Search

Highlights To predict the coefficient of thermal expansion (CTE) of carbon fiber/epoxy resin composites with void defects comprehensively and accurately, a comprehensive study is carried out by integrating experiment, analytical model (ANM), and finite element model (FEM). The experiments on composites are conducted combining with Micro‐CT to provide geometric parameters and verification for ANM and FEM. An ANM considering void defects is established based on the Chamis model to investigate the influence of porosity, temperature and the ratio of modulus of the constituents of composites. A FEM is established to verify the ANM and reveal the mechanisms of the influence of void defects. The results show that the proposed ANM has high agreement with FEM and experiment. The longitudinal CTE decreases by 61.94% as the porosity increases from 0% to 20% at 60°C, and the same change of porosity results in a 15.62% decrease at 180°C. The transverse CTE is less susceptible to changes in porosity, showing reductions of 2.32% at 60°C and 3.33% at 180°C. An innovative model is proposed to predict CTE considering void defects. The glass transition temperature Tg of the resin has a significant effect on CTE. Void defects change the homogeneity of the original stress field of the matrix. The reduction of the longitudinal CTE caused by void defects is more significant. [ABSTRACT FROM AUTHOR]

Efficient and accurate calculation of stress overload and stress redistribution near the fiber breakpoint is the basis for simulating the tensile damage evolution of unidirectional fiber reinforced plastic (FRP), and it is also the premise for predicting the tensile-tensile fatigue life. In this study, an efficient finite element (FE) model with a large number of fibers was developed based on the FE method to calculate stress concentration factor (SCF) near multiple breakpoints, and the calculation time only takes 3 min on average. The FE model is used to efficiently calculate multiple breakpoints and the stress distribution near the breakpoint considering the interface debonding. Based on the efficient FE model, an analytical model is developed to calculate the stress overload superposition around multiple breakpoints. In this analytical model, the shear stress distribution near the broken fiber elements is established based on the experiment, and the stress redistribution mechanism near the breakpoint in FRP with random distribution of fibers is established. Moreover, the calculation method of stress overload near multiple break points is established, and the FE method is verified. [ABSTRACT FROM AUTHOR]

• An analytical model is proposed for the semi-parallel stay cables under axial tensile loads. • The friction generated by adjacent steel wires under contact force and relative slip is considered. • The angle between the principal torsion-flexure axes and Frenet–seret axes of each wire is yielded. • The effect of friction on stay cable is clarified according to mechanical performance along axial direction of the wire. A novel analytical model is proposed to evaluate the influence of adjacent wire friction on the mechanical properties of semi-parallel stay cables. This model considers the bending and torsional stiffness of semi-parallel wires and the friction between adjacent contact wires. The finite difference method and nonlinear least squares method are used to solve the angle between the principal torsion-flexure axes and Frenet–Serret axes of the wires numerically, and each wire is solved sequentially according to the equation of the force transmission. The helical radius and angle of all wires after deformation are derived according to the angle, and the problem is iteratively solved until convergence of all wires. The effectiveness of the proposed model is verified via the refined finite element model of a 19-wire stay cable. The proposed method accurately evaluated the mechanical properties of adjacent wire friction on stay cable by analyzing the influence of angle on the semi-parallel wires, which is more conducive to understanding the fretting wear and fatigue behavior of wires and quantifying their damage. [ABSTRACT FROM AUTHOR]

The chip compression ratio is the most important characteristic of various machining processes with chip generation. This characteristic enables the determination of kinetic and other energy loads on the tool and the machined material. This provides an overall evaluation of the machining process and the possibility of its subsequent optimization. This paper presents the results of determining this cutting characteristic by experimental method, analytical calculation, and numerical modeling. For the analytical calculation of the chip compression ratio, an analytical cutting model developed based on the variational principle of the minimum potential energy was used. A finite element model of orthogonal cutting was used for the numerical simulation of the above process characteristic. Experimentally, the chip compression ratio was determined by the ratio of the chip thickness to the cutting depth (undeformed cutting thickness). The chip thickness was determined by direct measurement using chip slices obtained during the cutting process. The Johnson–Cook constitutive equation was used as the machined material model and the Coulomb model was used as the friction model. The generalized parameters' determination of the constitutive equation was performed through a DOE (Design of Experiment) sensitivity analysis. The variation range of these parameters was chosen based on the analysis of the effect of individual parameters of the constitutive equation on the chip compression ratio value. The largest deviations between the experimental and analytically calculated values of the chip compression ratio did not exceed 21%. At the same time, the largest deviations of simulated values of the indicated cutting characteristic and its experimental values did not exceed 20%. When comparing the experimental values of the chip compression ratio with the corresponding calculated and simulated values, the deviations were within 22%. [ABSTRACT FROM AUTHOR]

This paper is focused on a new structural type - sandwich shell, which includes inner and outer shells connected by hoop connectors to achieve composite action; and a functional layer in the middle. Considering that the hoop connectors are not completely rigid, there will be limited slip between the inner and outer shells, which will lead to partial Degree of Composite Action (DCA). Due to the existence of the hoop connectors and shear lag effect, the stress distribution along the width direction of the shell is uneven, which can be described by effective width. Considering all these factors, this paper first develops an analytical model for sandwich shells with different configurations of connectors; and uses finite element analysis results to verify the analytical model. Next, a parametric study is conducted using the analytical model to study the effects of material strength, the ratio of the thickness of the functional layer to the thickness of the single layer shell, and the ratio of the arc length to the width of the sandwich shell on the effective width. It is found that DCA can significantly affect the stress and strain distributions of the sandwich shell. The effective width for 100% DCA can be used as a conservative value to represent those of other DCAs. Finally, a simplified calculation formula, which can be used in practical design, is derived based on the effective width for 100% DCA. [ABSTRACT FROM AUTHOR]

