Nanofinishing of Microslots on Surgical Stainless Steel by Abrasive Flow Finishing Process: Experimentation and Modeling

Miniaturization of components is one of the major demands of the today's technological advancement. Microslots are one of the widely used microfeature found in various industries such as automobile, aerospace, fuel cells and medical. Surface roughness of the microslots plays critical role in high precision applications such as medical field (e.g., drug eluting stent and microfilters). In this paper, abrasive flow finishing (AFF) process is used for finishing of the microslots (width 450 μm) on surgical stainless steel workpiece that are fabricated by electrical discharge micromachining (EDμM). AFF medium is developed in-house and used for performing microslots finishing experiments. Developed medium not only helps in the removal of hard recast layer from the workpiece surfaces but also provides nano surface roughness. Parametric study of microslots finishing by AFF process is carried out with the help of central composite rotatable design (CCRD) method. The initial surface roughness on the microslots wall is in the range of 3.50 ± 0.10 μm. After AFF, the surface roughness is reduced to 192 nm with a 94.56% improvement in the surface roughness. To understand physics of the AFF process, three-dimensional (3D) finite element (FE) viscoelastic model of the AFF process is developed. Later, a surface roughness simulation model is also proposed to predict the final surface roughness after the AFF process. Simulated results are in good agreement with the experimental results.

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Development of polymer abrasive medium for nanofinishing of microholes on surgical stainless steel using abrasive flow finishing process

Proceedings of the Institution of Mechanical Engineers Part B Journal of Engineering Manufacture ◽

10.1177/0954405419883768 ◽

2019 ◽

Vol 234 (3) ◽

pp. 355-370 ◽

Cited By ~ 1

Author(s):

Sachin Singh ◽

M Ravi Sankar

Keyword(s):

Surface Roughness ◽

Stainless Steel ◽

High Surface ◽

Machining Process ◽

Abrasive Medium ◽

Finishing Process ◽

Drug Eluting ◽

Finishing Processes ◽

Abrasive Flow Finishing

The finishing operation completes the manufacturing cycle of a component. Depending on the level of finish (micro and nano) required on the component surface, different finishing processes are employed. Several components employed in medical, automotive and chemical industries use different types of passages for the flow of fluid. The surface roughness of such passages decides the functionality of the component. Drug-eluting stents are one of the recent advancements in the medical industry. They possess microholes for release of the drugs to the point of cure. Microholes are mostly fabricated by thermal-based micromachining processes that generate metallurgically destroyed surface layers with high surface roughness. Later, these are polished using chemical or electrochemical polishing techniques, which chemically destroy the quality of the surface. These metallurgically and chemically modified (destroyed/changed) rough surfaces on the microhole wall can cause contamination of the drug. So in this article, microholes of diameter 850 ± 30 µm are fabricated in surgical stainless steel (SS 316L) workpieces using the electric discharge micromachining process. Machined microholes are finished by employing a non-traditional finishing process called the abrasive flow finishing process. Instead of using a commercially available expensive abrasive flow finishing medium, the economic medium is fabricated in-house, and its rheological study is carried out. Machining process produces microholes with a surface roughness of about 1.40 ± 0.10 µm. Later, by finishing of microholes with the abrasive flow finishing process, the surface roughness is reduced to 150 nm (percentage surface roughness improvement of about 88.53%). Therefore, the abrasive flow finishing process is a viable alternative to chemical-based polishing processes as it removes the recast layer and achieves nanosurface roughness.

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Neoatherosclerosis after Drug-Eluting Stent Implantation: Roles and Mechanisms

Oxidative Medicine and Cellular Longevity ◽

10.1155/2016/5924234 ◽

2016 ◽

Vol 2016 ◽

pp. 1-11 ◽

Cited By ~ 3

Author(s):

Yuanyuan Cui ◽

Yue Liu ◽

Fuhai Zhao ◽

Dazhuo Shi ◽

Keji Chen

Keyword(s):

