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The unique structure of nacre is composed of 'bricks' and 'mortar,' which gives it excellent damage resistance. In this study, nacre-like bionic ceramic scaffolds were 3D-printed using vat photopolymerization (VPP) technology, filled with polymer, and reinforced with carbon fiber to create high-strength and high-toughness carbon fiber-reinforced bionic composites. This approach leverages additive manufacturing technology to easily overcome the challenges of fabricating complex bionic structures with a simple and flexible production process. It offers a practical method for developing other lightweight, high-strength, and tough bionic materials. The microstructure of the composites was observed using scanning electron microscopy and energy dispersive spectroscopy. Additionally, finite element method and molecular dynamics simulations were performed on the composites. The results indicate that the composite material increased the flexural strength by 293.52 % and the fracture toughness by 109.36 % compared to solid ceramic parts. The primary toughening mechanisms of carbon fiber include crack deflection, fiber "pull-out," and "debonding" within the composite. [Display omitted] • Nacre-like biomimetic composites were fabricated via vat photopolymerization. • Effects of various fillers on flexural properties were investigated. • Atomic-level insights on biomimetic structures were offered by molecular dynamics. • Finite element method reveals filler interaction with the nacre scaffold. [ABSTRACT FROM AUTHOR]

• A partitioned fluid-structure interaction (FSI) framework is developed. • The meshless Vector Form Intrinsic Finite Element (VFIFE) is innovatively used as a solid solver. • Various benchmarks involving vortex-induced vibration phenomena are studied with the new algorithm. • Strong adaptability and accuracy of the VFIFE method are proved by numerical results. • An experimental case of flow past flexible curtain in a water tank is investigated. The Vector Form Intrinsic Finite Element (VFIFE) is an advanced meshless Lagrangian structural solver. This study introduces a partitioned framework to integrate Arbitrary Lagrangian-Eulerian and VFIFE methods into fluid-structure interaction (FSI) problems featured by large structural displacements and deformations. The VFIFE method enables the FSI simulations with deformable structures due to the nature of Lagrangian particles, which is challenging for traditional computational fluid mechanics techniques. In addition, the VFIFE can be effectively equipped with the partitioned coupling schemes because of the versatility of governing equations. In this algorithm system, several matrix problems in finite element methods and mapping and interpolation in the fluid-structure interface can be avoided. The significant potential of this algorithm in tackling complex FSI problems is demonstrated through various benchmarks, encompassing scenarios like Taylor-Green vortex, flow over a rigid cylinder (Re = 40 ∼ 200), forced vibration of a rigid cylinder, vortex-induced vibration (VIV) of an elastically mounted cylinder, and VIV of a rigid cylinder with an attached flexible cantilever beam. Finally, an experiment on flow past a curtain in a water tank is conducted to further evaluate the precision and stability of the current coupling strategy in three dimensions, demonstrating the feasibility of such methods in flexible structures. [ABSTRACT FROM AUTHOR]

In micro-LED chip repair, a nanopositioner is commonly used to adjust the positioning of the LED chip. However, during the bonding process, the heat generated can cause the positioning system to deform, leading to inaccurate alignment and poor-quality chip repair. To solve this issue, a novel flexible connection structure has been proposed that can eliminate thermal deformation. The principle of this novel flexible connection structure is that the thermal distortion self-elimination performance is achieved via three flexible connection modules (FCM) so that the thermal stress is automatically eliminated. First, the paper introduces the principle of thermal deformation elimination, and then the design and modeling process of the proposed structure are described. A heat transfer model is then developed to determine how temperature is distributed within the structure. A thermal deformation model is established, and the size of the FCM is optimized using a genetic algorithm (GA) to minimize the thermal deformation. Finite element analysis (FEA) is used to simulate and evaluate the thermal distortion self-elimination performance of the optimized mechanism. Finally, experiments are conducted to verify the reliability and accuracy of the simulation results. The simulations and experiments show that the proposed structure can eliminate more than 38 % of the thermal deformation, indicating an excellent thermal deformation self-eliminating capability. [ABSTRACT FROM AUTHOR]

Purpose: This study is an attempt to illustrate and discuss multi-hazard interactions in vibration control of long-span bridges subjected to wind and seismic loads. Such bridges, being flexible structures, are inherently vulnerable to wind loads. However, some response parameters of such bridges, for example, tower and deck acceleration, can be significant during large earthquakes which produce ground motions with low-frequency content. Methods: To illustrate this problem, a case study of the Runyang Suspension Bridge (RSB) is used. A finite element model of the bridge is created and verified against published literature. A set of ground motions from large worldwide earthquakes and spatially varying wind velocity time series, simulated as a realization of a random field, are used to evaluate the bridge's dynamic response with and without control devices. The control devices applied in this study are passive-tuned mass dampers (TMDs). Careful investigation of the uncontrolled response of the bridge shows that while wind load is mainly important for the displacement of the bridge deck, seismic loads can induce significant acceleration of the tower and the deck. Since the response of the tower and the deck are coupled at some higher modes of vibration, seismic action, although most critical for the tower, is also relevant for deck acceleration. These observations indicate the need for a multi-performance-based control strategy. Results: It is found that TMDs optimal for reducing seismic-induced deck acceleration can lead to amplification of wind-induced deck displacement. At the same time, TMDs optimal for reducing wind-induced displacement response are, in some cases, harmful to seismic-induced deck acceleration. These results clearly show multi-hazard interaction in control performance. Conclusions: To account for this problem, a control strategy for the deck and tower's seismic and wind responses is investigated. This consists of TMDs placed at the top of each tower and 4 TMDs placed on the deck. By tuning the TMDs to different vibration modes of the bridge, the system is shown to be effective for both seismic and wind actions. [ABSTRACT FROM AUTHOR]

The large-span, relaxed antenna network is a large deformation flexible structure due to its low pre-tension level of the wires. Its dynamic analysis under a wind load belongs to dynamic and geometric nonlinear problems, which is very complex to accurately calculate and solve. This paper explores the possibility of the finite particle method (FPM) to the aeolian vibration analysis of a large-span, low stress-tensioned antenna cable net. In the FPM, the antenna network structure is discretized into a group of finite particles, where the motions of all particles follow Newton's second law and can be solved dynamically using a central difference scheme. The effectiveness and applicability of the FPM were verified by comparing the calculation results of the finite element method and FPM. The FPM was used to study the effects of wind speed and the distribution of vibration on the aeolian vibration of antenna cable nets. The results showed that this method is suitable for studying the aeolian vibration of a large-span, low stress-tensioned antenna network and has high computational efficiency and accuracy. [ABSTRACT FROM AUTHOR]