As a new type of braking method, the eddy current brake (ECB) is nowadays widely applied in life and military. The ECB can generate the strong resistance by the magnetic field, and obtaining the accurate magnetic induction distribution is essential in the ECB modeling. This paper proposes an analytical model of a cylinder ECB used in the artillery that operates under the intense impact load. This model takes the axial edge effects into consideration in both static and dynamic conditions. Firstly, this paper introduces the structure and working principle of this ECB. Secondly, a multilayer theory with virtual region is proposed to calculate the magnetic induction distribution considering the end effect. Thirdly, Finite Element Method (FEM) model is established to describe the spatial variation of the magnetic field in different conditions. Finally, the analytical model is compared with the FEM model to prove its validity and predict the working characteristic of the ECB under the intense impact load, the max recoil displacement and speed range both meet design and work requirements. [ABSTRACT FROM AUTHOR]

Permanent magnet synchronous motors (PMSMs) have been widely applied in the fields of electric cars/strucks and industries due to their high torque and efficiency, reliable performance, simple structure and various shapes and sizes. Recently, multi-phase PMSMs with inner and outer configurations have been applied to the above applications. However, the investigation, evaluation and comparison performences of multi-phase PMSM with inner and outer rotor types in previous studies have not been fully presented in both the analytical model and finite element technique. The previous researches mainly have focussed on doing experiments without presenting the detail of design of these machines. In this context, electromagnetic parameters (such as electromagnetic torque, cogging torque, torque ripple, back electromagnetic force, linkage flux) of a six-phase surface mounted PMSM (SPMSM) with inner and outer rotor configurations is proposed via an association of analytic model and finite element method (FEM). The development of the proposed methods is focussed on a 145kW six-phase SPMSM with two distinct rotor structures (inner and outer rotors). [ABSTRACT FROM AUTHOR]

This paper presents a two-dimensional analytical model for brushless double-rotor flux-switching permanent magnet machines (BDRPFSPMM) with yokeless stator recognized as a type of partitioned-structure flux-switching permanent magnet that is an appropriate machine to be employed as the electric motor in industry. The most salient advantages of the proposed machine are low iron loss due to volume of iron in stator and high space of stator slot for winding. The radial and tangential components of the magnetic flux density due to permanent magnets and armature currents in each active domain of the machine, electromagnetic torque, self- and mutual inductance, unbalanced magnetic force (UMF), and local traction are calculated based on the subdomain method. Teethes on both rotor and stator structures are effective on magnetic quantities, so interactions of rotor and stator saliency are considered. The method is general for the magnetic field calculation with any combination of rotor- and stator-pole number. To validate the proposed model, the analytical outputs are compared with those obtained from the finite element method (FEM). [ABSTRACT FROM AUTHOR]

For the rolling process from rectangular blank to profiled ring, there is a lack of simple and rapid prediction method for geometric size. Based on the constant volume principle and the discrete idea from slab method, a rapid prediction model (RPM) describing the exact geometry of ring is established, and a simplified prediction formula for the section shape of profiled ring in the rolling filling process is proposed. This method is used to analyze the rolling process of typical profiled ring, and the results are compared with the rolling experiment, the finite element model (FEM), and the formula model (FM). The results show that this method has higher prediction accuracy than the constant volume formula method and higher calculation efficiency than the finite element method. The rapid prediction method proposed in this paper is of great significance for improving the analytical efficiency of profiled ring rolling. [ABSTRACT FROM AUTHOR]

• The symplectic approach is applied to solve the strip cross section temperature. • The mechanism of residual stress formation in hot strip rolling is studied by fiber rods model. • An analytical model for the coupling of temperature, crown and residual stress is established. • The strip critical exit crown ratio is obtained by using the residual stress analytical model. • Eliminating manifested and latent flatness defects by critical exit crown ratio of strip. Residual stress is introduced during hot-rolled strip production due to various factors, such as temperature distribution, crown change, and metal transverse flow. Excessive residual stress can cause flatness defects in the strip, while insufficient residual stress may result in deformation during subsequent cutting. To explore the mechanism of residual stress formation in hot-rolled strip and how to control it, an analytical model for the coupling of temperature, crown and residual stress is established. Firstly, based on the symplectic space Hamiltonian system, an analytical solution for the strip cross section temperature field in each inter-stand zone is obtained. Then the residual stress analytical model is derived based on the fiber rod model combined with the law of volume invariance, lateral metal flow function and high temperature stress relaxation phenomenon. Meanwhile, to verify the accuracy of the analytical model, a multi field coupled finite element model based on the measured data validation is established. The calculation results of the analytical model are in good agreement with the finite element model. Furthermore, the buckling model of strip in symplectic space Hamiltonian system is derived, and the critical buckling stress of different strip flatness defects is directly calculated. Finally, the residual stress analytical model is combined with critical buckling stress to calculate the critical exit crown ratio to keep the strip flat. [ABSTRACT FROM AUTHOR]

Accurate dynamic modeling is the basis for achieving high-precision motion control of a wheeled wall-climbing robot. In a dynamic model, the magnetic attractive force is one of the important influencing forces. In this study, to quickly obtain the attractive force of the magnetic wheel under different wall structure and attitude, the equivalent magnetic circuit method is combined with an analytical approach to construct attractive force models on the flat wall, the 90° concave corner, and the 90° convex corner, respectively. By establishing the geometric relations of the air gap, the reluctance is calculated to analyze the effects of changes in wall structure and relative attitude. The formula for calculating the attractive force is obtained based on this analysis. The proposed model's accuracy was confirmed by comparing it to finite element analysis (FEA) results. These models enable rapid calculation of the dynamic attractive force, providing a foundation for establishing a high-precision dynamic model for a wheeled wall-climbing robot. [ABSTRACT FROM AUTHOR]

