Greater Contact Area Research Articles

Cutting Force Analysis when Milling Ti-6Al-4V under Dry and Near Dry Conditions Using Coated Tungsten Carbides

The effectiveness of the usage of coolant in high speed machining of highly reactive material like titanium and its alloys is still far away uncertain. For this reason, it is wiser to study the effectiveness of MQL under transient cutting speed before we go to the high speed machining. This paper discusses the effect of MQL on the machinability of Ti-6Al-4V by using PVD coated cemented carbide tools. The machinability of Ti-6Al-4V was investigated based on the effect on cutting force and the tool life. The performance of PVD coated cemented carbide tool was investigated at various cutting condition. Completely dry machining and near dry (MQL) were applied in this experiment. For near dry machining, two levels of coolant flow rate were investigated, 50 and 100 mL/H. The effectiveness of mist coolant was tested at three different levels of cutting speed, 120, 135 and 150 m/min. Application of mist coolant is more significant at cutting speed of 135 m/min. At this speed longer tool life was obtained when more coolant was applied. No significant effect of the cutting speed and coolant flow rate on the surface roughness. Surface roughness is more sensitive to the feed rate and the depth of cut. No significant effect of application of MQL on cutting force at early stage of machining. MQL seems to be more affective when tools start worn out where greater contact area between tool and work piece occur to give better lubrication effect.

In-vivo time-dependent articular cartilage contact behavior of the tibiofemoral joint

The purpose of this study was to investigate the in-vivo time-dependent contact behavior of tibiofemoral cartilage of human subjects during the first 300 s after applying a constant full body weight loading and determine whether there are differences in cartilage contact responses between the medial and lateral compartments. Six healthy knees were investigated in this study. Each knee joint was subjected to full body weight loading and the in-vivo positions of the knee were captured by two orthogonal fluoroscopes during the first 300 s after applying the load. Three-dimensional models of the knee were created from MR images and used to reproduce the in-vivo knee positions recorded by the fluoroscopes. The time-dependent contact behavior of the cartilage was represented using the peak cartilage contact deformation and the cartilage contact area as functions of time under the constant full body weight. Both medial and lateral compartments showed a rapid increase in contact deformation and contact area during the first 20s of loading. After 50s of loading, the peak contact deformation values were 10.5+/-0.8% (medial) and 12.6+/-3.4% (lateral), and the contact areas were 223.9+/-14.8 mm(2) (medial) and 123.0+/-22.8 mm(2) (lateral). Thereafter, the peak cartilage contact deformation and contact area remained relatively constant. The respective changing rates of cartilage contact deformation were 1.4+/-0.9%/s (medial) and 3.1+/-2.5%/s (lateral); and of contact areas were 40.6+/-20.8 mm(2)/s (medial) and 24.0+/-11.4 mm(2)/s (lateral), at the first second of loading. Beyond 50 s, both changing rates approached zero. The peak cartilage contact deformation increased rapidly within the first 20s of loading and remained relatively constant after approximately 50 s of loading. The time-dependent response of cartilage contact behavior under constant full body weight loading was significantly different in the medial and lateral tibiofemoral compartments, with greater peak cartilage contact deformation on the lateral side and greater contact area on the medial side. These data can provide insight into normal in-vivo cartilage function and provide guidelines for the improvement of ex-vivo cartilage experiments and the validation of computational models that simulate human knee joint contact.

In brief: meniscal tears.

Meniscal tears can cause considerable symptoms (pain, catching or locking, and effusions) and may subject the knee to premature degeneration of the joint. They also are one of the most common indications for an orthopaedic surgical procedure [3]. As such, although a tear of the meniscus is never life- or limb-threatening, its importance in orthopaedic surgery is undoubted.

