A system was designed to measure the effect of gap size on semi-span low Reynolds number wind tunnel experiments. The lift forces on NACA 1412, NACA 2412 and NACA 4412 half wings were measured using a strain gauge balance at chord Reynolds numbers of 100,000 and 200,000 and three different gap sizes including sealed gap. Pressure distributions on both airfoil top and bottom surfaces in the chord-wise direction near the gap were recorded for these airfoils. Also recorded was the span wise pressure distribution on both the airfoil surfaces at the quarter chord section. The results revealed that the presence of the gap, however small, affects the measurements. These effects were mainly observed in drop of lift and change in zero lift angle of attack and change in stall angle for the airfoil. The size of the gap is not linearly related to these changes, which also depend on the camber of the airfoil. These changes occur due to the flow through the gap from the lower surface to the upper surface of the model. The wing/end plate gap effect reduces along the span but is not fully restricted to the base of the model and the model behaves more like a full three-dimensional wing than a semi-span model. This study was made possible with the support of Department of Aerospace and Ocean Engineering, Virginia Polytechnic Institute and State University under the supervision of Dr. James Marchman / Master of Science

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Disc brake calipers are subjected to complex mechanical loading and interaction of individual components in a typical brake assembly makes design improvement very challenging. To analyse caliper behaviour, complex Finite Element models were created and successfully validated using a variety of experimental techniques, including exceptionally suitable Digital Image Correlation. A novel methodology to optimise caliper design was developed, using non-linear contact Finite Element Analysis and topology optimisation, to generate lightweight, high performance brake calipers. The method was used on a Formula 1 brake assembly and significant improvement in structural design was achieved, with the new caliper being lighter and stiffer than the original. The same approach was used on more conventional 4 pistons calipers using various boundary conditions with particular focus on mass reduction and considerably lighter designs were achieved. The influence of specific features of the optimised calipers on the structural performance was also successfully investigated.

Este trabalho apresenta uma metodologia para predição da distribuição de pressão sobre uma asa bi-trapezoidal genérica usando redes neurais artificiais. O toolbox de redes neurais do MatLab® foi utilizado para o treinamento e validação das redes neurais e os conjuntos de treinamentos foram obtidos por meio do software BLWF® versão 28 (Boundary Layer Wing-Fuselage) um código CFD (Computacional Fluid Dynamics) de potencial completo com correção de camada limite. Levando em consideração o nível de complexidade do problema, optou-se por dividir o estudo em três etapas de desenvolvimento. Inicialmente, uma rede neural foi treinada considerando apenas as variáveis de condição de voo e de forma em planta. Resultados promissores motivaram a criação de uma segunda rede neural, mais genérica, na qual foram adicionadas variáveis de três perfis distribuídos ao longo da asa. Porém apenas um desses perfis era variável enquanto que os demais eram parametrizados com relação à este perfil. Criou-se, por fim, uma rede neural ainda mais genérica, desta vez atentando também para as variáveis dos três perfis de modo independente. Os resultados obtidos mostram que esta metodologia pode ser usada como interessante ferramenta para obtenção de distribuição de pressão, especialmente em projetos de MDO (Multi-Disciplinary Optimization), uma vez que ela possibilita uma predição rápida, precisa e de fácil automatização de pressão em uma asa genérica. / This work shows a method for predicting pressure distribution over a generic bi-trapezoidal wing using artificial neural networks. The MatLab® Neural Network Toolbox was used for the neural network implementation and the training set was obtained using the BLWF® version 28 (Boundary Layer Wing-Fuselage), a full potential CFD (Computational Fluid Dynamics) code with boundary layer correction. The work was divided in three development phase, according with the problem complexibibility level. Initially, a neural network considering only flight conditions and plan form variables was trained. Promising results motivated the generation of a more generic neural network, considering also parameters of three airfoils distributed along the wing spanwise and chordwise. However only one airfoil was variable, the two other were parametrized in relation to the variable airfoil. At last, an even more generic neural network was generated, this time considering also the variables of the three profiles independently. The results show that this methodology can be successfully used as an interesting tool to obtain the pressure distribution, especially on the solution of MDO (Multi-Disciplinary Optimization) problems, since it allows fast prediction, automation facility and accurate measuring of the pressure distribution under a generic wing.

