Optimal parameters of abrasive flow finishing for hip joint implants

2021 ◽  
pp. 095440542199561
Author(s):  
Yahya Choopani ◽  
Mohsen Khajehzadeh ◽  
Mohammad Reza Razfar
Keyword(s):  
Surface Roughness ◽  
Standard Deviation ◽  
Femoral Head ◽  
Hip Joint ◽  
Spherical Shape ◽  
Shape Deviation ◽  
Head Surface ◽  
Joint Implants ◽  
Finishing Processes ◽  
Abrasive Flow Finishing

Total hip arthroplasty (THA) is one of the most well-known orthopedic surgeries in the world which involves the substitution of the natural hip joint by prostheses. In this process, the surface roughness of the femoral head plays a pivotal role in the performance of hip joint implants. In this regard, the nano-finishing of the femoral head of the hip joint implants to achieve a uniform surface roughness with the lowest standard deviation is a major challenge in the conventional and advanced finishing processes. In the present study, the inverse replica fixture technique was used for automatic finishing in the abrasive flow finishing (AFF) process. For this aim, an experimental setup of the AFF process was designed and fabricated. After the tests, experimental data were modeled and optimized to achieve the minimum surface roughness in the ASTM F138 (SS 316L) femoral head of the hip joint through the use of response surface methodology (RSM). The results confirmed uniform surface roughness up to the range of 0.0203 µm with a minimum standard deviation of 0.00224 for the femoral head. Moreover, the spherical shape deviation of the femoral head was achieved in the range of 7 µm. The RSM results showed a 99.71% improvement in the femoral head surface roughness (0.0007) µm under the optimized condition involving the extrusion pressure of 9.10 MPa, the number of finishing cycles of 95, and SiC abrasive mesh number of 1000.

scholarly journals Novel Polishing Media for Finishing Hip Joint Implants

2021 ◽  
Author(s):  
Yahya Choopani ◽  
Mohsen Khajehzadeh ◽  
Mohammad Reza Razfar
Keyword(s):  
Surface Roughness ◽  
Femoral Head ◽  
Hip Joint ◽  
Substantial Reduction ◽  
Sisal Fiber ◽  
Future Application ◽  
Finishing Process ◽  
Joint Implants ◽  
Optimized Conditions ◽  
Influential Parameters

Abstract Automating the finishing process of the femoral head in hip joint implants is one of the greatest concerns in industrial and academic societies. To achieve this goal, first, a negative replica is developed for the femoral head in the abrasive flow finishing (AFF) process. Then, a novel polishing media by combining the viscoelastic carrier and coarse sisal fiber is proposed for finishing. Finally, the performance of the finishing procedure through the proposed polishing media is assessed experimentally by evaluating the influential parameters of the AFF process on the surface roughness of the femoral head, which is made from ASTM F138 (SS 316L). Experimental results prove the effectiveness of the proposed polishing media in negative replica for finishing of femoral head owing to the severe mechanical disintegration. This is validated with the substantial reduction of surface roughness in the femoral head from 134.6 nm to 36.96 nm. Furthermore, AFM results confirm the improved surface topography parameters of Ra, Rq, and Rt in the femoral head under optimized conditions by 72.54%, 70.50%, and 64.79%, respectively. Generally, it can be said that promising results for future application of the polishing media in the AFF process are obtained.

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

2019 ◽  
Vol 234 (3) ◽  
pp. 355-370 ◽  
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.

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

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.

Effect of Head Surface Roughness and Sterilization Method on Wear of UHMWPE Acetabular Cups: Preliminary Hip Joint Simulator Results

2006 ◽  
Author(s):  
Anneli Jedenmalm ◽  
Walther Leardini ◽  
Mara Zavalloni ◽  
Saverio Affatato
Keyword(s):  
Surface Roughness ◽  
Hip Joint ◽  
Calf Serum ◽  
The Body ◽  
Acetabular Cup ◽  
Sterilization Method ◽  
Metal Head ◽  
Head Surface ◽  
The Impact ◽  
Hip Joint Simulator

