共查询到20条相似文献,搜索用时 31 毫秒
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An optoelectronic method is considered for noncontacting reconstruction of the surface profile of three-dimensional objects of large dimensions. The optimal conditions for performing measurements are identified. It is shown that the proposed method, in contrast to the already known methods, does not require fine tuning of the equipment. A numerical method is given for compensating distortions caused by aberrations. A method is described for reconstructing the surface profile cell by cell which increases the accuracy of measurements. 相似文献
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In this paper, a numerical method for computing the relaxation modulus of a linearly viscoelastic material is presented. The method is valid for relaxation tests where a constant strain rate is followed by a constant strain. The method is similar to the procedure suggested by Zapas and Phillips. Unlike Zapas-Phillips approach, this new method can be also applied for times shorter than t
1/2, where t
1 denotes time when the maximum strain is achieved. Therefore this method is very suitable for materials that experiences fast relaxation. The method is verified with numerical simulations. Results from the simulations are compared with analytical solution and Zapas-Phillips method. Results indicate that the presented approach is suitable for estimating the relaxation modulus. 相似文献
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Uri Kirsch Michal Kocvara Jochem Zowe 《International journal for numerical methods in engineering》2002,55(2):233-251
A preconditioned conjugate gradient (PCG) method that is most suitable for reanalysis of structures is developed. The method presented provides accurate results efficiently. It is easy to implement and can be used in a wide range of applications, including non‐linear analysis and eigenvalue problems. It is shown that the PCG method presented and the combined approximations (CA) method developed recently provide theoretically identical results. Consequently, available results from one method can be applied to the other method. Effective solution procedures developed for the CA method can be used for the PCG method, and various criteria and error bounds developed for conjugate gradient methods can be used for the CA method. Numerical examples show that the condition number of the selected preconditioned matrix is much smaller than the condition number of the original matrix. This property explains the fast convergence and accurate results achieved by the method. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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结构瞬态响应数值积分法的稳定性 总被引:4,自引:0,他引:4
本文借模态分析方法,导出了多自由度系统数值积分中的判稳方法,并以常用的尤拉后差法、纽马克法、呼伯特法为例,阐述了这一通用的数值稳定性分析方法,并得到了一些对选择恰当的差分格式有用的结论. 相似文献
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A numerical method for regenerators is introduced in this paper. It is not only suitable for the regenerators in cryocoolers and Stirling engines, but also suitable for the stacks in acoustic engines and the pulse tubes in pulse tube refrigerators. The numerical model is one dimensional periodic unsteady flow model. The numerical method is based on the control volume concept with the implicitly solve method. The iteration acceleration method, which considers the one-dimensional periodic unsteady problem as the steady two-dimensional problem, is used for decreasing the calculation time. By this method, the regenerator in an inertance tube pulse tube refrigerator was simulated. The result is useful for understanding how the inefficiency of the regenerator changes with the inertance effect. 相似文献
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M. G. Kaganer 《Journal of Engineering Physics and Thermophysics》1968,15(3):869-875
A solution is obtained for the problem of the heating of a two-layer plate at constant heating rate and for the problem of the monotonic heating of a single-layer plate with allowance for the temperature dependence of the thermophysical properties. The methods used include the integral heat balance method, the small parameter method, and Galerkin's method. The first problem is also solved by an operational method. 相似文献
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S. Ramadhyani S. V. Patankar 《International journal for numerical methods in engineering》1980,15(9):1395-1402
The two-dimensional Poisson equation is solved by the finite element method which uses rectangular elements and the bilinear shape function. Two kinds of weighting functions are employed, which correspond to the Galerkin method and the control-volume method. The results for three test problems, for which exact analytical solutions are available, show that the control-volume method leads to errors that are about one-half of the errors given by the Galerkin method. Incidentally, the five-point finite difference method is found to give errors which are nearly equal to those for the Galerkin method. 相似文献
