Jun‐Sik Kim  Maenghyo Cho 《International journal for numerical methods in engineering》2002,55(11):1323-1343

A finite element based on the efficient higher‐order zig‐zag theory with multiple delaminations is developed. The bending part of the formulation is constructed from the concept of DKQ element. Unlike conventional elements, a developed element has its reference in the bottom surface which simplifies zig‐zag terms on formulation. Exact patch solutions are developed on elements which have the bottom reference system. The present element passes proper bending patch tests in the arbitrary mesh configurations in isotropic materials. Zig‐zag formulation is adopted to model laminated plates with multiple delaminations. To assess the accuracy and efficiency of the present element based on higher‐order zig‐zag theory with multiple delaminations, the linear buckling problem of laminated plates with multiple delaminations has been analysed. The results have been compared with three‐dimensional elasticity solutions. The present element works as an efficient tool for analysing the behaviour of the laminated composites with multiple delaminations. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

    

Zhi‐Wei Wang 《Packaging Technology and Science》2001,14(4):149-157

By applying the method suggested in the author's previous paper, shock spectra and damage boundary curves are investigated for a hyperbolic tangent cushioning system under the action of rectangular, half‐sine, terminal‐peak saw‐tooth and initial‐peak saw‐tooth acceleration pulses, respectively. The shock spectrum is affected not only by the damping parameter but also by the dimensionless pulse peak, and both the damping parameter and the dimensionless fragility influence the damage boundary curve for this cushioning system. Some important features of a hyperbolic tangent cushioning system that differs from a tangent cushioning system are discussed in detail. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

    

Jos&#x;Luis Toca‐Herrera  Rumen Krastev  Vera Bosio  Seta Küpcü  Dietmar Pum  Andreas Fery  Margit Sra  Uwe&#x;B. Sleytr 《Small (Weinheim an der Bergstrasse, Germany)》2005,1(3):261-261

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Sang‐Ho Lee  Jeong‐Hoon Song  Young‐Cheol Yoon  Goangseup Zi  Ted Belytschko 《International journal for numerical methods in engineering》2004,59(8):1119-1136

A combination of the extended finite element method (XFEM) and the mesh superposition method (s‐version FEM) for modelling of stationary and growing cracks is presented. The near‐tip field is modelled by superimposed quarter point elements on an overlaid mesh and the rest of the discontinuity is implicitly described by a step function on partition of unity. The two displacement fields are matched through a transition region. The method can robustly deal with stationary crack and crack growth. It simplifies the numerical integration of the weak form in the Galerkin method as compared to the s‐version FEM. Numerical experiments are provided to demonstrate the effectiveness and robustness of the proposed method. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

  总被引：1，自引：0，他引：1  

N. Sukumar  Z. Y. Huang  J.‐H. Prvost  Z. Suo 《International journal for numerical methods in engineering》2004,59(8):1075-1102

Partition of unity enrichment techniques are developed for bimaterial interface cracks. A discontinuous function and the two‐dimensional near‐tip asymptotic displacement functions are added to the finite element approximation using the framework of partition of unity. This enables the domain to be modelled by finite elements without explicitly meshing the crack surfaces. The crack‐tip enrichment functions are chosen as those that span the asymptotic displacement fields for an interfacial crack. The concept of partition of unity facilitates the incorporation of the oscillatory nature of the singularity within a conforming finite element approximation. The mixed‐mode (complex) stress intensity factors for bimaterial interfacial cracks are numerically evaluated using the domain form of the interaction integral. Good agreement between the numerical results and the reference solutions for benchmark interfacial crack problems is realized. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

    

Nam‐II Kim  Hee‐Taek Yun  Moon‐Young Kim 《International journal for numerical methods in engineering》2004,61(2):274-302

