Transverse Roughness Research Articles

Experimental research on performance of monolayer brazed diamond wheel through a new precise dressing method—plate wheel dressing

The application of monolayer brazed diamond wheels in machining hard–brittle materials is always limited for the high transverse roughness on the ground surface of the workpiece. In the present investigation, a new dressing method, namely plate wheel dressing, was proposed for monolayer brazed diamond wheels in order to reduce the surface roughness of workpiece by micro-removing the over-protruded grits. To evaluate the effect of the dressing method, the grinding performance of the dressed diamond wheel was investigated in grinding SiC ceramics. Results obtained show that the contour of the grits was improved greatly and the quality of the workpiece was pretty good to meet the requirement of precision grinding. The transverse surface roughness Ra value reduced to the minimum value, i.e., 0.086 μm. This plate wheel dressing method can realize the precise dressing of the monolayer brazed diamond wheel.

A STUDY OF THIN FILM LUBRICATION AT NANOSCALE FOR A FERROFLUID BASED INFINITELY LONG ROUGH POROUS SLIDER BEARING

The study aims at analyzing the performance of a ferrofluid-based infinitely long rough porous slider bearing which makes use of thin film lubrication at nanoscale. The stochastic model of Christensen and Tonder has been employed to analyze the effect of surface roughness while the Neuringer-Rosensweig’s model has been adopted to study the magnetization effect. The pressure distribution in the bearing system has been obtained by solving the associated stochastically averaged Reynolds type equation. The results indicate that although the transverse roughness is supposed to affect the bearing system adversely, the situation remains fairly better in the case of thin film lubrication at nanoscale. In fact, the consideration of thin film lubrication at nanoscale results in an all round improved performance, even for lower strength of the magnetic intensity. However, the couple stress adds a little more to this positive effect.

Combined Effect of Slip Velocity and Roughness on the Jenkins Model Based Ferrofluid Lubrication of a Curved Rough Annular Squeeze Film

This paper theoretically analyzes the combined effect of slip velocity and surface roughness on the performance of Jenkins model based ferrofluid squeeze film in curved annular plates. The effect of slip velocity has been studied resorting to the slip model of Beavers and Joseph. The stochastically averaging method of Christensen and Tonders has been deployed for studying the effect of surface roughness. The pressure distribution is derived by solving the associated stochastically averaged Reynolds type equation with suitable boundary conditions, leading to the computation of load carrying capacity. The graphical representations reveal that the transverse surface roughness adversely affects the bearing performance. However, Jenkins model based ferrofluid lubrication offers some scopes in minimizing this adverse effect when the slip parameter is kept at minimum. Of course, an appropriate choice of curvature parameters adds to this positive effect in the case of negatively skewed roughness. Moreover, it is established that this type of bearing system supports certain amount of load; even when there is no flow which does not happen in the case of conventional lubricant based bearing system.

Chaotic Response and Bifurcation Analysis of Rotor-Bearing System with Nonlinear Suspension and Roughness Effect under Turbulent Flow

This research aims to study a numerical analysis to investigate the dynamic orbits of a rotor supported by two turbulent journal bearings considering longitudinal and transverse roughness effect under nonlinear suspension. The dynamic response of the rotor center and bearing center are studied. The dynamic trajectories of the rotor center and bearing center, Poincare maps, bifurcation diagrams and the maximum Lyapunov exponent method are employed to analyze dynamic responses in this study. The results show that either the longitudinal and transverse or the values of roughness parameters c1 would not affect strongly nonlinear rotor-bearing system very much but the difference of dynamic response between considering with roughness effect and without roughness effect are very obvious. The modeling results provide some theoretical references for further researching of rotor-bearing system for rotating machinery that operate in highly rotational speed, especially it considers roughness effect, turbulent flow and nonlinear suspension of bearing system.

Performance of a Ferrofluid Based Rough Parallel Plate Slider Bearing: A Comparison of Three Magnetic Fluid Flow Models

Efforts have been made to present a comparison of all the three magnetic fluid flow models (Neuringer-Rosensweig model, Shliomis model, and Jenkins model) so far as the performance of a magnetic fluid based parallel plate rough slider bearing is concerned. The stochastic model of Christensen and Tonder is adopted for the evaluation of effect of transverse surface roughness. The stochastically averaged Reynolds-type equation is solved with suitable boundary conditions to obtain the pressure distribution resulting in the calculation of load carrying capacity. The graphical results establish that for a bearing’s long life period the Shliomis model may be employed for higher loads. However, for lower to moderate loads, the Neuringer-Rosensweig model may be deployed.

