Percentage Of Contact Area Research Articles

Plantar Pressure Distribution Patterns of Individuals with Prediabetes in Comparison with Healthy Individuals and Individuals with Diabetes

Since elevated mechanical stress along with loss of plantar protective sensation are considered relevant factors in skin breakdown resulting in diabetic foot ulcerations, the assessment of plantar pressure is important for the prevention of diabetic foot complications. Prediabetes subjects are at risk of chronic hyperglycemia complications, among them neuropathy, but information about plantar loading in this population is not available. We aimed to compare baropodometric parameters of individuals with prediabetes versus healthy persons and persons with diabetes mellitus (DM). Baropodometric data from 73 subjects (15 with prediabetes (pre-DM), 28 with type 2 DM, 30 healthy) aged between 29 and 69 years of both genders were registered through a pressure platform with self-selected gait speed and first-step protocol. Peak plantar pressure, stance time, percentage of contact time, percentage of contact area and pressure-time integral were assessed in five plantar foot regions: heel, midfoot, metatarsals, hallux, and toes 2 to 5. Groups were compared by one-way analysis of variance with Scheffé post hoc (α = 0.05). Age, body mass index, gender, and arch height index did not differ between groups. Pre-DM and DM subjects presented increased peak pressure and pressure-time integral in metatarsals (p = .010; p > .001), as well as increased percentage of contact time in midfoot (p = .006) and metatarsals (p = .004) regions when compared with healthy subjects. Stance time was significantly higher (p = .017) in DM subjects. Pre-DM subjects seem to exhibit an altered plantar pressure distribution pattern similar to that often found in DM subjects.

Effect of lesser tuberosity osteotomy size and repair construct during total shoulder arthroplasty

Lesser tuberosity osteotomy has been shown to decrease postoperative subscapularis dysfunction. The purpose of this study was to determine the effect of osteotomy thickness and suture configuration on repair integrity. One side of 12 matched-pair cadaveric shoulders was randomly assigned to either a thick osteotomy (100% of lesser tuberosity height) or a thin osteotomy (50% of height). Both sides of the matched pairs were given the same repair, either (1) compression sutures or (2) compression sutures plus 1 tension suture. This created 4 groups of 6 paired specimens. Computed tomography imaging was used to measure tuberosity dimensions before and after osteotomy to validate fragment height and area. The repairs were loaded cyclically and then loaded to failure. A video system measured fragment displacement. The percent area of osteotomy contact was calculated from the computed tomography and displacement data. The average initial displacement was less in the thin osteotomy groups (P = .011). Adding a tension suture negated this difference. A significant number of thin repair sites compared with thick repair sites remained intact during load-to-failure testing (P = .001). No difference occurred because of maximum load between the repair groups (P = .401), and construct stiffness was greater when a tension suture was used (P = .032). The percent area of osteotomy contact showed no differences between the osteotomy (P = .431) and repair (P = .251) groups. The study showed that thin osteotomies displaced less than thick osteotomies. Adding a tension band improved construct stability and eliminated some failure modes. Our ideal repair was a thin wafer with both tension and compression sutures. This construct had smaller total displacement, a high osteotomy percent contact area, and a high maximum load.

Deterministic contact mechanics model applied to electrode interfaces in polymer electrolyte fuel cells and interfacial water accumulation

An elastic deterministic contact mechanics model is applied to the compressed micro-porous (MPL) and catalyst layer (CL) interfaces in polymer electrolyte fuel cells (PEFCs) to elucidate the interfacial morphology. The model employs measured two-dimensional surface profiles and computes local surface deformation and interfacial gap, average contact resistance, and percent contact area as a function of compression pressure. Here, we apply the model to one interface having a MPL with cracks and one with a crack-free MPL. The void size distributions and water retention curves for the two sets of CL|MPL interfaces under compression are also computed. The CL|MPL interfaces with cracks are observed to have higher roughness, resulting in twice the interfacial average gap compared to the non-cracked interface at a given level of compression. The results indicate that the interfacial contact resistance is roughly the same for cracked or non-cracked interfaces due to cracks occupying low percentage of overall area. However, the cracked CL|MPL interface yields higher liquid saturation levels at all capillary pressures, resulting in an order of magnitude higher water storage capacity compared to the smooth interface. The van Genuchten water retention curve correlation for log-normal void size distributions is found to fit non-cracked CL|MPL interfaces well.