Machinalibilty of Ti-6Al-4V Under Dry and Near Dry Condition Using Carbide Tools

The effectiveness of the usage of coolant in high speed machining of highly reactive material like titanium and its alloys is still far away uncertain. For this reason, it is wiser to study the effectiveness of Minimum Quantity of Lubri- cant (MQL) under transient cutting speed before advancing to high speed machining. This paper discusses the effect of MQL on the machinability of Ti-6Al-4V using Physical Vapor Disposition (PVD) coated cemented carbide tools. The ma- chinability studied parameters were the generated cutting force and the tool life. The performance of PVD coated cemented carbide tool was investigated at various cutting condition under dry and near dry (or MQL) machining. For near dry ma- chining, two levels of coolant flow rate of 50 and 100 mL/H were investigated. The effectiveness of mist coolant was tested at three different levels of cutting speed, 120, 135 and 150 m/min. Application of mist coolant is more effective at cutting speed of 135 m/min. At this speed longer tool life was obtained when more coolant was applied. The effect of the cutting speed and coolant flow rate on the surface roughness is not significant. Surface roughness is more sensitive to the feed rate and the depth of cut. No significant effect of MQL on cutting force at early stage of machining was observed. MQL seems to be more effective when tools start to wear out, where greater contact area between tool and work piece occurs to give better lubrication effect.

Densidade do solo no ambiente solo-semente e velocidade de emergência em sistema de semeadura de milho

O microambiente próximo à semente é influenciado diretamente pelo tipo de mecanismo de abertura do sulco e elemento compactador do solo. Nesse sentido, este trabalho objetivou avaliar a densidade do solo na região da semente, em sistema plantio direto, utilizando a tomografia computadorizada. O experimento foi montado em esquema de parcelas subsubdivididas, em que as parcelas foram constituídas de três teores de água do solo (0,22; 0,28; e 0,34 kg kg-1); as subparcelas, de dois mecanismos de abertura do sulco (haste sulcadora tipo facão e disco duplo); e as subsubparcelas, de dois tipos de elementos compactadores (borracha e lisa), com três repetições, no delineamento em blocos casualizados, na cultura do milho. Foram retiradas amostras indeformadas de solo sobre a linha de plantio, onde deveria conter a semente, para a obtenção de tomografias com resolução milimétrica, a fim de determinar sua densidade. Foram realizadas as determinações de densidades de solo (máxima, mínima e média), na posição onde se encontrava a semente no bloco indeformado. Os resultados mostraram que os tratamentos estudados não interferiram significativamente nos valores de índice de velocidade de emergência e densidade mínima medida pelo tomógrafo. O mecanismo tipo disco duplo proporcionou maiores valores de densidades (média e máxima), bem como menor percentagem de emergência; e o uso do elemento compactador de borracha proporcionou menor pressão aplicada sobre a semente, em decorrência da maior área de contato com o solo. O método da tomografia computadorizada mostrou-se adequado e eficiente na determinação da densidade do solo na região da semente.

An Experimental Approach of Influences of Perforated Length and Fractures on Horizontal Well Productivity

