RBS measurements of the nitrogen concentration in diamonds

The nitrogen content in a depth up to 500 Å of three type IaA, two mixed type and two type IaB diamond plates has been determined by Rutherford backscattering spectroscopy (RBS). The natural concentration of carbon-13 served as an intrinsic reference for an absolute determination of the nitrogen content. The RBS results are compared with the nitrogen concentration, obtained from IR-absorption measurements.     

用减少弯曲刚度法研究非对称复合材料层压板的弯曲

本文用减少弯曲刚度法把考虑横向剪切变形影响的非对称层压板的弯曲问题形式上作为对称问题来处理,从而大大简化求解过程.从数值结果看,只要铺层数大于2,使用减少弯曲刚度法所产生的误差很小.      

A new analysis of nonlinear free vibration behavior of bi-functionally graded sandwich plates using the p-version of the finite element method

Geometrically nonlinear vibration of bi-functionally graded material (FGM) sandwich plates has been carried out by the p-version of the finite element method (FEM). The bi-FGM sandwich plate is made up of two face-sheet layers of two different FGM and one layer of homogeneous core. The nonlinear equations of motion of bi-FGM sandwich plates are establish using the harmonic balance method and solved iteratively by the linearized updated mode method. The effects of amplitude vibration, mechanical properties, geometrical parameters, thickness ratio of bi-FGM layers, and volume fraction exponent on the nonlinear vibration behavior of bi-FGM sandwich plates are plotted and investigated.     

翼缘削弱型钢梁的整体稳定性分析

针对钢框架梁翼缘削弱式(RBS)节点梁的整体稳定性能进行了分析。采用能量法研究了不同荷载作用下RBS 梁的整体稳定性能, 将梁翼缘削弱段刚度采用等效折减刚度进行分析, 得到RBS 梁侧向弯扭失稳的临界荷载, 并与等截面梁临界荷载进行对比。讨论了不同削弱参数下RBS 梁的临界弯矩变化规律, 并通过有限元数值计算验证了削弱参数对RBS 梁弯扭失稳临界弯矩的影响。研究结果表明:RBS 梁削弱参数整体对侧向弯扭失稳影响明显, 其临界弯矩值较同尺寸的普通钢梁明显降低, 工程设计中应考虑其不利影响;RBS随梁跨度的增加, 削弱段局部刚度对整段梁的刚度影响作用减弱, 当RBS梁的高跨比较小时, 可以忽略削弱参数对临界弯矩的影响。     

防屈曲可更换伸臂桁架弦杆抗震性能试验研究

为提高伸臂桁架弦杆的延性变形能力和震后可修复能力,提出了一种防屈曲可更换伸臂桁架弦杆.为研究上述新型弦杆的可行性和可靠性,采用1∶3的缩尺比例,设计制作了 1个传统削弱式截面(reduced beam section,RBS)弦杆和2不同构造形式的新型防屈曲可更换弦杆,开展了拟静力低周往复加载实验.对新型弦杆的变形能力...     

Constraint loss correction for assessment of CTOD fracture toughness under welding residual stress. Part I: Methodology using the equivalent CTOD ratio

This part I of a two-part paper presents a method of assessing the effects of welding residual stress and constraint loss on the cleavage fracture of a wide plate subjected to membrane stress based on the Weibull stress criterion. It has been found that the Weibull stress criterion is efficient for evaluating the fracture instability of wide plates with and without a welding residual stress field. The concept of an equivalent crack-tip opening displacement (CTOD) ratio β_r under a welding residual stress field is introduced for assessment of constraint loss effects on CTOD fracture toughness of wide plates. The equivalent CTOD ratio β_r is defined as the ratio of the CTOD in the standard fracture toughness specimen to the CTOD in a wide plate with a welding residual stress at the same level of the Weibull stress. Fracture assessment procedures using β_r for wide plates are shown within the framework of the failure assessment diagram. It has been found that the excessive conservatism observed in the conventional procedure can be reduced reasonably by applying the proposed method. The companion part II of the paper presents applications of the CTOD toughness correction method using β_r to the fracture test data of welded joints and verifies the proposed method in the ductile-brittle transition temperature region.     

