| 1. |
- Högberg, J. Li, et al.
(författare)
-
Simulation of an adhesive layer using a novel mixed mode cohesive law
- 2006
-
Ingår i: CDCM 2006 - Conference on Damage in Composite Materials 2006 18th-19th of September 2006 in Stuttgart, Germany.
-
Konferensbidrag (refereegranskat)abstract
- The purpose of this work is to develop a flexible cohesive law to simulate the constitutive behaviour of an adhesive layer under mixed mode loading. A mixed mode cohesive law that captures the linear elastic and softening behaviour before fracture is presented. This simple model uses a coupled formulation to describe the mixed mode cohesive behaviour. It also allows for different fracture parameters, such as fracture energy, strength and critical separation in different mode mixities. Thus, the fracture process in mode I (peel), in mode II (shear) or in mixed mode (a combination of peel and shear) can be modelled without the usual constraint of a common fracture energy in peel and shear. Examples are given of FE-implementation of the normalised cohesive law, namely for the Unsymmetric Double Cantilever Beam (UDCB) specimen and the Mixed-mode double Cantilever Beam (MCB) specimen. Both specimens are adhesively bonded and loaded in mixed-mode.
|
|
| 2. |
- Pesämaa, Ossi, et al.
(författare)
-
Attitudes to change in Gnosjöregion
- 2009
-
Ingår i: Presented at The international Symposium on Entrepreneurship in Tourism, Rovaniemi, Finland, March 17-21, 2009.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This study promotes ideas into two main academic areas, that is attitudes towards change processes and regional development. The implications of the study are written to tourism in the Gnosjöregion and other countryside areas. We specifically ask what attitudes towards change processes in development projects in tourism generate commitments to tourism and to what extent these effects are moderated by perceived involvement. Our objective is to develop more knowledge to the area of attitudes within project management. The results of the study engender from a pre-study from 59 responses of a survey distributed during spring 2008 in the Gnosjöregion. Our major implication is that future study may consider freedom rather than interest towards working in change processes and that these effects are also moderated when individuals perceive an enhanced involvement. Our study is a first attempt to develop these two areas and results should therefore be read and interpreted with the same carefulness as any pre-study is prepared and conducted.
|
|
| 3. |
- Salomonsson, Kent, et al.
(författare)
-
An adhesive interphase element for structural analyses
- 2008
-
Ingår i: International Journal for Numerical Methods in Engineering. - : Wiley. - 0029-5981 .- 1097-0207. ; 76:4, s. 482-500
-
Tidskriftsartikel (refereegranskat)abstract
- A special purpose finite element is developed for structural simulations of complex adhesively bonded structures. In the interphase element, the adhesive is explicitly regarded as a material phase between two substrates. The element considers large rotations. Furthermore. it considers in-plane straining of the adhesive due to large curvatures of the bonded shells. This feature appears especially important when considering bonding of thin plastically deforming metallic shell structures. Simulations are made on specimens where the adherends deform both elastically and plastically. The results are in good agreement with previously performed experiments. Copyright (0 2008 John Wiley & Sons, Ltd.
|
|
| 4. |
- Salomonsson, Kent, et al.
(författare)
-
Influence of root curvature on the fracture energy of adhesive layers
- 2009
-
Ingår i: Engineering Fracture Mechanics. - : Elsevier. - 0013-7944 .- 1873-7315. ; 76:13, s. 2025-2038
-
Tidskriftsartikel (refereegranskat)abstract
- Previously performed experiments to study the mode I behavior of an adhesive layer revealed an apparent increase in the fracture toughness when the adherends deformed plastically. Attempts to simulate the experiments are made; both with elastically and plastically deforming adherends. Thus, effects of the size of the process zone and the deformation of the adherends are revealed. The adhesive layer is modeled using finite elements with different approaches; cohesive elements and representative volume elements. The adherends are modeled with solid elements. With a long process zone, all models give good results as compared to the experiments. However, only the model with representative volume elements gives good agreement for large root curvatures and correspondingly short process zones. The results are interpreted by analyzing the deformation and mechanisms of crack propagation in the representative volume elements. It is shown that with large root curvature of the adherends, the in-plane stretching of the adhesive layer gives a substantial contribution to the fracture energy. A simple formula is derived and shown to give an accurate prediction of the effects of the root curvature. This result indicates the limits of conventional cohesive zone modeling of an adhesive layer of finite thickness.
|
|
| 5. |
- Salomonsson, Kent
(författare)
-
Meso-Mechanical Modeling and Analysis of Adhesive Layers
- 2007
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is concerned with the modeling, simulation and analysis of adhesive layers. By use of an in situ scanning electron microscopy study it is found that the adhesive studied in the present thesis has a very complex structure with two different compounds, a mineral and an epoxy/thermoplastic blend. A representative volume element (RVE) model is developed to study the behavior of the adhesive layer at the meso-level. It is a continuum model where interface finite elements are implemented at the boundaries of the continuum elements in order to enable crack initiation and propagation of micro cracks. On a structural level, two deformation modes, modes I and II, dominate the behavior of thin adhesive layers. With the RVE it is possible reproduce experimental stress-deformation relations from both modes. However, in a real structure, mixed mode loading usually occur. A range of mode mixes is studied, using the RVE, from an un-loaded state until fracture of the layer. The results indicate that the behavior of the interface elements dominate for mode mixes close to mode I and plasticity in the continuum elements dominates for mode II dominated mode mixes. Furthermore, effects of large root curvatures of the adherends is analyzed numerically by simulating plastically deforming double cantilever beam specimens using the finite element model. The developed RVE is implemented in the models to simulate the behavior of the adhesive layer. By this methodology, virtual experiments can be analyzed with extreme detail. It is shown that in-plane straining of the adhesive layer significantly influences the strength of adhesive joints at large plastic strain of the adherends. There is a never ending need in industries to minimize computational time. To this end, an interphase finite element for structural analyses is developed. The element considers in-plane straining of the adhesive layer due to large curvatures of surrounding substrates.
