Analysis Of Mechanical Structures Research Articles

Structural Design and Mechanical Analysis of HTS CICC Made From Twisted Stack Slotted-Core Cable

Structural Design and Mechanical Analysis of HTS CICC Made From Twisted Stack Slotted-Core Cable

Simulation and Structural Analysis of a Flexible Coupling Bionic Desorption Mechanism Based on the Engineering Discrete Element Method.

Soil adhesion is one of the important factors affecting the working stability and quality of agricultural machinery. The application of bionic non-smooth surfaces provides a novel idea for soil anti-adhesion. The parameters of sandy loam with 21% moisture content were calibrated by the Engineering Discrete Element Method (EDEM). The final simulated soil repose angle was highly consistent with the measured soil repose angle, and the obtained regression equation of the soil repose angle provides a numerical reference for the parameter calibration of different soils. By simulating the sinusoidal swing of a sandfish, it was found that the contact interface shows the phenomenon of stress concentration and periodic change, which reflects the effectiveness of flexible desorption and soil anti-adhesion. The moving resistance of the wedge with different wedge angles and different serrated structures was simulated. Finally, it was found that a 40° wedge with a high-tail sparse staggered serrated structure on the surface has the best drag reduction effect, and the drag reduction is about 10.73%.

Structural design and mechanical analysis of small-caliber bilayer vascular prostheses

This research comprehensively addresses the influence of structural properties and polymer type on the mechanical performance of bilayer vascular grafts. The grafts consist of inner layers with randomly distributed polycaprolactone(PCL)/polylactic acid(PLA) or poly(l-lactide-co-caprolactone)(PLCL) fibers and an outer layer with radially oriented PLCL fibers, manufactured through a sequential electrospinning process. Highlighted results indicate that tubular scaffolds possess an inner layer ranging in thickness from 62 to 94 µm, while their outer layers vary in thickness from 180 to 296 µm. In addition, radially oriented fibers enhance tensile strength in radial direction (9–11 MPa), while depending on polymer composition and wall thickness proportions of individual layers, tensile strength values change between 2.7 and 7.7 MPa in longitudinal direction. Scaffolds with elastic PCL or PLCL inner layers display higher compliance values (above 1%/mmHg × 10−2).

Simulation for Endovascular Treatment

With the advent of high-resolution imaging and advancements in computational fluid dynamics(CFD)and computational structural mechanics(CSM)analyses, clinical simulation of endovascular intervention has gradually become feasible. Virtual stents have become indispensable for coil embolization. For braided stents, such as those with low-profile visualized intraluminal support and flow diverters, predicting postplacement elongation and contraction is challenging; however, software development has enabled more precise treatment planning. Additionally, simulations utilizing three-dimensional(3D)printer models can enable realistic simulations of procedures such as intracranial stents and Woven EndoBridge placement. This approach is beneficial for shunt disorders such as arteriovenous malformations and dural arteriovenous fistulas, offering 3D visualization of shunt access routes and intuitive treatment strategy planning, even for beginners. Furthermore, it can be applied to procedures such as open surgical clipping and nidus resection, aiding in the selection of suitable clips and considerations for ideal resection based on nidus curvature. Simulations using CFD, CSM, and 3D printers are crucial for training surgeons and handling new devices. Harnessing medicine-engineering synergy is essential, and regulatory approval(insurance coverage)and appropriate commercialization of simulations are paramount for the future.

