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Safari, Alaleh
Publications (10 of 10) Show all publications
Safari, A., Emami, N. & Cervantes, M. J. (2018). Viscoelasticity and shear-thinning effects on bio-polymer solution and suspended particle behaviours under oscillatory curve Couette flow conditions. Biosurface and Biotribology, 4(1), 1-17
Open this publication in new window or tab >>Viscoelasticity and shear-thinning effects on bio-polymer solution and suspended particle behaviours under oscillatory curve Couette flow conditions
2018 (English)In: Biosurface and Biotribology, ISSN 2405-4518, Vol. 4, no 1, p. 1-17Article in journal (Refereed) Published
Abstract [en]

Formation of wear particles within total hip replacement is one of the main causes of its failure. In addition to improving the lubrication and wear resistance of materials used as bearing surfaces, understanding of wear particle distribution patterns within lubricants inside an implant gap could be used to improve design parameters and implants’ lifespan. In this study, the behaviours of biolubricants (with compositions similar to human joint synovial fluid) and suspended particles were investigated by micro-particle image velocimetry in curved mini channels under oscillatory Couette flow conditions. The studied biolubricants had shear-thinning viscoelastic characteristics. The authors found that increasing shear-thinning, elasticity or motion frequency levels did not affect the trend behaviours of biolubricant flows due to the low strain values of the experimental conditions applied. However, suspended particles formed strings along flow directions and exhibited cross-stream migration to channel walls. Motion frequency, fluid shear thinning and elasticity characteristics and channel dimensions strongly affected particle behaviours.

Place, publisher, year, edition, pages
IET Digital Library, 2018
National Category
Engineering and Technology Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Fluid Mechanics and Acoustics
Research subject
Machine Elements; Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-68670 (URN)10.1049/bsbt.2018.0002 (DOI)
Note

Validerad;2018;Nivå 1;2018-08-16 (andbra)

Available from: 2018-05-07 Created: 2018-05-07 Last updated: 2018-10-08Bibliographically approved
Safari, A., Espanol, M., Ginebra, M.-P., Cervantes, M. & Emami, N. (2017). Effect of dynamic loading versus static loading on the frictional behavior of a UHMWPE pin in artificial biolubricants. Biosurface and Biotribology, 3(1), 35-44
Open this publication in new window or tab >>Effect of dynamic loading versus static loading on the frictional behavior of a UHMWPE pin in artificial biolubricants
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2017 (English)In: Biosurface and Biotribology, ISSN 2405-4518, Vol. 3, no 1, p. 35-44Article in journal (Refereed) Published
Abstract [en]

To obtain reliable results from in vitro measurements on the tribological behavior of joint implant materials, the parameters of the measurements must simulate in vivo conditions. Although the nature of the load in human joints is dynamic, most of the studies using simple pin-on-disk tribometers were performed with a constant load. The current study focused on investigating the effect of dynamic loading in comparison with static loading in the tribological behavior of ultra-high-molecular-weight polyethylene (UHMWPE) sliding against a cobalt chromium molybdenum (CoCrMo) counter surface with different lubricants, where the effects of hyaluronic acid (HA) and protein content in the lubricants were also investigated. The results suggested that although the dynamic loading did not affect the friction evolution for any of the lubricants, the friction value decreased for the lubricants that did not contain HA. The results showed that higher protein content in the lubricant increased the friction coefficient, however, it provided the highest protection against wear for sliding surfaces.

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Fluid Mechanics and Acoustics
Research subject
Machine Elements; Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-62639 (URN)10.1016/j.bsbt.2017.03.001 (DOI)
Note

Validerad; 2017; Nivå 1; 2017-05-02 (rokbeg)

Available from: 2017-03-23 Created: 2017-03-23 Last updated: 2018-09-13Bibliographically approved
Safari, A. (2017). Time dependent flow of biolubricant and suspended particles behavior within total hip replacement. (Doctoral dissertation). Luleå University of Technology
Open this publication in new window or tab >>Time dependent flow of biolubricant and suspended particles behavior within total hip replacement
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Total hip replacement (THR) has been one of the most successful surgeries in the 21st century. Ultra-high-molecular-weight-polyethylene (UHMWPE) shows favorable mechanical and tribological properties when used as a bearing surface material in THR. However, produced UHMWPE wear particles challenge increasing the THR lifetimes. Bone loss (osteolysis) initiated by these wear particles is a major cause of total joint arthroplasty failure in both hip and knee prosthesis.

