Effect Of Frictional Heating Research Articles

Heat transfer optimization of Marangoni convective flow of nanofluid over an infinite disk with Stefan blowing and slip effects using Taguchi method

This article optimizes the heat and mass transfer characteristics of Marangoni convection in a nanoliquid flowing on an infinite disk with Stefan blowing and activation energy using the Taguchi method. The combined effects of frictional heating, Joule heating, and the binary chemical reaction on Marangoni convection are also examined. The flow is compelled by surface tension resulting from the thermal and nanoparticle gradient. The thermal and nanoparticle slippages are deliberated on the surface of the disk. The similarity variables of Von Kármán are used to obtain the numerical solutions of the partial differential equations of the boundary layer. The impact of operational parameters on Nusselt number, thermal energy, Sherwood number, nanoparticles volume fraction, and velocity quantities is analyzed. The Robust Taguchi method and the L16 orthogonal array design are used to optimize the heat/mass transfer rate of the nanoliquid. The combination of the optimal levels of Prandtl number, Marangoni number, thermal slip number, and nanoparticle slip number for maximum heat/mass transport in the nanoliquid is estimated by the Taguchi method. ANOVA and multivariate regression methods are also employed to obtain the significance of key parameters. The optimal combination of the key parameters is Pr = 3, δC = 0, δT = 0 and Ma = 1.0 to achieve the maximum heat transfer rate (1.73425). Among the key parameters selected for the optimization process, the Marangoni number has the highest contribution (62.12%) to the improvement of the rate of heat transport, while the nanoparticle slip condition has the lowest contribution (1.9%).

Using 1.5 mm internal diameter columns for optimal compatibility with current liquid chromatographic systems

This article describes the use of a new prototype column hardware made with 1.5 mm internal diameter (i.d.) and demonstrates some benefits over the 1.0 mm i.d. micro-bore column. The performance of 2.1, 1.5 and 1.0 mm i.d. columns were systematically compared. With the 1.5 mm i.d. column, the loss of apparent column efficiency can be significantly reduced compared to 1.0 mm i.d. columns in both isocratic and gradient elution modes. In the end, the 1.5 mm i.d. column is almost comparable to 2.1 mm i.d. column from a peak broadening point of view. The advantages of the 1.5 mm i.d. hardware vs 2.1 mm i.d. narrow-bore columns are the lower sample and solvent consumption, and reduced frictional heating effects due to decreased operating flow rates.

Abrasive wear response of Al-Si–SiCp composite: Effect of friction heat and friction coefficient

Abstract The effects of friction heat and friction coefficient on the abrasive wear response of Al-7.5Si–SiCp composite against low-cost hypereutectic (Al-17.5Si) alloy were investigated as functions of the abrasive size and applied load in both as-cast and after heat-treatment conditions. Experiments were performed on pin-on-disc apparatus at 38 –80 μm abrasive size, 5 – 20 N applied load, 100 –400 m abrading (sliding) distances and 1 m s–1 constant sliding speed. The frictional heating of as-cast and heat-treated composite was superior compared to the matrix alloy and hypereutectic alloy, whereas the trend reversed for the friction coefficient. The frictional heating and friction coefficient of the materials increased with the abrasive size and applied load in both as-cast and after heat-treatment. The worn surface and wear debris particles were examined by using field emission scanning electron microscopy to understand the wear mechanism.

Impact of Die Radius in a Streamlined Die during Wire Drawing

The effects of die radius in a streamlined die on design factors, such as the distribution of strain, stress, temperature, damage, and drawing force of a wire, were investigated during wire drawing for a better understanding of streamlined die and improvement in drawing quality of the wire. A numerical simulation was performed with the die radius of the streamlined die. The behavior of the design factors of the drawn wire fabricated by the streamlined die was different from that of the conventional die and was highly dependent on the die radius. The different behaviors of the design factors with the die radius can be explained by the frictional work and redundant work of the wire with die angle. The temperature rise and drawing force were high at a greater die radius because of the great frictional stress and heating effect stemming from the high contact length of the wire and die. Meanwhile, the higher redundant work at the surface area with decreasing die radius led to higher strain inhomogeneity, effective stress, damage value, temperature rise, and drawing force due to the abrupt change in the metal flow of the wire stemming from the high die angle. After the optimization of several design factors with die radius, it was concluded that the optimum IDR values ranged from 0.14 to 0.18, indicating that a streamlined die with a radius of 70 to 90 mm was the most suitable in the present process condition. In particular, the damage value of the wire was reduced in this range of die radii compared to the conventional die.