Coupled AC2-CFD simulations for a high-pressure core melt accident scenario

Abstract Even though very unlikely to occur, severe accident scenarios in nuclear power plants have to be analyzed. During high-pressure core meltdown scenarios in a pressurized water reactor the primary circuit should fail first. Previous analyses found that a free convection flow within the vertical steam generator (SG) tubes with a simultaneous stratified gas counterflow in the hot legs could arise. This phenomenon leads to higher thermal loads on individual SG tubes which might then fail leading to a containment bypass and the release of radioactive material into the environment. Lumped parameter system codes used for safety analyses do not provide the models necessary to simulate phenomena like mixing in three-dimensional flows and could not consider local turbulence effects. Computational fluid dynamic (CFD) codes provide such capabilities but are much more computationally expensive. Coupling of a system code with a CFD code can therefore be used to simulate such phenomena. The advantages of both approaches can be maximized by splitting up the simulation domain between the codes, depending on the expected flow conditions. The system code AC2 coupled with the CFD code OpenFOAM was used to simulate part of the severe accident transient. Free convection in the hot leg and the U-tubes of the vertical SG was observed in case of high-pressure severe accident sequences. The thermal load of individual SG tubes has been estimated from the results. These loads can be used as inputs for structural-mechanical analyses to estimate which part of the primary circuit would fail first.

Synthesis of diamondoids through hydrogenation of adamantane-annulated arenes

Abstract Diamondoids are cage-shaped saturated hydrocarbons whose carbon scaffolds are substructures of diamond. Despite their potential application, the availability of diamondoids has been significantly limited due mainly to the difficulty in synthesis. Herein, we report a new synthetic methodology for diamondoids. It was found that adamantane-annulated arenes, which can be synthesized by our recently developed method, can be transformed to saturated hydrocarbons by catalytic hydrogenation of arene moieties. The thus-obtained hydrocarbons are unnatural diamondoids, which are otherwise difficult toobtaine. The structural analysis and DFT calculation of the reaction mechanism were also performed to initiate exploration of the untapped synthetic chemistry of diamondoids.

A dual-mode stick-slip piezoelectric actuator imitating mantis forefoot

Most existing stick-slip piezoelectric actuators fail to achieve smooth motion and linear speed, and the backward motion cannot be actively inhibited during motion. This paper develops a novel piezoelectric actuator with stiffness-variable flexible mechanism imitating mantis forefoot, which utilizes the elastic potential energy to suppress backward motion. Furthermore, the contact condition between the driving foot and the rotor can be adjusted through a joint-like flexible structure. On this basis, contact precisely adjusted driving (CPAD) mode and triangular wave cooperative driving (TWCD) mode are proposed to achieve complete suppression of backward motion, as well as high-speed and high-resolution output. The transfer matrix method (TMM) in the cross-section of multiple state nodes has been improved and applied to accurately establish the theoretical model for the complex flexible hinge structure, with the combination of FEM for structural optimization design and mechanical properties analysis. The error between the calculated results and the experimental results is within 4%. Finally, a prototype with dimensions of Ø36 × 10 mm is manufactured and tested. The results show that both driving modes are able to achieve smooth motion output by actively suppressing backward motion, and a linear speed curve can be achieved under 800 Hz. The prototype achieves a maximum speed of 4491.38 mrad/s and a rotational resolution of 0.332 μrad, which is significantly better than existing actuators with similar size. This study shows great value for applications in the field of fast and precise positioning with size constraints.

Research and Analysis of Coulomb Friction in Landing Gear Shimmy

Aircraft are subject to small disturbances during taxiing, many of which are accidental and difficult to explain. Although nonlinear factors are considered in traditional analysis, Coulomb friction is generally ignored, and the interaction and common effects of nonlinear factors are mostly not discussed. In this paper, the dynamic model of shimmy is established, and the influence of Coulomb friction on shimmy is studied by using bifurcation theory and the structural mechanics analysis method. The results show that the system with Coulomb friction has subcritical Hopf bifurcation and that the system with square damping has supercritical Hopf bifurcation. Although the two do not change the stability of the system, their cooperation can improve the stability of the system. The Coulomb friction torque of the system has a complex piecewise functional relationship with the stability distance, rake angle, and acceleration. Some combinations will lead to very low Coulomb friction and deteriorate the anti-interference ability of the landing gear. This paper provides theoretical basis and support for the rational design of structural parameter collocation, enhancing the antidisturbance ability of the system during constant-speed or variable-speed taxis and explaining the shimmy phenomenon in the process of variable-speed taxis of some aircraft.

