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Ultra-supercritical coal-fired power plants in Japan and globally experience creep damage in the welded parts of their high-chromium steel assets. As the creep damage advances, voids develop at depth by preference and become dense and cause accidents. The voids cannot be detected using existing non-destructive methods, causing the unreasonable and uneconomic management of plants. To establish a non-destructive examination method that can be used for practical and economic maintenance, a detection method for dense creep voids using ultrasonic backscattered waves is proposed herein. The creep-damaged structures are modelled using a transducer and the transmission and reception characteristics are discussed. These characteristics are considered using the finite element method, as they cannot be measured through normal experiments. The results show that without a focusing process at the time of reception, changes in the amplitude of backscattered waves cannot be confirmed; thus, the contribution of transmission focus to creep void detection is limited. Conversely, it is confirmed that when the received backscattered waves in the direction normal to the transducer are integrated and the phase matching is reflected, the amplitude of the scattered waves increases with creep void density. The reception focus considerably contributes towards dense creep void detection. [ABSTRACT FROM AUTHOR]

Capsule endoscopy offers a non-invasive and patient-friendly method for imaging the gastrointestinal tract, boasting superior tissue accessibility compared to traditional endoscopy and colonoscopy. While advances have led to capsules capable of drug delivery, tactile sensing, and biopsy, size constraints often limit a single capsule from having multifunctionality. In response, we introduce multi-capsule endoscopy, where individually ingested capsules, each with unique functionalities, work collaboratively. However, synchronized navigation of these capsules is essential for this approach. In this paper, we present an active distance control strategy using a closed-loop system. This entails equipping one capsule with a sphere permanent magnet and the other with a solenoid. We utilized a Simulink model, incorporating (i) the peristalsis motion on the primary capsule, (ii) a PID controller, (iii) force dynamics between capsules through magnetic dipole approximation, and (iv) position tracking of the secondary capsule. For practical implementation, Hall effect sensors determined the inter-capsule distance, and a PID controller adjusted the solenoid's current to maintain the desired capsule spacing. Our proof-of-concept experiments, conducted on phantoms and ex vivo bovine tissues, pulled the leading capsule mimicking a typical human peristalsis speed of 1 cm/min. Results showcased an inter-capsule distance of 1.94 mm ± 0.097 mm for radii of curvature at 500 mm, 250 mm, and 100 mm, aiming for a 2-mm capsule spacing. For ex vivo bovine tissue, the achieved distance was 0.97 ± 0.28 mm against a target inter-capsule distance of 1 mm. Through the successful demonstration of precise inter-capsule control, this study paves the way for the potential of multi-capsule endoscopy in future research. [ABSTRACT FROM AUTHOR]

The Sheikh Jaber Al-Ahmad Al-Sabah Causeway consists of an asymmetric cable-stayed bridge (340 m) and a prestressed concrete (PSC) box girder bridge (35.80 km) linking Kuwait City and Northern Kuwait. The full load tests were performed on the PSC box girder bridge and the load scale was set to 14,092 kNm which was 98.47% of the maximum design moment (14,310 kNm). A total of 12 individual 40 tonf dump trucks were exerted on the bridge for the tests. Based on the influence line of the target bridge, displacement sensors, and strain gauges were installed at the points where the maximum bending moment would occur. The collected deflection and strain data were compared with the finite element method analysis to analyze the change in stiffness of the bridge. From the analysis, it was found that higher stiffness behavior was identified compared to the design load. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to present a new approach for the modelling of post-tensioned beams with calibration of the FE model to experimental results until the load capacity and post-critical state are reached. Two post-tensioned beams with different nonlinear tendon layouts were analysed. Material testing for concrete, reinforcing steel and prestressing steel was performed prior to the experimental testing of the beams. The Hypermesh program was used to define the geometry of the spatial arrangement of the finite elements of the beams. The Abaqus/Explicit solver was used for numerical analysis. The concrete damage plasticity model was used to describe the behaviour of concrete with different laws of elastic–plastic stress–strain evolution for compression and tension. Elastic-hardening plastic constitutive models were used to describe the behaviour of steel components. An effective approach to modelling the load was developed, supported by the use of Rayleigh mass damping in an explicit procedure. The presented model approach ensures good agreement between numerical and experimental results. The crack patterns obtained in concrete reflect the actual behaviour of structural elements at every loading stage. Random imperfections found during experimental studies on the results of numerical analyses were also discussed. [ABSTRACT FROM AUTHOR]

