Analysis Of Mechanical Structures Research Articles

Structural Synthesis and Analysis of Spatial Mechanisms Designed from Planar- and Screw-Type Kinematic Chains

Structural Synthesis and Analysis of Spatial Mechanisms Designed from Planar- and Screw-Type Kinematic Chains

Development of a thermoplastic constitutive model for steel based on the generalized Mises yield criterion

Steel is widely used in building structures, and the constitutive model that describes the steel's response to load is an essential component of structural mechanics analysis. This paper aims to investigate the thermoplastic behavior of steel at elevated temperatures. Based on the classical elastoplastic mechanics framework, this study introduces a generalized Mises yield criterion derived from energy theory, which takes into account the temperature effect. In conjunction with relevant assumptions, hardening condition, flow rule, the generalized Hooke's law, and consistency condition, we derive a novel incremental thermoplastic constitutive model for steel. And the new thermoplastic constitutive model's rationality is further verified by utilizing high-temperature steady-state tensile test data. It is encouraging that this new model can accurately describe the mechanical behavior of steel in high-temperature environment such as fire, which is of significant importance for fire safety design of building structures.

Numerical study on structural design and mechanical analysis of anti-migration tracheal stent with non-uniform Poisson's ratio

Stent migration is one of the common complications after tracheal stent implantation. The causes of stent migration include size mismatch between the stent and the trachea, physiological movement of the trachea, and so on. In order to solve the above problems, this study designed a non-uniform Poisson ratio tracheal stent by combining the size and structure of the trachea and the physiological movement of the trachea to improve the migration of the stent, meanwhile ensuring the support of the stent. In this study, the stent corresponding to cartilage was constructed with negative Poisson's ratio, and the stent corresponding to the circular connective tissue and muscular membrane was constructed with positive Poisson's ratio. And four kinds of non-uniform Poisson's ratio tracheal stents with different link lengths and negative Poisson's ratio were designed. Then, this paper numerically simulated the expansion and rebound process of the stent after implantation to observe the support of the stent, and further simulated the stretch movement of the trachea to calculate the diameter changes of the stent corresponding to different negative Poisson's ratio structures. The axial migration of the stent was recorded by applying different respiratory pressure to the wall of the tracheal wall to evaluate whether the stent has anti-migration effect. The research results show that the non-uniform Poisson ratio stent with connecting rod length of 3 mm has the largest diameter expansion in the negative Poisson ratio section when the trachea was stretched. Compared with the positive Poisson's ratio structure, the axial migration during vigorous breathing was reduced from 0.024 mm to 0.012 mm. The negative Poisson's ratio structure of the non-uniform Poisson's ratio stent designed in this study did not fail in the tracheal expansion effect. Compared with the traditional stent, the non-uniform Poisson's ratio tracheal stent has an anti-migration effect under the normal movement of the trachea while ensuring the support force of the stent.

Morphing flap driven by link with antagonistic shape memory alloy wires

Abstract This paper describes a study of a morphing flap using antagonistically arranged shape memory alloy (SMA) wires as actuators. The main focus of this study is to examine how existing aircraft structures and mechanisms can be modified to make the morphing airfoil more practical. The first step is to consider the drawbacks of existing morphing airfoils and then examine the advantages of the morphing airfoil proposed in this study. Then, a morphing airfoil is proposed to realize four significant technical issues: weight reduction, compatibility with existing structures, securing internal space, and seamless skin made with shape memory polymer (SMP) films. First, elemental experiments were conducted to examine the feasibility of the mechanical design, and the feasibility of the design of a large-morphing airfoil operating test model was confirmed. Next, aerodynamic and structural-mechanical analyses are conducted while designing the experimental operating model to verify whether it could operate up to the target flap angle under simulated flight conditions. After completing the experimental model, actuation tests are conducted as a morphing wing and confirm whether the wing could operate at the target flap angle in a realistic environment. As a result, the two-way morphing flap angle was experimentally observed. It is noted that only aerodynamic force was not considered in the experiment, which is further investigated in wind tunnel tests in future study. In addition, control rate of the proposed system seems improved than conventional model because of the reduction of the wire length of the actuation system. Thus, the results obtained in this study suggested the proposed link-driven SMA wire mechanism can be applied to make the morphing airfoil more practical.