Cogging torque can affect the performance of permanent magnet (PM) homopolar inductor machines (HIMs). In order to find the reduction methods of the PM HIM cogging torque, it is necessary to investigate its production mechanism and analytical model. In this paper, the production mechanism of the PM HIM cogging torque is revealed from the perspective of air‐gap field modulation principle. It is found that the air‐gap permeance of PM HIMs can modulate their air‐gap magneto‐motive force (MMF) and then a large number of modulated air‐gap magnetic fields are generated. These magnetic fields with identical production condition but different rotation speeds or rotation directions can interact with each other, hence the production of the PM HIM cogging torque. By the combination of energy method and air‐gap field modulation principle, the cogging torque analytical model of PM HIMs is derived. Based on the obtained analytical model, the methods for reducing the PM HIM cogging torque are further analyzed. Finally, a 48‐slot/4‐pole (48S4P) PM HIM is designed and exampled. The air‐gap flux density of the 48S4P PM HIM is simulated by three‐dimensional (3‐D) finite element analysis (FEA). Based on the harmonic analysis for the simulated results, the correctness of the proposed cogging torque production mechanism is validated. In addition, a prototype of the 48S4P PM HIM is manufactured. The cogging torque in the prototype is obtained by the analytical model, 3‐D FEA and experiments, respectively. The simulation and measurement results verify the correctness of the cogging torque analytical model. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Micro-newton thrust stands are widely used in thruster ground calibration procedures for a variety of space missions. The conventional analytical model does not consider the gravity-induced extension effect and systematic error in displacement for thrust stands consisting of hanging pendulums based on flexure hinge structures. This paper proposes an improved analytical model of a hanging pendulum for thrust measurement, where an elliptical notched flexure hinge is the key component. A parametric model of the bending stiffness of the flexure hinge is developed. Equally, both the bending stiffness shift under the gravity-induced extension effect and the systematic error in displacement due to the assumed rotational center offset of the hinge are investigated. The presented stiffness equations for elliptical notched hinges can be degenerated into stiffness equations for circular notched as well as leaf-type hinges. The improved model aims to evaluate and highlight the influence of the two considered factors for use in thrust stand parameter design and thrust analysis. A finite element modeling solution is proposed to validate the proposed analytical model. The results show that the proposed model can quantify the hinge bending stiffness shift, which also demonstrates that even a small bending stiffness shift may introduce great uncertainty into the thrust analysis. [ABSTRACT FROM AUTHOR]

In view of the unstable electromagnetic performance of the air gap magnetic field caused by the torque ripple and harmonic interference of a multi-slot and multi-pole low-speed, high-torque permanent magnet synchronous motor, we propose a simplified model of double-layer permanent magnets. The model is divided into an upper and a lower subdomain, with the upper subdomain being an ideal circular ring and the lower subdomain being a segmented sector ring. Moreover, we develop an exact analytical model of the motor that predicts the magnetic field distribution based on Laplace's and Poisson's equations, which is solved using the method of separating variables. Taking a 40p168s low-speed, high-torque permanent magnet synchronous motor as an example, the accuracy of the model is verified by comparison with an ideal circular ring model, a segmented sector ring model, and the finite element method. Based on the proposed simplified model, three combined permanent magnets considering both edge-cutting and polar arc cutting structures are proposed, which are chamfered, rounded, and rectangular combinations. Under the premise of a consistent edge-cutting amount, the electromagnetic characteristics of the three combination types of permanent magnets are compared using the finite element method. The results show that the electromagnetic characteristics of the chamfered combination PM are superior to those of the other two combinations. Finally, a prototype is manufactured and tested to validate the theoretical analysis. [ABSTRACT FROM AUTHOR]

External bonding with fiber-reinforced polymer (FRP) offers a potential solution to mitigate the detrimental effects caused by load impact and corrosion, which can weaken the bond strength of reinforced concrete structures. However, existing models need to be improved in addressing the FRP confinement mechanism and failure modes. As a solution, the proposed model employs stress intensity factor (SIF)-based criteria to determine the internal pressure exerted on the steel-concrete interface during various stages of comprehensive concrete cracking. Critical parameters are evaluated using weight function theory and a finite element model. A bond-slip model is introduced for the FRP-concrete interface and reasonable assumptions on failure plane characteristics. The internal pressure model employed demonstrates that FRP confinement has the ability to generate dual peaks in stress distribution and modify their magnitude as the confinement level increases. The proposed predictive model demonstrates superior performance in failure modes, test methods, and wrap methods for assessing bond strength with FRP confinement. The accuracy of this model is indicated by an integral absolute error (IAE) of 9.6% based on 125 experimental data, surpassing the performance of the other three existing models. Moreover, a new confinement parameter is introduced and validated, showing an upper bound of 0.44 for enhancing FRP bond strength. Additionally, a general expression validating the bond strength model with FRP confinement is established, allowing for the prediction of bond length. [ABSTRACT FROM AUTHOR]

The pole–slot combination is an important factor affecting the cogging and electromagnetic characteristics of a permanent magnet synchronous motor. Taking a 95 kW direct-drive drilling permanent magnet synchronous motor (DPMSM) as an example, this paper presents an analytical model of the motor's magnetic field based on the ideas of segmental discretization and magnetic vector potential, and considers a case in which the stator slot type is a closed slot. The Laplace or Poisson equations of each solution domain are solved using the separation of variables method, and the undetermined coefficients in the general solution are obtained by combining the boundary or interface conditions, thus completing the construction of the analytical model of the motor. The accuracy of this analytical model is verified with the finite element method (FEM). Based on the analytical model, the effects of the different pole–slot combinations on the electromagnetic performance, such as the air-gap flux density, back-EMF, cogging torque, output torque, etc., are investigated, and a reasonable choice of pole–slot combinations is made. The test results of the prototype are basically consistent with the predictions of the analytical model. The analytical model serves as an accurate and efficient calculation tool for the design of DPMSMs. [ABSTRACT FROM AUTHOR]

