Effect Of Elastic Deformation Research Articles

Research on the influence of flexible wheelset rotation effect on wheel rail contact force

PurposeUnder the high-speed operating conditions, the effects of wheelset elastic deformation on the wheel rail dynamic forces will become more notable compared to the low-speed condition. In order to meet different analysis requirements and selecting appropriate models to analyzing the wheel rail interaction, it is crucial to understand the influence of wheelset flexibility on the wheel-rail dynamics under different speeds and track excitations condition.Design/methodology/approachThe wheel rail contact points solving method and vehicle dynamics equations considering wheelset flexibility in the trajectory body coordinate system were investigated in this paper. As for the wheel-rail contact forces, which is a particular force element in vehicle multibody system, a method for calculating the Jacobian matrix of the wheel-rail contact force is proposed to better couple the wheel-rail contact force calculation with the vehicle dynamics response calculation. Based on the flexible wheelset modeling approach in this paper, two vehicle dynamic models considering the wheelset as both elastic and rigid bodies are established, two kinds of track excitations, namely normal measured track irregularities and short-wave irregularities are used, wheel-rail geometric contact characteristic and wheel-rail contact forces in both time and frequency domains are compared with the two models in order to study the influence of flexible wheelset rotation effect on wheel rail contact force.FindingsUnder normal track irregularity excitations, the amplitudes of vertical, longitudinal and lateral forces computed by the flexible wheelset model are smaller than those of the rigid wheelset model, and the virtual penetration and equivalent contact patch are also slightly smaller. For the flexible wheelset model, the wheel rail longitudinal and lateral creepages will also decrease. The higher the vehicle speed, the larger the differences in wheel-rail forces computed by the flexible and rigid wheelset model. Under track short-wave irregularity excitations, the vertical force amplitude computed by the flexible wheelset is also smaller than that of the rigid wheelset. However, unlike the excitation case of measured track irregularity, under short-wave excitations, for the speed within the range of 200 to 350 km/h, the difference in the amplitude of the vertical force between the flexible and rigid wheelset models gradually decreases as the speed increase. This is partly due to the contribution of wheelset’s elastic vibration under short-wave excitations. For low-frequency wheel-rail force analysis problems at speeds of 350 km/h and above, as well as high-frequency wheel-rail interaction analysis problems under various speed conditions, the flexible wheelset model will give results agrees better with the reality.Originality/valueThis study provides reference for the modeling method of the flexible wheelset and the coupling method of wheel-rail contact force to the vehicle multibody dynamics system. Furthermore, by comparative research, the influence of wheelset flexibility and rotation on wheel-rail dynamic behavior are obtained, which is useful to the application scope of rigid and flexible wheelset models.

Analysis to the dynamic response of a functionally graded spherical microshell in consideration of fractional-order dual-phase-lag heat conduction and nonlocal effect

Functionally graded materials (FGMs) stand as one of the most representative composite materials due to the superior thermal resistance in non-isothermal environment. On another front, the applicability of integer-order heat conduction models is increasingly questionable because the heat transfer shares the history-dependent property at time microscale. It is noted that the small-scale effect of elastic deformation has become significant due to the development of micro-devices. To capture the small-scale effect of elastic deformation and the memory-dependent effect of heat conduction in the FGM microstructures, as a first attempt, the present study focuses on developing a thermoelastic model by incorporating the fractional-order dual-phase-lag (FODPL) heat conduction model and the Eringen’s nonlocal model. Moreover, the extension of the Caputo definition, i.e., the Tempered-Caputo (TC) definition of fractional derivative ruling out singular kernel is adopted to depict the memory-dependent effect of the heat conduction. Then, the modified model is used to investigating the dynamic response of a FGM spherical microshell subjected to a sinusoidal thermal-mechanical loading. The corresponding governing equations are formulated and then solved by Laplace transform techniques. Some parametric results are demonstrated to display the influences of the fractional-order parameter, the nonlocal parameter and the power-law index on the considered physical quantities.