Hiding behind the platform: the myth of flexibility for gig workers in Indonesia

ABSTRACT Mainstream arguments hold that the digital gig economy has been a boon for countries with high levels of unemployment, and some have even deemed it the future of work. Online platform companies handling transportation, courier and food delivery services – such as Gojek, Grab and Maxim – have similarly built narratives that the drivers who become their partners will enjoy flexible working conditions. Using a structural analysis of flexible work mechanisms in the digital gig economy, this article explores the asymmetrical power of gig workers and online platform companies. Taking a post-positivist approach, the data in this research were collected through interviews with 290 platform drivers. The results show that the structural situation, wherein extensive reserves of labour exist and workers’ power is weak, has created a significant power asymmetry between gig workers and platform companies. The impact of this asymmetry of power makes the flexibility promised to gig workers a myth and actually increases precarity for workers.

The Impact of Thermal Load and Turbulent Flow on Minimum Film Thickness of a Large Tilting-Pad Journal Bearing

Abstract Thermal loads induced by internal fluid friction significantly influence the operating behavior of high-speed journal bearings. These loads increase on average if critical Reynolds numbers are exceeded. This paper presents a detailed thermo-elasto-hydrodynamic (TEHD) analysis of a large five-pad tilting-pad journal bearing operating up to surface speeds of 94 m/s. The structure mechanical analysis is conducted by a FE-Code that is implemented as a submodule of the bearing code to improve computational efficiency. The nonlinear structure model includes the pads, their aligning ring, and the housing while the journal's thermal expansion is approximated analytically. The contact of pads and ring is modeled with a contact algorithm. Validation with test data from literature indicates the relevance of structure model's complexity. Besides the pad deflection, in particular, the consideration of the ring and housing thermal expansion is decisive in predicting the effective clearance properly. Furthermore, comparisons between measurement and simulation show that the experimentally identified nonlinear speed-dependent characteristic of minimum film thickness that features an increase due to turbulent flow is well predicted by the theoretical model. Generally, results provide an insight on the impact of the different effects dominating the behavior of the bearing in the respective speed ranges, and therefore, improve the understanding of complex bearing systems. Finally, the quality of results of approximation formulas that are easier to implement and more time efficient than the complex FE-code is investigated.

Sub-channel analysis for LBE cooled fuel assembly with grid type spacers of China initiative accelerator driven system

The present study focuses on the thermal hydraulic characteristics of fuel assemblies in the China Initiative Accelerator Driven subcritical System (CiADS), which utilizes grid-type spacers to support lead bismuth eutectic (LBE) cooled fast reactors. While the structural design and mechanical analysis of CiADS triangular fuel assemblies with grid-type spacers have been preliminarily investigated, there is a pressing need to study the thermal hydraulic behavior of liquid LBE within these fuel assemblies. This analysis is crucial for assessing the safety and economy of the CiADS subcritical reactor. The sub-channel analysis code, based on the lumped parameter method, plays a vital role in rapidly evaluating the safety features of LBE-cooled fast reactor fuel assemblies. To comprehensively evaluate the thermal hydraulic performance of fuel assemblies with grid-type spacers in the CiADS LBE cooling system, the flow pressure drop model, turbulent mixing model, and convective heat transfer model for the fuel assembly structure with grid-type spacers were incorporated into the existing CiADS sub-channel analysis code. This enhanced code has been successfully employed in the thermal hydraulic analysis of fuel assemblies utilizing wire-type spacers in the CiADS system. To verify the validity and accuracy of the modified CiADS sub-channel analysis code in calculating triangular fuel assemblies with grid-type spacers, the code was first utilized to replicate a 19-rods flow heat transfer experiment with grid-type spacers cooling liquid LBE. A comparison between the simulation and experimental results confirms that the CiADS sub-channel analysis code can predict the coolant temperature and fuel rod surface temperature in fuel assemblies with grid-type spacers. Subsequently, the structure and thermal hydraulic design of the latest CiADS fuel assembly with grid-type spacers were reviewed. Finally, taking into account the aforementioned enhancements to the CiADS sub-channel analysis code, a comprehensive thermo-hydraulic calculation of the CiADS fuel assembly with grid-type spacers was conducted. The results demonstrate that the coolant outlet temperature, maximum cladding temperature, and maximum fuel pellet temperature all fall within the design parameters of CiADS. Furthermore, the impact of the number of rods in different rod bundles (91, 61, 37, and 7 rods) on thermal hydraulic performance was analyzed. The findings indicate that, while ensuring calculation accuracy and efficiency, the results obtained from the 37-rod bundle can effectively reflect the thermal hydraulic behavior of the reactor core.