The effect of rotatory inertia on the dynamic response of laminated composite plate

The strip element method (SEM) is extended to include rotatory inertia for analysing the dynamic response of laminated composite plates. The transient responses of rectangular symmetric laminated plates are computed for various loading using the newly developed SEM program. The effect of the rotatory inertia is investigated for plates of different thickness. It is found that the rotatory inertia has less effect on thin plates whose thickness–length ratio is less than 1/20, but significant effect on thicker plates. The effects of other parameters such as elastic constants, material density and fiber orientation on the responses of plate are also studied and discussed in detail.     

Reliability-guided Rayleigh backscattering spectrum correlation method for distributed strain measurements in optical fibres

We present a method of reliability-guided Rayleigh backscattering correlation for distributed strain measurements in optical fibres. In this method, a reference Rayleigh-backscattering-spectrum (RBS) range that is larger than the measurement RBS range is defined to extend the matching range. To obtain the best match between reference and measurement spectra, the zero-mean normalized cross correlation (ZNCC) is employed to evaluate the degree of similarity. The path for searching the maximum similarity matching pattern is guided using Newton’s iteration method. The reliability of the computed RBS shift is identified by the ZNCC coefficient distribution. The experiments show that the proposed method has high reliability in computing the RBS shift. Even at a relatively large strain (e.g. 5000?µ?), the proposed method can stably demodulate the strain within a relative error of ?1% and a spatial resolution of 1.6?cm over a 22-meter-long single-mode fibre. This shows that the proposed method has an advantage in regard to relatively large strain measurements.     

Interlaminar stress distribution of composite laminated plates with functionally graded fiber volume fraction

Various functionally graded design methods have been proposed recently for fiber reinforced composite plates. The laminates with variable fiber spacing along the thickness direction are focused on in this paper. Fiber volume ratio distribution functions are defined separately in each single layer. Classic state space method as well as differential quadrature state space method are utilized here for different boundary and plied conditions. For the latter method, a sub-layer based scheme, which has both high accuracy and less numerical capacity, is suggested for functionally graded plates. Numerical examples indicate that the non-uniform distribution of fibers rearranges the stress field, of which the in-plane stresses are sensitive to the fibers’ distribution, while the transverse stresses are not affected so much. In-plane stresses near interfaces would decrease if the fiber ratio reduces in this region, which provides a method to resolve the interfacial stress concentration problems.     

The effect of anisotropy on post-buckling behavior of laminated plates using semi-energy finite strip method

The effects of anisotropy (i.e. the ratio of longitudinal modulus of elasticity to transverse modulus of elasticity of a rectangular plate) on buckling and post-buckling performance of laminated plates under uniform end-shortening have been studied in this paper by implementing a Rayleigh–Ritz approach and a finite strip approach based on the concept of a rigorous post-buckling solution for composite plates and plate structures, namely the semi-energy approach. To validate the results, they are compared with those obtained from finite element method of analysis. The study of results has revealed that the buckling and post-buckling response of the laminates is significantly influenced by the changing of the anisotropy ratio.     

Rutherford backscattering spectrometry and computer simulation for the in-depth analysis of chemically modified poly(vinylidene fluoride)

The alkaline treatment of poly(vinylidene fluoride) (PVdF), in the presence of phase transfer catalysts (PTCs) has been investigated. Rutherford backscattering spectrometry (RBS) has been used to determine the depth of modification achieved and to provide compositional depth profiles of modified PVdF samples. The complex chemical nature of the modified substrate, and the overlap of the elemental scattering edges within the depths involved (up to 1.4 m), create RBS spectra which are difficult to interpret. The DataFurnace software has been applied to the data, leading to excellent results. Defluorination and oxygenation of PVdF occurs on treatment with NaOH and PTC. Through the use of samples prepared with the aim of establishing the kinetics of the modification, a mechanism concerning elimination of fluorine followed by oxygenation, is shown to occur. The RBS analysis indicates that the kinetics of the defluorination reaction follows the Case 1 (Fickian) diffusion law, and that the depth of treatment is of the order of 1.4 m.     