Accurate pavement design and evaluation requires the execution of response analysis. Pavement materials' behavior does not necessarily conform to the assumptions of the multi-linear elastic theory usually adopted during pavement analysis. In particular, the unbound granular materials located in the base and sub-base layers behave in a nonlinear elastic manner, which can be captured through advanced constitutive modeling of their resilient modulus. The finite element method enables us to code constitutive models and quantify potential variations in pavement responses because of different mechanistic assumptions. In this study, variations in response are investigated for a typical structure of a flexible pavement considering the nonlinear anisotropic behavior of the unbound materials together with their initial stress–strain state. To demonstrate the impact of their behavior on the outcome of pavement analysis, variable asphalt concrete layer thicknesses and moduli are assumed, such that they cover a large spectrum of roadways. It was found that pavement responses can be calculated up to 3.5 times higher than those retrieved from the conventional linear analysis. This comparison means that the alterative mechanistic modeling of the unbound granular materials can be proved to be more conservative (i.e., leading to higher strains) in terms of pavement design and analysis. From a practical perspective, this study alerts pavement scientists and engineers engaged in pavement design to a more reliable performance prediction, which is needed to bridge the gap between advanced modeling and routine analysis. [ABSTRACT FROM AUTHOR]

Lattice high-molded support can generally be used for cast-in-place support for bridges, but for more than 50 meters of lattice high support, due to the wind, load and other factors, due to the support length and slenderness of the relatively large, relatively light and flexible structure and other characteristics of the role of the wind load is very sensitive. When the lattice high-molded stent construction is used in the typhoon area, it is easy to be damaged by the typhoon, and the structural design of the lattice high-molded stent and the construction of that technology are facing great challenges. In this paper, based on the new construction of a special bridge in Fujian, finite element analysis of four-legged and six-legged lattice bracing is carried out by ANSYS, and the effects of steel pipe diameter, number of columns, longitudinal and transversal spacing of bracing, and diagonal bracing structural parameters on structural performance are analyzed by using the coefficients of buckling stability and the coefficients of critical loading. The results of the study show that the main design variable for displacement sensitivity is the diameter of vertical rod; the main design variable for stress sensitivity is the diameter of diagonal rod; the main design variable for overall stability sensitivity is the diameter of diagonal rod; and the main design variable for overall stability sensitivity of total volume is the diameter of diagonal rod. And the optimal wind resistance parameters are: 4 lattice high-braced columns are selected, the section length should be controlled within 15m, and the total height should not be more than 70m, and the spacing of the columns is controlled between 7m and 8m. This study proposes a set of optimized design process method for wind-resistant lattice structure under the constraints of stiffness, strength and critical load factor, which improves the economy and ensures the reasonableness of the design, and can be used for the design of high-modular lattice bracket in typhoon area. [ABSTRACT FROM AUTHOR]

As spectral resolution increases, the dimension of the Doppler Asymmetric Spatial Heterodyne (DASH) interferometer increases. The existing approach for stably mounting the interferometer is limited to mounting a normal-sized DASH interferometer. In this study, a novel and stable structure is proposed, with its effecti1veness exemplified for a near-infrared (NIR) DASH interferometer. The mathematical model of a flexible structure was established. The parameters of the support structure were optimized by requiring the mechanical stress of the flexible structure and shear stress at the bonding surface to be less than the strength value. The spring constants were optimally designed to adjust natural frequency and minimize stress. The finite element analysis (FEA) results show that the maximum mechanical stress was 65.56 MPa. The maximum shear stress was 3.4 MPa. All stress values had a high safety margin. The mechanical material and adhesive area were optimally designed. Therefore, the thermal resistance of the structure was improved by 7.5 times. The test results indicate that the proposed flexible support structure could satisfy the requirements of the launch environment. The results from FEA and vibration tests were consistent with the model calculation results. Compared to existing structures, the mechanical performance and thermal resistance were improved. [ABSTRACT FROM AUTHOR]

Clustered tensegrity structures integrated with continuous cables are lightweight, foldable, and deployable. Thus, they can be used as flexible manipulators or soft robots. The actuation process of such soft structure has high probabilistic sensitivity. It is essential to quantify the uncertainty of actuated responses of the tensegrity structures and to modulate their deformation accurately. In this work, we propose a comprehensive data-driven computational approach to study the uncertainty quantification (UQ) and probability propagation in clustered tensegrity structures, and we have developed a surrogate optimization model to control the flexible structure deformation. An example of clustered tensegrity beam subjected to a clustered actuation is presented to demonstrate the validity of the approach and its potential application. The three main novelties of the data-driven framework are: (1) The proposed model can avoid the difficulty of convergence in nonlinear Finite Element Analysis (FEA), by two machine learning methods, the Gauss Process Regression (GPR) and Neutral Network (NN). (2) A fast real-time prediction on uncertainty propagation can be achieved by the surrogate model, and (3) Optimization of the actuated deformation comes true by using both Sequence Quadratic Programming (SQP) and Bayesian optimization methods. The results have shown that the proposed data-driven computational approach is powerful and can be extended to other UQ models or alternative optimization objectives. [ABSTRACT FROM AUTHOR]

Purpose: Tactile sensation is an important sensory function for robots in contact with the external environment. To better acquire tactile information about objects, this paper aims to propose a three-layer structure of the interdigital flexible tactile sensor. Design/methodology/approach: The sensor consists of a bottom electrode layer, a middle pressure-sensitive layer and a top indenter layer. First, the pressure sensitive material, structure design, fabrication process and circuit design of the sensor are introduced. Then, the calibration and performance test of the designed sensor is carried out. Four functions are used to fit and calibrate the relationship between the output voltage of the sensor and the contact force. Finally, the contact force sensing test of different weight objects and the flexible test of the sensor are carried out. Findings: The performance test results show that the sensitivity of the sensor is 0.93 V/N when it is loaded with 0–3 N and 0.23 V/N when it is loaded with 3–5 N. It shows good repeatability, and the cross-interference between the sensing units is generally low. The contact force sensing test results of different weight objects show that the proposed sensor performs well in contact force. Each part of the sensor is a flexible material, allowing the sensor to achieve bending deformation, so that the sensor can better perceive the contact signs of the grasped object. Practical implications: The sensor can paste the surface of the paper robot's gripper to measure the contact force of the grasping object and estimate the contour of the object. Originality/value: In this paper, a three-layer interdigital flexible tactile sensor is proposed, and the structural parameters of the interdigital electrode are designed to improve the sensitivity and response speed of the sensor. The indenter with three shapes of the prism, square cylinder and hemisphere is preliminarily designed and the prism indenter with better conduction force is selected through finite element analysis, which can concentrate the external force in the sensing area to improve the sensitivity. The sensor designed in this paper can realize the measurement of contact force, which provides a certain reference for the field of robot tactile. [ABSTRACT FROM AUTHOR]

