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Fulltext Effects of lubrication in warm powder compaction process

Rahman, M.M., Nor, S.S.M., Rahman, H.Y.

ASM Science Journal, 2011;5(1):11-18.
MyJurnal

Warm compaction is an advanced manufacturing technique which consists of two consecutive steps, i.e. powder compaction at above ambient temperature and sintering in a controlled environment. Due to the relative movement between the powder mass and die wall as well as sliding among powder particles, frictional force is generated during the compaction stage. Admixed lubricant is used during the compaction step in order to minimize friction and hence improve the uniformity of the density of distribution inside the component. However, during the sintering process, trapped lubricant is often found to be burnt out hence leaving pores or voids which result in the lower strength of the final products. Warm compaction was initiated in the nineties, however not much information has been published about the effects of lubrication on the quality of the components produced through this route. Therefore, this paper presents the outcome of an experimental investigation about the effects of lubrication on manufacturing near-net shape components through the warm compaction route. Iron powder ASC 100.29 was mixed mechanically with zinc stearate to prepare the feedstock. Mixing time, weight percentage of lubricant content and compaction temperature were varied during green compact generation while sintering temperature, heating rate and holding time were manipulated during sintering. The relative densities and strengths of the final products were investigated at every compaction as well as sintering parameter. The results revealed that lubrication could provide significant effects at the compaction temperature of 180ºC while no significant effect of lubrication was observed during sintering. The suitable lubricant content was found to be 0.4 wt% and mixing time was around 30 min and the sintering temperature was around 990ºC.

Matched MeSH terms: Friction
Fulltext The Study of Drag Reduction on Ships Inspired by Simplified Shark Skin Imitation

Ibrahim MD, Amran SNA, Yunos YS, Rahman MRA, Mohtar MZ, Wong LK, et al.

Appl Bionics Biomech, 2018;2018:7854321.
PMID: 29853998 DOI: 10.1155/2018/7854321

The skin of a fast swimming shark reveals riblet structures that help reduce the shark's skin friction drag, enhancing its efficiency and speed while moving in the water. Inspired by the structure of the shark skin denticles, our team has carried out a study as an effort in improving the hydrodynamic design of marine vessels through hull design modification which was inspired by this riblet structure of shark skin denticle. Our study covers on macroscaled design modification. This is an attempt to propose an alternative for a better economical and practical modification to obtain a more optimum cruising characteristics for marine vessels. The models used for this study are constructed using computer-aided design (CAD) software, and computational fluid dynamic (CFD) simulations are then carried out to predict the effectiveness of the hydrodynamic effects of the biomimetic shark skins on those models. Interestingly, the numerical calculated results obtained show that the presence of biomimetic shark skin implemented on the vessels give about 3.75% reduction of drag coefficient as well as reducing up to 3.89% in drag force experienced by the vessels. Theoretically, as force drag can be reduced, it can lead to a more efficient vessel with a better cruising speed. This will give better impact to shipping or marine industries around the world. However, it can be suggested that an experimental procedure is best to be conducted to verify the numerical result that has been obtained for further improvement on this research.

Matched MeSH terms: Friction
Fulltext MHD radiative nanofluid flow induced by a nonlinear stretching sheet in a porous medium

Jafar AB, Shafie S, Ullah I

Heliyon, 2020 Jun;6(6):e04201.
PMID: 32637680 DOI: 10.1016/j.heliyon.2020.e04201

In this article, we numerically investigate the influence of thermal radiation and heat generation on the flow of an electrically conducting nanofluid past a nonlinear stretching sheet through a porous medium with frictional heating. The partial differential equations governing the flow problems are reduced to ordinary differential equations via similarity variables. The reduced equations are then solved numerically with the aid of Keller box method. The influence of physical parameters such as nanoparticle volume fraction ϕ, permeability parameter K, nonlinear stretching sheet parameter n, magnetic field parameter M, heat generation parameter Q and Eckert number Ec on the flow field, temperature distribution, skin friction and Nusselt number are studied and presented in graphical illustrations and tabular forms. The results obtained reveal that there is an enhancement in the rate of heat transfer with the rise in nanoparticle volume fraction and permeability parameter. The temperature distribution is also influenced with the presence of K, Q, R and ϕ. This shows that the solid volume fraction of nanoparticle can be used in controlling the behaviours of heat transfer and nanofluid flows.

