Lubricant Distribution Research Articles

Mixed lubrication friction model including surface texture effects for sheet metal forming

In deep drawing processes, mixed lubrication friction regime is common in which the friction condition is governed by solid–solid asperity contacts and lubricant pressure. In this study, a friction model in the mixed lubrication regime is developed that accounts for the effect of the surface topographies of sheet and tool on the lubricant pressure distribution. The overall friction due to solid–solid asperity contacts and lubricant pressure is determined using a coupled hydrodynamic and boundary friction models. The model is utilized in an in-house FE code (DiekA) for deep drawing simulations. In the FE simulations, the lubricant pressure is determined by solving the average Reynolds equation. The flow factors required in the average Reynolds equation are determined separately using measured tool and sheet surface topographies. Cross-die experiments are performed at different lubricant amounts to validate the friction model at a component level. The results show that punch force vs. displacement and strain field from experiments and FE simulations (using the new friction model) correlate very well.

An optical tomographic method to characterize the mist distribution in MQL Tools

Proper mist flow is important to Minimum Quantity Lubrication (MQL) machining as only a small amount of lubricant-air mixture is applied to the cutting zone. This paper presents an optical-tomography-based method to visualize the lubricant distribution of MQL mist flow in through-tool channels, particularly for drilling. High-speed images of the flow are acquired from multiple view angles to capture the 2D projections of 3D flow. The Filter Back Projection (FBP) algorithm is used to perform tomography and produce tomographic reconstruction image of the lubricant distribution in the through-tool channels. The method is validated with a known annular flow created using a vertical pipe flow. The method is also applied to two 3D printed drill bits, one with two straight channels and another with two helical channels to emulate actual through-tool channel geometries of drills. The tomographic reconstructions obtained using FBP match with the literature and show a clear influence of the channel geometry on the lubricant distribution. Physical, imaging, and lighting requirements to achieve proper results using this technique are also detailed in the paper.

The influence of protruding silicon particle shape on the friction performance of Al–Si alloy

The surface of Al–Si alloy samples was produced by chemical etching and laser finishing. After both chemical etching and laser finishing, the silicon particles could be exposed on the surface, resulting in improving the friction performance of Al–Si alloy. The edge shapes of the protruding silicon particles were different in the two surface treatments. Besides, the edges of protruding silicon particles were sharp after chemical etching. As a result, the edges were damaged in friction, and even some of silicon particle could shed. Then, it was easy for the abrasive wear to occur on the surface. There were obvious vortices on both sides of protruding silicon particle with sharp edge in the fluid region, resulting in a comparatively weak lubrication. In contrast, the edges of protruding silicon particles were round after laser finishing. Moreover, silicon particles could be closely combined with aluminum matrix due to the rapid cooling after being heated by laser, meanwhile, it was difficult for them to be separated from the matrix during friction. There were no vortices occurring on both sides of protruding silicon particle with round edge in fluid region, presenting excellent lubrication. Besides, the samples by laser finishing owned a low friction coefficient. Thus, the Al–Si alloy samples by laser finishing, with round edges of silicon particle, exhibiting a better friction performance. Consequently, the micro-mechanisms of friction performance associated with the edge shape of protruding silicon particle such as better lubrication and uniform stress distribution of rounded edge were determined.

Innovative Meshing Strategies for Bearing Lubrication Simulations

Efficiency improvement is the new challenge in all fields of design. In this scenario the reduction of power losses is becoming more and more a main concern also in the design of power transmissions. Appropriate models to predict power losses are therefore required from the earliest stages of the design phase. The aim of this project is to carry out lubrication simulations of several variants of a cylindrical roller bearing to understand the lubricant distribution and the related churning power losses. Several strategies to reduce the computational effort were used. Among them the sectorial symmetry and three innovative meshing strategies (purely analytical with and without interfaces and analytical/subtractive) that were implemented in the OpenFOAM® environment. The results of the different approaches were compared among them and reasonable savings in terms of computational effort were shown.

Monitoring lubricant addition in pharmaceutical tablet manufacturing through passive vibration measurements in a V-blender

In tablet manufacturing, a lubricant is added in a tumbling mixer prior to compression to ensure that the tablet is ejected smoothly without sticking or breakage. Control and monitoring of this process is critical as process parameters can negatively affect final tablet properties. Inline monitoring methods including passive vibration measurements could be implemented to improve process efficiency. This method is non-invasive, non-destructive, and has a reduced cost compared to other monitoring techniques. Using an accelerometer affixed to the lid of a V-blender, magnesium stearate was added to glass beads and granule formulations and monitored to determine the effect of lubricant concentration, particle size, and particle size distribution on vibration measurements. Mixing end-points were identified and changes in mixing profiles were reflected in signal amplitude and variation. This research indicates that passive vibration measurements have the potential to be used as a real-time inline monitoring method for lubricant addition.

