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The “essential work of fracture” (EWF) method is applied to various machine-made papers. The deforming and fracturing processes of the paper samples during testing is analyzed by means of the thermographic observation. Plastic deformation zone appears in three ways when deep double edge notched tension specimens are strained under in-plane stress: i.e. 1. type (i)--appearing through whole the ligament in a vague manner and developing into a circular (or oval) zone even before or at the maximum load point; 2. type (ii)--appearing from notch tip and amalgamating into a circular (or oval) zone after the maximum load point; and 3. type (iii)--appearing from notch tip and not amalgamating into a circular (or oval) zone until the sheet failure. Specimens with small ligament length (L) are likely to belong to type (i), while those with large L to type (ii) & (iii). Among these three types, type (i) fulfills the original assumption of the EWF method best in terms of the complete ligament yielding before crack initiation. Thus the specific essential work of fracture determined using the linear relation of type (i) should be correct, although the estimated work is a little smaller than that from the linear relation of type (ii) & (iii). [ABSTRACT FROM AUTHOR]

Copyright of Materials Science / Medziagotyra is the property of Kaunas University of Technology, represented by Prof. Rymantas Jonas Kazys 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 paper presents a comprehensive study on optimizing wind farm efficiency by controlling wake effects using the WFSim dynamic simulation model. Focusing on five key factors—yaw wind turbine position, yaw angle, wind farm spacing, longitudinal wind turbine spacing, and yaw rate—we qualitatively analyze their individual and combined impact on the wind farm's wake behavior and mechanical load. Through a quantitative approach using the orthogonal test method, we assess each factor's influence on the farm's overall power output. The findings prioritize the following factors in terms of their effect on power output: yaw wind turbine position, yaw angle, wind farm spacing, longitudinal spacing, and yaw rate. Most significantly, this study identifies optimal working conditions for maximizing the wind farm's average power output. These conditions include a wind turbine longitudinal spacing of 7.0D, a wind farm spacing of 15.0D, a yaw angle of 30°, and a yaw rate of 0.0122 rad/s, with the first and second rows of turbines in a yaw state. Under these optimized conditions, the wind farm's average power output is enhanced to 35.19 MW, marking an increase of 2.86 MW compared to the farm's original configuration. Additionally, this paper offers an analysis of wake deflection under these optimal conditions, providing valuable insights for the design and management of more efficient wind farms. [ABSTRACT FROM AUTHOR]

High-performance structural materials (HPSMs) are needed for the successful and safe design of fission and fusion reactors. Their operation is associated with unprecedented fluxes of high-energy neutrons and thermomechanical loadings. In fission reactors, HPSMs are used, e.g., for fuel claddings, core internal structural components and reactor pressure vessels. Even stronger requirements are expected for fourth-generation supercritical water fission reactors, with a particular focus on the HPSM's corrosion resistance. The first wall and blanket structural materials in fusion reactors are subjected not only to high energy neutron irradiation, but also to strong mechanical, heat and electromagnetic loadings. This paper presents a historical and state-of-the-art summary focused on the properties and application potential of irradiation-resistant alloys predominantly strengthened by an oxide dispersion. These alloys are categorized according to their matrix as ferritic, ferritic–martensitic and austenitic. Low void swelling, high-temperature He embrittlement, thermal and irradiation hardening and creep are typical phenomena most usually studied in ferritic and ferritic martensitic oxide dispersion strengthened (ODS) alloys. In contrast, austenitic ODS alloys exhibit an increased corrosion and oxidation resistance and a higher creep resistance at elevated temperatures. This is why the advantages and drawbacks of each matrix-type ODS are discussed in this paper. [ABSTRACT FROM AUTHOR]

Copyright of FME Transactions is the property of University of Belgrade, Faculty of Mechanical Engineering 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.)

The paper is focused on analysis of limit states and actual behaviour of the great size fibre cement boards that are produced without autoclaving. In this paper the basic information on the testing of the fibre cement boards is summarized, but its main goal is the utilization of acquired specification and data for the elaboration of backgrounds for direct determining of the defined load carrying capacity of boards for basic cases of loading, span and support conditions. The elaborated solutions and results follow the contemporary approach of the structural design method and reliability verification based on the concept of limit state design using the partial safety factors. [ABSTRACT FROM AUTHOR]

Magnetostrictive transducer, as a kind of high-efficiency transducer, has a broad application in the field of energy harvesting and sensor. However, the voltage generating performance of the transducer limits its application. This paper will endeavor to quantify the load-induced voltage of magnetostrictive transducer by developing a holistic theoretical model and deriving the corresponding analytical solution. On this basis, this paper proposed the concept of voltage sensitivity in transducer optimization, which could quantitatively analyze the normalized voltage generated by a unit excitation. Based on the theoretical simulation and experimental validation, the voltage sensitivities of magnetostrictive transducer under different mechanical loads are investigated. The parametric analysis will be conducted to further optimize the transducer structure to enhance its open-circuit and load voltage. The works of this paper could be instructive to guide magnetostrictive transducer design in sensing and energy harvesting applications. [ABSTRACT FROM AUTHOR]

The mechanical properties of deep rock masses are significantly influenced by temperature and other factors. The effect of temperature on the strength of deep rock masses will pose a serious challenge to deep resource exploitation and engineering construction. In this paper, the thermal-mechanical coupling calculation model is established by particle flow code (PFC2D) to study the uniaxial compression response of rock masses with microcracks after temperature load. The strength of failure, microcracks, and strain was analyzed. The results show that: (i) When the soft rock thickness ratio Hs/H < 0.5, the displacement caused by the applied temperature is concentrated at the structural plane, and the contact force is concentrated at the end of the initial microcrack. When Hs/H ≥ 0.5, the displacement caused by the applied temperature is concentrated on both sides of the initial microcrack, and the contact force is concentrated in the hard rock area. (ii) The number of microcracks decreases with the increase of soft rock thickness under different working conditions. When the soft rock thickness ratio Hs/H < 0.5, the relationship curve between the number of microcracks and the vertical strain shows two stages of change. When Hs/H ≥ 0.5, the relationship curve between the number of cracks and the vertical strain changes shows three stages of change. (iii) When the soft rock thickness ratio Hs/H < 0.5, the failure strength decreases with the increase of soft rock thickness ratio at T = 100°C and 200°C. When T = 300°C and 400°C, the failure strength decreased first and then increased. When Hs/H ≥ 0.5, the failure strength increases with the increase of soft rock thickness at T = 200°C, 300°C, and 400°C. At T = 100°C, the failure strength decreases with the increase of soft rock thickness. [ABSTRACT FROM AUTHOR]