Structural Design and Mechanical Properties Analysis of Laminated SiAlON Ceramic Tool Materials

Based on finite element simulation analysis, laminated ceramic tool materials with different structures were designed and the effect of laminated structure on tool state was investigated. Residual stresses in ceramic tool materials increase with the number of layers and layer–thickness ratio. Based on the simulation results, SiAlON-SiC-SiCw/SiAlON-Al2O3 ceramic tool materials (SCWAs) were prepared using the spark plasma sintering process, and the influence of residual stress on the mechanical properties and microstructure of laminated ceramic tool materials was studied. The mechanical properties of ceramic materials were significantly improved under the effect of residual stresses. The fracture toughness of SCWA4 with 7 layers and a layer–thickness ratio of 6 was 6.02 ± 0.19 MPa·m1/2, and the front and side flexural strengths were 602 ± 19 MPa and 595 ± 17 MPa, 36.3% and 39.0% higher than homogeneous SiAlON ceramics, respectively.

Discrete differential geometry-based model for nonlinear analysis of axisymmetric shells

In this paper, we propose a novel one-dimensional (1D) discrete differential geometry (DDG)-based numerical method for geometrically nonlinear mechanics analysis (e.g., buckling and snapping) of axisymmetric shell structures. Our numerical model leverages differential geometry principles to accurately capture the complex nonlinear deformation patterns exhibited by axisymmetric shells. By discretizing the axisymmetric shell into interconnected 1D elements along the meridional direction, the in-plane stretching and out-of-bending potentials are formulated based on the geometric principles of 1D nodes and edges under the Kirchhoff–Love hypothesis, and elastic force vector and associated Hessian matrix required by equations of motion are later derived based on symbolic calculation. Through extensive validation with available theoretical solutions and finite element method (FEM) simulations in literature, our model demonstrates high accuracy in predicting the nonlinear behavior of axisymmetric shells. Importantly, compared to the classical theoretical model and three-dimensional (3D) FEM simulation, our model is highly computationally efficient, making it suitable for large-scale real-time simulations of nonlinear problems of shell structures such as instability and snap-through phenomena. Moreover, our framework can easily incorporate complex loading conditions, e.g., boundary nonlinear contact and multi-physics actuation, which play an essential role in the use of engineering applications, such as soft robots and flexible devices. This study demonstrates that the simplicity and effectiveness of the 1D discrete differential geometry-based approach render it a powerful tool for engineers and researchers interested in nonlinear mechanics analysis of axisymmetric shells, with potential applications in various engineering fields.

A structural mechanics analysis on a Type IV hydrogen storage tank during refueling and discharging

High-pressure hydrogen gas, as a power generation fuel widely used in transportation, has significantly contributed to the development of hydrogen fuel cell electric vehicles. However, obvious temperature rise and drop during fast refueling and discharging cause serious safety risk to the structural stability of on-board hydrogen storage tank. The American Society of Automotive Engineers SAE J2601 and the international standard ISO 15869 strictly stipulate that the operation temperature range of hydrogen storage tank varies from −40 °C to 85 °C. In this study, a finite element mechanics model was constructed using ACP and Static Mechanical software to better understand the deformation, stress, strain, and failure modes experienced by a Type IV tank during charging and discharging. Detailed parameters such as ply angle, ply thickness, mesh generation, and boundary conditions, were extensively elucidated. The results indicate that the high temperature and pressure generated during fast fueling of the storage tanks are less likely to cause yield failure of the inner, outer layers and plug, but the stress concentration caused by low temperature and high pressure may lead to the fracture rupture of internal polyethylene materials. Aluminum alloy plug, serving as sealing devices for the tank, are most susceptible to yielding failure under coupled conditions. The mechanical load reaching the yield stress of the plug is approximately 85 MPa with the nominal working temperature of 85 °C. Additionally, the maximum stress on the outer layer can be reduced by adjusting the circumferential layer direction from 90° to 70° or by optimizing the orientation of the maximum stress layer increasing it by 110°. The present study can offer new insights into the dynamic loading behavior of the Type IV tanks during fast charging and discharging, and may provide technical references for optimization design of the tank structures.