Effect of Fracture on ESR Intensity Using a Low-Velocity Rotary Shear Apparatus

Abstract We sheared simulated-quartz gouges using a low-velocity rotary shear apparatus and evaluated the relationship between electron spin resonance (ESR) intensity and displacement quantitatively considering problems of contaminants. ESR intensity of E1’ centre increased while OHC and peroxy centre kept constant with the increasing displacement up to 1.4 m. Microstructural analysis showed grain size reduction and fracture of starting gouges; hence, the fracture can affect the change in ESR intensity. ESR measurements were also conducted for starting gouges with variable amounts of contaminants, and it was confirmed that the effect of contaminants on the change in ESR intensity was negligible. Moreover, we estimated the temperature rise by the frictional heating on the surface and between particles, and it was shown that the effect of frictional heating on ESR intensity was also negligible in our experimental condition. Therefore, we could clarify the relationship between ESR intensity and fracturing with various displacements separately from contaminants and frictional heating. The results imply that the zero-setting of ESR signals cannot occur by the fracture with low frictional heating at the shallow depth.

Thermal damage and fatigue estimation in heavily loaded lubricated rolling/sliding contacts with Micro-Geometry

A previously developed model for heavily loaded Elastohydrodynamically lubricated (EHL) contacts with surface micro-geometry for the calculation of surface distress (micropitting), based on high-cycle fatigue and mild wear competition, is herewith further extended. It now includes the effects of frictional heating with a sharp temperature rise developed in the rolling contact. For this, a new surface damage model, originated in creep modelling, is included. With this modification, the detrimental effect of high temperature developed in the rolling/sliding contact can now be accounted for. This model can consider sharp or moderate surface temperature rise during over-rolling is found in bearings and gears operating at high speeds or under the combination of speeds, loads and unfavourable environmental aspects. The present model introduces a threshold limit made of the combination of temperature and (heating time under stress) load cycles above which the conditions in the rolling contact are deemed damaging for the steel microstructure and the tribological functionality of the rolling contact. The surface damage model is first compared with laboratory experiments in rolling/sliding conditions and then applied to study combinations of loads, sliding speeds and the effect in rolling bearings. The ability of the present model to include damaging mechanisms, other than classical metal fatigue, increases the flexibility in contact surface damage modelling and allows for the accounting of phenomena up to now excluded from better estimation of the machine elements surface life.

WITHDRAWN: MHD boundary layer flow of a Casson nano liquid over a penetrable linearly stretching sheet with frictional heating effects in Brinkmann-Forcheiemerr porous medium

Abstract This exploration comprises the predicament of 2D Casson nano liquid motion, neighbouring to boundary stratum, through Brinkmann-Forcheiemerr porous medium above a rectilinear stretching sheet. A specific computational explanation to boundary value problem concerning to nonlinear PDE’s recounting liquid motion, thermic transfer and mass convey, are derived by RK-Fehlberg method. The impact of an array of several parametric quantities on liquid motion, thermic transfer, and mass convey are probed. The impost reconnoitres the disparity of diverse liquid motion, thermic and mass, parametric quantities, induces notable thought on the compartment, of liquid, hotness and mass conveys variables are reconnoitred by way of plots.

Two-scale thermomechanical damage model for dynamic shear failure in brittle solids

A coupled thermomechanical damage approach for dynamic shear failure in brittle solids is proposed in the present contribution. The model is constructed by asymptotic homogenization from microstructures with dynamically evolving microcracks, in mode II, with unilateral contact and friction conditions on their lips. Crack-tip and frictional heating effects assumed at the small scale give rise to distributed heat sources in the macroscopic temperature equation and specific dissipation terms in the upscaled damage law. The analysis of the effective thermomechanical response of the model reveals strain rate and size effects and the influence of friction and growth of microcracks on the macroscopic thermal evolutions.

