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  • 1.
    Amouzgar, Kaveh
    et al.
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Bandaru, Sunith
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Andersson, Tobias J.
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Ng, Amos H. C.
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    A framework for simulation based multi-objective optimization and knowledge discovery of machining process2018Inngår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 98, nr 9-12, s. 2469-2486Artikkel i tidsskrift (Fagfellevurdert)
  • 2.
    Amouzgar, Kaveh
    et al.
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Bandaru, Sunith
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Andersson, Tobias J.
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Ng, Amos H. C.
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Metamodel based multi-objective optimization of a turning process by using finite element simulationArtikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study investigates the advantages and potentials of the metamodelbased multi-objective optimization (MOO) of a turning operation through the application of finite element simulations and evolutionary algorithms to a metal cutting process. The objectives are minimizing the interface temperature and tool wear depth obtained from FE simulations using DEFORM2D software, and maximizing the material removal rate. Tool geometry and process parameters are considered as the input variables. Seven metamodelling methods are employed and evaluated, based on accuracy and suitability. Radial basis functions with a priori bias and Kriging are chosen to model tool–chip interface temperature and tool wear depth, respectively. The non-dominated solutions are found using the strength Pareto evolutionary algorithm SPEA2 and compared with the non-dominated front obtained from pure simulation-based MOO. The metamodel-based MOO method is not only advantageous in terms of reducing the computational time by 70%, but is also able to discover 31 new non-dominated solutions over simulation-based MOO.

  • 3.
    Amouzgar, Kaveh
    et al.
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Bandaru, Sunith
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Andersson, Tobias
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Ng, Amos H. C.
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Metamodel based multi-objective optimization of a turning process by using finite element simulation2019Inngår i: Engineering optimization (Print), ISSN 0305-215X, E-ISSN 1029-0273Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study investigates the advantages and potentials of the metamodelbased multi-objective optimization (MOO) of a turning operation through the application of finite element simulations and evolutionary algorithms to a metal cutting process. The objectives are minimizing the interface temperature and tool wear depth obtained from FE simulations using DEFORM2D software, and maximizing the material removal rate. Tool geometry and process parameters are considered as the input variables. Seven metamodelling methods are employed and evaluated, based on accuracy and suitability. Radial basis functions with a priori bias and Kriging are chosen to model tool–chip interface temperature and tool wear depth, respectively. The non-dominated solutions are found using the strength Pareto evolutionary algorithm SPEA2 and compared with the non-dominated front obtained from pure simulation-based MOO. The metamodel-based MOO method is not only advantageous in terms of reducing the computational time by 70%, but is also able to discover 31 new non-dominated solutions over simulation-based MOO.

  • 4.
    Andersson, Tobias
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Mechanical Behaviour of Adhesive Layers: Methods to Extract Peel and Mixed Mode Properties2006Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Mechanical Behaviour of Adhesive Layers Methods to Extract Peel and Mixed Mode Properties TOBIAS ANDERSSON Department of Applied Mechanics Chalmers University of Technology ABSTRACT This thesis is concerned with methods to extract material properties of thin adhesive layers loaded in peel and in mixed mode. The first part of the thesis is devoted to an experimental method to determine the complete stress-elongation relation (or cohesive law) for an adhesive layer loaded in peel using the DCB-specimen. The method is based on the concept of equilibrium of the energetic forces acting on the specimen. Two sources of energetic forces are identified: the start of the adhesive layer and the positions of the two acting loads. By use of the concept of equilibrium of energetic forces, it is possible to measure the energy release rate of the adhesive layer instantaneously during an experiment. The complete stress-elongation relation is found to be the derivative of the energy release rate with respect to the elongation of the adhesive layer at its start. By this procedure, an effective property of the adhesive layer is measured. The validity of the approach is investigated by experiments where the adherends deform 1) elastically and 2) plastically. It is found that a unique stress-elongation is obtained when the adherends deform elastically. The same relation cannot be used to predict the experiments where the adherends deform plastically indicating that the approach has limited applicability. The second part of the thesis is concerned with the development of a mesomechanical finite element model of a thin adhesive layer loaded in mixed mode. 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 modelling and calibration. The purpose of the mesomechanical finite element model is to facilitate the development of constitutive laws for adhesive layers. The modelling 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 modelling of the entire process of degradation and fracture of the adhesive layer. A genetic algorithm is developed for the calibration. The simulations are shown to be in reasonably good agreement with the experiments. Keywords: adhesive layer, stress-elongation relation, J-integral, energetic force, experimental method, RVE, interface elements, genetic algorithm