Matched MeSH terms: Friction
Fulltext Correlation between the bending strength and the thickness interlayer of alumina-mild steel friction welded at lower rotational speed

Mohamad Zaky Noh, Luay Bakir Hussain, Zainal Arifin Ahmad

Journal of Nuclear and Related Technologies, 2007;2007(1):75-82.
MyJurnal

The joining of ceramic-metal could be done through a few techniques: brazing, diffusion bonding, friction welding etc. However, the mechanism of ceramic-metal joining was still not properly understood. In this study, alumina rod was bonded to mild steel rod via friction welding technique by using Al 1100 sheet as interlayer. The diameter of the rods was 10 mm. Friction pressure of 20 MPa and forging pressure of 40 MPa were used. Rotational speeds were maintained at 900 rpm and friction times of 2 to 20 seconds were applied. The joining strength was determined through four point bending test. The maximum bending strength, 240 MPa was obtained at the friction times of 20 seconds. Under optical microscope and SEM observation, the deformation of the aluminum interface was clearly obtained. Mechanical interlocking and close contact between the aluminaaluminum and aluminum-mild steel were observed at magnifications of 3000X. The strength of alumina-steel bonding is much dependent on the wettability of the alumina surface by the molten aluminum and the existing of mechanical interlocking between interlayer and sample materials.

Matched MeSH terms: Friction
Fulltext Design and fabrication of brake pad testing apparatus for teaching and learning application

Leman, A.M., Che Wan Izzudin, Md Zin Ibrahim, Dafit Feriyanto

Journal of Occupational Safety and Health, 2015;12(2):87-92.
MyJurnal

Brake pad apparatus is designed for help student and instructor in teaching and learning application. The objective
of this research is to differentiate the pressure effect and braking temperature condition of different pad. This apparatus
also aimed for learning the safety car and motorcycle braking system. This apparatus can to compare with theoretical
calculation in order to approve that this apparatus is useful. The main concept in this apparatus is thermocouple use
to detect the temperature gain while braking process. Speed motor controller used for set the angular velocity of the
motor in braking process. Pressure applied at brake pedal detected by pressure gauge and data logger function as a
connector. This apparatus also designed based on valid data for average of teenager in Malaysia which made on a
sample university student. Result show that the apparatus can function effectively by defines the different temperature
when applied the different pressure and different pad. Pad C shows the 880C for thermocouple 1 and 790C for
thermocouple 2 at the 20 psi and infrared thermometer show 1130C for pad C. Graph from calculation shows that the
pad A have 216.480C at 1000 rpm which have low temperature than pad B, C and D. high efficiency of friction and
pressure applied will cause more heat generate than low coefficient of friction and pressure applied.

Matched MeSH terms: Friction
Friction at nanopillared polymer surfaces beyond Amontons' laws: Stick-slip amplitude coefficient (SSAC) and multiparametric nanotribological properties

Ishak MI, Dobryden I, Martin Claesson P, Briscoe WH, Su B

J Colloid Interface Sci, 2021 Feb 01;583:414-424.
PMID: 33011410 DOI: 10.1016/j.jcis.2020.09.038

Frictional and nanomechanical properties of nanostructured polymer surfaces are important to their technological and biomedical applications. In this work, poly(ethylene terephthalate) (PET) surfaces with a periodic distribution of well-defined nanopillars were fabricated through an anodization/embossing process. The apparent surface energy of the nanopillared surfaces was evaluated using the Fowkes acid-base approach, and the surface morphology was characterized using scanning electron microscope (SEM) and atomic force microscope (AFM). The normal and lateral forces between a silica microparticle and these surfaces were quantified using colloidal probe atomic force microscopy (CP-AFM). The friction-load relationship followed Amonton's first law, and the friction coefficient appeared to scale linearly with the nanopillar height. Furthermore, all the nanopillared surfaces showed pronounced frictional instabilities compared to the smooth sliding friction loop on the flat control. Performing the stick-slip amplitude coefficient (SSAC) analysis, we found a correlation between the frictional instabilities and the nanopillars density, pull-off force and work of adhesion. We have summarised the dependence of the nanotribological properties on such nanopillared surfaces on five relevant parameters, i.e. pull-off force fp, Amontons' friction coefficient μ, RMS roughness Rq, stick-slip amplitude friction coefficient SSAC, and work of adhesion between the substrate and water Wadh in a radar chart. Whilst demonstrating the complexity of the frictional behaviour of nanopillared polymer surfaces, our results show that analyses of multiparametric nanotribological properties of nanostructured surfaces should go beyond classic Amontons' laws, with the SSAC more representative of the frictional properties compared to the friction coefficient.

