Dimple Textures Research Articles

Experimental and Computational Analysis of Aluminum-Coated Dimple and Plain Tubes in Solar Water Heater System

Solar power is often regarded as one of the most promising forms of alternative energy since it is both sustainable and renewable. It is difficult to utilize and benefit from solar energy in residential and industrial applications because of the intermittent nature of its supply. A solar-based water heating system is efficient for using solar thermal conversion, the simplest and most successful method of turning solar energy into thermal energy. In this research, the performance analysis of Parabolic Trough Solar Collectors (PTSCs) with aluminum-coated copper dimple tubes was computationally and experimentally analyzed. For computational analysis, a Computational Fluid Dynamics (CFD) tool was used. For experimental analysis, aluminum-coated dimple tubes were used to pass the base fluid (water) in it while varying the mass flow rate from 1.0 to 3.0 kg/min at steps of 0.5 kg/min to examine the effect of dimple texturing and aluminum coating on the performance of the solar water heater. The parameters, such as thermal efficiency, friction factor, convective heat transfer coefficient, Nusselt number, and effectiveness of the PTSC, were analyzed, and we found remarkable improvement towards high conversion efficiency. At a flow rate of 2.5 kg/min, the thermal efficiency was improved by about 36%, the friction factor increased by about 0.32%, the convective heat transfer coefficient was improved by 1150 W/m2K, Nusselt number was improved by about 53.8 and the effectiveness was enhanced by 0.4. The simulation results were compared with the experimental results, and the deviation was about ±3.8%, which may be due to an error in the instrument as well as environmental conditions during the analysis. The outcome of results can be used for real-life applications in industrial water heating and domestic water heating especially, the places exposed to low solar radiation intensity throughout the year.

Stray-corrosion-free ECM with electrolyte absorbed in a porous solid ball for dimple texturing on finished workpiece surfaces

Dimple textures are widely used on the finished workpiece surface. For example, shallow grooves with a depth of micrometers are typically used as oil pockets on sliding surfaces, and dimple textures are also used on metal workpiece surfaces to mark product logos or product numbers. Electrochemical machining (ECM) is commonly used because it does not produce heat-affected layers, residual stress, or microcrack. However, stray-corrosion of ECM decreases the surface quality of the finished workpiece and is challenging to solve. In this study, to process dimple textures on a finished workpiece surface, a new ECM method was employed, with a porous solid ball serving as the electrolyte absorption material. During processing, the electrolyte distribution is limited by the porous solid as no electrolysis occurs in the unintended processed area. Hence, it leads to a stray-corrosion-free process. Before processing, the proposed ECM method was analyzed with a simulation to investigate the electric potential, current density distribution, and processed result. Finally, combined with the control of the power supply switching and the relative movement between the tool electrode and workpiece, shallow dimples with different depths, lengths, and patterns were obtained.

Tribological Investigation of Textured Surfaces in Starved Lubrication Conditions

The present work investigates the friction reduction capability of two types of micro-textures (grooves and dimples) created on steel surfaces using a vertical milling machine. The wear studies were conducted using a pin-on-disc tribometer, with the results indicating a better friction reduction capacity in the case of the dimple texture as compared to the grooved texture. The microscopic images of the pin surface revealed deep furrows and significant damage on the pin surfaces of the groove-textured disc. An optimization of the textured surfaces was performed using an artificial neural network (ANN) model, predicting the influence of the surface texture as a function of the load, depth of cut and distance between the micro-textures.

Experimental research on sealing performance of liquid film seal with herringbone-grooved composite textures

Based on the mechanical seal experiments, sealing performances of the mechanical face seals with the herringbone-grooves (HG) only and with composite textures of herringbone grooves and circular dimple textures (HGC) were investigated respectively. The reserve suction effect of HG observed in the experiments provided the evidence for the main inducing mechanism of zero leakage in liquid film sealing. The cavitation region of HGC decreases with the rotating speed, and the HG has the reserve effect. The HGC has lower friction torque and larger film thickness compared to HG, indicating better friction performance. Because of the circular dimples, the temperature difference in sealing rings is reduced and the corresponding thermal performance of the mechanical seal has been improved.