Dynamic Analysis of the Structure of Automobile Components, Obtained by Powder Metallurgy

The analysis of the dynamic behavior of parts from the structure of the cationing mechanism of an internal combustion engine in 4 steps is followed. Thus, kinetic and dynamic models were developed for the motor mechanism considered as an assembly consisting of crankshaft, connecting rods, bearings and pistons. Dynamic models were built mainly in the Ansys program, based on the finite element method. The following problems were addressed, namely the dynamic analysis, with the determination of the response in time for displacements, stresses and deformations and also the vibration analysis in order to analyze the frequency response for the kinematic parameters of the whole system, but also of the component elements. Dynamic models for the numerical processing of the two types of analyzes were designed in a parameterized system with multiple possibilities of working on different time, frequency or different types of loadings and connection conditions. The purpose of this paper is to study the dynamic response of the main elements of the mechanism, for different types of materials. Given the wide field of applicability in automobiles, the technology for obtaining parts from sintered powders, the studies were realized for the cases when the connecting rod and the bearings are made of metallic powders, respectively of steel, to be extended for more complex cases, when we consider the influence of lubricant and temperature distribution in areas of practical interest.

Towards reliable optimization of metal powder—Lubricant mixing for high die filling performance: Exploring a rheology based approach

A previously unreported approach to optimize the time of an industry scale mixing operation for best filling performance, while ensuring premix uniformity, is tested. Mixing a base metal powder with a lubricant facilitates compacting and ejecting of powder compacts. However, the quality of lubricant admixing directly influences premix flowability and, therefore, the die filling performance of the premix. Insufficient lubricant admixing leads to non-uniform lubricant distribution, while excessive mixing, − to segregation or flowability degradation.Approximately 1.5 metric tons of a powder mix based on FL 4405 and a lubricant containing lithium compounds are mixed in a double cone blender. The optimum mixing time is estimated using a set of powder rheology measurements. It is then validated through conventional premix flowability and uniformity tests including Hall flowrate and burn-off-based probing of lubricant distribution, respectively. A streamlined subset of the performed characterization steps for the optimization of other premix formulations is proposed.

HIV Prevention Via Mobile Messaging for Men Who Have Sex With Men (M-Cubed): Protocol for a Randomized Controlled Trial.

BackgroundMen who have sex with men (MSM) continue to be the predominately impacted risk group in the United States HIV epidemic and are a priority group for risk reduction in national strategic goals for HIV prevention. Modeling studies have demonstrated that a comprehensive package of status-tailored HIV prevention and care interventions have the potential to substantially reduce new infections among MSM. However, uptake of basic prevention services, including HIV testing, sexually transmitted infection (STI) testing, condom distribution, condom-compatible lubricant distribution, and preexposure prophylaxis (PrEP), is suboptimal. Further, stronger public health strategies are needed to promote engagement in HIV care and viral load suppression among MSM living with HIV. Mobile health (mHealth) tools can help inform and encourage MSM regarding HIV prevention, care, and treatment, especially among men who lack access to conventional medical services. This protocol details the design and procedures of a randomized controlled trial (RCT) of a novel mHealth intervention that comprises a comprehensive HIV prevention app and brief, tailored text- and video-based messages that are systematically presented to participants based on the participants’ HIV status and level of HIV acquisition risk.ObjectiveThe objective of the RCT was to test the efficacy of the Mobile Messaging for Men (M-Cubed, or M3) app among at least 1200 MSM in Atlanta, Detroit, and New York. The goal was to determine its ability to increase HIV testing (HIV-negative men), STI testing (all men), condom use for anal sex (all men), evaluation for PrEP eligibility, uptake of PrEP (higher risk HIV-negative men), engagement in HIV care (men living with HIV), and uptake of and adherence to antiretroviral medications (men living with HIV). A unique benefit of this approach is the HIV serostatus-inclusiveness of the intervention, which includes both HIV-negative and HIV-positive MSM.MethodsMSM were recruited through online and venue-based approaches in Atlanta, Detroit, and New York City. Men who were eligible and consented were randomized to the intervention (immediate access to the M3 app for a period of three months) or to the waitlist-control (delayed access) group. Outcomes were evaluated immediately postintervention or control period, and again three and six months after the intervention period. Main outcomes will be reported as period prevalence ratios or hazards, depending on the outcome. Where appropriate, serostatus/risk-specific outcomes will be evaluated in relevant subgroups. Men randomized to the control condition were offered the opportunity to use (and evaluate) the M3 app for a three-month period after the final RCT outcome assessment.ResultsM3 enrollment began in January 2018 and concluded in November 2018. A total of 1229 MSM were enrolled. Data collection was completed in September 2019.ConclusionsThis RCT of the M3 mobile app seeks to determine the effects of an HIV serostatus–inclusive intervention on the use of multiple HIV prevention and care-related outcomes among MSM. A strength of the design is that it incorporates a large sample and broad range of MSM with differing prevention needs in three cities with high prevalence of HIV among MSM.Trial RegistrationClinicalTrials.gov NCT03666247; https://clinicaltrials.gov/ct2/show/NCT03666247International Registered Report Identifier (IRRID)DERR1-10.2196/16439