First Generation ◽

Critical Role ◽

Late Complications ◽

Drug Eluting Stent ◽

Late Stent Thrombosis ◽

Fibrous Cap ◽

Close Relationship ◽

Drug Eluting ◽

Improve Clinical Outcome

In-stent neoatherosclerosis (NA), characterized by a relatively thin fibrous cap and large volume of yellow-lipid accumulation after drug-eluting stents (DES) implantation, has attracted much attention owing to its close relationship with late complications, such as revascularization and late stent thrombosis (ST). Accumulating evidence has demonstrated that more than one-third of patients with first-generation DES present with NA. Even in the advent of second-generation DES, NA still occurs. It is indicated that endothelial dysfunction induced by DES plays a critical role in neoatherosclerotic development. Upregulation of reactive oxygen species (ROS) induced by DES implantation significantly affects endothelial cells healing and functioning, therefore rendering NA formation. In light of the role of ROS in suppression of endothelial healing, combining antioxidant therapies with stenting technology may facilitate reestablishing a functioning endothelium to improve clinical outcome for patients with stenting.

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Yield and shear of rough interlocked faults: analytical solution and experimental observations

10.5194/egusphere-egu2020-2565 ◽

2020 ◽

Author(s):

Amir Sagy ◽

Vladimir Lyakhovsky ◽

Yossef H. Hatzor

Keyword(s):

Surface Roughness ◽

Analytical Solution ◽

Normal Stress ◽

Laboratory Experiments ◽

Three Dimensional ◽

Elastic Half Space ◽

Interface Roughness ◽

Displacement Rate ◽

Initial Surface ◽

Surface Geometry

Natural fault surfaces are interlocked, partly cohesive, and display multiscale geometric irregularities. Here we examine the nucleation of deformation and the evolution of shear in such interlocked surfaces using a closed-form analytical solution and a series of laboratory experiments. &#160;The analytical model considers an interlocked interface with multiscale roughness between two linear elastic half-space blocks. The interface geometry is based on three-dimensional fault surfaces imaging. It is represented by a Fourier series and the plane strain solution for the elastic stress distribution is represented as a sum of the constant background stress generated by a uniform far-field loading and perturbations associated with the interface roughness. The model predicts the critical stress necessary for failure and the location of failure nucleation sites across the surface, as function of the initial surface geometry.A similar configuration is adopted in laboratory experiments as carbonate blocks with rough interlocked surfaces generated by tensional fracturing are sheared in a servo-controlled direct shear apparatus. Resistance to shear and surface roughness evolution are measured under variable normal stresses, slip distances and slip rates.&#160; We find that the evolution of surface morphology with shear is closely related to the loading configuration. Initially rough, interlocked, surfaces become rougher when normal stress and displacement rate are increased. Under a fixed, relatively low normal stress and fixed displacement rate however, the surfaces become smoother with increasing displacement distance. &#160;The shear of the interlocked slip surfaces is associated with volumetric deformation, wear and frictional slip, all of which are typically observed across natural fault zones. We suggest that their intensities and partitioning are strongly affected by the initial surface roughness characteristics, the background stress, and the rate and magnitude of shear displacement.&#160;

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Development and Rheological Characterisation of Abrasive Flow Finishing Medium for Finishing Macro to Micro Features

Defence Science Journal ◽

10.14429/dsj.70.14790 ◽

2020 ◽

Vol 70 (2) ◽

pp. 190-196

Author(s):

Sachin Singh ◽

M. Ravi Sankar

Keyword(s):

Surface Roughness ◽

Surface Finish ◽

Recast Layer ◽

Technological Advancement ◽

Minimal Cost ◽

Finishing Process ◽

Fine Surface ◽

Micro Features ◽

Finishing Processes ◽

Abrasive Flow Finishing

Technological advancement demands the manufacturing of components with a fine surface finish at a minimal cost. This scenario acts as the driving force for the research communities to develop economic finishing processes. Abrasive flow finishing (AFF) is one of the advanced finishing processes employed for finishing, deburring, radiusing and recast layer removal from the workpiece surfaces. AFF process uses a finishing medium that acts as a deformable tool during the finishing process. It is the rheological properties of the medium that profoundly influences the end surface finish obtained on the workpiece after the AFF process. In the current work, an attempt is made to develop an economic AFF medium by using viscoelastic polymers i.e., soft styrene and soft silicone polymer. Detailed static and dynamic characterisation of the medium is carried out. Later, to study the finishing performance of the developed medium, AFF experiments are performed for the finishing of macro and micro feature components. The experimental study showed that the nano surface finish could be achieved by varying the viscosity of the developed medium. Developed medium achieved 89.06 per cent improvement in surface roughness during finishing of tubes (macro feature component), while 92.13 per cent and 88.11 per cent surface roughness improvement is achieved during finishing of microslots and microholes (micro feature component), respectively.

