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Recently, Egypt had seismic activity. These seismic events have affected the stability of minarets, especially historical ones. Weight is one of the minaret's main stability factors. The main objective of the current research is to perform a three-dimensional (3D) assessment of an existing minaret, determine its accurate spatial model, document its current condition, examine its stability in the event of earthquakes, and identify the requisite measures to safeguard the minaret from any potential damage. The masonry to construct the minaret was used by extracting and examining specimens of this substance to determine its physical characteristics. The current work created three-dimensional models of the Abou-Ghanam El-Bialy minaret using a terrestrial laser scanner (TLS) to document its current condition, as well as minaret was subjected to a free vibration analysis using 3D finite element modeling. Finally, the minaret's seismic behavior was assessed utilizing mode forms, base responses, and normal stresses. The surveying method effectively documented the Minarets' existing case. The 3D seismic analysis showed that the minaret responded dynamically to earthquake loading, with mode shapes, base reactions, and normal stresses being crucial characteristics. Based on these data, we may suggest procedures to protect the minaret during seismic events. [ABSTRACT FROM AUTHOR]

By addressing the phenomenon of carbody abnormal vibrations in the field, the acceleration of the carbody and bogie was measured using accelerometers, and the diamond mode of the carbody was identified. The equivalent conicity of the wheelset and the acceleration at the frame end indicated that the shaking of the carbody was caused by bogie hunting. In the SIMPACK simulation, the acceleration frequency and amplitude at the frame end and midsection of the side beam were calculated. The lateral deformation amplitude of the side beam in the finite element model was extracted, and a modal shape function for the diamond-shaped mode was established. By utilizing the modal vibration equation, the modal generalized forces of the carbody were computed, revealing that, during carbody shaking, the yaw damper force contributed significantly among the forces of the secondary suspension, with the phase difference between the front and rear bogies approaching 180°. This insight offers a novel perspective for subsequent active control strategies. Subsequently, these modal generalized forces were applied as external excitation to a coupled vibration model encompassing both the carbody and transformer. Aiming to reduce the acceleration amplitude at the side beam, the transformer was treated as a dynamic vibration absorber, allowing for the optimization of its lateral suspension parameters. As a result, the lateral and vertical acceleration amplitudes at the side beam were concurrently reduced, with the maximum decrease reaching 58.5%, significantly enhancing the ride comfort. [ABSTRACT FROM AUTHOR]

Living organisms are constructed from proteins that assemble into biomolecular complexes, each with a unique shape and function. Our knowledge about the structure–activity relationship of these complexes is still limited, mainly because of their small size, complex structure, fast processes, and changing environment. Furthermore, the constraints of current microscopic tools and the difficulty in applying molecular dynamic simulations to capture the dynamic response of biomolecular complexes and long-term phenomena call for new supplementary tools and approaches that can help bridge this gap. In this paper, we present an approach to comparing biomolecular and origami hierarchical structures and apply it to comparing bacterial microcompartments (BMCs) with spiral-based origami models. Our first analysis compares proteins that assemble the BMC with an origami model called "flasher", which is the unit cell of an assembled origami model. Then, the BMC structure is compared with the assembled origami model and based on the similarity, a physical scaled-up origami model, which is analogous to the BMC, is constructed. The origami model is translated into a computer-aided design model and manufactured via 3D-printing technology. Finite element analysis and physical experiments of the origami model and 3D-printed parts reveal trends in the mechanical response of the icosahedron, which is constructed from tiled-chiral elements. The chiral elements rotate as the icosahedron expands and we deduce that it allows the BMC to open gates for transmembrane passage of materials. [ABSTRACT FROM AUTHOR]

Abnormal wear of stitch wires due to interference poses a serious threat to railway safety. To avoid this scenario, the concept of the dynamic envelope of the stitch wire was proposed, accompanied by an interference check method. A multi-node beam model of the stitch wire was established using the finite element method, employed to simulate the pantograph and catenary system, and validated by field test. The dynamic behaviour of the stitch wire was studied, and the concept of dynamic envelope was introduced. Moreover, factors affecting this envelope were analysed, and an interference check method was proposed. Results demonstrate that, the vibration of the stitch wire mainly occurs in the vertical direction and intensifies with increasing speed. Its vertical vibration increases from 70 mm to 137 mm as the train speed goes from 300 km/h to 400 km/h. Cantilever assembly errors and dropper installation issues are the main causes for the abnormal wear of stitch wires. A 100 mm assembly error reduces the clearance from 67 mm to 14 mm, while a 2 m dropper installation error eliminates the clearance entirely. This study provides valuable insights for enhancing the safety of catenary system. [ABSTRACT FROM AUTHOR]

Globally, rail transit is developing toward higher speeds, larger axle weights, and greater environmental friendliness. The more and more complex wheel–rail interaction will result in the dynamic responses of vehicles, tracks and other structures needing more in-depth theoretical research. However, most existing models for dynamic simulations of the vehicle–track coupling system need to extend the model on both sides of the concerned region to eliminate the boundary effect. To a certain extent, this kind of process method increases the computational effort. To overcome this disadvantage, a hybrid model combined with the analytical method and finite element method was proposed. The moving support system (including transition nodes) was specially established referring to the analytical solution of rail deflection based on the Winkler elastic foundation beam theory to realize the combination of the two methods. Two examples were presented to verify the stability and accuracy of the proposed model. The comparison results show that simulation results of vertical wheel–rail forces and track vibrations are almost consistent with the existing model. Furthermore, the calculation efficiency was discussed and certificated under different long-marshalling trains, with an obvious speedup factor that could be more than 2.5 for 16-marshalling train. The proposed model has a wide application prospect in the vehicle–track coupling analysis of long-marshalling trains, especially for heavy haul railways with hundreds of vehicles. [ABSTRACT FROM AUTHOR]

This study developed a finite element method (FEM) dynamic simulation to visualize the deployment behavior of thin membrane structures in the space environment. The proliferation of space debris resulting from accelerated space development threatens the future of space. Numerous researchers have explored strategies to prevent artificial structures from remaining in space and becoming space debris. One such method involves utilizing a drag sail device to de-orbit artificial structures, which reduces their kinetic energy by inducing additional atmospheric drag, allowing them to re-enter the Earth's atmosphere. Tohoku University and Nakashimada Engineering Works, Ltd. have successfully developed a deployable membrane structure for de-orbit purposes and demonstrated its effectiveness in space. Space structures, such as membranes, exhibit highly nonlinear behavior due to their flexible properties, and ground tests by actual devices cannot fully demonstrate their deployment stability in a microgravity environment. Therefore, evaluating the deployment behavior using simulation methods instead of relying solely on hardware development is crucial. In this study, we employed FEM to establish a simulation environment, which enables us to consider nonlinear oscillations of flexible structures, such as the membrane. The simulation results closely reproduce the deployment motion observed in ground tests by appropriately incorporating constraint conditions related to deployment forces and hardware interactions, such as a hub component initially wrapped by the membrane. The simulation facilitated an assessment of the impact of membrane properties on deployment without the need for physically developing an actual hardware device. We proposed evaluation methods for determining membrane properties in terms of the trend of propagation of deployed surface area and the tendency of deployment motion. This established simulation technique can be utilized to develop future flexible space structures. • De-orbit Membrane Mechanism (DOM) was developed as a satellite de-orbit application. • Formulate nonlinear FEM analysis of non-spin type deployable structures. • Modeling techniques of the membrane in simulation. • Evaluation of the membrane deployment between simulation and ground experiments. • Proposed methods can be used to predict the deployment behavior of the actual membrane. [ABSTRACT FROM AUTHOR]