Pengembangan Sistem Inventory Control Pada Perusahaan PT Alam Indah Utama

Alam Indah Utama are official pertamina lubricant dealer in bali. Alam Indah Utama moves in lubricant distribution on pertamina oil. Alam Indah utama as a official dealer had an advantages to buy the oil direct from Pertamina. Alam Indah Utama used system that pertamina gave and the second system are internal system. And in this journal will talk about improving the Alam Indah Utama’s internal inventory stock system. With hope can make the internal system that can show the stocks, customer, supplier and past transaction.

A COMPREHENSIVE FLUID-SOLID INTERACTION ANALYSIS OF FINITE JOURNAL BEARINGS

As key elements in plenty of rotating machinery, the elastohydrodynamic performance of journal bearings should be carefully checked in light of the design and operating parameters considered. This first part of the current study aims to numerically analyse the operation of journal bearings under alignment conditions. In the fluid-solid interaction analysis conducted, the lubricant flow field is solved using the finite volume method. Based on finite elements strategy, a structural analysis is then implemented to the solid bearing using the pressure distribution computed earlier on its inner surface. A wide range of operating conditions has been considered including the eccentricity ratio (0.1≤ε≤0.9), bearing length-diameter ratio (0.8≤L/D≤2), and rotation speed (4,000≤N≤10,000 rpm). Three principal categories of operational quantities have inspected, namely; the lubricant pressure distribution, overall performance parameters, and structural aftereffects. Among all the parameters examined, the eccentricity ratio is the most influential one on the performance of journal bearings. As it increases with applying heavier loads, a significant rise occurs in each of the friction force, power loss, stress levels, and deformation on the inner surface of the bearing. The bearing length and rotation speed, on the other hand, affect the bearing performance as well, but to a less extent.

Investigation of lubricant transfer and distribution at head/disk interface in air-helium gas mixtures

Lubricant transfer and distribution at the head/disk interface in air-helium gas mixtures is investigated using a developed model that combines an air-bearing model with a molecular dynamics model. The pressure distribution is calculated by the air-bearing model at the head/disk interface with respect to the helium content and the pressure obtained is then input to the molecular dynamics model to understand the lubricant transfer mechanism. Finally, the effects of pressure at the boundary condition and disk velocity on lubricant transfer are discussed in relation to the helium fraction within the air-helium gas mixtures. Results show there is a decrease in the pressure difference with an increase in the helium percentage, which leads to a decrease in the volume of the lubricant transferred. The results also suggest that the lubricant is not easily to transfer in gas mixtures with a high percentage of helium, even when both higher disk velocities and pressure boundary conditions are applied.

Tool Texturing for Deep Drawing Applications

The application of surface texturing on sheet metal is a widely used approach to improve lubrication and control friction in deep drawing applications. However, it has been shown that current texturing processes are not robust to produce uniform textures on the sheet due to rapid and severe wear on texture-rolls. Furthermore, in multi-stage forming processes, deterioration of the sheet texture even at the first stage of forming makes texturing of the sheet metal surface ineffective. Tool surface texturing is a new method to control friction and tool wear in metal forming industry. In the current study, a multi-scale friction model is adopted to investigate the effect of tool texturing on the evolution of friction during sheet metal forming operations. The multi-scale friction model accounts for surface topography changes due to deformation of asperities and ploughing of tool asperities on the sheet metal surface, mixed lubrication regime and furthermore the tool micro-texture effects on lubricant distribution at tool-sheet metal interface. The model is validated with respect to strip-draw experiments using different tool textures. The model is later applied to the simulation of a U-bend forming process. The results show that using textured tools, it is possible to reduce friction and punch force in sheet metal forming processes. The model can be used to tailor and optimize textures on stamping tools for complex parts.