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

A prestressed cable net structure is applied to shape and support the reflective surface of mesh antennas. The radiation pattern of an antenna highly depends on the positions of the cable net nodes. The pretension force and node positions of the cable net structure are strongly coupled. The deformation of the flexible support frame changes the positions of the cable net nodes, causing the radiation pattern to deteriorate. To achieve high node position precision, this study proposes the pretension design method of a cable net structure with flexible supports. To improve calculation efficiency, finite element method and force density method are combined to calculate structural deformation directly and accurately. Furthermore, a pretension optimization model is established by considering the rigid body displacements of the nodes. This model is solved iteratively. Numerical results show that the proposed pretension design method can achieve high design accuracy for a flexible support cable net structure and significantly improve the mechanical properties of a support frame. [ABSTRACT FROM AUTHOR]

Broadband motion control in flexure-based stages can benefit from passive damping enhancement at their flexible structures. This paper develops a damped two-axis axially collocated (2-AC) flexure hinge with damping-enabling hybrid inserts and analytically derives its loss factor model based on hybrid (empirical and analytical) compliance modeling and shearing damping modeling. The analytical loss factor model is verified by finite element analysis. It is seen that the geometric parameters of the diameter and slope angle of the insert are sensitive to the hinge's loss factor based on the theoretical loss factor model, especially in low-frequency and resonant zone. The actual experiments and finite element simulation indicate that embedding the hybrid inserts into the 2-AC flexure hinge can improve the damping performance of the hinge. [ABSTRACT FROM AUTHOR]

Cable-membrane reflector is a highly nonlinear flexible structure, which can represent a specific surface shape under the proper combination of cable tension and membrane stress. AstroMesh reflector is a representative of cable membrane reflector, which has advantages of large aperture, easy folding, and light weight, and is increasingly utilized in space antenna reflectors. In this paper, a finite element model of the cable-membrane structure is established together with the corresponding incremental equilibrium equation which provides the sensitivity of the nodal position with respect to the geometric parameter of the cables and triangular membranes. A form-finding strategy is detailed, which aims at a configuration with the reflector nodes locating on a specified paraboloid while all cables and membranes are tensioned uniformly as possible. In addition, the surface precision of the reflector is reduced due to the inevitable errors in the manufacturing process. Therefore, the tension ties in the cable network is designed to be adjustable to solve this problem. Carefully changing the length of these cables can increase the reflector surface precision, which is referred as shape adjustment. An adjustment strategy with model updating is proposed. The model updating using the measured positions of the reflector nodes can dramatically reduce the discrepancy of the finite element model with respect to the actual reflector, thus remarkably improving the efficiency of shape adjustment. Numerical example and physical experiment demonstrate the effectiveness of the proposed method. • A valuable research on flexible reflector antenna is studied considering wire mesh. • The sensitivity method greatly improves the efficiency of morphological analysis. • The shape adjustment process with real-time model updating is more instructive. [ABSTRACT FROM AUTHOR]

In this study, we develop flexible multibody dynamic-electromagnetic-structural vibration coupled analysis method to accurately predict motor vibration by considering the electromagnetic force characteristics, rotating characteristics of rotating motor motors, and their interactions at the no-load rated speed and operating speed range. The structural characteristics are accurately reflected by developing a three-dimensional (3D) finite element model considering the entire components of the motor. The reliability of the 3D finite element model of the motor is verified using the impact hammer test. In addition, to consider the rotational characteristics of the rotor structure, we develop a flexible multibody dynamics model that connects the flexible rotor and the bearing with revolute joint. The vibration of the motor at the no-load rated speed is analyzed using flexible multibody dynamics-electromagnetic-structural vibration coupled analysis. Comparing the vibration test results, it is confirmed that the flexible multibody dynamics-electromagnetic- structural vibration coupled analysis result predicts the actual motor vibration more accurately than the conventional finite element analysis-based electromagnetic-structural vibration coupled analysis result. By using flexible multibody dynamics-electromagnetic-structural vibration coupled analysis in the operating speed range, it is confirmed that not only electromagnetic force harmonics but also sideband harmonics caused by rotor eccentricity-induced large vibrations, and also confirmed that it accurately predicts the vibration characteristics of actual motors with rotating rotors. [ABSTRACT FROM AUTHOR]

Many flexible structures are characterized by a small number of compliant modes, i.e., large-deformation paths that can be traversed with little mechanical effort, whereas resistance to other deformations is much stiffer. Predicting the compliant modes for a given flexible structure, however, is challenging. While linear eigenmodes capture the small-deformation behavior, they quickly divert into states of unrealistically high energy for larger displacements. Moreover, they are inherently unable to predict nonlinear phenomena such as buckling, stiffening, multistability, and contact. To address this limitation, we propose Nonlinear Compliant Modes—a physically principled extension of linear eigenmodes for large-deformation analysis. Instead of constraining the entire structure to deform along a given eigenmode, our method only prescribes the projection of the system's state onto the linear mode while all other degrees of freedom follow through energy minimization. We evaluate the potential of our method on a diverse set of flexible structures, ranging from compliant mechanisms to topology-optimized joints and structured materials. As validated through experiments on physical prototypes, our method correctly predicts a broad range of nonlinear effects that linear eigenanalysis fails to capture. [ABSTRACT FROM AUTHOR]

To achieve real-time sensing and deformation reconstruction of flexible plate structure, a 3D reconstruction technique based on a quasi-distributed fiber grating sensor network and order-optimized modal superposition method is proposed. Graphic visualization is introduced to the field of deformation monitoring, then the displacement field reconstruction of the typical structure of spacecraft is realized. Firstly, a finite element model of the four-sided fixed-supported plate structure is constructed, and the conversion matrix of surface strain and displacement are obtained based on modal analysis, and then the modal parameters are optimized through static simulation experiments; Secondly, the influence of the number and position of sensors on the reconstruction accuracy is studied, then a high-density distributed fiber grating sensor network is attached to the surface of the plate to construct an experimental FBG model of the spacecraft; Finally, concentrated loads are applied to the structure at different positions, and structure's surface strain information is collected by FBG network, then the morphological reconstruction of the deformed structure is realized based on the improved model superposition method, which proves the feasibility of the algorithm. The results show that the reconstruction method's average absolute error is less than 0.13 mm, so this method can be used to displace field reconstruction problems of flexible structures. [ABSTRACT FROM AUTHOR]