The paper presents the study and analysis with finite elements of the hook of a hoist, as well as the load capacity of the hook varying the cross-sections. The selected sections were constant over time and then the sizes of two different sections were changed. The hoist hook is modelled using SOLIDWORKS software. Von Mises stress analyses were performed. To validate the stress distribution model for its correctness, he used the theory of curved beams. The obtained results were compared with those determined by analytical calculation and it was found that the deviations are at least 5%. The finite element analysis method can be used for different material types and different loadings. [ABSTRACT FROM AUTHOR]

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• Based on the fiber rods model, the formation mechanism of residual stress caused by temperature and phase transformation is studied. • An analytical model is established to calculate the residual stresses at different run-out table cooling stages. • Based on symplectic space Hamiltonian system, the mathematical relationship between residual stress and flatness is solved directly. • The edge wave defects in strip run-out table cooling process are calculated directly by using the analytical model. The residual stress formed in the run-out table cooling stage of hot-rolled strip has a great influence on flatness and subsequent cutting. Based on the fiber rods model, the formation mechanism of residual stress induced by incompatible deformation caused by temperature and phase transformation is studied in this paper. Meanwhile, the present study makes a first attempt to establishing the analytical model for calculating residual stresses at different run-out table cooling stages. Moreover, in order to further investigate the relationship between residual stress and flatness defects, a strip buckling model is introduced. The traditional buckling equilibrium equation of Lagrange system is introduced into the Hamiltonian system of symplectic space, and the mathematical relationship between residual stress and strip flatness is obtained directly without assuming stress and deflection function. Then the strip flatness is calculated by using this mathematical relationship and residual stress analytical model. Furthermore, to verify the accuracy of the analytical model, a multi-field coupled finite element model based on the validation of the measured data is established. Finally, the distribution of residual stress calculated by the analytical model and the finite element model is basically consistent. The analytical model calculated that the strip would have edge wave defects during run-out table cooling, which is highly consistent with the results of finite element model. [ABSTRACT FROM AUTHOR]

This paper proposes a method to amplify the performance of a flexural-wave-generation system by utilizing the energy-localization characteristics of a phononic crystal (PnC) with a piezoelectric defect and an analytical approach that accelerates the predictions of such wave-generation performance. The proposed analytical model is based on the Euler-Bernoulli beam theory. The proposed analytical approach, inspired by the transfer matrix and S-parameter methods, is used to perform band-structure and time-harmonic analyses. A comparison of the results of the proposed approach with those of the finite element method validates the high predictive capability and time efficiency of the proposed model. A case study is explored; the results demonstrate an almost ten-fold amplification of the velocity amplitudes of flexural waves leaving at a defect-band frequency, compared with a system without the PnC. Moreover, design guidelines for piezoelectric-defect-introduced PnCs are provided by analyzing the changes in wave-generation performance that arise depending on the defect location. [ABSTRACT FROM AUTHOR]

This work assesses the flexural performance of prestressed concrete beams with external carbon fiber-reinforced polymer (CFRP) tendons, focusing on tendon-related variables. A finite element analysis (FEA) method is verified. A numerical parametric analysis of prestressed concrete beams with external CFRP tendons is carried out. Four tendon-related variables are considered, namely, the area, initial prestress, depth and elastic modulus of tendons. The analysis shows that flexural ductility decreases as the tendon area, initial prestress or elastic modulus increases but is insensitive to the tendon depth. The ultimate tendon stress increment (Δσp) is influenced by all of the four variables investigated. JGJ 92-2016 (Chinese technical specification for concrete structures prestressed with unbonded tendons) significantly underestimates Δσp and, hence, is over-conservative for the strength design of these beams. An equation is proposed for calculating Δσp, taking into account all four variables investigated. An analytical model is then developed to estimate the flexural strength (Mu) of prestressed concrete beams with external CFRP tendons. The proposed analytical model shows good agreement with FEA, i.e., the mean discrepancy for Δσp is 0.9% with a standard deviation of 11.1%; and the mean discrepancy for Mu is −1.6% with a standard deviation of 2.1%. [ABSTRACT FROM AUTHOR]

Rock load on lining structures increases over time for tunnels buried in rheological rock, and in addition deterioration of primary lining is common due to its structural characteristics and service environment attack, where these delayed features affect the mechanical response of tunnels. However, accounting for these delayed features in long-term stability assessment of tunnel structures is complex and has not attracted enough attention. In this paper, an analytical approach is proposed for investigating long-term mechanical response of tunnel structures in rheological rock influenced by degradation of primary lining. For this purpose, degradation of primary lining, characterized by decreasing concrete stiffness over time, is quantitatively described by an exponential model. The rheological characteristic of surrounding rock is simulated by the Burgers model. The time-varying solutions for rock deformation and support pressure are obtained by considering the coordinated interaction between surrounding rock and linings, and their correctness is verified by comparing them with numerical results. The results revealed that the pressure imposed on linings due to the rheological behavior of surrounding rock increases over time. As the primary lining degrades, the rheological load is transferred from primary lining to secondary lining, leading to increasing pressure on secondary lining; and a faster degradation rate of primary lining leads to greater pressure on secondary lining. Therefore, the primary lining should not be overlooked in long-term safety assessment of operation tunnels because of its role in bearing and transmitting load. Finally, the tunnel's design and operational maintenance strategy are discussed when the delay effects of surrounding rock and lining are taken into account. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• An analytical model is developed to evaluate thermoelastic damping in laminated microring. • More items are needed to converge when values of ∆ E for the layers are quite different. • The temperature gradient in the circumferential direction has little effect on the TED. • Increasing thickness of metallic coating will increase TED of laminated microring resonators. Predicting thermoelastic damping (TED) is crucial in the design of micro-resonators with high quality factors. Until now, some analytical models have been developed to evaluate the TED effect on microrings which are widely used in many micro-resonators. However, most previous works are limited to microrings with single homogeneous material. This paper develops an analytical model for investigating the TED in the laminated microrings. The temperature fields along the thickness and circumferential directions in the laminated microring are presented using the generalized orthogonal expansion technique. The analytical model for the TED is obtained by computing the dissipated energy and the maximum elastic energy in each layer. The present analytical model for evaluating the TED is validated by comparing with the previously published result and the finite element method (FEM). The effects of the thickness and the property of the metallic layer on the TED characteristics of two- and three-layered microrings are analyzed. The present model can be used to optimize the design of the microring resonators with high quality factors. [ABSTRACT FROM AUTHOR]