Effect of Laser Surface Texturing on the Tribological Properties and Scuffing Mechanism of CKS Piston Ring Against Cast Iron Cylinder Liner Under High Intensifying

The objective of this study is to characterize and understand the evolutionary processes that the effect of surface texture has on the tribology properties of the Chrom-Keramik-Schicht (CKS) piston ring/cast iron cylinder liner system under high intensifying. Surface dimple textures with an area density of 3–9% were prepared on the CKS piston ring by YAG laser, and the antifriction and antiscuffing properties were tested on a reciprocating test rig at 200 °C and 80 MPa. The minimum friction coefficient and wear loss were both obtained at the area density of 5%, compared with the untextured cylinder liner–piston ring (CLPR). The friction coefficient decreased by 0.013 to 0.086, and the wear loss for the piston ring and cylinder liner decreased by 41% and 46%, respectively. The sharp decrease of the friction force induced by surface polishing of the cylinder liner is taken as a sign to indicate the cylinder scuffing under starved lubrication. The scuffing time for the piston ring/cylinder liner system reached a maximum value of 18 min at an area density of 3%, which is extended about 41% compared with that of the untextured piston ring. The dimple surface texture on the piston ring could extend the scuffing time by delaying the occurrence of polishing behavior on the surface of cylinder liner. It is found that the retarded surface polishing played a major role for the modification of the antiscuffing property of the friction pairs according to the friction curves and wear morphologies.

Influence of dimple textures on the tribological performances of tapered roller bearings under starved lubrication

PurposeThe purpose of this paper is to study the influence of dimple textures on the friction and wear properties of tapered roller bearings (TRBs) with many pattern parameters, e.g. diameter, depth and area density under starved lubrication.Design/methodology/approachThe pattern parameters include the dimple diameter (D; 60, 100 and 200 µm), dimple depth (H; 5, 10 and 20 µm) and area density (S; 6%, 12% and 24%). Dimples were fabricated on the outer ring (OR) of TRBs using a laser marking machine. The tribological properties of dimple-textured TRBs under starved lubrication were studied on a vertical universal friction wear tester with special friction pairs. The effect mechanisms of dimple textures on the tribological properties of TRBs are presented and summarized through experiments and discussions.FindingsWhen dimple-textured TRBs revolve under starved lubrication, the average coefficients of friction (ACOF) and wear losses are markedly lower than those of non-textured bearings. S has the greatest influence on the COF curve. When D is 100 µm and S is 24%, the ACOF and wear losses are both lowest, i.e. 0.00426 and 0.51 mg, respectively. Under the same test conditions, compared with the non-textured group, its COF and wear loss decreased by 35.6% and 62.5%, respectively.Originality/valueThis work provides a useful reference for the research on the raceways of textured TRBs.

Thermal Performance of a Dimpled Tube Parabolic Trough Solar Collector (PTSC) with SiO2 Nanofluid

In this research work, dimple texture tubes and silicon dioxide (SiO2) nanofluid were used to analyze the performance parameters of a solar water heater. For this purpose, SiO2 was mixed with deionized (DI) water using an ultrasonic dispersion device to prepare the nanofluids (SiO2/DI-H2O). The size of the nanoparticle was in the range of 10-15 nm. Different volume concentrations of the nanoparticles in the range of 0.1% to 0.5%, in steps of 0.1%, were chosen to prepare the nanofluids to carry out the experiments. Apart from this, computational fluid dynamics (CFD) tool was used to numerically analyze the parameters affecting the performance of the solar water heater, as well as the fluid flow pattern in the dimple texture tube. During the experiment, the mass flow rate of the base fluid (water) varied in the range of 0.5 kg/min to 3.0 kg/min in steps of 0.5 kg/min. The added advantage of the dimple texture tube design led to an increase in turbulence in the flow pattern, resulting 34.2% increase in the convective heat transfer efficiency compared with the plain tube. Among all experimental modules, SiO2/DI-H2O with a mass flow rate of 2.5 kg/min and 0.3% volume concentration gives overall optimized results in absolute energy absorption, gradient temperature, and efficiency of the solar water heater. The efficiency metrics of the experimental results were compared with the simulation results, and it was in the acceptable range with an overall deviation of ±7.42%.

Additive texturing of metallic implant surfaces for improved wetting and biotribological performance

The current study introduces a novel additive texturing method to fabricate samples with dimple and groove textures through the laser-based powder bed fusion (PBF) technique using stainless steel (SS 316L) powder. The topographical analysis shows that the additive textured samples are fabricated with periodic feature sizes less than 150 μm and within an error limit of 7%. Fine grains with an average size of 14.05 μm and 13.62 μm are formed in dimple and groove textured samples, respectively, leading to enhancement of micro-hardness up to 213%. XRD results show the formation of the face-centered cubic (FCC) austenitic phase only. Further, the wettability study indicates hydrophilic wetting behavior with contact angles in the ranges of 72.3°–60.6° for deionized (DI) water and 64.1°–39.9° for hank's balanced salt solution (HBSS). The bio-tribology test with hip-joint prosthesis condition is carried out, and the results indicate that the coefficient of friction (COF) value of 0.11 in a dry condition for groove textured, whereas for dimple textured it is 0.38 under lubricated condition. The details of the study are described in this manuscript.

