Search

The reliability of high-voltage circuit breakers (HVCBs) depends critically on the dynamic characteristics of their hydraulic operating mechanisms (OMs). However, previous analyses have been limited to discrete components due to the lack of models capturing multi-physics couplings. This paper proposes a novel co-simulation approach for hydraulic OMs that enables system-level analysis. Specifically, the hydraulic system is modelled using the lumped parameter method, and the transmission mechanism is modelled via finite element analysis. The subsystem models exchange inputs and outputs through shared memory, realizing coupling without compromising simulation performance. Experiments on a 550 kV HVCB validate that the model accurately captures OM transient responses. The co-simulation framework has diverse capabilities, including predicting dynamics under varied operating parameters and quantifying stress distributions and response evolution patterns. Overall, this paper proposes an advanced multi-physics analysis capability for hydraulic OMs to support reliabilityoriented design and optimization. [ABSTRACT FROM AUTHOR]

Rail grinding with abrasive belt is increasingly applied in daily rail maintenance due to its high efficiency and high quality. The contact between rail and abrasive belt largely determines grinding efficiency and grinding quality, but the influences of grinding process and contact wheel’s parameters on the contact behaviour are obscure. To explore the influences, a finite element model of the wheelrail contact was established. The simulation results showed that the grinding angle significantly affected the shape of contact spot. The contact spot gradually became narrower as the grinding angle increased. Similarly, the reduction of the contact wheel radius significantly increased the contact stress. But when the ratio of the thickness of rubber layer to wheel radius increased above 60 %, it had little effect on the size of contact spot and maximum contact stress. This study provides the basis for the selection of grinding process and contact wheel’s parameters. In the actual grinding process, grinding process and contact wheel should be selected according to grinding requirements. (Received in April 2022, accepted in June 2022. This paper was with the authors 2 weeks for 1 revision.) [ABSTRACT FROM AUTHOR]

With the increase in ambient temperature around the world in summer, the working environment of cable joints is deteriorating. Based on the finite element method, a simulation model for temperature analysis in a 10 kV three-core cable and the joints is established. The temperature distribution is analyzed under different ambient temperatures and different currents. Firstly, the temperature rise experiments are carried out to obtain a steady temperature on the surface of the cable joint, which verifies the accuracy of the simulation model. Then, the relationships between the surface temperature and the current of the high voltage current carrying conductor of the joint under different ambient temperatures are fitted. The ultimate safe current carrying capacity of the joint under the different ambient temperatures can be calculated by using these related functions. The results show that the increase of ambient temperature has little effect on the temperature distribution trend of the high voltage conductor surface of the joint, which also meets this rule on the outer surface of the outer sheath. The relation of the surface temperature on the high voltage conductor of the joint to the current is approximately a quadratic function. When the current amplitude is 480 A and the ambient temperature is 75 ℃, the highest temperatures on the surface of the high-voltage current-carrying conductor and the outer surface of the outer sheath are 1.57 and 1.69 times higher respectively than at an ambient temperature of 30 ℃. When the ambient temperature exceeds 55 ℃, the continuous allowable current carrying capacity specified in the national standard can make the high voltage copper conductor of the joint exceed the maximum permitted operating temperature of 90 ℃. Considering the continuous increase in summer ambient temperature since 2020, the continuous allowable current carrying capacity of the intermediate joint of 10 kV copper conductor three-core cross-linked polyethylene insulated cables in the GB needs to be improved and perfected.

The chain link corrosion model was constructed by the finite element analysis software ABAQUS to evaluate the plain link chain impact under the changing behavior of different corrosion states. The link chain simulation study at different corrosion states was conducted (corrosion depth, area, and density), the curve of stress and energy variation with time was plotted. The stress distribution and related energy variations remained approximately the same at heavy loads. The steady stress of the corrosion chain link, friction dissipation energy, plastic dissipation energy, as well as steady internal energy, and corrosion depth, area, and density are fitted by third-degree polynomial relations. The maximum steady stress occurred at corrosion state III, which already exceeded the yield strength of the link chain below 20°C so that it made easy for the corrosion fracture to occur. This method provided important grounds for the design optimization and lifetime prediction of plain link chains. [ABSTRACT FROM AUTHOR]

To restrain bulging in the upsetting of the larger height-diameter ratio (LHDR) billet, a novel upsetting method named cone end billet upsetting (CEBU) is proposed in this article. This method is featured by prefabricating cone shape at billet ends, and aimed to obtain a smaller rigid deformation zone in forming. The forming characters of a cylinder LHDR billet were analyzed by the commercial finite element software DEFORM. Moreover, virtual orthogonal tests were proceeded to uncover several influence factors such as billet end taper, pressing speed and billet height. The results show that bulging can be effectively restrained in CEBU. In the condition of billet end taper α = 15°, pressing speed υ = 0.5 mm/s, and billet height h = 35 mm, a much smaller bulging can be achieved. The simulated results are in good agreement with experiment which was conducted with polycarbonate samples, and indicate CEBU is a promising method to control bulging in the upsetting of LHDR billet.