  • 5.
    Andersson, Tobias
    et al.
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Biel, Anders
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Effects of the length of the damage zone on the effective constitutive properties of an adhesive layer loaded in peel2004Inngår i: The 15th European Conference on Fracture: ECF 15, 2004Konferansepaper (Annet vitenskapelig)
  • 6.
    Andersson, Tobias
    et al.
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Biel, Anders
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    On the effective constitutive properties of a thin adhesive layer loaded in peel2006Inngår i: International Journal of Fracture, ISSN 0376-9429, E-ISSN 1573-2673, Vol. 141, nr 1-2, s. 227-246Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An experimental method to determine the complete stress-elongation relation for a structural adhesive loaded in peel is presented. Experiments are performed on the double cantilever beam specimen, which facilitates a more stable experimental set-up as compared with conventional methods like the butt-joint test. The method is based on the concept of equilibrium of the energetic forces acting on the specimen. Two sources of energetic forces are identified: the start of the adhesive layer and the positions of the two acting loads. By use of the concept of equilibrium of energetic forces, it is possible to measure the energy release rate of the adhesive layer instantaneously during an experiment. The complete stress-elongation relation is found to be the derivative of the energy release rate with respect to the elongation of the adhesive layer at its start. By this procedure, an effective property of the adhesive layer is measured. That is, the fields are assumed to be constant through the thickness of the layer and only vary along the layer. To investigate the validity of this approach, experiments are performed on five different groups of specimens with different dimensions. This leads to large variations in the length of the damage zone at the start of the adhesive layer. Four of the experimental groups are used to determine the stress-elongation relation. This is found to be independent of the geometry. For the remaining experimental group, the adherends deform plastically and simulations are performed with the stress-elongation relation determined from the four elastic groups. It is found that the relation cannot be used to accurately predict the behaviour of the experiments where the adherends deform plastically. This indicates that the stress-elongation relation has limited applicability.

  • 7.
    Andersson, Tobias
    et al.
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Salomonsson, Kent
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Meso-mechanical modeling of thin adhesive layers2004Inngår i: The 15th European Conference on Fracture, 2004Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    A meso-mechanical finite element model for a thin adhesive layer is developed. The model is calibrated to experimental results where the adhesive layer is loaded in monotonically increasing peel or shear, cf. Andersson and Stigh [1] and Alfredsson et al. [2], and to an in situ SEM study of the fracture process. The purpose of the meso-mechanical finite element model is to facilitate the development of constitutive laws for adhesive layers.

    Ideas developed by Needleman [3], where structural continuum elements are bonded by cohesive elements are used as a basis for the finite element mesh. This thus enables micro cracks to propagate along the finite element boundaries.

    The simulations are found to be in good agreement with the experiments. The model is also capable of reproducing realistically the deformation observed in both peel [1] and shear [2] experiments.

  • 8.
    Andersson, Tobias
    et al.
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Salomonsson, Kent
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Simulation of crack initiation and propagation in an adhesive layer using a mesomechanical model: Polymer Composite Materials for Wind Power Turbines2006Inngår i: the 27th Risö International Symposium on Material Science, Riso National Laboratory , 2006, s. 315-320Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    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.

  • 9.
    Andersson, Tobias
    et al.
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap.
    Stigh, Ulf
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap.
    The stress-elongation relation for an adhesive layer loaded in peel using equilibrium of energetic forces2004Inngår i: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 41, nr 2, s. 413-434Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An experimental method to determine the stress–elongation relation for a thin adhesive layer loaded in peel is presented. The method is based on equilibrium of the energetic forces acting on a DCB-specimen. These energetic forces are identified to be associated with the geometrical positions of the acting loads and the start of the adhesive layer. The first energetic force is shown to be given by the product of the force and the rotation of the loading point. The second energetic force is shown to be given by the area under the stress–elongation curve for the adhesive layer. Using equilibrium of these energetic forces, the shape of the stress–elongation curve is determined. A test set-up is developed to facilitate the experiments. Special consideration is given to the accuracy of the measurement of the elongation of the adhesive. Results from two sets of experiments with slightly varying geometry are presented. The main result is that the stress–elongation relation can be described by a curve divided into three parts; initially the stress increases proportionally to the elongation. This corresponds to a linear elastic behaviour of the layer. The next part is given by a constant limiting stress. The curve ends with a parabolically softening part. After this point, a crack has been initiated in the adhesive. The experimental results are first compared to an asymptotic analysis using linear elastic fracture mechanics. This shows that the new method to evaluate the fracture energy gives consistent results. The experiments are also simulated using the measured stress–elongation law. Good agreement with the experiments is achieved which further validates the method. The fracture energy and the maximum peel stress are found to agree well within each set of experiments. Some variation is found between the two sets. This is accredited to differences in fracture initiation

