This paper is a contribution to answering the following question: Is it possible to design a permanent-magnet machine with the performance expected from rare-earth magnets, but at a lower cost? ...Performance being understood as torque, size, efficiency, demagnetization and temperature rise together. The question is addressed with a systematic exploration of different interior permanent-magnet machine topologies mixing rare-earth and ferrite permanent magnets. The study starts from a production baseline, the Prius 2010 traction motor, with interior magnets placed in a single V pattern. It investigates various rotor designs, most specifically, single V and double V patterns as well as spoke configurations. The stator cross-section design and winding selection are fixed, providing a solid comparison basis from the point of view of machine cooling. For each rotor design, torque potential and machine material cost are assessed, the latter expressed as torque per dollar. A promising configuration was found, based on a spoke pattern, for which further modeling was performed to assess efficiency as well as mechanical strength and resistance to short circuits and to demagnetization. It reduces the rare earth magnet volume by over 60%.
The present work describes a reliability analysis of strength models for predicting the confinement effect of concrete cylinders with Carbon Fibre Reinforced Polymers (CFRPs) through the Artificial ...Neural Network (ANN). For the reliability analysis, not only current available equations are used but present work also proposes the new empirical equation (Eq-Q) based on the previously conducted experimental work. For which, the database of 708 samples is developed with the detailed information of critical parameters, i.e.; diameter of cylinder (d), height of cylinder (h), unconfined concrete strength (fco'), thickness (nt), elastic modulus of CFRP (Ef), and the ultimate strength of confined concrete (fcc'). The aim of this investigation is achieved in two phases: In first phase, the comparison of current available equations with the proposed ANN model and proposed Eq-Q. In second phase, for the validation purposes of proposed ANN model and Eq-Q, new experimental scheme is developed for the concrete cylinders confined with CFRP and its nonlinear finite element analysis (NLFEA). The NLFEA model after calibration with experimental results is used for further parametric studies. The Comparative studies show that the proposed ANN model, proposed Eq-Q and NLFEA results are in close agreement with the experimental results and give better results as compared to their counterparts.
Background
One of the most common fractures in the skeleton happens in the femur. One of the important reasons for this fracture is because it is the longest bone in the body and osteoporosis affect ...this part a lot. The geometric complexity and anisotropy properties of this bone have received a lot of attention in the orthopedic field.
Methods
In this research, a femur designed using 3D printing machine using the middle part of the hip made of polylactic acid–hydroxyapatite (PLA–HA) nanocomposite containing 0, 5, 10, 15, and 25 wt% of ceramic nanoparticle. Three different types of loadings, including centralized loading, full-scale, and partially loaded, were applied to the designed femur bone. The finite element analysis was used to analyze biomechanical components.
Results
The results of the analysis showed that it is possible to use the porous scaffold model for replacement in the femur having proper strength and mechanical stability. Stress–strain analysis on femoral implant with biometric HA and PLA after modeling was performed using the finite element method under static conditions in Abaqus software.
Conclusion
Three scaffold structures, i.e., mono-, hybrid, and zonal structures, that can be fabricated using current bioprinting techniques are also discussed with respect to scaffold design.
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•A heterogeneous structure was built via a Voronoi-Thiessen based parametric modeling method.•Heterogeneity had little influence on porosity, thus, mechanical/hydrodynamic ...properties.•Irregular local geometry mimicked cancellous bone structure and promoted cellular behavior.•50% heterogeneity (SR structure) kept a balance of structure integrity and osteogenesis.
In nature, many natural porous tissues of animals or plants follow heterogeneous structures pattern. Including turtle back pattern, leaf veins, wood porous fiber and porous cancellous bone are classic heterogeneous structures. In order to better design bionic microenvironment porous bone implants, herein, a bionic porous structure based on Voronoi-Thiessen diagram to create heterogeneous topology microenvironment promoting bone regeneration were proposed. Porous structures with tunable heterogeneity were built and achieved by selective laser melting (SLM). The topology analysis revealed the introduce of heterogeneity brought wide pore size distribution and irregular topology. The mechanical and hydrodynamics properties were predesigned and simulated by finite element analysis (FEA). The heterogeneity hardly influenced the overall strength, stiffness and permeability but the irregular stress and fluid shear rate distribution in FEA results indicated fluctuating local stiffness and permeability. In vitro and in vivo experimental results indicated that Quasi-homogeneous structure had irregular topology mimicking that of the natural bone structure and semi-heterogenous structure shown better osteogenesis. It is found that the scaffold heterogeneous microenvironment factors play important roles for bone regeneration, and which is crucial for the development of new orthopedic implants.