The paper proposes a spectral decomposition–based approach for implementing a multisurface coupled damage–plasticity model for concrete subjected to fire. The multisurface approach enables distinct flow rules to be used for plastic flow in compression and tension. The spectral decomposition–based procedure enables, for general multiaxial loading, the Jacobian for the return mapping algorithm to be determined analytically without the need for finite difference approximations or additional nested iterations. The proposed approach, developed in the context of a general multisurface plasticity model subject to the small strain assumption, is specialized to the case of a combined Drucker-Prager and Rankine yield surface, and can account for situations where the eigenvalues of the stress tensor are degenerate. It is verified by solving finite element models for concrete structural components subjected to high temperature under a wide variety of mechanical loads. The simulation results, obtained using a sequentially coupled approach, are found to closely match established experimental results. [ABSTRACT FROM AUTHOR]

This paper develops a novel set of displacement temperature potential functions to solve the thermoelastodynamic problems in functionally graded transversely isotropic media subjected to thermal source. For this purpose, three-dimensional heat and wave equations are considered to obtain the displacement temperature equations of motion for functionally graded materials. In the present study, a systematic method is used to decouple the elasticity and heat equations. Hence one sixth-order differential equation and two second-order differential equations are obtained. Completeness of the solution is proved using a retarded logarithmic Newtonian potential function for functionally graded transversely isotropic domain. To verify the obtained solution, in a simpler case, potential functions are generated for homogeneous transversely isotropic media that coincide with respective equations. Presented potential functions can be used to solve the problems in various media like infinite and semi-infinite space, beams and columns, plates, shells, etc., with arbitrary boundary conditions and subjected to arbitrary mechanical and thermal loads. [ABSTRACT FROM AUTHOR]

Service loads repeatedly stress components on a regular basis and lead to fatigue damage in the material. In the case of components made of short fibre-reinforced thermoplastics, which are also crash-relevant in addition to only bearing service loads, however, a significant deterioration in mechanical properties can be observed after fatigue damage has been introduced. This is where the approach presented in this paper comes in: in order to enable a realistic simulation of such components in their used conditions, the material data are assigned depending on previously determined damage. The approach, which combines the domains of highly dynamic and cyclic experiments as well as different types of numerical simulations, is tested for its performance in the present paper. For this purpose, component tests are carried out on cross-rib beams, which serve to validate the method. The novelty and uniqueness of this paper lies in the linking of fatigue life and crashworthiness considerations for short fibre-reinforced thermoplastics, which, in this case, is raised to a new level by considering the component level for the first time. [ABSTRACT FROM AUTHOR]

This paper develops a mathematical framework that aims to control the temperature and rotational speed in the activation process of a gas turbine in an optimal way. These controls influence the deformation and the stress in the component due to centripetal loads and transient thermal stress. An optimal control problem is formulated as the minimization of maximal von Mises stress over a given time and over the whole component. To find a solution for this, we need to solve the linear thermoelasticity and the heat equations using the finite element method. The results for the optimal control as functions of the rotation speed and external gas temperature over time are computed by sequential quadratic programming, where gradients are computed using finite differences. The overall outcome reveals a significant reduction of approximately 10%, from 830 N/mm² to 750 N/mm², in von Mises stress by controlling two parameters, along with the temporal separation of physical control phenomena. [ABSTRACT FROM AUTHOR]

Sandwich structures are widely used in various fields. Curved sandwich structures have attracted the attention of researchers owing to their superior stiffness and strength. With the application of the structures in engineering, it is required that the structures can not only meet the needs of mechanical loads but also can cope with thermal, acoustic, optical, and electrical loads. Sound insulation is one of the most common problems in the fields of aerospace, transportation, and architecture, so it is imperative to research new structures with good mechanical and acoustic properties. In this paper, a composite structure which is coupled with curve shell sandwich structure and acoustic metamaterials is proposed to obtain good mechanical and acoustic properties. Based on the harmonic expansion method and principle of virtual work, the theoretical model is established and the sound transmission loss (STL) performance is studied. Then, the effects of the geometry of the structure and material parameters on the STL of the structure are discussed. [ABSTRACT FROM AUTHOR]

Deep shale gas reservoirs have geological characteristics of high temperature, high pressure, high stress, and inferior ability to pass through fluids. The multi-stage fractured horizontal well is the key to exploiting the deep shale gas reservoir. However, during the production process, the effectiveness of the hydraulic fracture network decreases with the closure of fractures, which accelerates the decline of shale gas production. In this paper, we addressed the problems of unclear fracture closure mechanisms and low accuracy of shale gas production prediction during deep shale gas production. Then we established the fluidesolideheat coupled model coupling the deformation and fluid flow among the fracture surface, proppant and the shale matrix. When the fluidesolideheat coupled model was applied to the fracture network, it was well solved by our numerical method named discontinuous discrete fracture method. Compared with the conventional discrete fracture method, the discontinuous discrete fracture method can describe the three-dimensional morphology of the fracture while considering the effect of the change of fracture surface permeation coefficient on the coupled fractureematrix flow and describing the displacement discontinuity across the fracture. Numerical simulations revealed that the degree of fracture closure increases as the production time proceeds, and the degree of closure of the secondary fractures is higher than that of the primary fractures. Shale creep and proppant embedment both increase the degree of fracture closure. The reduction in fracture surface permeability due to proppant embedment reduces the rate of fluid transfer between matrix and fracture, which has often been overlooked in the past. However, it significantly impacts shale gas production, with calculations showing a 24.7% cumulative three-year yield reduction. This study is helpful to understand the mechanism of hydraulic fracture closure. Therefore, it provides the theoretical guidance for maintaining the long-term effectiveness of hydraulic fractures. [ABSTRACT FROM AUTHOR]