To verify the effectiveness of uplift-restricted and slip-permitted (URSP) connectors in alleviating crack formation in the negative-moment region of steel-concrete composite beams (SCCBs) and improve the engineering adaptability of URSP connectors, this paper proposes a modified uplift-restricted and slip-permitted (MURSP) connector. Static load tests and theoretical analysis were conducted on two overhanging beams with MURSP connectors and ordinary studs to analyze the influence of different stud forms on the deflection, crack, and slip of SCCBs in the negative-moment region. Finally, a nonlinear finite element modeling method for MURSP-type steel-concrete composite beams was developed, and a finite element model was established. The results showed that the use of MURSP connectors could effectively alleviate the concrete cracking problem in the negative-moment zone of SCCBs. Compared with the common stud SCCB, the crack load of the MURSP-type SCCB was higher, the maximum crack width was lower, and the crack distribution was more uniform; however, the overall flexural stiffness of the overhanging beam with MURSP connectors was reduced by 3.08%. The interface slip of the overhanging beam with the MURSP connectors increased suddenly in the initial stage of loading, whereas the increase was more gradual in the later stage. The SCCB model established in this study was in good agreement with the results of experimental beams. The finite element analysis results showed that the ordinary stud and MURSP connector exhibited different stress and deformation states in the negative-moment region of SCCBs, and the deformation states changed from bending type to shear type. [ABSTRACT FROM AUTHOR]

The main objective of the paper is to demonstrate the functionality and reliability of a hydrokinetic turbine system -- a submersible electric generator, suitable for very low watercourses. To achieve this goal, it is necessary to design and build a prototype of a hydrokinetic turbine, coupled with an electric generator with excitation made with permanent magnets. This paper presents an analytical model and a finite element numerical model for estimating the electrical parameters of the generator (voltage, current, power, etc.). The two models were compared, and the results were extrapolated, in the analytical model, for several speed values. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Southeast University (English Edition) is the property of Journal of Southeast University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This article presents the process of building a hybrid analytical model (HAM) for surface-mounted permanent-magnet machines. The HAM couples a reluctance network (RN) model in the stator region with a magnetic scalar potential analytical model in the air gap and magnets regions. This hybrid model can deal with the slotting effect with straight teeth, and takes magnetic saturation into account in the stator iron material using the RN model. It is calculated under open-circuit and loaded conditions. The magnetic flux density, flux linkage, back electromotive force (EMF), and torque of the machines are also calculated. This hybrid model is compared with the subdomain method. It is also compared with the finite element method (FEM) both in terms of the size of the matrix that needs to be calculated and in terms of the torque error. We analyzed this method for two surface-mounted permanent-magnet machines, one with a symmetry factor of four and another with a symmetry factor of three. In both cases, HAM reduced the size of the matrix that needed to be solved compared to FEM. In the machine with a symmetry factor of three, when the matrix size of both FEM and HAM was around 1700 × 1700, the torque error of FEM was 2.62% compared to the high-mesh-density FEM simulation, while the torque error of HAM was only 0.17% compared to the same simulation. HAM also had significant advantages over the subdomain method, as it reduced the torque error from 16.8% to 0.08% in the case of high magnetic saturation. The HAM can, hence, play a significant role in the design and optimization of surface-mounted permanent-magnet machines, especially in cases where magnetic saturation is present. [ABSTRACT FROM AUTHOR]

The stability of axially loaded steel columns with compact rectangular hollow sections at elevated temperatures is studied in this paper. The current Eurocode model for checking the buckling resistance of columns in fire was developed on a similar basis to that for ambient conditions. Due to the effect of the complex non-linear behaviour of steel in fire, the standard design model is not always fully appropriate, and certain parameter ranges may give unsafe results. In this work, an analytical method to determine the buckling resistance of steel columns at elevated temperatures is proposed, accounting for variable non-linear stiffness properties which have significant effects on the flexural buckling resistance of steel columns in fire. A finite element model was developed, and an extensive numerical study was performed to explore the effects of different parameters on the behaviours of steel columns at elevated temperatures. The proposed method is validated by comparing the performance with the results of the numerical model. Its improved accuracy with respect to the current Eurocode method is verified. The advantage of the new technique is its computational efficiency, which is valuable in reliability evaluations or data-based design procedures demanding numerous calculation cycles. The potential of the method for probability-based analysis is supported by the format, which enables us to explicitly handle the uncertainties of essential parameters. The proposed framework is suitable for extension to incorporate different material models and section types. [ABSTRACT FROM AUTHOR]

