Mohammad Tauviqirrahman

Numerical study of the load-carrying capacity of lubricated parallel sliding textured surfaces including wall slip

This article analyzes the combined effect of surface texturing and wall slip on the load-carrying capacity of parallel sliding systems. A new modified Reynolds equation with slip is proposed, based on the critical shear stress model, to reveal the hydrodynamic load-carrying capacity. A range of parameters such as texturing zone, texture cell aspect ratio, critical shear stress, and slip length are analyzed. It is shown that the optimal texturing zone length oscillates around 75% of the slider length. A slight shift of the optimized texturing zone toward the inlet of the contact is observed when the critical shear stress is increased. The numerical analysis also shows that there is a unique threshold value of the critical shear stress for every texture cell aspect ratio. When this ratio is increased, the threshold value increases, thus influencing the slip considerably. Slip has a positive effect on the load-carrying capacity for critical shear stress lower than the threshold value, whereas it has no effect on higher values. It is also found that in comparison with a solely textured surface, the load-carrying capacity of the combined textured/wall slip pattern can be increased by around 300% using the optimized slip parameters.

Numerical Study of Salat Movements for Total Hip Replacement Patient

Salat as a daily Muslim activitiy in praying contains several movements which are not suggested by orthopaedic doctor to be conducted by patient with total hip replacement (THR). Sujud and sitting are two movements in Salat which is recommended to be done above the chair for THR patients. There are lacks of scientific discussions about the consequences of the normal salat movement for Muslim THR patients. This paper observes the effect of these movements to the artificial hip joint in THR patient body. A three-dimensional finite element simulation is used to investigate the resisting moment, the contact pressure and the von Mises stress. An artificial hip joint model proposed by previous researcher is used in the simulations. The results show that sujud induces the impingement and plastic deformation whereas sitting is relatively safe to be conducted by THR patients. Some suggestions are also discussed with respect to the design of new artificial hip joint model which allows THR patients to conduct Salat in a normal way. The reduction of inset at the liner, the new profile at circumferential edge inner liner and the increase in the femoral head diameter can be considered as a guideline for new design of the artificial hip joint for Muslim.

Numerical analysis of tire/contact pressure using finite element method

The interaction between the road surface and vehicle’s tire may significantly determine the stability of a vehicle. We could study the tire contact-pressure to road surfaces through a numerical simulation in this present study. In particular, the main purpose of the study was to present an illustration of the effect of the varied loads to the tire, which would affect the contact pressure on the road surface sand stress distribution on the tire by employing a commercial ABAQUS software, based on the finite element method. To make the process of data analysis easier, the tire was assumed to be made from natural rubber which composition consisted of 2 layers of the inner tire and 1 layer of carcass. In pre-conditions, the tire was given air pressure as much as 17 psi, and loads as much as 2 KN, 6 KN, and 10 KN; then, the air pressure was increased to be 30 psi; consequently, the simulation results of stress distribution and deformation on each of loads condition would be acquired. The simulation results indi...

Induction Hardening of Carbon Steel Material: The Effect of Specimen Diameter

Induction hardening is well developed technology in many industrial applications, e.g. automotive, tool manufacturing, casting technology, sheet metal forming etc. The surface hardened medium carbon steels are widely used for critical automotive and machine components such as propulsion shafts, crankshafts and steering knuckles which require high fatigue resistance. However, some of small and medium sized enterprises, focused in metal manufacturing in Indonesia have not complete practical knowledge in employing induction hardening to harden the mechanical components. This paper present a technical report of induction hardening process for medium carbon steel material with considering the effect of specimen diameter. The results show that the increase of the specimen diameter increases the current input requirement which also increase the power requirement as a consequence. The induction frequency is automatically decrease when the specimen diameter is increase and resulted in the deeper hardening layer on the surface. The hardness layer of specimen A ranges from outer surface to 6 mm from the surface whereas specimen B ranges from outer surface to 10 mm from the surface from. The micro structure evolution from the surface to the center of the specimen for the both specimen is almost similar. It is mostly affected by the heating temperature and heat distribution from the surface to the center of specimen.

Modeling of Repeated Rolling Contact on Rough Surface: Surface Topographical Change

An finite element analysis (FEA) of a repeated rolling contact over an elastic-plastic deforming rough surface is performed. The surface topographical change is calculated to determine the running-in phase to the steady-state rolling contact situation. A rigid hemisphere is repeatedly rolled over a rough flat aluminum surface and the effect of the contact load and the number of overrollings is studied. It is found that the change in surface topography due to the repeated rolling contact results in smoothening of the rough surface due to the flattening of the highest asperities. The result shows that the running-in of the repeated rolling contact takes place within the first few overrollings.

