Olsson R.,Swerea SICOMP AB |
Juntikka R.,Swerea SICOMP AB |
Juntikka R.,FS Dynamics Sweden AB |
Asp L.E.,Swerea SICOMP AB
Solid Mechanics and its Applications | Year: 2013
Hail impact on composite structures during flight occurs at high velocities and is a serious concern as it may cause matrix cracking, large internal delaminations, and eventually fibre fracture not visible on the impacted surface. The present paper gives an introduction to hail impact on composite laminates and an overviewof experiments andmodellingwork on this topic, performed during several years at Swerea SICOMP. Ice balls of different sizes and velocities have been shot with an air gun on composite laminates of different thickness and reinforcement architecture. High speed photography and measurement of strain and deflection histories of the laminates have been used to validate the models developed. Models involve dynamic explicit finite element (FE) simulations with cohesive elements to allow for delamination in the laminate, and simplified but fast analytical models. The experimental response has also been compared with predictions from the FE model and the analytical models using various material models of the ice. FE models using a calibrated elastic-plastic ice model are capable of accurately predicting the response and delamination initiation, while the current analytical models are unable to simulate the initial part of the impact. A main conclusion is that delamination occurs at a very early stage of the impact (first 10-50 μs) where three-dimensional wave propagation and the initial elastic-plastic behaviour of the ice are important. Closed form models are capable of predicting the peak contact stresses at the first instance of contact, but further work is required to allow simulation of the decay of contact stresses observed in the FE simulations. © Springer Science+Business Media Dordrecht 2013.
Svensson D.,University of Skovde |
Alfredsson K.S.,University of Skovde |
Stigh U.,University of Skovde |
Jansson N.E.,GKN plc |
Jansson N.E.,FS Dynamics Sweden AB
Engineering Fracture Mechanics | Year: 2016
Kink-band formation is an important mechanism limiting the compressive strength of high strength composites. A cohesive zone model is used to model the material in a unidirectional carbon fibre composite that forms the kink-band. Equilibrium of configurational forces is used to design and evaluate the experiments. Microscopic studies show that a kink-band is formed with the height of about 200μm. The corresponding cohesive law has a peak stress of about 1.5GPa, a compression at failure of about 50μm and a fracture energy of about 25kJ/m2. © 2015 Elsevier Ltd.
Gardhagen R.,Linkoping University |
Lantz J.,Linkoping University |
Carlsson F.,FS Dynamics Sweden AB |
Karlsson M.,Linkoping University
WSEAS Transactions on Biology and Biomedicine | Year: 2011
Turbulent flow in the cardiovascular system may increase the risk for severe arterial disease. This work addresses the feasibility of Large Eddy Simulation (LES) using a general purpose code as a tool for assessment of cardiovascular flow and investigates Wall Shear Stress (WSS) in steady as well as pulsating turbulent pipe flow. Poiseuille flow was specified at the inlet, and with a suitable ammount of perturbations at the inlet it was possible to predict experimental data. The extent of the recirculation zone was affected by the inlet disturbances, and magnitude as well as direction of the WSS vector varied significantly at the reattachment point. For the pulsating flow, WSS shows a complex pattern with different spatial and temporal variation along the pipe. The wall shear stress gradient was calculated on the entire post-stenotic surface and each component in the gradient was investigated. The off-diagonal components in the gradient are usually assumed to be small, but here they were found to be on the same order of magnitude as the diagonal terms. This work demonstrates the need for a scale resolving simulation technique to accurately model cardiovascular flows.
Eller D.,KTH Royal Institute of Technology |
Tomac M.,FS Dynamics Sweden AB
CAD Computer Aided Design | Year: 2016
An open-source implementation of an efficient mesh generation procedure for hybrid prismatic-tetrahedral meshes intended for use in Reynolds-averaged Navier-Stokes solutions is presented. The method employed combines the established, and very fast, Delaunay-based tetrahedral mesh generator TetGen with a novel technique for the creation of a prismatic layer, where constrained global optimization of the envelope is employed. Once a well-shaped envelope is thus obtained, a semi-structured layer of pentahedral elements is extruded between wall and envelope surface. Satisfactory mesh quality is demonstrated by comparing solutions obtained using the new meshes with reference data computed on high-quality advancing-front grids. Mesh generation time is shown to be substantially smaller than with many other methods. Overall, the presented implementation is deemed a valuable tool for cases where many meshes need to be generated for routine analyses and turnaround time is critical. This is an extended version of the paper presented at the 23rd International Meshing Roundtable in London, October 2014. © 2015 Elsevier Ltd.