Nonlinear computational framework for hybrid ductile glulam joists

This paper starts by presenting a nonlinear algebraic analysis of hybrid glulam sections, including ductile compression-softening constitutive models obtained via regression analysis of material test data, to compute full-range admissible values of moment (M), co-existent curvature (κ) and excluded-area axial force (Fea) for the sections. The (M,κ,Fea) states, double-checked by treating the section alternately as discretised and as a continuum, are clustered into (M,κ) and (M,Fea) data-sets that permit regression-analysis of κ and Fea as polynomial functions of M. For any load on a glulam member the M profile is known, so κ(M) is a more efficient route to calculating deflections than is M(κ). The κ(M) and Fea(M) constitutive functions, which enable assessment of any section state without tedious recalculation, are fused with longitudinal compatibility and equilibrium requirements to predict the joists’ nonlinear responses up to ultimate. Using quartic or Glos compressive constitutive models, spreadsheet-coding of this framework is shown to predict nonlinear local (κ(M)) and global (load–deflection) responses close to test data, also axial and longitudinal-shear stress redistributions mimicking FE predictions for distributed- or point-loaded hybrid glulam joists comprising combinations of poplar, blue-gum, maritime-pine and larch. The results show that post-peak reductions on compressive stress–strain curves cause through-depth reversal of longitudinal-shear at high moments

Nonlinear magnetic model of surface mounted pm machines incorporating saturation saliency

In this paper a comprehensive nonlinear model of surface mounted permanent magnet synchronous machine (SPMSM) is proposed considering both the structural and the saturation saliencies to enable the numerical simulation of new rotor position detection algorithms. With an identifiable parameter matrix, a numerical nonlinear inductance model is developed, in which the rotor position and the stator current are taken as the variables. After experimentally identifying out all the parameters, a nonlinear mathematic model of SPMSM is built up. With all the machine dimensions and physical parameters, finite-element analysis (FEA) is applied to calculate the magnetic field of the machine. FEA and performance simulation results are used to verify the new nonlinear model, which can be further used as a virtual model to develop, simulate, and verify the saturation saliency detection strategies. © 2009 IEEE

Biomechanical characterization of the periodontal ligament: Orthodontic tooth movement

To quantify the biomechanical properties of the bovine periodontal ligament (PDL) in postmortem sections and to apply these properties to study orthodontic tooth intrusion using finite element analysis (FEA). We hypothesized that PDL’s property inherited heterogeneous (anatomical dependency) and nonlinear stress-strain behavior that could aid FEA to delineate force vectors with various rectangular archwires

A general method for designing the transformer of flyback converters based on nonlinear FEA of electromagnetic field coupled with external circuit

This paper presents a general method for designing the transformer of flyback switching AC-DC converters based on nonlinear finite element analysis (FEA) of electromagnetic field coupled with external circuit. For that, the variation patterns of the PWM duty ratio and the current flowing through the windings of transformer versus the input voltage are introduced first, and then several important principles for the design of the transformer are given by using analytical method. As the magnetic saturation and control delay possess heavy influence on the safety of the operation, a MATLAB/Simulink based simulation model, in which both the nonlinear differential inductance and the control delay are included, is built to predict the converter transient performance. The nonlinear differential inductance is calculated by a general program of nonlinear 2-D FEA in Matlab/Simulink surrounding. By running the model, the performances of the converter with different loads and input voltages are obtained. Simulation results are in good agreement with theoretical analysis

A 2-D nonlinear FEA tool embedded in Matlab/Simulink surrounding for application of electromagnetic field analysis in power converters

This paper presents a 2-D nonlinear finite element analysis (FEA) tool embedded in Matlab/Simulink surrounding for the application of electromagnetic field analysis in power converters. Comparing with other FEA tools such as ANSYS and ANSOFT, as different control arithmetic has been realized in Matlab/Simulink surrounding, the significant advance by using the FEA tool embedded in Matlab/Simulink surrounding is that the field analysis can be more easily interfaced with the external control arithmetic. Considering that the characteristics of most field analyses in power converters which are static electromagnetic equipments, not only the general application procedure of the 2-D FEA tool is introduced, but also some improvements for strengthening its function is proposed. As an example, the proposed model is implemented for the performance analysis of a flyback switching AC-DC converter. By running the proposed model in Simulink surrounding, several performances can be obtained efficiently