Abstract Many simulation studies have been conducted regarding the importance of perforated well length on horizontal well performance. All of these studies suffered from their dependence upon theoretical models, which lack plausibility due to the lack of accurate experimental and/or field data. Therefore, there is a real need for experimental data to be used for tuning the single well simulation models before applying a full field simulation of oil reservoirs with horizontal wells. This experimental study was designed to investigate the influences of fractions of perforated length, total length, and fractures, which do not intersect with a well axis, on the productivity of horizontal wells. An experimental model (60 cm x?40 cm × 20 cm) was designed and used to achieve the study objectives. Carefully sized sandpacks were used to represent the homogeneous unconsolidated porous media while a perforated aluminum sheet was used as a horizontal fracture parallel (horizontal fracture) and perpendicular but not intersecting (vertical fracture) the horizontal well axis in the sandpack. Several runs were carried out using horizontal wells with different lengths and different perforation fractions of total length utilizing homogenous porous media with and without fracture systems. The results indicated that an increase of perforated well length increases flow rate of the horizontal well for both homogeneous and fractured formations that do not intersect with the well axis. Furthermore, horizontally-fractured formations parallel to and vertically-fractured formations vertical to the well axis improve the productivity of horizontal wells for different perforation ratios. A single vertically-fractured porous medium provides a higher productivity ratio than a horizontally-fractured one for the same perforation length and intensity, when both fracture systems do not intersect with the well axis. Several empirical equations were developed to correlate the horizontal well productivity with perforated length for homogenous and fractured porous media. Ignoring of the effect of pressure drop along horizontal well may have serious implications on perforated well length since proportionality of the productivity index to the well length is no longer valid. Introduction and Literature Review Recently, the economic feasibility of drilling a horizontal well improved drastically due to advances in drilling technology. Advantages of horizontal wells over vertical well applications have been confirmed by many scientists(1–4) and operators(5–7). Horizontal wells showed many distinct advantages over vertical ones such as improvement of well productivity, attenuation of sand production, and significant reduction of gas and/or water coning problems. From reservoir and production engineering standpoints, the sole difference between vertical and horizontal wells was identified to be the contact area. For a partially penetrating vertical well, the reservoir disturbance due to a vertical well was limited to the close vicinity of the wellbore hole(8). Then, the choke diameter became the main parameter affecting the flow rate. For a horizontal well, the disturbance created by the well not only affected the vicinity of the wellbore, but also influences the whole reservoir due to the greater contact area of the pay zone penetrated by the well.

CaO-MgO CATALYSTS FOR SOOT COMBUSTION: KNO3 AS SOURCE FOR DOPING WITH POTASSIUM

MgO, CaO, an equal ratio mixture of the oxides (50-CaO) and a sample with 10% potassium added to the previous mixture, showed increasing activity for the catalytic combustion of carbon black, a model compound for soot. These catalysts were characterized by XPS, BET, DRIFTS and AAS. Activity was measured by TGA and by TPO; CO and CO2 concentration in the outlet gas flow were measured by NDIR. Pure MgO was barely active. The 50-CaO catalyst was as active as the pure CaO in spite of a lower content of calcium. This was attributed to greater contact area and better dispersion of calcium, lesser bulk and surface carbonation, cooperative effect of magnesium that diminishes the stability of adsorbed surface compounds, and a greater accessibility of O2(g) to calcium sites. Potassium introduction over the 50-CaO produced high activity, related to a increase of the surface concentration of oxygen on the catalyst and larger CO2/CO ratio in the exit gases. Moreover, potassium addition resulted in a lower content of calcium on the surface, hence less carbonation of the catalyst

Effect of End-Cutting Intramedullary Reamers on Host-Allograft Contact Area

Use of large allografts in the diaphyseal region can be complicated by nonunion of the host bone to the allograft. Increasing the contact area at this interface can help prevent this from happening. This study investigated the resulting contact area with use of end-cutting reamers to prepare the interface of host and allograft bone in the daiphyseal region, as compared with hand preparation using a sagittal saw. Using a sawbone model, it was demonstrated that the end-cutting reamers produced a significantly greater contact area, compared with hand-cutting techniques.

Effect of fillers on parameters of dry and swollen polymer matrix networks

The effect of nano- and micro- particle size of SiO2 on dry and swollen parameter network of the polymer matrix blends of acrylontrile-butadiene (NBR) and chlorosulphonated polyethylene (CSM) such as: volume and mass degree of swelling Rv and Rw; volume fraction of NBR-CSM polymer matrix in swollen gel V2 elasticity modulus G; interaction parameter between NBR-CSM polymer matrix and solvent ? and crossiinking density ?, was tested. The influence of nano-and micro- particle size of SiO2 on physical and mechanical properties, as well as effectiveness volume ratio of filiers in NBR-CSM polymer matrix at 300% elongation was tested using Einstein-Quth-Gold equation. The Kraus equation for swelling test of NBR-CSM polymer matrix containing nano- and micro- particle size of SiO2. Test results have shown that a greater interaction of nano-particie size of SiO2 with NBR-CSM polymer matrix, and possible chemical bonding, than the one of micro-silica was a consequence of a greater contact area. This results in better physical and mechanical properties.