Real-time Visualization of Lubricant Films on Head Slider Using an Ellipsometric Microscope

As the recording density increased in hard disk drives (HDDs), the head disk interface (HDI) spacing has been decreased to 2-3 nm during its operation. The head slider may pick up the lubricant at this contact or near-contact HDI. Therefore, a real-time visualization of lubricant thickness distribution on a slider surface is essential to study the physical mechanisms for reducing the head disk interface spacing. A vertical-objective-based ellipsometric microscope (VEM) was presented as the effective method for real-time visualization of nm- thick lubricant films on disks with high lateral resolution. However, extinction coefficient of head slider is low, which means the intensity of reflected light may be reduced. In this report, the feasibility of VEM used for head observation is discussed, and the images of polar perfluoropolyether (PFPE) lubricant Zdol4000 applied on head slider are obtained by the current setup. It indicates that this method can be used in real-time visualization of nm-thick lubricant films on head slider.

Quantification of lubrication and particle size distribution effects on tensile strength and stiffness of tablets

We adopt a Quality by Design (QbD) paradigm to better control the mechanical properties of tablets. To this end, the effect of particle size distribution, lubricant concentration, and mixing time on the tensile strength and elastic modulus of tablets is studied. Two grades of lactose, monohydrate and spray-dried, are selected. Tablets are compressed to different relative densities ranging from 0.8 to 0.94 using an instrumented compaction simulator. We propose a general model, which predicts the elastic modulus and tensile strength envelope that a specific powder can obtain based on its lubrication sensitivity for different particle size distributions. This is possible by introducing a new dimensionless parameter in the existing tensile strength and elastic modulus relationships with relative density. A wide range of lubrication conditions is explored and a predictable model is calibrated. The mechanical properties of lactose monohydrate tablets are noticeably dependent on particle size, unlike spray-dried lactose where little to almost no sensitivity to particle size is observed. The model is designed in a general fashion that can capture mechanical quality attributes in response to different lubrication conditions and particle size, and it can be extended to powders than undergo different deformation mechanisms, complex mixtures, and doubly convex tablets. Therefore, the model can be used to map the achievable design space of any given formulation.

Influence of Test Stand and Contact Size Sensitivity on the Friction Coefficient in Sheet Metal Forming

The precise knowledge of frictional behavior is highly relevant for accurate modelling in sheet metal forming simulations. This allows e.g., the precise prediction of restraining forces which, in turn, determines an optimal draw bead strategy and blank-texture-development for automotive components. As a result, tryout loops can be avoided and thus production costs can be reduced. Nevertheless, the benefit of this detailed friction description is often ignored by the use of a constant friction coefficient. Finding a practical solution has motivated numerous research projects in recent decades. In this context, many efforts have been made to develop test stands to gain a better understanding of friction and to determine load-dependent friction coefficients for simulations. However, different test stands for friction investigation show a big quantitative difference in friction value which makes the direct use of the values in finite element simulation questionable. Therefore, the focus of this paper is to compare two different common strip drawing tests and detect the sources of deviation. In particular, the influence of the contact area between tool and blank is investigated. The results indicate that while the effect of the different test stands is negligible, a high dependency of the friction coefficient on the contact area was shown. This phenomenon is caused by macroscopic lubricant distribution over the contact area, which varies according to the size of the tools. The results show a potential field of research in categorizing different friction test stands and resolving the issue of quantitative non-comparable coefficients of friction.

A new reverse engineering method to combine FEM and CFD simulation three-dimensional insight into the chipping zone during the drilling of Inconel 718 with internal cooling

ABSTRACTThe use of cooling lubricants in metal machining increases both the tool life and the quality of workpieces and improves the overall sustainability of production systems. In addition to fulfilling these main functions, the focus of machining processes is also related to the reduction of environmental pollution. This can for example be achieved by an optimized arrangement of the cutting tool cooling channels. Therefore, the active cutting edges of the tool should be effectively supplied with a sufficient amount of cooling lubricant. An analysis of the tribological stress is rather difficult because the complex contact zone is inaccessible. Hence, optical investigations are often limited to only observing the chip formation or analyzing the process without considering the influence of the chips.This article presents an innovative method, which enables a deeper three-dimensional insight into the chip formation zone during drilling with internal cooling channels, considering the cooling lubricant distribution and chip formation. The chip formation simulation based on the finite element method and the computational fluid dynamics flow simulation are combined. In this way, the differences between the different geometric models that do not allow any joint generation of numerical information due to missing interfaces are overcome.