Effect of elastic deformation on the heat transfer characteristic of refrigerator gasket based on static analysis of structural assemblies

ABSTRACT Soft and hard contact deformation is most common issue of the refrigerator gasket and it has almost been ignored in previous studies. In this paper, the novelty is to propose a thermal-solid coupling simulation to study the effect of assembly states on the heat transfer of gaskets, improving the accuracy of heat transfer simulation analysis. The numerical results indicate that the calculated temperature based on physical model of assembly state is closer to measured temperature. The assembly distance affects the assembly state of the gasket by changing the contact positions and lengths of contact interfaces. As a result, the heat transfer path and condition at the gasket region also changes. As the deformation increases form −1.0 mm to 5.0 mm, the heat leakage load of gasket rises firstly and then falls, in the range of 1.61 ~ 3.33 W•m−1. The heat leakage at the transfer paths of internal cold air, outer shell and cold bridge accounts for over 20%. Thus, it is recommended to reduce the contact interface length of internal cold air, increase the thermal resistance of auxiliary air-bag, reduce the thermal conductivity and thickness of magnetic strip and increase the contact thermal resistance of cold bridge.

Aerodynamic performance of a flyable flapping wing rotor with dragonfly-like flexible wings

Drawing inspiration from insect flapping wings, a Flapping Wing Rotor (FWR) has been developed for Micro Aerial Vehicle (MAV) applications. The FWR features unique active flapping and passive rotary kinematics of motion to achieve a high lift coefficient and flight efficiency. This study thoroughly investigates the aerodynamic performance and design of a bio-inspired flexible wing for FWR-MAVs, emphasizing its novel backward-curved wingtip and variable spanwise stiffness resembling a dragonfly's wing. The research departs from previous aerodynamic studies of FWR, which focused predominantly on rectangular and rigid wings, and delves into wing flexibility. Employing Computational Fluid Dynamics (CFD), Computational Structural Dynamics (CSD), and experimental measurements, the study demonstrates the aerodynamic benefits of the dragonfly-inspired FWR wingtip shape and its reinforced structure. Fluid-Structure Interaction (FSI) analysis is used to examine the effects of elastic deformation encompassing twist and bending on aerodynamic forces. The results underscore the importance of bending deformation in enhancing lift and power efficiency and propose a method for analysing variable stiffness along the wingspan using a vortex delay mechanism that is induced by delayed flapping motion. By comparing modelled and measured stiffness, the study validates the flexibility of the FWR wing, revealing optimal aerodynamic efficiency is achieved through moderate flexibility and spanwise stiffness variation. The curving leading-edge beam forming the sweep-back wingtip offers a practical approach to obtaining variable stiffness and aerodynamic benefits for FWR-MAVs. Using the same pair of dragonfly-like flexible wings, FWR-MAVs have effectively exhibited VTOL and hovering flight capabilities, spanning from a 25-g single-motor drive model to a 51-g dual-motor drive model. This research provides valuable insights into flexible wing design for FWR-MAVs, leveraging biomimicry to improve flight efficiency.

Flow-induced rearrangement of a poroelastic cluster

Although poroelastic clusters in nature, such as bristled wings and plumed seeds, exhibit remarkable flight performances by virtue of their porous structure, the effects of another key feature, elasticity, on aerodynamic loading remain elusive. For a poroelastic cluster, we investigate the aerodynamic effects of elastic deformation that occurs through the collective rearrangement of many elastic components and the fluid-dynamic interactions between them. As a simple two-dimensional model, an array of multiple cylinders which are individually and elastically mounted is employed with diverse values of porosity and elasticity. Under a uniform free stream, the poroelastic cluster enlarges its frontal area and augments the total drag force in the quasi-steady state; this is in contrast to the general reconfiguration of fixed elastic structures, which tends to reduce the frontal area and drag. The rearrangement of the poroelastic cluster is dominated by the virtual fluid barrier that develops in a gap between the elastic components, interrupting the flow penetrating between them. The effects of this hydrodynamic blockage on changes in the frontal area and drag force are analysed in terms of porosity and elasticity, revealing the fluid-dynamic mechanism underlying the appearance of peak drag at an intermediate porosity. Moreover, to represent the coupled effects of porosity and elasticity on the rearrangement, a scaled elastic energy is derived through a consideration of the energy balance.