In this paper, the open-circuit dc-winding-induced voltage in a wound field switched flux (WFSFs) machines is analyzed. The phenomenon of open-circuit dc-winding-induced voltage is illustrated and the mechanism is explained. Rotor skewing is proposed to reduce the open-circuit dc-winding-induced voltage, and the optimal skewing angle is analytically derived based on the analytically deduced harmonic orders of the open-circuit dc-winding-induced voltage. Finite-element (FE) analyses show that the open-circuit dc-winding-induced voltages in the analyzed 12-stator-pole partitioned stator WFSF machines having 10-, 11-, 13-, and 14-rotor-pole rotors can be effectively reduced by >94%, while the ac-winding phase-fundamental back-EMFs can be maintained by >95%. Twelve/ten-stator/rotor-pole prototypes with skewed and nonskewed rotors are built and tested to verify the analytical and FE results. [ABSTRACT FROM AUTHOR]

In this paper, a fast and effective algorithm is proposed for the reconstruction of complex defect profiles for magnetic flux leakage (MFL) inspection, which is the most widely used non-destructive testing (NDT) technique for tanks and pipelines. A Gauss-Newton optimisation procedure is used to reconstruct the depth profile by optimising the parameters of the analytical model. The space mapping (SM) technique is employed to minimise the misalignment between the 'coarse' analytical model and the 'fine' finite element method (FEM) model. A region growing (RG)-based evaluation method is used to locate defect signals and estimate the opening shape of the defect, which reduces the number of optimisation parameters. To demonstrate the accuracy of the proposed inversion algorithm, the procedure is tested with defects of complex shapes from simulated MFL signals under different degrees of freedom (DOFs). The procedure is also tested using the experimental data of two metal loss defects. In all cases, the proposed algorithm shows good agreement between the actual and the reconstructed defect profiles, with fast convergence speed [ABSTRACT FROM AUTHOR]

In order to increase the torque density of the five-phase machines, the third harmonic is commonly employed. In this paper, the optimal and critical ratios for the third harmonic current injection are analytically derived and validated by finite element (FE) analyses. It is found that the optimal and critical injection ratios along with the torque improvement are dependent on the ratio of the third harmonic back electromotive force to the fundamental one. In order to improve the electromagnetic torque contributed by the third harmonic component, this paper employs unequal tooth to increase both the fundamental and third harmonic winding factors. Meanwhile, the optimal unequal tooth width combination is deduced and demonstrated by the FE method. When the third harmonic current is injected under the same amplitude constraint, the output torque can be improved. When the third harmonic current is injected under the same RMS value constraint, for the ten-slot/eight-pole equal tooth machine, the output torque can barely be increased, whilst for the unequal tooth machine, the output torque can be increased by 2.1%. Finally, the ten-slot/eight-pole machine with unequal teeth is prototyped and tested to prove the analyses. [ABSTRACT FROM PUBLISHER]

This paper proposes a new partitioned stator flux reversal permanent magnet (PM) (PS-FRPM) machine having integer-slot overlapping windings, i.e., the slot number per pole per phase q is an integer, based on the magnetic gearing effect in stator-PM machines. Compared with the existing PS-FRPM machine with fractional-slot nonoverlapping windings, a more sinusoidal armature reaction magnetomotive force can be achieved in the proposed PS-FRPM machine with integer-slot overlapping windings, resulting in lower iron loss and PM loss. Electromagnetic performance of the PS-FRPM machine, which has q = 1 overlapping windings is analyzed and compared with PS-FRPM machine, which has q = 0.5 nonoverlapping windings by finite element (FE) analysis. FE results show that the proposed 24/10/12-outer-stator/rotor/inner-stator-pole PS-FRPM machine with q = 1 overlapping winding exhibits higher fundamental phase back-electromotive force, higher average electromagnetic torque and lower torque ripple, lower loss and higher efficiency, higher self-inductance but lower mutual inductance, higher d-axis inductance, and potential infinite flux-weakening capability compared with the 12/10/12-outer-stator/rotor/inner-stator-pole PS-FRPM machine with q = 0.5 nonoverlapping windings. Both prototype machines with q = 1 overlapping winding and q = 0.5 nonoverlapping windings are built and tested to verify the FE analyzes. [ABSTRACT FROM PUBLISHER]