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实验室常用静力称重法对微量液体容量进行检测,该方法在1μL容量的精确度达到2.18%,重复性为1.85%,但该方法无法在实验室外进行。现有的光学测量微量液体容量法的在1μL的精度为6.09%,重复性为1.31%。该法可实现在线检测,但其精度不如静力称重法。对光学测量微量液体容量的方法进行研究分析,提出了一种新的标定容量参照标准的方法,该标定方法将静力称重法与光学测量法两者结合,以静力称重法容量测量结果为参照标准,代替光学法原先的标准液。新的标定方法在原理上将参照标准由点扩展到线,可将光学测量法在10μL点的精度提高到2.014%,重复性1.30%。 相似文献
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Considering the misalignment of gear root circle and base circle and accurate transition curve, an improved mesh stiffness model for a healthy gear pair is proposed and validated by the finite element method (FEM). Based on the improved method, three mesh stiffness calculation methods (method 1: straight lines for crack path and limiting line; method 2: straight line for crack path and parabolic curve for limiting line proposed in Ref. [1]; method 3: parabolic curves for crack path and limiting line) for cracked gear pair are presented and compared with FEM. The results show that there is a significant difference between method 1 and FEM under large crack condition and the results of methods 2 and 3 are quite close to FEM result, which also shows that the parabolic curve as a limiting line is appropriate. Mesh stiffness of method 2 is very close to that of method 3, which also shows that it is acceptable to assume the crack path to be a straight line. 相似文献
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分别运用稳健统计(四分位和迭代)法、格拉布斯准则剔除离群值后用经典统计法对热轧带肋钢筋的6组数据进行了统计分析。结果表明:数据组中Z比分值大于5的数据,为离群值。数据组总体服从正态分布或接近正态分布的,3种统计方法结果基本吻合;不存在离群数据的情况下,建议采用稳健统计(四分位或迭代)法进行统计;存在离群数据的情况下,应采用格拉布斯准则剔除离群值后用经典统计法进行统计。对于数据明显偏离正态分布的,不存在离群数据的情况下,建议采用迭代稳健统计法进行统计;存在离群数据的情况下,应采用格拉布斯准则剔除离群值后用经典统计法进行统计。 相似文献
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《Composites Science and Technology》2003,63(13):1911-1920
Delamination of laminated composites is usually invisible or difficult to detect visually. Delamination causes low reliability for primary structures. Automatic systems for in-service delamination identifications are desired to improve low reliability. The present study employs an electric resistance change method for delamination detection. Since the method adopts reinforcement carbon fiber itself as sensors for delamination detection, this method does not reduce static or fatigue strength; also, the method is applicable to existing structures. Authors have found that the electric resistance change method with response surfaces is very effective experimentally and analytically. However, a large error of estimation remains for estimation of delamination location. In the present study, a new data processing procedure is proposed to improve performance of estimations of delamination location. The new method is applied to laminated composite beams. A delamination crack of a laminated composite beam is monitored with the new method using FEM analyses. As a result, the method reveals excellent performance of estimations of delamination location even for new data not used in regression equations. 相似文献
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《IEEE transactions on magnetics》2006,42(10):2279-2281
This paper describes a direct calculation method for medium fields in perpendicular recording systems. The method accounts for the effect of the zig-zag transition in the written medium pattern which can be obtained using micromagnetic simulations. The described method is useful for studying the cross-track characteristics of read sensors. The method is able to deal with a recording medium layer with nonunity relative permeability. The computed medium field in the gap region under the read head is compared with that obtained using the finite-element method. The purpose of this study is to develop a fast and effective tool for producing read-back signals based on computer modeling and simulation. 相似文献
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A simple method for computing the strain and the time dependent constants for non-linear viscoelastic materials is presented. The method is based on the finite time increment formulation of the convolution integral, and is applicable for materials which exhibit separable strain and time variables. The strain-dependent function can take any form including the hyperelastic potentials such as the Mooney-Rivlin strain energy function. The time-dependent function is based on the Prony series. The attraction of the method is that true material constants can be computed for any deformation history. 相似文献