Induction motors are one of the most used machines because they provide the necessary traction force for many industrial applications. Their easy operation, installation, maintenance, and reliability make them preferred over other electrical motors. Mechanical and electrical failures, as with other machines, can appear at any stage of their service life, making the stator intern-turn short-circuit fault (ITSC) stand out. Hence, its detection is necessary in order to extend and save useful life, avoiding a breakdown and unprogrammed maintenance processes as well as, in the worst circumstances, a total loss of the machine. Nonetheless, the challenge lies in detecting this type of fault, which has made the analysis and diagnosis processes easier. Such is the case with convolutional neural networks (CNNs), which facilitate the development of methodologies for pattern recognition in several areas of knowledge. Unfortunately, these techniques require a large amount of data for an adequate training process, which is not always available. In this sense, this paper presents a new methodology for the detection of incipient ITSC faults employing a modified cumulative distribution function (CDF) of the current stator signal. Then, these are converted to images and fed into a fast and compact CNN model, trained with a small data set, reaching up to 99.16% accuracy for seven conditions (0, 5, 10, 15, 20, 30, and 40 short-circuited turns) and four mechanical load conditions. [ABSTRACT FROM AUTHOR]

Understanding the role that settlement can have on the base resistance of piles is a crucial matter in the design and safety control of deep foundations under various buildings and infrastructure, especially for long to super-long piles (60–90 m length) in soft soil. This paper presents a novel assessment of this issue by applying explainable machine learning (ML) techniques to a robust database (1131 datapoints) of fully instrumented pile tests across 37 real-life projects in the Mekong Delta. The analysis of data based on conventional methods shows distinct responses of long piles to rising settlement, as compared to short piles. The base resistance can rapidly develop at a small settlement threshold (0.015–0.03% of pile's length) and contribute up to 50–55% of the total bearing capacity in short piles, but it slowly rises over a wide range of settlement to only 20–25% in long piles due to considerable loss of settlement impact over the depth. Furthermore, by leveraging the advantages of ML methods, the results significantly enhance our understanding of the settlement–base resistance relationship through explainable computations. The ML-based prediction method is compared with popular practice codes for pile foundations, further attesting to the high accuracy and reliability of the newly established model. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to propose a new control approach to be applied to a variable rotor speed wind turbine at a low wind velocity zone. The aim is to reduce dynamic mechanical loads and optimize energy production by acting on the generator torque through a new hybrid adaptive controller. This combines two well-known nonlinear methods: nonlinear control based on Radial Basis Function Neural Networks used to estimate the nonlinear part of the wind turbine system and Integral Sliding Mode Control to tackle system uncertainties. Lyapunov’s approach has been applied to assess the stability of this new controller. Then, simulations were carried out using the Matlab/Simulink software package. The obtained results demonstrated the superior performance of the hybrid controller compared to each controller taken alone. [ABSTRACT FROM AUTHOR]

In this paper, a comprehensive study of the mechanical properties of selective laser sintered polyamide components is presented, for various different process parameters as well as environmental testing conditions. For the optimization of the static and dynamic mechanical load behavior, different process parameters, e.g., laser power, scan speed, and build temperature, were varied, defining an optimal parameter combination. First, the influence of the different process parameters was tested, leading to a constant energy density for different combinations. Due to similarities in mechanical load behavior, the energy density was identified as a decisive factor, mostly independent of the input parameters. Thus, secondly, the energy density was varied by the different parameters, exhibiting large differences for all levels of fatigue behavior. An optimal parameter combination of 18 W for the laser power and a scan speed of 2666 mm/s was determined, as a higher energy density led to the best results in static and dynamic testing. According to this, the variation in build temperature was investigated, leading to improvements in tensile strength and fatigue strength at higher build temperatures. Furthermore, different ambient temperatures during testing were evaluated, as the temperature-dependent behavior of polymers is of high importance for industrial applications. An increased ambient temperature as well as active cooling during testing was examined, having a significant impact on the high cycle fatigue regime and on the endurance limit. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive approach aimed at developing a coupled process-structure simulation that integrates anisotropic and elastoplastic material behavior for plastic components manufactured through Fused Filament Fabrication (FFF) 3D printing. The simulation incorporates material orientation considerations, linking the process simulation with structural simulation. Subsequently, stress and strain values from the simulations are compared with the test results. Moreover, the fracture behavior of components manufactured in this way is also taken into account in relation to material orientation. The executed simulations have yielded successful outcomes, affirming the efficacy of the anisotropic and elastoplastic simulation across all strand orientations. Special attention is paid to the application of the method. Here, the simulation method introduced in this contribution with the approaches for describing the material behavior under mechanical load can be used in the future in the dimensioning of FFF manufactured plastic components to predict the deformation behavior and failure, especially under consideration of a well economic and efficient virtual product development. [ABSTRACT FROM AUTHOR]

In this paper, a new functionally graded material (FGM) porous sandwich plate analysis model considering pores with only four variables is proposed. It is applied to the nonlinear bending of two different types of FGM porous sandwich plates under mechanical loading, and the bending of two different types of FGM porous sandwich plates is compared. The governing equations are obtained through the principle of virtual work. The simple supported FGM porous sandwich plates are solved using the Navier method. The obtained numerical results are compared with the results in the literature to verify the accuracy of the theory in this paper. Finally, the effects of volume fraction index, porosity, layer thickness ratio, side-thickness ratio and symmetry on the mechanical bending properties of FGM porous sandwich plates are studied in detail. By comparing the bending characteristics of two types of FGM porous sandwich plates under different influencing factors, it is found that the bending characteristics of different FGM porous sandwich plate types are also very different. This has great guiding significance for the design of FGM porous sandwich plates. [ABSTRACT FROM AUTHOR]