Temporal bone is often hit by projectiles. Temporal gunshot wounds must be deeply evaluated to establish wound morphology and stress distribution. Finite element analysis (FEA) is a promising tool that can support forensic aspects. A three-dimensional finite element model of a dry skull filled with neural soft tissue and a projectile.40 calibre S&W were obtained. Two situations were simulated: shot angle fired at 90° with and without neural soft tissue. The results exhibit different morphologies in bony entrance wounds as well as the strong influence of soft tissue. There was good reproducibility between bone and neural tissue real behaviour, and the finite element model that was built. In conclusion, the presence of neural soft tissue cannot be neglected in gunshot wounds, since it does alter results. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to investigate the design and optimization of landing gear buffers to improve the landing-phase comfort of civil aircraft. Design/methodology/approach: The vibration comfort during the landing and taxiing phases is calculated and evaluated based on the flight-testing data for a type of civil aircraft. The calculation and evaluation are under the guidance of the vibration comfort standard of GB/T13441.1-2007 and related files. The authors establish here a rigid-flexible coupled multibody dynamics finite element model of one full-size aircraft. Furthermore, the authors also implement a dynamic simulation for the landing and taxiing processes. Also, an analysis of how the main parameters of the buffers affect the vibration comfort is presented. Finally, the optimization of the single-chamber and double-chamber buffers in the landing gear is performed considering vibration comfort. Findings: The double-chamber buffer with optimized parameters in landing gear can improve the vibration comfort of the aircraft during the landing and taxiing phases. Moreover, the comfort index can be increased by 25.6% more than that of a single-chamber type. Originality/value: To the best of the authors' knowledge, this study first investigates the evaluation methods and evaluation indexes on the aircraft vibration comfort, then further conducts the optimization of the parameters of landing gear buffer with different structures, so as to improve the comfort of aircraft passengers during landing process. Most of the current studies on aircraft landing gear have focused on the strength and safety of the landing gear, with very limited research on cabin vibration comfort during landing and subsequent taxiing because of the coupling of runway surface unevenness and airframe vibration. [ABSTRACT FROM AUTHOR]

Owing to the challenge of capturing the dynamic behaviour of metal experimentally, high-precision numerical simulations have become essential for analysing dynamic characteristics. In this study, calculation accuracy was improved by analysing the impact of constitutive models using the finite element (FE) model, and the deep learning (DL) model was employed for result analysis. The results showed that FE simulations with these models effectively capture the elastic-plastic response, and the ZA model exhibits the highest accuracy, with a 26.0% accuracy improvement compared with other models at 502 m/s for Hugoniot elastic limit (HEL) stress. The different constitutive models offer diverse descriptions of stress during the elastic-plastic response because of temperature effects. Concurrently, the parameters related to the yield strength at quasi-static influence the propagation speed of elastic waves. Calculation show that the yield strength at quasi-static of 6061 Al adheres to y = ax + b for HEL stress. The R-squared (R2) and mean absolute error (MAE) values of the DL model for HEL stress predictions are 0.998 and 0.0062, respectively. This research provides a reference for selecting constitutive models for simulation under the same conditions. [ABSTRACT FROM AUTHOR]

Time-domain or transient dynamic response method is the most traditional method used to evaluate the dynamic response of a vibratory system subjected to deterministic inputs. The inertia or damping effects are very crucial in the time scale of loading. The present work determines the time domain analysis of railway locomotive using finite element analysis for Indian tracks. The track inputs are modelled as an ellipsoidal bump, and variations in displacement at different key locations of the truck and carbody models are plotted subjected to standard loading conditions. The response plot of the front and rear locations of the locomotive truck and carbody indicate that these regions are more responsive to wheel inputs in comparison to the mid portion due to unbalanced mass distribution. In the further study vertical-lateral random inputs are measured through track recording car and modelled to express in the form of PSD. These random inputs are provided to finite element modelled flexible bogie frame, and acceleration response is determined. The results obtained are compared with the same obtained from rigid bogie frame formulated using an analytical model. The results obtained from the flexible and rigid body models are found to be in good agreement. [ABSTRACT FROM AUTHOR]

Background: While the development of CT imaging technique has brought cognition of in vivo organs, the resolution of CT images and their static characteristics have gradually become barriers of microscopic tissue research. Purpose: Previous research used the finite element method to study the airflow and gas exchange in the alveolus and acinar to show the fate of inhaled aerosols and studied the diffusive, convective, and sedimentation mechanisms. Our study combines these techniques with CT scan simulation to study the mechanisms of respiratory movement and its imaging appearance. Methods: We use 3D fluid‐structure interaction simulation to study the movement of an ideal alveolus under regular and forced breathing situations and ill alveoli with different tissue elasticities. Additionally, we use the Monte Carlo algorithm within the OpenGATE platform to simulate the computational CT images of the dynamic process with different designated resolutions. The resolutions show the relationship between the kinematic model of the human alveolus and its imaging appearance. Results: The results show that the alveolus and the wall thickness can be seen with an image resolution smaller than 15.6 μm. With ordinary CT resolution, the alveolus is expressed with four voxels. Conclusions: This is a preliminary study concerning the imaging appearance of the dynamic alveolus model. This technique will be used to study the imaging appearance of the dynamic bronchial tree and the lung lobe models in the future. [ABSTRACT FROM AUTHOR]

Percutaneous needle insertion constitutes a widely adopted technique for performing minimally invasive operations. Robot-assisted needle placement and virtual surgical training platforms have the potential to significantly improve the accuracy of these operations. For this, the development of mathematical models that provide a complete characterization of the underlying dynamics of medical needles is considered of paramount importance. In this paper, we develop two three-dimensional nonlinear rigid/flexible dynamic models of brachytherapy and local anaesthetic transperineal biopsy (LATP) needles. The proposed models relax the assumptions of previous investigations, quantify the vibrational behaviour and the rigid-body dynamics of medical needles and allow for real-time haptic and visual feedback information. Their accuracy and computational efficiency are assessed and validated using commercial software. The results show that, among the examined methods, the Rigid Finite Element Method provides the most accurate and numerically efficient solution for capturing the dynamics of flexible medical needles. [ABSTRACT FROM AUTHOR]

This paper presents a virtual generation method for the heterogeneous microstructure of asphalt mixtures. The coarse aggregates used in the digital asphalt mixture were derived from real aggregates captured by a three-dimensional (3D) laser scanner. Then, a rigid-body dynamic simulation framework was proposed to generate a stable skeletal structure composed of coarse aggregates similar to those formed by compaction. Furthermore, FAM and air voids were generated based on the generated aggregate skeleton and the assumption of equal thickness of FAM film. To prove the reliability of the model, the air voids of the digital asphalt mixture samples were verified by comparison with real specimens. The generated digital specimens were also applied to finite element method (FEM) simulations to predict the dynamic modulus of the asphalt mixture and the simulated results were in good agreement with the experimental results. The method can be applied to study the spatial distribution of asphalt mixture components, the movement pattern of aggregate particles during compaction and numerical simulations at the microscopic scale. [ABSTRACT FROM AUTHOR]