Dynamic viscoelastic properties of ultra-large particle size asphalt mixture based on fractional derivative constitutive model

The aim of this paper was to accurately grasp and precisely characterize the dynamic viscoelastic properties of Ultra-Large Particle Size Asphalt Mixture (LSAM-50), and fully explore the features and simplified forms of the generalized fractional derivative Zener (GFDZ) model. The constitutive relations of the GFDZ model with n Abel elements were first given, and a modified GFDZ (mGFDZ) model was proposed. Then the master curves of LSAM-50, AC-13 and AC-20 mixtures were constructed, and the expression effects of different models and the dynamic viscoelastic behaviors of different asphalt mixtures were compared. The results showed that LSAM-50 was a typical viscoelastic material similar to traditional mixture. Both dynamic modulus and energy storage modulus decreased with increasing temperature. The phase angle increased first and then decreased with temperature increasing, and the peak value appeared near 40℃ at low frequency. The loss modulus increased first and then decreased with the temperature increasing. When the loading frequency was 0.1 Hz∼25 Hz, the peak value appeared at 0℃∼20℃. The rutting factors of LSAM-50 became larger with temperature reduction and frequency enhancement. When the number of Abel elements reached 2 in the GFDZ model or reached 3 in the mGFDZ model, the model fitting effects would no longer change significantly. The 2-mGFDZ model with only 5 parameters fitted master curves data satisfactorily and the physical meanings of parameters were clear. Comparing among three mixtures, LSAM-50, with the lowest asphalt content, showed significantly superior elasticity and better deformation resistance at medium and high temperatures. At low temperatures, the viscosity behavior of LSAM-50 was slightly inferior, but it may have pronounced plate properties considering the effect of aggregate skeletonization. The research results would promote new pavement structural design and mechanical response analysis.

Structure Parametric Optimization and Mechanical Analysis of the MSe1 Septum Magnet

Structure Parametric Optimization and Mechanical Analysis of the MSe1 Septum Magnet

Structural Stability and Mechanical Analysis of PVC Pipe Jacking under Axial Force

Structural Stability and Mechanical Analysis of PVC Pipe Jacking under Axial Force

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

Structural, radiation shielding, thermal and dynamic mechanical analysis for waste rubber/EPDM rubber composite loaded with Fe2O3 for green environment

Increasing waste rubber recycling produces a specious range of products for many valuable applications. Waste Rubber/EPDM composite with different concentrations was prepared. Infrared spectroscopy (FTIR) is used to identify the chemical composition. A water absorption test, Dynamic mechanical analysis (DMA), and Thermal Gravimetric Analysis (TGA) were performed. The (75/25) WR/EPDM rubber composite exhibited the best behavior with the highest mechanical performance. Fe2O3 was added to (75/25) WR/EPDM rubber composite. Water absorption, FTIR, TGA, and DMA were investigated. The composite performance was improved with increasing Fe2O3 content. The linear attenuation coefficients (μ) were also measured as a function of the concentrations of Fe2O3 for γ-ray energy 662 keV by using 137Cs point source; the radiation shielding can be denoted by numbers of parameters like mass attenuation coefficient (μm), half value layer (HVL), Tenth value layer TVL and radiation protection efficiency (RPE%), radiation protection efficiency increased as Fe2O3 increased.

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.

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.

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.

Dynamic interactions of carbon trading, green certificate trading, and electricity markets: Insights from system dynamics modeling.

In the context of the evolving landscape of reduction in carbon emissions and integration of renewable energy, this study uses system dynamics (SD) modeling to explore the interconnected dynamics of carbon trading (CT), tradable green certificate (TGC) trading, and electricity markets. Using differential equations with time delays, the study provides a comprehensive analysis of structural relationships and feedback mechanisms within and between these markets. Key findings reveal the intricate interplay between carbon prices, green certificate prices, and electricity prices under various coupling mechanisms. For example, under the three-market coupling mechanism, carbon trading prices stabilize around 150 Yuan/ton, while green certificate prices reach a peak of 0.45 Yuan/KWH, impacting electricity prices, which fluctuate between 0.33 and 1.09 Yuan / KWH during the simulation period. These quantitative results shed light on nuanced fluctuations in market prices and the dynamics of anticipated purchases and sales volumes within each market. The insights gleaned from this study offer valuable implications for policy makers and market stakeholders in navigating the complexities of carbon emission reduction strategies, the integration of renewable energy and market equilibrium. By understanding the dynamics of multi-market coupling, stakeholders can better formulate policies and strategies to achieve sustainable energy transitions and mitigate impacts of climate change.