Influence of spherical protruded and dimple texture on the journal bearing performance: A comparative theoretical analysis implementing JFO boundary conditions

PurposeThe purpose of this paper is to compare the spherical protruded and dimple textured journal bearings performance characteristics with the untextured bearing.Design/methodology/approachThe governing Reynolds equation considering the mass conserving (JFO) boundary conditions is solved using the computationally efficient progressive mesh densification (PMD) method. The central difference scheme is used for the discretization of the governing Reynolds equation. The numerical code developed is validated with the experimental results available in the literature.FindingsFrom this numerical study, it has been observed that the protruded textured journal bearing gives better performance compared to the dimple textured and untextured journal bearing for friction variable, whereas dimple textured journal bearing provides better performance compared to the protruded textured and untextured journal bearing for load carrying capacity and flow coefficient. For better performance, dimple and protruded textured bearings must be textured in second-half textured region configuration.Practical implicationsThe results shown here would be quite useful for the researchers generally and the bearing designers particularly.Originality/valueThe load carrying capacity should be maximum whereas, the friction coefficient should be minimum and also the adequate flow of lubricant is necessary to maintain hydrodynamic lubrication and to remove the heat generated within the bearing due to friction, which impacts the bearing performance and life. Thus, this study would be significant in effective bearing design aspect.

FELINE: Finite element solver for hydrodynamic lubrication problems using the inexact Newton method

In this work we present FELINE, a C++ solver of the Reynolds equation for treating hydrodynamic lubrication problems. To correctly describe cavitation regions, FELINE implements the inexact Newton iteration (INE) algorithm within a finite element method (FEM) framework. The solver was tested and validated against known cases in literature and industrially relevant cases of dimpled textures. Furthermore, we provide a benchmark for a complex dimpled texture case to evaluate the performance and robustness of the implementation. FELINE performs very fast when compared with existing implementations and shows a great degree of stability, while providing physically correct solutions thanks to the INE algorithm. Program summaryProgram title: FELINECPC Library link to program files:https://doi.org/10.17632/srkpysb727.1Licensing provisions: Creative Commons by 4.0Programming language: C++Nature of problem: A fast Reynolds equation solver robust enough to correctly solve the linear complementarity problems that arise from proper treatment of the cavitation boundaries.Solution method: An inexact Newton iteration method implemented within a finite element method framework that properly ensures the complementarity conditions are satisfied by introducing a forcing term.

Development of morphable polishing tools with labyrinth and dimple textures

Inspired by the physical nature and functionality of morphable surfaces, this paper develops the polishing tools with such surface characteristics. The surface textures of morphable polishing tools can be tuned and adapted according to the stage and requirements of the targeted surface finish and material removal rate. To investigate the performance of morphable surfaces in polishing, morphable polishing tools with labyrinth, dimple and hybrid textures were fabricated by curing silicone materials with different Young’s moduli. The morphable polishing tools can be produced with fast responsiveness and reversibility by controlling the air pressure in the tool cavity. Fixed-spot polishing experiments with the developed morphable tools were performed on a copper surface, and the surface morphology, surface roughness and removed volume of polished copper were measured with a laser confocal microscope. Furthermore, static and dynamic polishing forces, polishing pressure distribution and interfacial friction coefficient between the tool and workpiece were obtained and benchmarked in polishing experiments regarding the labyrinth, dimple and hybrid tools. The results show that under the investigated polishing parameters, the roughness of polished surface is the smallest with the dimple tool, higher with the hybrid tool and the labyrinth tool. The material removal volume, static and dynamic polishing forces under different tool offsets are larger in the polishing processes with a dimple tool. In addition, the theoretical and experimental study indicates that the tool surface texture significantly affects the polishing pressure distribution. Labyrinth tools show denser pressure distribution owing to the finer textures of a smaller characteristic length, while dimple tools show sparsely distributed pressure owing to the coarser surface texture.

Surface Properties of Ti6Al7Nb Alloy: Surface Free Energy and Bacteria Adhesion.