The health of thermoplastic induction welded joints was evaluated by monitoring the electromagnetic response to a time variant magnetic field through a local measurement of the attenuated and reflected field. For this purpose, a numerical model was developed to study how the joint interface affects this response in the presence and absence of a delamination and as a function of the electromagnetic characteristics of a susceptor. Using a single loop coil geometry as local magnetic field excitation and measurement, the frequency range at which the highest damage detection sensitivity occurs has been identified for different sizes of a delamination in the bond line. It has been found that the presence of a susceptor reduces the capability of damage detection for the considered values of electromagnetic properties. The obtained results are the starting point for further research activities aimed at developing an electromagnetically based sensitive layer for monitoring the health of thermoplastic joints, capable of detecting and quantifying joint damage and assessing residual fatigue life. [ABSTRACT FROM AUTHOR]

Starting from the fact that, in the event of a repeated cyclical impact with an inclined plane of a sphere, the wear shows slip zones, this paper aims to study the process by comparing experimental results with those obtained as a result of a numerical simulations. An experimental stand has been designed which allows a ball repeatedly impacted on a flat surface. The numerical simulation using the explicit Abaqus 2018 software is presented. The novelty consists in the fact that, based on the comparative analysis between the experimental method and the numerical simulation, a prediction can be made regarding the behavior of a material that will be subjected to repeated impacts under different angles of incidence. [ABSTRACT FROM AUTHOR]

When the welded part of a vehicle body is considered in an analysis model, the accuracy of the analysis varies depending on whether the welded part is assumed to be a simple rigid body or if its characteristics are included. Particularly, when assuming a simple rigid body, the accuracy of the stress result may be insufficient, resulting in a large error. In this study, titled "part 2-development of finite element method (FEM) analysis model for predicting fracture strength", a commercial welding simulation program, MSC Simufact welding software, was used to create a finite element method analysis model that includes the material characteristics of the welded part, and the analysis accuracy was determined in comparison with the experimental results presented in part 1. The analysis results showed satisfactory results with an error rate of 0.03%. Thus, the fracture strength and fracture position of the welding specimen could be confirmed using the FEM analysis model. Additionally, assuming that the welded part in spot welding has a simple geometric-shaped structure, a simplification spot welding model was created to determine whether it can replace the plasma arc spot welding experiment and pass the tensile shear test. [ABSTRACT FROM AUTHOR]

This paper conducted a three-point loading experiment and analytical investigations on the shear performance of reinforced concrete (RC) beams with anchor defect at the lower end of stirrups. In the experiment, artificial methods were used to simulate the anchor degradation of the lower end of the stirrup caused by the alkali-aggregate reaction (AAR). The results show that, compared with the sound beams, the anchorage degradation of stirrups reduces the shear capacity of RC beams, and the degree of reduction becomes more pronounced with the increase of the local bond degradation area. The decrease in shear capacity is thought to be attributed to the reduction of the shear contribution by the stirrups and the reduction of the shear resistance by interlock action of coarse aggregate between diagonal cracks. The quantitative evaluation of shear contribution based on the computed stirrup strains confirms that the anchorage defect at the lower end of the stirrup reduces both the shear contribution Vc by concrete and Vs by stirrups, and the reduction of Vs is more significant than Vc.

The Sheikh Jaber Al-Ahmad Al-Sabah Causeway consists of an asymmetric cable-stayed bridge (340 m) and a prestressed concrete (PSC) box girder bridge (35.80 km) linking Kuwait City and Northern Kuwait. The full load tests were performed on the PSC box girder bridge and the load scale was set to 14,092 kNm which was 98.47% of the maximum design moment (14,310 kNm). A total of 12 individual 40 tonf dump trucks were exerted on the bridge for the tests. Based on the influence line of the target bridge, displacement sensors, and strain gauges were installed at the points where the maximum bending moment would occur. The collected deflection and strain data were compared with the finite element method analysis to analyze the change in stiffness of the bridge. From the analysis, it was found that higher stiffness behavior was identified compared to the design load.

