Effect Of Elastic Deformation Research Articles

Ferro‐elastohydrodynamic lubrication of inclined slider‐bearing

AbstractIn practice, due to bearing load there is a generation of pressure in the lubricant film, which leads elastic deformation on the bounding surfaces and causes variation in the film thickness. As film thickness plays an important role in performance of the slider‐bearing designs; an attempt has been made to study numerical simulation of elastic deformation effect in one‐dimensional inclined slider‐bearing with ferrofluid (FF) lubricant. The modified Reynolds equation is derived using ferrohydrodynamic theory by Shliomis with transverse uniformly strong magnetic field, and continuity equation. Using this equation dimensionless load‐carrying capacity () is studied for different parameters. The results show the better performance of for lower convergence ratio and higher effective viscosity. However, elastic deformation has no effect on . Some comparisons are also made with the previous literature.

Improved Permeability Model of the Binary Gas Interaction within a Two-Phase Flow and its Application in CO2-Enhanced Coalbed Methane Recovery.

In this paper, we develop a dual-porosity dual-permeability model for binary gas migration to explore the permeability evolution in the matrix and fracture in the process of a gas–water two-phase flow during CO2-enhanced coalbed methane (CO2-ECBM) recovery in coal reservoirs. This mechanistic model accommodates the effects of elastic deformation caused by the effective stress change in the matrix and fracture, the swelling/shrinkage deformation of the matrix caused by adsorption/desorption, the convection and diffusion of gas, and the discharge of water. Specifically, the time-dependent matrix swelling, from initially completely reducing the fracture aperture to finally affecting the coal bulk volume, is considered by the invaded volume fraction involving binary gas intrusion. The model is validated through laboratory data and applied to examine the permeability evolution of CO2-ECBM recovery for 10 000 days. Furthermore, we analyze the sensitivity of some selected initial parameters to capture the key factors affecting CO2-ECBM recovery. Our modeling results show that the permeability evolution can be divided into two stages during the process, where stage I is dominated by effective stress and stage II is dominated by adsorption/desorption. Increasing the injection pressure or initial permeability advances the start of stage II. The decrease in initial water saturation causes the permeability to change more drastically and the time of stage II to appear earlier until a time long enough, after which little effect is seen on the permeability results.

Experimental Investigation into the Effect of Elastic Deformation of Plates on the Friction Resistance of Plate Heat Exchangers

Experimental Investigation into the Effect of Elastic Deformation of Plates on the Friction Resistance of Plate Heat Exchangers

In situ investigation of the influence of varying load conditions on tooth deformation and wear of polymer gears

A new method for in situ deformation and wear measurement of polymer gears has been developed at the LKT and validated for polyamide-66 (PA66) gears at constant loading torque and rotational speed. This contribution contains a more comprehensive validation of the newly developed test method by examining polybutylenterephtalate (PBT) gears under varying loading conditions. The deformation test method is based on measuring and analysing the timing differences between the index pulse signals of rotary encoders on the input and output shaft of the test rig. Since the total tooth deformation is a combination of different effects, such as elastic and plastic deformation, thermal expansion and wear, different testing modes with a low and a high torque level are implemented to separate the effects of elastic deformation on the one hand and plastic deformation and wear on the other hand. As a consequence, the new test rig design allows a deeper understanding of the wear and deformation behaviour of polymer steel gear sets over time. This potential is used to analyse the interactions of different loading conditions on the time-dependent deformation of plastic gears. The influence of both, different transmitting torques and rotational speeds is examined.The test method shows good correlation with well-established ex situ measurements for different combinations of rotational speeds and loading torques and thus could be validated. Long-term gear tests under varying rotational speeds and loading torques show increasing wear and deformation at higher speeds and torques confirming the state of the art described in the literature. In addition, the time dependent deformation behaviour at different load conditions due to superposition of wear and plastic deformation could be analysed in detail.

An EHL Extension of the Unsteady FBNS Algorithm

Many engineering applications rely on lubricated gaps where the hydrodynamic pressure distribution is influenced by cavitation phenomena and elastic deformations. To obtain details about the conditions within the lubricated gap, solvers are required that can model cavitation and elastic deformation effects efficiently when a large amount of discretization cells is employed. The presented unsteady EHL-FBNS solver can compute the solution of such large problems that require the consideration of both mass-conserving cavitation and elastic deformation. The execution time of the presented algorithm scales almost with Nlog (N) where N is the number of computational grid points. A detailed description of the algorithm and the discretized equations is presented. The MATLAB^{copyright } code is provided in the supplements along with a maintained version on GitHub to encourage its usage and further development. The output of the solver is compared to and validated with analytical, simulated, and experimental results from the literature to provide a detailed comparison of different discretization schemes of the Couette term in presence of gap height discontinuities. As a final result, the most favorable scheme is identified for the unsteady study of surface textures in ball-on-disc tribometers under EHL conditions.