Reducing subsidence risk by using rapid manufactured patient-specific intervertebral disc implants

Intervertebral disc implant size, shape, and position during total disc replacement have been shown to affect the risk of implant subsidence or vertebral fracture. Rapid manufacturing has been successfully applied to produce patient-specific implants for craniomaxillofacial, dental, hip, and knee requirements, but very little has been published on its application for spinal implants. This research was undertaken to investigate the improved load distribution and stiffness that can be achieved when using implants with matching bone interface geometry as opposed to implants with flat end plate geometries. The study design comprises a biomechanical investigation and comparison of compressive loads applied to cadaveric vertebrae when using two different end plate designs. Four spines from male cadavers (ages 45-65 years, average 52 years), which had a total of n=88 vertebrae (C3-L5), were considered during this study. Bone mineral density scans on each spine revealed only one to be eligible for this study. Twenty remaining vertebrae (C3-L3) were potted and subjected to nondestructive compression tests followed by destructive compression tests. Custom-made nonfunctional implants were designed for this experiment. Ten implants were designed with matching end plate-to-bone interface geometry, whereas the other 10 were designed with flat end plates. Testing did not incorporate the use of a keel in either design type. I-Scan pressure sensors (Tekscan, Inc., MA, USA) were used during the nondestructive tests to assess the load distribution and percentage surface contact. Average percent contact area measured during nondestructive tests was 45.27% and 10.49% for conformal and flat implants, respectively-a difference that is statistically significant (p<.001). A higher percent contact area was especially observed for cervical vertebrae because of their pronounced end plate concavity. During destructive compression tests, conformal implants achieved higher failure loads than flat implants. Conformal implants also performed significantly better when stiffness values were compared (p<.0001). One of the main expected benefits from customizing the end plate geometry of disc implants is the reduced risk and potential for subsidence into the vertebral bone end plate. Subsidence depends in part on the stiffness of the implant-bone construct, and with a 137% increase in stiffness, the results of this study show that there are indeed significant potential benefits that can be achieved through the use of customization during the design and manufacture of intervertebral disc implants.

Effect of Temperature on Pad Surface Contact Area in Chemical Mechanical Planarization

In this study, pad surface contact area measurement was performed using laser confocal microscopy at elevated temperatures under dry and static condition to illustrate the effect of temperature on the mechanical contacts in chemical mechanical planarization. Pad surface contact area and contact density were measured for a Cabot Microelectronics Corporation D100 pad sample at 27.6 kPa with a custom-made sample holder that was designed to heat the pad sample during the measurement. When the pad surface temperature increased from 25 to 45°C, pad asperities became much softer and resulted in a significant increase (from 0.029% to 0.092%) in the pad contact area percentage while the contact density remained in the same range.

Comparison of Initial Compression of the Medial, Lateral, and Posterior Screws in an Ankle Fusion Construct

One of the requirements for successful ankle arthrodesis is adequate compression by the fixation across the fusion surfaces. A common screw construct for ankle fusion is three crossed screws from proximal-to-distal. Because the screws are inserted nearly orthogonal to each other, it is possible minimal additional compression is obtainable once the first screw is inserted. The aim of this study was to determine which of the three screws gave the greatest initial compression and theoretically should be inserted first. Seventeen cadaver limbs were dissected to expose the anterior and posterior aspects of the tibiotalar joint. Three Fuji film templates were created for each ankle joint with a hole to accommodate a 7.0-mm cannulated screw. Each film was tested with a single medial, lateral, or posterior screw. The Fuji films were then analyzed for contact area, percent contact area, and pressure. There was no difference in the total contact area, percent contact area, or pressure generated between the three screws. The mean contact area for all screws was 11% of the joint surface. All three screws had greater contact area and percent contact area over the anterior half of the ankle joint. The medial, lateral, and posterior screws were equivalent with respect to contact area, percent contact area, and pressure generated across the tibiotalar joint. All three screws had greater contact area over the anterior half of the joint. Only 11% of the tibiotalar joint surface came in contact following the insertion of a single partially threaded screw. In a neutrally aligned ankle arthrodesis the order of screw insertion does not affect the amount of compression ultimately achieved at the fusion site.

Characterization and Modeling of Pad Asperity Response in CMP

AbstractA model is proposed to understand the interactions between CMP pad asperities and the wafer. Pad asperity reduced modulus and height distribution are included in the model. Physical measurements of asperity properties are performed: asperity reduced modulus is measured by nanoindentation, and pad asperity height distribution is scanned by profilometry. The measured results are used in the model to predict the contact area percentage between the pad and wafer in the CMP process.

FOREARM AND ELBOW INJURY

The purpose of this study was to develop an axial loading forearm fracture model and to determine the influence of forearm rotation on the fracture pattern. Twenty-six cadaveric arms were thawed in saline solution. Pressure-sensitive film was sealed and was placed through a lateral arthrotomy into the radiocapitellar joint. The arm was potted at the proximal part of the humerus with the elbow in extension. Rotational range of motion was measured with use of a goniometer starting from a supinated position (0 degrees ). Specimens were placed in a vertical position at various angles of forearm rotation, and a 27-kg mass was raised to 90 cm and was dropped onto the distal part of the radius. The pressure film was removed and was analyzed to determine the radiocapitellar joint contact area following impact. Each arm was dissected, and the injury pattern was assessed. Both-bone forearm fractures (proximal radial fractures with concomitant distal ulnar fractures) occurred at 5 degrees +/- 2.6 degrees of rotation, isolated radial head fractures occurred at 44.4 degrees +/- 5.2 degrees of rotation, and Essex-Lopresti fractures (radial head fractures with tearing of the interosseous membrane) occurred at 70 degrees +/- 25.2 degrees of rotation. The distribution of Essex-Lopresti and radial head fractures was significantly different at a cutpoint of 54 degrees of forearm rotation (p = 0.009), and the distribution of radial head fractures and both-bone forearm fractures was significantly different at a cutpoint of 10 degrees of forearm rotation (p = 0.001). The percent contact area of the radial head varied with the injury pattern (p = 0.029). Marginal radial head fractures occurred at 46.7 degrees +/- 6.6 degrees of rotation with a contact area of 30.9% +/- 8.6%, while comminuted radial head fractures occurred at 74.4 degrees +/- 27.2 degrees of rotation with a contact area of 53.9% +/- 8.3%. The amount of forearm rotation at the time of axial load impact directly influenced the injury pattern. Furthermore, the radial head contact area and the fracture severity increased in pronation compared with supination.