Structural Analysis of the Evolution Mechanism of Online Public Opinion and its Development Stages Based on Machine Learning and Social Network Analysis

Internet public opinion is a complex and changeable system, and its trend development is characterized by explosive, evolutionary uncertainty, concealment and interactivity due to the participation of the vast number of Internet users. Today, with the rapid development of network information technology, public opinion has an increasing influence on the stable development of society. Computational intelligence is the frontier field of artificial intelligence development, and computational intelligence is used to mine and analyze public opinion text information and study the evolution of online public opinion. This paper uses the Changchun Changsheng Vaccine Incident as an example, and the netizens’ degree of attention to emergency-related keyword searches in the Baidu Index as a descriptive variable for the development of network public opinion. After applying the optimal segmentation algorithm, the development of public opinion is divided into phases. On this basis, a social network analysis is adopted to analyze the spatial and topological structure of each phase of network public opinion, using data from the Sina Weibo platform. Based on optimal segmentation, the development of network public opinion of the Changchun Changsheng Vaccine Incident can be divided into four phases, namely latent, spreading, control, and stable; each phase has different spatial and topological characteristics. Corresponding policy suggestions on network public opinion governance are put forward for each phase.

Design, properties, and applications of non-pneumatic tires: A review

The interest in airless or non-pneumatic tire (NPT) structures emerges due to potential performance and environmental advantages, such as reduced rolling resistance and improved recyclability, when compared with traditional rubber-based pneumatic tires. NPTs can already be found in commercial applications such as forklifts, electric scooters, and wheelchairs. Even so, up to the knowledge of authors, there is no known established large-scale production of NPTs for most applications. This work presents a systematic literature review regarding the mechanical design and development of NPTs. A summary of structural characteristics and mechanical behaviour analysis is provided. Relevant standards, analysis strategies, materials, production techniques, and the end-of-life of tires are addressed. In the end, the authors debate the current challenges and prospects of these emergent products. Furthermore, this research aims at being used as a tool, potentiating the development of innovative and efficient, airless tire solutions. The review presented clarifies that many academic efforts are focused on finding optimal functional designs, which are frequently complex and physically demanding. These geometrically complex design proposals are, in most cases, composed of intricate cellular structures and spokes arrangements. Based on the current lack of knowledge, authors identify key research areas to be further developed such as the production, performance, and reliability of NPTs. It is debatable whether there will ever be a shortcoming of the rubber tire, or a time when fully recyclable tires are a societal obligation. Nevertheless, the number of reasons to promote the development of a reliable replacement to the traditional tire is far from scarce.