Matched MeSH terms: Friction
A facile, bio-based, novel approach for synthesis of covalently functionalized graphene nanoplatelet nano-coolants toward improved thermo-physical and heat transfer properties

Sadri R, Hosseini M, Kazi SN, Bagheri S, Abdelrazek AH, Ahmadi G, et al.

J Colloid Interface Sci, 2018 Jan 01;509:140-152.
PMID: 28898734 DOI: 10.1016/j.jcis.2017.07.052

In this study, we synthesized covalently functionalized graphene nanoplatelet (GNP) aqueous suspensions that are highly stable and environmentally friendly for use as coolants in heat transfer systems. We evaluated the heat transfer and hydrodynamic properties of these nano-coolants flowing through a horizontal stainless steel tube subjected to a uniform heat flux at its outer surface. The GNPs functionalized with clove buds using the one-pot technique. We characterized the clove-treated GNPs (CGNPs) using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). We then dispersed the CGNPs in distilled water at three particle concentrations (0.025, 0.075 and 0.1wt%) in order to prepare the CGNP-water nanofluids (nano-coolants). We used ultraviolet-visible (UV-vis) spectroscopy to examine the stability and solubility of the CGNPs in the distilled water. There is significant enhancement in thermo-physical properties of CGNPs nanofluids relative those for distilled water. We validated our experimental set-up by comparing the friction factor and Nusselt number for distilled water obtained from experiments with those determined from empirical correlations, indeed, our experimental set-up is reliable and produces results with reasonable accuracy. We conducted heat transfer experiments for the CGNP-water nano-coolants flowing through the horizontal heated tube in fully developed turbulent condition. Our results are indeed promising since there is a significant enhancement in the Nusselt number and convective heat transfer coefficient for the CGNP-water nanofluids, with only a negligible increase in the friction factor and pumping power. More importantly, we found that there is a significant increase in the performance index, which is a positive indicator that our nanofluids have potential to substitute conventional coolants in heat transfer systems because of their overall thermal performance and energy savings benefits.

Matched MeSH terms: Friction
Comfort and frictional properties of dental gloves

Roberts AD, Brackley CA

J Dent, 1996 Sep;24(5):339-43.
PMID: 8916648

OBJECTIVES: A survey of general dental practitioners and dental surgery assistants was carried out to ascertain their preferences and opinions on powder-free hydrogel-coated gloves compared with starch-powdered gloves. The aim was to relate the survey findings to laboratory measurements of the frictional characteristics of glove inner surfaces and their water absorptive capability.
METHODS: The survey was carried out using a questionnaire given to local dental practitioners. Glove friction and water absorption measurements were made using specially designed equipment.
RESULTS: The survey showed that a selected group of dentist and dental surgery assistants preferred hydrogel-coated gloves, particularly for damp donning, durability and long-term wear comfort. Laboratory measurements showed that the hydrogel coating gave a low friction coefficient against damp skin. The coating was durable, and absorbed water more readily than other treatments.
CONCLUSION: A survey of dental practitioners and dental surgery assistants and laboratory measurements indicates that hydrogel-coated gloves have superior properties, and are preferred to other non-sterile glove types.

Matched MeSH terms: Friction
Engine performance and emission characteristics of palm biodiesel blends with graphene oxide nanoplatelets and dimethyl carbonate additives

Razzaq L, Mujtaba MA, Soudagar MEM, Ahmed W, Fayaz H, Bashir S, et al.

