1,721,376 research outputs found
Compressive failure and kink-band formation modeling
Full text linkTo increase the use of polymeric structural composites, a major issue is to properly account for intra-laminar failure mechanisms, such as fiber kinking induced under compression. We propose a new continuum damage model that can predict the fiber kinking response at the ply level. The model is based on a previous structure tensor-based model for the response of UD-plies. A novel feature is that the compressive UD-ply response at the macroscale includes the effect of the fiber misalignment shaped as a kink-band that is resolved at the sub-scale. Concepts of computational homogenization are used to include the fiber-shear of the kink-band at the sub-scale. The model calibration is adapted to account for either kink-band formation or shear-splitting depending on the off-axis loading. Finally, the model is validated at the laminate level against experimental data for OHC-tests available in the literature. A good agreement is found for predicted strength values and observed fracture patterns of the laminates. The size effect experienced when different hole sizes are tested is also addressed
Damage analysis of spot replacement sleepers interspersed in ballasted railway tracks
Full text linkThe interspersed pattern sleeper, a spot replacement of old timber sleeper with concrete or composite counterparts, of railway track is often used as a temporary maintenance for secondary railway lines such as yards, balloon loops or siding. However, their negative effect on the railway has not been taken into account. It is observed that performance of interspersed tracks can quickly deteriorate after some years. On this ground, a nonlinear simulation of interspersed sleeper railway is conducted using the finite element program, STRAND7, so that the structural damage analysis can be conducted. Two moving point loads representing an axle load along each rail has been established to investigate the worst-case, potential actions for premature damage of sleepers and differential settlement of the track. Dynamic displacement and acceleration of sleeper are then evaluated by varying the speed of the moving force from 5 km/h to 120 km/h and the interspersed patterns to identify the causes of track deterioration and track differential settlement. The insight strongly demonstrates the potential cases and engineering guideline for interspersed railway tracks
Implementation of the Generalized Brazier Effect in Analysis of Wind Turbine Blades
No full textAs wind turbine blades are getting longer and more slender, new failure modes occur and these may be related to the non-linear geometric Brazier effect1,2,3, where the bending moments ovalize the thin-walled cross-sections. For general cross-sections the torsional moments have a similar effect. The combined effect is denoted the general Brazier effect, and it is described in an accompanying paper. The stresses caused by the generalized Brazier effect are directed perpendicular to the beam axis, and this may have a large influence on the fatigue life of composite structure. The generalized Brazier effect can be calculated in an approximate way which enables to add the additional non-linear geometric effects to the results from the wind simulation. This has been described in the accompanying paper, and in this paper focus will be on the practical implementation in a Finite Element program. The accuracy of the proposed method has been illustrated on a wind turbine blade from SSP Technology A/S
Large amplitude free vibrations of spider web structures
Full text linkMost research into natural spider web structures have considered only the small deformation theory based on small amplitude analysis. In reality, spider web structures, which are slender by nature, are more prone to large-amplitude load effects. This paper firstly presents a numerical study into large amplitude free vibrations of spider web structures. Highly coupled geometry and material nonlinearities have been formulated to establish the finite element models of spider web structures. Validation of the model has been carried out using previous research studies into spider web vibrations. Excellent agreement has been obtained for linear and nonlinear perturbation results. The validated FEM has been further extended to investigate the large amplitude effect on natural frequencies and corresponding mode shapes of highly-slender spider webs. Interestingly, this is the world first to report the dynamic softening and hardening phenomenon in the slender spider web structures. The insight into nonlinear dynamics of slender thin membrane skeleton structures can be used not only for better understanding the nature, but also for improving functionalities of defence technology using ultra-thin plates and shells
Proceedings of 29th Nordic Seminar on Computational Mechanics – NSCM29
No full textThis e-volume contains the extended abstracts presented at the 29th Nordic Seminar on Computational Mechanics (NSCM29), held at Chalmers, Göteborg, Sweden, on October 26-28, 2016. The NSCM is organized annually by the Nordic Association for Computational Mechanics (NoACM), which represents the interest for the Nordic and Baltic countries in the European Community on Computational Methods in Applied Sciences (ECCOMAS) and the International Association for Computational Mechanics (IACM). The first NSCM event was held at Chalmers University in Gothenburg, Sweden in 1988. The overall aim of these events is to be a meeting place for researchers developing computational methods and scientists and engineers focusing on challenging applications in broad aspects of mechanics. In particular, presentations by graduate students are welcomed. Thus, making a friendly and creative atmosphere for the participants is considered important. The conference has attracted approximately 100 contributions formulated in 4-5 parallel sessions over four days.