Temperature evolution prediction of engine big-end bearing by tribo-dynamics modeling and wireless measurement verification

Thermally-induced seizure (TIS) issue of the big-end bearing could lead to catastrophic engine failures. Evaluating bearing temperature during the design phase effectively identifies this issue in advance. However, accurate prediction remains challenging due to complex influencing factors and variable friction states. This work develops a more comprehensive model for the big-end bearing temperature evolution by tribo-dynamics modeling considering the effects of lubricant rheology and elastic deformation. Wireless measurements of bearing temperature are conducted in a full-size engine at rated conditions. Coupling simulations and tests provide an in-depth understanding of bearing temperature and tribo-dynamics behavior. Results reveal the experimental bearing achieves 133 ℃ at the focus positions. The simulated bearing temperature corresponds nicely to the test one with a difference of 1.55 ℃.

On the habit planes between elastically distorted austenite and martensite in NiTi

The cubic B2 to monoclinic B19’ martensitic transformation in NiTi shape memory alloys proceeds by the nucleation and propagation of habit plane interfaces that remain undistorted and unrotated during the transformation. Due to incompatibility of austenite and martensite lattices in NiTi, habit plane interfaces are assumed to form between austenite and twinned martensite as described by Phenomenological Theory of Martensite Crystallography (PTMC). This view is currently widely spread in the literature in spite of the fact that it contradicts experimental observations of interfaces between austenite and single martensite lattice by TEM and EBSD methods frequently reported in the literature. On this account, we propose a different solution for the formation of strain compatible habit planes propagating during stress induced martensitic transformation by considering the effect of elastic deformation of both lattices caused by the external stress. Using modified PTMC theory, we evaluate the magnitudes of the uniaxial stress in tension and compression along a general austenite crystal direction, for which strain compatible habit plane interfaces can be established between austenite and single variant of martensite. The stress calculated in such a way is, however, too high. Nevertheless, considering the pre-transformation softening of austenite, the critical stress decreases to 500 MPa commonly observed in experiments. Three scenarios are simulated assuming softening of elastic constants of austenite. Orientation dependence and tension-compression asymmetry of predicted habit planes of stress induced martensitic transformation is compared with available experimental results.

Effect of elastic deformation on lubrication characteristics in different clearances and head size of metallic artificial hip joint

The issue of lubrication in metallic artificial hip joints is discussed to prevent the two bearing surfaces from contacting each other. This study aims to analyse the characteristics of elastohydrodynamic lubrication (EHL) and investigate the effect of radial clearance and head size on the tribological performance of metallic artificial hip joints under steady-state conditions using the Fluid-Structure-Interaction (FSI) method. The average load in the z-direction and flexion-extension motion around the y-axis were used to represent normal walking. This study demonstrates that the film thickness profile from the validation study aligns with the findings of the previous study. The contour of the fluid pressure in the central contact zone changes with different time steps – the direction of fluid movement corresponds to the solid-fluid reaction. Additionally, the deformation of the cup surfaces contributes to the continuous fluid film that separates the contact surfaces. Furthermore, design parameters also influence EHL performance. It has been discovered that less radial clearance and a larger head size led to an increase in fluid film thickness.

Experimental characterization of damage during geothermal production of hot dry rocks: Comprehensive effects of the damage-elastic deformation on conductivity evolution

The development of hot dry rocks (HDRs) is of great significance to adjusting energy structure, alleviating energy shortage, reducing pollution, etc. Low-permeability granite is the predominant rock type in deep HDRs, making fractures the primary pathways for fluid circulation and heat extraction. The production of HDRs is significantly influenced by variable fracture conductivity, but current conductivity characterization primarily relies on the elastic deformation of the matrix, neglecting the impact of damage. Accordingly, we propose an experimental method and a supporting apparatus, which is used to unveil the conductivity evolution characteristics resulting from the comprehensive effects of damage and elastic deformation. The experimental results demonstrate that when subjected to confining force squeezing inward, the fracture conductivity experiences varying degrees of decrease compared to its initial state before the experiment. By utilizing the conductivity evolution rate as the evaluation criterion and conducting grey correlation analysis, it has been determined that temperature exerts the most significant influence on the conductivity evolution, followed by injection flow, and lastly, confining pressure. Moreover, rock particle types and production cycles also have different degrees of effect. After considering the comprehensive effects of damage-elastic deformation at the field-scale, the damage has a positive effect on conductivity enhancement. Our study provides a new approach for the characterization of fracture conductivity evolution for deep geothermal projects.