PERFORMANCE OF HORIZONTAL WELLS WITH LONGITUDINAL FRACTURES IN RESERVOIRS WITH BOTTOM-WATER DRIVE

The production performance of un-fractured horizontal wells and horizontal wells with longitudinal fractures of various vertical penetrations in reservoirs with bottom water drive has been studied using a scaled three-dimensional rectangular model. The model represented the drainage volume for a single horizontal well in one of the Middle East reservoirs. The model was packed with glass beads yielding a porosity of 0.36 and a permeability of 400 Darcies, and kerosene and distilled water were used to represent the reservoir fluids. The production rate was chosen so that the oil–water interface would remain stable until it approaches the producing well. In general, wells with greater contact area with the reservoir gave higher oil recovery before water breakthrough, and experienced lower pressure drop. Increasing the fracture penetration improved the production performance up to a limit beyond which no further improvement was obtained. Interestingly, it was found that extending the fracture penetration towards the original oil–water contact did not, as might have been expected, result in earlier water breakthrough. The fracture acted as an in situ oil–water separator and an equilibrium water level was maintained within the fracture as long as the oil–water interface was flat as it moved upward towards the well. *Currently with Qatar Gas Company.

Patello-femoral contact area and compressive force after anteromedial displacement of tibial tuberosity in amputated knees

Contact force and contact area in the patello-femoral joint was biomechanically analyzed using seven amputated legs. The knees were fixed firmly to the experimental apparatus and 300 N of tension was applied to the quadriceps tendon. Total contact force was measured using pressure-sensitive film, and the ratio of the contact area to the patellar joint surface (%) was measured using hydrophilic vinyl polysiloxane impression material. At a Q-angle of 0° with no advancement, 10 mm and 20 mm advancement of the tibial tuberosity, the total contact force on the patello-femoral joint at a knee flexion of 45° was 266±55 N, 191±58 N and 146±58 N, respectively. The total contact force became smaller as the advancement of the tibial tuberosity changed to 5, 10, 15 and 20 mm. Especially, the total contact force with Q-angle of 0° and anterior advancement of 15 and 20 mm was significantly smaller than that with no advancement. With a Q-angle of 0°, the contact area of the patello-femoral joint at 10 mm advancement was the greatest, occupying 30.1±9.9% of the whole patellar joint surface. The mean contact pressure with Q-angle of 0° and anterior advancement of 10 mm was smaller than that with all other positions, but there was no significant difference. In this experiment, combined anterior and medial displacement of the tibial tuberosity reduced the contact force in the patello-femoral joint of the amputated legs, and an advancement of 10 mm achieved optimal reduction of force and the greatest contact area.

Seasonal changes in the dissolved oxygen status of two tropical water storages

AbstractSeasonal changes in the dissolved oxygen characteristics of two tropical impoundments in north‐western Queensland are described. The lakes are compared in terms of their dissolved oxygen saturation deviation index (OSDI). In the deeper, more sheltered Lake Julius (20°08'S, 139°43.5′E) OSDI was positively correlated with vertical water column stability which explained ∼50% of the observed variation in OSDI. In the shallower, more exposed Lake Moondarra (20°35'S, 139°34.5′E) which, like Lake Julius experiences prolonged periods of hypolimnetic oxygen depletion, there was no significant correlation between OSDI and water column stability. It is concluded that in the considerably less stable Lake Moondarra, high OSDI values are maintained by the greater area of contact between the hypolimnion and sediment surface. In neither lake was there any significant correlation between OSDI and the phytoplankton biomass (measured as sub‐surface chlorophyll a concentration). Volume and 4°C‐temperature corrected rates of oxygen depletion for the entire lake were higher in Lake Julius (0.075 mg L−1 day−1) than in Lake Moondarra (0.038 mg L−1 day−1).