In addition to improving the wear resistance of bearing surfaces to reduce wear, wear debris distribution mechanisms within the joint gap must also be thoroughly investigated. These particles distribute within lubricant and across the implant gap. Synovial fluid (SF) lubricates natural joints which is a viscoelastic non-Newtonian shear thinning fluid. The non-Newtonian behavior of SF is attributed to its hyaluronic acid (HA) content which is a linear biopolymer. The distribution patterns of wear particles within total joint replacement are affected by the special rheological behaviors of the SF, geometrical parameters, particle size and shape distribution and particle-fluid interactions. Therefore, understanding wear particles distribution pattern is pivotal to understand the mechanism and eventually minimizing third-body wear of the UHMWPE acetabular liner in THR.

According to fluid mechanics forces, the size and density of wear particles suggests that wear particles follow lubricant movements. However, over a matter of hours, such particles show specific behaviors within viscoelastic fluid (not visible in Newtonian fluid) such as particle migration and string formation along the flow direction.

The main aim of this project was to develop and validate an experimental method for assessing characteristics of HA and artificial SF solutions and behaviors of wear particles in a viscoelastic fluid flow. The effects of different parameters such as HA concentration, protein content, fluid flow types (steady, unsteady, etc.) and gap shapes on fluid behavior were quantified to fully understand such mechanisms.

In this project, micro particle image velocimetry (micro-PIV) was applied as the quantitative flow visualization method. Pin-on-disk tribo-measurement was performed as a complimentary study to investigate the tribological behaviors of a UHMWPE pin rotating against a cobalt chromium molybdenum (CoCrMo) disk in the presence of HA solutions of various concentrations. This study was conducted to understand the effects of dynamic loading on lubricant performance relative to those of static loading.

The results showed that under oscillatory flow conditions, strain levels, rates, and distributions are important parameters that affect the flow behaviors of HA solutions. Particle migration and alignment were affected by channel sizes, HA concentrations, flow types and the elastic instability of the solution.

The tribological study results suggested that in the presence of HA, sinusoidal dynamic loading does not affect the frictional behaviors of UHMWPE moving against CoCrMo in comparison with static loading.

Place, publisher, year, edition, pages
Luleå University of Technology, 2017. p. 94
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-61756 (URN)978-91-7583-810-6 (ISBN)978-91-7583-811-3 (ISBN)
Public defence
2017-03-31, E231, Luleå, 13:00 (English)
Opponent
Supervisors
Available from: 2017-02-06 Created: 2017-02-01 Last updated: 2018-01-13Bibliographically approved
Safari, A., Cervantes, M. & Emami, N. (2016). Bio-lubricant Behavior under Reciprocating Motion in Mini-Channel (ed.). Paper presented at STLE Annual Meeting & Exhibition : 15/05/2016 - 19/05/2016. Paper presented at STLE Annual Meeting & Exhibition : 15/05/2016 - 19/05/2016.
Open this publication in new window or tab >>Bio-lubricant Behavior under Reciprocating Motion in Mini-Channel
2016 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

Synovial fluid (SF) is articular joint lubrication. It contains a linear biopolymer called Hyaluronic acid(HA), which causes the viscoelastic behavior. Several studies on viscoelasticity of synovial fluid orHA solutions with different concentration and molecular weight have been carried out withrheometers. However, there are very few studies on the effect of viscoelasticity on HA solutionsmovement and velocity distribution inside the joint gap. Therefore, in this study, HA solutions withdifferent concentrations were studied under a sinusoidal reciprocating movement inside a rectangularmini-channel. This study focuses on deriving velocity distribution along channel width with MicroParticle Image Velocimetry (micro-PIV). Very high viscosity of the HA solutions suggests a quasisteadybehavior for this solution under investigated sinusoidal movement. However, the resultsindicated that the steady state laws are not applicable for estimating the HA behavior because ofspecial polymeric behavior of the HA chains inside the solutions.