Fractional dual-phase-lag thermal-mechanical response of an functionally graded spherical microshell with size-dependent effect

Functionally graded materials (FGM) have attracted much attention due to their superior thermal shock resistance in extreme thermal environment. In addition, the memory-dependent feature of transient heat transfer progress can’t be reflected in the frame of integer-order heat conduction model due to the inability of depicting the effect of the past states on the current state. It is noticed that the size-dependent effect of elastic deformation has become significant due to the development of micro-devices. To describe the memory-dependent effect and the size-dependent effect in the functionally graded microstructures, the work aims a thermoelastic model by incorporating the fractional dual-phase-lag heat conduction model and the Eringen’s nonlocal model. To illustrate its application values, the modified model is used to investigate the dynamic performance of an functionally graded spherical microshell subjected to a thermal-mechanical loading. Governing equations including the modified parameters are derived and solved by Laplace transformation. The achieved results show that considering the influences of nonlocal effect and ceramic composition will reduce the thermal deformation under ultrafast heating condition.

Dynamic performances of novel misaligned non-uniform distributed tilting-pad bearing

The non-uniform distributed tilting-pad journal bearings (NDTPJB) in large wind turbine main shafting has become an important development trend for high-power wind turbines due to the advantages of improving reliability and reducing maintenance costs. However, studies involving NDTPJB have not been reported under specific conditions such as low speed, wide range variable direction and magnitude of heavy-load in wind turbine. A new transient mixed elastohydrodynamic lubrication (mixed EHL) model for NDTPJB is established, taking into account the misalignment effect of the shaft tilt and the swinging of pads in the circumferential and axial directions, as well as the influence of pivot friction and elastic deformation effects. Based on the mathematical model, the dynamic characteristics and structural parameter effects of NDTPJB are systematically studied under low speed, wide range variable direction and magnitude of heavy-load. The results indicate that the NDTPJB exhibits a more significant sensitivity to the heavy load direction due to the different functional roles of the above distributed pads (ADP) and bottom distributed pads (BDP). The modified mixed EHL model can more accurately evaluate the lubrication performance of NDTPJB, and combine the characteristics in individual pad swing and the overall effect of the pads to comprehensively analyze the dynamic lubrication behavior of NDTPJB. By setting the pivot coefficient to 0.55, reducing the distribution angle of BDP, and increasing the distribution angle of ADP, a better load-carrying capacity can be achieved. The research results have guiding significance for further monitoring and analyzing the experimental performance of NDTPJB, as well as designing and optimizing such bearing structures.

Characterization of low-velocity and low-energy responses of elastic-plastic plate struck by elastic-plastic impactor

This paper presents a study on the characterization of low-velocity and low-energy impact responses of elastic-plastic plate struck by elastic-plastic spherical impactor. The applicability of the existing impact characterization diagram is examined firstly by intensive finite element (FE) simulations for a wide range of complicated impact situations including all three types of contact: indentation, flattening and combined flattening and indentation. The limitations of the existing diagram are found in identifying the type of impact response and predicting the maximum impact force for complicated impact situations. The effects of elastic and plastic deformations of impactor on the identification and prediction by the existing diagram are analyzed. A new linear contact law is presented according to the piecewise linear characteristics of contact stiffness observed from the intensive FE results. An extended impact characterization diagram is then proposed to characterize low-velocity and low-energy impact responses of plate under complicated impact situations with arbitrary three contact types. The extended diagram is validated by the intensive FE simulations and experimental results. It is concluded that the extended impact characterization diagram can identify correctly the plate response type to complicated impacts and predict accurately the maximum impact force in a fast and simple way without the aid of FE models and experimental tests.