A model for rolling bearing life with surface and subsurface survival: Surface thermal effects

A previously developed model for bearing life calculation, based on high-cycle fatigue, including the separation of the surface and the subsurface survival of the rolling contact, is herewith further extended. It now includes the effects of frictional heating with a sharp temperature rise developed in the rolling contact. For this, a new surface damage integral, based on the creep mechanism, is included in the model. With this modification, the detrimental effect of high temperature developed in the rolling contact can now be accounted for. Sharp surface temperature rise during over-rolling are found in bearings operating at high speeds or under the combination of speeds, loads and unfavourable environmental temperatures. The present model introduces a threshold limit value of temperature above which the temperature in the rolling contact is deemed damaging for the steel microstructure and the tribological functionality of the rolling contact. The surface creep-damage model is first calibrated with endurance tests of bearings and then applied to study combinations of loads and speeds and the effect of the steel thermal conductivity on the life expectancy of the bearing. The ability of the present model to include damaging mechanisms, other than classical metal fatigue, increases the flexibility in bearing life predictions and allows to account for phenomena hitherto excluded from the estimation of the bearing fatigue life.

A Comparative Study of Friction Self-Piercing Riveting and Self-Piercing Riveting of Aluminum Alloy AA5182-O

In this paper, self-piercing riveting (SPR) and friction self-piercing riveting (F-SPR) processes were employed to join aluminum alloy AA5182-O sheets. Parallel studies were carried out to compare the two processes in terms of joint macrogeometry, tooling force, microhardness, quasi-static mechanical performance, and fatigue behavior. The results indicate that the F-SPR process formed both rivet–sheet interlocking and sheet–sheet solid-state bonding, whereas the SPR process only contained rivet–sheet interlocking. For the same rivet flaring, the F-SPR process required 63% less tooling force than the SPR process because of the softening effect of frictional heat and the lower rivet hardness of F-SPR. The decrease in the switch depth of the F-SPR resulted in more hardening of the aluminum alloy surrounding the rivet. The higher hardness of aluminum and formation of solid-state bonding enhanced the F-SPR joint stiffness under lap-shear loading, which contributed to the higher quasi-static lap-shear strength and longer fatigue life compared to those of the SPR joints.

Investigation of mass transfer properties and kinetic performance of high-efficiency columns packed with C18 sub-2μm fully and superficially porous particles.

Three columns packed with 2.0μm superficially porous particles, 1.7μm fully porous particles, and monodisperse 1.9μm fully porous particles with narrow particle size distribution have been deeply characterized from a kinetic point of view. The 1.9μm column showed excellent kinetic performance, comparable to that of the superficially porous one. These two columns also exhibit flatter c-branches of the van Deemter curve compared to the 1.7μm fully porous particles column, resulting in smaller loss of efficiency when they are operated at higher flow rates than the optimal ones. The independent evaluation of each contribution to band broadening has revealed that the difference in kinetic performance comes from the very small eddy dispersion contribution on the 1.9μm column, surprisingly even lower than that of the superficially porous one. This finding suggests a very good packing of the monodisperse 1.9μm column. On the other hand, the potential of 1.7μm fully porous particles is completely broken down by the strong frictional heating effect already arising at relatively low flow rates.

Effects of friction heating on a half space involving ellipsoidal inclusions with non-uniform eigentemperature gradients

Performance of material containing inhomogeneities/inclusions is severely affected by frictional heat resulting from contact behaviors between two mechanical components. An effective method for dealing with thermal field of a half space with distributed non-uniform ellipsoidal inclusions subjected to frictional heating load was proposed in the current investigation, which can be simplified to handle problems of uniform ellipsoidal inclusion and extended to deal with inhomogeneity problems. Two categories of non-uniform inclusions with Gaussian and exponential eigentemperature gradients are modeled. Temperature rise and thermal stress are analogously solved via the equivalent inclusion method (EIM). Results obtained by the proposed method totally correspond to those of the benchmarks. Parametric studies on eigentermperature gradient distribution and thermal field of a half space involving a non-uniform spherical inclusion are carried out. Surface convection effect is further taken into consideration to extend the application scope of the proposed method, and the influence of surface heat-transfer coefficients on the thermal field of a semi-infinite medium is explored.