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Fluid Mechanics and Acoustics
Research subject
Machine Elements; Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-37185 (URN)b2173d2a-858c-41ad-8926-f7ddfa0b12ee (Local ID)b2173d2a-858c-41ad-8926-f7ddfa0b12ee (Archive number)b2173d2a-858c-41ad-8926-f7ddfa0b12ee (OAI)
Conference
STLE Annual Meeting & Exhibition : 15/05/2016 - 19/05/2016
Note
Godkänd; 2016; 20160722 (alasaf)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2018-03-08Bibliographically approved
Safari, A., Cervantes, M. & Emami, N. (2016). Bio-lubricant Behavior under Reciprocating Motion in Mini-Channel. In: : . Paper presented at 71st STLE Annual Meeting & Exhibition.
Open this publication in new window or tab >>Bio-lubricant Behavior under Reciprocating Motion in Mini-Channel
2016 (English)Conference paper, Oral presentation with published abstract (Refereed)
National Category
Mechanical Engineering Fluid Mechanics and Acoustics Medical Engineering
Identifiers
urn:nbn:se:ltu:diva-71943 (URN)
Conference
71st STLE Annual Meeting & Exhibition
Available from: 2018-12-06 Created: 2018-12-06 Last updated: 2018-12-06
Safari, A., Emami, N. & Cervantes, M. (2016). Bio-lubricant flow behaviour in mini-channels (ed.). Lubrication Science, 28(4), 221-242
Open this publication in new window or tab >>Bio-lubricant flow behaviour in mini-channels
2016 (English)In: Lubrication Science, ISSN 0954-0075, E-ISSN 1557-6833, Vol. 28, no 4, p. 221-242Article in journal (Refereed) Published
Abstract [en]

One of the most common causes of failures in total joint replacements is the generation of wear particles within the joint. This contributes to bone lost and aseptic loosening of the implant, eventually requiring its replacement. Many studies have been carried out to improve the wear characteristics of bearing surfaces in total joint replacement. From the lubrication point of view, the friction behaviour of surfaces and rheology of the joint lubricant (synovial fluid) have been extensively studied. However, little attention has been paid to the interaction between the lubricant and the bearing surfaces. The aim of this study is to develop a methodology for studying the behaviour of bio-based lubricant in mini-channels. For this purpose, micro-particle image velocimetry was used in order to characterise the lubricant behaviour. Channels made of relevant materials such as ultra-high molecular weight polyethylene, cobalt–chromium–molybdenum alloy and titanium–aluminium–vanadium alloy with 1 and 1.5 mm width, 45 mm length and 2 mm depth were experimentally investigated. Results suggested that the used polymeric solution interaction with solid surfaces is very sensitive to the polymer concentration in the lubricant. Moreover, it was observed that there exist differences between water (Newtonian reference fluid) and the polymeric solution behaviour even at very simple movements; although usually, the properties of this lubricant at high shear rates are estimated by water properties.

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Fluid Mechanics and Acoustics
Research subject
Machine Elements; Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-8713 (URN)10.1002/ls.1328 (DOI)000383722300003 ()2-s2.0-84966470342 (Scopus ID)73ea7014-caf1-42f2-9e3a-9f0595d1ee89 (Local ID)73ea7014-caf1-42f2-9e3a-9f0595d1ee89 (Archive number)73ea7014-caf1-42f2-9e3a-9f0595d1ee89 (OAI)
Note

Validerad; 2016; Nivå 2; 20160330 (alasaf)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Safari, A., Cervantes, M. & Emami, N. (2016). Viscoelastic behaviour effect of hyaluronic acid on reciprocating flow inside mini-channel (ed.). Lubrication Science, 28(8), 521-544
Open this publication in new window or tab >>Viscoelastic behaviour effect of hyaluronic acid on reciprocating flow inside mini-channel
2016 (English)In: Lubrication Science, ISSN 0954-0075, E-ISSN 1557-6833, Vol. 28, no 8, p. 521-544Article in journal (Refereed) Published
Abstract [en]

One of the most successful surgeries during the 21st century is total joint replacement (TJR) with material combination of polymer-on-metal (PoM). Despite its success, wear particle generation at the interface of the polymer and metal causes eventually implant loosening. Investigating and understanding the wear particles distribution should help in designing implants with better performances. First step towards characterising wear particle distribution is deriving the lubricant behaviour and velocity distribution inside implant gap. Different hyaluronic acid (HA) solutions were subjected to a sinusoidal movement in straight rectangular channels. The velocity profiles along the channel width were measured with Micro Particle Image Velocimetry. HA solution behaviour was found to be dependent on the concentration. Results showed significant differences between the water (Newtonian) and HA behaviour in unsteady flow. The unsteady behaviour of the lubricant depended strongly on its non-Newtonian viscoelastic behaviour which was due to the time dependent nature of HA solution.