Herein Finite elements analysis (FEA) study assesses the adequacy and accuracy of five failure criteria (Von Mises (VM), Tresca, maximum principal (S1), minimum principal (S3), and Hydrostatic ...pressure) for the study of tooth as a structure (made of enamel, dentin, and cement), along with its stress absorption-dissipation ability. Eighty-one 3D models of the second lower premolar (with intact and 1-8 mm reduced periodontium) were subjected to five orthodontic forces (intrusion, extrusion, tipping, rotation, and translation) of 0.5 N (approx. 50 gf) (in a total of 405 FEA simulations). Only the Tresca and VM criteria showed biomechanically correct stress display during the 0-8 mm periodontal breakdown simulation, while the other three showed various unusual biomechanical stress display. All five failure criteria displayed comparable quantitative stress results (with Tresca and VM producing the highest of all), showing the rotational and translational movements to produce the highest amount of stress, while intrusion and extrusion, the lowest. The tooth structure absorbed and dissipated most of the stress produced by the orthodontic loads (from a total of 0.5 N/50 gf only 0.125 N/12.5 gf reached PDL and 0.01 N/1 gf the pulp and NVB). The Tresca criterion seems to be more accurate than Von Mises for the study of tooth as structure.
In the present study, the low-energy impact response of woven carbon fibre reinforced plastic (CFRP) composite sandwich panels with thermoplastic honeycomb and reentrant cores was investigated ...experimentally and numerically under three different impact energies (20 J, 40 J and 70 J). The Acrylonitrile Butadiene Styrene (ABS) honeycomb and reentrant core structures were manufactured in-plane and out-of-plane oriented via 3D printer, and adhesively bonded with two CFRP face sheets. The results indicate that the in-plane reentrant core based composite sandwich panel exhibits better impact strength and energy dissipation behavior than the in-plane and out-of-plane honeycomb core based composite sandwich panels.
•3D printer technology provides advantages in production of the sandwich core structures with complex geometry.•Composite sandwich panels can be successfully produced by using thermoplastic core structure and CFRP face-sheets.•Reentrant cored composite sandwich panels allow the development of impact strength and energy dissipation ability.•FEM presents an effective solution in modeling low-energy impact response of the composite sandwich structures.
A computationally efficient time‐harmonic finite element model for the steady‐state analysis of a brushless doubly fed induction machine (BDFIM) is proposed. In the model, the electromagnetic ...couplings of the BDFIM are described by means of the sum of two complex magnetic vector potentials that represent the two fundamental harmonic time components of the magnetic flux density distribution in the rotor frame of reference. As in an ordinary induction motor, the non‐linearity of the magnetisation characteristic is accounted for using an effective magnetic permeability. For the BDFIM, this is derived by considering the features of modulated magnetic flux density waveform. The accuracy of the approach has been validated by comparing the characteristics of a D270 machine operating in the double‐feed mode with ones obtained from the experimentally verified time‐stepping model at various operating conditions. High accuracy of the results coming from the proposed model is demonstrated even under deep saturation conditions within the magnetic circuit.
A steady‐state time‐harmonic model for brushless doubly fed induction motor is presented considering non‐linearity of magnetisation characteristic. Effective permeability model is proposed. The approach is validated against time‐stepping model and measurements.