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

Cellular structures have been widely studied and employed in engineering because of their excellent mechanical properties. To enrich the geometric diversity of cellular structures, we proposed two novel chiral cellular structures composed of half-periodic and full-periodic cosinoidal beams respectively in this paper. The in-plane elastic properties were studied by a combination of the energy method and the finite element analysis, and verified by the experimental test. The influences of geometric parameters on the elastic constants were analyzed. Then, the elastic properties of the two structures as well as the V-shaped chiral structure were compared. Finally, error analysis was carried out on the theoretical models. Results show that: (1) the two structures own considerably low equivalent elastic moduli and extremely high strain capabilities, and possess certain in-plane elastic coupling effects; (2) the elastic properties of the two structures are highly tunable with the variations of geometric parameters; (3) the elastic moduli of the two structures are lower than that of the V-shaped structure, and the structure with half-periodic beams exhibits the lowest in-plane stiffness and the highest strain capabilities; (4) the theoretical models without considering the internal axial force are convincible in predicting the elastic properties when the corresponding chord ratio is larger than 0.2. Generally, the proposed structures have great potential as flexible structures for morphing application. [ABSTRACT FROM AUTHOR]

The performance of a viscoelastic particulate composite (VEPC) in the passive control of parametric instability of layered beams is investigated. The effective properties of the VEPC layers in the layered beams are first estimated, and then the parametric instability of the layered beams is analyzed by deriving a finite element model. The results reveal significantly improved passive control of parametric instability of the layered beams when the monolithic viscoelastic damping layers are replaced by the present VEPC layers. Therefore, the present VEPC may be a potential damping material for improved passive control of parametric instability of flexible structures. [ABSTRACT FROM AUTHOR]

Soil is an anisotropic, heterogeneous, and inelastic complex material. It is difficult to represent the exact behavior of soil by numerical modelling in practice. Conventionally, soil is simplified to an idealized model where it is considered isotropic, homogeneous, and behaves elastically under loads. The idealization, in this case, is done using the proper elastic modulus, Poisson's ratio, and unit weight of soil depending upon the soil type. Although the exact soil behavior is simplified, using Finite Element Analysis (FEA) a more effective result can be obtained. A superstructure was modelled using ETABS using a fixed-base system and the base reaction forces were obtained. A mat and a soil element on which the mat was laid were modelled as a flexible-base system in Midas GTS NX. The base reactions obtained from ETABS were applied to the mat in the soil model to determine the settlements and, consequently, the spring stiffness. The superstructure was then modelled again, incorporating springs under the respective columns. Convergence in settlement, and base reactions were reached by iteration, and the final results from the flexible-base system were then compared with the fixed-base system. The center column settled the most, about 60 mm, and there was a decrease in settlement by 15% between the first model and the final iterated model. The base reaction for center columns decreased by 24% in the flexible base system compared to the fixed base system. However, an increase in base reaction was observed for both side and edge columns. There was an extremely erratic change in grade beams under a flexible base system, which shows that the superstructure elements are also affected by the change in the base system. It is recommended to use this approach, for the analysis of structures considering flexible base systems instead of fixed bases because it enhances the accuracy of analysis with feasible time consumption and less complex effort. [ABSTRACT FROM AUTHOR]

In order to suppress the vibration of a class of multi-coupling flexible beams, a three-coupling flexible beam experimental device is constructed. The vibration characteristics and active vibration control algorithms of three coupled flexible beams are studied. Due to the complex residual vibration of multi-coupled flexible beam structure, which shows the interaction between beams and close frequency characteristics, the dynamic model of coupled flexible beam structure is established by finite element method (FEM) and its theoretical modal analysis is carried out. Furthermore, the parameters of the experimental system are identified, and the close modal frequencies and damping ratios of the actual system are obtained. The characteristics of close modal vibration are verified. A reinforcement learning (RL) vibration controller based on proximal policy optimization (PPO) algorithm is designed. The algorithm mainly includes actor neural network and critic neural network, which are used to approximate the control strategy and evaluate state respectively. Based on theoretical modeling and experimental identification correction model, the agent learns offline, and then transfers the learned policy parameters to the experimental system for vibration control experiments. The experimental results demonstrate that the designed RL controller can effectively suppress the residual vibration of three coupled flexible beams. [ABSTRACT FROM AUTHOR]

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

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

The design requirements of a 2 m mirror assembly installed on a large space optical remote sensor are investigated in this study. The mirror body and rigid connectors are designed using topology and size optimization methods. The initial design scheme of flexible supports is then proposed through an in-depth exploration of fatigue failure mechanism caused by impacts of size parameters, thermal–mechanical vibration, and surface abrasion. The comprehensive analysis mode of the flexible support structure is established with the help of finite element and fatigue analysis software programs. The designed mirror surface error under composited force is 5.6 nm, first natural vibration mode is 119.16 Hz, and fatigue life synthesizing thermal–mechanical vibration is about 21,790,000 cycles, thereby meeting the design requirements. The first natural vibration mode, acceleration response, and stress responses of sine and random vibration are verified with experiments, and the findings are compared with the theoretical analysis results. The analysis mode can successfully and significantly improve the reliability of the mirror assembly and help optimize the design of flexible supports. [ABSTRACT FROM AUTHOR]

Dynamic force measurements are often corrupted by the structural dynamics of the surrounding support structure. Force reconstruction techniques aim to correct for these structural effects by using additional information such as a modal characterization of the structure, a finite element model of the assembly, or additional instrumentation. In practice, accurately measuring input forces to validate the techniques is often difficult or impossible. This work proposes a novel experiment that allows for measurement of the true input spatial force distribution acting on a structure for the purposes of experimentally validating force reconstruction techniques. In the proposed experiment, independently-controlled electromagnets are supported by force gages and used to excite a flexible structure. The reaction force from the electromagnet gives a measure of the applied forces over a given bandwidth, which can be used to validate force reconstruction techniques. This paper focuses on the design of such an experimental arrangement, and presents a numerical model which can also be used to validate force reconstruction techniques. Key components of this experiment are characterized to validate the measurements and methodology. The independently-controlled electromagnets can mimic different types of physical excitation forces, which allow for validation of various force reconstruction techniques aimed at niche applications. For example, the main application of the proposed experiment is to reconstruct unsteady fluid-borne forces generated on a flexible test structure. As such, a sample measurement mimicking forces generated by turbulent flow across a beam using electromagnets is provided. [ABSTRACT FROM AUTHOR]

In order to improve the seismic performance of lightweight flexible structures, a new type of air spring‐lead rubber bearing (AS-LRB) three-dimensional seismic isolation device with both horizontal and vertical seismic isolation was proposed. The construction of the AS-LRB was introduced, the horizontal and vertical mechanical properties of the AS-LRB were experimentally studied, the finite element (FE) model was developed based on the material properties of the AS-LRB, and the calculation method of the horizontal and vertical mechanical property parameters of the AS-LRB was proposed. The research results show that the air spring (AS) in the AS-LRB bears the vertical seismic isolation, and the lead rubber bearing (LRB) bears the horizontal seismic isolation. The energy dissipation capacity of horizontal seismic isolation is obvious, and its horizontal mechanical properties are significantly affected by the loading amplitude and vertical force. The load displacement behavior of vertical seismic isolation exhibits nonlinear characteristics, and its vertical mechanical properties are obviously affected by vertical force. In comparison with the test results, the FE model proposed can accurately simulate the AS-LRB, and the calculation method can accurately calculate the horizontal and vertical mechanical property parameters of the AS-LRB. • An air spring‑lead rubber bearing (AS-LRB) three-dimensional seismic isolation device was proposed. • The mechanical properties of the AS-LRB were studied, and the material properties of the AS capsule skin were tested. • The finite element model of the AS-LRB was developed based on the material properties of the AS capsule skin. • The calculation method of the horizontal and vertical mechanical property parameters of the AS-LRB was proposed. [ABSTRACT FROM AUTHOR]

