Assessment of the Cohesive Contact method for the analysis of thin-walled bonded structures (original) (raw)
Related papers
Experimental and numerical investigations on adhesively bonded joints
IOP conference series, 2016
Two types of adhesively bonded joints were experimental and numerical investigated. Firstly, the adhesives were characterized through a set of tests and the main elastic and mechanical properties were obtained. After that, the stress distributions at interface and middle of adhesive layer were determined using a linear elastic FEA. The numerical data were fitted by a power law in order to determine the critical values of intensity of stress singularity.
Standard finite element techniques for efficient stress analysis of adhesive joints
International Journal of Adhesion and Adhesives, 2009
The paper documents ongoing research in the field of stress analysis of adhesive bonded joints and aims at developing efficient and accurate finite element techniques for the simplified calculation of adhesive stresses. Goal of the research is to avoid the major limitations of existing methods, in particular their dependency on special elements or procedures not supported by general purpose analysis packages. Two simplified computational methods, relying on standard modelling tools and regular finite elements are explored and compared with the outcome of theoretical solutions retrieved from the literature and with the results of full, computationally intensive, finite element analyses. Both methods reproduce the adherends by means of structural elements (beams or plates) and the adhesive by a single layer of solid elements (plane-stress or bricks). The difference between the two methods resides in the thickness and in the elastic properties given to the adhesive layer. In one case, the adhesive thickness is extended up to the midplane of the adherends and its elastic modulus is proportionally increased. In the other case, the adhesive layer is maintained at its true properties and the connection to the adherends is enforced by standard kinematic constraints. The benchmark analyses start from 2D single lap joints and are then extended to 3D configurations, including a wall-bonded square bracket undergoing cantilever loading. One of the two simplified methods investigated provides accurate results with minimal computational effort for both 2D and 3D configurations.
Influence of the Cohesive Law Parameters on the Strength Prediction of Adhesively-Bonded Joints
Materials Science Forum, 2012
Adhesive joints are largely employed nowadays as a fast and effective joining process. The respective techniques for strength prediction have also improved over the years. Cohesive Zone Models (CZM's) coupled to Finite Element Method (FEM) analyses surpass the limitations of stress and fracture criteria and allow modelling damage. CZM's require the energy release rates in tension (G n ) and shear (G s ) and respective fracture energies in tension (G n c ) and shear (G s c ). Additionally, the cohesive strengths (t n 0 for tension and t s 0 for shear) must also be defined. In this work, the influence of the CZM parameters of a triangular CZM used to model a thin adhesive layer is studied, to estimate their effect on the predictions. Some conclusions were drawn for the accuracy of the simulation results by variations of each one of these parameters.
Analytical models of adhesively bonded joints—Part I: Literature survey
International Journal of Adhesion and Adhesives, 2009
The literature survey presented in Part I describes the major analytical models for adhesively bonded joints, especially for single lap joints. By consulting the summary table given in Part I, the designer can choose from a wide range of models which is the best for a particular situation. However, the information given in the summary table is not sufficient for a proper selection. The designer also needs to know the time required for setting up an analysis and solving it. Another important factor is the accuracy of strength prediction. Therefore, models of increasing complexity were selected from the summary table and a comparative study was made in terms of time requirements and failure prediction for various cases. Three main situations were considered: elastic adherends and adhesive, elastic adherends with nonlinear adhesive, and nonlinear analyses for both adherends and adhesive. The adherends were both isotropic (metals) and anisotropic (composites). The effects of the overlap length and the adhesive thickness were also considered.
Structures built from several components require some means of joining. In this context, bonding with adhesives has several advantages compared to traditional joining methods, e.g. reduction of stress concentrations, reduced weight penalty and easy manufacturing. Adhesives can be strong and brittle (e.g., Araldite ® AV138) or less strong and ductile (e.g., Araldite ® 2015). A new family of polyurethane adhesives combines high strength and ductility (e.g., Sikaforce ® 7888). In this work, the performance of the three above mentioned adhesives was tested in single-lap joints with varying values of overlap length (L O). The experimental work carried out is accompanied by a detailed numerical analysis by Finite Elements, based on Cohesive Zone Models (CZM). This procedure enabled detailing the performance of this predictive technique applied to bonded joints. Moreover, it was possible to evaluate which family of adhesives is more suited for each joint geometry. CZM revealed to be highly accurate, except for largely ductile adhesives, although this could be circumvented with a different cohesive law.