This paper presents a virtual generation method for the heterogeneous microstructure of asphalt mixtures. The coarse aggregates used in the digital asphalt mixture were derived from real aggregates captured by a three-dimensional (3D) laser scanner. Then, a rigid-body dynamic simulation framework was proposed to generate a stable skeletal structure composed of coarse aggregates similar to those formed by compaction. Furthermore, FAM and air voids were generated based on the generated aggregate skeleton and the assumption of equal thickness of FAM film. To prove the reliability of the model, the air voids of the digital asphalt mixture samples were verified by comparison with real specimens. The generated digital specimens were also applied to finite element method (FEM) simulations to predict the dynamic modulus of the asphalt mixture and the simulated results were in good agreement with the experimental results. The method can be applied to study the spatial distribution of asphalt mixture components, the movement pattern of aggregate particles during compaction and numerical simulations at the microscopic scale. [ABSTRACT FROM AUTHOR]

The finite element method is widely used to solve the problem of flexible bodies with contact-impact. To express the high-frequency and high-transient characteristics of the impact process and the high stress distribution of the local contact region, the amount of the node coordinates will be very large, which brings great burden to the dynamic simulation. It is particularly important to reduce the degrees of freedom of the system in the contact-impact problem. However, as the impact itself is a strong nonlinear problem, the linear model reduction techniques cannot be used directly. The partition method is presented to solve this problem, in which the deformation of the contact region is described by finite element node coordinates to preserve the local nonlinear characteristic while the deformation of the non-contact region is described by the reduced elastic coordinates. Different model reduction techniques including modal truncation method and Krylov subspace method are used to reduce the degrees of freedom of the non-contact region of an experimental rod-plate impact case, and the results are compared with that of the finite element method and the experiment. The simulation results show that the partition method can effectively reduce the degrees of freedom of the system and maintain good accuracy. Moreover, the Krylov subspace method has an advantage over the modal method in the model reduction of contact-impact problem. [ABSTRACT FROM AUTHOR]

With the development of space technology, the traditional aerospace cooling technology is hard to meet the constantly developing requirements of heat dissipation. In order to address the problem of temperature control for aerospace systems, the pump-driven fluid loop system has been often adopted. In the pump-driven fluid loop system, the rotor system is needed to be analyzed. In this paper, the rotor coupling system of the canned pump with multiple journal bearings has been studied based on the bearing data, lumped parameter method, Reynolds equation and finite element method. By solving the Reynolds equation, parameters of each bearing have been solved, and a database file has been formed. The bearing data have been addressed by linear interpolation. In this study, the static indeterminate problem has been combined to analyze the bearing force, and the bearing characteristic parameters under the steady-state condition have been solved based on the iterative method. The results indicated that the influences of clearance ratio and rotational speed on the natural frequency, critical rotational speed and unbalanced response of the rotor show certain regularity. The study provides a theoretical basis for the stable operation of the whole rotor system. [ABSTRACT FROM AUTHOR]

Consideration of standard landing cases from technical guideline document is the traditional design practice followed to ascertain aircraft landing loads. A rationale approach on landing load generation and its impact on flexible airframe dynamic response is explored, considering multi-variate landing conditions for the first time on land-base high performance aircraft. Methodology on nonlinear landing dynamic response simulation is developed by amalgamating inputs such as nonlinear nose and main landing gear dynamic models, aircraft rigid body dynamics, low speed aerodynamic and thrust forces. True representation of landing gear nonlinear oleo-pneumatic strut and tire characteristics, variable geometric strut structural stiffness and nonlinear spin-up friction resulted in satisfactory correlation of vertical and longitudinal dynamic response simulation with experimental drop test results. The adequacy of lateral dynamic model is established from the compatibility condition of landing gear and tire dynamics. A down selection methodology is worked out considering total probability and first order sensitive multi-variate landing parameters such as pitch, roll and vertical descent speed, taking into account the plausible statistical variation. Transient dynamic response simulation is then performed for the critical landing cases, on a flexible airframe finite element model by inputting landing load time history as base excitation motion. The dynamic amplification of acceleration response on flexible fuselage nose location from the simulation, is verified with flight data accelerometer frequency response. The application of flexible dynamic responses in ensuring the structural integrity of airframe is elaborated. The proposed methodology on landing load generation is pragmatic, in comparison with the traditional design practice and provides insight during early design phase thereby achieving landing gear subsystem development in-unison with airframe structural clearance aspects. [ABSTRACT FROM AUTHOR]

• A framework for a hybrid terramechanics modelling method is presented. • The method involves using ML to augment existing semi-empirical models. • Model presented in a general way that can be applied to any semi-empirical model. • Method applied to a blade simulation with the Fundamental Earthmoving Equation. • Method applied to a wheel simulation with the Bekker-Wong terramechanics formulation. The field of terramechanics focuses largely on two types of simulation approaches. First, the classical semi-empirical methods that rely on empirically determined soil parameters and equations to calculate the soil reaction forces acting on a wheel, track or tool. One major drawback to these methods is that they are only valid under steady-state conditions. The more flexible modelling approaches are discrete or finite element methods (DEM, FEM) that discretize the soil into elements. These computationally demanding approaches do away with the steady state assumption at the cost of including more model parameters that can be difficult to accurately tune. Model-free approaches in which machine learning algorithms are used to predict soil reaction forces have been explored in the past, but the use of these models comes at the cost of the valuable insight that the semi-empirical models provide. In this work, we presume that in a dynamic simulation, the soil reaction forces can be divided into a steady state component that can be captured using semi-empirical models and a dynamic component that cannot. We propose an augmented modelling approach in which a neural network is trained to predict the dynamic component of the reaction forces. We explore how this theory can be applied to the simulation of a soil-cutting blade using the Fundamental Earthmoving Equation and of a wheel driving over soft soil using the Bekker wheel-soil model. [ABSTRACT FROM AUTHOR]

For the pelvic fracture reduction, generally the fragment of the unaffected side is fixed and the affected side is moved to its correct anatomical position and orientation. During the pelvic fracture reduction, circumpelvic muscles deformation is closely related to the surgical accuracy. In this article, the biomechanical properties of musculoskeletal tissue during pelvic fracture reduction are studied. Five-parameter hyperelastic model named Mooney-Rivlin is adopted to analyze muscle's stress–strain relationship. The finite element model of the injured pelvic musculoskeletal tissue is established, and the deformation of circumpelvic main muscles is simulated. Then, the dynamic simulation of pelvic fracture reduction is performed according to the planned spatial reduction path. The results show that when the muscles are stretched the same stretch length, the strain of the gluteus medius is the largest. It is most prone to deformation under and the muscle injury is most easily to occur. During the pelvic fracture reduction, the strain of gluteus maximus is the largest, and it is most prone to deformation and injury. The traction length is the largest, and the traction force mainly comes from the gluteus maximus. This study provides reference for the robot assisted pelvic fracture reduction. [ABSTRACT FROM AUTHOR]