Background: Masticatory forces generate various degrees of stress and strain in the periodontium of teeth which determine the clinical functions and load-bearing capacity of the teeth. There are few in vitro studies that have analyzed stress generated due to combined forces acting on the teeth. Thus, the objective of the present study was to do a comparative analysis of the influence of various stresses on the periodontal ligament and alveolar bone of maxillary central incisor with normal bone height and reduced bone height under simulated standard masticatory using finite element stress analysis. Methodology: A 3D model of the tooth was obtained with the help of ANSYS software. These models were subjected to various oblique forces, i.e., 100N and 235.9N, applied at 45° angle on the lingual surface of the maxillary central incisor and stress values were recorded in three dimensions. The results from FE analysis were analyzed using 3D Von Mises Criteria. Results: It was observed that in healthy periodontium; it was observed that among the periodontal structure studied, the maximum stress levels were exerted on root followed by cortical bone, cancellous bone, and PDL, irrespective of the force, as compared to the diseased periodontium, in which the bone height was reduced, the maximum stresses were on root followed by cortical bone, PDL, and cancellous bone. Conclusion: The main factor governing the success of any periodontal procedure depends on the height of the remaining bone and the amount of force exerted on to the tooth and the stress generated within the tooth. The finite element method could be of substantial importance in this respect as it can assess the stresses of various occlusal forces on the periodontal ligament, root, cortical bone, and cancellous bone of teeth in a periodontally healthy and diseased state.

Multiphase induction machines are getting more attention in industry and academia because of their advantages and need for electric vehicles as well as ship propulsion. In this case, more number of power electronics devices are required due to higher number of phases. Moreover, in comparison with electromechanical systems, the probability of failure in power electronic inverter switches will be high. A fault in a semiconductor switch, without any proper alleviating methods, may result in the failure of the entire drive. To improve the reliability of induction motor drives (IMD), there is a necessity to enhance the postfault operation of the inverters. In this article, the proposed nine‐phase IMD incorporates simple mathematical equations and less circuit reconfigurations to work under conditions of open‐switch fault in either a single switch or the inverter's entire leg. This enables the drive to achieve balanced steady‐state operation with minimal deration in output power/torque under the fault conditions. In addition, alternative operational technique, which modulates the healthy phases of fault phase group with 50% duty ratio and minimal circuit reconfiguration, is discussed in this article. Moreover, all possible fault conditions and associated reconfiguration details of the drive are described in detail. To validate the proposed concepts, finite element method analysis is performed using ANSYS Maxwell, and experimentation is performed in the laboratory for both normal and fault conditions on nine‐phase IMD. [ABSTRACT FROM AUTHOR]

For efficient calculation of energy release rate (ERR) for interface cracks in environmental barrier coatings (EBCs) with a columnar layer, we propose a simple and versatile homogenization method of the columnar layer. The columnar layer consisting of a number of fine columns is modeled as an anisotropic homogenized layer whose elastic properties are isotropic in the plane perpendicular to the layer thickness direction. The homogenization was achieved by a finite element method (FEM) analysis for a single columnar model to obtain elastic parameters that characterize the homogenized layer. For validation of the homogenization method, we conduct an FEM analysis for a typical EBC structure and obtain the ERRs of an interface crack with various crack length and columnar size. We demonstrate that the homogenization method provides estimation of ERR with a good accuracy on the safer side, which is advantageous for EBC structure design. In addition, the method can reduce the calculation time by more than 50%. From these results, we conclude that the proposed homogenization method can be applied generally for estimation of ERR in EBCs with a columnar layer. [ABSTRACT FROM AUTHOR]

In this paper a scaling approach for the solution of 2D FE models of electric machines is proposed. This allows a geometrical and stator and rotor resistance scaling as well as a rewinding of a squirrel cage induction machine enabling an efficient numerical optimization. The 2D FEM solutions of a reference machine are calculated by a model based hybrid numeric induction machine simulation approach. In contrast to already known scaling procedures for synchronous machines the FEM solutions of the induction machine are scaled in the stator-current-rotor-frequency-plane and then transformed to the torque- speed-map. This gives the possibility to use a new time scaling factor that is necessary to keep a constant field distribution. The scaling procedure is validated by the finite element method and used in a numerical optimization process for the sizing of an electric vehicle traction drive considering the gear ratio. The results show that the scaling procedure is very accurate, computational very efficient and suitable for the use in machine design optimization.