As flexible structures, suspension bridges usually undergo significant deformation under live load when carrying rail traffic, jeopardizing the safety of passing trains. In engineering practice, suspension bridges with short extended spans have been applied to reduce the beam-end rotation angle under live load. However, the extended span layout is still determined empirically, and optimizing the span layout of such bridges to reduce maximum deformation under live load requires further investigation. This study proposes an analytical method for solving the maximum deformation responses of suspension bridges with extended spans under live load based on deflection theory and the extreme value analysis method. The proposed method can accurately solve the deformation responses of suspension bridges with extended spans caused by live load. It also allows one to analyze the most unfavorable live load distribution and the maximum deformation under live load, avoiding the redundant search process of the finite element method. Furthermore, the proposed method is applied to analyze the influence of the extended span layout on the maximum deformation responses under live load. The results show that adequately increasing the length of the first extended span and decreasing the length of the second extended span is beneficial to reduce the maximum beam-end rotation angle and the maximum curvature of the main beam. • The method can effectively solve the deformation responses in extended-spans suspension bridges under specific live load. • The method can determine the most unfavorable live load distribution and the maximum deformation responses under live load. • An in-depth analysis is conducted on how the extended span layout influences maximum deformation responses under live loads. • The method merges the deflection theory with extreme value analysis method, laying the groundwork for structural design. [ABSTRACT FROM AUTHOR]

[Display omitted] • MBD and FEA are combined to calculate the transient stress distribution. • CCA and ASO are combined to obtain the optimal shape. • Stress concentration is eliminated and the peak stress decrease by 34.35%. • The FCS with multi-layered flexible sheet is further analyzed. On-Load Tap-Changer (OLTC) is the only core equipment in the ultra-high voltage (UHV) converter transformer that moves frequently, and flexible connection structure (FCS) is the moveable actuating part of the vacuum interrupter drive mechanism of OLTC. Minimizing the transient stress during the movement of FCS is essential for prolonging its fatigue life, thus is pursued by optimizing the shape of the flexible sheet in this paper. Peak transient stress of FCS is defined as the optimization objective, and eight geometrical parameters controlling the shape of flexible sheet are defined as the optimization variables. A progressive three-stage shape optimization strategy is proposed by combing four techniques: Multi-body Dynamic (MBD), Finite Element Analysis (FEA), Correlation Coefficient Analysis (CCA) and Adaptive Single-objective Optimization (ASO). MBD analysis of the vacuum interrupter drive mechanism and FEA of the FCS are utilized for calculating the transient stress distribution. Spearman CCA is performed to quantitively determine the correlation and sensitivity between the optimization variables and the optimization objective. Shape optimization of FCS using ASO is carried out, and results show that the stress concentration is basically eliminated and the peak transient stress decrease by 34.35% after shape optimization. Further analysis of the FCS with multi-layered flexible sheet is conducted, again demonstrating the effectiveness of the shape optimization on minimizing transient stress. [ABSTRACT FROM AUTHOR]

• A composite structure that can regulate the in-plane Poisson's ratio is proposed. • The theoretical model of composite structure is established, whose prediction results agree with the numerical results. • A skin structure with an in-plane Poisson's ratio of approximately zero is optimized and fabricated. Regulating the inherent Poisson's ratio of soft elastic materials under large deformation is important for their application in emerging fields, such as morphing structures and stretchable electronics. In this study, we selected a composite in which an auxetic honeycomb was embedded in a soft material to regulate the in-plane Poisson's ratio. Based on a cantilever beam model, a theoretical model was established to guide the design optimization of composite structures. The macroscopic constitutive relation and in-plane Poisson's ratio of the composite structures with different configurations were predicted by the theoretical model, which were consistent with the finite element analysis results. In the 30% strain range, the slope of the Poisson's ratio–strain curve decreases with an increase in the length of the inclined bar, and the in-plane Poisson's ratio increases with an increase in the angle between the transverse bar and the inclined bar. In addition, we propose an optimization design method with the in-plane Poisson's ratio as the objective function and then optimize and fabricate a skin structure with an in-plane Poisson's ratio of approximately zero for the morphing wings. The achievements of this study provide theoretical guidance for regulating the in-plane Poisson's ratio of thin flexible layers. [ABSTRACT FROM AUTHOR]

From large scale structures such as bridges and cranes to small-scale structures such as lattices, mechanical structures today increasingly consist of "tuneable parts": parts with a simple geometry described by a small set of strongly varying parameters. For example, although a bridge is a macroscale structure with a complex geometry, it is made from simple beams, bolts and plates, all of which depend on spatially varying, geometrical parameters such as their length-to-width ratio. Accelerating this trend is the concurrent improvement of, on one hand, Additive Manufacturing techniques that allow for increasingly complex parts to be manufactured and, on the other, structural optimization techniques that exploit this expanded design space. However, this trend also poses a challenge to current simulation techniques, as for example the Finite Element Method requires large amounts of elements to represent such structures. We propose to exploit the large conformity between parts inside the mechanical structure through construction of semi-analytic "Parametrized Superelements", built by meshing with solid elements, reduction to a fixed interface and approximation of the reduced stiffness matrices. These new elements can be employed next to standard elements, enabling the simulation of more complex geometries. The technique we propose is applied to lattice structures and provides a flexible, differentiable, more accurate but still efficient way to simulate their elastic response. A net gain in total computation time occurs after simulating more than twenty lattices. As such, the proposed method enables large-scale parameter exploration and optimization of lattice structures for improved energy absorption, mass and/or stiffness. [ABSTRACT FROM AUTHOR]