The edge crush test is the most popular laboratory test in the corrugated packaging industry. It measures the edge crush resistance of a sample in the cross-fiber direction (CD), also known as the ECT index. This parameter is widely used for the specification of the board by its producers. It is also utilized in most analytical formulas describing the load capacity of the packaging. On the other hand, the ECT value can be estimated from both analytical and numerical models based on the basic parameters of each constituent paper. Knowing the compressive strength in CD (commonly known as SCT) and the elastic properties of the individual layers, the sample geometry (i.e., the period and height of the corrugated layer), as well as the boundary conditions, the ECT value can be calculated. This is very useful as new boards can be virtually analyzed before being manufactured. In this work, both detailed numerical models based on finite elements (FE) methods and very simple analytical (engineering) models were used for the ECT calculations. All presented models were validated with experimental data. The surprising consistency and high precision of the results obtained with the simplest approach was additionally analyzed in the study. [ABSTRACT FROM AUTHOR]

Surface-mounted permanent magnet (SPM) machines with skewed slots as vehicle drives are widely used. Due to skewed slots, electromagnetic characteristics are modulated by the skew effect. To analyze the skew effect, Maxwell’s equations-based 3-D analytical model is proposed. Based on differences in 3-D air-gap flux density distribution, the mechanism by which the skew effect modulates cogging torque, flux linkage, and back electromotive force (EMF) is investigated. The effectiveness of the theory about the skew effect is verified by both the finite element method (FEM) and the experimental result. [ABSTRACT FROM AUTHOR]

Focusing on the unstable electromagnetic performance of an air gap magnetic field caused by torque ripple and harmonic interference of a multi-slot and multi-pole low-speed high-torque permanent magnet synchronous motor (LHPMSM), an asymmetric stator slot is proposed to improve the comprehensive electromagnetic performance of the motor. Moreover, this paper develops an exact analytical model which predicts the magnetic field distribution based on Laplace's and Poisson's equations. The stator slot asymmetry is introduced into the model and solved by the method of separating variables. Taking a 40p168s LHPMSM as an example, numerical results of the no-load flux density field distributions are obtained by the finite element method (FEM) and employed to validate the analytical model. The influence of stator slot asymmetric structure on electromagnetic characteristics is subsequently analyzed. The results show that, compared with the semi-closed slot model, the asymmetric slot has better torque characteristics, and the electromagnetic characteristics of the motor can be significantly improved by optimizing the stator slot asymmetry. Finally, a prototype is manufactured and tested to validate the theoretical analysis. [ABSTRACT FROM AUTHOR]

Blind bolting technology could access the inside of a closed-section column, which enables to assemble a steel beam to concrete encased CFST (CECFST) column. However, the bulge of steel tube and outer concrete were likely to appear for blind bolted normal CECFST column joints owing to the limited strength of outer concrete. Therefore, this paper adopts UHPC as outer concrete to form a UHPC encased CFST composite column, which aims to avoid the steel tube from being failed for blind bolted joints effectively. Initially, the modular construction process of UHPC encased CFST column blind bolted joints was proposed, in which the assembled joints could be divided into column and beam modular parts during construction. Afterwards, a finite element model was established by ABAQUS considering the complex interactions and material properties to validate the feasible of this modular joint. Detailed failure mechanism and contact behavior between UHPC and steel tube of the joints were discussed, indicating that the UHPC could effectively restrict the bulge of steel tube. Parametric analyses were conducted on typical UHPC encased CFST composite column blind bolted to steel beam joint. Finally, the analytical models of the joint initial stiffness and moment resistance were developed based on the component method considering the dispersal effect of outer UHPC. The comparison results declared that the proposed analytical method provided a reasonable prediction of the initial stiffness and moment resistance. The research results in this paper validated that replacing normal concrete of CECFST by UHPC could avoid column failure when using blind bolted joints and gave a proper design method for the UHPC encased CFST composite column blind bolted to steel beam joint. • Confinement between UHPC and steel tube was analyzed in assembled joints. • Failure mechanism and influence of parameters on the novel joint was discussed. • Design model on initial stiffness and moment resistance was developed. [ABSTRACT FROM AUTHOR]

• The concept of large tooth gap assumption is proposed and used for gear mesh stiffness calculation. • Two new gear mesh stiffness models are proposed based on different tooth gap assumptions. • The proposed rotational model shows a better accordance with the FEM. Tooth broken fault inevitably affects the theoretical tooth contact state, and the meshing force direction is actually not along the theoretical line of action (LOA) when abnormal tooth contact state exists. In previous analytical gear mesh stiffness (GMS) models, theoretical meshing force direction was used whether the tooth broken fault exists or not. Moreover, the tooth gap was assumed to be closed by tooth translational motion, and this kind of GMS model is named as 'the translational model'. To fill this gap, a new GMS model named as 'the rotational model' is proposed in this paper based on the concept of large tooth gap assumption. Different from 'the translational model', the unloaded static transmission error (USTE) is evaluated by the arc length between the initial point and the corresponding contact point along the potential tooth contact path, which can be obtained by the tooth contact analysis (TCA). Further, a loaded tooth contact analysis (LTCA) procedure is developed. The GMS predicted by the proposed theoretical models are compared with the finite element method (FEM) as well as those results reported in the literatures to prove its effectiveness. [ABSTRACT FROM AUTHOR]

Stretch forming with reconfigurable tooling is a flexible manufacturing process that has the potential to produce complex and customized components. A cushion (hyperelastic material) is placed between reconfigurable pinheads and sheet metal to reduce the height of dimples on formed components. Conformability between the cushion and pinhead interface is important in enhancing the accuracy of components. Among various existing cushion types, the component-specific cushion designed in earlier work improved the conformability and accuracy of components. However, considering gaps between neighboring pins after adjusting them to desired height based on component and pinhead surfaces in cushion design can further significantly enhance its effectiveness and is yet to be addressed. In the present work, an analytical model is developed by considering gaps between neighboring pins at every location to determine the conformability through a measure of global shape error (i.e., maximum geometrical deviation) for obtaining a range of base radius of scooped-out patch that further enhances accuracy. To demonstrate the effectiveness of the proposed methodology, finite element analysis of multipoint-stretch forming is performed to form a spherical shape using component-specific cushions designed with and without considering gaps between neighboring pins. Results clearly indicate that the base radius of scooped-out patch between 0.85 and 0.95 times the pinhead radius significantly improved the conformability. The accuracy and surface quality of the component formed using a component-specific cushion designed by considering gaps between neighboring pins enhanced significantly (68% local and 31% global shape errors) compared to one designed without considering gaps between them. [ABSTRACT FROM AUTHOR]