J Environ Manage, 2021 Mar 15;282:111917.
PMID: 33453625 DOI: 10.1016/j.jenvman.2020.111917

This study investigated the engine performance and emission characteristics of biodiesel blends with combined Graphene oxide nanoplatelets (GNPs) and 10% v/v dimethyl carbonate (DMC) as fuel additives as well as analysed the tribological characteristics of those blends. 10% by volume DMC was mixed with 30% palm oil biodiesel blends with diesel. Three different concentrations (40, 80 and 120 ppm) of GNPs were added to these blends via the ultrasonication process to prepare the nanofuels. Sodium dodecyl sulphate (SDS) surfactant was added to improve the stability of these blends. GNPs were characterised using Scanning Electron Microscope (SEM) and Fourier Transform Infrared (FTIR), while the viscosity of nanofuels was investigated by rheometer. UV-spectrometry was used to determine the stability of these nanoplatelets. A ratio of 1:4 GNP: SDS was found to produce maximum stability in biodiesel. Performance and emissions characteristics of these nanofuels have been investigated in a four-stroke compression ignition engine. The maximum reduction in BSFC of 5.05% and the maximum BTE of 22.80% was for B30GNP40DMC10 compared to all other tested blends. A reduction in HC (25%) and CO (4.41%) were observed for B30DMC10, while a reduction in NOx of 3.65% was observed for B30GNP40DMC10. The diesel-biodiesel fuel blends with the addition of GNP exhibited a promising reduction in the average coefficient of friction 15.05%, 8.68% and 3.61% for 120, 80 and 40 ppm concentrations compared to B30. Thus, combined GNP and DMC showed excellent potential for utilisation in diesel engine operation.

Matched MeSH terms: Friction
Fulltext Quantification of Gait Stability During Incline and Decline Walking: The Responses of Required Coefficient of Friction and Dynamic Postural Index

Abdul Yamin NAA, Basaruddin KS, Abu Bakar S, Salleh AF, Mat Som MH, Yazid H, et al.

J Healthc Eng, 2022;2022:7716821.
PMID: 36275397 DOI: 10.1155/2022/7716821

This study aims to investigate the gait stability response during incline and decline walking for various surface inclination angles in terms of the required coefficient of friction (RCOF), postural stability index (PSI), and center of pressure (COP)-center of mass (COM) distance. A customized platform with different surface inclinations (0°, 5°, 7.5°, and 10°) was designed. Twenty-three male volunteers participated by walking on an inclined platform for each inclination. The process was then repeated for declined platform as well. Qualysis motion capture system was used to capture and collect the trajectories motion of ten reflective markers that attached to the subjects before being exported to a visual three-dimensional (3D) software and executed in Matlab to obtain the RCOF, PSI, as well as dynamic PSI (DPSI) and COP-COM distance parameters. According to the result for incline walking, during initial contact, the RCOF was not affected to inclination. However, it was affected during peak ground reaction force (GRF) starting at 7.5° towards 10° for both walking conditions. The most affected PSI was found at anterior-posterior PSI (APSI) even as low as 5° inclination during both incline and decline walking. On the other hand, DPSI was not affected during both walking conditions. Furthermore, COP-COM distance was most affected during decline walking in anterior-posterior direction. The findings of this research indicate that in order to decrease the risk of falling and manage the inclination demand, a suitable walking strategy and improved safety measures should be applied during slope walking, particularly for decline and anterior-posterior orientations. This study also provides additional understanding on the best incline walking technique for secure and practical incline locomotion.

Matched MeSH terms: Friction
The impact of surface and geometry on coefficient of friction of artificial hip joints

Choudhury D, Vrbka M, Mamat AB, Stavness I, Roy CK, Mootanah R, et al.

J Mech Behav Biomed Mater, 2017 08;72:192-199.
PMID: 28500998 DOI: 10.1016/j.jmbbm.2017.05.011

Coefficient of friction (COF) tests were conducted on 28-mm and 36-mm-diameter hip joint prostheses for four different material combinations, with or without the presence of Ultra High Molecular Weight Polyethylene (UHMWPE) particles using a novel pendulum hip simulator. The effects of three micro dimpled arrays on femoral head against a polyethylene and a metallic cup were also investigated. Clearance played a vital role in the COF of ceramic on polyethylene and ceramic on ceramic artificial hip joints. Micro dimpled metallic femoral heads yielded higher COF against a polyethylene cup; however, with metal on metal prostheses the dimpled arrays significantly reduced the COF. In situ images revealed evidence that the dimple arrays enhanced film formation, which was the main mechanism that contributed to reduced friction.

