Interferometric 45° and 60° strain rosettes measuring

A laser-based technique, referred to as interferometric strain rosettes for measuring three in-plane strains, is presented. The strain rosette consists of three microindentations produced on a specimen surface and can be of two separate forms. The two forms are 45° and 60° rosettes for indentations located at the vertices of a 45° right triangle and an equilateral triangle, respectively. The three indentations for either form can be grouped into three pairs. When the indentations are illuminated with laser light, each pair of indentations acts like a two-point source generating a pair of Young's interference fringe patterns. The fringe spacing is inversely proportional to the separation of the indentations. Because strains cause the separation to change, the fringe spacing also changes. The fringe change is monitored with linear-array diodes and collected real time through a microcomputer system. The three strain components in the directions of the indentation pairs can then be obtained.     

A through interface crack between a ±45° transversely isotropic pair of materials

In this study, the first term of the asymptotic displacement and stress fields is determined analytically for a straight through crack along the interface between a ±45° transversely isotropic pair of materials. Since with this configuration, there is full coupling between the modes, this problem requires a three-dimensional treatment. To calculate stress intensity factors, a three-dimensional M-integral is derived using the asymptotic fields as auxiliary solutions. The displacement extrapolation method is derived as well, and used to check the results obtained by the M-integral. Two numerical test cases are employed to examine the accuracy of both methods. Results obtained for other mechanical problems are presented as well.     

45°角尺角值的检测方法

在JJF1085-2002《水平尺》校准规范中,要求配备专用45°角尺,45°角的角值偏差要求为±2'。角值用角度规检测,很难保证准确度。一般选用的45°角尺的边长都在(400×400)m m以上,用正弦规也无法检测。本文介绍一种简便方法,供参考。一、测量方法将45°角尺放在零级平板上,紧靠定位块,使电感仪测头垂直接触45°工作面(如图1所示),在电感仪指示表上读数;然后移动45°角尺将另一垂直面紧靠定位块,再一次在电感仪指示表上读数,两次读数差即为45°角线值偏差,换算成角值偏差δ,则:δ=ρΔ/L式中:ρ=206265″;L——两测量点间的距离(m m);Δ——…     

Porosity of cement paste cured at 45 °C as a function of location relative to casting position

The influence of location relative to the casting position, on porosity and pore size distribution of cement pastes, was investigated. Three different pastes were prepared at a constant water/binder ratio of 0.45. The pastes were the control paste (CP) in which Portland cement was used and no cement replacement materials were added, pastes with 22% and 9% replacement (by mass) of cement with fly ash (FA) and silica fume (SF), respectively. Paste specimens were cast in cube moulds and were either cured in air at a temperature of 45 °C and relative humidity of 25% for 28 days or moist cured for 14 days after casting at 45 °C, followed by air curing at 45 °C and 25% relative humidity for further 14 days. Samples were taken from various locations of the cube specimens. Porosity and pore size distribution were conducted on the paste samples using the mercury intrusion porosimetry technique.The results show that large differences in porosity and pore size distribution exist between samples taken from different locations relative to casting positions. These differences are larger in pastes subjected to dry curing as compared to pastes subjected to some initial moist curing. The influence of sample location relative to casting position on porosity and pore size distribution of paste is compared with absorption of concrete performed in a previous investigation. The correlation between pore volume of paste and water absorption of concrete is also conducted.     

The effect of fibre rotation in ±45° tension tests on measured shear properties

Non-linear analysis has been carried out on glass/epoxy ±45° tension specimens to quantify the errors involved in deducing the shear stress-strain response from this test. The non-linear geometry effect due to large fibre rotations, large strains and the effects of non-linear shear and transverse material properties are considered. It is shown that at large shear strains the actual ply-level shear stress is much lower than that normally assumed due to the combined effect of fibre rotation and non-linear shear response. There is a large increase in the fibre-direction stress, and this explains the very high values of apparent shear strength which can be obtained with ±45° tension tests. Large transverse compressive stresses can also arise as a result of fibre rotation. However, the errors in shear stress are small at shear strains below about 7%, confirming that the tests are satisfactory for modulus and initial stress-strain measurements.     

镶齿锯片45°倒角加工工艺研究

镶齿锯片每隔一齿有倒45°角的齿。45°倒角要有一定的后角。为加工45°倒角,设计一台专机与卡具,磨头的砂轮轴线与水平锯片成45°角,锯片被安装在能自动分齿的卡具上。     

Accurate comparative determination of the in-plane shear modulus of T300/914 by the iosipescu and 45° off-axis tests

This paper compares the initial shear modulus distributions obtained from [0]₂₀, [90]₂₀ and [0/90]_5s Iosipescu and [45]₂₀ off-axis T300/914 specimens. The data reduction processes for the two tests are presented together with a finite element analysis of the Iosipescu test that enables the determination of correction factors to account for the non-homogeneity of the stress and strain fields along the notch line. A preliminary 45° off-axis test is performed to determine a region of linear elastic behaviour within which the samples are each tested four times. Close examination of the test data leads to a detailed discussion of the quality of the Iosipescu specimens in terms of perpendicularity of the loading surfaces to the lateral faces. The degrees of scatter due to the mechanical loading conditions and to the sample to sample variations are compared.     

