Global/local methods research using a common structural analysis framework

Knight, Norman F.; Ransom, Jonathan B.; Griffin, O. Hayden; Thompson, Danniella M.

doi:10.1016/0168-874x(91)90053-2

Cited by 25 publications

(5 citation statements)

References 9 publications

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“…If not, the resulting incompatibility can be removed using the techniques, e.g. of References [56,57]. As customary, a topological transformation is adopted to uniform the computation of the integrals, that maps any element into a square element with corners e p J i , e q J i = ± 1.…”

Section: Finite Element Discretizationmentioning

confidence: 99%

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Layerwise mixed element with sublaminates approximation and 3D zig‐zag field, for analysis of local effects in laminated and sandwich composites

Icardi

2006

Numerical Meth Engineering

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SUMMARYThe analysis of damaged sandwich composites and thick laminates remains a still challenging task, owing to their intricate distributions of displacements and stresses across the thickness. The arduous task is capturing these distributions with an affordable computational effort. The use of sublaminate zig-zag models appears promising since they allow to group several physical layers into a sublaminate without violating the continuity of interlaminar stresses. To contribute to research in this field, a mixed, sublaminate element is developed in which displacements and stresses are approximated by two independent zig-zag models. Like for any zig-zag model, the interfacial contact conditions are fulfilled a priori suitably choosing the continuity functions and constants. In addition to the contact conditions on interlaminar shears, here those on the transverse normal stress and stress gradient are also fulfilled, as required by the elasticity theory. This uncustomary feature implies the presence of unwise terms which need C 2 continuous shape functions. To overcome this drawback, C 1 and C 2 terms are eliminated from the displacement field, as allowed by the mixed approach, then the interlaminar stresses obtained by the C 0 -made displacement model are cast into a separate zig-zag representation which restores their continuity at the interfaces. As nodal d.o.f. the three displacements and the three interlaminar stresses at the upper and lower faces are assumed, in order to fulfil the contact conditions assembling the sublaminates. Standard, C 0 , serendipity interpolation polynomials are used to represent both internal displacements and stress fields. As a consequence of this choice, the intra-element stress equilibria are fulfilled in an approximate integral form. This makes easier the development of the element, but does not compromise its accuracy and convergence rate, as shown by former applications. A postprocessing procedure is developed which improves the estimation of interlaminar stresses and helps to reduce the number of sublaminates. The result is that the analysis can be carried out using a single computational layer across the thickness and a reasonably fine in-plane discretization, even with distinctly different material properties of layers and in presence of damage. The overall computational time is reduced to an half of that required by a conventional sublaminate model, like present one deprived of zig-zag terms and postprocessing procedure.

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Section: Finite Element Discretizationmentioning

confidence: 99%

“…If not, the resulting incompatibility can be removed using the techniques, e.g. of References [56,57].…”

Section: Finite Element Discretizationmentioning

confidence: 99%

Layerwise mixed element with sublaminates approximation and 3D zig‐zag field, for analysis of local effects in laminated and sandwich composites

Icardi

2006

Numerical Meth Engineering

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“…The sub-models do not influence the operation of the system but get their boundary conditions and loading data from the larger simplified model. The sub-modeling approach is also referred to in the literature as the global/local approach (Knight et al, 1991). The sub-modeling approach can be used to connect dissimilar meshes together as shown schematically in Fig.…”

Section: Sub-modelingmentioning

confidence: 99%

Sub-modeling approach for obtaining structural stress histories during dynamic analysis