This paper first investigates the flux-weakening control performance of two types of partitioned stator-switched flux permanent-magnet (PM) (PS-SFPM) machines and then proposes a novel mechanical flux-weakening technique. The PS-SFPM machine topologies, operation principles, and flux-weakening control method are described. In addition, it is shown that by mechanically varying the relative position of two stators of the PS-SFPM machine, the PM flux linkage can also be varied, and hence, it can provide improvement in the speed range and torque capability. The optimal relative mechanical angle is derived to enable the maximum torque capability and reduce or even avoid the flux-weakening current injected by the inverter. The proposed technique is verified by three-dimensional (3-D) finite-element (FE) analyses and experiments on the prototype machines. [ABSTRACT FROM AUTHOR]

In this paper, a double stator (DS) wound field (WF) switched flux (SF) (DS-WFSF) machine is proposed. In the DS-WFSF machine, field and armature windings are separately placed in two different stators. Compared with the conventional WFSF machine with single stator, in which both field and armature windings are located, nonoverlapping concentrated windings and large slot areas can be obtained in the DS-WFSF machine. The proposed DS-WFSF machine exhibits >19% higher torque than the conventional WFSF machine, with both machines having the same space envelope and being globally optimized. The influence of leading design parameters, such as copper loss ratio between the field and armature windings, air-gap diameter, and rotor iron piece thickness and widths, on the average output torque is investigated for the DS-WFSF machines having 12/10, 12/11, 12/13, and 12/14 stator slots/rotor iron pieces. All the analyses are confirmed by both finite element and experimental results. [ABSTRACT FROM AUTHOR]

In this paper, switched flux permanent magnet (SFPM) machines are analyzed from the perspective of the air-gap field harmonics. It is found that the modulation of the salient rotor to PM and armature reaction fields in SFPM machines is similar to that of the iron pieces to those fields in the magnetic gear and magnetically geared machine. The magnetic gearing effect is analyzed in SFPM machines with different stator/rotor pole combinations, winding configurations, and stator lamination segment types by a simple magnetomotive force-permeance model, and validated by finite-element (FE) analysis. Different from fractional-slot surface-mounted PM machines in which the working air-gap field harmonic generates >95% of the average electromagnetic torque, >95% of the average electromagnetic torque in SFPM machines having \boldsymbol p\boldsymbol {s} stator pole pairs and nr rotor poles are contributed by several dominating field harmonics, i.e., rotating ones with \vert kn\boldsymbol {r}\,\pm \, (\textbf {2}\boldsymbol {i}-\textbf {1})\boldsymbol {p}\boldsymbol {s}\vert pole pair ( \boldsymbol k=\textbf 1, \boldsymbol i=\textbf 1, 2, 3 ) and static ones with (2\boldsymbol i-\textbf 1)\boldsymbol p\boldsymbol {s} pole pair ( \boldsymbol i=\textbf 1, 2, 3 ). The FE predicted average static torques in SFPM machines are validated by measurements on prototype machines. [ABSTRACT FROM AUTHOR]

In this manuscript, we describe how the map of high frequency conductivity distribution of an oxide-doped anti-ferromagnetic 200 nm thin film can be obtained from the quality factor (Q) measured by a near-field scanning microwave microscope (NSMM). Finite element analysis (FEA) is employed to simulate the NSMM tipsample interaction and obtain a curve related between the simulated quality factor (Q) and conductivity. The curve is calibrated by a standard Cu thin film with thickness of 200 nm, together with NSMM measured Q of Ag, Au, Fe, Cr and Ti thin films. The experimental conductivity obtained by the NSMM for IrMn thin films with various doped concentrations of Al2O3 is found consistent with conventional voltammetry measurement in the same tendency. That conductivity decreases as the content of doped Al2O3 increases. The results and images obtained demonstrate that NSMM can be employed in thin film analysis for characterization of local electrical properties of materials in a non-destructive manner and for obtaining a map of conductivity distribution on the same film. [ABSTRACT FROM AUTHOR]

According to the relationship between damping, strain and time, the piecewise linear wavelet transform and the piecewise linear short time Fourier transform methods are put forward to identify the nonlinear damping of alloy material. The overall nonlinear property of damping is derived from the piecewise local linearisation. The satisfied results obtained from simulations demonstrate that the methods presented are effective. Usually, damping measured in the non-uniform stress field is only a volumetric average. To overcome this deficiency, a trapezoid specimen with quasi-uniform stress field is developed on the basis of the traditional damping experimental equipment. The damping measurement experiment is carried out. The measurement signal is analysed by the two methods presented. The relation curve of damping versus strain has shown that the damping capacity of the alloy Al-33Zn-6Si increases with the increasing strain. The relationship between damping and strain appears obviously nonlinear. [ABSTRACT FROM AUTHOR]