The organizers would like to thank all authors for submitting their contributions, as well as their supporting organizations, to make NSCM29 at Chalmers possible
Proceedings of 14th European Mechanics of Materials Conference - EMMC14
No full textThis volume contains the abstracts presented at the 14th European Mechanics of Materials Conference (EMMC14), held at Chalmers, Göteborg, Sweden, on September 27-29, 2014. The ever increasing development of new engineering materials required to meet advanced technological needs poses new challenges in the field of mechanics of materials. Therefore, the aim of EMMC14 is to bring together researchers, working in various fields of material mechanics and with different backgrounds, to further spread the knowledge and ideas of material mechanics. Mathematical modeling, computational methods and experimental techniques are included. Recent developments that have taken place in the material mechanics field are reflected by the contents of the papers of in these proceedings. The conference has attracted approximately 250 contributions formulated in 6 parallel sessions over three days
Large amplitude free vibrations of spider web structures
Full text linkMost research into natural spider web structures have considered only the small deformation theory based on small amplitude analysis. In reality, spider web structures, which are slender by nature, are more prone to large-amplitude load effects. This paper firstly presents a numerical study into large amplitude free vibrations of spider web structures. Highly coupled geometry and material nonlinearities have been formulated to establish the finite element models of spider web structures. Validation of the model has been carried out using previous research studies into spider web vibrations. Excellent agreement has been obtained for linear and nonlinear perturbation results. The validated FEM has been further extended to investigate the large amplitude effect on natural frequencies and corresponding mode shapes of highly-slender spider webs. Interestingly, this is the world first to report the dynamic softening and hardening phenomenon in the slender spider web structures. The insight into nonlinear dynamics of slender thin membrane skeleton structures can be used not only for better understanding the nature, but also for improving functionalities of defence technology using ultra-thin plates and shells
The Geometric Nonlinear Generalized Brazier Effect:a linearized finite element based solution
No full textA thin walled circular tubular cross section under large bending moments ovalized and this is often denoted as the Brazier effect. This effect can also be seen in other types of profiles such as wind turbine blades. The paper shows that torsional moment gives a similar effect and this has been denoted the generalized Brazier effect. The original work of Brazier dealt with very large deformations that changed the cross section significantly and hereby also the bending moment of inertia and the bending moment capacity.In this paper the aim is to describe the Brazier effect for smaller deformation not taking into account the change in moment of inertia. However, the generalized Brazier effect gives additional stresses directed perpendicular to the beam axis. In composite structures these extra stresses may influence the fatigue life significantly.The paper demonstrates a linearized method to solve the complex non-linear geometric problem with a high accuracy. This is of importance in simulations of wind turbine blades, where the wind load simulations are based on small Finite Element models based on beam type elements in order to be realistic. The linearized solution exploits that the generalized Brazier effect is a local effect not influencing the overall mechanical behavior of the structure significantly. The offset is a nonlinear geometric beam-type Finite Element calculation, which takes into account the large displacements and rotations. The beam-type model defines the stresses which mainly are in the direction of the beam axis. The generalized Brazier effect is calculated as a linear load case based on these stresses
Damage analysis of spot replacement sleepers interspersed in ballasted railway tracks
Full text linkThe interspersed pattern sleeper, a spot replacement of old timber sleeper with concrete or composite counterparts, of railway track is often used as a temporary maintenance for secondary railway lines such as yards, balloon loops or siding. However, their negative effect on the railway has not been taken into account. It is observed that performance of interspersed tracks can quickly deteriorate after some years. On this ground, a nonlinear simulation of interspersed sleeper railway is conducted using the finite element program, STRAND7, so that the structural damage analysis can be conducted. Two moving point loads representing an axle load along each rail has been established to investigate the worst-case, potential actions for premature damage of sleepers and differential settlement of the track. Dynamic displacement and acceleration of sleeper are then evaluated by varying the speed of the moving force from 5 km/h to 120 km/h and the interspersed patterns to identify the causes of track deterioration and track differential settlement. The insight strongly demonstrates the potential cases and engineering guideline for interspersed railway tracks
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