An evaluation procedure of exact static stiffness matrices for curved beams with non‐symmetric thin‐walled cross section are rigorously presented for the static analysis. Higher‐order differential equations for a uniform curved beam element are first transformed into a set of the first‐order simultaneous ordinary differential equations by introducing 14 displacement parameters where displacement modes corresponding to zero eigenvalues are suitably taken into account. This numerical technique is then accomplished via a generalized linear eigenvalue problem with non‐symmetric matrices. Next, the displacement functions of displacement parameters are exactly calculated by determining general solutions of simultaneous non‐homogeneous differential equations. Finally an exact stiffness matrix is evaluated using force–deformation relationships. In order to demonstrate the validity and effectiveness of this method, displacements and normal stresses of cantilever thin‐walled curved beams subjected to tip loads are evaluated and compared with those by thin‐walled curved beam elements as well as shell elements. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

    

Z. S. Abo‐Hammour  M. Yusuf  N. M. Mirza  S. M. Mirza  M. Arif  J. Khurshid 《International journal for numerical methods in engineering》2004,61(8):1219-1242

Second‐order, two‐point boundary‐value problems are encountered in many engineering applications including the study of beam deflections, heat flow, and various dynamic systems. Two classical numerical techniques are widely used in the engineering community for the solution of such problems; the shooting method and finite difference method. These methods are suited for linear problems. However, when solving the non‐linear problems, these methods require some major modifications that include the use of some root‐finding technique. Furthermore, they require the use of other basic numerical techniques in order to obtain the solution. In this paper, the author introduces a novel method based on continuous genetic algorithms for numerically approximating a solution to this problem. The new method has the following characteristics; first, it does not require any modification while switching from the linear to the non‐linear case; as a result, it is of versatile nature. Second, this approach does not resort to more advanced mathematical tools and is thus easily accepted in the engineering application field. Third, the proposed methodology has an implicit parallel nature which points to its implementation on parallel machines. However, being a variant of the finite difference scheme with truncation error of the order O(h²), the method provides solutions with moderate accuracy. Numerical examples presented in the paper illustrate the applicability and generality of the proposed method. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

    

Charbel Farhat  Radek Tezaur  Paul Weidemann‐Goiran 《International journal for numerical methods in engineering》2004,61(11):1938-1956

Recently, a discontinuous Galerkin method with plane wave basis functions and Lagrange multiplier degrees of freedom was proposed for the efficient solution of Helmholtz problems in the mid‐frequency regime. In this paper, this method is extended to higher‐order elements. Performance results obtained for various two‐dimensional problems highlight the advantages of these elements over classical higher‐order Galerkin elements such as Q₂ and Q₄ for the discretization of interior and exterior Helmholtz problems. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

    

Dan Koppel  Yuan‐Fang Wang  Hua Lee 《International journal of imaging systems and technology》2004,14(5):181-185

Video endoscopy, a modality of minimally invasive surgery, has proven to be significantly less invasive to the patient. However, by relying on a video interface to observe the surgical scene, several nonintuitive effects need to be contended with. One of these is the reduction or removal of the discrepancy in view position and orientation between the surgeon and the endoscope. Eliminating artifacts in the visual feedback is important for the improvement of the effectiveness of the surgical procedures. This article presents a novel rendering technique to produce the scene from a “surgeon‐centric” viewpoint to create greater transparency for optimizing the visual precision of the endoscopic procedures. © 2005 Wiley Periodicals, Inc. Int J Imaging Syst Technol 14, 181–185, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.20022  相似文献   

    

Shih‐Yu Huang 《International journal of imaging systems and technology》2004,14(6):246-252

Taking into consideration computational complexity and design regularity, this article proposes a content‐aware full search (CAFS) block matching scheme for motion estimation. Full search (FS) is widely employed in hardware design of block matching because of its regular data flow. But the huge computational complexity of FS makes it infeasible especially in low‐power environments. To reduce the required computational complexity, CAFS using a content‐aware computation allocation mechanism dynamically distributes computation to blocks with distinct motion content based on center‐biased distribution characteristics of motion vectors. Because all operations of CAFS can be performed by a series of ±2 FSs, the hardware of CAFS can be easily extended by the design of FS. Experimental results indicates that CAFS can achieve about 0.5–1.4 dB quality improvement over original FS in football and table tennis sequences under the same computation. © 2005 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 14, 246–252, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.20028  相似文献