This paper is concerned with electric–acoustic/acoustic–electric conversions of thin-wafer piezoelectric transducers polarized in the thickness direction. By introducing two mechanical components with frequency-dependent values, i.e., radiation resistance and radiation mass, into the equivalent circuit of the thin-wafer piezoelectric transducer, we established a frequency-dependent dynamic mechanic-electric equivalent network with four terminals for an arbitrary given frequency, an enhancement from the conventional circuit networks. We derived the analytic expressions of its electric–acoustic and acoustic–electric conversion impulse responses using the four-terminal equivalent circuit to replace the traditional six-terminal equivalent circuit for a thin-wafer transducer with harmonic vibrational motion. For multifrequency electrical/acoustic signals acting on the transducer, we established parallel electric–acoustic/acoustic–electric conversion transmission networks. These two transmission network models have simple structures and clear physical and mathematical descriptions of thin-wafer transducers for electric–acoustic/acoustic–electric conversion when excited by a multifrequency electric/acoustic signal wavelet. The calculated results showed that the transducer's center frequency shift relates to its mechanical load and vibration state. The method reported in this paper can be applied to conventional-sized and small-sized piezoelectric transducers with universal applicability. [ABSTRACT FROM AUTHOR]

In recent years, a lot of studies were performed on the mechanics of beams. One of the most important aspects of the computations regarding these problems are the stresses and deformations caused by combined mechanical and thermal loads. This paper deals with the determination of the deformation of homogeneous isotropic linearly elastic beams under the action of axial load and thermal loading. In our problem prismatic a beam is considered, which is subjected to combined thermal and mechanical loads, and our aim is to present the analytical solution to this problem when the temperature field is a specific linear function of the cross sectional coordinates. The applied mechanical load consists of an axial load and bending moment applied them at the end cross sections of the considered prismatic beam. The thermal loading is obtained from a temperature field which is a linear function of the cross–sectional coordinates. [ABSTRACT FROM AUTHOR]

The nonlinear buckling response of laminated composite cylindrical shells reinforced with graphene nanoplatelets (GNPs) is studied in this paper. The functionally graded (FG) shell reinforced by GNPs is analytically studied under external pressure and uniform temperature rise loadings. It is also assumed that the GNP-reinforced laminated composite shell is in contact with an elastic foundation. Various types of profiles are employed for the GNP distribution patterns in the shell thickness including 10 nanocomposite layers. The nonlinear strain-displacement relations of the shallow cylindrical panel are established utilizing the third-order shear deformation shell theory. Governing equilibrium equations of the laminated GNP-reinforced composite shell are formulated employing the principle of virtual displacement. The coupled system of nonlinear differential equations is solved analytically for the hinged–hinged and fixed–fixed boundaries of the shell using a perturbation-based technique. Correctness of presented formulations and obtained solutions is proved by comparisons with results from previous studies for an isotropic cylindrical shell. Novel numerical results reveal that the material properties, geometrical characteristics and load parameters significantly affect on the buckling behavior of laminated composite cylindrical shells. [ABSTRACT FROM AUTHOR]

In this paper, a two-dimensional (2D) thermo-hydro-mechanical dynamic (THMD) coupling analysis in the presence of a half-space medium is studied using Ezzat's fractional order generalized theory of thermoelasticity. Using normal mode analysis (NMA), the influence of the anisotropy of the thermal conduction coefficient, fractional derivatives, and frequency on the THMD response of anisotropy, fully saturated, and poroelastic subgrade is then analyzed with a time-harmonic load including mechanical load and thermal source subjected to the surface. The general relationships among the dimensionless physical variables such as the vertical displacement, excess pore water pressure, vertical stress, and temperature distribution are graphically illustrated. The NMA method does not require the integration and inverse transformation, increases the decoupling speed, and eliminates the limitation of numerical inverse transformation. The obtained results can guide the geotechnical engineering construction according to different values of load frequency, fractional order coefficient, and anisotropy of thermal conduction coefficient. This improves the subgrade stability and enriches the theoretical studies on thermo-hydro-mechanical coupling. [ABSTRACT FROM AUTHOR]

Metamaterials have been a hot topic over the past 2 decades, involving scientific research directions in materials, engineering, and physics. Among them, programmable mechanical metamaterials are an emerging class of metamaterials that offer intelligent programming and control of diverse mechanical properties, such as stiffness, damping, thermal expansion, and shape memory behavior. Meanwhile, it can be rationally designed to have specific geometric architectures and programming strategies in response to different types of external stimuli, such as temperature, electric and magnetic fields, and mechanical loads. These intelligent mechanical properties have a wide range of potential applications due to their uniqueness and controllability, including soft robotics, adaptive structures, and wearable devices. Thus, the programming strategies to achieve them are particularly critical. Combined with related programmable thinking concepts, this paper briefly reviews programming strategies for programmable mechanical metamaterials, including geometric, structural, and external driving force programming. Meanwhile, this paper presents the principles of programming strategies classified according to different programmable mechanical properties (e.g., programmable stiffness, deformation, multistability) and looks ahead to the challenges and opportunities for future research. [ABSTRACT FROM AUTHOR]

Interior permanent magnet synchronous motors (IPMSMs) are extensively used as traction motors today because of their exceptional torque, power density, and wide, constant power operating range. Under real-world usage, an IPMSM rotor undergoes varying electromagnetic, thermal, and mechanical loads. Under such conditions, fatigue life-based design criteria should be used over stress-based design criteria to ensure the structural integrity of the rotor. Moreover, the driving dynamics can change the rotor temperature continuously, which affects the electromagnetic, mechanical, and fatigue properties of the rotor material. This paper proposes a robust thermomechanical rotor fatigue simulation workflow considering significant loads acting on an IPMSM rotor and the temperature variation throughout a drive cycle. It discusses an accelerated fatigue life estimation approach based on the peak valley extraction method to reduce the simulation time significantly for the stress and fatigue analysis. Then, it presents a method for a stress-life curve generation for variable loading. It also presents a sensitivity study with a median S-N curve, and a 90% reliability and 95% confidence (R90C95) S-N curve. [ABSTRACT FROM AUTHOR]