Effect of Surface Elastic Deformation in Hydrodynamic Inclined Fixed Pad Thrust Bearing with Low Clearance

The paper analytically studies the effect of surface elastic deformation in hydrodynamic inclined fixed pad thrust slider bearing with low clearances by the multiscale approach considering the physically adsorbed layer on the bearing surface. The numerical calculation results show that the bearing surface elastic deformation has significant influences on both the hydrodynamic pressure and the surface clearance in the bearing especially for a strong fluid-bearing surface interaction. For given load, sliding speed and bearing geometrical sizes, the surface elastic deformation considerably reduces the minimum bearing clearance, which exists on the exit of the bearing. It also significantly reduces the hydrodynamic film stiffness and the load-carrying capacity of the bearing especially for a strong fluid-bearing surface interaction and low bearing clearances. The increasing proportionality of the carried load of the bearing with the sliding speed is also significantly reduced by the surface elastic deformation particularly for a strong fluid-bearing surface interaction.

Robust polyurea icephobic coatings with static large-scale de-icing and dynamic anti-icing performance

Ice accumulation significantly affects the operation of infrastructure and the safety of transportation. Passive icephobic materials utilize inherent properties to achieve anti-icing performance, which has the benefits of no energy consumption and environmental protection. However, their degraded robustness in harsh environments severely limits practical applications. It is still a challenge to prepare icephobic materials that maintain both icephobicity and robustness. In this study, we propose a rational strategy for revolutionarily achieving both icephobicity and robustness by adopting a combination of soft and hard segments impregnated with the lubricant agent. Based on the strategy, the polyurea icephobic coating (PUIC) developed by the NCO-terminated prepolymer, polyaspartic ester, and dimethyl silicone oil ensures rapid and nondamaging ice detachment on the interface (low ice adhesion strength ∼23.7 kPa) via the synergistic effects of hydrophobicity, elastic deformation, and interfacial slippage. In addition, the resulting PUIC can reserve icephobicity under not only continuous 5000 Taber abrasion cycles before the complete wearing off the coating, but also 50 icing/de-icing cycles, 72 h acid/alkali immersion, 72 h UV radiation, and 240 h neutral salt spray. Furthermore, the destroyed PUICs can be recovered by organic solvents and maintain excellent icephobicity. Together with icephobicity, robustness, and scalability, PUICs are effective in static large-scale de-icing and dynamic anti-icing, with broad prospects in practical applications.

Effect of cavitation on fluid-structure interaction of a cantilever hydrofoil

In this work, a study of the cavitation fluid-structure interaction characteristics of a trapezoidal elastic NACA 0009 (mod) hydrofoil is conducted. The simulation includes the Schneer–Sauer cavitation model and two-way fluid-structure interactions (FSI). A large-eddy simulation (LES) is used to simulate the effects of cavitation and elastic deformation on the hydrodynamic performance. First, the reliability of the numerical method is verified through mesh strategy convergence analysis. On this basis, the vibration response and cavitation behavior of the hydrofoil are investigated. The results indicate that the hydrodynamic and vibration responses of the overall flow state are changed by the cavitation and fluid-structure interaction. In contrast to the case of a rigid hydrofoil, cavitation on an elastic hydrofoil shows periodic variation. This phenomenon causes the hydrofoil vibration mode to be close to the first and second natural frequencies. Additionally, the frequency of lock-in vibration is close to the hydrofoil's first bending mode due to elasticity. We believe that under similar conditions and structural materials, our results have a certain degree of generalizability.

