| 3011. |
- Högberg, Dan, 1965-
(författare)
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Use of finite element method in trailer deck design
- 2001
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Ingår i: Journal of Materials Processing Technology. - : Elsevier. - 0924-0136 .- 1873-4774. ; 117:1-2, s. 238-243
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Tidskriftsartikel (refereegranskat)abstract
- The employment of the finite element (FE) method in conceptual and detail design of a secondary deck platform for trailer bodies is presented. The main objective of the project is to design a versatile, light and cheap secondary deck. To assist the designer with sufficient means for the concept generation and evaluation process, the FE method is used in order to gain fair structural analysis data. Assistance from the computer software stimulates creativity, reduces the time required in the design process, and eventually increases probability to gain customer satisfaction. This approach is precise enough for comparison purposes at this stage of the design process. The structural data gained is compared mainly with weight and access criteria.
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| 3012. |
- Högberg, J. Li, et al.
(författare)
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Constitutive behaviour of mixed mode loaded adhesive layer
- 2007
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Ingår i: International Journal of Solids and Structures. - : Elsevier. - 0020-7683 .- 1879-2146. ; 44:25-26, s. 8335-8354
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Tidskriftsartikel (refereegranskat)abstract
- Mixed mode testing of adhesive layer is performed with the Mixed mode double Cantilever Beam specimen. During the experiments, the specimens are loaded by transversal and/or shear forces; seven different mode mixities are tested. The J-integral is used to evaluate the energy dissipation in the failure process zone. The constitutive behaviour of the adhesive layer is obtained by a so called inverse method and fitting an existing mixed mode cohesive model, which uses a coupled formulation to describe a mode dependent constitutive behaviour. The cohesive parameters are determined by optimizing the parameters of the cohesive model to the experimental data. A comparison is made with the results of two fitting procedures. It is concluded that the constitutive properties are coupled, i.e. the peel and shear stress depend on both the peel and shear deformations. Moreover, the experiments show that the critical deformation in the peel direction is virtually independent of the mode mixity.
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| 3013. |
- Högberg, J. Li
(författare)
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Mixed mode cohesive law
- 2006
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Ingår i: International Journal of Fracture. - : Springer Netherlands. - 0376-9429 .- 1573-2673. ; 141:3-4, s. 549-559
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Tidskriftsartikel (refereegranskat)abstract
- A traction-separation relation to model the fracture process is presented. The cohesive law captures the linear elastic and softening behaviour prior to fracture. 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 limitation of a common fracture energy in peel and shear. Examples are given in form of FE- implementations of the normalised cohesive law, namely for the Unsymmetrical Double Cantilever Beam (UDCB) specimen and the Mixed-mode double Cantilever Beam (MCB) specimen. Both specimens are adhesively bonded and loaded in mixed-mode
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| 3014. |
- Högberg, Jia Li
(författare)
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Mixed mode loaded adhesive layers : from measurement of material data to analysis of structural behaviour
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In manufacturing of multi-material products, a joining method that is able to cost-effectively assemble components made of dissimilar and similar material, with irregular geometries, is optimal. As an alternative, adhesive bonding is in-creasingly adapted by the industry, which is also used in manufacturing of multi-phase materials. In practice, adhesives are constrained to thin layers. An adhesive as a constrained layer behaves differently compared to the adhesive as a bulk material. In general, adhesive layers are loaded in peel (mode I), or in shear (mode II or III), or in a combination of peel and shear (mixed mode). This thesis deals with mixed mode loaded adhesive layers, from measurement of ma-terial data to analysis of structural behaviour. For studying of structural behaviour of adhesive joints, an integrated approach is developed. Arbitrarily end-loaded single-layer adhesive joints with arbitrary ad-herends of arbitrary length are analysed with the Beam/Adhesive layer (B/A) model. Closed-form solutions are obtained for the adhesive layer as well as for the adherends. For joints with a semi-infinite symmetric geometry, i.e. relative long joints with identical adherends loaded at one end, basic loading cases are obtained. Solutions to these basic loading cases are easy to use in designing of joints with this type of geometry. For nonlinear or general adhesive layers, a mode-dependent cohesive law is de-veloped. The normalized formulation is easy to implement in numerical simula-tions, yet, it captures the characteristics of adhesive layers. For experimental studies, this cohesive law is used to obtain the constitutive behaviour of an adhe-sive layer. The results confirm the ability and suitability of this cohesive law in modelling of adhesive layers. To obtain material data of adhesive layers, experimental methods are developed based on the J-integral. Two specimens, the Mixed mode double Cantilever Beams (MCB) specimen and the Unbalanced Double Cantilever Beams (UDCB) specimen, are designed to allow adhesive layers to be loaded in mixed mode. The MCB-specimen is implemented experimentally and the constitutive behav-iour of the tested adhesive layer is obtained.
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| 3015. |
- Högberg, J. Li
(författare)
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Mixed mode testing of adhesive layer : Polymer Composite Materials for Wind Power Turbines
- 2006
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Ingår i: Proceedings of the 27th Risø International Symposium on Materials Science. - Roskilde : Risø National Laboratory. - 8755035280 ; , s. 183-190
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Konferensbidrag (refereegranskat)abstract
- For a flexible linear adhesive, the mode mixety of a single-layer adhesive joint is directly related to the deformation of the adhesive layer at the crack tip. The governing equations for linear elastic singe-layer adhesive joints show that the mode mixety depends on the exteranl loads, the properties of the adherends and often on the flexibility of the adhesive layer. This implies some fundemantal problems that has to be adressed before an experimental method can be established. Requirements for the design of a specimen configuration for a mixed mode testing of adhesive layers are given. A new specimen configuration is proposed and some preliminary experimental results are given.