• Analyzing the stress difference of each steel bar and deriving the analytical solution of energy consumption. • Quantifying total energy dissipation of steel bars at three typical impact positions. • Dividing steel bars' total energy and summarizing its changing rules. • Developing two methods for calculating the penetration depth considering impact position. • Establishing and verifying the finite element model for comparison with the analytical model. In the research of projectile penetration into reinforced concrete, the discreteness of penetration depth widely exists in the experiments and empirical formulas, and different impact positions are one of the main reasons for this discreteness. However, the existing theoretical models considering impact position require self-programming methods to solve, and analytical solutions for penetration depth have not been provided. Moreover, existing penetration depth formulas have not dealt with the influence of impact position on penetration depth. To incorporate the influence of the impact position in the penetration depth formulas, this study has investigated different impact positions of the projectile penetration. Herein, the Young formula is used as an example, the projectile penetration process is regarded as a uniformly variable motion based on the constant resistance assumption, two methods are used to obtain the penetration constant resistance, and the energy dissipation of the steel bar at three typical impact positions is theoretically modeled. Finally, analytical solutions for the penetration depth at the three positions are proposed and the mechanism of differences at the three typical impact positions is revealed. In addition, finite element models are established for the three impact positions based on published penetration tests. The penetration depth and steel bar energy consumption of the three impact positions are compared and analyzed, and the analytical model is verified. The results suggest that different impact positions can cause different energy consumption of the steel bar, ultimately leading to varying penetration depth. This analytical model, which fully considers the impact positions of the projectile and the arrangement of the steel bars, can be generalized to any penetration resistance theoretical model or penetration depth calculation formula. It can play an important role in further improving and developing the penetration depth calculation formula, and guiding the design of reinforced concrete protection engineering. [ABSTRACT FROM AUTHOR]

Small wind turbines can generate clean energy in diverse locations, from urban to rural areas, without access to the main grids. This study proposes design optimization of an Axial Flux Permanent Magnet (AFPM) synchronous machine for small-scale portable applications. At first, a fast, accurate and pragmatic hybrid analytical model is proposed for performance prediction of the machine. The proposed model is then used as a basis for direct search optimization with factual constraints and objective functions to improve the machine in terms of efficiency, weight, and convenience of the manufacturing process. 3-Dimensional Time Stepping Finite Element Method (3-DTSFEM) is utilized to validate the accuracy and effectiveness of the proposed model and optimization methodology. Output characteristics of the machine from both analytical model and 3-DTSFEM are compared to each other, thus proving the functionality of the proposed study. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) has inherent mechanical strength inconsistencies when the build orientation changes. To address this issue, theoretical models, including analytical and numerical models, can be developed to predict the material properties of additively manufactured materials. This study develops a systematic finite element (FE)-based multiscale numerical model and simulation process for the polymer acrylonitrile butadiene styrene (ABS). ABS samples are fabricated using fused deposition modelling (FDM) to determine the material properties and mechanical behaviours. For macroscale analysis, good agreement between the numerical and experimental tensile strength of transverse samples proved that the FE model is applicable for applying a reverse engineering method in simulating the uniaxial tension of samples. The FE modelling method shows its capability to consider infill density effects. For mesoscale analysis, two methods are developed. The first method is a representative volume element (RVE)-based numerical model for all longitudinal samples. The second method is analytical and based on the rule of mixtures (ROM). Modified rule of mixtures (MROM) models are also developed, which demonstrate an improvement compared to the original ROM models. The research outcomes of this study can facilitate the AM process of parts in various engineering fields. [ABSTRACT FROM AUTHOR]

This paper presents the overview of the numerical design model of welds in structural steels using finite element shell element. Many researches are emerging in the field of advanced modelling of welds in steel connections by using finite element analysis in order to represent accurate geometry and stiffness of welds. There are several weld modelling techniques used for the computation of structural hot spot stresses in fatigue; oblique shell elements, rigid links and increased thickness techniques. The article intends to eliminate the gaps in knowledge about the numerical modelling of welds using shell elements to compute the direct resistance of the welds in structural steels. This paper focuses on the study of numerical design calculation for the resistance of the welds in steel structures from high‐strength steels. Inclined shell elements are used to represent geometry and the stiffness of the welds during modelling of transverse fillet welds in double lapped joint. Several design standards, and guidelines are widely used to check the resistance of the welds. To verify and validate the results of finite element models, analytical and experiment results from literature are used in the undermatching welding conditions. Based on numerical design calculations, a general approach of inclined shell element is recommended to represent the welds for computation of the direct resistance of the welds in steel structures. [ABSTRACT FROM AUTHOR]