Advanced nanomaterials and novel microstructures have been developed to achieve flexible piezoresistive pressure sensors with high sensitivity and wide linearity range. However, the theoretical relationships between the sensitivity and the structure of the flexible pressure sensor have rarely been established. Consequently, the sensitivities of the sensors cannot be controlled and tailored for practical application. In this work, a skin‐inspired flexible pressure sensor with gradient porous structure is proposed. Based on the stress distribution of finite element analysis (FEA), the quantitative descriptions between the sensitivity and sensor structure parameters are derived. Then, carbon black (CB)/polydimethylsiloxane (PDMS) composites are successfully fabricated with desired gradient porous structures by 3D printing technology. Encouragingly, the skin‐inspired gradient structure sensor shows good sensitivity (0.0048 kPa−1) over the ultrawide linear range of 0–500 kPa. Meanwhile, the sensor shows excellent stability and durability during over 500 compression cycles. Taking advantage of these excellent sensing properties, the skin‐inspired gradient porous sensor is demonstrated in the application of voice recognition, grasp sensing, and intermittent pneumatic compression (IPC) interface pressure monitoring. [ABSTRACT FROM AUTHOR]

Long-span suspension bridge is a flexible structure. When subjected to a horizontal transverse live load, its deck undergoes significant transverse bending deformation, jeopardizing traffic safety. This paper proposes an analytical calculation method for the static response of the entire suspension bridge with a horizontal transverse distributed live load applied to its deck. First, each component's geometric configuration and internal force for the suspension bridge subjected only to a dead load are obtained. Next, their values under the action of horizontal transverse live load are treated as basic unknown parameters. Then, governing equations are established based on geometric compatibility conditions, conservation of unstrained length, and force balance conditions. The unknown parameters are derived by nonlinear programming, estimating the entire suspension bridge's displacements and internal force response. The proposed analytical calculation method only considers the structural state of the suspension bridge before and after the action of the live load but not the intermediate process. Therefore, the complex problem of geometric nonlinearity involved in the stress calculation of the suspension bridge is precluded, and the calculation results are more accurate. Furthermore, the conventional treatment of all hangers as a continuous thin film is avoided. Instead, the effects of the following factors are analyzed: tower bending in the bridge-axis direction, tower torsion, hanger elongation, hanger inclination, and rigid body displacement of the deck in the bridge-axis direction. Finally, the feasibility and effectiveness of the method are verified by finite-element method (FEM) analysis of a suspension bridge with a main span of 548 m. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive approach for the linearized frequency-domain analysis of hydrodynamic loading and structural responses on a deformable body. The structural and hydrodynamic analyses are integrated by employing the mode superposition method. Commencing with an eigenvalue analysis on the structural model, the shapes of selected modes, mass, and structural stiffness matrices are extracted as input to the subsequent hydrodynamic analysis, where the global response is solved in the modal space. The resulting hydrodynamic and inertial loads are then transferred to the same finite element model for stress assessment. To exemplify the proposed methodology, a bottom-fixed flexible cylindrical monopile and a long box-shaped barge model are investigated. For the barge model, the sectional loads are obtained from the integral of stresses in the cuts along the structure model, which are found to be consistent with those from the hydrodynamic analysis, demonstrating the consistency of the entire workflow. In particular, this paper introduces a straightforward formulation for evaluating the generalized restoring matrices, eliminating the need for spatial derivatives of the mode shape function and thereby significantly reducing numerical uncertainties in using the flexible modes derived from finite element model for hydrodynamic analysis. • An integrated hydrodynamic-structural analysis workflow is proposed to account for the deformable motions of large volume floating structures. • Mode shapes FE model is taken as input to hydrodynamic analysis, with the resulting loads applied to the same model for stress evaluation. • Straightforward formulations proposed for restoring matrices, eliminating the need to operate with the spatial derivatives. • Mode superposition approach is validated against discrete module method to evaluate sectional loads and stresses for a flexible barge model. [ABSTRACT FROM AUTHOR]

• The enhanced segmented active constrained layer damping is proposed. • A new three-dimensional fan-section shell element is proposed. • The dependence on Euler's angular velocity of rotating hollow beam is found. • Neural network algorithm is used to optimize the structure. As an active and passive hybrid control technology, enhanced segmented active constrained layer damping (ESACLD) is an intelligent damping structure for suppressing adverse vibrations in flexible structures. In this study, the three-dimensional spatial dynamic model of a rotating hollow beam with improved ESACLD treatment is established based on the finite element method in a floating frame of reference. The damping effects of the ESACLD with both edge elements and incisions are considered in the dynamic model for the first time. Simulation results show the damping performance of the ESACLD is better than traditional active constrained layer damping with or without incisions (SACLD or ACLD). The Genetic Algorithm-Backpropagation (GA-BP) neural network is used to optimize the physical parameters of ESACLD, and the optimized model can effectively suppress the transverse and flapping bending vibration. It is also found that flapping and transverse bending vibrations exhibit differential dependence on nutation and precession angular velocities; higher nutation and lower precession velocities suppress flapping bending. The existing commercial finite element software has some problems, such as low efficiency and inaccuracy. The new finite element proposed in this paper uses a new form function to ensure accuracy in the simulation of rotation and vibration and has obvious advantages in dealing with rotational structures and complex boundary conditions. Research in this work can provide a design framework for vibration prediction and control of flexible beam-like structures. [ABSTRACT FROM AUTHOR]

The failure of harmonic gear drive is mainly caused by the fatigue fracture of flexible wheels and the fatigue damage of flexible bearings. In this paper, the stress sensitivity and fatigue life characteristics of flexible wheels with thin-walled vulnerable components are studied. Firstly, the structure of the flexible wheel of a B3-80 general harmonic gear reducer is designed, the finite element model of the flexible wheel is established by using ANSYS finite element software, and the finite element analysis results are compared with the theoretical calculations to verify the correctness of the model. Finally, by changing the cylinder length, smooth cylinder wall thickness and load, the maximum equivalent stress curves of the flexible gear ring, smooth cylinder and flexible wheel bottom are obtained, and the influence law of structural parameters on the stress characteristics of flexible wheel is obtained. At the same time, the influence laws of flexible wheel cylinder length and smooth cylinder wall thickness on the fatigue life of flexible wheel is studied, which provides a theoretical basis for the structural optimization design of the cup flexible wheel. [ABSTRACT FROM AUTHOR]

Thermally Induced Vibration (TIV) is a typical failure of flexible spacecraft appendages when they enter or leave the eclipse. However, it is very difficult to predict the on-orbit TIV by ground experiments mainly due to the gravity effect on these flexible structures. Using numerical predictions could be an alternative solution to this problem, if the numerical method can be verified by experimental results. For this purpose, ground TIV experiments for two slender cantilever tubes and the corresponding simulations by the Finite Element Method (FEM) are presented in this paper. This was the first time to use suspension strings to simulate the weightless on-orbit environment in TIV experiments. The nice consistence between the experimental and numerical results demonstrates that the Fourier FEM can successfully simulate the TIV responses. Thus, one can expect reliable numerical predictions of the on-orbit TIV based on the Fourier FEM model calibrated by the ground experiment. Besides, the classical Boley number defined for ideal step-wised heat flux is modified to an effective Boley number, which can evaluate the TIV intensity due to the ramped heat flux in practice. • TIV ground experiments were conducted by using the suspension strings to simulate the weightless on-orbit environment. • Fourier FEM results agree with the experimental results very well. • The effective Boley number is proposed to evaluate the intensity of TIV under practical thermal flux. [ABSTRACT FROM AUTHOR]