|
|
| 6. |
- Salomonsson, Kent
(författare)
-
Meso-Mechanical Modeling of Thin Adhesive Layers
- 2005
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A thin adhesive layer is analyzed using a representative volume element (RVE). The RVE is comprised by, both continuum and interfacial finite elements. The interface elements allow for crack initiation and crack propagation. To obtain realistic results from the RVE simulation, an in situ scanning electron microscopy (SEM) study is performed. Results from the SEM study show that the adhesive has a very complex structure with two different compounds, a mineral and an epoxy/thermoplastic blend.The RVE is subjected to two different load cases, peel and shear. An evolutionary algorithm is used to calibrate the numerical model to experimental results. The simulation results are compared to experimental results to verify the numerical model. The simulations show good agreement with the experimental results for both the peel and shear experiments.
|
|
| 7. |
|
|
| 8. |
- Salomonsson, Kent
(författare)
-
Mixed mode modeling of a thin adhesive layer using a meso-mechanical model
- 2008
-
Ingår i: Mechanics of materials. - : Elsevier. - 0167-6636 .- 1872-7743. ; 40:8, s. 665-672
-
Tidskriftsartikel (refereegranskat)abstract
- A representative volume element is modeled using the finite element method. It is used to analyze mixed mode behavior of a thin adhesive layer. Two sources of dissipation is modeled; plasticity and decohesion. Macroscopic traction–separation laws are extracted from the simulations. The results indicate that a boundary of mode mix exists between a region where major plastic dissipation is present and a region where it is not. Without major plastic dissipation, the fracture energy is low and essentially governed by the cohesive properties. This is the case in peel dominated loading cases. In shear dominated loading cases plastic dissipation gives a substantial contribution to the fracture energy. The results show that pure shear loading gives the largest fracture energy.
|
|
| 9. |
- Salomonsson, Kent, et al.
(författare)
-
Modeling and parameter calibration of an adhesive layer at the meso level
- 2008
-
Ingår i: Mechanics of materials. - : Elsevier ltd.. - 0167-6636 .- 1872-7743. ; 40:1-2, s. 48-65
-
Tidskriftsartikel (refereegranskat)abstract
- A mesomechanical finite element model of a thin adhesive layer is developed. The model is calibrated to previously performed experiments. In these, the adhesive layer is loaded in monotonically increasing peel or shear. An in situ SEM study is also performed and used to guide the modeling and calibration. The purpose of the mesomechanical finite element model is to facilitate the development of constitutive laws for adhesive layers. The modeling is based on Xu and Needleman’s method where all continuum finite elements are surrounded by interface elements that allow for the development of micro cracks. Thus, this enables the modeling of the entire process of degradation and fracture of the adhesive layer. A genetic algorithm is developed for the calibration. The simulations show good agreement with the experiments.
|
|
| 10. |
- Salomonsson, Kent, et al.
(författare)
-
On the apparent influence of the adherends on the fracture toughness of adhesive layers
- 2007
-
Ingår i: Interface design of polymer matrix composites. - 9788755036260
-
Konferensbidrag (refereegranskat)abstract
- A detailed model of experiments with the double cantilever beam specimen is set up. Analysis of the model shows that an experimentally deduced apparent increase of fracture energy with severely deforming adherends is due to contributions of in-plane straining of the adhesive layer to the fracture energy. An analysis with the J-integral confirms the result.
|
|
| 11. |
- Salomonsson, Kent, et al.
(författare)
-
Simulation of crack initiation and propagation in an adhesive layer using a meso-mechanical model
- 2006
-
Ingår i: Proc. of 27th Risø International Symposium on Materials Science, Polymer Composite Materials for Wind Power Turbines.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A finite element model of a double cantilever beam specimen is developed. The adherends are modeled using plane strain elastic continuum elements. Furthermore, the adhesive is modeled using a mesomechanical modeling technique which allows for simulation of initiation and propagation of micro-cracks. This enables the modeling of the entire process of degradation and fracture of the adhesive layer. The purpose of the present study is to compare the stress-deformation behavior in an idealized peel loading to the behavior in a double cantilever beam (DCB) specimen where the adhesive layer is deformed wilt a slight gradient along the layer. Previously performed experiments and simulations of the RVE are used as a comparison to the simulated results.
|
|
| 12. |
- Salomonsson, Kent, et al.
(författare)
-
Simulation of crack initiation and propagation in an adhesive layer using a mesomechanical model : Polymer Composite Materials for Wind Power Turbines
- 2006
-
Ingår i: Polymer composite materials for wind power turbines. Proceedings. - Roskilde : Risø National Laboratory. - 8755035280 ; , s. 315-320
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A finite element modle of a double cantilever beam specimen is developed. The adherents are modeled using plane strain elastic continuum elements. Furthermore, the adhesive is modeled using a mesomechanical modeling teqnique wich allows for simulation of initiation and prognationb of micro-cracks. This enables the modelling of entire process of degradation and fracture of the adhesive layer. The purpose of the present study is to compare the stress-deformation behavior in an idealized peel loading to the behavior in a double cantilever beam (DCB) specimen where the adhesive layer is deformed wilt a slight gradient along the layer. Previously performed experiments and simulations of the RVE are used as a compariosn to the simulated results.
|
|