The laser micro-machining was carried out on a station equipped with a TruMicro 5325c laser emitting ultraviolet radiation (343 nm wavelength) in picosecond pulses. On the surface of the Ti6Al7Nb alloy, dimple texturing with a constant diameter of ~200 μm, different depths (from ~5 to ~78 μm) and density (from 10% to 50%) were produced. The value of surface free energy was determined with the Owens–Wendt method using two measuring liquids: distilled water and diodomethane. The Staphylococcus epidermidis strain was used to test the adhesion of bacteria. It was found that the surface free energy value is influenced by both of the texture parameters (density, depth). The density also affects the potential for biofilm formation. Based on the analysis, it was shown that with an increase in surface free energy, the number of adhering microorganisms increases exponentially. Moreover, the study shows that there is a correlation between the number of adhering microorganisms and surface free energy.

Effects of liner surface textures on the tribological performance of different production piston rings

AbstractBased on the characteristics of engine working conditions, the ring/liner reciprocating friction tests were conducted to research the effects of three typical cylinder liner surface topographies (honed surface, large dimple texture and small dimple texture) on the tribological performance of production piston ring pack. The experimental results demonstrated the effects of liner textures are different between three kinds of piston rings: for the barrel‐shaped ring‐liner pair, the large or small dimple texture has its specific working condition; for the taper‐faced ring‐liner pair, the oil scraping efficiency and oil distributing stability can be improved by texturing small dimples on liner surface; while the dimple textures have little influence on the friction force of oil control ring‐liner pair. In addition, texturing micro‐dimples on liner is conducive to reducing the surface wear caused by abrasive wear, and the anti‐wear effect of small dimple texture is much better.

On the tribological and machining performance of laser textured sintered carbide cutting tools in turning of Al2024

This study investigates the performance of geometrically defined dimple and groove textures in the turning of Al2024. On-machine testing using combinations of periodic SEM imaging and cutting force capture were used for wear assessments of the textured surfaces and to provide input data for tribology testing. Tribometer investigations were conducted to determine the influences of surface textures on elastohydrodynamic lubrication, influenced by tool-chip contact pressure and entrainment area. The study has shown that both dimple and groove textures can reduce surface friction by influencing mixed and hydrodynamic contact, resulting in reductions of cutting forces.

Influence mechanism of surface texture on the output performance of an ultrasonic motor

PurposeThe purpose of this study is to investigate the influence mechanism of different interface component surface textures on the ultrasonic motor (USM) output performance.Design/methodology/approachThe energy transmission mechanism of the traveling-wave ultrasonic motor 60 (TRUM-60) was numerically and experimentally investigated by fabricating dimple textures with different feature types on the friction material and the stator.FindingsTextured friction material can increase the contact range effectively, and thus, can improve the friction characteristics of the interface and the output performance of the TRUM-60. The experimental results verified the expected influence mechanism and demonstrated that the use of either a textured friction material or stator has a very different effect on USM output performance. A textured PI-based friction material improved the TRUM-60 output performance, resulting in a maximum energy conversion efficiency of 57.11%. However, a textured stator degraded the TRUM-60 output performance, resulting in a minimum energy conversion efficiency of only 44.92%.Originality/valueThe results of this study provide a theoretical foundation for improved USM designs with textured interfaces.

Study on tribological properties of boronized and textured composite surface and its application on camshaft connecting-rod type hydraulic motor

With the high parameter development of low-speed and high-torque hydraulic motors, higher requirements have been placed on the tribological performances of their moving parts. Connecting rod slipper pair, as key friction pair, directly affects the leakage of hydraulic motors. In this paper, a composite wear-resistant surface is fabricated by combining the surface texture and boronizing technology, and the texture parameters are optimized by orthogonal tribological test and then applied to the connecting rod slipper pair for hydraulic motor bench test. For the tribological test: (i) the lubrication performance of composite surface is mainly provided by dynamic pressure generated by dimple texture under oil lubrication condition, (ii) the wear rate increases with the increase of texture diameter and depth, while decreases first and then increases with the increase of area density under starved lubrication condition. The hydraulic motor bench test shows that the wear of the composite treated connecting rod is obviously improved, and the leakage is 47.6% lower than that of connecting rod without treatment. The result demonstrates that the composite surface has the ability to capture wear debris and provide dynamic pressure dues to the textured surface, and thus its wear resistance is obviously improved with collaborative use of the high-hardness boride layer.

