Vernier permanent-magnet (VPM) machines have been obtaining a lot of attention over the past few years due to several advantages, such as their high torque density and simple mechanical structures. ...Moreover, it is found that the torque ripple of VPM machines is ultralow, even without specific design measures such as a short pitch, skewing slots/poles, magnet shaping technology, etc. This paper presents theoretical analysis and comprehensive simulations on the torque ripple of VPM machines. First, a general instantaneous torque equation of VPM machines is proposed to analyze torque features and the effect of parameters on the torque performance of VPM machines. Subsequently, based on the general torque equation and a finite-element algorithm, it is verified that torque smoothness is the inherent characteristic of VPM machines, and the torque ripple of VPM machines can be below 0.2%. Furthermore, it is demonstrated that the torque density of a VPM machine is 40% larger than that of a regular permanent-magnet machine. All these advantages demonstrate that VPM machines can obtain much better steady and dynamic drive performance. Finally, all the theoretical analyses are verified by experiments on a VPM prototype.
Numerical simulations are used in this work to investigate aspects of microstructure and microsegregation during rapid solidification of a Ni-based superalloy in a laser powder bed fusion additive ...manufacturing process. Thermal modeling by finite element analysis simulates the laser melt pool, with surface temperatures in agreement with in situ thermographic measurements on Inconel 625. Geometric and thermal features of the simulated melt pools are extracted and used in subsequent mesoscale simulations. Solidification in the melt pool is simulated on two length scales. For the multicomponent alloy Inconel 625, microsegregation between dendrite arms is calculated using the Scheil-Gulliver solidification model and DICTRA software. Phase-field simulations, using Ni–Nb as a binary analogue to Inconel 625, produced microstructures with primary cellular/dendritic arm spacings in agreement with measured spacings in experimentally observed microstructures and a lesser extent of microsegregation than predicted by DICTRA simulations. The composition profiles are used to compare thermodynamic driving forces for nucleation against experimentally observed precipitates identified by electron and X-ray diffraction analyses. Our analysis lists the precipitates that may form from FCC phase of enriched interdendritic compositions and compares these against experimentally observed phases from 1 h heat treatments at two temperatures: stress relief at 1143 K (870 °C) or homogenization at 1423 K (1150 °C).
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Toughening matrix materials by incorporating rigid nanoparticles has received significant interest for mitigating matrix microcracking in fibre-reinforced polymer-matrix composites, particularly at ...cryogenic temperatures. Despite recent experimental observations indicating the effectiveness of nanoparticle toughening, a notable gap remains in understanding the effects of nanoparticle size and volume fraction, and particle-matrix interfacial properties, on toughening efficacy. To address this gap, a multiscale model has been developed which employs a high-fidelity micromechanical model to quantify the deformation and energy dissipation caused by the rigid nanoparticles under a triaxial strain state determined from a macroscopic elastoplastic analysis. The interface between the nanoparticle and the matrix is characterized by a cohesive zone model (CZM), revealing a size-dependent phenomenon distinct to nanoparticles, sharply contrasting with micrometre-sized particles. Furthermore, the results reveal, for the first time, an optimum particle size that maximizes the toughening effect for a given particle-matrix combination. The existence of an optimum size is ascribed to the incomplete particle debonding from the matrix as the particle radius approaches the critical separation distance of the CZM. This revelation challenges the prevailing belief that, for a fixed volume fraction of nanoparticles, the enhancement in toughness rises as the particle size decreases as a result of the increase in total particle surface area. The implications for enhancing cryogenic performance are explored.
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•A multiscale model unravels the origin of nanoparticle toughening in epoxy.•Discovery of the existence of optimum particle size and volume fraction that maximize the toughening efficiency.•Quantification of the significant role of particle-matrix interface in toughening.
•A three-linear CZM is proposed based on the microscopic failure mechanism of the delamination in composite laminates.•Bridging stress is experimentally obtained by J-integral method and implemented ...into the new CZM using a user-subroutine UMAT.•A sensitivity analysis shows that the interfacial strength has little effect on the simulated results.