Temperature distribution and residual stress in Friction Stir Welding process

Friction Stir Welding is an advanced solid state joining process invented as an alternative to join materials which are unfavourable to join using fusion welding technique. In Friction Stir Welding, the non-consumable tool is rotated and is slowly dived into the centreline and simultaneously progressed along that line. The heat generation in the process is a combined effect of frictional heating and heat because of the plasticization of the material. In this paper, the Finite Element package COMSOL Multiphysics 5.2a is used to develop a three dimensional numerical model to generate thermal profiles during welding, which is validated through experimentation. Due to the differential heating and cooling and the plasticization of the material, residual stresses develop in the material. The nature of the residual stresses significantly affects the quality of the joints. To analyse the residual stresses developed, three different approaches; namely experimental, analytical and numerical methods are used. Experimentally, residual stress is obtained by X-Ray Diffraction technique, Masubuchi and Martin’s longitudinal stress equation is used for analytical measurements and also residual stress is obtained numerically. The three approaches used for measurement of residual stresses are in well agreement with each other.

Entropy Generation in Cu-Al2O3-H2O Hybrid Nanofluid Flow over a Curved Surface with Thermal Dissipation

Heat transfer and entropy generation in a hybrid nanoliquid flow caused by an elastic curved surface is investigated in the present article. To examine the effects of frictional heating on entropy generation, the energy dissipation function is included in the energy equation. The Tiwari and Dass model for nanofluid is used by taking water as a base fluid. A new class of nanofluid (hybrid nanofluid) with two kinds of nanoparticles, Copper (Cu) and Aluminum oxide (Al2O3), is considered. Curvilinear coordinates are used in the mathematical formulation due to the curved nature of the solid boundary. By utilizing similarity transformations, the modelled partial differential equations are converted into ordinary differential equations. Shooting and the Runge-Kutta-Fehlberg method (FRKM) have been used to solve the transformed set of non-linear differential equations. The expression for entropy generation is derived in curvilinear coordinates and computed by using the numerical results obtained from dimensionless momentum and energy equations. Comparisons of our numerical results and those published in the previous literature demonstrate excellent agreements, validating our numerical simulation. In addition, we have also conducted parametric studies and find that entropy generation and temperature suppress with increasing values of dimensionless radius of curvature. Furthermore, it is found that less entropy is generated in regular nanofluid as compare to hybrid nanofluid. To examine the influences of a set of embedding physical parameters on quantities of interest, different graphs are plotted and discussed.

Second law analysis of Blasius flow with nonlinear Rosseland thermal radiation in the presence of viscous dissipation

In the present article, we perform the second law analysis of classical Blasius flow accounting the effects of nonlinear radiation and frictional heating. The two-dimensional boundary layer momentum and energy equations are converted to self-similar equations using similarity transformations. The set of resultant ordinary differential equations are solved numerically. The numerical results obtained from solutions of dimensionless momentum and energy equations are used to calculate the entropy generation number and Bejan number. The velocity profile f'(ξ), temperature distribution θ(ξ), entropy production number Ns and Bejan number Be are plotted against the physical flow parameters and are discussed in detail. Further, for the sake of validation of our numerical code, the obtained results are reproduced using Matlab built-in boundary value solver bvp4c resulting in an excellent agreement. It is observed that entropy generation is increasing function of heating parameter, Prandtl number, Eckert number and radiation parameter. Further, it is observed that entropy generation can be minimized by reducing the operating temperature ΔT=Tw−T∞.

Rubber friction and the effect of shape

Abstract Contrary to the classic laws of friction, rubber friction is not independent of shape. The friction of three shapes of the same rubber compound sliding over a dry-rough surface was measured. The three shapes had the same nominal contact area but different sliding direction-lengths and widths. Frictional differences were found between all three shapes at sliding speeds of 10 mm/s and 0.5 mm/s. The effect of frictional heating and other friction mechanisms that cause these differences are evaluated and discussed.

Friction spot riveting of AA6061-T6 and polypropylene

A novel joining method called friction spot riveting (FSR) was proposed to improve mechanical properties between AA6061-T6 and polypropylene (PP) joints via improving mechanical interlocking. Under the synergistic effect of frictional heat and forging force, the plastic was heated and softened, which further flowed into the pre-fabricated holes in the metal. Sound metal/plastic joints were obtained via a rivet composed of PP plastics, while an intimate joining interface formed between AA6061-T6 and PP. The joining mechanism contained the mechanical interlocking induced by the rivet and the adhesion bonding. The tensile shear load was significant improved and the maximum value was 266 N. The tensile shear fracture were characterized by the fracture of the rivet and the failure of adhesive joining.

