The Experts below are selected from a list of 14040 Experts worldwide ranked by ideXlab platform
Yuelin Wang - One of the best experts on this subject based on the ideXlab platform.
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squeeze film air damping of thick Hole Plate
Sensors and Actuators A-physical, 2003Co-Authors: Minhang Bao, Heng Yang, Yuancheng Sun, Yuelin WangAbstract:Abstract The damping effect of air flow in Holes is considered based on Poiseuille equation and the damping effect of lateral flow is considered by conventional Reynolds’ equation for infinite thick Hole-Plate. The expression for damping ratio is obtained and the conditions for minimum damping ratio can be found. A modified Reynolds’ equation is established for thick Hole-Plate with finite dimensions. The equation is a good approximation for Hole-Plates in typical MEMS devices. As it is also effective for non-Hole-Plate as well, it is more general than the conventional Reynolds’ equation. The distribution of damping pressure under a Hole-Plate can be found by solving the modified Reynolds’ equation with appropriate boundary conditions. As an example, the damping pressure of squeeze-film air damping of a long rectangular Hole-Plate is considered. Analytical expressions for the damping pressure, damping force and damping ratio are found.
J. S. Kawalec - One of the best experts on this subject based on the ideXlab platform.
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mixed metal fretting corrosion of ti6al4v and wrought cobalt alloy
Journal of Biomedical Materials Research, 1995Co-Authors: J. S. Kawalec, Joe H. Payer, Stanley A Brown, Katharine MerrittAbstract:Corrosion has been reported at the modular interfaces of total joint replacement implants, but with conflicting theories as to the cause of such damage. The modular design itself leaves the interface susceptible to galvanic, crevice, or fretting corrosion, or a combination of the three. The purpose of this study was to quantify the effect of material combination on fretting corrosion of orthopedic alloys. Each test specimen consisted of a two-Hole Plate with spherical countersinks of a two cortical bone screws. The Plates and screws were made of either Ti6Al4V or wrought cobalt–chromium–molybdenum (CCM), and were tested in all mixed-metal and similar-alloy combinations. Fretting corrosion experiments were conducted for 14 days in 10% calf serum, according to ASTM F897. Corrosion damage was evaluated by weight-loss measurements, atomic absorption spectrophotometry and scanning electron microscopy analyses. The results indicated that Ti6Al4V suffered relatively severe damage when fretted against itself, as a result of adhesive galling. The extent of titanium damage was reduced considerably, however, when Ti6Al4V was fretted against wrought CCM. In contrast, there was essentially no difference in wrought CCM damage when the alloy was fretted against itself compared to fretting against Ti6Al4V. Finally, in similar-alloy combinations, Ti6Al4V suffered more severe damage than wrought CCM. © 1995 John Wiley & Sons, Inc.
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reduction of fretting corrosion of ti 6al 4v by various surface treatments
Journal of Orthopaedic Research, 1993Co-Authors: Anne M. Maurer, Joe H. Payer, Stanley A Brown, Katharine Merritt, J. S. KawalecAbstract:Titanium and titanium-6% aluminum-4% vanadium (Ti-6Al-4V) are known to be biocompatible and corrosion resistant. However, there have been numerous reports of elevated tissue levels of titanium due to passive dissolution, wear, or fretting corrosion of implants. Studies were undertaken to determine whether the fretting corrosion of Ti-6Al-4V could be reduced by surface treatment of one or both surfaces in a fretting situation. Three different surface treatments were studied: ion implantation, physical vapor deposition nitriding, and plasma ion nitriding. The specimens used were screws fretting against the countersinks of a two-Hole Plate. Fretting corrosion was assessed by weight loss, by chemical analysis of test solutions, and by scanning electron microscopy. Surface treatment of one component, the screws, resulted in reduction in the release of titanium to only 18–32% of that seen with the untreated controls. Weight loss of the untreated Plates fretted against physical vapor deposition nitrided screws and plasma ion nitrided screws was reduced to 31 and 38% of the control, respectively. The weight loss of plasma nitrided screws was only 30% that of the control. Nitriding of both Plates and screws resulted in a further decrease in Plate weight loss and metal release. Plasma ion nitriding of both components had the most significant effect, with the weight loss and titanium release being only 11 and 2% of the control values, respectively.
Minhang Bao - One of the best experts on this subject based on the ideXlab platform.
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squeeze film air damping of thick Hole Plate
Sensors and Actuators A-physical, 2003Co-Authors: Minhang Bao, Heng Yang, Yuancheng Sun, Yuelin WangAbstract:Abstract The damping effect of air flow in Holes is considered based on Poiseuille equation and the damping effect of lateral flow is considered by conventional Reynolds’ equation for infinite thick Hole-Plate. The expression for damping ratio is obtained and the conditions for minimum damping ratio can be found. A modified Reynolds’ equation is established for thick Hole-Plate with finite dimensions. The equation is a good approximation for Hole-Plates in typical MEMS devices. As it is also effective for non-Hole-Plate as well, it is more general than the conventional Reynolds’ equation. The distribution of damping pressure under a Hole-Plate can be found by solving the modified Reynolds’ equation with appropriate boundary conditions. As an example, the damping pressure of squeeze-film air damping of a long rectangular Hole-Plate is considered. Analytical expressions for the damping pressure, damping force and damping ratio are found.