Characterization of surface profiles of LPCVD silicon nitride films by RBS profile

Abstract

A Rutherford backscattering spectrometry (RBS)‐profile was applied to the characterization of the surface profile of silicon nitride films prepared by low pressure chemical vapor deposition (LPCVD). This method detected inhomogeneity in the silicon nitride films and demonstrated Si‐richness near the interface. This method was also used to study the silicon nitride profiles associated with bird's beak formation in VLSI devices. This paper presents a scheme for an auto‐search routine for an RBS‐profile program. The potential of the RBS‐profile method for the characterization of LPCVD silicon nitride films are demonstrated.     

Vibration of functionally graded carbon nanotube reinforced quadrilateral plates using geometric transformation discrete singular convolution method

Free vibration characteristics of thick skew plates reinforced by functionally graded carbon nanotubes (CNTs) reinforced composite are presented. Discrete singular convolution (DSC) method is used for the numerical solution of vibration problems via geometric mapping technique. Using the geometric transformation via a four-node element, the straight-sided quadrilateral physical domain is mapped into a square domain in the computational space. Then the method of discrete singular convolution with some singular kernels such as Regularized Shannon's delta (RSD) and Lagrange's delta kernels (LDK) have been used for spatial discretizing of the resulting governing equation of motion. Calculated results have been presented in order to show the effects of volume fraction of CNT, skew angles, CNT distribution types, plate aspect ratio and length-to-thickness ratio on the frequency of CNT reinforced skew plate. The current results are compared with the related results available in the literature and obtained by different methods. It is shown that reasonable accurate results are obtained for free vibration of nanocomposite plates with less computational effort for higher modes. Several test examples for different plate have been selected to demonstrate the convergence properties, accuracy, and simplicity in numerical implementation of DSC procedures. This approach has verified the accuracy and applicability of DSC method to the class of problem considered in this study. Furthermore, in the numerical examples in the scope of the study, the results obtained with DSC method using a coarser grid are more accurate than the values obtained by finite elements and differential quadrature (DQ) methods. It is also revealed that the method of discrete singular convolution is a promising and potential approach for computational mechanics of nonrectangular plates with nanocomposite reinforced.     

Limitation of Ti/TiN diffusion barrier layers in silicon technology

The usefulness of Ti/TiN and TiSi₂/TiN bilayers as low resistive contacts and diffusion barriers between doped silicon and aluminium has been examined. The Ti layer was magnetron sputtered and the TiN layers were deposited by reactive magnetron sputtering in an argon/nitrogen mixture. After Ti/TiN deposition part of the samples were annealed in a vacuum furnace to form a TiSi₂/TiN structure. The films were characterized by Rutherford backscattering spectrometry (RBS), X-ray diffractometry (XRD) and resistivity measurements. The integrity of the final metallization systems, with aluminium as top level, for annealing temperatures in the range 400–600°C was evaluated by RBS and electrical measurements on fully processed test vehicles containing structures for contact resistivity measurements and shallow implanted gated diodes. A significant discrepancy has been observed between recorded RBS data and electrical measurements. No reaction was detected by RBS at temperatures below 525°C although a significant degradation of the electrical performance was readily observed at lower annealing temperatures, e.g. an increase in contact resistance and large reverse leakage currents. It is concluded that RBS, commonly used in the study of diffusion barrier properties, gives optimistic information on the upper limit of the metallurgical stability of the barrier layers, whereas other factors such as step coverage, compositional variation and mechanical stress are of predominant significance when actual device metallization is concerned.     

Accurate determination of quantity of material in thin films by Rutherford backscattering spectrometry

Ion beam analysis (IBA) is a cluster of techniques including Rutherford and non-Rutherford backscattering spectrometry and particle-induced X-ray emission (PIXE). Recently, the ability to treat multiple IBA techniques (including PIXE) self-consistently has been demonstrated. The utility of IBA for accurately depth profiling thin films is critically reviewed. As an important example of IBA, three laboratories have independently measured a silicon sample implanted with a fluence of nominally 5 × 10(15) As/cm(2) at an unprecedented absolute accuracy. Using 1.5 MeV (4)He(+) Rutherford backscattering spectrometry (RBS), each lab has demonstrated a combined standard uncertainty around 1% (coverage factor k = 1) traceable to an Sb-implanted certified reference material through the silicon electronic stopping power. The uncertainty budget shows that this accuracy is dominated by the knowledge of the electronic stopping, but that special care must also be taken to accurately determine the electronic gain of the detection system and other parameters. This RBS method is quite general and can be used routinely to accurately validate ion implanter charge collection systems, to certify SIMS standards, and for other applications. The generality of application of such methods in IBA is emphasized: if RBS and PIXE data are analysed self-consistently then the resulting depth profile inherits the accuracy and depth resolution of RBS and the sensitivity and elemental discrimination of PIXE.     

