyclic stress-optic law. It is also possible to use the method to determine time-averaged isoclinics. The method has great potentiality in the study of in-plane vibrations. 相似文献
9.
本文系统地讨论了以动态流体双折射方法实现心血管内流场的高质量模拟测试的基本理论和实用分析方法。首先,分析了稳态流动和振荡剪切流中光──力学关系的差异,提出脉动流中简化的光──力学关系假设,然后给出其适用于低频脉动流动的实验验证。为使医学和生物力学研究人员易于掌握,又提出一种简单新颖的局域分析法。 相似文献
10.
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
11.
Gary L. Cloud 《Experimental Mechanics》1969,9(11):489-499
Polycarbonate resin possesses optical and mechanical properties which make it particularly suitable for certain experimental investigations, including two-and three-dimensional photoelastic analysis. The ductility and transparency of this material might be usefully employed in photomechanical investigations of plastic and viscoelastic response. The similarity of the stress-strain law of polycarbonate to that of mild steel could simplify the similitude problem. In addition, its spectral transmittance in visible and infrared makes polycarbonate useful for studies of material properties and structure. The optical creep of polycarbonate is respresented by a normalized creep coefficient. The relationship of this factor to the theory of viscoelasticity is discussed, and the conditions for a valid calibration of birefringent materials are reviewed. The wavelength dependence of relative retardation is represented by the normalized retardation, from which the dispersion of birefringence can be deduced. The stress-birefringence-time-wavelength characteristics of two brands of polycarbonate resin were determined. Because of residual birefringence, it was necessary to heat treat the resin at about 146°C, and properties of both annealed and unannealed resins are presented. Retardation was measured over the visible and near-infrared portions of the electromagnetic spectrum (407 nm to 1900 nm). There exists a definite relationship between dispersion of birefringence, which amounts to 14 percent in visible, and the infrared spectral transmittance, which is indicative of material structure. 相似文献
12.
Hui Pih 《Experimental Mechanics》1963,3(2):33-40
Studies of the two-dimensional dynamic stress-optic law were made using Castolite circular disks under diametral impact load. The dynamic stress-fringe relationship of Castolite was found to be approximately linear. The dynamic fringe values were slightly lower than the static values. In four of the five specimens used the maximum difference was 8.2 percent. Previous work on the dynamic stress-optic calibration was limited to cases of one-dimensional stress.A new dual-beam cathode ray oscilloscope and two dualtrace plug-in preamplifiers were adapted for this work. Taking advantage of symmetry, three strain components at an arbitrary point in the disk and the birefringence at the symmetrical point were recorded in one photograph during a single impact.was formerly associated with International Business Machines Corp., Endicott, N. Y.Paper was presented at 1962 SESA Annual Meeting held in Milwaukee, Wis., on October 24–26. 相似文献
13.
Walter Schumann 《Experimental Mechanics》1973,13(6):225-231
In a general view, a comparison is made of different optical methods where either photoelastic models, opaque bodies with transparent coatings or noncontacted objects are examinèd with coherent light. Further, it is tried to show that some common features are contained by the three groups. These aspects concern the separation, by controlled determination, of displacement, rotation and strain (or of certain of their components), the multiplication of the optical effects in the detection and the elimination of secondary influences. In particular, the noncontacting method of wavefront reconstruction with double-exposure holograms is discussed and the role of the localization condition for the fringes in space is analyzed. On the other hand, it is illustrated that, besides the generally known birefringence and diffraction. use could be made of nonorthodox effects like rotation of the plane of polarization, second-harmonic generation in nonlinear optics, etc. This may, for instance, contribute to the optical instrumentation when transparent models and bodies with photoelastic coatings are investigated under the above aspects. 相似文献
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15.
本文提出一种新的计算机辅助光弹性应力分析方法,它具有全电子记录、全自动应力场分析、光路简单等优点。相位技术的采用使数据精度大大提高。文中给出了几种实验光路以及提高图象质量的方法,用对经受压圆盘光弹实验证明了方法的可行性。 相似文献
16.
The photoelastic method was used to investigate the nature of the local stress field at a sharp corner of a wedge that was compressed against a larger body. Planar wedge specimens made of photoelastic material were compressed against a half plane (larger body) of identical material at various load levels. Several wedge angles were studied. The nature of the singular stress field postulated by linear elastic analysis was verified and the strength of the singularity was obtained by plotting the variation of fringe order as a function of radial distance from the sharp corner on a logarithmic scale. The experimental results were found to be in good agreement with the theoretical predictions. The effect of interface friction and the effect of rounding off the sharp edge are brietly discussed. 相似文献
17.
T. Y. Chen 《Experimental Mechanics》1997,37(3):232-236
A new approach for digital determination of photoelastic birefringence is proposed. The relationships between the intensity values and the fringe orders of two wavelengths are derived. This scheme allows for automatic determination of fringe orders of a full-field photoelastic fringe pattern without using zero-order fringes in the fringe pattern. The usefulness of this method was demonstrated on two experimental fringe patterns with different wavelengths. 相似文献
18.
Henderiekus G. B. Allersma 《Experimental Mechanics》1982,22(9):336-341
An optical measuring method and a calculation procedure for determining the distribution of the stress tensor in a plane-strained three-dimensional assembly of random-shaped photoelastic particles are described. The stress tensor at an arbitrary point of the model is determined by an integration procedure, based on the equations of equilibrium of stresses. The distribution of the principal-stress direction and the relative principal-stress difference and at least two normal stresses in a plane have to be known to perform the integration. The distribution of the principal-stress directions and their difference are measured optically by scanning the model with an optical filter system with a single rotating polarizer. 相似文献
19.
复合材料光弹性分析的工程方法 总被引:1,自引:0,他引:1
本文在推导均衡光弹性复合材料应力(应变)—光定律的基础上,导出了均衡光弹性复合材料的近似应变—光定律。然后加以推广,提出适用于一般光弹性复合材料的近似应变—光定律.精度分析及实验验证表明:作为工程计算,在采用本文推荐的参数时,光弹性复合材料可视作各向同性材料进行光弹性分析。 相似文献