Abstract: Filament wound pressure vessels have been extensively used in many engineering fields, especially aerospace industry. Vibration-based damage detection methods have the potential to be employed to monitor the health status of the structures based on the fact that damage occurred in a structure would result in changes in its structural dynamic characteristics. However the presence of fluid will affect the dynamic response of this type of vessel structures. Due to the liquid mass decrease during its service, the whole system is considered a time-variant system in terms of its dynamic response even the structure itself remains free of damage, which cause problems for vibration-based damage detection method that utilized dynamic response change to identify damage. Therefore it is critical to understand how the change of the liquid height level influences the dynamic response of the coupled fluid–structure system. This work describes the FEM analysis and an experimental study on the dynamic response of filament wound pressure vessels filled with liquid of different heights and provides the primary information that can be used for vibration-based damage detection. [Copyright &y& Elsevier]

This paper is concerned with partially-observed optimal control problems for fully-coupled forward-backward stochastic systems. The maximum principle is obtained on the assumption that the forward diffusion coefficient does not contain the control variable and the control domain is not necessarily convex. By a classical spike variational method and a filtering technique, the related adjoint processes are characterized as solutions to forward-backward stochastic differential equations in finite-dimensional spaces. Then, our theoretical result is applied to study a partially-observed linear-quadratic optimal control problem for a fully-coupled forward-backward stochastic system and an explicit observable control variable is given. [ABSTRACT FROM AUTHOR]

Based on the minimal energy principle, the shape prediction models of the 0·5 mm pitch, 16 pin quad flat no lead (QFN) package solder joints were developed. The influence of the process parameters including the pad length, the pad width and the stand-off on the solder joint shape of QFN was studied. Utilising the surface coordinate exported from the QFN solder joint shape prediction models, finite element analysis (FEA) models were set up and then the non-linear FEA of the QFN solder joints under thermal cycles was performed by ANSYS. The stress–strain distribution within the solder joints and the maximum strain range of the solder joint were determined. The thermal fatigue life of the QFN solder joint was calculated based on the maximum strain range and the Coffin–Manson equation. The results show that the process parameters influence the QFN solder joint shape distinctly, and the QFN solder joint with different pad lengths, pad widths and stand-offs has various stress–strain distributions and fatigue life. The QFN solder joint with a pad length of 0·7 mm, a pad width of 0·28 mm and a stand-off of 0·125 has a fatigue life of 252 cycles under thermal cycles. [ABSTRACT FROM AUTHOR]

A flake is a crack that is induced by trapped hydrogen within steel. To study its formation mechanism, previous studies mostly focused on the formation process and magnitude of hydrogen pressure in hydrogen traps such as cavities and cracks. However, according to recent studies, the hydrogen leads to the decline of the mechanical properties of steel, which is known as hydrogen embrittlement, is another reason for flake formation. In addition, the phenomenon of stress induced hydrogen uphill diffusion should not be neglected. All of the three behaviors are at work simultaneously. In order to further explore the formation mechanism of flakes in steel, the process of flake initiation and growth were studied with the following three coupling factors: trap hydrogen pressure, hydrogen embrittlement, and stress induced hydrogen re-distribution. The analysis model was established using the finite element method, and a crack whose radius is 0.5 mm was set in its center. The cohesive method and Bilinear Traction Separate Law (BTSL) were used to address the coupling effect. The results show that trap hydrogen pressure is the main driving force for flake formation. After the high hydrogen pressure was generated around the trap, a stress field formed. In addition, the trap is the center of stress concentration. Then, hydrogen is concentrated in a distribution around this trap, and most of the steel mechanical properties are reduced. The trap size is a key factor for defining the critical hydrogen content for flake formation and propagation. However, when the trap size exceeds the specified value, the critical hydrogen content does not change any more. As for the crack whose radius is 0.5 mm, the critical hydrogen content of Cr5VMo steel is 2.2 ppm, which is much closer to the maximum safe hydrogen concentration of 2.0 ppm used in China. The work presented in this article increases our understanding of flake formation and propagation mechanisms in steel.

The effect of a non-uniform bondline within a two-layer ultrasonic transducer is investigated using finite element analysis. The predicted results are compared with measured data and good agreement is reported. [ABSTRACT FROM AUTHOR]