2013

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Abstract. Modern machine structures are often fabricated by welding. From a fatigue point of view, the structural details and especially, the welded details are the most prone to fatigue damage and failure. Design against fatigue requires information on the fatigue resistance of a structure's critical details and the stress loads that act on each detail. Even though, dynamic simulation of flexible bodies is already current method for analyzing structures, obtaining the stress history of a structural detail during dynamic simulation is a challenging task; especially when the detail has a complex geometry. In particular, analyzing the stress history of every structural detail within a single finite element model can be overwhelming since the amount of nodal degrees of freedom needed in the model may require an impractical amount of computational effort. The purpose of computer simulation is to reduce amount of prototypes and speed up the product development process. Also, to take operator influence into account, real time models, i.e. simplified and computationally efficient models are required. This in turn, requires stress computation to be efficient if it will be performed during dynamic simulation. The research looks back at the theoretical background of multibody simulation and finite element method to find suitable parts to form a new approach for efficient stress calculation. This study proposes that, the problem of stress calculation during dynamic simulation can be greatly simplified by using a combination of Floating Frame of Reference Formulation with modal superposition and a sub-modeling approach. In practice, the proposed approach can be used to efficiently generate the relevant fatigue assessment stress history for a structural detail during or after dynamic simulation. Proposed approach is demonstrated in practice using one numerical example. Even though, examples are simplified the results show that approach is applicable and can be used as proposed.

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“…The resulting mesh is inadequate for evaluating the stress intensity factors using the displacement technique, however. Therefore, the submodelling technique [47,48] is used, in which the displacements from this mesh are imposed on an independent focused mesh which represents the crack tip using quarter-point elements (as shown in Figure 2(a)). The displacement field of this focused mesh is then used to estimate the stress intensity factor.…”

Section: Representation Of the Crack Advancementmentioning

confidence: 99%

A review of fatigue crack propagation modelling techniques using FEM and XFEM

Rege

Lemu

2017

IOP Conf. Ser.: Mater. Sci. Eng.

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The study of the dissipation heat flow and the acoustic emission during the fatigue crack propagation in the metal A N Vshivkov, A Yu Iziumova, I A Panteleev et al. noAbstract. Fatigue is one of the main causes of failures in mechanical and structural systems. Offshore installations, in particular, are susceptible to fatigue failure due to their exposure to the combination of wind loads, wave loads and currents. In order to assess the safety of the components of these installations, the expected lifetime of the component needs to be estimated. The fatigue life is the sum of the number of loading cycles required for a fatigue crack to initiate, and the number of cycles required for the crack to propagate before sudden fracture occurs. Since analytical determination of the fatigue crack propagation life in real geometries is rarely viable, crack propagation problems are normally solved using some computational method. In this review the use of the finite element method (FEM) and the extended finite element method (XFEM) to model fatigue crack propagation is discussed. The basic techniques are presented, together with some of the recent developments. IntroductionComponents which are subjected to fluctuating loads are found virtually everywhere: Vehicles and other machinery contain rotating axles and gears, pressure vessels and piping may be subjected to pressure fluctuations (e.g. water hammer) or repeated temperature changes, structural members in bridges are subjected to traffic loads and wind loads, while those in ships and offshore structures are subjected to the combination of wind loads, wave loads and currents. If the components are subjected to a fluctuating load of a certain magnitude for a sufficient amount of time, small cracks will nucleate in the material. Over time, the cracks will propagate, up to the point where the remaining cross-section of the component is not able to carry the load, at which the component will be subjected to sudden fracture [1]. This process is called fatigue, and is one of the main causes of failures in structural and mechanical components [2]. In order to assess the safety of the component, engineers need to estimate its expected lifetime. The fatigue life is the sum of the number of loading cycles required for a fatigue crack to nucleate/initiate, and the number of cycles required for the crack to propagate until its critical size has been reached [2,3]. In this paper, computational methods to estimate the lifespan of a propagating crack whose initial geometry is known will be considered.Estimations of the fatigue crack propagation rate, da/dN, are normally based on a relation with the range of the stress intensity factor, ΔK, which is a linear elastic fracture mechanics (LEFM) parameter for quantifying the load and geometry of the crack. Paris, Gomez and Anderson [4] first proposed the existence of such a relation in 1961, and its simplest form is the Paris law [5]:

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Global/local methods research using a common structural analysis framework

Cited by 25 publications

References 9 publications

Layerwise mixed element with sublaminates approximation and 3D zig‐zag field, for analysis of local effects in laminated and sandwich composites

Layerwise mixed element with sublaminates approximation and 3D zig‐zag field, for analysis of local effects in laminated and sandwich composites

Sub-modeling approach for obtaining structural stress histories during dynamic analysis

A review of fatigue crack propagation modelling techniques using FEM and XFEM

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