Background: Masticatory forces generate various degrees of stress and strain in the periodontium of teeth which determine the clinical functions and load-bearing capacity of the teeth. There are few in vitro studies that have analyzed stress generated due to combined forces acting on the teeth. Thus, the objective of the present study was to do a comparative analysis of the influence of various stresses on the periodontal ligament and alveolar bone of maxillary central incisor with normal bone height and reduced bone height under simulated standard masticatory using finite element stress analysis. Methodology: A 3D model of the tooth was obtained with the help of ANSYS software. These models were subjected to various oblique forces, i.e., 100N and 235.9N, applied at 45° angle on the lingual surface of the maxillary central incisor and stress values were recorded in three dimensions. The results from FE analysis were analyzed using 3D Von Mises Criteria. Results: It was observed that in healthy periodontium; it was observed that among the periodontal structure studied, the maximum stress levels were exerted on root followed by cortical bone, cancellous bone, and PDL, irrespective of the force, as compared to the diseased periodontium, in which the bone height was reduced, the maximum stresses were on root followed by cortical bone, PDL, and cancellous bone. Conclusion: The main factor governing the success of any periodontal procedure depends on the height of the remaining bone and the amount of force exerted on to the tooth and the stress generated within the tooth. The finite element method could be of substantial importance in this respect as it can assess the stresses of various occlusal forces on the periodontal ligament, root, cortical bone, and cancellous bone of teeth in a periodontally healthy and diseased state. [ABSTRACT FROM AUTHOR]

The mechanical properties of certain flexible core materials of ship structure sandwich panels, having skins made of metallic or composite laminates maybe significantly influenced by the temperature variations that may occur during the operational loading. At the same time, the improving knowledge of the behaviour of these panels in terms of bending strength and other stress/strain related aspects in various harsh conditions increases their superiority in terms of weight-to-strength ratio, high stiffness, easy to manufacture, acoustic, and thermal insulation. In the paper, the behaviour of the ship structural rectangular sandwich panels to the mechanical and thermal loading are presented. The sandwiches have a special core of 20 mm and skins made out of different materials (glass fiber reinforced polyester, steel and aluminum) with a thickness of 3 mm. Analysis consists of the behaviour of the composite sandwich panels in the bending test at constant speed by the three-point method, for three distances between different supports, by measuring the maximum displacement and force applied to the specimens under various thermal fields. The sandwich structures are also thermally analysed, determining their thermal conductivity by the heat flow measurement method. The experimental results are compared with the results obtained by finite element analysis in numerical simulation of all modelling cases. [ABSTRACT FROM AUTHOR]

The simply supported double composite beam with moving mass is investigated. During the analysis,the acceleration of the moving mass can be arbitrary. With some assumptions, the strain energy and the kinetic energy of the system are gotten. Then the axial-bending coupled equations of motion are derived by the Hamilton’s principle, and solved by the finite element method combined with Newmark method. The numerical examples show that, the larger the speed of moving mass the larger the maximum vertical displacement of the beam; the horizental displacement of centre point of the beam is zero when the moving mass on the centre point; under the same conditions, the double composite beams have higher stiffness-to-weight ratio than the single layer ones. The conclusions obtained here provide theoretical references for designing the structures with high strength and light weight.

It is necessary to have a model to design magnetic gear (MG) optimally and to investigate the effective parameters on its performance. This study proposed a two‐dimensional (2D) model to predict the magnetic components of coaxial MG (CMG). This model is based on the mesh analysis method considering core nonlinear B‐H curve. In the proposed model, the radial and tangential components of flux densities, magnetic fluxes as well as the inner/outer rotor torque are estimated by extraction of the magnetic equivalent circuit (MEC). The effect of non‐linear B‐H magnetising curve is considered on the MEC model and it is compared with linear core (constant probability). Furthermore, the dynamic model of CMG is presented and its torque‐angle curve and consequently its pull‐out torque is obtained. To validate the proposed model, the 2D MEC model results are compared with results of finite element method analysis. [ABSTRACT FROM AUTHOR]

In recent years, a minimally invasive medical needle is required. The development of such a fine needle requires evaluation of puncture resistance force. We have developed various microneedles and conducted the puncture experiments to evaluate their resistance force against an artificial skin made of silicone rubber. In this study, it is attempted to reproduce the puncture experiment by FEM simulation, in which accurate three dimensional (3D) models of needle and skin are constructed, and the conditions of material properties, model size, puncture distance, puncture speed, etc. are set to the same ones as the experiments. As a commercially available nonlinear FEM software, LS-DYNA was employed. The results of FEM analysis and those of experiment were compared to estimate what extent they are matched. As a result, the tendency of the load curve, i.e., transition of resistance force with respect to puncturing distance, and the state of skin deformation were well matched, showing the possibility of FEM analysis to reproduce the experiment. The error of resistance force between analysis and experiment was 20% at most. It is expected that the parameter study would be possible, in which the performance of needle is evaluated by changing the parameters, e.g., its size, shape, how to insert it to the skin, etc.

