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  • 1
    Electronic Resource
    Electronic Resource
    Self-Similar Crack Expansion method for the stress intensity factor analysis (1996)
    Springer
    Acta mechanica solida Sinica 9 (1996), S. 104-123 
    Details
    ISSN: 0894-9166
    Keywords: self-similar crack expansion ; stress intensity factor ; crack extension method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The Self-Similar Crack Expansion(SSCE) method is proposed to evaluate stress intensity factors at crack tips, whereby stress intensity factors of a crack can be determined by the crack opening displacement over the crack, not just by the local displacement around the crack tip. The crack expansion rate is estimated by taking advantage of the crack self-similarity. Therefore, the accuracy of the calculation is improved. The singular integrals on crack tip elements are also analyzed and are precisely evaluated in terms of a special integral analysis. Combination of these two techniques greatly increases the accuracy in estimating the stress distribution around the crack tip. A variety of two-dimensional cracks, such as subsurface cracks, edge cracks, and their interactions are calculated in terms of the self-similar expansion rate. Solutions are satisfied with errors less than 0. 5% as compared with the analytical solutions. Based on the calculations of the crack interactions, a theory for crack interactions is proposed such that for a group of aligned cracks the summation of the square of SIFs at the right tips of cracks is always equal to that at the left tips of cracks. This theory was proved by the mehtod of Self-Similar Crack Expansion in this paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02209156
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A Self-Similar Crack Expansion method for three-dimensional cracks in an infinite or semi-infinite medium (1996)
    Springer
    Acta mechanica solida Sinica 9 (1996), S. 217-235 
    Details
    ISSN: 0894-9166
    Keywords: self-similar crack expansion ; stress intensity ; crack extension method ; 3-D cracks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The Self-Similar Crack Expansion (SSCE) method is used to calculate stress intensity factors for three-dimensional cracks in an infinite medium or semi-infinite medium by the boundary integral element technique, whereby, the stress intensity factors at crack tips are determined by calculating the crack-opening displacements over the crack surface. For elements on the crack surface, regular integrals and singular integrals are precisely evaluated based on closed form expressions, which improves the accuracy. Examples show that this method yields very accurate results for stress intensity factors of penny-shaped cracks and elliptical cracks in the full space, with errors of less than 1% as compared with analytical solutions. The stress intensity factors of subsurface cracks are in good agreement with other analytical solutions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02208305
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Element-free Galerkin method for contact problems in metal forming analysis (2001)
    Bradford : Emerald
    Engineering computations 18 (2001), S. 62-78 
    Details
    ISSN: 0264-4401
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Technology
    Notes: The total Lagrangian formulation and implementation of the element-free Galerkin method (EFG) is presented for the analysis of contact-impact problems with large deformations and for the simulation of metal forming processes. An integration scheme based on stress points is used, so no mesh is needed. A simple but general contact searching algorithm is used to treat the contact interface and an algorithm for the contact force is presented. Numerical results for Taylor bar impact are compared to finite element solutions and agree well. Solutions to upsetting, extrusion of metals with large material distortions are given to show the effectiveness of the algorithm. In particular, EFG is shown to be more capable of treating motions of the workpiece around corners of the punch than finite element methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/02644400110365806
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  • 4
    Electronic Resource
    Electronic Resource
    Numerical integration of the Galerkin weak form in meshfree methods (1999)
    Springer
    Computational mechanics 23 (1999), S. 219-230 
    Details
    ISSN: 1432-0924
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The numerical integration of Galerkin weak forms for meshfree methods is investigated and some improvements are presented. The character of the shape functions in meshfree methods is reviewed and compared to those used in the Finite Element Method (FEM). Emphasis is placed on the relationship between the supports of the shape functions and the subdomains used to integrate the discrete equations. The construction of quadrature cells without regard to the local supports of the shape functions is shown to result in the possibility of considerable integration error. Numerical studies using the meshfree Element Free Galerkin (EFG) method illustrate the effect of these errors on solutions to elliptic problems. A construct for integration cells which reduces quadrature error is presented. The observations and conclusions apply to all Galerkin methods which use meshfree approximations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004660050403
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  • 5
    Electronic Resource
    Electronic Resource
    An assembled surface normal algorithm for interior node removal in three-dimensional finite element meshes (1985)
    Springer
    Engineering with computers 1 (1985), S. 55-60 
    Details
    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract An algorithm is developed for identifying interior nodes and edges in finite element meshes of three-dimensional solids. The algorithm is extremely simple and quite fast. The interior nodes are identified by assembling the normals to all surfaces of the model according to the usual finite element assembly procedure. Comparison with a sort-search algorithm shows a tenfold reduction in running time; running time is a linear function of the number of nodes or elements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01200339