Fiber bridging has a significant influence on the delamination propagation behavior in multidirectional composite laminates. Traditional pure mode I bilinear cohesive zone models (CZM) do not consider the effect of fiber bridging and result in an inaccurate simulation on the delamination behavior. This study proposed a physical-based three-linear CZM superposed by two bilinear CZMs, which represent two different phenomena including the quasi-brittle matrix fracture characterized by a higher peak stress and a shorter critical opening displacement, and the fiber bridging characterized by a lower peak stress and a longer critical opening displacement, respectively. The three-linear CZM was implemented in the commercial FE software using a user-subroutine UMAT. Double Cantilever Beam (DCB) tests on the multidirectional composite laminates with 0°/5° and 45°/−45° interfaces conducted in our previous studies are shown to have large-scale fiber bridging in mode I delamination and are used to provide experimental data for calibrating the new CZM. Good agreements between the predicted and tested results can be achieved by adopting this new CZM, demonstrating its applicability on predicting the mode I delamination behavior in composite laminates with the effect of fiber bridging.
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Abstract
Four types of cooling plates with serpent channel structures are established to study the cooling effect of rectangular lithium-ion power battery under different cooling plates. Then, the ...number of serpent bends is analyzed, whether the fillet and pipe wall thickness is set on the cooling performance of the liquid cooling plate. According to the analysis results, a new liquid flow structure form of liquid cooling plate is designed. Numerical simulation results show that the newly designed cooling plate is integrated with the front flow of water and the internal liquid side flow, achieving a cooling effect with the maximum temperature is 309.55K and a pressure drop of 6032.1pa, which has the most effective cooling performance. Under the requirement of controlling reasonable temperature and low-pressure drop, a liquid cooling plate with better performance can be designed by innovatively setting the direction of the water inlet and outlet and the water channel’s internal flow. The above results will provide some ideas for the design of a lithium-ion battery liquid cooling plate.
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%.
Polyimide (PI) is widely used in electronic, electrical and communication fields because of its outstanding mechanical properties, electrical insulation and thermal stability. However, the lower ...thermal conductivity limits their application. Here, PI composite films with high thermal conductivity are obtained by utilizing reactive groups on the carbon nitride nanosheets (CNNS) surface to form covalent bond with PI matrix. The thermal conductivity of CNNS/PI composite films can reach 5.84 W∙m−1∙K−1, which is about 10 times higher than that of pure PI (0.56 W∙m−1∙K−1). This is attributed to the covalent bond between CNNS and PI matrix acting as a “thermal bridge” to connect the discontinuities at the interface, thereby reducing the interfacial thermal resistance between CNNS and PI. The heat transfer mechanism of composite film is further revealed by finite element analysis. This work provides a viable solution to improve the thermal conductivity of PI, allowing for a wide range of potential applications for PI in electronic devices.
Bio-inspired engineering design has drawn considerable attention in the recent years for its great structural and mechanical features. This study aimed to explore the energy absorption ...characteristics of a novel bionic-bamboo tube (BBT) structure subjected to axial crushing. The tubes with six different cross-sectional configurations were devised with inspiration of bamboo microstructure. The effects of rib shape and rib number were analyzed by using the finite element code LS-DYNA. The numerical results indicated that the BBT structures with the rib shape of “X” and the rib number of six exhibited the best crashworthiness. To further improve the energy absorption capabilities of these BBT structures, the multiobjective optimization was employed with respect to design variables of configurational structure, such as the rib angle of the “X” shaped cross-section, center distance and rib thickness. The response surface method (RSM) and multiobjective particle swarm optimization (MOPSO) algorithm were adopted to maximize specific energy absorption (SEA) while minimizing peak crushing force (PCF). The optimization results demonstrated that compared to the baseline design, the SEA value of the optimized BBT structure was further increased by 6.84% without sacrificing in peak crushing force.
•Six kinds of bionic-bamboo thin-walled structures (BBTS) were proposed and their energy absorptions were compared.•BBTS with rib shape of “X” and rib number of six showed the best energy absorption capability.•Rib number, rib thickness, angle of rib and center distance had considerable effects on the energy absorption.•Crashworthiness characteristics of optimized BBTS were superior than that of initial design.
Flax fibres offer performance capabilities comparable to glass fibres, thereby enhancing their potential in the biobased composites industry. However, these fibres have morphological defects ...affecting their mechanical features. In the present work, flax elementary fibres geometries with defects assessed by synchrotron X-ray microtomography were meshed to simulate a tensile test using finite element analysis. For the first time, the distribution of stresses in the vicinity of defects is revealed. The geometrical irregularities at the surface of the fibre and the delamination of cellulose layers within fibre cell wall turned out to concentrate stress up to 7.5 times compared to defect-free regions. These results demonstrate why flax fibres cannot reach their full potential in comparison to what could be expected from a structure mainly constituted from crystalline cellulose microfibrils, and why fracture in a composite is likely to initiate in those defect zones.
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