Performance of 180° partial hole-entry hybrid journal bearing considering the combined influence of surface roughness and non-Newtonian behaviour of lubricant

The present paper is aimed to analyse the static and dynamic performance of a capillary compensated 180° partial non-recessed (hole-entry) hybrid journal bearing system considering the combined influence of surface roughness and nonlinear behaviour of the lubricant. The relation between shear stress and shear strain rate of non-Newtonian lubricant has been modelled by using the power law model. To analyse, the performance of hybrid journal bearing, the governing Reynolds equation has been solved by using the finite element method. The numerically simulated result indicates the effect of surface orientation parameters (γ), power law index (n) and surface roughness parameter (Λ) on the performance characteristics. The present results indicate that, the transverse roughness pattern (γ = 1 / 6) gives better stability of bearing as compared to other roughness patterns. Therefore, a proper selection of roughness parameters (γ and Λ) and power law index (n) is essential to obtain optimum performance of bearing.

Studying the properties of heat cure acrylic resin after reinforced with polyamide fibers treated with plasma (oxygen gas)

Background: In prosthodontic dentistry, Heat cure acrylic resin is the most popular denture base material. This material still requires different methods of reinforcement .One of which can be the addition of different kind of fibers. This study aimed to investigate the effects of different concentrations of plasma treated polyamide fibers on some properties of heat cure acrylic resin. Materials and methods: All specimens were prepared from heat cure acrylic resin. plasma treated polyamide fibers were added in different concentration as follow (0% no fibers control, 2%, 5% &7%).These fibers were treated with a plasma oxygen gas for two times 5min and 10 min .The properties of these specimens were evaluated through the following test: Transverse strength, Impact strength, Indentation hardness and surface roughness. Statistical analysis of data was done using ANOVA test. Results: In heat cure acrylic specimens reinforced with plasma treated polyamide fiber for 10 min , the highest mean values of Transverse strength and Impact strength (78.5+3.100)Mpa,( 7.821+0.763)KJ/m2 respectively. These results observed in specimens contain (5%) of fiber. Also, the effect of polyamide fiber treated with oxygen gas for 5 min increases transverse strength and impact strength. ANOVA test results revealed a non-significance difference among groups of specimens for indentation test only. Conclusions: Within the limitation of this study ,it can be concluded that 2%&5% of plasma treated polyamide fiber results in improvement in transverse strength, impact strength and surface roughness. While for Indentation hardness test, a statistically non significance difference was observed among all groups of specimens.

Comparison of Some Mechanical Properties of Silanated SiO2 and Polyester Fiber Composite Incorporation into Heat Cured Acrylic Resin.

Background: improving polymethylemethacrylate (PMMA) resin properties is the challenge nowadays, this can be done by adding several forms and types of nano- and micro-particles to the powder or to the monomer , the aims of the study is to investigate some mechanical properties of the acrylic resin after the addition of SiO2 nano-particles in combination with polyester fibers. Materials and Methods: The research includes 160 samples divided into four groups, four tests investigated in the study: Transverse flexural strength, impact strength, surface hardness and surface roughness (n=10). Group I is the control (No addition), group II with the addition of SiO2 5% by wt. nano-particles, group III in which polyester fibers 3% by wt., 6 mm length added and group IV contains a combination of SiO2 5% by wt. nano-particles and polyester fibers 3% by wt., 6 mm length. The data analyzed by ANOVA Table and multiple comparison post hoc Tukey’s tests. Results: Show that a mark increase in the impact and flexural strength when combination of 5% by wt. silanated SiO2 and 3% by wt. and 6 mm length polyester fiber incorporated into PMMA resin; while flexural strength and surface hardness tests show that there was no significant differences among the groups after ANOVA Table inferential statistical analysis application. Surface roughness comparison among the groups revealed that group containing silanated SiO2 only gives the highest rough surface while group containing polyester fiber only shows the lowest value of roughness. Conclusion: Within the limitation of this study, incorporation of silanated SiO2 and polyester fiber combinations in a significant weight and fiber length lead to enhancement in the impact and flexural strength of PMMA resins and with no or little effect on the surface hardness and roughness properties.