Mechanical load is one of the main determinants of cardiac structure and function. Mechanical load is studied in vitro using cardiac preparations together with loading protocols (e.g., auxotonic, isometric). However, such studies are often limited by reductionist models and poorly simulated mechanical load profiles. This hinders the physiological relevance of findings. Living myocardial slices have been used to study load in vitro. Living myocardial slices (LMS) are 300‐μm‐thick intact organotypic preparations obtained from explanted animal or human hearts. They have preserved cellular populations and the functional, structural, metabolic and molecular profile of the tissue from which they are prepared. Using a three‐element Windkessel (3EWK) model we previously showed that LMSs can be cultured while performing cardiac work loops with different preload and afterload. Under such conditions, LMSs remodel as a function of the mechanical load applied to them (physiological load, pressure or volume overload). These studies were conducted in commercially available length actuators that had to be extensively modified for culture experiments. In this paper, we demonstrate the design, development and validation of a novel device, MyoLoop. MyoLoop is a bioreactor that can pace, thermoregulate, acquire and process data, and chronically load LMSs and other cardiac tissues in vitro. In MyoLoop, load is parametrised using a 3EWK model, which can be used to recreate physiological and pathological work loops and the remodelling response to these. We believe MyoLoop is the next frontier in basic cardiovascular research enabling reductionist but physiologically relevant in vitro mechanical studies. What is the central question of this study?Can cardiac tissues be cultured under conditions that do not simulate the mechanical load the heart is exposed to in vivo?What is the main finding and its importance?A culture bioreactor was developed that can keep living heart tissue alive in vitro under continuous electromechanical stimulation. The device, MyoLoop, simulates the cardiac cycle on a beating slice during culture, recreating the in vivo workload of the heart in vitro. MyoLoop is a novel translational platform for cardiac studies. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the interface efficiency of Carbon Fiber Reinforced Polymers (CFRP) adhesively bonded on concrete, a commonly used retrofitting measure applied for enhancing the deformability and strength of decaying structures or existing ones with low capacity. The efficiency quantification is expressed with the Interface Capacity Index (IC). The index correlates the thickness and strength of each layer of the strengthening system and accounts for the transferred loads (ICL) and the strain distribution that causes the failure propagation on the concrete substrate (ICfp). The investigation focuses on different CFRP strengthening schemes (laminated fabrics, prefabricated plates, Near Surface Mounted bars-NSM) applied to concrete substrates using different adhesive layers. Two cases were studied for different levels of concrete's integrity: (a) healthy and (b) containing corrosion products. The experimental results were used to calibrate the numerical models and to evaluate the effects of different strengthening strategies. The results show the tendency of the strengthening systems to shift the interface performance from fully elastic to non-linear. Further, the quantification of the efficiency of retrofitting can be addressed by accounting for the mechanical and geometrical properties at the interface level, representing different failure modes and integration levels. [ABSTRACT FROM AUTHOR]

Due to physical limitations and safety requirements, the rate and amplitude of change in wind turbines' pitch angle are limited, which will bring integral saturation problems to the control system. This leads to the deterioration of the pitch control system's performance or even an instability problem. This paper designs an anti-windup robust pitch angle control strategy to deal with pitch rate constraint issue to enhance the safety of the control system. First, to facilitate controller design, a filtered tracking-error technique is employed to transform the nonaffine form into an affine one. Subsequently, a feedback robust controller based on an uncertainty and disturbance estimator (UDE) is developed to handle the model's uncertainty and external disturbances. To address the issue of integral saturation in the pitch system and guarantee its safety, an elliptical bounded constraint is integrated into the designed UDE strategy. This bounded UDE controller can improve the stability of power generation quality, reducing the mechanical loads on components. Finally, the effectiveness of the proposed scheme is verified on the Wind Turbine Blockset platform in Matlab/Simulink. It can achieve better performance than traditional methods. [ABSTRACT FROM AUTHOR]

For the project of pipe jacking in cohesionless soil, it is key to determine the vertical load on jacked pipe so as to predict the jacking force accurately. In this paper, a new parabolic soil arching model was proposed to calculate the vertical load on jacked pipe. This proposed analytical model was composed of parabolic soil arching zone, parabola-typed collapse zone and friction arch zone. Combined with existing literature, the key parameters (i.e., height of parabolic soil arching, horizontal pressure coefficient and width and height of friction arch) were determined. In addition, considering that the trajectory of major stress is parabola, the formula of horizontal pressure coefficient was deduced in the friction arch. The parabolic soil arching zone is assumed as a three-hinged arch with reasonable arch axis, and the formula of load transfer was derived considering the transition effect of parabolic soil arching. The results of experiment, theoretical models and numerical model were adopted to verify the proposed analytical model. Finally, the influence of the key parameters on the vertical load on jacked pipe were also discussed in detail. This work provides a meaningful reference for evaluating the vertical load on jacked pipe for design of pipe jacking. [ABSTRACT FROM AUTHOR]

The surcharge load at the ground surface inevitably breaks the original equilibrium state between the underneath tunnel and the surrounding soil, which will impact the service performance of a subway tunnel. This paper presents a novel semi-analytical approach for assessing the time-dependent, longitudinal responses of a subway tunnel in soft soil strata induced by the surcharge load. The solution is developed based on the framework of the classical "two-stage method" but innovatively incorporates the effects of ground stratification, the consolidation process, and the longitudinal stiffness reduction of the lining. Biot's poroelastic theory in conjunction with the Laplace-Fourier transform technique is selected to model the deformation of the stratified ground, while the Timoshenko beam on a Pasternak foundation is employed to model the mechanical responses of the tunnel. The proposed semi-analytical solution is validated not only by comparison with benchmark solutions and a finite element model, but also by predicting a well-documented field measurement. Parametric analyses are conducted to investigate the effects of the elastic modulus and the permeability coefficient of the stratified ground on the longitudinal responses of the tunnel. It is expected that the proposed solution can serve as a useful tool for evaluating the effects of the surcharge load on the longitudinal responses of a subway tunnel. [ABSTRACT FROM AUTHOR]

The authors devote a quantitative assessment on the synchronisation capability of a line‐start permanent magnet synchronous motor (LSPMSM) equipped with a hybrid rotor. The quantitative assessment is realised by determining a load criterion consisting of load torques and inertias under which the motor will just synchronise. During the process of load‐criterion determination, close attention is paid to parameters governing the motor synchronisation behaviour. Following the principle of stator‐current error minimisation, the time‐variant magnetising inductances and permanent magnet (PM) flux linkages of the analysed LSPMSM are simplified into slip‐dependent constants via the simple and robust genetic algorithm (GA). The load criterion is then obtained after the establishment of a dynamic motor model involving the simplified parameters. Prototyping tests focused on motor speed‐time responses under different mechanical loads are carried out to validate the obtained load criterion and the paper analyses. [ABSTRACT FROM AUTHOR]