Hallux valgus and hallux limitus are two common foot pathologies that may require surgical intervention. While the modified Austin bunionectomy and the Youngswick osteotomy/cheilectomy respectively, are often used to correct these conditions, insufficient research has been published regarding the effects of these procedures on plantar pressure distribution of the foot. This thesis involves a series of six studies investigating topics relating to radiographic measurements and plantar pressure distribution over a two-year period, in normal feet and in hallux valgus and hallux limitus feet before and after corrective surgery.A review of the literature is presented relating to the development of plantar pressure measurement technology, the aetiology and surgical management of hallux valgus and hallux limitus, the reliability of the EMED system used in the studies, and the related clinical uses of plantar pressure measurement.An initial study was designed to investigate the reliability measurements using a simplified two-step method of data collection as compared to the traditional mid-gait technique of ten normal asymptomatic subjects. Intra-class correlation coefficients were calculated and compared for the pressure variables of contact area, contact time, maximum force and peak pressure of ten regions of the foot.A study to determine normal reference range values for the EMED-SF system was then conducted using thirty healthy subjects and the two-step method of data collection. Descriptive statistical reporting of peak pressure, mean pressure and pressure-time- integrals were presented for ten regions of the foot.Three related studies on radiographic and plantar pressure measurement differences, and their relationships were made using thirty normal, hallux valgus and hallux limitus feet. Various angular and linear radiographic measurements were tested for intra-rater ++ / reliability of measurement and pressure variables of peak pressure, mean pressure and pressure-time-integral of 10 regions of the foot were recorded and one way analysis of variance employed to assess any significant differences.Finally, two independent two-year prospective studies were designed to investigate the effects of the modified Austin bunionectomy for hallux valgus and the Youngswick osteotomy/cheilectomy for hallux limitus on plantar pressure distribution of the forefoot. In addition, fundamental radiographic measurement changes of the forefoot of hallux valgus subjects and range of motion changes of the first metatarsophalangeal joint of hallux limitus subjects were conducted. Thirty-six healthy volunteers acted as control subjects, 31 subjects (44 feet) with hallux valgus and 17 subjects (23 feet) with hallux limitus were included in the study. Using an EMED-SF system, plantar pressure variables of peak pressure, pressure-time-integral, contact time, maximum force and force-time-integral were recorded at six regions of the forefoot, pre-operation and repeated at three, six, 12, 18 and 24-months post-operation for surgical subjects. Control subjects were tested at zero and 24-months. Descriptive statistics, multivariate and univariate analysis of variance with contrasts, t-tests of significance and correlations between certain measurement parameters were used in the analysis of the results.The findings of these studies suggest that the two-step method of data collection of plantar pressure measurements is more reliable that the traditional mid-gait technique for most pressure variables. Consequently, the two-step method was employed as the preferred method of data collection in this series of studies.With respect to radiographic differences between normal, hallux valgus and hallux limitus, it appears that hallux valgus feet have significant increases in ++ / metatarsus primus varus and first metatarsal protrusion distance, while hallux limitus feet have increased hallux abductus interphalangeal angles. Comparison of pressure variables between each group demonstrate hallux valgus feet have a medial localisation of peak pressure beneath the first, second and third metatarsal heads, suggesting that hyperpronation of the foot is associated with the development of hallux valgus. Hallux limitus feet on the other hand, show increased pressure beneath the hallux, third and fourth metatarsals and lesser toes, indicating a more lateral locus of pressure loading, suggestive -of the foot functioning in a more supinated position. No significant relationship was found between any radiographic parameter and pressure variable tested in either group of subjects.Plantar pressure measurement changes show the greatest variation during the initial three to six months following surgical treatment of hallux valgus and hallux limitus. The Youngswick osteotomy/cheilectomy for the treatment of hallux limitus produces near-normal range of motion of the first metatarsophalangeal joint. Pressures of the first metatarsal head remain relatively constant over the period of measurement, while a significant reduction of the hallux and lateral metatarsals were noted, related to increased dorsiflexion of the hallux. Pressures of the second metatarsal head remained significantly above pre-operation levels. The modified Austin bunionectomy for the treatment of hallux valgus produced 24-month radiographic changes consistent with accepted values. Pressure variables of the hallux reduced to normal values, with the first metatarsal head demonstrating an initial significant decrease and subsequent increase by twelve months post-operation to remain with the second metatarsal head at relatively similar values to pre-operation measurements.The research demonstrates ++ / the two-step method of data collection is a viable means of obtaining reliable plantar pressure measurement data in the clinical situation. The investigations into radiographic and plantar pressure distribution indicate that structural radiographic and functional differences exist between normal, hallux valgus and hallux limitus feet. However, no relationship could be found between any of the radiographic parameters and pressure variables tested.The modified Austin bunionectomy for hallux valgus significantly reduced fundamental radiographic measurements to accepted post-operative values, while the Youngswick procedure for hallux limitus significantly increased the amount of post-operative dorsiflexion of the hallux to normal values. The research demonstrates that immediate and longer-term functional changes to the forefoot occur following the surgical treatment of hallux valgus and hallux limitus, however plantar pressure measurements do not return to normal values. No correlation was found between plantar pressure measurements and post- operative radiographic measurements in the hallux valgus group. However, the increased amount of dorsiflexion of the hallux post-operatively in the hallux limitus group was correlated with reduced lateral loading of the forefoot. Post-operation changes of plantar pressure distribution indicate that the rehabilitative period required to achieve stable foot function is between twelve to eighteen months. Furthermore, plantar pressure measurement technology offers the clinician a useful tool to monitor foot function prior to and following therapeutic intervention.