The contactless electromagnetic de-tumbling method does not have physical contact with the uncooperative space targets and can avoid generating new space debris. Due to pollution-free and high safety performance advantages, this method has a tremendous prospect in the application of de-tumbling the uncooperative space targets. In this paper, an improved arc-linear electromagnetic device and its corresponding de-tumbling method are presented based on the principle of electromagnetic eddy current, which is mainly used for the uncooperative space targets. The analytical model of the electromagnetic device is obtained by introducing the Carter and Russel-Norsworthy coefficients and validated by the finite element method (FEM). Then, the effect on the de-tumbling torque with different electromagnetic parameters is further analyzed. Finally, the three-dimensional dynamic simulation of the uncooperative space target is carried out. The results show that the uncooperative space target can be de-tumbled in a short time by the proposed contactless electromagnetic de-tumbling device. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to simulate molded printed circuit board (PCB) warpage behavior under reflow temperature distribution. Simulation models are used to estimate dynamic warpage behavior for different form factor sizes. Design/methodology/approach: This study analyzes warpage during the reflow process. The shadow moiré experiment methodology is used to collect data on the dynamic warpage performance of a model with a form factor of 10mm × 10mm × 1mm. The temperature profile with heating from 25°C to 300°C at intervals of 50°C is used, and the sample is made to undergo a cooling process until it reaches the room temperature. Subsequently, ANSYS static structural simulation is performed on similar form factor models to ascertain the accuracy of the simulation results. Findings: Results show that the deformation and total force induced by coefficient of thermal expansion (CTE) mismatch are examined based on the warpage performance of models with different sizes, that is, 45mm × 45mm × 1mm and 45mm × 15mm × 1mm. Compared with the experimental data, the simulated modeling accuracy yields a less than 5% deviation in the dynamic warpage prediction at a reflow temperature of 300°C. Results also reveal that the larger the model, the larger the warpage changes under the reflow temperature. Research limitations/implications: The simulated warpage is limited to the temperature and force induced by CTE mismatch between two materials. The form factor of the ball-grid array model is limited to only three different sizes. The model is assumed to be steady, isothermal and static. The simulation adopts homogenous materials, as it cannot accurately model nonhomogeneous multilayered composite materials. Practical implications: This study can provide engineers and researchers with a profound understanding of molded PCB warpage, minimal resource utilization and the improved product development process. Social implications: The accurate prediction of molded PCB warpage can enable efficient product development and reduce resources and production time, thereby creating a sustainable environment. Originality/value: The literature review points out that warpage in various types of PCBs was successfully examined, and that considerable efforts were exerted to investigate warpage reduction in PCB modules. However, PCB warpage studies are limited to bare PCBs. To the best of the authors' knowledge, the examination of warpage in a molded PCB designed with a molded compound cover, as depicted in Figure 3, is yet to be conducted. A molded compound provides strong lattice support for PCBs to prevent deformation during the reflow process, which is a topic of considerable interest and should be explored. [ABSTRACT FROM AUTHOR]

In this paper, a numerical method is proposed for a flexible tether motion that spans two different environments and has large displacement and deformation. When considering the behavior of a tethered system in which the tether cable is subjected to the above conditions, variations of an internal boundary in the tether must be considered. In general, the absolute nodal coordinate formulation (ANCF), a nonlinear finite element method, is effective for the dynamic simulation of a flexible body with large displacement and deformation. However, in conventional methods, such as ANCF, the analysis accuracy decreases and the calculation cost increases when the movement of an internal boundary across different environments is considered. In this study, an efficient numerical approach that considers the variations of an internal boundary by using ANCF using variable-domain finite elements is proposed. In addition, to further improve the calculation efficiency, dimensionless variables are introduced using appropriate representative values. The accuracy of the numerical results obtained using the proposed method, which considers an internal variable boundary, is similar to that for a conventional method. [ABSTRACT FROM AUTHOR]

This paper compares different track model formulations for the simulation of dynamic vehicle–track interaction in switches and crossings (S&C, turnouts) in a multi-body simulation (MBS) environment. The investigations are an extension of the S&C simulation Benchmark with the addition of a finite element model of a 60E1-760-1:15 turnout. This model constitutes a common reference from which four different track formulations are derived: co-running, modal superposition, finite element incorporated into the MBS model and finite element coupled to MBS using a co-simulation approach. For the different track models, the difference in modelling technique, results, simulation time, and suitability for different simulation tasks is compared. A good agreement is found between the different track model formulations for wheel–rail contact forces and rail displacements. This study found a better agreement between co-running and structural track models compared to previous studies in the prediction of wheel–rail contact forces. This appears to be due to the increased complexity of co-running track model used in this study together with a tuning of the co-running track model to the reference model in a wider frequency range. For the reader interested to reproduce the results in this paper, the reference track model is available for download. [ABSTRACT FROM AUTHOR]

Owing to the wide acceptance of fiber reinforced composites in the lightweight structure industry, the need to study its thermo‐elastic behavior in dynamical multi‐body systems still remains an open question. Standard continuum models, by virtue of first‐order gradient of deformation, cannot capture curvature effects and hence appropriate extensions of the standard modeling techniques are indispensable to model the accurate physical stiffness. The fiber‐bending curvature are captured by introducing a higher‐order gradient of the deformation as an independent field in the standard continuum. This work explores in detail, a further extension of this continuum to understand the thermal effects on the bending stiffness of fiber bundle in fiber‐reinforced composites. Our proposed model incorporates the temperature of the composite and its bidirectional dependency with the higher‐order gradients of the deformation into the extended mechanical continuum model. The implementation of the model is pursued in the context of multi‐field mixed finite element method and dynamic variational principle. The principle of virtual power enables our extended non‐isothermal continuum to derive an energy‐momentum scheme of higher order. The resulting time‐integrator exhibits physically consistent locking‐ free numerical behavior in dynamical simulations. Our novel approach is illustrated by simple transient dynamic simulations with a hyperelastic, transversely isotropic, polyconvex material behavior. We investigate the conservation of total energy and total momentum in the framework of thermo‐elasticity and study the spatial and temporal convergence for long‐term dynamic simulations with coarser grids and increased accurate numerical solutions. [ABSTRACT FROM AUTHOR]

With the plethora of data on how CFRP layers enhance RCs under static loads, research on how the reinforced structural components react to unequal lateral impact loads from a derailed train striking metro station columns or a car accident is lacking. A similar motivation inspired the current study, which sought to create a numerical technique backed by actual testing to evaluate RC members with CFRP in a range of unequal lateral impact scenarios. This paper uses explicit nonlinear finite element techniques to numerically analyze the response of unequal lateral impact‐loaded RC members wrapped in (CFRP) layers. Diverse variables related to CFRP, concrete, steel reinforcement, and impact energy are investigated. This kind of thorough analysis provides unique insights to strengthen RC members against unequal lateral impact loads. The effects of internal forces and deflections, as well as absorbed energy on the impact response of CFRP‐RC components, were investigated and verified by prior experimental results. A parametric sensitivity analysis was conducted after the strain characteristics of steel bars confirmed the finite element model, reinforcement ratio, impact velocity, CFRP properties, and ductility index all influence the member's impact response. This study's results will help advance the field's understanding of CFRP‐RC components analysis and design under unequal lateral impact. [ABSTRACT FROM AUTHOR]

