Finite Elements

This paper addresses the efficiency of thermal insulation layers applied to protect structural elements strengthened by fiber-reinforced polymers (FRP) in the case of fire event. The paper presents numerical modeling and nonlinear analysis of reinforced concrete (RC) columns externally strengthened by FRP and protected by thermal insulation layers when subjected to elevated temperature specified by standard fire tests, in order to predict their residual capacity and fire endurance. The adopted numerical approach uses commercial software includes heat transfer, variation of thermal and mechanical properties of concrete, steel reinforcement, FRP and insulation material with elevated temperature. The numerical results show good agreement with published results of full-scale fire tests. A parametric study was conducted to investigate the influence of several variables on the structural response and residual capacity of insulated FRP-confined columns loaded by service loads when exposed ...

Two original numerical techniques are developed for the finite element (FE) transient analysis of induction and permanent magnet motors operating in demanding aerospace applications. The first technique is the electromagnetic and thermal analysis weak coupling using a multiple slices 2D FE model. The advantage of the specific technique is the representation of complex actuator geometries including skewed magnets and winding ends, by using a low computational cost 2D model while taking into consideration temperature dependent material attributes. The second technique consists in the development of properly defined boundary conditions for the emulation of the cooling housing of actuators. Those boundary conditions are applied at the outer surface of the actuators in contact with the housing and eliminate the need of modeling complex 3D geometries of highly integrated actuator housings.

A composite beam is made up of a reinforced concrete slab connected to a steel beam by means of shear connectors. If the slab was wide and the composite beam is under positive bending moment, it is evident that the simple beam theory does not strictly apply because the longitudinal stress in the concrete flange will vary with distance from the beam web, the flange being more highly stressed over the web than in the extremities. In this paper a three dimensional linear finite element analysis, using ANSYS program, is done to study the effect of the breadth of the slab on the effective slab width and stress distribution across the slab width (shear lag) of composite steel-concrete beams.
The stresses of concrete and steel are compared with stresses obtained from T-beam theory for variable breadths of concrete slab. Effective width for composite beams with different breadth under various loads has been drawn.

A generalized macroscopic representation of electrical steels used in transformer manufacturing industry is developed. The proposed representation is specifically formulated for integration in the finite element method. Usage of the specific technique enables the accurate evaluation of electromagnetic field distribution of transformer cores under heavily saturated conditions. Advantages over conventional techniques include numerical stability, numerical accuracy, and reduction of iterations of the Newton–Raphson method.

Uncertainties associated with modelling of deteriorating bridges strongly affect management decisions, such as inspection, maintenance and repair actions. These uncertainties can be reduced by the effective use of health monitoring systems, through which information regarding in situ performance can be incorporated in the management of bridges.The objectives of this paper are twofold; first, an improved chloride induced deterioration model for concrete bridges is proposed that can quantify degradation in performance soon after chlorides are deposited on the bridge, rather than when initiation of corrosion at the reinforcement level takes place. As a result, the implications of introducing proactive health monitoring can be assessed using probabilistic durability criteria. Thus, the second objective of the paper is to present a methodology for performance updating of deteriorating concrete bridges fitted with a proactive health monitoring system.This methodology is illustrated via a simple example of a typical bridge element, such as a beam or a part of a slab. The results highlight the benefits from introducing ‘smart’ technology in managing bridges subject to deterioration, and quantify the reduction in uncertainties and their subsequent effect on predictions of future bridge performance.

In this paper a robust three-dimensional (3D) finite element (FE) anisotropy model is introduced based on a particular scalar potential formulation. The specific 3D FE model is suitable for the accurate evaluation of the peak flux density distribution and no load loss of one-phase and three-phase wound core distribution transformers. The accuracy of the proposed 3D FE anisotropy model is validated by local flux density and no load loss measurements.

Nowadays, the integration of different mechanical design process stages (Design, analysis and manufacturing) of is a necessity so as to reduce the time of design and optimization. This tendency of integration CAD/CAM/Analysis and automation of the corresponding processes requires shared data between the various tasks using an integrated product model. Our research is oriented to CAD/CAM/Analysis integration by rebuilding the CAD model (BREP) starting from the CAE results (deformed mesh).

A detailed study was carried out on crankshafts used in two wheeler made from C45 (EN 8/AISI 1042) steel. Undesirable noise was heard in crankshaft when the engine is in running. This was stated as failure of crankshaft. Material has been peeled off and seemed to be scraped at the central portion of the crankpin.  It was the bearing seating place where oil hole also provided. Under analysis the crankpin was identified as tempered. Chemical composition, micro-hardness and microstructure were studied and compared with the specified properties of the crankpin material. Reason for failure is identified as wear due to lower hardness, improper lubrication and high operating oil temperature.

In this paper a typical soil–structure interaction problem is considered, the case of a vertical pile installed in sand and submitted to an axial compression loading. Results from two full scale pile tests are analysed and the tests are reproduced by numerical simulations via finite ...

