Finite Element Analysis of Microwave Transmission-Lines Employing a Self Adaptive Mesh Technique with an Efficient Element Subdivision Algorithm

It is important to establish an integrated CAD system for mechanical engineering. The geometric model is constructed with primitives, such as wire frame, surface and solid on this system. The finite element model is induced from the substructure, which is a component of the geometric model. After the extraction of the substructure from the model, the mesh for the finite element analyses is automatically generated against the substructure. An approach to automatic mesh generation is discussed on this paper, based upon the techniques of interpolation with the blending function, originally developed for geometric modeling. But, the blending function may produce unexpected results when the mesh is generated, due to the nature of the algorithm. In order to conclude with expected results for automatic mesh generation, and accuracy-fitting method is introduced.

A fuzzy logic knowledge-based approach, FUZZYMESH, for finite element mesh generation and analysis is presented. The proposed approach initiates the adaptive process with a high quality initial mesh that is more refined around the critical points/regions in the problem domain. In order to create high quality initial meshes, the heuristic knowledge, past experience, common sense, and ad hoc methods of finite element specialists are incorporated into the knowledge base of the fuzzy system. Using the linguistic variable concept and approximate reasoning techniques, the fuzzy system makes expert decisions about the initial mesh design by considering the geometric information, as well as the boundary and loading conditions. The decision process includes the determination of priority of critical points/regions and the prediction of mesh sizes for them. According to the mesh size information, a near-optimal initial mesh is created with an automatic mesh generator that is based on the advancing front mesh generation technique. The performance of the proposed approach was measured and evaluated in terms of efficiency and accuracy. The evaluation included comparison between the results of a code based on the proposed fuzzy logic knowledge-based approach, FUZZYMESH, and the conventional approach, which starts the finite element analysis with different meshes, by solving various problems. The global as well as local errors of different solutions were examined and compared. The CPU times for different approaches to achieve a particular accuracy were also measured and compared. The results showed that due to better quality of initial meshes, FUZZYMESH results in lower levels and more accurate error estimates. In turn, the proposed approach is able to solve the problem with a more accurate solution at less cost.

Application of automated cubic-order mesh generation for efficient energy transfer using parabolic arcs for microwave problems

<div class="htmlview paragraph">A set of methods is described to calculate boundary conditions for thermal and mechanical finite element (FE) analyses and to assess and present the results of those analyses in a clear and understandable way. The approach utilizes a combination of engine simulation programs and an empirical database of engine measurements developed over many years. The methodology relies on the use of specialized FE pre- and post-processors dedicated to the analyses of engine components.</div> <div class="htmlview paragraph">Gas-side thermal boundary conditions for combustion chamber components are calculated using an engine simulation code for standalone FE analyses or for FE analyses directly coupled to the engine simulation code itself. Coolant side boundary conditions are calculated using multidimensional flow analysis (computational fluid dynamics). Boundary conditions in intake and exhaust manifolds are calculated using a one-dimensional gas dynamics code.</div> <div class="htmlview paragraph">Thermo-mechanical analysis results are assessed and presented using dedicated post-processing tools to determine the effects of temperature on local material strength, and to calculate distributions of safety factor against ultimate strength, yield strength and fatigue strength. New methods of results presentation are described for the analysis of cylinder bore distortion, piston-liner interaction, cylinder liner cavitation and valve seat wear.</div>

Objective To explore the establishment of 3D thoracic model by finite element methods, and study the mechanical mechanism of minimally invasive surgery for correcting the chest wall deformity, and provide personalized surgery solution in the future. Methods According to admission and exclusion criteria, we selected 10 cases of pectus carinatum that received chest CT scan. The finite element model of pectus carinatum was established and analyzed by Mimics, ABAQUS, etc. The validity of finite element method for chest wall was verified by comparing the sternal displacement between the simulated values and actual values with the same force. Results The 3D finite element model of pectus carinatum was successfully established and analyzed. The stress distribution of the 10 cases in the posterior ribs was mainly in the 1-6 ribs on both sides, mostly concentrated in the 4th to 6th ribs, and the stress was symmetrical on both sides. Statistical analysis showed that the displacement value of the sternum was correlated, and the validity of the model was verified. Conclusion Mimics, ABAQUS and other finite element modeling and analysis software can effectively establish the thoracic 3D finite element model and mechanical analysis, which can help the further development of personalized minimally invasive surgery for correcting chest wall deformities. Key words: Pectus carinatum; Chest wall deformity; Finite element analysis

An adaptive finite element technique for thermal stress analysis of built-up structures has been developed. A finite element formulation for a triangular membrane element and a new plate bending element, used for modelling such structures under both mechanical and thermal loadings, is presented. The associated finite element matrices have been derived in closed form. The performance of the new plate bending element is evaluated for a plate with temperature gradient through its thickness by comparing the predicted solution with the exact solution. The effectiveness of the adaptive meshing technique combined with the finite element method is evaluated by thermal stress analysis of a built-up structure with intersecting panels. The application demonstrates that the adaptive meshing technique can provide an accurate solution with fewer elements and shorter computational time than the standard finite element procedure.