Since it is difficult to balance the speed and accuracy of the finite element simulation model of cutting processing, a dynamic mesh refinement algorithm for 3D finite element model is proposed. The functions of the algorithm include mesh refinement area judgment, mesh refinement and transfer of physics fields between new and old meshes. The algorithm is applied to the turning simulation of Ti2AlNb with the secondary development of Abaqus using Python, and the accuracy of the simulation model is verified through experiments. Compared with the simulation results of the local mesh refinement, the simulation using dynamic mesh refinement increases 7.3% in cutting force solution error and increases 0.2% in maximum stress solution error, with an increased 174.2% solution speed. The simulation operation speed is effectively improved while ensuring the calculation accuracy. [ABSTRACT FROM AUTHOR]

Magnesium alloys are one of the highly promising structural metals. hcp structure makes it less plastic at room temperature, which greatly limits the development of magnesium alloys. The problem of poor plastic deformation of magnesium alloy can be solved by grain refinement methods, and equal channel angle pressing is one of the more effective methods in grain refinement. In this paper, two-dimensional dynamic simulation of equal channel angle pressing of magnesium alloy is carried out by using finite element software DEFORM F2TM. The deformation of magnesium alloy with different of die angles and die corner angles was analyzed. The results show that in the main deformation zone, when the die angles are different, the deformation of the workpiece in the horizontal direction is very uniform. However, in the longitudinal direction of the workpiece, the larger the die angle is, the more uniform the workpiece deformation is. The die corner angle has no significant effect on the uniformity of workpiece deformation in the longitudinal direction, but it has an effect on the dead zone area and workpiece warpage. The dead zone area and workpiece warpage increase with the increase of die angle. [ABSTRACT FROM AUTHOR]

This paper aims to study the penetration effect of harpoons on space debris to ensure the sustainable development of the space environment and solve the increasingly serious space debris problem. Firstly, a harpoon system was designed to capture space debris. Secondly, based on the Johnson–Cook dynamic constitutive model and fracture failure criterion, the finite element models of aluminum alloy plates were established. Then, the ballistic limit theory for the aluminum alloy target predicted the minimum launch velocity of the harpoon. Finally, the validation experiment was set up to verify the correctness of the model. The results show that the error between the simulation results of the speed for the harpoon embedded in the target and the theoretical results of the ballistic limit is 9.1%, which provides guidance for active space debris removal technology. [ABSTRACT FROM AUTHOR]

Neuronavigation is a computer-assisted technique for presenting three-dimensional images of a patient's brain to facilitate immediate and precise lesion localization by surgeons. Neuronavigation systems use preoperative medical images of patients. In neurosurgery, when the dura mater and arachnoid membrane are incised and the cerebrospinal fluid (CSF) drains out, the brain loses the CSF buoyancy and deforms in the direction of gravity, which is referred to as brain shift. This brain shift yields inaccurate neuronavigation. To reduce this inaccuracy, an intraoperative brain shift should be estimated. This paper proposes a dynamic simulation method for brain-shift estimation combining the moving-particle semi-implicit (MPS) method and the finite element method (FEM). The CSF was modeled using fluid particles, whereas the brain parenchyma was modeled using finite elements (FEs). Node particles were attached to the surface nodes of the brain parenchyma in the FE model. The interaction between the CSF and brain parenchyma was simulated using the repulsive force between the fluid particles and node particles. Validation experiments were performed using a gelatin block. The gelatin block was dipped into silicone oil, which was then gradually removed; the block deformation owing to the buoyancy loss was measured. The experimental deformation data were compared with the results of the MPS-FEM coupled analysis. The mean absolute error (MAE) between the simulated deformation and the average across the four experiments was 0.26 mm, while the mean absolute percentage error (MAPE) was 27.7%. Brain-shift simulations were performed using the MPS-FEM coupled analysis, and the computational cost was evaluated. [ABSTRACT FROM AUTHOR]

Significant effects of the bolt arrangement on the contact characteristics of bolted joints have been demonstrated, which are strongly associated with the dynamic performance of mechanical structures. However, the complexity of interfacial pressure distribution and the randomness of surface microtopography bring challenges to the accurate characterization of the multi-scale contact mechanics. Herein, a hybrid method combining fractal theory with the finite element method (FT-FEM) is proposed, which formulates the interfacial contact evolution in the elastic, elastic-plastic, and fully plastic stages. The complementarity of these two methods makes it possible to reveal the contact mechanism at both micro and macro scales and overcomes difficulties in reflecting the detailed joint contact characteristics in the overall dynamic model. To explore broader implications, FT-FEM is applied to the optimal design of bolt arrangement in an ultra-precision machine tool. Good agreements in calculation results and experimental data validate the accuracy of the proposed FT-FEM and the dynamic simulation. Replacing 15-M10 bolts with 19-M8 bolts results in a 2.9% enhancement in the contact stiffness and a 2.283% attenuation in the vibration response of the workpiece. The results also show that adjusting the bolt arrangement according to the working condition can strengthen the bolted joint effectively. FT-FEM contributes to solving contact problems in various mechanical structures, and the findings have wide practical applications in bolt arrangement optimization. [Display omitted] • A hybrid method for bolted joint modeling considering multi-scale contact mechanics. • New method combines improved fractal theory and finite element method. • Bolt arrangement optimization is carried out applying the method in dynamic analysis. • Experimental validation is done with bolted structures and machine tool. [ABSTRACT FROM AUTHOR]

• In vivo finite element model of knee lunge was built by dual fluoroscopic imaging system. • The finite element model was validated by experiments of three-dimensional printed model. • The simulation of in vivo knee movements would help the substantial research of knee. Biomechanical modeling of the knee during motion is a pivotal component in disease treatment, implant designs, and rehabilitation strategies. Historically, dynamic simulations of the knee have been scant. This study uniquely integrates a dual fluoroscopic imaging system (DFIS) to investigate the in vivo dynamic behavior of the meniscus during functional activities using a finite element (FE) model. The model was subsequently validated through experiments. Motion capture of a single-leg lunge was executed by DFIS. The motion model was reconstructed using 2D-to-3D registration in conjunction with computed tomography (CT) scans. Both CT and magnetic resonance imaging (MRI) data facilitated the development of the knee FE model. In vivo knee displacements and rotations were utilized as driving conditions for the FE model. Moreover, a 3D-printed model, accompanied with digital imaging correlation (DIC), was used to evaluate the accuracy of the FE model. To a better inner view of knees during the DIC analysis, tibia and femur were crafted by transparent resin. The availability of the FE model was guaranteed by the similar strain distribution of the DIC and FE simulation. Subsequent modeling revealed that the compressive stress distribution between the medial and lateral menisci was balanced in the standing posture. As the flexion angle increased, the medial meniscus bore the primary compressive load, with peak stresses occurring between 60 and 80° of flexion. The simulation of a healthy knee provides a critical theoretical foundation for addressing knee pathologies and advancing prosthetic designs. [ABSTRACT FROM AUTHOR]

Camera attitude control systems for robots require a compact structure and high responsiveness. However, due to the combination structure of several actuators, the camera attitude control system is large. To address this issue, this study proposes a three-degree-of-freedom (3DOF) voice coil actuator. A single actuator is used to generate 3DOF motion, which is driven by a four-phase current. This study also describes the basic structure and operating principle of the actuator and clarifies the torque characteristics using a three-dimensional (3D) finite element method (FEM). Furthermore, the dynamic modeling and control methods are presented. The FEM and dynamic simulation results reveal that the proposed actuator can be arbitrarily driven in 3DOF. [ABSTRACT FROM AUTHOR]