Kinetostatics modeling and elasto-geometrical calibration of overconstrained parallel manipulators

Overconstrained parallel manipulators have garnered increasing attention due to their higher stiffness resulting from redundant wrenches and improved performance by eliminating clearances and backlashes through forced assembly, as compared to non-overconstrained counterparts. However, a challenge arises in calibrating these manipulators due to non-ideal geometry, which introduces mechanical strains in the structure. Consequently, identifying the geometrical errors of the manipulators becomes difficult without considering the effect of elastic deformations. The primary contribution of this work is to propose an efficient kinetostatic modeling and elasto-geometrical calibration method that enables simultaneous identification of both geometric parameters and compliance parameters in overconstrained parallel manipulators. Initially, a kinetostatic model considering both geometric errors and flexible deformations is proposed using an error equivalent method. Subsequently, a unified error model encompassing geometric and compliance parameters is derived through projection operations. To validate the effectiveness of the proposed method, experiments are conducted on a 3-DOF translational manipulator. The results demonstrate a significant reduction in residual errors of the manipulator using the proposed approach.

Numerical simulation of the effect of elastic deformation on the fairing separation process

In view of the potential impact of structural deformation on the separation safety of elastic fairing at low altitude and high speed, the aerodynamic/deformation/motion coupling analysis method is established. The numerical simulation of the separation process of the fairing considering elastic deformation after disengaging is carried out. The motion characteristics and structural response characteristics of the elastic fairing in the separation process are obtained. Moreover, the impact of elastic deformation on the attitude and trajectory of the fairing is studied. The results indicate that the elastic deformation has an impact on the attitude and trajectory of the fairing after hinge decoupling. However, for the calculation conditions in this paper, elastic deformation has no subversive effect on the separation safety.

Investigation on mixed thermalelstohydrodynamic lubrication behavior of slipper/swash plate interface in water hydraulic axial piston pump

To reveal the thermal-fluid-structure interaction characteristics of water-lubricated slipper/swash plate interface, a transient mixed thermoelstohydrodynamic (MTEHD) lubrication model incorporating asperity contact, elastic deformation, heat transfer and viscosity temperature effect is originally presented. The change in fluid properties caused by cavitation is considered for solution the piston chamber pressure. Distributions of pressure, temperature, deformation and tilting state of slipper simulated by MTEHD show strong reasonableness. Effect of operating and structural parameters on energy consumption characteristics calculated by MTEHD and hydrodynamic lubrication is contrastively analyzed. The results show that energy consumption is different in delivery and suction stroke due to different degrees of MTEHD effects and transient contact. Besides, the optimal dimension for the width of studied sealing surface is determined.

A new tribo-dynamics model for engine connecting rod small-end bearing considering elastic deformation and thermal effects

The connecting rod small-end bearing system is one of engine's rotating friction pairs under the most severe condition. Significant deformation, high temperature, and the coupling action of multi-bearing tribology and multi-body dynamics make the simulation challenging. This study develops a new tribo-dynamics model considering deformation and thermal effects for the small-end bearing system. A full-scale engine test is conducted, and the predicted severe wear position is consistent with the experimental one. Results show the axial uneven wear and temperature rise happens in the bearing lower surface after considering elastic deformation and thermal effects. The piston pin is decelerated to stop nearly and then accelerated by the friction torque during compression and work strokes that differs from the simplified rigid model.

Molecular Dynamics Simulation of Droplet Impact on a Hydrophobic 3D Elastic Surface.

The phenomenon of droplets impacting elastic surfaces is common in nature and in many engineering applications. It has been shown that droplet impact on an elastic surface drastically reduces droplet contact time and hinders droplet spreading. However, most of the current studies are based on experiments, and the analysis of the influence mechanism of the elastic substrate on the dynamic behavior of droplets is not complete. In addition, the simulations of droplet impact on elastic substrates are mainly focused on 2D elastic films or vibrating rigid substrates, ignoring the effect of 3D elastic substrate deformation on the droplet dynamic behavior. Therefore, in this paper, we propose to model the droplet impact on a 3D hydrophobic elastic substrate using the molecular dynamics method. We find that droplet pancake rebound can substantially reduce the droplet contact time. Moreover, we record the conditions required for the pancake rebound of the droplet. Furthermore, we investigated the effects of the elastic modulus of the substrate and the initial velocity of the droplet on the droplet contact time, contact area, and spreading factor. This study further elucidates the influence mechanism of the elastic substrate on the dynamic behavior of the droplet and provides theoretical guidance for regulating the dynamic behavior of the droplet in related fields.