A finite element based method for estimating natural frequencies of locally damaged homogeneous beams

The operational behavior of a six-phase, 2 poles and 36 stator slot squirrel cage induction machine is analyzed for the effects of stator slot openings in this paper. The study is carried out using the field analysis method and the finite element analysis (FEA) of the two dimensional commercially available finite element QuickField modeling Package. Experimental analysis is conducted on a 1.5 kW machine to validate the integrity of the theoretical method of the original opening slot. The FEA analysis is carried out for no-load (Magnetostatics) and loaded conditions (steady state AC Magnetics). The results show that decreasing the slot opening of the stator winding increases the performance of the machine.

In spite of recent advancements in computer aided design and engineering (CAD/CAE), such as parametric geometry and automatic mesh generation, a large gap exists between computer based design model and analysis model. In this paper, a new product specific approach to integrate design and analysis integration is proposed. The primary objective of this approach is to capture designer’s intent from the limited interaction with the designer in a language that is familiar to designer and to provide the feed back on the suitability of the design based on the finite element analysis (FEA) so that the design is automatically and iteratively modified. Hence, the proposed modeling paradigm provides capabilities of analysis to the designer and acts as a black box without requiring the designer to possess relevant knowledge of FEA. Priority has been given to the class of problems termed as routine analysis – the regularly used, established analysis model in the product design. A representative case study pertaining to Belleville spring is discussed in the context of the proposed methodology to demonstrate that it enables highly automated routine analysis through FEA for the model.

The combination of thin-walled steel structure with concrete infill can be used as the alternative material properties in the building in Indonesia. This composite material is suitable for seismic-resistant building because it has more ductility than conventional material. In the tsunami event, some tsunami debris strikes the building and induced partial or full collapse of the building. The loading tip shape of tsunami debris which contacts to a tubular surface affects the local deformation or buckling mode of the thin-walled structures. In order to investigate the effects, we conducted three-dimensional nonlinear finite element analyses of concrete filled square steel tubular members subjected to concentrated lateral loads by using the finite element analysis (FEM) program MSC Marc/Mentat. The fiber element analysis is also performed to reduce the analysis time of FEM and simplify the analysis. The accuracy of the FEM and fiber element analysis is verified by the experiment. Being based on the parametric numerical study, it discusses the effect of axial load on the load-deflection relations. It shows that the higher the axial load, the more degradation the ductility of the structure.

Finite element prediction with experimental validation of damage distribution in single trabeculae during three-point bending tests

A modified fracture-mechanics method for the prediction of fatigue failure from stress concentrations in engineering components

The present study aimed to identify the optimal design of the unicompartmental femoral component through parameter analysis and stability evaluation. A finite element (FE) analysis was applied to analyse and adjust the parameter combinations of the anterior tilt angle of the posterior condyle resection surface, the position of the peg, the length of the pegand the inclination angle of the peg, resulting in 10 different FE models. Setting three knee flexion angles of 8.4° (maximum load state during walking), 40° (maximum load state during stair climbing)and 90° (maximum load state during squatting exercise), quantitatively analysing the micromotion values of the bone-prosthesis interfaceand defining a weighted scoring formula to evaluate the stability of different FE models. The validity of the FE analysis was verified using the Digital Image Correlation (DIC) device. The errors between the FE analysis and the DIC test at three flexion angles were 5.6%, 1.7%and 11.1%. The 10 different femoral component design models were measured separately. The FE analysis demonstrated that the design with a 0° anterior tilt angle of the posterior condyle resection surface, both pegs placed on the distal resection surface, lengthened 5 mm pegsand a 10° peg inclination angle provided the best stability. The current study proposed a method for evaluating the stability of the femoral component design. The optimal intersurface stability design of the unicompartmental femoral component was achieved with two pegs placed on the distal resection surface, a 5-mm peg length incrementand a 10° peg inclination. These results might provide a reference for the selection of unicompartmental femoral components in clinical practice and therefore improve the survival rate of future unicompartmental knee arthroplasty. Level III.

Field investigation and finite element analysis on expansion and shrinkage strains of expansive concrete structures

In a finite element (FE) analysis of the lumbar spine, different preload application methods that are used in biomechanical studies may yield diverging results. To investigate how the biomechanical behaviour of a spinal implant is affected by the method of applying the preload, hybrid-controlled FE analysis was used to evaluate the biomechanical behaviour of the lumbar spine under different preload application methods. The FE models of anterior lumbar interbody fusion (ALIF) and artificial disc replacement (ADR) were tested under three different loading conditions: a 150 N pressure preload (PP) and 150 and 400 N follower loads (FLs). This study analysed the resulting range of motion (ROM), facet contact force (FCF), inlay contact pressure (ICP) and stress distribution of adjacent discs. The FE results indicated that the ROM of both surgical constructs was related to the preload application method and magnitude; differences in the ROM were within 7% for the ALIF model and 32% for the ADR model. Following the application of the FL and after increasing the FL magnitude, the FCF of the ADR model gradually increased, reaching 45% at the implanted level in torsion. The maximum ICP gradually decreased by 34.1% in torsion and 28.4% in lateral bending. This study concluded that the preload magnitude and application method affect the biomechanical behaviour of the lumbar spine. For the ADR, remarkable alteration was observed while increasing the FL magnitude, particularly in the ROM, FCF and ICP. However, for the ALIF, PP and FL methods had no remarkable alteration in terms of ROM and adjacent disc stress.