Influence of Donut-Shaped Bump on the Hydrodynamic Lubrication of Textured Parallel Sliders

The influence of donut-shaped bump texture on the hydrodynamic lubrication performance for parallel surfaces is presented in this paper. A mathematical equation has been applied to express the shape of three-dimensional donut-shaped bump texture. Numerical simulation of the pressure distribution of lubricant between a textured slider and a smooth, moving slider has been performed to analyze the geometrical parameters' influence on the hydrodynamic performance for textured surfaces. The numerical results show that the convex of the donut-shaped bump provides a microstep slider, which can form a convergent wedge and build up hydrodynamic pressure. Optimum values of horizontal spacing and bump height are obtained to maximize the hydrodynamic pressure. It is also noted that the average pressure increases monotonically with the increase of bump radius, but decreases with the increase of vertical spacing and dimple depth, respectively.

A Study of Lubricant Inertia Effects for Squeeze Film Dampers Incorporated into High-Speed Turbomachinery

This work proposes a numerical model that incorporates the effect of lubricant inertia on the hydrodynamic pressure distribution, fluid film reaction forces, and the fluid velocity component profiles for finite-length open-ended squeeze film dampers (SFDs). Firstly, the thin film flow equations for the SFD in presence of fluid inertia effects are introduced. Furthermore, a small first-order perturbation by means of the expressions for the fluid film velocity components and the lubricant pressure distribution that are expanded in power series of the squeeze film Reynolds number is applied to the flow equations. Subsequently the developed lubricant flow equations are solved to develop expressions for the velocity component profiles and the hydrodynamic pressure distribution in SFDs. The pressure expression is numerically solved by using Gauss–Seidel method with finite difference discretization. Moreover, the fluid film reaction forces are determined by numerically integrating the hydrodynamic pressure expressions over the journal surface. Additionally, the proposed pressure distribution expression and the numerical SFD forces are incorporated into a simulation model and the simulation results are compared with the existing models in the literature under different operating conditions, including eccentricity ratios and inertia effects (i.e., Reynolds numbers). The simulation results demonstrate the significant influence of both convective and temporal (i.e., unsteady) lubricant inertia terms on the SFD hydrodynamic pressure distribution and the fluid film reaction forces. Furthermore, the proposed SFD model is incorporated into a multi-mass flexible rotordynamic model to evaluate the effect of SFD fluid inertia on the mass unbalance induced steady-state vibrations of the rotor and the nodal transient orbits by implementing finite element method and transient modal integration with predictor–corrector solver. The results of the analysis demonstrate the significant effect of fluid inertia on the resonance frequencies of the rotor and the steady-state vibration amplitudes and the transient orbits at the resonance zone.

Experimental study of elastohydrodynamic lubrication behaviour under single oil droplet supply

In this study, an oil droplet passing through an elastohydrodynamic lubrication contact is observed via interferometry, and the effects of droplet size, entrainment speed, load, and slide/roll ratio (SRR) are studied. The results show that the surface area of the droplet is enlarged because of the squeeze spread and capillary force at the inlet region, which influence the film growth. With a large droplet size, the spreading diameter increases and a thick film is generated. When the entrainment speed increases, the surface area enlargement of the oil droplet at the inlet is found to be insufficient, and only a local dimple-shaped film is formed. The SRR has a direct effect on the lubricant distribution. In particular, the load and viscosity effects exhibit different characteristics compared with the case of typical fully flooded lubrication.

Microstructural Characterization of Solid State Reaction Phase Formed During Sintering of Hexagonal Boron Nitride with Iron.

In the development of dry self-lubricating composites, not only solid lubricant particle size and distribution are important, but also the correct selection of the solid lubricant characteristics, which should be stable, i.e. not reactive, during the whole processing. In this work, Fe+9 vol% h-BN composites were produced by uniaxial cold compaction and sintering, for which a reaction between h-BN and iron was detected after sintering at 1,150°C. The reaction phase was characterized by optical and scanning electron microscopy and identified by X-ray diffraction and energy-dispersive X-ray spectroscopy. The newly formed phase had high hardness when compared with the iron matrix. The resulting composites presented a high friction coefficient and high wear.