A stabilized, nodally integrated linear tetrahedral is formulated and analysed. It is well known that linear tetrahedral elements perform poorly in problems with plasticity, nearly incompressible materials, and acute bending. For a variety of reasons, low-order tetrahedral elements are preferable to quadratic tetrahedral elements; particularly for nonlinear problems. But the severe locking problems of tetrahedrals have forced analysts to employ hexahedral formulations for most nonlinear problems. On the other hand, automatic mesh generation is often not feasible for building many 3D hexahedral meshes. A stabilized, nodally integrated linear tetrahedral is developed and shown to perform very well in problems with plasticity, nearly incompressible materials and acute bending. The formulation is analytically and numerically shown to be stable and optimally convergent for the compressible case provided sufficient smoothness of the exact solution u ∈ C2 ∩ (H1)3. Future work may extend the formulation to the incompressible regime and relax the regularity requirements; nonetheless, the results demonstrate that the method is not susceptible to locking and performs quite well in several standard linear and nonlinear benchmarks. Published in 2006 by John Wiley & Sons, Ltd.

Vehicle door latch minimum force capability testing presently utilizes uniaxial quasi-static loading conditions created toward the middle of the last century. Current technology enables more sophisticated virtual testing of a broad range of systems. Door latch failures have been observed in vehicles under a variety of conditions. Typically these conditions involve multiple axis loading conditions. The loading conditions presented during rollovers on passenger vehicle side door latches are not currently evaluated. Background on these conditions is reviewed. Rollover crash test results, rollover crashes and physical FMVSS 206 latch testing are reviewed. In this paper, the creation and validation of a passenger vehicle door latch model is described. The multi-axis loading conditions observed in virtual rollover testing at the latch location are characterized. These loads are then applied to the virtual testing of a latch in both the secondary and primary latch positions. The results are then compared with crash test and real world rollover results for the same latch. The results indicate that while a door latch in the secondary latch position may meet minimum existing uniaxial horizontal plane loading requirements, the incorporation of multi-axis loading conditions may result in failure of the latch to accomplish its intended purpose at loads substantially below the FMVSS 206 uniaxial failure loads. The findings suggest the need for reexamining the relevance of existing door latch testing practices in light of the prevalence of rollover impacts and other impact conditions in today's vehicle fleet environment.

Even though, the transformer is the most efficient of electrical machines, with efficiencies typically in the high 90s, it is possible to reduce transformer costs and losses by using composite magnetic cores. This paper presents a new composite magnetic core that can be used effectively for manufacturing single–phase and three–phase wound core distribution transformers. The new composite wound core concept is based on experimental evidence concerning the flux density non–uniformity of conventional single–phase and three–phase magnetic wound cores and the losses and magnetization properties of conventional and high permeability Si–Fe grain–oriented steels. A systematic experimental losses and flux distribution analysis of single phase and three–phase magnetic wound cores is undertaken as well as finite element (FE) analysis considering the bulk anisotropic characteristics of laminated wound cores.

This paper presents a finite-element (FE) study conducted to investigate the deflections of newly constructed cantilevered slabs built for a medical facility expansion. From the beginning of the construction stage, the deflections of the newly built cantilevers caused disputes among the owner, contractor, and the structural engineer of record. The study presented here was performed to understand whether the cantilevers were designed and built to conform to the governing codes. The cantilever deflections at three levels and their relative displacements were studied in detail for comparison with the measured values at the job site and code limitations. The mainstream structural engineering software programs predominantly used in structural engineering offices are generally run to identify the most critical load combinations, critical forces, moments, and deflections of structural members; however, a deflection study such as the one described here requires an extensive FE model created with comprehensive software like ANSYS to investigate the sequential loading of cantilever deflections. In ANSYS, the reinforced concrete behavior can be simulated with SOLID65 elements, which provide an excellent fit for representing the true stress-strain diagram of reinforced concrete. The FE modeling with ANSYS SOLID65 elements for flat slab cantilever deflections have not been discussed in detail in a technical publication before: This study fills that gap. The study not only covers the detailed FE modeling with SOLID65 elements, but it also compares the results with the measured deflections and code requirements. In addition, the study provides recommendations for avoiding excessive deflections in cantilevered reinforced concrete construction.

The losses in European Union distribution transformers are estimated at about 33 TW · h/year, whereas reactive power and harmonic losses add a further 5 TW · h/year. The reduction of distribution transformer no-load loss is particularly important as the ratio of no-load to load losses is nearly three. In this paper, the no load operation of wound-core transformers under sinusoidal and distorted supply-voltage conditions is investigated. For that purpose, a 2-D nonlinear transient finite-element analysis taking into account hysteresis has been developed. The hysteresis model is based on a modified Jiles–Atherton representation, and the proposed analysis is compared to experimental data.