THE EFFECT OF CONCRETE-STEEL INTERFACE MODEL ON FINITE ELEMENT ANALYSIS OF CONCRETE FILLED SQUARE STEEL TUBE BEAM

Three-dimensional nonlinear finite element (FEA) is developed to predict the experimental behaviour of concrete filled square steel tubular member. The FEA is conducted to determine moment carrying capacity at ultimate load for simple beam. The concrete-steel interface model is the important parameter affecting the result of FEA simulation. Based on the experimental result, there is a local buckling near the loading contact point. To investigate the local buckling phenomenon, concrete-steel interface model is studied by using contact analysis between concrete and steel elements, by using rigid bar element (rbe2 element) and by using interface elements. The geometrical non-linearity, material non-linearity, loading, boundary conditions is the same for all analysis models. To account for all of these properties, FEA model by means MSC Marc Mentat software is developed. The proposed model can predict the ultimate strength with difference only 5-30%. The collapse modes by FEA model are also compared. Based on the numerical analysis, it can be seen that the local buckling is clearly shown in the FEA model with the concrete and steel interface by using interface elements

An inverse method for determining the spatially resolved properties of viscoelastic–viscoplastic three-dimensional printed materials

A method using experimental nanoindentation and inverse finite-element analysis (FEA) has been developed that enables the spatial variation of material constitutive properties to be accurately determined. The method was used to measure property variation in a three-dimensional printed (3DP) polymeric material. The accuracy of the method is dependent on the applicability of the constitutive model used in the inverse FEA, hence four potential material models: viscoelastic, viscoelastic–viscoplastic, nonlinear viscoelastic and nonlinear viscoelastic–viscoplastic were evaluated, with the latter enabling the best fit to experimental data. Significant changes in material properties were seen in the depth direction of the 3DP sample, which could be linked to the degree of cross-linking within the material, a feature inherent in a UV-cured layer-by-layer construction method. It is proposed that the method is a powerful tool in the analysis of manufacturing processes with potential spatial property variation that will also enable the accurate prediction of final manufactured part performance

Non-Linear Finite Element Analysis of RC Deep Beam Using CDP Model

Finite element analysis (FEA) is widely adopted these days to investigate relatively heavy structures such as reinforced concrete (RC) deep beam, which requires a higher investment of resources. This research aims to investigate a numerical modeling technique applicable to study the nonlinear behavior of RC deep beams by using FEA based on the software, ABAQUS. The nonlinear behavior of an RC deep beam adapted from an earlier research work is captured by using the uniaxial compressive and tensile stress-strain relationship and damage parameters of concrete. The response of the FE model is verified with the experimental results in terms of the load to midspan deflection curve and damage distribution. The ultimate shear capacity predicted by the FE model is 0.75% lower, and the corresponding displacement is 6.92% higher than the experimental results. The adopted modeling technique and the constitutive concrete models demonstrate the promising results indicating its possibilities for the investigation of RC structures

Nonlinear characterization of half and full wavelength power ultrasonic devices

It is well known that power ultrasonic devices whilst driven under elevated excitation levels exhibit nonlinear behaviors. If no attempt is made to understand and subsequently control these behaviors, these devices can exhibit poor performance or even suffer premature failure. This paper presents an experimental method for the dynamic characterization of a commercial ultrasonic transducer for bone cutting applications (Piezosurgery® Device) operated together with a variety of rod horns that are tuned to operate in a longitudinal mode of vibration. Near resonance responses, excited via a burst sine sweep method were used to identify nonlinear responses exhibited by the devices, while experimental modal analysis was performed to identify the modal parameters of the longitudinal modes of vibration of the assemblies between 0-80 kHz. This study tries to provide an understanding of the effects that geometry and material choices may have on the nonlinear behavior of a tuned device