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

Background: A conventional three-dimensional digital image correlation (DIC) based on painted speckle patterns has been used widely as a non-contact measurement method to study modal analysis of various structures. Surface treatment using painted speckle patterns might change the structural properties of flexible and lightweight structures such as artificial wings of flapping micro air vehicles. Furthermore, if materials and structures are being serviced, it is essential that their surfaces not be contaminated. Objective: We propose a new DIC method that is capable of preventing effects of painted speckle patterns on thin flexible structures during vibration measurement. Methods: We project a virtual speckle pattern onto the surface of structures instead of using painted speckle patterns. For a benchmark test, we demonstrate the effectiveness of the proposed virtual speckle pattern DIC method for measuring the structural characteristics of a cantilever beam. We then apply the proposed DIC method to the vibration measurement of an artificial flapping wing. Finite element analysis (FEA) of the artificial wing is performed in ABAQUS™ to obtain natural frequencies and mode shapes. Results: The natural frequencies at the first three modes of the artificial wing obtained from the proposed method are higher than those obtained from the conventional 3D DIC because of the smaller weight of the unpainted wing. The results of the mass compensation, laser sensor, and finite element analysis prove the effectiveness of the proposed virtual speckle pattern DIC method. Conclusion: The proposed DIC method achieves high accuracy and prevents the effect of painted speckle patterns on the dynamic vibration measurement of a thin flexible structure such as an artificial flapping wing. [ABSTRACT FROM AUTHOR]

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

Highlights: Flexible films of kink porous carbon nanofibers are designed at the micro, meso and macro levels The fiber-film anodes with porous, kinked, and entangled network structures exhibit high rate and stability for potassium-ion storage With the emergence of wearable electronics, flexible energy storage materials have been extensively studied in recent years. However, most studies focus on improving the electrochemical properties, ignoring the flexible mechanism and structure design for flexible electrode materials with high rate capacities and long-time stability. In this study, porous, kinked, and entangled network structures are designed for highly flexible fiber films. Based on theoretical analysis and finite element simulation, the bending degree of the porous structure (30% porosity) increased by 192% at the micro-level. An appropriate increase in kinking degree at the meso-level and contact points in entanglement network at the macro-level are beneficial for the flexibility of fiber films. Therefore, a porous and entangled network of sulfur-/nitrogen-co-doped kinked carbon nanofibers (S/N-KCNFs) is synthesized. The nanofiber films synthesized from melamine as nitrogen sources and segmented vulcanization exhibited a porous, kinked, and entangled network structure, and the stretching degree increased several times. The flexible S/N-KCNFs anode delivered a higher rate performance of 270 mAh g−1 at a current density of 2000 mA g−1 and a higher capacity retention rate of 93.3% after 2000 cycles. Moreover, the foldable pouch cell assembled by potassium-ion hybrid supercapacitor operated safely at large-angle bending and showed long-time stability of 88% capacity retention after 4000 cycles. This study provides a new idea and strategy for the flexible structure design of high-performance potassium-ion storage materials. [ABSTRACT FROM AUTHOR]

In many practical engineering situations, a source of vibrations may excite a large and flexible structure such as a ship's deck, an aeroplane fuselage, a satellite antenna, a wall panel. To avoid transmission of the vibration and structure-borne sound, radial or polar periodicity may be used. In these cases, numerical approaches to study free and forced wave propagation close to the excitation source in polar coordinates are desirable. This is the paper's aim, where a numerical method based on Floquet-theory and the FE discretision of a finite slice of the radial periodic structure is presented and verified. Only a small slice of the structure is analysed, which is approximated using piecewise Cartesian segments. Wave characteristics in each segment are obtained by the theory of wave propagation in periodic Cartesian structures and Finite Element analysis, while wave amplitude change due to the changes in the geometry of the slice is accommodated in the model assuming that the energy flow through the segments is the same. Forced response of the structure is then evaluated in the wave domain. Results are verified for an infinite isotropic thin plate excited by a point harmonic force. A plate with a periodic radial change of thickness is then studied. Free waves propagation are shown, and the forced response in the nearfield is evaluated, showing the validity of the method and the computational advantage compared to FE harmonic analysis for infinite structures. [ABSTRACT FROM AUTHOR]

Specific satellites with ultralong wings play a crucial role in many fields. However, external disturbance and self-rotation could result in undesired vibrations of the flexible wings, which affect the normal operation of the satellites. In severe cases, the satellites would be damaged. Therefore, it is imperative to conduct vibration suppression for these flexible structures. Utilizing fuzzy-proportional integral derivative control and deep reinforcement learning (DRL), two active control methods are proposed in this article to rapidly suppress the vibration of flexible structures with quite small controllable force based on a cable-driven parallel robot. Inspired by the output law of DRL, a new control method named Tang and Sun control is innovatively presented based on the Lyapunov theory. To verify the effectiveness of these three control methods, three groups of simulations with different initial disturbances are implemented for each method. Besides, to enhance the contrast, a passive pretightening scheme is also tested. First, the dynamic model of the cable-driven parallel robot which comprises four cables and a flexible structure is established using the finite element method. Then, the dynamic behavior of the model under the controllable cable force is analyzed by the Newmark-ß method. Finally, these control methods are implemented by numerical simulations to evaluate their performance, and the results are satisfactory, which validates the controllers' ability to suppress vibrations. [ABSTRACT FROM AUTHOR]

Optoelectronic packaging is an important component of optical communication systems. However, it is a challenge for the packaging equipment to simultaneously have multiple degrees of freedom (DOF), wide range, and high precision. In this article, a six-degree-of-freedom (6-DOF) compliant parallel platform with all these features is presented. This platform has a parallel basic structure with large-stroke flexible joints. Based on elastokinematic analysis, the inverse kinematics solution of the platform is derived, and the effectiveness of the platform is proved by analyzing the 6-DOF motion via finite element analysis. The reachable workspace of the platform is analyzed, and its solution process is simplified using the inverse distance weighted method. Furthermore, a prototype of the proposed platform is presented and its accuracy is evaluated through experiments. Error compensation is used to significantly improve the motion accuracy of the platform. A closed-loop control that uses optical power meters instead of a multi-DOF detection device is proposed for optoelectronic packaging. The performance of the prototype applied to the packaging of coaxial optoelectronic devices is also demonstrated by experiments. The results demonstrate that the 6-DOF compliant parallel platform can successfully carry out the optical alignment of optoelectronic devices. [ABSTRACT FROM AUTHOR]