The effects of couple stress lubricants and surface roughness on squeeze EHL motion between porous medium layer and elastic ball

This paper investigated the effects of porous media layer (PML) and couple stress (CS) lubricants at pure squeeze action in an isothermal elastohydrodynamic lubrication (EHL) point contact with surface roughness (SRN) under constant load condition. The modified transient stochastic Reynolds equation was derived in polar coordinates by means of the Christensen’s stochastic theory and the Stokes’s CS fluid theory. The Gauss-Seidel method (GSM) and the finite difference method (FDM) were both used to solve simultaneously modified transient stochastic Reynolds, force equilibrium, elasticity deformation, and rheology equations. The simulation results revealed that the greater permeability ( K) and porous layer thickness (Φ) are, the smaller central pressures ( Pc) are, and the smaller film thicknesses ( H) are. The times required for achieving maximum central pressures (Pcmax) decrease with increasing K and Φ. Due to squeeze and elastic deformation effects, the slope values of central velocity ( Vc) change from negative to positive. The magnitude of Vc and Vmin decreased with decreasing K and Φ. The Hcmin of circular type RN are greater than that of radial type RN. The Pcmax of radial type RN are slightly greater than that of circular type RN.

Elastic deformation of liquid spiral groove face seals operating at high speeds and low pressure

The uneven distribution of fluid pressure in the spiral groove area leads to the elastic deformation of the seal faces, which not only affects the sealing performance but also affects the running stability. In this paper, a numerical model of a high-speed spiral groove liquid face seal is proposed with the consideration of elastic deformation and cavitation medium compressibility. The novelty of this study is that the pressure of the cavitation region is modeled as an uneven distribution rather than as a constant. This uneven pressure distribution of sealing surfaces is generally regarded to have an influence on face deformation. Based on the assumption that the fluid exists at a complete gas state in the cavitation, the elastic deformation and pressure distribution of sealing surfaces are calculated. The influence of elastic deformation on sealing performance is further investigated. Results show that the elastic deformation of sealing surfaces and cavitation effect has a significant influence on the stability of sealing clearance, which may produce a negative effect on the sealing performance of liquid face seals. The face deformation causes a divergent gap between two seal faces. With the increase of rotational speed, the elastic deformation of sealing surfaces reduces at low seal pressure but increases at higher seal pressure, which may influence the cavitation behavior and pressure distribution of surfaces. Furthermore, the sealing performance of spiral groove liquid face seal becomes more complicated because of the coupling effect of cavitation effect and elastic deformation. The changing trend of sealing performance is different under various seal clearance and seal pressure. The obtained results may provide guidance for the future design of liquid face seals in engineering applications under high-speed conditions.

Effect of elastic deformations on direct polymorphic transformations in BN under pressure

This paper gives an investigation of the effect of shear deformation on direct transitions in BN under pressure. The transition of a hexagonal (graphite-like) phase h-BN into a cubic (“sphalerite”) c-BN through the intermediate rhombohedral phase r-BN, at a pressure P = 3.0 GPa, is shown. With shear deformation applied, the mechanism of h-BN transformation into the hexagonal (wurtzite) phase w-BN changes, and the following planes are parallel in the phases: for P = 5.0 GPa and deformation ε = 0° (001)h|| (001)w; and for P = 5.0 GPa and deformation ε ≅ 7.2 (001)h|| (100)w. The shear deformation at 6–17 GPa leads to the reverse transition of w-BN to h-BN and the observed orientation relationship is different from the one occurring at the thermal transformation of w-BN to h-BN (T ≅ 1600 K) at a pressure P = 0.1 MPa.

Combined effects of elastic deformation and piezo-viscous dependency on the performance of a journal bearing operating with a non-Newtonian fluid

A theoretical study of the effects of elastic deformation and the variation of viscosity with pressure on the performance characteristics of a circular journal bearing lubricated with non-Newtonian fluids. The Barus law and the power law model are used to express the viscosity-pressure variation and the non-Newtonian behavior of fluids respectively. To determine the displacement field at the fluid film bearing liner interface, the elastic thin liner model is used. The modified Reynolds equation accounting the viscosity pressure dependency in the non-Newtonian fluids is mathematically derived and solved using finite difference method, to obtain the fluid film pressure field. The static performance characteristics for finite-width journal bearing are evaluated for various values of pressure-viscosity coefficient, the power law index n, and the elastic deformation coefficient. According to the results obtained, it is found that the hydrodynamic pressure and non-dimensional load-carrying capacity increase as the power law index and pressure-viscosity coefficient increases especially for rigid and heavily loaded bearing case. In addition, the combined effects of the elastic deformation and the viscosity pressure dependency are found to be more pronounced on the performance characteristics of a heavily loaded journal bearing operating with a shear-thickening fluid.