The goal of this study was to explore the self-guided machining mechanism of boring and trepanning association (BTA) deep hole drilling and realize precise control of the machining quality. The motion analysis method was used to analyze the center motion trajectory of the drill during the entrance, and the self-guiding mechanism and hole-forming mechanism of BTA deep hole drilling were revealed. Considering the bending deformation of the drilling tube and the tool structure parameters, according to the elastic-plastic deformation theory and Hertzian contact theory, a novel analytical model of the extrusion contact between the guide pads and the hole wall of the BTA deep hole drilling was established for the theoretical prediction of the extrusion deformation and the machining hole diameter. Combined with the finite element method (FEM) simulation model, the variation law of the contact inclination angle, contact stress, and extrusion deformation of the guide pads and the hole wall with the drilling conditions were studied. The total extrusion deformation between the guide pad and the hole wall was between 10 and 50 μm. The maximum error between the FEM simulation results and the test results was 18.1%, and the maximum error between the analytical model results and the test results was 23.6%. The simulation and experimental results showed that the established extrusion contact model could accurately predict the extrusion deformation of the hole wall and the machining hole diameter. [ABSTRACT FROM AUTHOR]

This article develops a nonlinear analytical model (NAM) for predicting the magnet loss of surface-mounted permanent-magnet (PM) motors considering nonlinearity effect and slotting effect. The analytical expression of vector magnetic potential in the PM region is derived from Hague’s equation for slotless air-gap, and then, it is extended for slotted air-gap based on the conformal mapping method. The PMs, iron nonlinearity, and winding current contributing to the eddy current are all represented by equivalent current in the analytical model. The key of the proposed model is to solve the equivalent current of iron nonlinearity from the improved magnetic circuit model (IMCM) of iron region, where the air flux source is proposed to replace the air reluctance. It is found that the iron saturation can decrease the amplitude of flux density and therefore reduce the magnet loss. Based on the NAM, the magnet loss can be obtained with high accuracy and high efficiency, which is a powerful tool for the optimization of magnet loss in the motor design. The effectiveness of the proposed model is verified by the finite-element method. [ABSTRACT FROM AUTHOR]

A metal bushing ring is an important part of the plate heat exchanger, which plays the role of sealing, and the welding seam formed in the current forming processes shortens the life of the plate heat exchanger. A drawing-flaring process of a metal bushing ring without a welding seam is proposed, which includes deep drawing and multi-flaring processes, and the latter is the process that matters. Considering the uneven thickness after deep drawing, an analytical model is established to predict the stress and strain states, thickness distribution, flaring ratio, and driving force in multi-flaring. The whole process FE model is also established, and its reliability is validated through an experiment. Deformation characteristics, thickness distribution, flaring ratio, and driving force are studied by comparing the results of the experiment, finite element analysis (FEA), and theoretical analysis. The buckling phenomenon easily occurs in 90° flaring, so improvements are proposed to enhance the stability, which can avoid the defects. The results prove that the drawing-flaring process is feasible, and the analytical model is reliable. [ABSTRACT FROM AUTHOR]

To accurately predict the peen forming effectiveness under different parameters, coverage and paths, a regional averaging method is proposed in this paper. The realistic peening stress is estimated based on the average stress of all nodes in a specific area and introduced into the peening area as the initial stress to obtain the resultant shape of the sheet. On the basis of the saturated peening field, an analytical expression is proposed for calculating the average stress considering the interaction between projectiles. And the bending moment is acquired by integrating the stresses on the cross-sectional indentation. Moreover, a series of finite element models are adopted to obtain the accurate average stress. Using a Python script, the finite element models are divided into several regions and the average stress of each region is calculated separately. Through single- and four-shot models, the average stress field around a single shot and the interaction between shots are investigated. And with random peening models, the quantitative relationship of the average stress with respect to the peening intensity and coverage is revealed. In addition, the averaged stresses are introduced to sheet forming models to predict the peen forming effectiveness. Narrow strip experiments are designed under the same peening conditions as that of the sheet forming models, and the simulated values are in good agreement with experimentally measured resultant curvatures. [ABSTRACT FROM AUTHOR]

To facilitate the active magnetic bearing (AMB) design and analysis, an accurate and fast model that considers both rotor eccentricity and the saturation effect is necessary. In this article, a novel hybrid analytical model (HAM) for effective calculation of the magnetic field of the AMB is proposed. Eccentricity and local saturation are considered in the proposed HAM. In the proposed HAM, the stator and rotor are modeled by elementary subdomains (ESDs) and the air-gap is modeled by magnetic equivalent circuit (MEC). Direct coupling between the solutions in the ESD regions with MEC completes the whole model matrices. Compared to the existing literature, the proposed model considers both the rotor eccentricity and material nonlinearity. The effectiveness and accuracy of the proposed HAM are validated by both the finite element model and experimental results. The results show that the proposed HAM can accurately predict the magnetic quantities of the AMB. [ABSTRACT FROM AUTHOR]

A novel cage-secondary permanent magnet (PM) linear eddy current brake (ECB) with wide speed range and its analytical model are presented in this article. Differ from the existed PM ECB, the proposed ECB owns the variable parameters cage-secondary structure. This unique secondary structure can keep braking force at a large constant value from high speed to low speed by changing the secondary parameters in different speed ranges. First, both the structure and working principle of the proposed ECB are given. Then, a new analytical model combined with multilayer theory is proposed, where the saturation of secondary iron teeth and the end effect are considered. Based on the magnetic field distribution result, the characteristics of proposed ECB are analyzed. Third, the accuracy and validity of the analysis results are verified by the finite-element method and prototype experiments. Moreover, based on the genetic algorithm, the optimal secondary parameters are obtained with the objective of maximum braking force at each speed. [ABSTRACT FROM AUTHOR]

A new and efficient analytical optimization methodology for the design of rotor features is developed and used in interior permanent magnet motors (IPM). The analytical methodology is based on an extended winding function theory to include the IPM rotor's primary and secondary reluctance paths and the non-homogeneous airgap of the rotor sculpt features. The shape and placement of the rotor features, derived from the analytical-based optimization process, show the improvement in torque average and torque ripple of the IPM machine at a fraction of computational effort. The analytical optimization results are validated with finite element analysis via an exhaustive search. [ABSTRACT FROM AUTHOR]