In this paper, the authors introduce a model of a strain-based geometrically nonlinear piezoelectric beam for modeling energy harvesters. A nonlinear shear-underfomable 3-D Rayleigh's beam theory is used to model the displacement fields and can be considered as an interesting alternative to linear and highly nonlinear models commonly presented in the literature. The nonlinearities are introduced to reproduce the behavior of the flexible structure, since moderate to large displacements can occur in response of external loading conditions. The finite element method is used to model the piezolaminated bimorph configuration. Each finite element consists of two piezoelectric energy harvesters embedded or perfectly bonded to an elastic substrate. The electromechanical coupling includes axial and flexural effects as well as additional term that comes from the nonlinearity incorporated into the strain tensor. Additionally, the authors explore briefly two topics for linear harvesters: the influence of the electric domain on the structural properties and, the performance of the harvester near resonance in term of electric power output of a purely resistive network. As a validation case, a cantilevered piezoelectric energy harvester under base excitation is modeled. Alongside, the response to gust of a harvester embedded in a wing structure is analyzed. [ABSTRACT FROM AUTHOR]

In this study, considering the non-uniform action of actual wheel loads, the influence of bonding conditions at the surface layer/base and base/subbase interfaces on the structure of flexible base asphalt pavement was investigated. The mechanical response under two extreme bonding conditions – one with full slip and the other with complete continuity – was calculated by using the three-dimensional finite element software EverStressFE. Moreover, the dynamic evolution of the life of the pavement structure under different bonding conditions was comprehensively explored. The results show that the bonding conditions had different effects on pavement surface deflection, shear strain, flexural-tensile strain, and maximum vertical compressive strain at the top of the subgrade. The life of the pavement structure controlled by fatigue cracking and permanent deformation decreased non-linearly with the gradual deterioration of bonding conditions. The main mode of damages to the pavement structure alternated between permanent deformation and fatigue cracking, thereby increasing the difficulty of design, construction, and maintenance. Compared with the non-uniform action of wheel loads, the bonding conditions had a larger and independent impact on the structure of flexible base asphalt pavements. [ABSTRACT FROM AUTHOR]

In this paper, the dynamics of the flexible riser are investigated based on the absolute nodal coordinate formulation (ANCF). The stiffness, generalized elastic force, external load, and mass matrixes of the element are deduced based on the principle of energy conversion and assembled with the finite element method. The motion equation of the flexible riser is established. The influence of the environmental load conditions on the flexible riser model is studied in the MATLAB environment. Moreover, the accuracy and reliability of the programs are verified for a beam model with theoretical solutions. Finally, the static and dynamic characteristics of the flexible riser are analyzed, systematically adopting the ANCF method, which in turn proves the effectiveness and feasibility of the ANCF. Therefore, the proposed method is a powerful scheme for investigating the dynamics of flexible structures with large deformation in ocean engineering. [ABSTRACT FROM AUTHOR]

Featured Application: Flexible support is often used in high-speed flexible rotor systems, such as the textile winding rotor, to make the rotor pass smoothly through the critical speed points. The structural coupling, as well as time-varying and frequency-dependent parameters increase the complexity of the winding rotor dynamic behaviors and the difficulty of vibration control. This paper presents a method to reveal the dynamic behavior of the winding rotor through simulation analysis and non-contact test measurement, which have important potential applications in the design of flexible rotor structural parameters and process parameters. To satisfy the requirements of high speed, large capacity and constant winding, a textile winding rotor needs to work in a wide rotation speed range and frequently pass through critical speed points. Thus, the winding rotor adopts the flexible long shaft coupling structure and flexible support with rubber O-rings. This kind of rotor has a multi-coupling structure and frequency-dependent parameters characteristics, especially representative and universal in the dynamic analysis method of the high-speed rotor. In this paper, an approach was proposed to investigate the dynamic behavior of the winding rotor considering the flexible coupling and frequency-dependent supporting parameters. Firstly, a dynamic model of the winding rotor was established by using a Timoshenko beam element. Its dynamic behaviors were simulated by considering the time-varying rotation speed and the frequency-dependent parameters of flexible support. Secondly, a non-contact measuring device was developed for measuring the vibration displacement of the winding rotor in three different speed-up times. Finally, based on simulation and measurement data, how flexible support parameters and the speed-up time affect the winding rotor passing through the critical speed point of the rotor smoothly is revealed. The methods and findings reported here can be used for theoretical and experimental vibration analysis of other types of high-speed flexible rotors. [ABSTRACT FROM AUTHOR]

In order to overcome the apparent characteristics as a flexible structure of a long-span single-tower cable-stayed bridge and the excessive axial force of the main girder, and to exert the advantages of cable-stayed arch cooperative system bridges, this paper proposes a new type of single-tower cable-stayed arch cooperative system bridge. On the premise of the same amount of steel, the new cooperative system bridge can have a greater stiffness than the existing cable-stayed arch cooperative system bridge with the same span. The new system bridge uses the main girder as the rigid tie bar to balance the arches' thrusts, which enables the main girder to have a smaller axial force and makes the cable-stayed arch cooperative system bridge a thrustless structure. The proposed bridge is assembled by the following method: (a) constructing a cable-stayed bridge with a steel box girder to bear part of the dead load and to act as a construction platform firstly; (b) then installing arch structures and fixing they with the girder to bear the remaining dead load; and, (c) adding web members between the arch ribs and the girder to form a variable-height truss structure with the arch ribs as the upper chords and the girder as a lower chord to bear most of the live load at last. The underlying mechanical principles were explained, and the mechanical properties of the cooperative system bridges were calculated with the finite element method in this paper. The stiffness and axial forces in the girders are analyzed by the finite element method and compared with those of the conventional bridges. The FEA results show that the new cooperative system bridge has the truss structure's characteristics, which shows apparent advantages of stiffness and much smaller axial force in the main girder. [ABSTRACT FROM AUTHOR]

As the innermost structure of the flexible pipe, the carcass layer plays the role of bearing the external hydrostatic pressure. How to improve the crushing resistance of the carcass layer is the focus of the research on the flexible pipe structure. In order to study the influence of the cross-sectional parameters of the carcass layer on the crushing resistance of the flexible pipe, a three-dimensional finite element model of the carcass layer was established, and the results of finite element numerical analysis were verified through theoretical calculations. On this basis, the orthogonal experimental method was carried out to study the influence of the cross-sectional parameters on the crushing resistance. Finally, through the response surface method combined, the optimized cross-sectional parameters of the carcass layer were obtained. The results show that the mass of the optimized carcass layer decreases by 5% and the crushing resistance increases by 11%, which provides a reference for improving the crushing resistance of the flexible pipe. [ABSTRACT FROM AUTHOR]