Evaluation of the roll elastic deformation and thermal expansion effects on the dimensional precision of flat ring rolling products: A numerical investigation

Ring rolling is a near-net shape forming process that produces ring products with relatively good dimensional accuracy. Two main factors that lower the precision of the final products are the inability to determine the effects of elasticity and the thermal expansion of rolls during the process. This work focuses on the creation and evaluation of suitable finite element models of a ring rolling process based on available experimental data found in literature. Through these numerical models, the elastic and thermal deformations of the rolls were thoroughly studied and the deformation effect on the produced ring was predicted. A difference of a few millimeters was calculated on the outer and inner diameters of the ring as a result of the two effects, which is far greater than the annotation levels of these products. On the other hand, the effects of the tools’ elasticity and thermal expansion of the ring rolling loads were proven negligible. Based on our analysis it was made clear that slight deformation deviations (thermal and elastic deformations) from the targeted values may cause instabilities to the process if the rolls fail to compensate for these deformations. Material combinations seem to influence the process. Regarding final dimensional deviations it can be concluded that thermo-elastic tool deformations are considerable in case of high product precision requirements.

Accounting for GIA signal in GRACE products

SUMMARY The Gravity Recovery and Climate Experiment (GRACE) observes gravitational potential anomalies that include the effects of present-day surface mass change (PDSMC)- and glacial isostatic adjustment (GIA)-driven solid Earth mass redistribution. Therefore, GIA estimates from a forward model are commonly removed from GRACE to estimate PDSMC. There are several GIA models and to facilitate users in using a GIA model of their choice, both GRACE and GIA products are made available in terms of global gridded fields representing mass anomaly. GRACE-observed gravitational potential anomalies are represented in terms of equivalent water height (EWH) with a relation that accounts for an elastic solid Earth deformation due to PDSMC. However, for obtaining GIA EWH fields from GIA gravitational potential fields, two relations are being used: one that is similar to that being used for GRACE EWH and the other that does not include an elastic deformation effect. This leaves users with the possibility of obtaining different values for PDSMC with a given GRACE and GIA field. In this paper, we discuss the impact of this problem on regional mass change estimates and highlight the need for consistent treatment of GIA signals in GRACE observations.

Determining geometrical deviations of crankshafts with limited detection possibilities due to support conditions

This article is a continuation of previous research in which we analysed the effect of deflections and elastic deformations caused by unsupervised support conditions on the measurements of geometrical deviations of large crankshafts. Supporting the shaft using a set of rigid supports at the same height limited the ability to detect deviations in the pin axis position and pin profile. Formula for supporting crankshaft measurements was proposed using the results and metrology fundamentals, which allowed the accurate assessment of the geometric state under such conditions. The results provide solutions for measuring large crankshafts while eliminating the imperfections of current shaft measurement techniques. In result a high correlation (correlation coefficent at level 0.9935) with datum-based method was obtained. Therefore it was stated than proposed formula largely eliminates the disadvantages of shaft measurements using V-blocks with rigid supports.

Elastodynamic model for flapping-wing micro aerial vehicle

Lightweight design is key to high efficiency and long durability of micro air vehicle (MAV), while it will inevitably reduce the stiffness of the structures and affect the motion of the mechanism. In this study, an elastodynamic model for flapping-wing MAV (FMAV) is established to unveil the effect of elastic deformation of transmission mechanism on the flapping motion. Based on kineto-elastostatic analysis, an elastodynamic model of the transmission mechanism is built, which reveals that the inertial force of the transmission mechanism for typical FMAV is much smaller than the force transmitted. Thus, the inertial force can be ignored, and analytical formula between the deformation of transmission mechanism and the flapping angle is derived. Finite element method (FEM) simulations are conducted to validate the analytical formula, and the results show that the flapping angle obtained from the analytical formula matches well with FEM simulations. The proposed elastodynamic model and analytical formula will provide theoretical guidance for designing and optimizing FMAV with desired transmission mechanism and flapping motion.