Biomechanics of the human knee joint in compression: reconstruction, mesh generation and finite element analysis

Computer-assisted tomography with direct digitization and measurements were used to reconstruct the detailed geometry of an entire human knee joint specimen. These data were then merged with a mesh generation algorithm and material properties reported in the literature to develop a three dimensional non-linear finite element model of the knee joint. This model consists of three bony structures (tibia, femur and patella), their articular cartilage layers, medial and lateral menisci, and five principal ligaments (collaterals, cruciates and patellar tendon). The menisci are represented as a non-homogeneous composite of a solid matrix reinforced by radial and circumferential collagen fibres. The articulation of cartilage layers with each other as well as with intervening menisci and the wrapping of the medial collateral ligament with tibia are treated as general large displacement frictionless contact problems. The incremental response of the tibiofemoral joint in full extension is determined under axial forces of up to 1000 N applied on the femur. Analyses are carried out with the tibia fixed while the femur is set free to translate in medial-lateral, anterior-posterior, and proximal-distal directions; the internal-external rotation is either left free or fixed. Cases simulating total meniscectomy are also considered. The joint exhibits a non-linear stiffening response in the axial direction with large coupled displacements. At 1000 N, the load transferred through the joint is found to be greater for the lateral compartment than for the medial compartment and at the cartilage-cartilage contact than at the meniscus-cartilage contact. The menisci, firmly attached by their horns to the tibia, are radially extruded under the axial compression and cause greater contact areas and smaller, more uniform, contact pressures. Removal of menisci markedly increases the primary and coupled laxities of the joint, reduces total contact areas, and increases contact stresses. The predictions are in general agreement with measurements reported in the literature.

The use of SEM to study the effect of bacteriostatic properties of sponges on bacterial attachment and growth

Many bacteria possess the ability to adhere and grow on solid surfaces. The existence of bacterial biofilms in food processing plants and in or on food processing equipment can have serious consequences, and various cleaning and sanitizing procedures are employed to deal with such contamination. Bacteriological monitoring methods are employed to test the efficiency of these cleaning procedures, and the most widely used technique is the swab rinse method whereby a moistened sterile sv/ab is rubbed over the surface of the area to be sampled. One difficulty with this procedure is that the surface contact area of the swab is quite small, so that evenly swabbing a defined area can be difficult. To correct this problem, square sponges have been tried as substitutes to provide a much greater contact area. However, recent studies have shown that some sponges may contain bacteriostatic substances which can hinder test results. To determine whether some makes of sponges may contain bacteriostatic agents, SEM was used to examine samples which had been exposed to conditions to promote bacterial attachment and growth on their surface. The results of these observations were correlated with microbial tests to determine bacteriostatic activity of duplicate sponge samples.

Degenerative changes in the structure of neuromuscular junctions of Manduca sexta during metamorphosis.

During the degenerative processes that precede and accompany metamorphosis of the larval mesothoracic dorsal longitudinal muscles of Manduca sexta, the motor nerves and neuromuscular junctions undergo a variety of structural changes that are largely secondary to the changing morphologies of their respective glia. In the central region of the main motor nerve, the multiple layers of glial processes surrounding each of the large axons withdraw, leaving them apposed. In the peripheral region of the main motor nerve and in the secondary and tertiary nerve branches supplying the muscle, the outer glial processes of the nerve sheath and those that loosely wrap accompanying small neurosecretory axons all swell. Phagocytic cells and cells of unknown function invade the outer region of the nerve. In the neuromuscular junctions, the glial cells withdraw their processes from a complicated interdigitation with processes from the muscle fiber and from their relationship with the nerve terminal. As degeneration proceeds, this allows a greater area of contact between each nerve terminal and the muscle fiber. Within each junction there is a mixture of both functional and non-functional regions and active zones, as determined by both thin-section and freeze-fracture observations. No correlation was found between the degree of degeneration of a neuromuscular junction and its association with a particular muscle fiber or its position on the fiber relative to the origin or insertion.

Trends in use of health care services in Swedish primary care district. A ten year perspective.