宽频带±45°双极化基站天线的设计

本文设计了应用于2G,3G,4G(LTE)的一种宽频带±45°双极化基站天线.天线由两组垂直交叉的蝴蝶结状偶极子天线构成,每一组偶极子天线通过连接同轴线的短截线馈电,从而实现了天线的平面结构.通过在每组交叉偶极子天线上开设3个矩形缝隙和1个V形缝隙,可以有效地拓宽设计天线的阻抗带宽、改善天线的增益.仿真结果表明:该天线可以工作在1.7~2.7GHz频率范围内,两端口的回波损耗大于15dB,两端口之间隔离度大于27dB,半功率波束宽度在65°±3°范围内,整个频段内增益均大于7.7dBi,前后向增益比大于20dB.     

Diffraction contrast analysis of 90° and 180° ferroelectric domain structures of PbTiO3 thin films

Abstract

The ferroelectric domain structure of a PbTiO₃ thin film on (100) SrTiO₃ has been investigated by transmission electron microscopy (TEM). Two types of a-domain were found: one extended through the film to the surface and another comprised small a-domains confined within the film. Dark-field TEM (DFTEM) observation revealed that 180° domains formed near the substrate and stopped their growth 100 nm away from the substrate. The DFTEM observation also revealed that 90° domain boundaries had head-to-tail structures. To confirm the polarization direction obtained by experiments, diffracted intensities under a two-beam condition were simulated using the extended Darwin–Howie–Whelan equations. On the basis of the obtained results, a ferroelectric domain structure model of PbTiO₃ thin films on SrTiO₃ is proposed.     

直裂纹和45°斜裂纹转子系统动力特性对比

对于转子系统,转轴上带有斜裂纹或直裂纹,系统的响应会有一些不同,这些不同是由于直斜裂纹对转轴刚度的不同影响引起的.分析了裂纹深度对直斜裂纹转子的刚度和稳态响应的影响;同时还讨论了速度的变化对直斜裂纹转子的稳态响应的影响.最后实验研究了随速度增长直斜裂纹转子系统的稳态响应.研究结果表明,实验测得的工频分量与二倍频分量的变化趋势与计算结果相符.     

Heat conductivity of water near 4°C

The results of short-term nonsteady-state measurements do not confirm the view that the heat conductivity of water behaves abnormally in the vicinity of 4°C.Notation L thickness of the liquid layer, m - T temperature, K - q heat flux, W/m² - thermal conductivity, W/m·deg K. Indices 0 and L denote the beginning and end of the layer, respectively Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 39, No. 2, pp. 339–342, August, 1980.     

Observation of ferroelectric 180° domains by microphotometry of holographic gratings

A new holographic observation technique for 180° domains is demonstrated with a cerium-doped strontium barium niobate sample containing two antiparallel ferroelectric domains. The method relies on the fact that the phase shift of holographically written refractive-index gratings is +π/2 or -π/2 with respect to the initial light interference pattern depending on the orientation of the domains. As a consequence, readout of these gratings creates at the exit face of the sample new interference patterns shifted by 0 or π with respect to the initial one. These patterns, providing an image of the domain structure, are observed by microscope.     

Heat of Formation of Calcium Aluminate Monosulfate at 25 °C

The heat of formation of calcium aluminate monosulfate, 3CaO·Al₂O₃·CaSO₄·12H₂O, at 25 °C, and of less completely hydrated samples of the same compound, was determined by the heat-of-solution method, with 2N HCl as the solvent, and 3CaO·Al₂O₃·6H₂O(c) and CaSO₄·2H₂O(c), as the reactants. The results were as follows:

Production of high momentum negative pions by 800 MeV protons AT 0° to 20°

The π⁻ yield in the momentum range 500–740 MeV/c produced by 800 MeV protons incident on targets of Be and C has been measured at laboratory production angles between 0° and 20°. The yield of 725 MeV/c π⁻ from Be and C at 0° is a factor of 6 greater than at 20°, for 600 MeV/c π⁻ the factor is 3. The yield from beryllium is typically 30% higher than from carbon.     

Synthesis of nanocrystalline TiO2 at 100 °C

A simple gel to crystal conversion route has been followed for the preparation of TiO₂ at 80–100 °C under refluxing conditions. Freshly prepared titanium hydroxide gel is allowed to crystallize under refluxing and stirring conditions for 6–12 h. Formation of nanocrystallites of anatase is confirmed by X-ray diffraction (XRD) study. The anatase phase converts into rutile when calcined at 700 °C for 12 h. Raman scattering experiments were also performed to confirm both anatase and rutile phases. Transmission electron microscope (TEM) investigations revealed that the average particle size is 10 nm for the anatase phase whereas it is 35 nm for the rutile polymorph.     

Compression of a 0°-ply/acrylic sandwich

The compressive behaviour of a 0°-ply (AS4/PPS) inserted between two acrylic layers is studied experimentally, and results are compared with existing theoretical predictions. A transparent acrylic is chosen so that kink formation in the 0°-ply may be directly observed. Experiments show that failure occurs by catastrophic formation of an in-plane kink band with a kink band angle of 20° to the horizontal axis. Then, as the compression strain is further increased, several additional kink bands appear. The load corresponding to the formation of the first kink is in agreement with theoretical predictions. These experiments confirm that failure initiates by in-plane kinking, and shed light upon the behaviour of an internal 0°-ply inside a multidirectional laminate, especially the propensity for in-plane kinking versus out-of-plane kinking.     

矩形横截面试样经45°角倒棱后弯曲应力的修正计算

提供计算矩形横截面试样经45°角倒棱后弯曲应力和弯曲弹性模量的修正方法。     

Measurement of the monochromatic emissivity of coatings at 100–400°C

Results of measurement of the normal emissivities of certain coatings by a two-beam method in the 2–25 range are reported.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 27, No. 2, pp. 203–207, August, 1974.