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  • 6
    Electronic Resource
    Electronic Resource
    An expert system for setting time steps in dynamic finite element programs (1989)
    Springer
    Engineering with computers 5 (1989), S. 205-219 
    Details
    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract An expert system, ETUDES—Expert Time integration control Using Deep and Surface Knowledge System, which addresses the determination of the timestep for time integration of linear structural dynamic equations is described. This time-step may also be applicable for a moderately nonlinear simulation of the same structure. The program also determines whether an explicit or implicit method is most efficient for the particular simulation. A production rule programming system written in OPS5 is used for the implementation of this prototype expert system. Issues relating to the expert system architecture for this application, such as knowledge representation and structure, as well as domain knowledge are discussed. The prototype is evaluated by measuring it's performance in various benchmark model problems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02274213
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    A stochastic damage model for the rupture prediction of a multi-phase solid (1992)
    Springer
    International journal of fracture 55 (1992), S. 341-361 
    Details
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The stochastic damage model, which has been proposed in Part I of this paper, is utilized to analyze quantitatively the effects of uncertainties in locations, orientations and numbers of microcracks at the macro-tip. This is accomplished by introducing a computer simulation model which incorporates a statistical characterization of geometrical parameters of a random microcrack array. The counteracting effects of microcracking on the fracture toughness, namely, toughness enhancement and toughness degradation, are explored statistically through the change of the location and size of the near tip damage zone. The effects of changes in the geometric configuration and density of microcracks at the macro-tip are also examined through the present statistical approach. The validity of the present model is verified by comparing the obtained statistical distribution with the analytic model based on the Neville distribution function. A very good fit achieved by the use of the Neville function demonstrates the potential of the present damage model, in predicting the inherent statistical distribution of the fracture toughness from the intrinsic random microdefects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00035190
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  • 8
    Electronic Resource
    Electronic Resource
    A stochastic damage model for the rupture prediction of a multi-phase solid (1992)
    Springer
    International journal of fracture 55 (1992), S. 321-340 
    Details
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this paper, a stochastic damage model is proposed for the rupture prediction of a brittle, multi-phase material. The model, based on the macrocrack-microcrack interaction, characterizes damage by microcracking and fracture by macrocracking. The model incorporates uncertainties in locations, orientations and numbers of microcracks. Owing to the high concentration of microcracks within the frontal damage zone near the macro-tip, a higher order analysis based on traction boundary integral equations is formulated for an arbitrary array of cracks. The change of the stress intensity at the macrocrack tip by the configuration of microcracks is investigated through a parametric study. The presence of large fluctuation in the stress intensity at the macro-tip justifies the use of the statistical approach, which will be presented in a companion paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00035189
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    A stabilization procedure for the quadrilateral plate element with one-point quadrature (1983)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 19 (1983), S. 405-419 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A stabilization procedure is developed for controlling the kinematic modes of the four-node, bilinear quadrilateral element when single-point quadrature is used. These kinematic modes manifest themselves by spatial oscillations or singularity of the total stiffness. In this stabilization procedure, additional generalized strains are defined which are activated by the kinematic modes; these generalized modes are furthermore not activated by rigid body motions regardless of the shape of the quadrilateral. By using a scaling law developed in an earlier paper, the stabilization parameters are defined so they do not adversely affect the element's performance. Several problems which are subject to kinematic modes are presented to illustrate the performance of this stabilization procedure for linear problems.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620190308
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  • 10
    Electronic Resource
    Electronic Resource
    Improvements in 3-node triangular shell elements (1986)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 23 (1986), S. 1643-1667 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Low-order triangular finite shell elements are computationally economical and easy to implement, but often exhibit very slow convergence. Two new membrane formulations for triangular shell elements are examined which rectify these drawbacks. The first element is based on the Marguerre shallow shell theory and a strain projection method that eliminates spurious membrane strain energy. Resulting expressions are provided in an explicit form for easy implementation of the element. The second element is based on a linear membrane field governed by normal rotations and reduced quadrature.The difficulties with shell-normal rotations are analysed and a method for omitting these rotations while preserving rigid body motion is presented and tested. Finally, a set of test problems are examined which show the importance of mesh patterns and degrees-of-freedom per node on triangular element performance.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620230906
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