A 3D dynamic finite element model is developed to study the response of the existing tunnels' concrete structure under the influence of different train speeds and undercrossing with fixed shield excavation. The intersection area of Metro Line 3 in Guangzhou and the intercity railway between Foshan and Dongguan is used as the case study. A programming idea simulating oblique moving-axle loads in the numerical model by using function expressions to constrain activity area is proposed. The Hilber–Hughes–Taylor time-integration scheme is used to calculate the dynamic response parameters of the double-channel rectangular cross section tunnels. Considering fixed excavation steps in the process of shield crossing, acceleration and deformation of the existing tunnels were analyzed under the moving-axle loads of trains at different speeds. From the perspective of the vibration and deformation of existing tunnels, shield excavation and moving speed have their own emphasis on the dynamic influence of the existing tunnel. In addition, the calculation results of the numerical simulation are in good agreement with the data obtained from some field tests, which further verifies the reliability of the calculation method of the numerical model. The results of this research can guide the arrangements for reinforcement measures for existing tunnels in the later stage. [ABSTRACT FROM AUTHOR]

Aluminum alloy high-speed milling is commonly utilized in the aircraft, aerospace, mold, and other sectors, and its cutting force characteristics will have an important impact on the final machining quality of parts. The cutting force characteristics of high-speed milling of an aluminum alloy workpiece using a ball end milling cutter were investigated in this research. A three-dimensional finite element dynamic simulation model was developed for the high-speed milling of ball-end milling cutters. Firstly, the benefit of tool axis vector inclination angle in multi-axis machining was discussed, and the inclination angle of the tool axis vector in multi-axis machining was characterized more precisely. The three-dimensional model of the ball-end milling cutter was established according to the actual machining, and in order to simulate the machining process, it was put into a finite element analysis system. The rotation and intermittent cutting of the tool were considered in the simulation process, which was in good agreement with the actual machining process. In a finite element simulation environment, the cutting force under 25 groups of rake inclination angles was simulated, and verification milling tests on a five-axis machine were carried out. According to the results, the general trend of the maximum cutting force in all directions was in good agreement with the experimental results. Finally, the range of the rake inclination angle with less cutting force and more stable cutting force in multi-axis machining was given. The results also confirmed the reliability of the simulation results, and provided a reference for the finite element simulation of other metal cutting processes. [ABSTRACT FROM AUTHOR]

The dynamic vibration absorber (DVA) has a broad application background in slender structure vibration reduction, such as in machine gun systems, micro actuators, and so on. Rapid modeling and simulation of the DVA-beam system are of great importance for dynamic performance, evaluation, and finally, the structural design. The primary motivation for this paper is to present a reliable and convenient technique for the modeling and computation of the DVA-beam system. A novel DVA-beam element, which consists of a beam segment and a DVA, is presented. In this element, the DVA position can be arbitrarily allocated, whether on the beam node or within the beam domain. In this way, the beam can be modeled with a few elements to save on computing costs and maintain ideal modeling accuracy. An element deactivating method, which endows the DVA-beam element with the ability to simulate a bare beam and a DVA-beam structure simultaneously, is proposed. Some numerical examples were carried out to validate the reliability of the DVA-beam element in addressing different kinds of boundary conditions by comparing the beam tip responses with those simulated by ADAMS software, and good agreements were observed. Finally, two DVA optimization examples were conducted to investigate the effectiveness and applicability of the DVA-beam element in engineering optimization. The performance was impressive. [ABSTRACT FROM AUTHOR]

The simulation of the comminution process of a lithium-ion battery model and evaluation of the performance of three cylindrical battery models derived from previous studies were achieved in the present study. The finite element method (FEM) was used along with dynamic simulation procedures. The models were classified based on the battery material model parameters used in the analysis, namely type A, B, and C models. The battery material models of type A and C were unable to provide results that were consistent with real-world circumstances. In contrast, the type B model gives a realistic battery dynamic reaction. Additional testing on the type B model was performed in terms of battery shard size, fracture energy, comminution pressures, element displacement, battery element velocity, and device capacity calculation. The simulation results revealed that the type B model in this study is capable of properly predicting the dynamic response of the battery, notably when compared to the other two models. The study in the present research could be used in the future to identify the proper cutting tool geometry, estimate the size of the comminution product, and play an important role in the design and optimization of the comminution machine. [ABSTRACT FROM AUTHOR]

Dynamic fracture deals with the degradation and failure of materials and structures under conditions where the inertia effect must be included in the analysis. In this contribution, a dynamic description of a simple local damage approach and its detailed finite element implementation is presented towards brittle and quasi-brittle localization failure under time-dependent loading conditions. To eliminate the issue of the mesh-dependence, the softening parameter of the introduced model is controlled through a numerical factor that is determined based on material constants and the element length. The developed local damage model integrated with the smooth Rankine equivalent strain form results in an effective approach as it offers a physically realistic description of the damage localization in quasi-brittle media. The governing equation of the nonlinear behavior, when damage is involved, is spatially discretized by a nonlinear finite element method, and is efficiently solved using the standard Newton–Raphson method, while the popular Newmark-beta time integration method is applied to its time discretization. We also present the estimation of the crack tip velocity and dissipated energy. To show the accuracy and performance of the developed local damage approach, we study the dynamic crack propagation, and fragmentation branching in materials with brittle and quasi-brittle fracture. The obtained results are compared with experimental data and other numerical solutions available in literature. In terms of computational efficiency, the developed approach requires much less computational time than other numerical models in the same class of the smeared damage approach, i.e., gradient-enhanced and phase-field models, since it just needs to solve a single equation of motion. [ABSTRACT FROM AUTHOR]

BACKGROUND: Subspine impingement caused by low anterior inferior iliac spine is often neglected, resulting in missed diagnosis or poor treatment effect in some patients. OBJECTIVE: To compare and analyze the difference of hip joint of patients with anterior inferior iliac spine impingement and those without impingent, to investigate whether conventional X-ray and CT examination can directly or indirectly judge the existence of the low anterior inferior iliac spine. METHODS: Totally 15 patients diagnosed with anterior inferior iliac spine impingement and undergoing hip arthroscopic surgery in First Affiliated Hospital of Jinzhou Medical University from January 2016 to June 2019 were selected as trial group. Fifteen patients with non-iliac anterior inferior iliac spine impingement who underwent standard anteroposterior pelvic X-ray and three-dimensional CT examination of the pelvis were selected as control group. The angle α, the center-edge angle of the hip joint, the Tönnis angle, the neck shaft angle, the anteversion angle of the acetabulum, and the horizontal and vertical distance between the anterior inferior iliac spine and the acetabular anterior edge, and the width of the anterior inferior iliac spine were compared between the two groups using X-ray film and CT examination. Finite element analysis was used to simulate the physiological activities of the hip joint in patients with anterior inferior iliac spine, and to observe the absence and presence of local pressure change. RESULTS AND CONCLUSION: (1) The center-edge angle and the vertical distance of the anterior inferior iliac spine from the acetabular anterior edge of the trial group were smaller than those of the control group, but only the difference of vertical distance value between the groups was statistically significant (P < 0.05). The measured values of other indicators of the patients were slightly greater in the trial group than those in the control group, but the difference was not significant (P > 0.05). (2) Three-dimensional reconstruction of type II anterior inferior spinal impingement showed that anterior inferior iliac spine was proliferative, hypertrophic, and extends downward, but did not protrude to the acetabular anterior edge. The anterior inferior iliac spine gap disappeared. Moreover, the protruding hypertrophic part of the anterior inferior iliac spine did not make obvious contact with the proximal femur during the entire exercise loading process. (3) It is not possible to infer or judge whether there is a low anterior inferior iliac spine through X-ray and CT scans. The imaging diagnosis of the low anterior inferior iliac spine still mainly depends on three-dimensional reconstruction. Patients with anterior inferior iliac spine may not have abnormal contact between the distal end of the anterior inferior iliac spine hypertrophy and the proximal femur. [ABSTRACT FROM AUTHOR]