Effect of tool geometry on surface roughness in slotting of CFRP

This paper presents a study of transverse and longitudinal arithmetic average roughness of carbon fiber-reinforced plastic (CFRP) material slotted with three micrograin carbide knurled tools: fine, medium, and coarse toothings. By transverse (respectively longitudinal) arithmetic average roughness, we mean roughness measured perpendicular to the advance direction (respectively in the advance direction). The purpose of this work is to implant a theoretical model of transverse arithmetic average roughness highlighting his dependence on only tool geometry, to validate it experimentally and to define an empirical model of longitudinal arithmetic average roughness for each knurled tool. From the results of ANOVA, it is concluded that feed per tooth makes the highest statistical and physical influence on surface roughness. Experiments show that knurled tool fine toothing is the suitable tool for slotting of CFRP because it produces less damage to the laminate plate.

Laminar Flow Through a Circular Tube Having Transverse Ribs and Twisted Tapes

The experimental friction factor and Nusselt number data for laminar flow of viscous oil through a circular duct having integral transverse rib roughness and fitted with twisted tapes with oblique teeth have been presented. Predictive friction factor and Nusselt number correlations have also been presented. The thermohydraulic performance has been evaluated. The major findings of this experimental investigation are that the twisted tapes with oblique teeth in combination with integral transverse rib roughness perform significantly better than the individual enhancement technique acting alone for laminar flow through a circular duct up to a certain value of fin parameter.

An Evaluation of Some Mechanical Properties of Autopolymerizing Acrylic Resin with the Modified One after Changing the Curing Environment: (In vitro Study)

Background: Studying and investigating the transverse strength(Ts), impact strength(Is), hardness (Hr) and surface roughness(Ra) of conventional and modified autopolymerizing acrylic resin with different weight percentages of biopolymer kraftlignin, after curing in different water temperatures; 40°C and 80°C. Material and Methods: Standard acrylic specimens were fabricated according to ADA specification No.12 for transverse strength, ISO 179 was used for impact testing, Shore D for hardness and profilometerfor surface roughness. The material lignin first dispersed in the monomer, then the powder PMMA is immediately added. Ligninadded in different weight percentages. Then cured using pressure pot (Ivomet) in two temperatures;40°C and 80°C under 2 bar pressure, for 30 minutes.Atotal of 144samples were prepared for this study. Ts, Is, Ra, and Hr were tested, by using Instron universal testing machine, charpy impact tester, shore D tester, and profilometer respectively. Results: The transverse strength increased in both the conventional and modified onewhen compared with that cured in air. The addition of 0.5wt% lignin gave the higher effect (78.0017MPa) with highly significant difference found between groups at 40°C polymerizing temperature. While the impact strength in both temperatures in the modified resin revealed increased results than conventional one, 1.25wt% of kraft lignin gave the highest value (12.7355KJ/m2) with highly significant differences found between groups at 80°C polymerizing temperature. Hardness and surface roughness showed also highly significant differences found between groups at 40°C polymerizing temperature, all the groups had increased Hr. than the control one (78.95), while the Ra. decreased for 1.0% ,1.25,1.50 and 1.75 wt% lignin content to (0.26,0.10,0.063, 0.12µm) respectively in 40°C polymerizing temperature, the lowest value present in 1.75 wt% lignin (0.05 µm) at 80°Cpolymerizing temperature. Conclusions: It seems that increasing the polymerizing temperature to 40°C had a positive effect on the mechanical properties of autopolymerizing acrylic resin and the one enforced by kraft lignin biopolymer in low percentages. Increasing the polymerizing temperature to 80°C will doesn’t have much positive effect but it doesn’t deteriorate the mechanical properties. However, when submitted to increasing the temperature to 80°C, specimens showed a significant increase in impact strength.