This paper investigates the bending of asymmetric functionally graded material (FGM) sandwich plates subjected to thermo-mechanical loads in thermal environments. In this paper, a thermo-mechanical analysis model for asymmetric FGM sandwich plates is proposed, which contains only four control equations and four unknown variables. The governing equation is obtained through refined shear theory and the principle of virtual work, and the Navier method is used to solve it. Numerical examples of simply supported FGM sandwich plates under thermo-mechanical loads are given to verify the accuracy of the model. Finally, detailed studies are conducted on the bending of asymmetric FGM sandwich plates under thermo-mechanical loads, exploring the effects of various parameter changes on their bending behavior, and providing strong guidance for the application of asymmetric FGM sandwich plates in industrial production practice. [ABSTRACT FROM AUTHOR]

Adhesion is a major element of the bonding technologies used today. This way of joining meets the requirements of mechanical load, with high reliability of the product, and in connection with the production and climatic conditions. Bonding is the process of making inseparable bonds in mechanical engineering with non-metallic material, through adhesion and cohesion forces, without significant impact on the structure of the parts to be joined. Gluing (adhesive joint), as a way of making joints in mechanical engineering, is gaining importance in the development of spacecraft and aircraft, as well as the automotive industry. This requires high load-bearing capacity and stiffness, with minimal weight, so alloys such as aluminum and titanium are used. Adhesive joining is increasingly displacing the dominant rivets when joining light metals, and is used to join thin sheets made of different types of materials. In this paper, the possibilities of adhesive joining and the characteristics of glued joints made of aluminum alloy AW-5754 were researched, using static tests, and their fractography was analyzed. [ABSTRACT FROM AUTHOR]

Transient stress and deformation analysis of a functionally graded rotating cylinder made of Al-Sic with short length under thermal and mechanical loads is studied in this paper. It is assumed that the cylinder is located on a friction bed and is subjected to an external torque. The material property is assumed to be variable along the radial direction based on volume fraction distribution. Thermal conductivity equation with time parameter is solved to obtain temperature distribution by Finite Difference Method. First-order shear deformation theory is used to derive kinematic relations. The governing equations are derived using minimum total potential energy and Euler relations. These governing equations are solved using the method of Eigenvalue and Eigenvector. The physical and loading boundary conditions are applied to obtain unknown coefficients. As the main result of this paper, it is concluded that the radial displacement is uniform at the middle of a cylindrical shell and is decreased to zero with an increase of axial coordinate. [ABSTRACT FROM AUTHOR]

Wind turbines in wind farms often operate in waked or partially waked conditions, which can greatly increase the fatigue damage. Some fatigue considerations may be included, but currently a full fidelity analysis of the increased damage a turbine experiences in a wind farm is not considered in wind farm layout optimization because existing models are too computationally expensive. In this paper, we present a model to calculate fatigue damage caused by partial waking on a wind turbine that is computationally efficient and can be included in wind farm layout optimization. The model relies on analytic velocity, turbulence, and load models commonly used in farm research and design, and it captures some of the effects of turbulence on the fatigue loading. Compared to high-fidelity simulation data, our model accurately predicts the damage trends of various waking conditions. We also perform example wind farm layout optimizations with our presented model in which we maximize the annual energy production (AEP) of a wind farm while constraining the damage of the turbines in the farm. The results of our optimization show that the turbine damage can be significantly reduced, more than 10 %, with only a small sacrifice of around 0.07% to the AEP, or the damage can be reduced by 20% with an AEP sacrifice of 0.6 %. [ABSTRACT FROM AUTHOR]

Grid-connected power-converter-interfaced systems have been sharing the responsibility of grid generation alongside conventional synchronous generators. However, these systems lack spinning reserves, leading to a decrease in system inertia and resulting in more pronounced frequency deviations during power imbalances. Therefore, grid codes require the active involvement of wind energy conversion systems in frequency control, aiming to constrain the frequency and rate of change of frequency variations within predefined limits. This paper reviews fast power-reserve control techniques without energy storage in wind energy conversion systems that do not depend on frequency or rate of change of frequency values. The resulting effects on system frequency, energy production, mechanical loadings, and electrical loadings are assessed. The techniques are classified in the maximum-power point-tracking region according to the power function during the transient response, such as constant, speed-, time-, or mechanical power-dependent methods. Both overproduction and underproduction stages are considered. Certain techniques are tested on simulation grids that include either hydro or no-reheat steam generators, followed by a comparative analysis. [ABSTRACT FROM AUTHOR]

This paper discussed the fracture analysis of two collinear cracks under a thermo-magnetic-electric-elastic field. Taking advantage of the permeable crack models and the singular integral equation, the analytical solutions of important parameters around two collinear cracks are obtained. An example is used to demonstrate the method provided in this paper. The effects of the dimensionless quantities between the upper and lower crack surfaces, such as heat flux on the crack surface, electric displacement, magnetic induction per unit thickness, and the corresponding intensity factors near the inner and outer crack tips, are shown in the case analysis. It should be emphasized that because the theoretical solution obtained in this paper has an explicit form, it is convenient to solve the stress intensity factor. In particular, it is very convenient to solve the influence of various physical quantities on the stress intensity factor of the crack tip. [ABSTRACT FROM AUTHOR]

This document is a correction to a paper on the electromotility of outer hair cells. It addresses errors in the appendix of the paper, specifically in the transition rates and equations. The corrected values and equations are provided. The paper discusses the relationship between electromotility and molecular conformational changes, as well as the voltage dependence of membrane capacitance. The correction emphasizes the importance of considering the energy barrier between conformational states and provides revised equations and transition rates. The document also presents equations and models related to electromotility, including the effect of viscous drag and complex mechanical relaxation. It introduces a modified model that predicts a smaller difference between two quantities, x and y, compared to experimental observations. The document is technical in nature and provides examples of frequency dependence. [Extracted from the article]