Computational Efficiency Improvement of Dimple Textured Hydrodynamic Journal Bearing Using Progressive Mesh Densification Method

Abstract There is a considerable amount of study carried out on textured hydrodynamic bearings. The numerical solution of textured bearings is a matter of concern for the researchers. There are several methods used to estimate the performance parameters of textured bearings. However, progressive mesh densification (PMD) method is not yet used for textured bearings while it has been used for mixed elastohydrodynamic lubrication (EHL) and thermo-EHL problems. In the present analysis, the PMD method is implemented to estimate the performance parameters of the textured journal bearing. It is compared with the multigrid and the fixed mesh methods and found to be very effective in improving computational efficiency.

Effects of textured cylinder liner piston ring on performances of diesel engine under hot engine tests

It has great significance on the performance of cylinder liner-piston ring (CLPR) friction pairs with the different surface textures and affects the service life, reliability, and economy of diesel engines. However, most studies on the surface texture applied to CLPR have concentrated on simulated tests and computations, and the actual hot engine tests were ignored. The aim of this study was to gain insights into the interactions between different types of surface textures and the performance of diesel CLPRs under hot engine conditions. Three types of thread groove textures on cylinder liner surfaces with different widths, including 1, 2, and 3 mm, and a circular dimple texture on a piston ring with a depth of 100 μm were designed and machined, and were then tested under hot test conditions using a four-stroke diesel engine. To investigate the performance of diesel engine using different types of surface textures, the wear mass loss of the piston ring, worn surface morphologies and wear depth of the cylinder liner, exhaust gas emissions performance, and vibration performance of the diesel engine were obtained. Compared with untextured CLPRs, the experimental results indicated that appropriate surface texture (e.g., 3 mm wide grooved texture) significantly affected the comprehensive performance of the diesel engine. These findings will aid in understanding the performance impact of surface texture on diesel under hot engine conditions as well as its actual application to diesel engines.

Tribological behavior of co-textured cylinder liner-piston ring during running-in

The running-in of cylinder liner-piston rings (CLPRs) is the most important process that must be performed before a marine diesel engine can be operated. The quality of running-in directly affects the reliability of a CLPR. The surface texture of a CLPR has been proven to significantly affect its lubrication performance. In this study, the tribological behavior of a CLPR during running-in is investigated. Three types of surface textures are generated on the CLPR via laser processing: dimple texture on piston rings, groove texture on cylinder liners, and co-texture on both sides. Subsequently, a series of tests are performed on a slice tester. A load of 300 N (1.64 MPa) is applied, and two speeds (50 and 100 rpm) are adopted. The CLPR running-in quality is characterized based on three parameters, i.e., the friction coefficient, contact resistance, and wear topography. Experimental results show that, compared with a non-textured surface, the three types of surface textures mentioned above improved the friction performance during running-in. The lubricant supply capacity of the dimple texture on the piston ring, as a mobile oil reservoir, is stronger than that of the groove texture on the cylinder liner serving as a static oil reservoir. By contrast, the wear resistance of the dimple texture, as a movable debris trap on the piston ring, is weaker than that of the groove texture on the cylinder liner, which serves as a static debris trap. It is demonstrated that the co-texture combines the advantages of dimples and groove textures. Compared with non-textured surfaces, the friction coefficient decreased the most at 100 rpm (44.5%), and the contact resistance improved the most at 50 rpm (352.9%). The coupling effect provides the surface with improved running-in quality by optimizing the tribological performance, particularly at the dead center. This study provides guidance for the tribological design and manufacturing of CLPR in marine diesel engines.

Noise Reduction Mechanism and Analysis of TC4 with Dimple Textured Surfaces

Improving the friction-induced noise suppression performance of TC4 has far-reaching significance for its wide application in the field of robots and semiconductors. The friction noises of TC4 with solid lubricant (Sn-Ag-Cu) filled into dimples (TCS) and TC4 were predicted by simulation analysis. The noise reduction performance of TCS during dry rotary sliding was discussed. TCS with dimple size of 0.6 mm (TCS-0.6) exhibited the prominent performance of noise reduction, which was attributed to the synergistic effect of dimples and solid lubricant. During the dry sliding process, the debris were contained by dimples, the stress distribution in matrix was modified by lubricant, and the defects were decreased. Hence, the roughness of worn surface was reduced, which was beneficial to obtaining the stable friction coefficient. Inhibiting the unstable vibration by controlling the friction coefficient of the system can effectively demote the friction-induced noise.