Strength and Surface Roughness of Cross Linking Acrylic Resin Processed by Different Heat Curing Methods

Background: Heat-cured acrylic resin is considered one of the most commonly used denture base material in denture construction, but this material is not ideal in every respect. So many researches have been carried out to find an alternative material like cross linking acrylic resin. Meanwhile, the curing procedures have been modified to improve the physical and mechanical properties of resin materials .The aim of this study was to evaluate the effect of three curing methods:(water bath, autoclave short cycle and autoclave long cycle) on transverse strength, tensile strength and surface roughness of cross linking acrylic denture base materials. Material and method: Cross linking acrylic resin was used in this study and processed in three curing methods (water bath, autoclave short cycle and autoclave long cycle). Ninety specimens were prepared. Each main group was subdivided into three subgroups according to the type of test used (transvers strength test, tensile strength test and surface roughness test). Each group contained 10 specimens for each test. Result: Three tests were used to analyze the results: analysis of variance (ANOVA), the least significant difference (LSD) and an independent T-test. There were no significant differences between the results of the processing techniques regarding transverse and tensile strength but there was a significant difference between the results of surface roughness tests. Conclusion: It was concluded that autoclave curing method can be used with different duration whether it is short or long instead of water bath curing method.

CFD investigation of effect of relative roughness height on Nusselt number and friction factor in an artificially roughened solar air heater

Solar air heaters are cheap and extensively used solar energy collection devices for space heating, seasoning of timber, curing of industrial products and can also be effectively used for curing/drying of concrete/clay building components and in air-conditioning systems. In this article, the effect of relative roughness height on Nusselt number and friction factor in an artificially roughened solar air heater having circular-sectioned transverse rib roughness (duct aspect ratio, AR = 5:1) is studied by adopting CFD (computational fluid dynamics) approach. Numerical solutions are obtained using commercial CFD software ANSYS FLUENT v12.1. Computations based on the finite volume method with the SIMPLE algorithm have been conducted. Circular-sectioned transverse ribs are applied at the underside of the top of the duct, that is, on the absorber plate. The rib pitch (P) and rib height (e) are varied by keeping rib-pitch-to-rib-height ratio constant (P/e = 14.29). The rib-height-to-hydraulic-diameter ratio (e/D) studied is 0.021, 0.03, 0.042, and 0.06. For each rib-height-to-hydraulic-diameter ratio (e/D), simulations are executed at six Reynolds numbers from 3800 to 18,000 (relevant in solar air heater). The thermal enhancement factor for e/D = 0.042 is found to be the best for the investigated range of parameters and is about 1.635.

Jenkins model based ferrofluid lubrication of a curved rough annular squeeze film: Effect of slip velocity

This paper analyzes the combined effect of slip velocity and transverse roughness on the performance of a Jenkins model based ferrofluid lubrication of a squeeze film in curved rough annular plates. The slip model of Beavers and Joseph has been invoked to evaluate the effect of slip velocity. In order to find the effect of surface roughness the stochastic averaging model of Christensen and Tonder has been used. The pressure distribution is obtained by solving the concerned stochastically averaged Reynolds type equation. The load carrying capacity is calculated. The graphical representations of the results indicate that the effect of transverse surface roughness is adverse in general, however, the situation is relatively better in the case of negatively skewed roughness. Further, Jenkins model based ferrofluid lubrication offers some measures in reducing the adverse effect of roughness when slip parameter is kept at reduced level with a suitable ratio of curvature parameters. Lastly, the positive effect of magnetization gets a boost due to the combined effect of variance (-ve) and negatively skewed roughness suitably choosing the aspect ratio.

Magnetic fluid lubrication of an infinitely long slider bearing with rough surfaces

This article deals with the performance characteristics of an infinite slider bearing with rough surfaces in the presence of a magnetic fluid as the lubricant. The magnetic fluid flow model of Neuringer Rosenwicg has been used here. The stochastic model of Christensen and Tonder has been adopted to evaluate the effect of surface roughness. The related stochastically averaged Reynolds equation is solved to obtain the pressure distribution leading to the calculation of load carrying capacity. The results presented in graphical forms suggest that the adverse effect of transverse roughness can be minimized by choosing suitable magnetic strength. It is observed that the negativity-skewed roughness plays an important role in improving the bearing performance.