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| 3016. |
- Högberg, J. Li, et al.
(författare)
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Simulation of an adhesive layer using a novel mixed mode cohesive law
- 2006
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Ingår i: CDCM 2006 - Conference on Damage in Composite Materials 2006 18th-19th of September 2006 in Stuttgart, Germany.
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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.
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| 3017. |
- Högberg, J. Li, et al.
(författare)
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Specimen proposals for mixed mode testing of adhesive layer
- 2006
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Ingår i: Engineering Fracture Mechanics. - : Elsevier. - 0013-7944 .- 1873-7315. ; 73:16, s. 2541-2556
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Tidskriftsartikel (refereegranskat)abstract
- The experimental methods to determine the fracture properties for adhesives under mixed mode loading is not as well established as compared to such methods for adhesives under pure mode loading. Some controversies exist regarding the decomposition of the mode mixity. For a flexible linear elastic adhesive, the mode mixity of a single-layer adhesive joint is directly related to the deformation of the adhesive layer at the crack tip. The governing equations for linear elastic single-layer adhesive joints show that the mode mixity depends on the external loads, the properties of the adherends and often on the flexibility of the adhesive layer. This implies some fundamental problems that have to be addressed before an experimental method can be established. The purpose of this paper is to investigate different specimen configurations for mixed mode loading. Requirements for the design of a specimen configuration are given. A new specimen configuration is proposed based on the geometry of a semi-infinite symmetric DCB-specimen. According to this study, the proposed test specimen offers exceptional flexibility, variety and stability.
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| 3018. |
- Högberg, Jia Li
(författare)
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Unbalanced UCB-specimen
- 2006
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Ingår i: CDCM 2006 - Conference on Damage in Composite Materials 2006 18th-19th of September 2006 in Stuttgart, Germany.
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Konferensbidrag (refereegranskat)abstract
- The Double Cantilever Beam (DCB) specimen is a common test geometry for testing of mode I fracture properties of adhesive joints. However, when unbalances are introduced to the adherends, the adhesive layer is loaded in a combination of peel (mode I) and shear (mode II). In this work the unbalanced DCB-specimen is studied by the use of the beam/adhesive layer (B/A) model, in which the adherends are considered as beams and the adhesive layer as a generalised spring media. The effect of the thickness of adhesive layer together with the effect of the geometrical and material unbalances is analysed. The result of the B/A model is compared to the continuum model through FE-simulations. Finally, an unsymmetric DCB-specimen is dimensioned for mixed mode testing of adhesive layer.
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| 3019. |
- Högberg, Li
(författare)
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Mechanical Behaviour of Single-Layer Adhesive Joints : an integrated approach
- 2004
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Innovative products that are competitive on the market are likely to employ newtypes of materials and unusual geometries. A method that can assemble dissimilarmaterials and irregular geometries cost-effectively and at the same time offera joint that is light in weight and imperceptible, is optimal. Conventional joiningmethods, such as welding and riveting, can no longer satisfy the joining purposecompletely. Adhesive joints satisfy all mentioned requirements above and henceoffer design engineers a wider choice of materials and an increased freedom ingeometry design of the components, which most likely leads to a better design ina shorter time. The prediction of the mechanical behaviour of a joint, preferablywith simple and efficient formulas, plays an important role in the product designprocess. In this thesis, single-layer adhesive joints are analysed through the integratedapproach, i.e. an extensive stress analysis followed by a fracture analysisto determine the energy release rate and the mode-mixity due to general endloads. The purpose is to provide easy-to-use design formulas and to investigatedifferent specimen configurations for the experimental determination of the mechanicalproperties of adhesives under mixed mode loading.In the stress analysis, a systematic and easy to use closed-form solution based onthe beam/adhesive layer (B/A) model is presented to determine the stress andstrain in a linear elastic single-layer adhesive joint. In the fracture analysis, fourtypes of single-layer adhesive joints are investigated based on the closed-formsolution given in the stress analysis. The B/A model is compared to two continuummodels: one neglecting the existence of the adhesive layer (Suo and Hutchinson1990) and the other accounting the adhesive layer by the use of FEM.The results of the B/A model compares favourably to the FE-analyses. Threetypes of basic loading systems are identified for the symmetric semi-infinitejoint geometry. Two specimens for testing mode mixity are suggested. Accordingto the theoretical studies by use of the B/A model, the specimen denoted theMixed Mode B with a short crack length offers good flexibility, variety and stability.
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| 3020. |
- Höglund, Jarl, et al.
(författare)
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Up-Stream and Down-Stream Quality in Enterprise Modeling Practice : Supporting Model Driven Continuous Improvement in Organizations
- 2012
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Ingår i: The Practice of Enterprise Modeling. - Berlin, Heidelberg : Springer. - 9783642345487 - 9783642345494 ; , s. 148-159
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Konferensbidrag (refereegranskat)abstract
- The paper identifies and discusses what is considered to be the three most critical points, both up-stream and down-stream to Enterprise Modeling, for ensuring the usefulness and use of EM results in the continuous improvement of organizations. The model type that is targeted in the cases discussed in the paper is the process model, but other related model types, e.g. goal models and concepts models are also addressed in relation to process models. The points addressed in the paper are: 1) Trigger handling - acting on symptoms or the root cause problem, 2) critical aspects during modeling, and 3) establishing mechanisms for continuous model based business process improvement.
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