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.
Ultrasonic-assisted magnetic abrasive finishing (UAMAF) process has been developed to reduce the finishing time of hard materials. In this process, in addition to the rotation of the magnetic tool, ultrasonic vibrations are also applied to the workpiece simultaneously in the longitudinal direction. In the present work, the effects of UAMAF process parameters, including ultrasonic power, the rotational speed of the magnetic tool, working gap, and weight of magnetic abrasive particles (MAPs) on the percentage change in surface roughness (%ΔRa) of 1.2738 tool steel are discussed with an experimental approach. In this regard, besides the development of the UAMAF process, the sintering of MAPs with glass powder is proposed. The experiments are designed according to the Taguchi method. Then, the input parameters of the UAMAF process are modeled and optimized using the signal-to-noise (S/N) ratio analysis to achieve the maximum %ΔRa. Statistical analysis of experimental data shows that the most significant contribution in improving %ΔRa is attributed to the weight of MAPs. Furthermore, according to the comparative study, %ΔRa in the UAMAF process for finishing the DIN 1.2738 tool steel is improved by 86.62% under optimized conditions. In comparison, this value in the MAF process is equal to 48.62% under the same conditions. The results of the surface morphology also underline that abrasive particles in the UAMAF process hit the peaks of the surface roughness due to vibration applied to the workpiece, which leads to a high-quality finished surface.
Aluminum alloy 2024 (Al2024) tubes have extensive applications in the aerospace industry; however, finishing their interior surfaces is a big challenge. In this case, many traditional and advanced machining processes are inefficient due to the limitations of machining tools. To overcome these challenges and limitations, rotational-magnetorheological abrasive flow finishing (R-MRAFF) process has been proposed. In this process, magnetorheological polishing (MRP) fluid, experiences a rotational motion in addition to the reciprocating motion on the workpiece surface asperities. In the present work, the effect of the R-MRAFF processing time on the internal finishing of Al2024 tubes has been investigated experimentally in terms of two essential parameters; surface roughness and material removal. In this regard, an industrial prototype of the R-MRAFF process has been developed. Experimental results express the efficiency of the R-MRAFF process for nano-finishing of Al2024 tubes. The surface roughness and material removal values at a processing time of 15 min are 26.3 nm and 41 mg, respectively. In addition to the morphological observations, the surface topography results emphasize the removal of peaks by the R-MRAFF process, besides creating deep scratches with negative skewness on the surface texture of Al2024 tubes, which results in increased oil holding capacity.
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.
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