Human infants are born neurologically immature, potentially owing to conflicting selection pressures between bipedal locomotion and encephalization as suggested by the obstetrical dilemma hypothesis. Australopithecines are ideal for investigating this trade-off, having a bipedally adapted pelvis, yet relatively small brains. Our finite-element birth simulations indicate that rotational birth cannot be inferred from bony morphology alone. Based on a range of pelvic reconstructions and fetal head sizes, our simulations further imply that australopithecines, like humans, gave birth to immature, secondary altricial newborns with head sizes smaller than those predicted for non-human primates of the same body size especially when soft tissue thickness is adequately approximated. We conclude that australopithecines required cooperative breeding to care for their secondary altricial infants. These prerequisites for advanced cognitive development therefore seem to have been corollary to skeletal adaptations for bipedal locomotion that preceded the appearance of the genus Homo and the increase in encephalization. Using finite element models of australopithecine pelvis reconstructions the secondary altricial nature of early hominin newborns is revealed, indicating that the need for cooperative breeding evolved secondary to bipedalism and thus prior to the appearance of the genus Homo. [ABSTRACT FROM AUTHOR]

Human infants are born neurologically immature, potentially owing to conflicting selection pressures between bipedal locomotion and encephalization as suggested by the obstetrical dilemma hypothesis. Australopithecines are ideal for investigating this trade-off, having a bipedally adapted pelvis, yet relatively small brains. Our finite-element birth simulations indicate that rotational birth cannot be inferred from bony morphology alone. Based on a range of pelvic reconstructions and fetal head sizes, our simulations further imply that australopithecines, like humans, gave birth to immature, secondary altricial newborns with head sizes smaller than those predicted for non-human primates of the same body size especially when soft tissue thickness is adequately approximated. We conclude that australopithecines required cooperative breeding to care for their secondary altricial infants. These prerequisites for advanced cognitive development therefore seem to have been corollary to skeletal adaptations for bipedal locomotion that preceded the appearance of the genus Homo and the increase in encephalization. Using finite element models of australopithecine pelvis reconstructions the secondary altricial nature of early hominin newborns is revealed, indicating that the need for cooperative breeding evolved secondary to bipedalism and thus prior to the appearance of the genus Homo. [ABSTRACT FROM AUTHOR]

High temperature superconducting (HTS) maglev transportation has provided a new development direction for high-speed and ultra-high-speed rail transit. In order to promote the development of HTS materials in this area, the dynamic response of the vehicle superconductor under an alternating magnetic field with high frequency is well-worth studying. However, limited by some experimental conditions and other factors, the effective modelling method becomes an indispensable and cost-effective tool to predict the electromagnetic properties of the superconductors. In this paper, based on the single-peaked permanent magnet guideway (PMG)-HTS bulks maglev configuration, the modelling using three different E-J relationships include the power law model (PLM), the flux flow and creep model (FFCM), and the flux flow model (FFM) are compared. Results indicate that the PLM has the highest computational efficiency and good reliability. Then, using the PLM, we further study the dynamic response of the HTS bulks over a Halbach-typed PMG under higher vibration frequencies. The effect of the magnet failure in the middle of the PMG on the levitation system is also discussed. A finite element method is applied with the H formulation. The moving mesh is used to realize the relative displacement between the PMG and HTS bulks. To investigate the temperature rise and the AC loss inside the HTS bulks, the Heat Transfer module is coupled. Results show that the temperature inside the HTS bulks will decay exponentially with time if the magnitude and frequency of the external magnetic field do not continue to increase. This work can provide some references for the future practical applications of the high-speed HTS maglev. [ABSTRACT FROM AUTHOR]

Human infants are born neurologically immature, potentially owing to conflicting selection pressures between bipedal locomotion and encephalization as suggested by the obstetrical dilemma hypothesis. Australopithecines are ideal for investigating this trade-off, having a bipedally adapted pelvis, yet relatively small brains. Our finite-element birth simulations indicate that rotational birth cannot be inferred from bony morphology alone. Based on a range of pelvic reconstructions and fetal head sizes, our simulations further imply that australopithecines, like humans, gave birth to immature, secondary altricial newborns with head sizes smaller than those predicted for non-human primates of the same body size especially when soft tissue thickness is adequately approximated. We conclude that australopithecines required cooperative breeding to care for their secondary altricial infants. These prerequisites for advanced cognitive development therefore seem to have been corollary to skeletal adaptations for bipedal locomotion that preceded the appearance of the genus Homo and the increase in encephalization. Using finite element models of australopithecine pelvis reconstructions the secondary altricial nature of early hominin newborns is revealed, indicating that the need for cooperative breeding evolved secondary to bipedalism and thus prior to the appearance of the genus Homo. [ABSTRACT FROM AUTHOR]

In this paper, an efficient numerical scheme is proposed to simulate the high-frequency dynamic mechanical response of single-crystalline Ni–Mn–Ga samples. First, based on a three-dimensional setting, the governing equation system for a single-crystalline Ni–Mn–Ga sample is set up, which is composed of the equation of motion and the twin interface movement criteria. In order to solve the governing system, an iterative numerical algorithm is proposed, in which the finite element method and the NewMark-β method are applied. To demonstrate the efficiency of this numerical scheme, the response of a single-crystalline Ni–Mn–Ga sample under some typical loading conditions are studied. In the numerical simulations, a specific discretisation of the sample is adopted, such that the possible positions of the twin interfaces in the sample can be naturally inherited. With the obtained numerical results, the mechanical behaviours of the sample under the different loading conditions are predicted, which show good consistency with the experimental results. The distribution of variant state and the propagation of twin interfaces in the sample can also be simulated. The numerical scheme proposed in the current work is helpful for the design of novel sensors or actuators based on single-crystalline Ni–Mn–Ga alloys. [ABSTRACT FROM AUTHOR]

The macaw palm (Acrocomia aculeata) is a palm tree native to tropical forests that stand out due to its great potential for oil production. This study was developed with the objective of constructing a high-fidelity model of the macaw palm fruit-rachilla system for the purpose of simulating its dynamic behavior when subjected to mechanical vibrations. The finite element method was used to determine the natural frequencies and modes of vibration of the system. The three-dimensional models of the fruit-rachilla systems were elaborated using CAD3D Fusion 360 software. The modal properties of the fruit-rachilla systems were obtained based on the models developed by varying the elasticity modulus values of the system. The parameters of greatest influence in the estimation of natural frequencies are the elasticity modulus, especially that of the fruit-rachilla joint, and the specific mass. The models that take into account the three-dimensional strains along the rachilla are the least sensitive to variations in the mechanical properties (elasticity modulus and specific mass) and are shown to be more representative of the actual physical system. [ABSTRACT FROM AUTHOR]