Numerical study of the hydromechanical behavior of two rough fracture surfaces in contact

Flow in fractures is traditionally modeled by characterizing the aperture distribution with some deterministic function or set of stochastic parameters. Other models generate the aperture distribution by the closure of two stochastic surfaces. The objective of this research is to develop a model where the aperture distribution is determined during the closure of two random elastic surfaces with complete hydromechanical interaction. Because stress and strain conditions required to generate a given aperture distribution are calculated during closure, the model is used to couple the mechanical and hydraulic characteristics of the fracture. Stochastic realizations of clay fracture surfaces are generated by measuring one‐dimensional profiles of a fracture surface. Next, the spectral representation of the profile is related to the fractal dimension of the fracture. Using the fractal dimension determined from one‐dimensional clay profiles, an equivalent two‐dimensional fractal surface is generated. Conceptually, each surface consists of linear elastic rectangular asperities resting upon a linear elastic half‐space. During closure, asperities that come into contact deform and punch into the half space creating mechanical interaction between all the asperities on the grid. Once we determine the aperture distribution at an applied stress level, a hydraulic gradient is applied across the fracture and fluid flow is determined. Nodal pressures created by flow deform the aperture distribution coupling hydraulic to mechanical behavior. Stress versus relative closure results indicate that stress increases nonlinearly with relative closure. Fluid pressures in the aperture distribution exert a significant influence on the mechanical characteristics of a fracture. Fluid discharge through the fracture decreases exponentially with an increase in relative closure. Flow calculated in the rough walled aperture distribution deviates increasingly from the parallel plate model with the geometric mean aperture as the percent contact area increases. The deviation results from an increase in tortuosity and channelling of the flow field in the aperture distribution. We can use this model to develop stress and flow versus relative closure constitutive relationships for a single fracture as a function of fracture surface geometry.

Distribution of pressures and forces on the wrist after simulated intercarpal fusion and Kienböck's disease

Limited intercarpal fusion has been recommended for the treatment of Kienböck's disease. The effects of a simulated scapho-trapezio-trapezoid (STT) fusion and simulated Kienböck's disease on the biomechanics of the radio-ulno-carpal joint were investigated. The percent force, the centroid of the force, and the percent contact area in each fossa were determined. It was found that a STT fusion with the scaphoid in a neutral or extended position unloads the lunate fossa. STT fusion in flexion does not affect lunate load. It is concluded from this biomechanical experiment that STT fusion with the scaphoid in a neutral or extended position unloads the radiolunate joint regardless of the condition of the lunate. This load is shifted to the radioscaphoid articulation.

単ロール急冷凝固Ａｌ‐１２ｍａｓｓ％Ｓｉ合金箔の表面状態に及ぼすロール回転数と溶湯噴出圧力の影響

The geometric uniformity on the surface of foils rapidly solidified depends on the roll speed and ejection pressure. The wetting pattern irregularity was fabricated on the roll contact side of foil when the roll speed was low, and that irregularity was eliminated when the roll speed was high. The wetting pattern on the roll contact side surface was consist of the uncontact area and directly contacting area. The uncontact part in the wetting pattern was reduced in size by increasing the roll speed and ejection pressure. The percentage of contact area where the foil contacted to the roll was 70-80% and the contact area increased when the roll speed and ejection pressure increased. The roughness of rotating direction of the roll contact side surface was smaller than that of the lateral direction. The roughness of roll contact side surface decreased with increasing of the roll speed and ejection pressure.

A TEST FOR THE ADHESIVENESS OF VITREOUS ENAMELS TO METAL1

A method of testing the adhesiveness of vitreous enamels to metal is developed. The test specimens are prepared by clamping together two strips of enameled metal while they are still in the furnace and allowing them to cool slowly in another furnace from a temperature of 500°C. The test consists of determining the force necessary to pull the two metal pieces apart when treated as a continuous strip of metal under tensile stress. As a source of additional data in analyzing results, an estimate is made of the percentage of contact area on each specimen within which failure occurred in the bond. The adhesiveness of an enamel containing cobalt, manganese, and nickel oxides is compared with the enamel minus these oxides. The cobalt enamel gave a much stronger bond than the cobaltless enamel, a result which ie in agreement with industrial experience. The degree of reproducibility is sufficient to permit positive distinction between conditions of adhesiveness which differ considerably.