In a study that covered ten years a questionnaire about use of health care facilities was mailed each autumn to 1/60 representative samples of the population in Sollentuna, a Swedish primary care district with three health centres. Primary care was the health care form with the greatest contact area with the population studied. However, the strengthening of district physician resources at one of the three health centres did not, in the long term, lead to more people coming into contact with this form of medical care. It was more common for those who visited a private doctor or school/company doctor also to consult a district physician than vice versa. Similarly, hospital patients visited the health centre to a greater degree than patients of health centres visited hospitals. The only long-term change in the flow of patients that could be registered was a reduction in the number of patients who visited hospital emergency departments. It is concluded that the implementation of an annual survey may be considerably more helpful than more sparse investigations in distinguishing between temporary fluctuations and real changes.

Nucleation and growth studies of gold films prepared by evaporation and ion-assisted deposition

Thin gold films have been deposited onto glass substrates by electron-beam evaporation and by oxygen and argon ion-assisted deposition. The nucleation and growth of the films have been monitored in situ by ellipsometry and spectral reflectance and transmittance measurements. The composition of the film surface has been characterized by ion-scattering spectroscopy. These techniques show that the thickness at which coalescence of gold islands occurs is less for both ion-assisted films than for the evaporated film deposited on a clean substrate. Monitoring of coalesced films during sputter-etching combined with measurements of reflectance from both sides of the coated surface indicate that all films have a layer of density less than bulk near the air-film interface, and for evaporated and argon ion-assisted films, another near the gold-substrate interface. Oxygen ion-assisted films showed no evidence of an interfacial layer near the substrate and it is concluded that these films had a much greater area of contact with the substrate than evaporated or argon ion-assisted films.

Geometric accommodation between the dimensions of erythrocytes and the calibre of heart and muscle capillaries in the rat.

The finer and more closely arrayed the capillaries are, the more efficiently oxygen will be transported to tissue because the same blood volume has greater contact area with the tissue and the diffusion distance for the oxygen is minimized. If these principles are actually governing microvascular structure, then the finest capillaries will be the narrowest channels which circulating erythrocytes can transit. Ascertaining the existence of this geometric limit requires quantitative data of demonstrated reliability on erythrocyte geometry and on capillary diameters. The study was done on Wistar rats. Constant flow perfusion of skeletal and cardiac muscle by a modified Batson's compound for anatomical casting made available rigid three-dimensional replicas of the microvasculature which shrank less than 1% when the tissue was digested with potassium hydroxide. Measurements of individual capillaries were made on high contrast scanning electron micrographs of the casts. Measurements on individual rat erythrocytes were done on photomicrographs of cells on edge. Reliability of these data was tested in three ways. First, repeatability of the tracing of the cell outline was tested by processing a duplicate set of photomicrographs. Secondly, correlations of the various parameters were found. Thirdly, results from other techniques of measuring erythrocytes were examined for areas of agreement and also for causes of possible error for areas in dispute. Because of known variability in erythrocyte sizes and shapes between species and between individuals within a species, we compared the data on erythrocyte geometry and capillary diameters for samples taken from the same individual rat. The data revealed a very positive indication that the lowest range of capillary diameters were at the limits of deformation of the circulating erythrocytes. Ninety-five per cent of the erythrocytes sampled could pass through a channel 2.9 micron in diameter. A small number of the capillaries measured were narrower than this limit. The data on erythrocytes and capillaries were compared for six rats. The limiting diameter for passage of erythrocytes was remarkably uniform for all six animals.

Dynamic and Performance Characteristics of Baseball Bats

Abstract The purpose of this investigation was to compare the dynamic and performance characteristics of wooden and aluminum baseball bats. Field data collected during batting practice by accomplished college athletes revealed a 3.85 mph mean difference favoring balls batted with the aluminum bat. Laboratory data indicated that the aluminum bats possessed a greater contact area wherein reaction forces at the bat handle were small. This finding indicates that the aluminum bat has a larger center of percussion and offers a possible explanation for the significant mean difference found in the field.