This paper proposes a mechanism for preventing needle buckling and skin deformation by mimicking the mosquito's labium and discusses a puncturing device with a jig-integrated microneedle, based on the proposed mechanism. A sheet simplifying this mechanism was attached to an artificial skin's surface, and experiments to puncture this artificial skin and corresponding finite element method (FEM) analysis were conducted. It was confirmed that the deformation of the puncture target and the puncture resistance force decreased with the use of the sheet. Based on these experimental and FEM-analytical results, a puncturing device with a jig-integrated needle has been designed and fabricated with 3D laser lithography. Experiments have been conducted with the fabricated device to puncture an artificial skin and the skin of a nude mouse to determine needle buckling prevention and the reduction in skin deformation. The study successfully samples blood from the mouse without stagnation of blood flow. [ABSTRACT FROM AUTHOR]

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In this paper a scaling approach for the solution of 2D FE models of electric machines is proposed. This allows a geometrical and stator and rotor resistance scaling as well as a rewinding of a squirrel cage induction machine enabling an efficient numerical optimization. The 2D FEM solutions of a reference machine are calculated by a model based hybrid numeric induction machine simulation approach. In contrast to already known scaling procedures for synchronous machines the FEM solutions of the induction machine are scaled in the stator-current-rotor-frequency-plane and then transformed to the torque- speed-map. This gives the possibility to use a new time scaling factor that is necessary to keep a constant field distribution. The scaling procedure is validated by the finite element method and used in a numerical optimization process for the sizing of an electric vehicle traction drive considering the gear ratio. The results show that the scaling procedure is very accurate, computational very efficient and suitable for the use in machine design optimization. [ABSTRACT FROM AUTHOR]

This article designs the width of slit‐like flux barriers to improve the space harmonic distribution of the air‐gap flux density in a slit stator motor. The slit stator motor has slit‐like flux barriers at wound teeth of the stator. The stator design can adjust the space harmonic distribution with the slit width. Space harmonic distributions govern torque and losses in motors. For this reason, the dependence of the space harmonic distribution on the slit width should be clarified to design slit stator motors. The dependence is investigated through a theoretical calculation based on a magnetic circuit model and a finite element method analysis. These methods show that a space harmonic producing the drive torque is maximised at a slit width and other dominant detrimental space harmonics are decreased with the increase of the slit width. The improved space harmonic distribution is verified by performing an experiment with a measuring rotor. [ABSTRACT FROM AUTHOR]

This paper presents the cost reduction design of a brushless DC motor (BLDCM) considering twelve step control. The twelve step control can improve the output of the motor using the conventional six step control. Weight reduction can be effectively achieved by reducing rotor, stator and magnet through optimization of BLDCM using a response surface method (RSM). The BLDCM volume was decreased by about 45%, while satisfying basic performance requirements and improving efficiency. Original and optimized motors were built and tested. Experimental results are compared in terms of output power and efficiency. [ABSTRACT FROM AUTHOR]

Although it is known that aging plays an important role in the incidence and progression of cervical spondylotic myelopathy (CSM), the underlying mechanism is unclear. Studies that used fresh bovine cervical spinal cord report the gray matter of the cervical spinal cord as being more rigid and fragile than the white matter. However, there are no reports regarding the association between aging an tensile and Finite Element Method (FEM). Therefore, FEM was used based on the data pertaining to the mechanical features of older bovine cervical spinal cord to explain the pathogenesis of CSM in elderly patients. Tensile tests were conducted for white and gray matter separately in young and old bovine cervical spinal cords, and compared with their respective mechanical features. Based on the data obtained, FEM analysis was further performed, which included static and dynamic factors to describe the internal stress distribution changes of the spinal cord. These results demonstrated that the mechanical strength of young bovine spinal cords is different from that of old bovine spinal cords. The gray matter of the older spinal cord was significantly softer and more resistant to rupture compared with that of younger spinal cords (P<0.05). Among the old, although the gray matter was more fragile than the white matter, it was similar to the white matter in terms of its rigidity (P<0.05). The in vitro data were subjected to three compression patterns. The FEM analysis demonstrated that the stress level rises higher in the old spinal cords in response to similar compression, when compared with young spinal cords. These results demonstrate that in analyzing the response of the spinal cord to compression, the age of patients is an important factor to be considered, in addition to the degree of compression, compression speed and parts of the spinal cord compression factor. [ABSTRACT FROM AUTHOR]