Sensible Heat Fluxes in the Nearly Neutral Boundary Layer: The Impact of Frictional Heating within the Surface Layer

Abstract The effect of frictional dissipative heating on the calculation of surface fluxes in the atmospheric boundary layer using bulk flux formulas is considered. Although the importance of frictional dissipation in intense storms has been widely recognized, it is suggested here that its impact is also to be seen at more moderate wind speeds in apparently enhanced heat transfer coefficients and countergradient fluxes in nearly neutral conditions. A simple modification to the bulk flux formula can be made to account for its impact within the surface layer. This modification is consistent with an interpretation of the surface layer as one across which the flux of total energy is constant. The effect of this modification on tropical cyclones is assessed in an idealized model, where it is shown to reduce the predicted maximum wind speed by about 4%. In numerical simulations of three individual storms, the impacts are more subtle but indicate a reduction of the sensible heat flux into the storm and a cooling of the surface layer.

The Development and Application of a Scuffing Test Based on Contra-rotation

Scuffing is a surface failure mode that occurs in sliding–rolling contacts subjected to high loads and high sliding speeds, such as those in gears and cam-followers. Owing to its sudden onset, rapid progression and dependence on both fluid and boundary lubricant films, scuffing is difficult to study in a repeatable manner. This paper describes further development of a recently proposed scuffing test method based on contra-rotation, its extension to higher loads using a new experimental set-up and its application to study the onset of scuffing with a selection of model and fully-formulated oils. The method employs two surfaces moving in opposite directions under rolling–sliding conditions, with a fixed load and step-wise increasing sliding speed. By decoupling the entrainment and sliding speeds, the method allows the effects of lubricant formulation on scuffing performance to be isolated from the influence of viscosity. The approach achieves high sliding speeds in parallel with low entrainment speeds, while minimising the undesirable effects of surface wear and frictional heating. The proposed test is relatively fast and economical, with total test time of about 30 min including specimen cleaning and set-up. Results show that the newly implemented modifications have improved the repeatability of the test method, so that the number of repeat tests required for reliable oil ranking results is minimal. Tests with model and fully-formulated oils show that the onset of scuffing is characterised by a sharp and unrecoverable increase in friction and accompanied by the destruction of any boundary films. All tests show that the relationship load × speedn = constant holds at scuffing, with the exact value of the exponent n being dependent on the oil formulation. Additivised oils were shown to have enhanced scuffing resistance, which arises from their ability to postpone the uncontrollable rise in friction to higher sliding speeds. Finally, the critical maximum contact temperature scuffing criterion was shown to predict the onset of scuffing in our tests better than the frictional power intensity criterion.

Experimental Investigations on Microstructural and Mechanical Behavior of Friction Stir Welded Aluminum Matrix Composite

The welding of materials by applying Friction Stir Welding technique is a new solid-state joining technique. The main advantage of this method compared to the traditional joining process is that it minimizes problem-related to metal resolidification as the method incorporates no melting phase. In this experimental work, the effect of friction stir welding (FSW) technique on the microstructure and mechanical properties of the cast composite matrix AA6063 reinforced with 7wt % SiC particles is studied. Friction stir welding, owing to the simultaneous effect of intense plastic deformation and frictional heat generated throughout welding, had impacts each on the reinforcement agents and the matrix alloy. FSW produced a notable reduction in the size of reinforcement agents and their homogeneous distribution in the weld region. It also induced the grain refinement due to dynamic recrystallization of the aluminum matrix alloy in the weld area. The frictional heat generated during friction stir welding had impacts on the growth, dissolution and reprecipitation of the hardening precipitates. The microstructural changes resulted in improved mechanical properties such as UTS, elongation, and hardness of the joint. A joint efficiency of 98.84% was observed for the welded joint. The XRD and EDX analysis of the welded area confirmed that there was no formation of any other compound due to the frictional heat produced during welding. The SEM fracture morphology of the welded joint revealed that the fracture behavior was changed from ductile to brittle following to FSW.