Matched MeSH terms: Friction*
Thermal radiation effects on heat and mass transfer of magnetohydrodynamics dusty jeffrey fluid past an exponentially stretching sheet

Siti Nur Haseela Izani, Anati Ali

MATEMATIKA, 2019;35(2):187-200.
MyJurnal

The heat and mass transfer of steady magnetohydrodynamics of dusty Jeffrey fluid past an exponentially stretching sheet in the presence of thermal radiation have been investigated. The main purpose of this study is to conduct a detailed analysis of flow behaviour of suspended dust particles in non-Newtonian fluid. The governing equations hav been converted into dimensionless form, and then solved numerically via the Keller-box method. The expression of Sherwood number, Nusselt number and skin friction have been evaluated, and then displayed in tabular forms. Velocity, temperature and concentration profiles are presented graphically. It is observed that large value of dust particles mass concentration parameter has reduced the flow velocity significantly. Increase in radiation parameter enhances the temperature, whereas the increment in Schmidt number parameter reduces the concentration.

Matched MeSH terms: Friction
g-Jitter free convection flow of nanofluid in the three-dimensional stagnation point region

Mohamad Hidayad Ahmad Kamal, Anati Ali, Sharidan Shafie

MATEMATIKA, 2019;35(2):260-270.
MyJurnal

The three dimensional free convection boundary layer flow near a stagnation point region is embedded in viscous nanofluid with the effect of g-jitter is studied in this paper. Copper (Cu) and aluminium oxide (Al2O3) types of water base nanofluid are cho- sen with the constant Prandtl number, Pr=6.2. Based on Tiwari-Das nanofluid model, the boundary layer equation used is converted into a non-dimensional form by adopting non- dimensional variables and is solved numerically by engaging an implicit finite-difference scheme known as Keller-box method. Behaviors of fluid flow such as skin friction and Nusset number are studied by the controlled parameters including oscillation frequency, amplitude of gravity modulation and nanoparticles volume fraction. The reduced skin friction and Nusset number are presented graphically and discussed for different values of principal curvatures ratio at the nodal point. The numerical results shows that, in- crement occurs in the values of Nusset number with the presence of solid nanoparticles together with the values of the skin friction. It is worth mentioning that for the plane stagnation point there is an absence of reduced skin friction along the y-direction where as for axisymmetric stagnation point, the reduced skin friction for both directions are the same. As nanoparticles volume fraction increased, the skin friction increased as well as the Nusset number. The results, indicated that skin frictions of copper are found higher than aluminium oxide.

Matched MeSH terms: Friction
Unsteady free convection flow between two vertical parallel plates with newtonian heating

Fasihah Zulkiflee, Ahmad Qushairi Mohamad, Sharidan Shafie, Arshad Khan

MATEMATIKA, 2019;35(2):117-127.
MyJurnal

Free convection flow in a boundary layer region is a motion that results from the interaction of gravity with density differences within a fluid. These differences occur due to temperature or concentration gradients or due to their composition. Studies per- taining free convection flows of incompressible viscous fluids have received much attention in recent years both theoretically (exact or approximate solutions) and experimentally. The situation where the heat be transported to the convective fluid via a bounding sur- face having finite heat capacity is known as Newtonian heating (or conjugate convective flows). In this paper, the unsteady free convection flow of an incompressible viscous fluid between two parallel plates with Newtonian heating is studied. Appropriate non- dimensional variables are used to reduce the dimensional governing equations along with imposed initial and boundary conditions into dimensionless forms. The exact solutions for velocity and temperature are obtained using the Laplace transform technique. The corresponding expressions for skin friction and Nusselt number are also calculated. The graphical results are displayed to illustrate the influence of various embedded parameters such as Newtonian heating parameter and Grashof number. The results show that the effect of Newtonian heating parameter increases the Nusselt number but reduces the skin friction.

Matched MeSH terms: Friction
Fulltext Staged Surgery for Severe Soft Tissue and Bone Loss of the Knee

Chan, C.K., Goh, J.H., Ng, W.M., Kwan, M.K., Merican, A.M., Soong, K.L.