In this study, lignocellulose-derived aerogel (LA) with compression-rebound was synthesized from liquefied wood through sol-gel polymerization, aging and freeze-drying process. The results presented a gradual increase in the compressive strength, flexural strength, and maximum decomposition temperature of the LA sample with prolonged aging time from 3 to 10 h, demonstrating excellent elasticity and thermal stability. After more than 10 h, the bending strength began to decrease, indicating that the material's rigidity was greater than its elastic toughness at this time. A nonlinear viscoelastic constitutive model based on the Ogden function and parallel rheological framework showed very high correlation with experimental measurement results, and also demonstrated admirable mechanical properties. These predictions can provide an effective approach for the application of LA in buffer packaging. [Display omitted] • Lignocellulose-derived aerogels for buffer packaging was successfully obtained. • Appropriate aging time improved thermal stability and mechanical properties of LA. • High bending strength of 2.64 MPa at 50 % compression strain can be obtained. • LA-E4 achieved excellent compression rebound rate of 96.15 %. • A viscoelastic constitutive model for predicting mechanical behavior was established. [ABSTRACT FROM AUTHOR]

In this paper, a novel numerical simulation approach based on the finite element method for dynamically modeling the excavation process of shield tunneling is proposed, with the shield-ground interactions well captured. This method is capable of mimicking the alternating modes of advancing and stopping of a shield boring machine during underground construction, with the important effects of the cutterhead rotation and slurry support pressure considered. Under the cutting action, the soil at the excavation face would experience irreversible deformation and damage, such that additional support needs to be provided by the cutterhead blades and slurry to maintain stability. The impacts of key construction parameters are examined, including cutterhead rotary speed, advance rate, and slurry support pressure, on shield tunneling operations and ground responses. The numerical model is rigorously validated against physical model experiments. This work provides useful insights into the mechanistic processes in the stratum during shield tunneling, including the spatiotemporal evolution of ground deformation patterns and stress redistributions. The results offer valuable guidance for optimizing shield tunneling operations and enhancing tunneling safety and efficiency. [ABSTRACT FROM AUTHOR]

• A damage localization and quantification method without damage labels is proposed. • An efficient method to quantify bridge damage severity level is proposed. • An efficient method for generating damaged structure dynamic responses is proposed. Among the existing unsupervised bridge damage detection methods, it is difficult to quantify bridge damage severity levels, although some of the methods can achieve the localization of bridge damage. In the existing research, the damage index (DI) curve is calculated by the monitoring point dynamic response (inclination or deflection) of the bridge in the damage state, and the localization of the bridge damage can be achieved by the DI curve without the need for damage labels. Based on this bridge damage localization method, this paper proposes an efficient bridge damage severity level quantification method. Since the different DI curves calculated under the same damaged state basically coincide with each other, the DI curves will change with the bridge-damaged state. Therefore, the quantification of the bridge damage severity level is achieved by only calculating DI curves of different damage degrees at the damage location. To efficiently calculate the DI curve, this paper proposes a method for generating the monitoring point dynamic response of the specified damage bridge. By the specified damage bridge finite element model (FEM) static simulation to obtain arbitrary vertical nodal loads and monitoring point responses of the relationship function, and then combined with the healthy state of the bridge monitoring point dynamic response can be generated monitoring point dynamic response of the specified damage bridge. Since the method in this paper is based on real measured data to calculate the DI curve, it is more robust to noise and modeling errors than the FEM dynamic simulation method, and the modeling of this method only needs to update the model stiffness parameter to reduce the modeling cost. In the example of this paper, the method of this paper calculates the DI curve of one damage state only needs about 7 s about 437 times the computational efficiency of the FEM dynamic simulation method, which can achieve the fast quantification of bridge damage severity levels. Numerical simulations demonstrate that the method can localize and quantify multi-damage in bridges under unknown loads, a small number of sensors, noise, and modeling errors. However, the method in this paper still has limitations that do not apply to the localization and quantification of bridge pier damage and nonlinear models. [ABSTRACT FROM AUTHOR]

The problem of slope vibration induced by flood discharge of high dams cannot be ignored. In this paper, this problem is simplified to be the relationship among the fluctuating pressures, the inherent properties of the slope system, and its dynamic responses. The characteristics of fluctuating pressures in the plunge pool during flood discharge are analyzed by the hydraulic model test. And a numerical slope model consisting of the finite element domain and the PML domain is established to study the inherent characteristics and vibration responses by numerical simulation. The results show that the flow fluctuation in plunge pool is a continuous and stable random vibration process. And the fluctuating pressures on the bottom area of the plunge pool are greater than that of the sidewall, but the fluctuation phenomenon at the sidewall is more intense. In addition, the slope displacement vibration intensity caused by fluctuating pressures is small, only at the micron level. The fluctuating pressures on the bottom area of the plunge pool are the dominant factor affecting the kinetic energy density distribution of the slope. This work provides a simple and efficient method for the study of slope vibration induced by high dam flood discharge. [ABSTRACT FROM AUTHOR]

Strike-slip faults can be nonplanar in both their strike and dip dimensions. While a large body of work has investigated the effects of changes in strike on earthquake rupture and arrest, no previous studies have investigated the role of along-strike variations in dip on strike-slip ruptures. Here, I use the three-dimensional finite-element method to conduct dynamic simulations of ruptures on strike-slip faults with linear surface traces and changes in dip along strike. I experiment with the amount of dip change as well as the abruptness of that change under a variety of initial stress conditions. In all of my initial stress cases, I find that a change in dip along strike can cause rupture to stop, and that larger dip changes over shorter distances are more likely to do so. This is largely due to the change in strike at depth that inherently comes from changing the dip; the majority of these behaviors are a result of the rupture front being forced to change direction mid-rupture. While some dip-slip movement does occur on the nonvertical parts of the model fault, it does not have a significant effect on rupture extent. However, linear-surface-trace, nonvertical-dip faults do produce different surface slip, stress, and ground motion patterns compared to corresponding nonlinear-strike, vertical-dip faults. Together, my results show that changes in dip along strike-slip faults do considerably impact the rupture process, suggesting that this type of geometrical complexity should be considered in rupture forecasts and hazard assessments. [ABSTRACT FROM AUTHOR]

In this work, a model is proposed for the computation of unbalanced magnetic pull (UMP) in PM machines. This model is suitable for use in dynamic simulations. However, the aim of this research is not dynamic modeling of the PM machines. The main idea is to provide a fast model to be integrated into the dynamic models of PM machines. To reduce the required computational burden, the UMP of PM machines is expressed as a second-order algebraic vector function of the stator currents. The function parameters are estimated by post-processing of the results of some magneto-static simulations. These parameters are functions of the machine geometrical data and the rotor position. The role of these parameters in the computation of the machine UMP is the same as the role of the machine inductances in computation of the electromagnetic torque. To investigate the capability of the developed model, the UMP of a concentric fractional-slot surface PM machine with diametrically asymmetric stator windings and the UMP of an eccentric PM-inset machine are predicted. The obtained results are compared in terms of the consumed time and the accuracy by means of finite element analysis. [ABSTRACT FROM AUTHOR]