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modified reynolds equation and analytical analysis of squeeze film air damping of perforated structures
Journal of Micromechanics and Microengineering, 2003Co-Authors: Minhang Bao, Heng Yang, Yuancheng Sun, Paddy J FrenchAbstract:We modified the Reynolds equation to extend its applications to squeeze-film air damping of perforated Plates (i.e., the Hole-Plates) by adding a term related to the damping effect of gas flow through Holes. The modified Reynolds equation (MRE) is generally effective for a perforated Hole-Plate with a finite thickness and finite lateral dimensions as well as a non-perforated Hole-Plate. Analytical expressions of damping pressure for long rectangular Hole-Plates and regular rectangular Hole-Plates have been found. For MEMS devices with typical dimensions, 'effective damping width' approximation is introduced so that the boundary effect on damping force can be treated easily. The conditions for 'effective damping width' approximation are discussed. Based on the concept of 'effective damping width', damping forces for circular Plates and even Hole-Plates with irregular shapes can be found. The results obtained by the MRE method match the numerical results obtained by ANSYS/FLOTRAN very well. The comparison between the MRE results and the experimental results by Kim et al (1999 MEMS '99 pp 296–301) shows that the MRE results agree with the experimental results much better than the FEM simulation given by Kim et al.
Katharine Merritt - One of the best experts on this subject based on the ideXlab platform.
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mixed metal fretting corrosion of ti6al4v and wrought cobalt alloy
Journal of Biomedical Materials Research, 1995Co-Authors: J. S. Kawalec, Joe H. Payer, Stanley A Brown, Katharine MerrittAbstract:Corrosion has been reported at the modular interfaces of total joint replacement implants, but with conflicting theories as to the cause of such damage. The modular design itself leaves the interface susceptible to galvanic, crevice, or fretting corrosion, or a combination of the three. The purpose of this study was to quantify the effect of material combination on fretting corrosion of orthopedic alloys. Each test specimen consisted of a two-Hole Plate with spherical countersinks of a two cortical bone screws. The Plates and screws were made of either Ti6Al4V or wrought cobalt–chromium–molybdenum (CCM), and were tested in all mixed-metal and similar-alloy combinations. Fretting corrosion experiments were conducted for 14 days in 10% calf serum, according to ASTM F897. Corrosion damage was evaluated by weight-loss measurements, atomic absorption spectrophotometry and scanning electron microscopy analyses. The results indicated that Ti6Al4V suffered relatively severe damage when fretted against itself, as a result of adhesive galling. The extent of titanium damage was reduced considerably, however, when Ti6Al4V was fretted against wrought CCM. In contrast, there was essentially no difference in wrought CCM damage when the alloy was fretted against itself compared to fretting against Ti6Al4V. Finally, in similar-alloy combinations, Ti6Al4V suffered more severe damage than wrought CCM. © 1995 John Wiley & Sons, Inc.
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reduction of fretting corrosion of ti 6al 4v by various surface treatments
Journal of Orthopaedic Research, 1993Co-Authors: Anne M. Maurer, Joe H. Payer, Stanley A Brown, Katharine Merritt, J. S. KawalecAbstract:Titanium and titanium-6% aluminum-4% vanadium (Ti-6Al-4V) are known to be biocompatible and corrosion resistant. However, there have been numerous reports of elevated tissue levels of titanium due to passive dissolution, wear, or fretting corrosion of implants. Studies were undertaken to determine whether the fretting corrosion of Ti-6Al-4V could be reduced by surface treatment of one or both surfaces in a fretting situation. Three different surface treatments were studied: ion implantation, physical vapor deposition nitriding, and plasma ion nitriding. The specimens used were screws fretting against the countersinks of a two-Hole Plate. Fretting corrosion was assessed by weight loss, by chemical analysis of test solutions, and by scanning electron microscopy. Surface treatment of one component, the screws, resulted in reduction in the release of titanium to only 18–32% of that seen with the untreated controls. Weight loss of the untreated Plates fretted against physical vapor deposition nitrided screws and plasma ion nitrided screws was reduced to 31 and 38% of the control, respectively. The weight loss of plasma nitrided screws was only 30% that of the control. Nitriding of both Plates and screws resulted in a further decrease in Plate weight loss and metal release. Plasma ion nitriding of both components had the most significant effect, with the weight loss and titanium release being only 11 and 2% of the control values, respectively.
S Nayagam - One of the best experts on this subject based on the ideXlab platform.
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correcting genu varum and genu valgum in children by guided growth temporary hemiepiphysiodesis using tension band Plates
Journal of Bone and Joint Surgery-british Volume, 2010Co-Authors: M S Ballal, C E Bruce, S NayagamAbstract:A total of 25 children (37 legs and 51 segments) with coronal plane deformities around the knee were treated with the extraperiosteal application of a flexible two-Hole Plate and screws. The mean age was 11.6 years (5.5 to 14.9), the median angle of deformity treated was 8.3 degrees and mean time for correction was 16.1 months (7 to 37.3). There was a mean rate of correction of 0.7 degrees per month in the femur (0.3 degrees to 1.5 degrees ), 0.5 degrees per month in the tibia (0.1 degrees to 0.9 degrees ) and 1.2 degrees per month (0.1 degrees to 2.2 degrees ) if femur and tibia were treated concurrently. Correction was faster if the child was under 10 years of age (p = 0.05). The patients were reviewed between six and 32 months after Plate removal. One child had a rebound deformity but no permanent physeal tethers were encountered. The guided growth technique, as performed using a flexible titanium Plate, is simple and safe for treating periarticular deformities of the leg.