Malays Orthop J, 2010;4(2):40-43.
MyJurnal

A 20- year-old female student was involved in a motor vehicle accident. She sustained a severe friction injury to the left knee that resulted in considerable soft tissue and bone loss. There was also damage to the knee extensor mechanism, tibialis anterior muscle, femoral trochlea, the anterior half of the tibial plateau extending distally to the proximal tibia and skin. However, there was no crushing of the limb or resultant neurovascular deficit but cancellous bone and the remainder of the joint were exposed. Repeated surgical debridement was performed and was followed by covering of the soft tissue using a latissimus dorsi free flap and skin grafts. The bony defect was reconstituted with antibiotic bone cement to prevent flap adherence and shrinkage, enhance stability and prevent fracture. The cement was later removed at the time of arthrodesis at which time an ipsilateral double barrel vascularised fibular graft supplemented with autogenously cancellous bone and a ring fixator was used. Computer tomography confirmed union at three months post procedure. The fixator was then removed and a tibialis posterior transfer was performed.

Matched MeSH terms: Friction
Fulltext Synovial Cyst: A Culprit for Recalcitrant Iliotibial Band Syndrome: A Case Report

Yeoh C, Lim G, Sathappan SS

Malays Orthop J, 2015 Nov;9(3):68-70.
PMID: 28611916 DOI: 10.5704/MOJ.1511.011

We present the case of a 56-year old gentleman who presented with recalcitrant iliotibial band (ITB) friction syndrome which did not improve with various modalities of conservative treatment. Magnetic Resonance Imaging (MRI) of the affected knee did not show pathology typical of ITB friction syndrome. However, open exploration revealed a synovial cyst deep to the iliotibial band, abutting against the anterolateral capsule. The presence of distinctive clinical signs on physical examination should alert clinicians to consider knee synovial cyst as a differential diagnosis when dealing with recalcitrant ITB syndrome.

Matched MeSH terms: Friction
Fulltext Microstructural, Tribology and Corrosion Properties of Optimized Fe3O4-SiC Reinforced Aluminum Matrix Hybrid Nano Filler Composite Fabricated through Powder Metallurgy Method

Ashrafi N, Azmah Hanim MA, Sarraf M, Sulaiman S, Hong TS

Materials (Basel), 2020 Sep 15;13(18).
PMID: 32942621 DOI: 10.3390/ma13184090

Hybrid reinforcement's novel composite (Al-Fe3O4-SiC) via powder metallurgy method was successfully fabricated. In this study, the aim was to define the influence of SiC-Fe3O4 nanoparticles on microstructure, mechanical, tribology, and corrosion properties of the composite. Various researchers confirmed that aluminum matrix composite (AMC) is an excellent multifunctional lightweight material with remarkable properties. However, to improve the wear resistance in high-performance tribological application, hardening and developing corrosion resistance was needed; thus, an optimized hybrid reinforcement of particulates (SiC-Fe3O4) into an aluminum matrix was explored. Based on obtained results, the density and hardness were 2.69 g/cm3, 91 HV for Al-30Fe3O4-20SiC, after the sintering process. Coefficient of friction (COF) was decreased after adding Fe3O4 and SiC hybrid composite in tribology behaviors, and the lowest COF was 0.412 for Al-30Fe3O4-20SiC. The corrosion protection efficiency increased from 88.07%, 90.91%, and 99.83% for Al-30Fe3O4, Al-15Fe3O4-30SiC, and Al-30Fe3O4-20SiC samples, respectively. Hence, the addition of this reinforcement (Al-Fe3O4-SiC) to the composite shows a positive outcome toward corrosion resistance (lower corrosion rate), in order to increase the durability and life span of material during operation. The accomplished results indicated that, by increasing the weight percentage of SiC-Fe3O4, it had improved the mechanical properties, tribology, and corrosion resistance in aluminum matrix. After comparing all samples, we then selected Al-30Fe3O4-20SiC as an optimized composite.