Structure and mechanical properties of ladybird elytra as biological sandwich panels

The armour of the ladybird, elytra, protect the body from injury and are well-adapted to flight. However, experimental methods to decipher their mechanical performances had been challenging due to the small size, making it unclear how the elytra balance mass and strength. Here, we provide insights to the relationship between the microstructure and multifunctional properties of the elytra by means of structural characterization, mechanical analysis and finite element simulations. Micromorphology analysis on the elytron revealed the thickness ratio of the upper lamination, middle layer and lower lamination is approximately 51:139:7. The upper lamination had multiple cross fibre layers and the thickness of each fibre layer is not the same. In addition, the tensile strength, elastic modulus, fracture strain, bending stiffness and hardness of elytra were obtained through in-situ tensile and nanoindentation-bending under the influence of multiple loading conditions, which also serve as references for finite element models. The finite element model revealed that structural factors such as thickness of each layer, angle of fibre layer and trabeculae are key to affecting the mechanical properties, but the effect is different. When the thickness of upper, middle and lower layers is the same, the tensile strength provided by unit mass of the model is 52.78% lower than that provided by elytra. These findings broaden the relationship between the structural and mechanical properties of the ladybird elytra, and are expected to inspire the development of sandwich structures in biomedical engineering.

Structural Stiffness and Mechanical Analysis of Fiber Wound Composite Sports Equipment Reinforced with Carbon Fiber Materials

Continuous improvements in sports equipment are crucial for enhancing performance and ensuring safety. Carbon fiber composites, comprising carbon fibers and a matrix such as resin, metal, or ceramics, have exceptional strength and stiffness properties. This study focused on the application of carbon fiber reinforced composites in sports equipment, with an emphasis on optimizing the stiffness of lightweight equipment. The research revealed that fiber-wound composites exhibit nonlinear behavior, and the overlapping fiber structure can impede damage propagation, leading to greater in-plane shear failure strain compared to composite laminates. The study aimed to predict the mechanical behavior and structural stiffness of fiber-wound composite sports equipment reinforced with carbon fibers. The findings can be used to improve the design and manufacturing process of sports equipment, leading to better performance and durability. The utilization of these materials in sports equipment may also contribute to reducing the weight of the equipment, thereby enhancing athlete’s performance and reducing the risk of injury.

Structural design and mechanical analysis for space-borne electronic equipment

With the development of a new generation of radar performance requirements, the chip integration and module assembly density of onboard electronic equipment have been greatly improved. The integration of the system is becoming more complex. This paper designs a kind of electronic equipment with a superposition structure. Separate functional modules are strung together by a screw. Each module unit has the same sectional size. The conventional cabinet form structure is abandoned. The main contradiction of volume, weight, and reliability is solved well. The mechanical properties of electronic equipment are analyzed by the finite element method, and the structure of the fixed lug is optimized. The result shows that the electronic equipment meets the requirements of structural safety margin. The structural design is safe and reliable.

IsoGeometric Analysis with non-conforming multi-patches for the hull structural mechanical analysis

IsoGeometric Analysis (IGA) has been applied in hull structural analysis and proved to be efficient and accurate. Nevertheless, the advantages of IGA have not been fully utilized. In this paper, IGA technics for hull structural analysis are further developed. A 3 Degrees-Of-Freedoms C1-continuous Kirchhoff–Love shell element is used to analyze hull structures, and the weighted non-symmetric Nitsche’s method is used to couple connected patches. With the proposed shell elements and coupling method, the modeling of hull structures for IGA is greatly simplified. A typical hull block structure with complex interfaces is used to verify the correctness and accuracy of non-conforming multi-patch IGA. The commercial software ANSYS 17.0 is used to obtain reliable reference solutions. An extreme non-conforming IGA model with 231 non-conforming interfaces is adopted to test the robustness of IGA. When using the weighted non-symmetric Nitsche’s method, the maximum relative error of displacements is 1.7%, and the maximum relative error of von Mises stresses is 1.0%, which is acceptable in engineering. The correctness and robustness of non-conforming multi-patch IGA for the hull structural analysis are verified. The engineering practicability of IGA is proved.