Effects of Surface Roughness in Squeeze Film Lubrication of Spherical Bearings

This paper describes a theoretical analysis of the effects of surface roughness in squeeze film lubrication of spherical bearings. The analysis is based on a deterministic theory of hydrodynamic lubrication. The important squeeze film parameters are obtained as simple closed form expressions for roughness types. The generalized Reynolds equation accounting for the surface roughness is considered and it is applied to study the effects of roughness in squeeze film lubrication of spherical bearings. In order to get the expression for pressure, the generalized Reynolds equation is solved. Then by making use of this expression we obtain the expression for load carrying capacity, which in turn is used to find the expression for response time. These expressions are numerically computed and the results are presented graphically. From the numerical computations of the results, it is found that, the load capacity and squeezing time increases with an increase of peripheral viscosity of the lubricant. It is observed that in case of transverse roughness pattern the load capacity and squeezing time increases where as it decreases for longitudinal roughness pattern. Also load capacity increases with an increase in squeeze velocity.

Combined Effect of Surface Roughness and Slip Velocity on Jenkins Model Based Magnetic Squeeze Film in Curved Rough Circular Plates

This paper aims to discuss the effect of slip velocity and surface roughness on the performance of Jenkins model based magnetic squeeze film in curved rough circular plates. The upper plate’s curvature parameter is governed by an exponential expression while a hyperbolic form describes the curvature of lower plates. The stochastic model of Christensen and Tonder has been adopted to study the effect of transverse surface roughness of the bearing surfaces. Beavers and Joseph’s slip model has been employed here. The associated Reynolds type equation is solved to obtain the pressure distribution culminating in the calculation of load carrying capacity. The computed results show that the Jenkins model modifies the performance of the bearing system as compared to Neuringer-Rosensweig model, but this model provides little support to the negatively skewed roughness for overcoming the adverse effect of standard deviation and slip velocity even if curvature parameters are suitably chosen. This study establishes that for any type of improvement in the performance characteristics the slip parameter is required to be reduced even if variance (−ve) occurs and suitable magnetic strength is in force.

Large eddy simulation of turbulent channel flow with transverse roughness elements on one wall

This study examines the feasibility of large eddy simulation for predicting turbulent channel flows with two-dimensional roughness elements of square, circular and triangular shapes transversely placed on the bottom wall. Results are obtained for several values of the cavity width to the roughness height ratio using various subgrid-scale turbulence models. The present large eddy simulation predictions of mean streamwise velocity, root-mean-square velocity fluctuations, and skin frictional and form drags agree reasonably well with previously published results of direct numerical simulations at a low Reynolds number. All the subgrid-scale models examined here are capable of reproducing the relevant physics associated with the effect of the rough surface on the turbulent flow, exhibiting similar performances. Moreover, the use of the turbulence models leads to an improvement in the predictions of several turbulence statistics as compared with the case when no model is considered. Large eddy simulation can be combined easily with an immersed boundary method yielding satisfactory results based on a coarser grid resolution than in direct numerical simulation and, thus, it is suitable for the investigation of turbulent channel flows with riblets of various shapes.

Effect of Surface Roughness on the Squeeze Film Lubrication of Finite Poroelastic Partial Journal Bearings with Couple Stress Fluids: A Special Reference to Hip Joint Lubrication

A simplified mathematical model has been developed for understanding the combined effects of surface roughness and couple stresses on the squeeze film behavior of poroelastic bearings in general and that of hip joints in particular. The cartilage is modeled as biphasic poroelastic matrix and synovial fluid is modeled as couple stress fluid. The modified form of averaged Reynolds equation which incorporates the randomized roughness structure as well as elastic nature of articular cartilage with couple stress fluid as lubricant is derived. For the study of rough surfaces, Christensen's stochastic theory is used to study the effect of two types of one-dimensional random roughness, namely, longitudinal roughness pattern and the transverse roughness pattern. The averaged film pressure distribution equations are solved numerically by using the conjugate gradient method. It is observed that the surface roughness effect is dominant and pattern dependent and the influence of couple stresses is to improve the joint performance.

Combined Effects of Magnetic Field and Surface Roughness on Long Journal Bearing Lubricated with Ferrofluid

This study investigated the influence of ferrofluids on the lubrication performance of long journal bearings under the combined effects of stochastic surface roughness and a magnetic field generated by an infinitely long wire. According to our results, placing an infinitely long wire magnetic field at an appropriate distance from the center of the bearing can suppress side leakage in long journal bearings, thereby extending the life of the bearings. Under a higher power-law index and induced magnetic force, the introduction of transverse roughness can enhance film pressure and load capacity, while reducing the attitude angle and modified friction coefficient. The introduction of longitudinal roughness has the opposite effect. We believe that these findings provide a valuable reference for the design of bearings in the future.