Numerical investigation of the combined effects of slip and texture on tribological performance of bearing

Slider bearings are used in many applications. An increase in the load support may allow for saving of energy. In this work, in order to enhance the load support and decrease the friction force, a combined textured surface bearing using boundary slip is discussed. A modified Reynolds equation with slip is adopted. With the main goal of evaluating the effects of slip and texture, a parametric analysis is performed. For the given operating conditions, texturing features as well as slip pattern are analysed in detail. The numerical analysis is undertaken under the condition of different gap ratio values and the slip-textured area. The results show that combined techniques of slip and texture have a significant effect on the improvement of the tribological performance of bearing, that is, a high load support but low friction force. The gap ratio of the bearing is shown to have a significant effect on the lubrication behaviour. It is found that even with a smallest gap ratio (parallel gap), a high load support can be produced. However, it is also shown that the gap ratio appears to contribute to the generated friction force and the volume flow rate more than the boundary slip. Further analysis indicates that the optimum slip-text zones for certain gap ratio are highlighted. These findings may provide references for designing hydrodynamic-textured slider bearing considering boundary slip.

Tribological characteristic enhancement effects by polymer thickened oil in lubricated sliding contacts

Polymer thickened oils are the most preferred materials for modern lubrication applications due to their high shear. The present paper explores a lubrication mechanism in sliding contact lubricated with polymer thickened oil considering cavitation. Investigations are carried out by using a numerical method based on commercial CFD (computational fluid dynamic) software ANSYS for fluid flow phenomenon (Fluent) to assess the tribological characteristic (i.e. hydrodynamic pressure distribution) of lubricated sliding contact. The Zwart-Gerber-Belamri model for cavitation is adopted in this simulation to predict the extent of the full film region. The polymer thickened oil is characterized as non-Newtonian power-law fluid. The simulation results show that the cavitation lead lower pressure profile compared to that without cavitation. In addition, it is concluded that the characteristic of the lubrication performance with polymer thickened oil is strongly dependent on the Power-law index of lubricant.

A Comparative Study of Finite Journal Bearing in Laminar and Turbulent Regimes Using CFD (Computational Fluid Dynamic)

In this paper, an investigation of hydrodynamic performance for journal bearing lubricated by thin film is performed by three-dimensional CFD (computational fluid dynamic). Two regimes, i.e. laminar and turbulent regimes are of main interest. The sliding velocity was varied from 3000, 5000 and 10000. The numerical simulation shows that the velocity magnitude of the journal has a strong effect on the hydrodynamic pressure. In addition, it is found that an appropriate modelling of flow regime affects the predicted lubrication performance. From the overall analysis, both using laminar and turbulent regimes, the distribution of static hydrodynamic pressure shows a similar trend. It is also found that at the beginning of the contact, the static pressure is low, and then, it gradually increases to the highest point, and finally drops significantly.

3D Numerical study on the effect of shaft eccentricity on the tribological performance of lubricated sliding contact

Sustainable water supply has been the United Nation’s goal as stipulated in Sustainable Development Goals (SDG’s). In 2030, all people must have acess to safe and affordable drinking water. In Salatiga Indonesia, the water supply company (PDAM) can now only serves 65.64% of the city’s population. There are about 11.14% of the population served by community based water supply (CBWS). In line with the SDG’s, The Government of Indonesia’s program to have 100% coverage of water supply. The limitation on PDAM coverage has led the increase number of CBWS. This tendency has raised the question on the sustainability of CBWS. This paper presents the sustainability evaluations of some CBWS in Salatiga using Rapfish method. In the method, sustainability is evaluated using multi-dimensional scalling based on aspects of ecological, technological, social, institutional, and economical. The strategy to improve sustainability is identified using SWOT analysis. The study performed at 4 (four) CBWS at Kecamatan Sidorejo, Salatiga. It represents the CBWS using deep water sources and spring water sources. It shows that all CBWS analysed are barely sustainable on the dimension of ecological, technological, and social. The dimension on institutional and economical are in the status of no sustainability. Therefore, the CBWS need some improvement and reinforcement especially on institutional and economical.

Theoretical investigation of boundary slip on the hydrodynamic lubrication performance in pocketed bearings including cavitation

Boundary slip in bearings is becoming more and more popular to improve the hydrodynamic performance (pressure and shear stress). However, most of previously published works regarding textured bearings neglected the cavitation effect and make their results questionable. The main aim of this paper is to investigate the hydrodynamic performance of slip pocketed bearings considering cavitation by a theoretical approach. Cavitation was of particular interest with respect to pressure generation and shear stress. One main result presented here was that slip over the whole surface could retard the presence of cavitation and therefore the generated pressure and shear stress could be optimal. The work presented here leads to a design reference guideline that could be used by the designer/engineer to design slip pocketed bearings for improving the hydrodynamic performance.