A Universal Approach to Tire Forces Estimation by Accelerometer-Based Intelligent Tire: Analytical Model and Experimental Validation

ABSTRACT Efforts to improve the performance and safety of vehicles include placing active sensing components (e.g., embedded microsensors) within tires result in intelligent tires. One application of intelligent tire is tire force estimation based on accelerometers. However, its development is limited due to the difficulty of relating the tire force to kinematical information by model-based theory. In this manuscript, a universal approach to tire forces estimation by the accelerometer-based intelligent tire is formulated and experimentally validated. First, a microelectromechanical system accelerometer-based intelligent tire prototype is established with the function of on-board monitoring of tire forces. Then, a theoretical rolling kinematics model is proposed for illustrating the mechanisms of acceleration fields, resulting from the coupling effect of rigid body motion and elastic deformation. An analytical model is formulated to estimate the vertical force in real time. Furthermore, the beam model is adopted to describe lateral deformations of the tire belt, directly linking lateral acceleration and lateral force. Finally, the lateral force can be estimated by lateral acceleration and vertical force already estimated. Based on a universal analytical model, the lateral force estimation method realizes high accuracy under different circumstances, even with unified coefficients, by clarifying and eliminating the influence of ply steer. A field test and two bench experiments have been conducted to fully validate the developed model. It can be concluded that the theoretical-analysis-based estimation model realizes an encouraging tire force estimation application with an intelligent tire hardware system.

A fully-coupled water-vapor flow and rock deformation/damage model for shale and coal: Its application for mine stability evaluation

Roof instability is a pervasive hazard that may cause injuries and fatalities in underground coal mines. Variations in air humidity and the duration of roof exposure are known to significantly influence the stability of shale roof strata. Moisture-sensitive shales progressively deteriorate over time due to humidity-interaction and matrix swelling which can trigger skin failure and roof falls. Quantifying the evolution of dynamic mechanical and petrophysical properties of the shale roof requires a comprehensive understanding of the retention behavior of multiphase fluids in the shale and of the induced alterations associated with air-water-shale/coal interactions. This study presents a mechanism-based framework for modeling the integrative deformation and failure behaviors of the rock structure, shale roof and coal pillar—and integrates the coupled effects of water vapor flow, elastic deformation, and damage. A Time-Dependent Rock-Fluid-Geomechanics Model (TD-RFG Model) was developed to evaluate the time-dependent rock structure dynamics. The interactions across the elastic deformation field, the transient fluid transport field and the discontinuous damage field are analyzed and modeled using TD-RFG. The established TD-RFG platform provides a pathway for multi-field and time-dependent rock structure stability assessment. A case study of shaly roof stability in an Illinois Basin coal mine and an analysis of it are presented. In the analysis we investigate the time- and location-dependent propagation of rock fractures that create connected channels that allow for rapid water penetration. The analysis indicates that, because of damage-induced increases in permeabilities, moisture transport is facilitated and so seasonal relative humidity variations at the mine opening are quickly reflected at interior locations in the shale roof, coal pillars and ground floor. The results of the modeling can ultimately provide the approach and data for quantifying and evaluating the water retention behavior and suction potential in an unsaturated air-water-shale/coal system and define strategies for ground control.

Estimation of the Influence of Compressed Hydrogen on the Mechanical Properties of Pipeline Steels

Consideration of the possibility of transporting compressed hydrogen through existing gas pipelines leads to the need to study the regularities of the effect of hydrogen on the mechanical properties of steels in relation to the conditions of their operation in pipelines (operating pressure range, stress state of the pipe metal, etc.). This article provides an overview of the types of influence of hydrogen on the mechanical properties of steels, including those used for the manufacture of pipelines. The effect of elastic and plastic deformations on the intensity of hydrogen saturation of steels and changes in their strength and plastic deformations is analyzed. An assessment of the potential losses of transported hydrogen through the pipeline wall as a result of diffusion has been made. The main issues that need to be solved for the development of a scientifically grounded conclusion on the possibility of using existing gas pipelines for the transportation of compressed hydrogen are outlined.

Design of bidirectional frictional behaviour for tactile contact using ellipsoidal asperity micro-textures

Tactile perception and friction can be modified by producing a deterministic surface topography. Change of surface feature arrangement and texture symmetry can produce an anisotropic frictional behaviour. It is generally achieved through skin hysteresis by promoting its deformation. This work investigates whether a bidirectional friction can be created with microscale ellipsoidal asperity textures, thus relying on the adhesive component of friction. For this purpose, four textured samples with various asperity dimensions were moulded with a silicone rubber having an elastic modulus comparable to that of the skin. Coefficient of friction measurements were conducted in-vivo in two sliding directions with a range of normal loads up to 4 N. Finite element method (FEM) was used to study elastic deformation effects, explain the observed friction difference, and predict surface material influence. Measurements performed perpendicular to the asperity major radii showed consistently higher friction coefficients than that during parallel sliding. For the larger asperity dimensions, a change of the sliding direction increased friction up to a factor of 2. The numerical analysis showed that this effect is mostly related to elastic asperity deflection. Bidirectional friction differences can be further controlled by asperity dimensions, spacing, and material properties.

