Papers by Keyword: Finite Element Modeling (FEM)

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Authors: Xing Hua Chen, Piotr Omenzetter
Abstract: Because of the critical role that bridges play in land transport networks and broader economy, the assessment of existing bridges is gradually becoming a global concern. Structural health monitoring (SHM) systems have been installed on many bridges to provide data for the evaluation of bridge performance and safety. The challenge for bridge engineers is now to make use of the data and convert them into usable information and knowledge. Integrating SHM data with reliability analysis procedures offers a useful and practical methodology for bridge assessment since reliability is an important performance index and reliability-based procedures have the capability of accommodating uncertainties in structural models, responses, loads and monitoring data. In this paper, an approach for integrating SHM data in a reliability assessment framework is proposed. The reliability of the bridge is quantified by incorporating SHM information in the resistance, load and structural models. Advanced modeling tools and techniques, such as finite element analysis, finite model updating and Bayesian updating, are used for the reliability computations. Data from the SHM system installed on the Newmarket Viaduct, a newly constructed, 12-span, post-tensioned box girder bridge erected by the balanced cantilever method in Auckland, New Zealand, are also presented in this paper and used to explain the proposed framework.
Authors: Rui Miguel Ferreira Paulo, Filipe Teixeira-Dias, Robertt A.F. Valente
Abstract: Stiffened panels are composed of a base plate with stiffeners in one or more directions, leading to lightweight structures with high resistance. The structural design, in most cases, focuses mainly on the longitudinal compressive loads that the panels are subjected and can safely withstand. In the present work, a set of Finite Element Method Analyses (FEA) were carried out, using ABAQUS commercial simulation software, and compared with experimental data in order to infer about the sensitivity of the results to the initial geometrical imperfections (either in magnitude and shape). The developments in the present work aim to provide a range of models able to properly reproduce the experimental behaviour of aluminium stiffened panels subjected to compressive loads. It was shown that FEA using shell finite elements were able to obtain accurate predictions of the ultimate load, considering large deformation and elasto-plastic behaviours. The effect of using different shapes and magnitudes of the initial geometrical imperfections on the numerical simulation of the panels was also inferred and tested using previously obtained eigenvalue (EV) buckling modes.
Authors: C. Mahesh, Anindya Deb, S.V. Kailas, C. Uma Shankar, T.R.G. Kutty, K.N. Mahule
Abstract: The characterization of a closed-cell aluminum foam with the trade name Alporas is carried out here under compression loading for a nominal cross-head speed of 1 mm/min. Foam samples in the form of cubes are tested in a UTM and the average stress-strain behavior is obtained which clearly displays a plateau strength of approximately 2 MPa. It is noted that the specific energy absorption capacity of the foam can be high despite its low strength which makes it attractive as a material for certain energy-absorbing countermeasures. The mechanical behavior of the present Alporas foam is simulated using cellular (i.e. so-called microstructure-based) and solid element-based finite element models. The efficacy of the cellular approach is shown, perhaps for the first time in published literature, in terms of prediction of both stress-strain response and inclined fold formation during axial crush under compression loading. Keeping in mind future applications under impact loads, limited results are presented when foam samples are subjected to low velocity impact in a drop-weight test set-up.
Authors: Markos Petousis, Achilles Vairis, Betina Kandyla, George Stefanoudakis, Nektarios Vidakis
Abstract: The anterior cruciate ligament in the knee connects the femur to the tibia and is often torn during a sudden twisting motion, resulting in knee instability. Effective treatment is with surgery where the ligament is replaced with a piece of healthy tendon grafted into place to hold the knee joint together. Employing a novel repair device, models for the repaired and for the intact knee are developed to evaluate the efficacy of the design the device.