  • 10.
    Salomonsson, Kent
    et al.
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Andersson, Tobias
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Modeling and parameter calibration of an adhesive layer at the meso level2008Inngår i: Mechanics of materials (Print), ISSN 0167-6636, E-ISSN 1872-7743, Vol. 40, nr 1-2, s. 48-65Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 11.
    Salomonsson, Kent E.
    et al.
    Högskolan i Skövde, Forskningscentrum för Virtuella system. Högskolan i Skövde, Institutionen för teknik och samhälle.
    Andersson, Tobias J.
    Högskolan i Skövde, Forskningscentrum för Virtuella system. Högskolan i Skövde, Institutionen för teknik och samhälle.
    Weighted Potential Methodology for Mixed Mode Cohesive Laws2010Inngår i: Proceedings of the MECOM DEL BICENTENARIO, IX Argentinian Congress on Computational Mechanics / [ed] Eduardo Dvorkin, Marcela Goldschmit, Mario Storti, Asociación Argentina de Mecánica Comptacional , 2010, s. 8355-8374Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A  weighted  potential  methodology  is  developed  by  utilizing  pure  mode  I  and mode  II  energy  release  rate  experiments  to  determine  the  traction-separation  relations  for thin  adhesive  layers.  The  experimentally  measured  energy  release  rates  act  as  boundary conditions  for  developing  a  weighted  potential  function.  Thus,  the  tractions  for  any  mixed mode loading can be established.  Changes of mode mix during an experiment can also be captured  by  the  law  since  every  mixed  mode  variation  is  given  by  the  potential  function. Furthermore,  by  use  of  an  inverse  J-integral  approach  and  damage  type  variables,  the traction-separation  relations  for  any  mode  mix  can  be  approximated  by  use  of  pure  mode experiments.  Numerical  simulations  show  the  applicability  of  the  methodology.  The  results indicate  that  the  methodology  is  promising  when  simulating  the  constitutive  behavior  of adhesive layers.

  • 12.
    Stigh, Ulf
    et al.
    Högskolan i Skövde, Forskningscentrum för Virtuella system. Högskolan i Skövde, Institutionen för teknik och samhälle.
    Alfredsson, Svante K.
    Högskolan i Skövde, Forskningscentrum för Virtuella system. Högskolan i Skövde, Institutionen för teknik och samhälle.
    Andersson, Tobias
    Högskolan i Skövde, Forskningscentrum för Virtuella system. Högskolan i Skövde, Institutionen för teknik och samhälle.
    Biel, Anders
    Högskolan i Skövde, Forskningscentrum för Virtuella system. Högskolan i Skövde, Institutionen för teknik och samhälle.
    Carlberger, Thomas
    Högskolan i Skövde, Forskningscentrum för Virtuella system. Högskolan i Skövde, Institutionen för teknik och samhälle.
    Salomonsson, Kent
    Högskolan i Skövde, Forskningscentrum för Virtuella system. Högskolan i Skövde, Institutionen för teknik och samhälle.
    Some aspects of cohesive models and modelling with special application to strength of adhesive layers2010Inngår i: International Journal of Fracture, ISSN 0376-9429, E-ISSN 1573-2673, Vol. 165, nr 2, s. 149-162Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An overview of recent development of cohesive modelling is given. Cohesive models are discussed in general and specifically for the modelling of adhesive layers. It is argued that most cohesive models model a material volume and not a surface. Detailed microscopic and mesomechanical studies of the fracture process of an engineering epoxy are discussed. These studies show how plasticity on the mesomechanical length scale contributes to the fracture energy in shear dominated load cases. Methods to measure cohesive laws are presented in a general setting. Conclusions and conjectures based on experimental and mesomechanical studies are presented. The influence of temperature and strain rate on the peak stress and fracture energy of cohesive laws indicates fundamentally different mechanisms responsible for these properties. Experiments and mesomechanical studies show that in-plane straining of an adhesive layer can give large contributions to the registered fracture energy. Finite element formulations including a method to incorporate this influence are discussed.

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