More than one million hip joint replacements are performed each year in the world. However, the implants do not last forever due to material limitations, even though the operation is successful. The most common material combination used today is a CoCr head articulating against an UHMWPE (Ultra High Molecular Weight Polyethylene) acetabular cup. Several investigations have shown that the metal head is roughened inside the body and thus accelerating wear of the polymer cup. The sterilization method is also known to have effect on the wear properties. In vitro wear tests are however usually performed with as new implants. This investigation aimed at study the impact of head surface roughness on wear of both sterilized and non-sterilized acetabular cups. A total of nine acetabular cup and head pairs were wear tested in a hip joint simulator for 2Million cycles (Mc) with bovine calf serum as lubricant. Wear was determined by weighing of all cups. The heads were of CoCrMo and the average initial head surface roughness was 15nm (Ra), measured with a white light interference profilometer. The roughening was produced with a SiC paper producing circular multidirectional wear tracks to a surface roughness of about 400nm (Ra). The cups were of UHMWPE and the sterilized cups were 3Mrad gamma-radiated in nitrogen. The surface roughness after wear test was unchanged for the roughened heads, while the initially smooth heads were slightly roughened. Preliminary results show that the rough heads increase the wear of the cups 2-fold. The γ-irradiation affected both wear- and soak rate.

Experimental, Theoretical, and Simulation Comparative Study of Nano Surface Roughness Generated During Abrasive Flow Finishing Process

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Sachin Singh ◽  
Deepu Kumar ◽  
Mamilla Ravi Sankar
Keyword(s):  
Surface Roughness ◽  
Aluminum Alloy ◽  
Aluminum Alloys ◽  
Simulation Model ◽  
Abrasive Particle ◽  
Complex Surface ◽  
Abrasive Medium ◽  
Finishing Process ◽  
Finishing Processes ◽  
Abrasive Flow Finishing

Abrasive flow finishing (AFF) is one of the advanced finishing processes used mainly for finishing of complex surface features. Nano finishing of aluminum alloys is difficult using conventional finishing processes because of its soft nature. So, in this work, aluminum alloys are finished using AFF process. Since the finishing is carried out using polymer rheological abrasive medium (medium), the finishing forces on aluminum alloy workpieces are too low compared to conventional finishing processes. Thus, this process generates nano surface roughness on aluminum alloy. By using the theoretical model, change in surface roughness (ΔRa) with respect to various AFF input parameters is studied. A new simulation model is proposed in this paper to predict the finishing forces and ΔRa during AFF process. Modeling of finishing forces generated during the AFF process is carried out using ansys polyflow. These forces are used as input in the simulation model to predict ΔRa. Medium rheology decides the magnitude of the generated finishing forces in AFF process. Therefore, to predict the forces accurately, rheological properties of the medium are measured experimentally and used as input during modeling. Further, to make the simulation more realistic, abrasive particle bluntness with respect to extrusion pressure and number of strokes is considered. Because of considering these realistic conditions, simulation and experimental results are in better agreement compared to theoretical results.

Nonsphericity of Bearing Geometry and Lubrication in Hip Joint Implants

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
F. C. Wang ◽  
S. X. Zhao ◽  
A. Félix Quiñonez ◽  
H. Xu ◽  
X. S. Mei ◽  
...  
Keyword(s):  
Femoral Head ◽  
Hip Joint ◽  
Spherical Surface ◽  
Elastohydrodynamic Lubrication ◽  
Acetabular Cup ◽  
Surface Geometry ◽  
Spherical Coordinate ◽  
Transient Conditions ◽  
Convolution Model ◽  
Joint Implants

A general elastohydrodynamic lubrication model was developed to consider the nonsphericity of the bearing geometry in hip joint implants, both under the steady and transient conditions. The articulation between the femoral head and the acetabular cup was represented by a nominal ball-in-socket configuration. The nonsphericity was introduced on the acetabular cup and femoral head bearing surfaces in the form of an ellipsoidal surface represented by variations of the radii of curvature given by the three semi-axis lengths of the ellipsoid with regard to a nominal spherical surface. An appropriate spherical coordinate system and solution domain discretization were used to facilitate the numerical simulations. Both the equivalent discrete spherical convolution model and the corresponding spherical fast Fourier transform technique were used to evaluate the elastic deformation of either the spherical or nonspherical bearing surfaces. A fixed-tracked method was also developed to simulate the complex morphology introduced by moving the interface of the nonspherical bearing surfaces. The general methodology for the nonspherical bearing was first applied to investigate the steady-state elastohydrodynamic lubrication of an ellipsoidal cup articulating against a spherical head in a typical metal-on-metal hip joint implant. Subsequently, the problem of an ellipsoidal head articulating against a spherical cup was considered under the transient conditions. The significance of nonsphericity of bearing geometry in hip joint implants due to manufacturing, designing, and wear was discussed. The results obtained showed that the effect of a nonspherical bearing surface geometry on elastohydrodynamic lubrication was dependent on the orientation, the magnitude, and the deviation direction of the nonsphericity. A well-controlled nonsphericity was seen to be beneficial for improving the lubrication.

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