Fluid-structure interaction analysis of airflow, structural mechanics and aerosol dynamics in a four-generation acinar model

Elucidating the aerosol dynamics in the pulmonary acinar region is imperative for both health risk assessment and inhalation therapy, especially nowadays with the occurrence of the global COVID-19 pandemic. During respiration, the chest's outward elastic recoil and the lungs' inward elastic recoil lead to a change of transmural pressure, which drives the lungs to expand and contract to inhale and expel airflow and aerosol. In contrast to research using predefined wall motion, we developed a four-generation acinar model and applied an oscillatory pressure on the model outface to generate structure deformation and airflow. With such tools at hand, we performed a computational simulation that addressed both the airflow characteristic, structural mechanics, and aerosol dynamics in the human pulmonary acinar region. Our results showed that there is no recirculating flow in the sac. The structural displacement and stress were found to be positively related to the change of model volume and peaked at the end of inspiration. It was noteworthy that the stress distribution on the acinar wall was significantly heterogeneous, and obvious concentrations of stress were found at the junction of the alveoli and the ducts or the junction of the alveoli and alveoli in the sac. Our result demonstrated the effect of breathing cycles and aerosol diameter on deposition fraction and location of aerosols in the size range of 0.1–5 μm. Multiple respiratory cycles were found necessary for adequate deposition or escape of submicron particles while having a negligible influence on the transport of large particles, which were dominated by gravity. Our study can provide new insights into the further investigation of airflow, structural mechanics, and aerosol dynamics in the acinar depth.

Mechanical response of interlayer structural shear performance of asphalt pavement with functional layer considering interlayer contact state

To explore the mechanical response of asphalt pavement structure with functional layer, and make asphalt pavement have better service performance, a structural combination form of asphalt pavement with functional layers is proposed in this study, and the interlayer structural mechanical response analysis is carried out based on the theory of a multi-layer flexible layered system. The study first suggests a combined method of stress-strain and displacement at each point of the three-dimensional asphalt pavement structure under the combined compressive-shear load. Secondly, the shear strength of asphalt pavement structure with functional layer under the influence of compressive-shear combined loads, different longitudinal slopes, overload loads, and temperature-elastic modulus under different interlayer contact states are analyzed. Finally, the distribution of structural shear strain of asphalt pavement with a functional layer under different conditions is investigated. The results show that in the asphalt pavement structure with a functional layer, the functional layer is the weak layer of the base-surface layer, and the interlayer shear stress will change abruptly under the combined compression-shear load. The maximum shear stress and extreme strain values are mainly concentrated in the upper and middle surface layers, and they show a consistent trend of first increasing and then decreasing with the increase of the pavement depth. The functional layer can be used as a temperature buffer zone so that the asphalt pavement has good contact performance between the surface and base at 76 ℃ and good shear strength. The results of this study provide a theoretical foundation for studying the interlaminar shear resistance of asphalt pavement with functional layers.

Effect of offset between beam outside and neutral surfaces on dynamic soil-structure interactions

In finite element analyses of the dynamic soil-structure interaction (SSI), structures are often modelled as beam or shell elements in structural mechanics, while the soil requires discretization using solid elements in solid mechanics. The beam and shell elements are coupled with the solid elements on their outer surfaces, while the mechanical behaviour of the beam and shell elements are usually represented by variables defined at their neutral surfaces. The offset between the beam outer surface and the neutral surface in several dynamic SSI analyses is often ignored, which can cause large errors in the coupling analysis of solid and structural mechanics. This paper investigates the effect of the offset between the beam outer surface and neutral surface on the dynamic SSIs. First, the coupling conditions between the beam and the solid considering the offset between the beam outer surface and the neutral surface are deduced. In this process, the tangential interaction stress on the beam outer surface is transformed into an axial force and a moment acting on the beam neutral surface, and the tangential displacement on the beam outer surface is related to the axial displacement at the beam neutral surface as well as the cross-section rotation angle. Then, the coupling condition is implemented in the finite element analysis by modifying the mass and stiffness matrices of the beam element. The offset effects between beam outer surfaces and neutral surfaces on dynamic SSIs are finally discussed in detail through the seismic responses of a retaining wall, subway station and tunnel.