The aim of this study is to solve a practical problem encountered in the automotive industry, especially the failure of a cracked lower control arm made of al 6062 T6 material during static and crash physical tests, and to characterize the behavior of cracked parts made of aluminum materials using the fracture mechanics parameters. As a first step, we carried out a numerical study and simulation using Abaqus/CAE 2020 software and the finite element method to determine the stress concentration and load limit capacity for different car weight cases. The von Mises stress variation shows crack initiation and propagation to be in the area of the lower control arm's attachment to the vehicle platform, where stress is concentrated. These numerical results are consistent with the experimental test results found by automotive manufacturers. Also, we find that the mechanical load that can support this part is below 4900 N for good performance. In the second step, we use the results of the first section to simulate the failure of a lower control arm with a crack defect. This paper investigates the stress intensity factor KI in mode I for different lengths (L) and depths (a) of the crack in the lower control arm using the extended finite element method (XFEM) under Abaqus/CAE. For crack failure initiation and progression, we relied on the traction separation law, specifically the maximum principal stress (MAXPS) criterion. The KI factor was evaluated for the materials steel and Al 6062 T6. The results obtained from the variation of the KI coefficient as a function of crack depth (a) and the thickness (t) show that the crack remains stable even when a depth ratio (a/t = 0.8) is reached for the steel material. However, the crack in the Aluminum 6062 T6 material becomes unstable at depth (a/t = 0.6), with a high risk of total failure of the lower control arm. [ABSTRACT FROM AUTHOR]

Due to the high interest in the use of glass/epoxy laminates in aerospace applications, aviation, and as cryogenic tanks, it is crucial to understand the behavior of composites under challenging environmental conditions. Polymer composites are exposed to low temperatures, including cryogenic temperatures, which can lead to the initiation of microdamage. This paper investigates damage initiation/accumulation and its influence on the properties of cross-ply woven glass fiber epoxy composites at low temperatures compared to room temperature conditions. To evaluate the influence of a low-temperature environment on the mechanical performance of glass fiber reinforced epoxy composite (GFRP) laminates, three types of test campaigns were carried out: quasi-static tensile tests and stepwise increasing loading/unloading cyclic tensile tests at room temperature and in a low-temperature environment (−50 °C). We demonstrated that the initial stiffness of the laminates increased at low temperatures. On the other hand, there were no observed changes in the type or mechanism of developed damage in the two test conditions. However, the reduction in stiffness due to the accumulated damage was more significant for the laminates tested at low temperatures (~17% vs. ~11%). Exceptions were noted in a few formulations where the extent of damage at low temperatures was insignificant (<1%) compared to that at room temperature. Since some of the studied laminates exhibited a relatively minor decrease in stiffness (~2–3%), we can also conclude that the formulation of matrix material plays an important role in delaying the initiation and formation of damage. [ABSTRACT FROM AUTHOR]

The result of the development of additive manufacturing (AM) methods is the increasing use of the selective laser melting (SLM) method as a technique for producing tooling for injection moulds and die casting pressure moulds from maraging steel powders. The mould components are subjected to varying thermo-mechanical loads during these operations. This paper presents a numerical model that is used to predict the fatigue life of a material that is loaded with a time-varying temperature field according to the classic and modified Coffin test. Using a computational model, the temperature changes in the resistance-heated specimen and the stress and strain fields that are caused by this phenomenon were determined. Using three different multiaxial fatigue criteria, the fatigue life of SLM steel was determined. Numerical calculations were verified using experimental thermal fatigue tests on 1.2709 SLM steel that was aged at 490 °C as well as via metallographic tests. The numerical model was used to predict the durability of the same steel aged at 540 °C. The effect of specimen clamping conditions on the fatigue life of SLM steel was determined numerically. The value of the decrease in strength of SLM steel as a result of the increasing number of cycles of temperature changes was determined experimentally; a great influence of ageing temperature on fatigue life was found. Changes in the structure of steel occurring during cyclic changes in temperature are presented. [ABSTRACT FROM AUTHOR]

This paper develops a modeling method with an incremental stress–strain–environment constitutive model to predict the change in the plastic mechanical behavior of concrete caused by environmental action. The model regards the environmental factor as a constitutive variable, similar to stress and strain. The yield condition of the model is a function of stress, the plastic internal variable, and the environmental variable. The loading–unloading criterion is established in the space constructed by the strain and the environmental variable to determine the contribution of mechanical loads and environmental factors to plastic deformation. By considering the strain rate as an environmental factor and applying the proposed method, a stress–strain–strain rate constitutive model of concrete is developed to describe the plastic flow caused by the combined action of stress and strain rate. In addition, constant- and variable-strain rate loading tests are performed to evaluate the performance of the established model. In particular, the model's capabilities are further highlighted by comparing the simulation results of the dynamic stress–strain model and the proposed model under loading conditions with rapidly decreasing strain rates. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of Support Vector Regression hyperparameters optimization on electrical load prediction. Accurate and robust load prediction helps policy makers in the energy sector to make inform decision and reduce losses. To achieve this, Bayesian optimization technique was employed for the hyperparameters optimization which are then used for the load prediction. The hyperparameters are the regularization parameters and the epsilon. In addition, the effects of sliding window during the load prediction were also evaluated. The sliding window values were varied from 1 to 5. The results showed that the sliding window of 1 had the optimized hyperparameters with the best performing evaluation metrics of 0.01912 and 0.09493 for MSE and MAE respectively. [ABSTRACT FROM AUTHOR]

The concentrations of cellulose chemical markers, in oil, are influenced by various parameters due to the partition between the oil and the cellulose insulation. One major parameter is the oil temperature which is a function of the transformer load, ambient temperature and the type of cooling. To accurately follow the chemical markers concentration trends during all the transformer life, it is crucial to normalize the concentrations at a specific temperature. In this paper, we propose equations for the normalization of methanol, ethanol and 2-furfural at 20 °C. The proposed equations have been validated on some real power transformers. [ABSTRACT FROM PUBLISHER]