Authors: Vipulkumar I. Patel, Ondrej Muránsky, Cory J. Hamelin, Mitch D. Olson, Michael R. Hill, Lyndon Edwards
Abstract: Welding processes create a complex transient state of temperature that results in post-weld residual stresses. The current work presents a finite element (FE) analysis of the residual stress distribution in an eight-pass slot weld, conducted using a 316L austenitic stainless steel plate with 308L stainless steel filler metal. A thermal FE model is used to calibrate the transient thermal profile applied during the welding process. Time-resolved body heat flux data from this model is then used in a mechanical FE analysis to predict the resultant post-weld residual stress field. The mechanical analysis made use of the Lemaitre-Chaboche mixed isotropic-kinematic work-hardening model to accurately capture the constitutive response of the 316L weldment during the simulated multi-pass weld process, which results in an applied cyclic thermo-mechanical loading. The analysis is validated by contour method measurements performed on a representative weld specimen. Reasonable agreement between the predicted longitudinal residual stress field and contour measurement is observed, giving confidence in the results of measurements and FE weld model presented.
Authors: Anshul Sharma, C.K. Susheel, Rajeev Kumar, V.S. Chauhan
Abstract: In this paper, a finite element model of piezolaminated composite shell structure is developed using nine-noded degenerated shell element. The stiffness, mass and thermo-electro-mechanical coupling effect is incorporated in finite element modeling using first order shear deformation theory and linear piezoelectric theory. The sensor voltage is calculated using the same formulation and fuzzy logic controller is used to calculate the actuator voltage. The fuzzy logic controller is designed as double input-single output (DISO) system using 49 If-Then rules. The performance of fuzzy logic controller is compared with convention constant-gain negative feedback controller. The simulation results illustrate the superiority of fuzzy logic controller over constant-gain negative feedback controller.
Authors: Arkadeb Banerjee, Sankar Dhar, Sanjib Acharyya, Debasis Datta, Nityananda Nayak
Abstract: An experimental programme for determination of the Johnson Cook material and failure model constants for a typical armour steel material is reported. Tensile tests on specimens made from the armour material have been conducted at quasi-static and dynamic strain rates and at ambient and elevated temperatures. The analysis of the experimental data generates the model constants that are required as inputs during numerical simulation of dynamic events like armour impact using Johnson Cook constitutive relation and failure model implemented in most of the commercially available Finite Element codes.
Authors: Jun Liu, Ming Jen Tan, Sylvie Castagne, Samuel C.V. Lim
Abstract: The process parameters used in the hybrid superplastic forming have been optimized. Since the hybrid process was a combination of hot drawing and gas blow forming, the effects related with the two forming phases were taken into account to facilitate the process design. The punch shape has been modified. A two-stepped punch in accordance with the die geometry with length of 43 mm was used in this work. Finite element modeling (FEM) was carried out to detect the low-plastic-strain areas, where the materials would have capabilities to be deformed more as the temperature increased. The non-isothermal heating system was then adopted to heat up these selected areas to improve the material formability during deformation. The maximum thickness thinning of the formed sample was 40%. Microstructures observed via electron backscattered diffraction (EBSD) have shown the occurrence of grain growth and recrystallization. It is clear that no big structure defect resulting from large plastic deformation was found.
Authors: Pedro Henrique R. Pereira, Túlio H.P. Costa, Roberto B. Figueiredo, Paulo Roberto Cetlin, Terence G. Langdon
Abstract: The production of ultrafine-grained metals through severe plastic deformation (SPD) has attracted significant interest in the scientific community due to the improvement in mechanical properties. Among SPD methods, high pressure torsion (HPT) processing is most effective in producing exceptionally small grains in disc-shaped samples subjected to high hydrostatic pressures and concurrent torsional straining. The present paper analyzes the elastic distortions and plastic flow during the application of compressive pressure in samples during HPT. Simulations through finite element method reveal a distortion of the initial shape of the sample and a gradient in sample thickness between the center and the edge due to elastic distortions. Also, it is shown that significant plastic deformation takes place in this stage and this is before any torsional deformation is imposed on the sample.
Authors: Cui Ling Li, Shu Ying Qu, Ruo Yang Wu, Fan Bo Meng
Abstract: Deflection and stress of different cross section forms and its value are compared by finite element analysis of timberwork design model under the impact loading. The result indicates that decreasing the size of cross section or changing the section shape can effectively avoid the model too heavy and conservative design. In the case of horizontal loads applied on first floor, strengthening the column of first floor obviously reduces the deflection of model and improves the lateral stiffness. Keeping the column size of the first floor and choosing I-section significantly reduce the overall weight on condition of meeting the bearing capacity and stability, it also make the material higher utilization.
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