Buoyancy driven second grade nano boundary layers over a catalytic surface with reaction rate, heat of reaction and activation energy at boundary

The present article aims to explore the characteristics of catalytic surface reactions on free convection non-Newtonian nanofluid boundary layers which are driven by buoyancy force. The non-Newtonian behavior of the fluid is modeled using a Cauchy stress tensor which includes pressure, dynamic viscosity, two normal stress moduli and two Rivlin-Ericksen tensors. The Buongiorno model is utilized to model the nanofluid behavior. The exothermic surface reactions are considered by Arrhenius kinetics at the wall. The boundary conditions are designed with one-step, non-isothermal and first order reactions. Furthermore, the flow phenomenon is assumed with elastic deformation effects. To carry out a parametric study, the governing equations and boundary conditions were transformed into a non-dimensional form with essential parameters. The impacts of exothermic reactions in the flow region are explored using heat of reaction, reaction rate and activation energy parameters which occurred in the boundary. The flow behaviors are clearly analyzed with a numerical experiment. The results are plotted for momentum, thermal and concentration boundary layers, skin friction, dimensionless wall temperature and dimensionless wall concentration. The numerical values of dimensionless wall temperature and wall concentration are presented. It is found that the heat of reaction raises the temperature and concentration profiles significantly due to the catalytic surface reactions and it shows a slight enhancement in the velocity profile. Both activation energy and reaction rate constant retard all the nanofluid profiles and have a significant role on the temperature and concentration profiles. The surface reaction and the buoyancy parameters show a significant variation inside the boundary layer flow region of second grade nanofluid.

Nonlinear vibration of the spiral bevel gear under periodic torque considering multiple elastic deformation evaluations due to different bearing supports

This paper investigates two parameters effect on vibrational responses of the spiral bevel gear. Changing the gear system overall stiffness (GSOS) considering elastic deformation and periodic torques are the two parameters which are represented as the main goals of this study. In order to investigate the effects of shaft stiffness and elastic deformation, two different cases with different support locations are considered. The first case is presented by locating the support close to the gear, and in the latter one, the distance between gear and support is increased. Besides, to study the effect of torque, two main types are considered: constant and periodic excitation torque. To illustrate the dynamic behavior, the governing differential equations are solved numerically according to the Runge–Kutta method. The equations are nonlinear due to backlash and time-varying coefficients as the results of GSOS variation. Vibrational phenomena are illustrated by means of bifurcation diagrams, RMS, and Poincaré maps. Particular vibrational behaviors such as “chaos” and “period-doubling” phenomena are illustrated with details. By investigating the effect of shaft stiffness, results show that when the support is far away from gear, the vibration response increased by 67.5%. Moreover, while the input torque is constant, the support movement does not cause undesirable responses such as chaotic or period-doubling responses. The periodic torque causes undesirable responses such as chaos and bifurcation and period-doubling responses.Article HighlightsWhat is done in the present paper can be mentioned in three main parts:The nonlinear dynamics of the spiral bevel gear pair under two different support situations is investigated in this paper.To scrutinize the dynamic behavior of the spiral bevel gear-pair in a nearly real situation, the input driver torque is periodically variable.The results show that the spiral bevel gear pair may comprise chaotic response with periodic torque excitation if the bearing supports locate far enough from the gears.

Study on passive compliance control in robotic belt grinding of nickel-based superalloy blade

To overcome the effect of fluctuation of normal grinding force on belt precision grinding of nickel-based superalloy blade with the robot, a novel passive compliance control method is proposed in this work. A passive compliance grinding device was designed to reduce the fluctuation of robotic normal grinding force, and the mechanical modeling and analysis of this device were performed. In consideration of the effect of elastic deformation of contact wheel, inherent accuracy error of robot, non-uniform allowance distribution and weak rigidity of blade, the control model of the robotic normal grinding force was established to maintain its stability. The experimental results revealed that the presented control method was beneficial to stabilize the normal grinding force in robotic grinding of nickel-based superalloy blade, and control accuracy of normal grinding force with this proposed method increased by 64.81% than that without the control method. This control method significantly improved the surface profile accuracy of nickel-based superalloy turbine blade to 0.10309 mm. Furthermore, the mathematical model of residual height based on the proposed control method was obtained to explain the relationship between residual height and machined surface roughness of concave surface and convex surface.