Behaviour and design of composite beams subjected to negative bending and compression

This paper investigates the behaviour of steel–concrete composite beams subjected to the combined effects of negative bending and axial compression. Six full-scale tests were conducted on composite beams subjected to negative moment while compression was applied simultaneously. Following the tests, a nonlinear finite element model was developed and calibrated against the experimental results. The model was found to be capable of predicting the nonlinear response and the ultimate failure modes of the tested beams. The developed finite element model was further used to carry out a series of parametric analyses on a range of composite sections commonly used in practice. It was found that, when a compressive load acts in the composite section, the negative moment capacity of a composite beam is significantly reduced and local buckling in the steel beam is more pronounced, compromising the ductility of the section. Rigid plastic analysis based on sectional equilibrium can reasonably predict the combined strength of a composite section and, thus, can be used conservatively in the design practice. Based on the experimental outcomes and the finite element analyses a simplified design model is proposed for use in engineering practice

An internal variable constitutive model for the large deformation of metals at high temperatures

The advent of large deformation finite element methodologies is beginning to permit the numerical simulation of hot working processes whose design until recently has been based on prior industrial experience. Proper application of such finite element techniques requires realistic constitutive equations which more accurately model material behavior during hot working. A simple constitutive model for hot working is the single scalar internal variable model for isotropic thermal elastoplasticity proposed by Anand. The model is recalled and the specific scalar functions, for the equivalent plastic strain rate and the evolution equation for the internal variable, presented are slight modifications of those proposed by Anand. The modified functions are better able to represent high temperature material behavior. The monotonic constant true strain rate and strain rate jump compression experiments on a 2 percent silicon iron is briefly described. The model is implemented in the general purpose finite element program ABAQUS

Finite Element Analysis of Collapse of Metallic Tubes

Quasi-static axial and lateral compression tests were conducted on aluminium tubes of circular,rectangular, and square cross sections on a universal testing machine (Instron model 1197).During the compression process, different tubes were collapsed in different modes of collapse.These compression processes were also modelled using FORGE2 finite element code. The codehas the capabilities of automatic mesh generation, modelling of die, creation of material data file,carrying out the finite element computations, and post-processing of results. The deformingtube material was modelled as rigid-visco-plastic. Development of different modes of collapsewas investigated experimentally and computationally. The experimental load-compression curvesand deformed shapes are compared with the computed results and found in good agreement.It is found that the proposed finite element models of the different compression processes arecapable of predicting the modes of collapse

Microstructure modelling of hot deformation of Al–1%Mg alloy

This study presents the application of the finite elementmethod and intelligent systems techniques to the prediction of microstructural mapping for aluminium alloys. Here, the material within each finite element is defined using a hybrid model. The hybrid model is based on neuro-fuzzy and physically based components and it has been combined with the finite element technique. The model simulates the evolution of the internal state variables (i.e. dislocation density, subgrain size and subgrain boundary misorientation) and their effect on the recrystallisation behaviour of the stock. This paper presents the theory behind the model development, the integration between the numerical techniques, and the application of the technique to a hot rolling operation using aluminium, 1 wt% magnesium alloy. Furthermore, experimental data from plane strain compression (PSC) tests and rolling are used to validate the modelling outcome. The results show that the recrystallisation kinetics agree well with the experimental results for different annealing times. This hybrid approach has proved to be more accurate than conventional methods using empirical equations

Methods for Predicting Mechanical Deformations in the Breast During Clinical Breast Biopsy

A new method for clinical breast biopsy is presented, based on a deformable finite element model of the breast. The geometry of the model is constructed from MR data, and its mechanical properties are based on a nonlinear material model. This method allows imaging the breast without compression before the procedure, then compressing the breast and using the finite element model to predict the tumor\u27s position

A Randomized Proper Orthogonal Decomposition Method for Reducing Large Linear Systems

The proper orthogonal decomposition (POD) method is a powerful tool for reducing large data systems which can quickly overwhelm modern computing tools. In this thesis we provide a link between randomized projections and statistical methods by introducing the randomized POD method. We also apply the POD method to a heat transfer finite element model and image compression. In doing so we demonstrate the practical use and quantify the error introduced by the POD method.Aerospace Engineerin

Variant Reorientation in Single-crystal Shape-memory Alloys

In this work we model the variant reorientation in a single crystal NiMnGa magnetic shapememory alloy using the crystal-mechanics-based constitutive model of Thamburaja[1]. The model has been implemented in the ABAQUS/Explicit finite-element program by writing a user-material subroutine. Its numerical simulations quantitatively predict the mechanical response in simple compression and plain strain compression experiments to good accord

Cellular buckling in stiffened plates

An analytical model based on variational principles for a thin-walled stiffened plate subjected to axial compression is presented. A system of nonlinear differential and integral equations is derived and solved using numerical continuation. The results show that the system is susceptible to highly unstable local--global mode interaction after an initial instability is triggered. Moreover, snap-backs in the response showing sequential destabilization and restabilization, known as cellular buckling or snaking, arise. The analytical model is compared to static finite element models for joint conditions between the stiffener and the main plate that have significant rotational restraint. However, it is known from previous studies that the behaviour, where the same joint is insignificantly restrained rotationally, is captured better by an analytical approach than by standard finite element methods; the latter being unable to capture cellular buckling behaviour even though the phenomenon is clearly observed in laboratory experiments.Comment: 22 pages, 9 figures, 1 table, accepted for publication. Proceedings of the Royal Society A, 201

Numerical analysis of the load bearing capacity of pin-ended hybrid headed columns under uniaxial loading

The behaviour of fully encased composite columns loaded in axial compression through the concrete core and whole cross-section was studied. The primary objective is to develop a complete non-linear finite element model that could represent the behaviour of fully encased composite columns tested under uniaxial compression in the laboratory. A total of 10 models were analyzed using finite element simulations and the results obtained were compared with laboratories' test results. The finite element package LUSAS 14 has been used to carry out non-linear analyses of models in order to study the ultimate load behaviour and ultimate load-carrying capacity of the columns. The effects of parameters such as length of composite columns and loading condition on the ultimate load capacity have been examined. This study implies that load condition has significant influence on the behaviour and strength of the composite columns. Moreover, it is suggested that the finite element models were able to simulate various loading conditions, with very good accuracy