This work aimed to assess the biomechanics, using the finite element method (FEM), of traditional titanium Morse taper (MT) dental implants compared to one‐piece implants composed of zirconia, ...polyetheretherketone (PEEK), carbon fiber‐reinforced PEEK (CFR‐PEEK), or glass fiber‐reinforced PEEK (GFR‐PEEK). MT and one‐piece dental implants were modeled within a mandibular bone section and loaded on an oblique force using FEM. A MT implant system involving a Ti6Al4V abutment and a cp‐Ti grade IV implant was compared to one‐piece implants composed of cp‐Ti grade IV, zirconia (3Y‐TZP), PEEK, CFR‐PEEK, or GFR‐PEEK. Stress on bone and implants was computed and analyzed while bone remodeling prediction was evaluated considering equivalent strain. In comparison to one‐piece implants, the traditional MT implant revealed higher stress peak (112 MPa). The maximum stresses on the one‐piece implants reached ~80 MPa, regardless their chemical composition. MT implant induced lower bone stimulus, although excessive bone strain was recorded for PEEK implants. Balanced strain levels were noticed for reinforced PEEK implants of which CFR‐PEEK one‐piece implants showed proper biomechanical behavior. Balanced strain levels might induce bone remodeling at the peri‐implant region while maintaining low risks of mechanical failures. However, the strength of the PEEK‐based composite materials is still low for long‐term clinical performance.
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In this study, the Voronoi tessellation method has been used to design novel bone like three dimension (3D) porous scaffolds. The Voronoi method has been processed with computer ...design software to obtain 3D virtual isotropic porous interconnected models, exactly matching the main histomorphometric indices of trabecular bone (trabecular thickness, trabecular separation, trabecular number, bone volume to total volume ratio, bone surface to bone volume ratio, etc.). These bone like models have been further computed for mechanical (elastic modulus) and fluid mass transport (permeability) properties. The results show that the final properties of the scaffolds can be controlled during their microstructure and histomorphometric initial design stage. It is also shown that final properties can be tuned during the design stage to exactly match those of trabecular natural bone. Moreover, identical total porosity models can be designed with quite different specific bone surface area and thus, this specific microstructural feature can be used to favour cell adhesion, migration and, ultimately, new bone apposition (i.e. osteoconduction). Once the virtual models are fully characterized and optimized, these can be easily 3D printed by additive manufacturing and/or stereolitography technologies.
The significance of this article goes far beyond the specific objectives on which it is focussed. In fact, it shows, in a guided way, the entire novel process that can be followed to design graded porous implants, whatever its external shape and geometry, but internally tuned to the exact histomorphometric indices needed to match natural human tissues microstructures and, consequently, their mechanical and fluid properties, among others.
The significance is even more relevant nowadays thanks to the available new computing and design software that is easily linked to the 3D printing new technologies. It is this transversality, at the frontier of different disciplines, the main characteristic that gives this article a high scientific impact and interest to a broaden audience.
•A moderate NNBI system (H0 @ >2MW @ 400keV @ >100s) will be established in the framework of CRAFT. A gas neutralizer will be used in the CRAFT NNBI.•The final design of the neutralizer has been ...optimized to reduce the weight, to improve the maintenance and flexibility, to enhance the structural strength, and to increase the manufacturing availability and reliability.•All the machining processes of the neutralizer have been finished, including the deeply drilling channels of 1.7 m in length and 18 mm in diameter.•Assembly of the main body is designed to be implemented in a side-lying position and a trial assembly has been successfully carried out.
The Comprehensive Research Facility for Fusion Technology (CRAFT) is a highly integrated research and development base. It consists of 20 different demonstrating or testing facilities that address most of the critical technologies and systems for the fusion reactor in China. A negative ion-based neutral beam injector (NNBI) test facility is established in CRAFT. A gas neutralizer is applied to the CRAFT NNBI test facility for the neutralization of the negative hydrogen ion beam. The target of the neutralization efficiency is more than 50%. The length of the neutralizer is 3 m. The neutralizer is divided into two adjacent vertical channels and the total opening is 1.7 m × 0.32 m. The neutralizer is mainly composed of channel plate, support structure, beam scraper, cooling water pipes, and gas inlet pipes. Based on the design requirements of the neutralizer, the support structure and cooling water pipes were optimized, to reduce the total weight. The structural strength of all components was simulated and compared to the preliminary design. The manufacturing of the neutralizer is ongoing. Some manufacturing challenges have been overcome, such as deep hole drilling. Several 1.7 m long cooling channels were successfully drilled in a copper panel and the ratio of depth to diameter was 94.
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