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Quantitative analysis of mechanically retentive ceramic bracket base surfaces with a three-dimensional imaging system

The Angle Orthodontist ◽

10.2319/100412-782.1 ◽

2012 ◽

Vol 83 (4) ◽

pp. 705-711 ◽

Cited By ~ 5

Author(s):

Da-Young Kang ◽

Sung-Hwan Choi ◽

Jung-Yul Cha ◽

Chung-Ju Hwang

Keyword(s):

Surface Roughness ◽

Stainless Steel ◽

Surface Area ◽

Three Dimensional ◽

Micro Ct ◽

Base Surface ◽

Surface Areas ◽

Ceramic Brackets ◽

Ceramic Bracket ◽

Bracket Base

ABSTRACT Objective: To investigate the three-dimensional structural features of three types of mechanically retentive ceramic bracket bases. Materials and Methods: One type of stainless steel (MicroArch, Tomy, Tokyo, Japan) and three types of ceramic maxillary right central incisor brackets—Crystaline MB (Tomy), INVU (TP Orthodontics, La Porte, Ind), and Inspire Ice (Ormco, Glendora, Calif)—were tested to compare and quantitatively analyze differences in the surface features of each ceramic bracket base using scanning electron microscopy (SEM), a three-dimensional (3D) optical surface profiler, and microcomputed tomography (micro-CT). One-way analysis of variance was used to find differences in bracket base surface roughness values and surface areas between groups according to base designs. Tukey's honestly significant differences tests were used for post hoc comparisons. Results: SEM revealed that each bracket exhibited a unique surface texture (MicroArch, double mesh; Crystaline MB, irregular; INVU, single mesh; Inspire Ice, bead ball). With a 3D optical surface profiler, the stainless steel bracket showed significantly higher surface roughness values. Crystaline MB had significantly higher surface roughness values than Inspire Ice. Micro-CT demonstrated that stainless steel brackets showed significantly higher whole and unit bracket base surface areas. Among ceramic brackets, INVU showed significantly higher whole bracket base surface area, and Crystaline MB showed a significantly higher unit bracket base surface area than Inspire Ice. Conclusion: Irregular bracket surface features showed the highest surface roughness values and unit bracket base surface area among ceramic brackets, which contributes to increased mechanically retentive bracket bonding strength.

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Surface roughness of three types of modern plastic bracket slot floors and frictional resistance

The Angle Orthodontist ◽

10.2319/030313-179.1 ◽

2013 ◽

Vol 84 (1) ◽

pp. 177-183 ◽

Cited By ~ 8

Author(s):

Sung-Hwan Choi ◽

Da-Young Kang ◽

Chung–Ju Hwang

Keyword(s):