An Analysis of the Heat Conduction Problem for Plates with the Functionally Graded Material Using the Hybrid Numerical Method

A heat conduction analysis of the functionally graded material (FGM) plates has been investigated based on the hybrid numerical method (HNM). HNM combines the layer element method with the method of Fourier transforms and proves to be efficient and reliable. The FGM plates are infinite large and the material properties vary continuously through thickness. The heat source continually acted one the FGM plates. The temperature distribution of the FGM plates is obtained in different time and different position. Some useful results for heat conduction problems are shown in figures. This article applies HNM to heat conduction firstly and provides us a new way for studying the heat conduction problems.     

Thermo elasticity solution of functionally graded,solid, circular,and annular plates integrated with piezoelectric layers using the differential quadrature method

Static analysis of functionally graded (FG) solid circular/annular plates imbedded in piezoelectric layers under thermo-electro mechanical load is investigated using the differential quadrature method. The plate has various edge boundary conditions and its material properties are assumed to vary in an exponential law with the Poisson ratio to be constant. The method is validated by comparing numerical results with the results obtained in the literature. The effects of the gradient index, thickness to radius ratio, and edges boundary conditions on the thermoelastic behavior of FG solid circular and annular plates are investigated.     

梁翼缘削弱型节点钢框架柱弹性稳定分析

采用变截面梁的转角位移方程,通过分析柱子的近端影响,推导出翼缘削弱型节点(RBS)无侧移和有侧移框架柱分别对应的计算长度系数?值的计算公式。通过引入梁柱修正线刚度比,RBS节点框架柱计算长度系数的计算公式可写成现行《钢结构设计规范》附录D的公式形式。研究结果表明:RBS节点无侧移框架柱的计算长度系数基本等同于普通刚接钢框架柱的计算长度系数,建议在简化计算中可直接按普通无侧移钢框架来计算;但对RBS节点有侧移钢框架,由于梁翼缘削弱,柱计算长度系数比普通刚接有侧移钢框架柱的计算长度系数有较大增加,已超过工程设计的允许误差,设计中应考虑其不利影响。     

Maximum stiffness design of laminated composite plates via a constrained global optimization approach

The optimal lamination arrangements of laminated composite plates with maximum stiffness subject to side constraints are investigated via a constrained multi-start global optimization approach. In the optimal design process, the deformation analysis of laminated composite plates is accomplished by utilizing a shear deformable laminated composite finite element and the optimal design problem, which has been converted into an unconstrained minimization problem via the general augmented Lagrangian method, is solved by utilizing the proposed unconstrained multi-start global optimization technique to determine the optimal fiber angles and layer group thicknesses of the laminated composite plates for attaining maximum stiffness and simultaneously satisfying the imposed side constraints. The feasibility of the proposed constrained multi-start global optimization algorithm is validated by means of a simple but representative example and its applications are demonstrated by means of a number of examples on the maximum stiffness design of symmetrically laminated composite plates. The effects of length-to-thickness ratio, aspect ratio, and number of layer groups upon the optimum fiber angles and layer group thicknesses of the plates are investigated.     

玻璃纤维复合材料板隔声性能的研究

选择树脂基玻璃纤维复合材料板,测量其辐射效率和损耗因子,研究纤维排布方式及纤维用量的影响,结果表明,纤维正交和单向铺设对玻璃纤维板辐射效率的影响基本相同,纤维的用量在10%~70%变化时,也没有明显的变化;对损耗因子的影响,在160~1000Hz范围内,单向玻纤复合材料板的阻尼比正交排布的低,而在2000~8000 Hz范围两者基本相同的。在中低频范围内,正交排布比单向排布对阻尼的影响更加显著。通过测试复合材料和金属铁的隔声量,在160~8000Hz范围内,玻璃纤维复合材料板没有出现隔声谷。提出纤维复合材料板中纵波波速公式,计算复合材料板的隔声量,与测量结果吻合良好。