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Fluid Mechanics and Acoustics
Research subject
Machine Elements; Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-8598 (URN)10.1002/ls.1344 (DOI)000387584800003 ()2-s2.0-8499453037 (Scopus ID)71ddbd58-5181-435c-b427-8e4ed4292822 (Local ID)71ddbd58-5181-435c-b427-8e4ed4292822 (Archive number)71ddbd58-5181-435c-b427-8e4ed4292822 (OAI)
Note

Validerad; 2016; Nivå 2; 2016-11-25 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Safari, A., Emami, N. & Cervantes, M. (2015). Reciprocation Flow Behavior of Bio-Lubricant in Mini-Channels. In: : . Paper presented at EEIGM conference.
Open this publication in new window or tab >>Reciprocation Flow Behavior of Bio-Lubricant in Mini-Channels
2015 (English)Conference paper, Oral presentation only (Refereed)
National Category
Materials Engineering Composite Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-71947 (URN)
Conference
EEIGM conference
Available from: 2018-12-06 Created: 2018-12-06 Last updated: 2018-12-06
Safari, A., Ginebra, M. P., Emami, N. & Cervantes, M. (2014). Studying Water Based Lubricant Behavior in Mini-Channel (ed.). Paper presented at Nordic Symposium on Tribology : 10/06/2014 - 13/06/2014. Paper presented at Nordic Symposium on Tribology : 10/06/2014 - 13/06/2014.
Open this publication in new window or tab >>Studying Water Based Lubricant Behavior in Mini-Channel
2014 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

One of the most common causes of failures in total joint replacements is the generation of wear particles within the joint that leads to the micro separation at the implant-bone interface. This contributes to bone lost aseptic loosening of the implant, requiring eventually its replacement.Many studies have been carried out to improve the wear characteristics of bearing surfaces in total joint replacement (TJR). From lubrication point of view the friction behavior of surfaces and rheology of the joint lubricant (Synovial fluid) were extensively studied. However, not much attention was paid to the interaction between the lubricant and the bearing surfaces. The aim of this study is to develop a methodology for studying the behavior of water based lubricant in a micro-channel. For this purpose, Micro-PIV (Particle Image velocimetry) was used in order to characterize the lubricant behavior. Experimental models made of relevant materials such as ultra high molecular weight polyethylene, Cobalt-Chromium-Molybdenum alloy and Titanium-Aluminum-Vanadium alloy with 1 and 1.5 mm width, 45 mm length and 2 mm depth experimentally investigated.

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Fluid Mechanics and Acoustics
Research subject
Machine Elements; Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-38063 (URN)c5496799-d039-4553-9491-f4eb3e75ab8e (Local ID)c5496799-d039-4553-9491-f4eb3e75ab8e (Archive number)c5496799-d039-4553-9491-f4eb3e75ab8e (OAI)
Conference
Nordic Symposium on Tribology : 10/06/2014 - 13/06/2014
Note
Godkänd; 2014; 20140618 (andbra)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2018-03-08Bibliographically approved
Safari, A. (2013). A review on Micro-PIV Applications (ed.). Paper presented at International Tribology Symposium of IFToMM : 19/03/2013 - 21/03/2013. Paper presented at International Tribology Symposium of IFToMM : 19/03/2013 - 21/03/2013.
Open this publication in new window or tab >>A review on Micro-PIV Applications
2013 (English)Conference paper, Oral presentation only (Refereed)
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-39847 (URN)ebe8c041-e75c-44b8-943d-bb8e33e63244 (Local ID)ebe8c041-e75c-44b8-943d-bb8e33e63244 (Archive number)ebe8c041-e75c-44b8-943d-bb8e33e63244 (OAI)
Conference
International Tribology Symposium of IFToMM : 19/03/2013 - 21/03/2013
Note
Godkänd; 2013; 20130521 (ysko)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2018-01-14Bibliographically approved
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