| 1. |
- Borg, Rikard, et al.
(författare)
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Modeling of delamination using a discretized cohesive zone and damage formulation
- 2002
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Ingår i: Composites Science And Technology. - 0266-3538 .- 1879-1050. ; 62:10-11, s. 1299-1314
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Tidskriftsartikel (refereegranskat)abstract
- Delamination initiation and growth are analyzed by using a discrete cohesive crack model. The delamination is constrained to grow along a tied interface. The model is derived by postulating the existence of a maximum load surface which limits the adhesive forces in the process zone of the crack. The size of this maximum load surface is made dependent on the amount of dissipated crack opening work, such that the maximum load surface shrinks to zero as a predefined amount of work is consumed. A damage formulation is used to reduce the adhesive forces. Mode I, II and III loading or any combined loading is possible. An analytical solution is obtained for a single mode opening and the implications of this result on the governing equations is discussed. The delamination model is implemented in the finite element code LS-DYNA and simulation results are shown to be in agreement with experimental results. © 2002 Elsevier Science Ltd. All rights reserved.
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| 2. |
- Borg, Rikard, 1962-, et al.
(författare)
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Simulating DCB, ENF and MMB experiments using shell elements and a cohesive zone model
- 2004
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Ingår i: Composites Science And Technology. - 0266-3538 .- 1879-1050. ; 64:2, s. 269-278
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Tidskriftsartikel (refereegranskat)abstract
- A delamination model for shell elements is presented. It consists of an adhesive penalty contact formulation for initially tying shells together and a cohesive zone model for degrading the adhesive forces. An adhesive contact used between shell elements has to account for the thickness offset, such that the rotational degrees of freedom in the shell elements are included in the algorithm. This is considered in the present contact model and the complete delamination model is implemented in the explicit Finite Element code LS-DYNA. By preventing delamination growth the delamination model can be turned into a tied contact. As such it is used in two FE-models, where plates are bonded together and subjected to various loads. The adhesive penalty contact performs well. The complete delamination is validated by simulating the Double Cantilever Beam, End-Notch Flexural and Mixed Mode Bending setups, and the results are shown to be in agreement with experimental data.
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| 3. |
- Borg, Rikard, 1962-, et al.
(författare)
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Simulation of delamination in fiber composites with a discrete cohesive failure model
- 2001
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Ingår i: Composites Science And Technology. - 0266-3538 .- 1879-1050. ; 61:5
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Annan publikation (populärvet., debatt m.m.)abstract
- Delamination initiation and growth are analyzed by using a discrete cohesive crack model. The model is derived by postulating the existence of a maximum load surface which limits the adhesive forces in the process zone of the crack. The size of the maximum load surface is made dependent on the amount of dissipated crack opening work such that the maximum load surface shrinks to zero as a predefined amount of work is consumed. Mode I, II, III loading or any combined loading is possible. The delamination model is implemented in the explicit finite-element code LS-DYNA and simulation results are found to be in agreement with experimental results. ⌐ 2001 Elsevier Science Ltd. All rights reserved.
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| 4. |
- Borg, Rikard, 1962-, et al.
(författare)
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Simulation of low velocity impact on fiber laminates using a cohesive zone based delamination model
- 2004
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Ingår i: Composites Science And Technology. - 0266-3538 .- 1879-1050. ; 64:2, s. 279-288
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Tidskriftsartikel (refereegranskat)abstract
- An existing delamination model is further developed for use in transverse impact simulations. An algorithm is developed making it possible to determine the propagation direction of the delamination front. Using this it is possible to determine relative orientation of the delamination front with respect to the fibers above and below the interface. In a qualitative evaluation it is shown that the present delamination model can be used for modeling delamination initiation and growth in transverse impact simulations.
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| 5. |
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| 6. |
- Jansson, Tomas, et al.
(författare)
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Using surrogate models and response surfaces in structural optimization : with application to crashworthiness design and sheet metal forming
- 2003
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Ingår i: Structural and multidisciplinary optimization (Print). - : Springer Science and Business Media LLC. - 1615-147X .- 1615-1488. ; 25:2, s. 129-140
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this paper is to determine if the Space Mapping technique using surrogate models together with response surfaces is useful in the optimization of crashworthiness and sheet metal forming. In addition, the efficiency of optimization using Space Mapping will be compared to traditional structural optimization using the Response Surface Methodology (RSM). Five examples are used to study the algorithm: one optimization of an analytic function and four structural optimization problems. All examples are constrained optimization problems. In all examples, the algorithm converged to an improved design with all constraints fulfilled, even when a conventional RSM optimization failed to converge. For the crashworthiness design problems, the total computing time for convergence was reduced by 53% using Space Mapping compared to conventional RSM. For the sheet metal forming problems the total computing time was reduced by 63%. The conclusions are that optimization using Space Mapping and surrogate models can be used for optimization in crashworthiness design and sheet metal forming applications with a significant reduction in computing time.
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| 7. |
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| 8. |
- lI, M. X.D., et al.
(författare)
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Two-mesh refinement indicators and adaptivity in non-linear explicit finite element analysis of shells using LS-DYNA
- 2000
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Ingår i: International Journal for Numerical Methods in Engineering. - 0029-5981 .- 1097-0207. ; 16:11, s. 785-800
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Tidskriftsartikel (refereegranskat)abstract
- Two-mesh refinement indicators based on the gradients of effective stresses and effective plastic strains, respectively, are proposed for adaptive finite element analysis of the large deformation, materially non-linear dynamic response of shells. The refinement strategy consists of equi-distributing the variation of stresses or plastic strains over the elements of the mesh. A program module for implementing these refinement indicators has been developed and coupled with the general non-linear finite element explicit code LS-DYNA. Numerical examples including both material and geometric non-linearities are presented. It is shown that these indicators can effectively identify those finite elements, which have high gradients of stresses and strains so that the mesh is refined in the region's undergoing the most severe deformations.
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| 9. |
- Marklund, Per-Olof, et al.
(författare)
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Optimization of a car body component subjected to side impact
- 2001
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Ingår i: Structural and multidisciplinary optimization (Print). - : Springer Science and Business Media LLC. - 1615-147X .- 1615-1488. ; 21:5, s. 383-392
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Tidskriftsartikel (refereegranskat)abstract
- This paper explores structural optimization methods applied to a car side impact. The use of local and global approximation methods has been compared, resulting in a recommendation that global approximation methods should be used for this kind of transient loading problems. The numerical simulations have been carried out using the explicit finite element program LS-DYNA. The problem studied is the weight minimization of the B-pillar, situated between the front and the rear door of the car, without compromising the safety of the car occupants. All results are related to the original B-pillar in the SAAB 95 car. By using global approximations in the form of linear and quadratic response surfaces it is shown that the weight of the B-pillar can be reduced by 25% without the loss of safety.
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| 10. |
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