Surface Roughness ◽

Stainless Steel ◽

Three Dimensional ◽

Frictional Resistance ◽

Lower Surface ◽

Reinforced Plastic ◽

Ceramic Brackets ◽

Sliding Test ◽

Plastic Brackets

ABSTRACT Objective: To quantitatively analyze the surface roughness of the slot floors of three types of modern plastic brackets and to measure static frictional force during sliding mechanics in vitro. Materials and Methods: Control groups comprised stainless steel brackets and monocrystalline ceramic brackets. Test groups comprised three types of 0.022-in slot, Roth prescription, plastic, maxillary right central incisor brackets. Test groups included glass fiber-reinforced polycarbonate, filler-reinforced polycarbonate, and hybrid polymer with inserted metal slot brackets. The static frictional resistance caused by sliding movements with an archwire (stainless steel) in vitro was quantitatively analyzed. Both scanning electron microscope and three-dimensional optical surface profiling were used. Results: Scanning electron microscope and three-dimensional optical surface profiler revealed that all as-received brackets had irregular slot floor surfaces, and both irregularity and roughness increased after the archwire sliding test. The ceramic brackets in the control group showed significantly lower surface roughness values and higher frictional values during the archwire sliding test compared with the other brackets. The glass or filler-reinforced plastic brackets exhibited significantly higher static frictional values than the metallic slot type brackets (P < .001). The hybrid polymer with inserted metal slot brackets showed relatively lower surface roughness and frictional values compared with the stainless steel control bracket. Conclusion: Glass or filler-reinforced plastic brackets showed higher frictional resistance than metallic slot–type brackets. A plastic bracket with inserted metal slot may be the best choice among plastic brackets for low frictional resistance and to avoid damage from sliding movements of the archwire.

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Multi-Objective Optimization of Magneto Rheological Abrasive Flow Nano Finishing Process on AISI Stainless Steel 316L

Journal of Nano Research ◽

10.4028/www.scientific.net/jnanor.63.98 ◽

2020 ◽

Vol 63 ◽

pp. 98-111

Author(s):

S. Kathiresan ◽

B. Mohan

Keyword(s):

Surface Roughness ◽

Stainless Steel ◽

Initial Surface ◽

Multi Objective Optimization ◽

Stainless Steel 316L ◽

Volume Percentage ◽

Multi Objective ◽

Input Variables ◽

Number Of Cycles ◽

Magneto Rheological

In this experimental work, Magneto rheological abrasive flow nano finishing processes were conducted on AISI Stainless steel 316L work pieces that are widely used in medical implants. The focus of the present study is to assess the effect of input variables namely the volume percentage of iron (Fe) particles, silicon carbide (SiC) abrasive particles in the Magneto rheological abrasive fluid and number of cycles on the final surface roughness at nano level as well as the material removal rate. The volume % of Fe particles were taken as 20, 25 and 30 and the volume % of SiC particles were taken as 10, 15 and 20. The different number of cycles considered for the study is 100,200 and 300. There are 20 different set of experiments with different combinations of input variables mentioned have been carried out based on the experimental design derived through central composite design technique. The minimum surface roughness observed is 23.34 nanometer (nm) from the initial surface roughness of 1.92 micro meter (µm). Towards optimizing the input process variables, a multi objective optimization was carried out by using response surface methodology.

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Platinum Chromium Stent Series – The TAXUS™ Element™ (ION™), PROMUS Element™ and OMEGA™ Stents

Interventional Cardiology Review ◽

10.15420/icr.2011.6.2.134 ◽

2011 ◽

Vol 6 (2) ◽

pp. 134 ◽

Cited By ~ 8

Author(s):

Dominic J Allocco ◽

Mary V Jacoski ◽

Barbara Huibregtse ◽

Tim Mickley ◽

Keith D Dawkins ◽

...

Keyword(s):

Stainless Steel ◽

316L Stainless Steel ◽

Coronary Intervention ◽

Development Programme ◽

Drug Eluting Stent ◽

Cobalt Chromium ◽

Key Points ◽

Percutaneous Coronary ◽

Radial Strength ◽

Drug Eluting

Advances in drug-eluting stent technology have continued to improve clinical outcomes for patients undergoing percutaneous coronary intervention (PCI). The Boston Scientific stent platform has evolved from the 316L stainless steel Express™ stent, to the 316L stainless steel Liberté™ stent, to the cobalt–chromium PROMUS™ stent and, finally, to the platinum–chromium (PtCr) stent series. The PtCr platform, which uses the Element architecture, is designed to have improved deliverability, radiopacity, radial strength and recoil resistance compared with existing stainless steel or cobalt–chromium stents. This review discusses the key points in Boston Scientific’s development programme, which has culminated in the newest generation of coronary stent systems: the PtCr bare-metal OMEGA™ stent, the PtCr paclitaxel-eluting TAXUS Element™ (ION™) stent and the PtCr everolimus-eluting PROMUS Element™ stent systems.

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