Splines are irreplaceable in high-speed aviation fields due to their simplicity, reliability, and high specific power. Aviation splines are not only subjected to severe operating mechanical loads, but also sometimes operate under grease-lubricated and non-lubricated environments. All of this results in aviation splines suffering widespread failures. Since the 1960s, many researchers have carried out much research on aviation splines. The wide range of research topics demonstrates the technical challenges of understanding aviation spline. This paper reviews the research of aviation spline from the aspects of failure form, fatigue strength, surface contact stress, effects of lubrication, and misalignment on wear, as well as experiments. Relevant research shows crowned splines can mitigate the spline wear process induced by angular misalignment, and oil-lubricating splines experience almost no wear. This paper also looks forward to the future development directions of aviation splines. [ABSTRACT FROM AUTHOR]

Because wind power is connected to the grid on a large scale, frequency fluctuation in the power grid, which is defined as a system safety risk to the power grid, occurs from time to time. According to the grid code rules of China, wind turbines are required to be equipped with primary frequency modulation or inertia response control capability, which are used to support the safe and stable operation of the power grid. During the traditional frequency modulation process of the wind turbine, power limiting operation or pitch angle reservation is generally adopted to ensure that the reserved energy can be released at any time to support the frequency change in the power grid. However, the frequency support method leads to a large loss of power generation, and does not consider the coordination between mechanical load characteristics control and primary frequency modulation. In this paper, a mechanical load optimization control strategy for a wind turbine during the primary frequency modulation process, based on LIDAR (light detection and ranging) feed forward control technology, is proposed and verified. Through LIDAR feed forward control, the characteristics of incoming wind speed can be sensed in advance, with the consequence that the wind turbine can participate in, and actively control, the primary frequency modulation procedure. According to the characteristics of incoming wind, for instance the amplitude and turbulence, simultaneously, the size of the reserved pitch angle can be adjusted in real time. This kind of method, coordinating with the mechanical load of the wind turbine, can be used to reduce both the ultimate load and fatigue damage as much as possible. Finally, the mechanical load characteristics of the wind turbine with and without the control strategy are compared and studied through simulation. The research results show that the load optimization control strategy based on LIDAR feed-forward control technology can effectively reduce the fatigue and ultimate loads of the wind turbine while supporting the frequency change in the power grid; especially for the fatigue load of tower base tilt and roll bending moments, the reducing proportion will be about 4.3% and 6.3%, respectively. [ABSTRACT FROM AUTHOR]

The multiphase electric drives are of interest in fields where reliability and higher torque are guiding criteria, especially important in electric traction. In this paper a six-phased asynchronous machine electric drive for traction systems is analyzed for power quality indices. The driving factors for analysis of viability of such systems are dynamic properties and efficiency. Efficiency is a complex measure for electric systems, such as the asynchronous motor is designed to work with perfectly sinusoidal waveforms of voltages and currents, an impossible fact for variable speed and torque mechanical loads, where power converters are necessary to drive the motor. The part of drive efficiency that will be the center of this study is the power quality indices of the designed prototype multiphase electric drive. Specifically, how much distortion is to be expected in a variable speed drive comprised of six-phased asynchronous motor with scalar control, and how will it affect the active power that drives the load. The tools to determining the harmonic distortion and impact on the power quality, and subsequently on energy transfer efficiency, are also calculated numerically. The current standards that reflect this analysis are the IEEE Standards 1459-2010 and 519-2014, and the European equivalent IEC 61000-3-6, which all rely on the Fast Fourier Transform to decompose the waveform. The main limitation of this method is the applicability to steady signals. The real active power will then be deduced from the current and voltage harmonic distortions to determine the efficiency of power transfer to the electric drive. [ABSTRACT FROM AUTHOR]

In this paper, we propose a plate model, within the framework of finite-strain elasticity, to study the magneto-mechanical behaviors of hard-magnetic soft material plates. The 2D vector plate equation is derived from the 3D governing equations through a series expansion and truncation approach. The displacement and traction boundary conditions on the edges of plate samples are also proposed. Compared with the other plate or shell theories, the current plate model naturally incorporates the elastic incompressibility and the magneto-mechanical coupling effect of the material, which doesn't involve any a priori hypotheses on the geometry and deformation of the plates. Thus, it is applicable for modeling the large deformations of hard-magnetic soft material plates. To show the efficiency of the plate model, we study a benchmark problem, i.e., the plane-strain bending deformations of plate samples induced by magnetic and mechanical loads. Some analytical solutions of the plate equation system are derived, which provide accurate predictions on the magneto-mechanical response of the plate samples with different thickness-length ratios and magnetization directions. To promote applications of the plate model, we further derive a simplified plate equation system and write out its weak form, which is then implemented into the finite element software COMSOL Multiphysics. The efficiency of the simplified plate equation system is also verified through some typical examples. It is found that the numerical results obtained from the 2D plate model show good consistency with those of the 3D volume model, while the plate model exhibits obvious advantages in the aspects of numerical efficiency. • The magneto-mechanical response of hard-magnetic soft material plates is studied. • A plate model is proposed through the series-expansion and truncation approach. • Field-induced bending deformations of plate samples are studied analytically. • A simplified plate equation system is derived and its weak form is established. • Numerical simulations based on the plate model show good accuracy and efficiency. [ABSTRACT FROM AUTHOR]

In this paper large deformation of the skew microplate made of laminated composite enhanced with graphene nanosheets is investigated using first shear deformation theory (FSDT) when the plate undergoes combination of mechanical and thermal loads. Halpin-Tsai model is utilised to model mechanical properties while for thermal properties Schapery model is considered. First, shear deformation of the plate was obtained while using Green-Lagrange tensor the non-linear strain of the microplate is extracted using the von-Karman assumptions. Then, by Modified Coupled Stress Theory (MCSD), the components of Cauchy and Couple stress tensors are specified. Finally, using Hamilton Principle the governing equation of the microplate and boundary conditions are computed. After deriving analytical governmental equation results are presented for the simple support boundary condition and the proposed model is validated by previously reported data and it proves to be promising. Primary results showed that with raising skew angle deflection and bending moment decreases which means microplate becomes more rigid in higher skew angles. Higher mechanical loads lead to higher deflections and bending moments. Four different configurations of the layers were analysed from which angle-ply configuration possessed highest deflection and bending while UD configuration revealed the lowest values of deflection and bending moment. [ABSTRACT FROM AUTHOR]