Efficient Post-elastic Analysis of Bonded Joints by Standard Finite Element Techniques
Journal of Adhesion Science and Technology, 2009
A simplified finite element approach based on reduced models with minimum degrees of freedom was applied to the post-elastic analysis of bonded joints. The reduced model describes the adherends by means of structural elements (beams or shells) and the adhesive by a single strip of solid elements (plane-stress or brick). Internal kinematic constraints were applied to link the adherends and adhesive meshes. The accuracy and the efficiency of the reduced models in providing the force–displacement curve of T-peel joints were evaluated through a numerical test campaign by comparison with full finite element analyses. The test campaign was designed as a 2-level factorial experiment involving four variables: the skew angle of the T-peel (45 and 90°), the thickness of the adherends (2 and 3 mm), the material of the adherends (aluminium and steel) and the stress–strain behaviour of the adhesive (brittle and perfectly plastic). The results show that the reduced model reproduces with fair accuracy the load–displacement curves of the joints at a fraction of the computational cost of the full model. The elastic stiffness, the yield load and the deformation energy were predicted within an error of 7%, 15% and 36%, respectively, with processing times that were typically 50 times shorter than the full model.
Procedia Engineering, 2015
Structures built from several components require some means of joining. In this context, bonding with adhesives has several advantages compared to traditional joining methods, e.g. reduction of stress concentrations, reduced weight penalty and easy manufacturing. Adhesives can be strong and brittle (e.g., Araldite ® AV138) or less strong and ductile (e.g., Araldite ® 2015). A new family of polyurethane adhesives combines high strength and ductility (e.g., Sikaforce ® 7888). In this work, the performance of the three above mentioned adhesives was tested in single-lap joints with varying values of overlap length (L O). The experimental work carried out is accompanied by a detailed numerical analysis by Finite Elements, based on Cohesive Zone Models (CZM). This procedure enabled detailing the performance of this predictive technique applied to bonded joints. Moreover, it was possible to evaluate which family of adhesives is more suited for each joint geometry. CZM revealed to be highly accurate, except for largely ductile adhesives, although this could be circumvented with a different cohesive law.
Numerical and experimental analysis of bonded joints with combined loading
International Journal of Adhesion and Adhesives, 2019
The metallic materials bonding using structural adhesives has become an increasingly used process, presenting advantages when compared to other fastening methods such as screws and rivets. The aim of this paper is the numerical evaluation of bonded joints with combined loading (traction and shear) using the finite element method, comparing the results obtained with the experiments performed at the same configurations. Considering adhesive joints with the same bonded area, but with different linear dimensions, the mechanical strength may be different, which characterizes the shape factor. In this way, the analyzes considered the bonded area shape factor in nine different configurations, being modified both the height and the width of the joint, considering two points of force application for each group. For the numerical simulation, the cohesive zone models (CZM) were used, which use the concepts of linear elastic fracture mechanics (LEFM). These models consider that one or multiple interfaces or regions of fracture may be artificially introduced into the structures, which is done through the separation-traction laws. For this purpose, DCB (double cantilever beam) and ENF (end notched flexure) tests were performed, measuring this way the essential cohesive properties to the numerical modeling, especially the critical energy release in I and II modes (normal and shear, respectively). The influence of some cohesive properties on the maximum load of the bonded joint was investigated. 2 The good numerical and experimental concordance in different configurations studied confirms that the CZM provide consistent results with the bonded joint experiments for the presented conditions of adhesive thickness, surface treatment and load application point, not only in single lap joints, but also in combined loading joints, whose investigation was done in this work.
Strength assessment of adhesive-bonded joints
Computational Materials Science, 2008
This paper deals with non-linear analyses of adhesively bonded joints under tensile lap shear loading. 3D FEM models are taken into account. The effect of the number of elements through the adhesive layer thickness is considered. Tensile true stress-true strain curves are used as models of the adherend and adhesive materials. The single lap joints are tested to validated the numerical analyses.