Matched MeSH terms: Friction
Fulltext Texture Evolution in AA6082-T6 BFSW Welds: Optical Microscopy and EBSD Characterisation

Tamadon A, Pons DJ, Clucas D, Sued K

Materials (Basel), 2019 Oct 01;12(19).
PMID: 31581446 DOI: 10.3390/ma12193215

One of the difficulties with bobbin friction stir welding (BFSW) has been the visualisation of microstructure, particularly grain boundaries, and this is especially problematic for materials with fine grain structure, such as AA6082-T6 aluminium as here. Welds of this material were examined using optical microscopy (OM) and electron backscatter diffraction (EBSD). Results show that the grain structures that form depend on a complex set of factors. The motion of the pin and shoulder features transports material around the weld, which induces shear. The shear deformation around the pin is non-uniform with a thermal and strain gradient across the weld, and hence the dynamic recrystallisation (DRX) processes are also variable, giving a range of observed polycrystalline and grain boundary structures. Partial DRX was observed at both hourglass boundaries, and full DRX at mid-stirring zone. The grain boundary mapping showed the formation of low-angle grain boundaries (LAGBs) at regions of high shear as a consequence of thermomechanical nature of the process.

Matched MeSH terms: Friction
Fulltext Evaluation of the Effects of Cement and Lime with Rice Husk Ash as an Additive on Strength Behavior of Coastal Soil

Eliaslankaran Z, Daud NNN, Yusoff ZM, Rostami V

Materials (Basel), 2021 Feb 28;14(5).
PMID: 33670914 DOI: 10.3390/ma14051140

Coastal accretion and erosion are unavoidable processes as some coastal sediments undergo modification and stabilization. This study was conducted to investigate the geotechnical behavior of soil collected from Bagan Lalang coast and treated with lime, cement, and rice husk ash (RHA) to design a low-cost alternative mixture with environmentally friendly characteristics. Laboratory tests were carried out to analyze the physical properties of the soil (Atterberg limits and compaction properties), together with mechanical characteristics (direct shear and unconfined compressive strength (UCS) tests) to determine the effect of different ratios of stabilizer/pozzolan on the coastal soil and the optimum conditions for each mixture. Part of the purpose of this study was also to analyze the shear behavior of the coastal soil and monitor the maximum axial compressive stress that the treated specimens can bear under zero confining pressure. Compared to the natural soil, the soil treated with lime and rice husk ash (LRHA) in the ratio of 1:2 (8% lime content) showed a tremendous increase in shear stress under the normal stress of 200 kPa. The strength parameters such as the cohesion (c) and internal friction angle (ϕ) values showed a significant increase. Cohesion values increased considerably in samples cured for 90 days compared to specimens cured for 7 days with additional LRHA in the ratio of 1:2 (28%).

Matched MeSH terms: Friction
Fulltext Laser-Assisted High Speed Machining of 316 Stainless Steel: The Effect of Water-Soluble Sago Starch Based Cutting Fluid on Surface Roughness and Tool Wear

Yasmin F, Tamrin KF, Sheikh NA, Barroy P, Yassin A, Khan AA, et al.

Materials (Basel), 2021 Mar 09;14(5).
PMID: 33803364 DOI: 10.3390/ma14051311

Laser-assisted high speed milling is a subtractive machining method that employs a laser to thermally soften a difficult-to-cut material's surface in order to enhance machinability at a high material removal rate with improved surface finish and tool life. However, this machining with high speed leads to high friction between workpiece and tool, and can result in high temperatures, impairing the surface quality. Use of conventional cutting fluid may not effectively control the heat generation. Besides, vegetable-based cutting fluids are invariably a major source of food insecurity of edible oils which is traditionally used as a staple food in many countries. Thus, the primary objective of this study is to experimentally investigate the effects of water-soluble sago starch-based cutting fluid on surface roughness and tool's flank wear using response surface methodology (RSM) while machining of 316 stainless steel. In order to observe the comparison, the experiments with same machining parameters are conducted with conventional cutting fluid. The prepared water-soluble sago starch based cutting fluid showed excellent cooling and lubricating performance. Therefore, in comparison to the machining using conventional cutting fluid, a decrease of 48.23% in surface roughness and 38.41% in flank wear were noted using presented approach. Furthermore, using the extreme learning machine (ELM), the obtained data is modeled to predict surface roughness and flank wear and showed good agreement between observations and predictions.

Matched MeSH terms: Friction

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