This article aims to design an innovative polishing method that can do polishing job to a complicated axial symmetric free surface. The main task of the system is to increase the precision of a middle size (diameter range from 50mm to 150mm) free surface with low precision (form error is larger than 10£gm, even reach few hundred £gm. By using the developed polishing system, the precision is expected to reach and order of sub-micron. It is a machining method which able to outcome a precise free surface, and also a high efficient free surface machining method compared to machining technique nowadays. At the beginning of this article, a logical thinking method will be used to set up a number of sub-targets from the task of the article. From those sub-targets, the keys of the polishing method would come out to accomplish the task. They are: 1.The machining tool is deformable and able to match up the shape of the surface of the tool to enlarge the polishing area. This will increase the efficiency of the machining method; 2.The pressure distribution between the tool and work piece is controllable to let the surface area with larger error form has larger machining rate. By accomplish the sub-targets above, a set of form error compensate strategy can be use to remove the error profile of the free surface with high efficiency. To increase the efficiency of the polishing system, the analysis of the force guide by ANSYS (a finite element analysis software) will be done to create a relation between the force applied and the pressure distribution. This will make the pressure distribution construction task easy and the efficiency of polishing will be increased. According to the machining method designed above, a prototype polishing machine will be designed, and a series of experiments will be done on the designed prototype polishing machine to test the workability of the polishing method. The outcome of the experiments shows that the machine not only has good repeatability, but also has a very high machining efficiency. Besides, the machining distribution experiment shows that the machining method has ability to remove the error distribution from the free surface. It means that is able to do precision machining job to the free surface.

<p>Soil compaction is an inevitable result of agricultural practices. It alters physical properties of soil and tends to be undesirable as it adversely affects water and nutrient penetration. Furthermore, additional energy is spent to till the soil. Although a tremendous amount of research has been conducted in the area of soil compaction, the focus has been primarily on surface soil displacement.</p> <p>Realizing that the observed soil displacement is the cumulative effect from the compaction of subsurface layers, this research discusses the displacement and distributed pressure through the soil from a surface load. A given volume of soil of known density and moisture content was loaded at the surface with a slowly applied force using an Instron® testing machine. The distribution of the pressure and displacement profile from the surface to depth was measured to provide insight into the formation of the subsurface soil structures. The nonlinear exponential decay of the soil displacement (compaction) from the surface to a given depth converges to zero at the location of a hard, compact layer or a point where no soil movement occurs, regardless of the initial soil compaction. By increasing soil moisture content and decreasing soil bulk density, the vertical soil displacement increased at the surface and within the soil profile, and the pressure distribution decreased with depth. Changing the shape of loading surface had minimal effect on soil displacement.</p>

<p>The pressure-density relationship and the pressure distribution inside the compression chamber of a newly designed New Holland BB960 large square baler were studied for the baling of alfalfa, whole green barley, barley straw, and wheat straw. An analytical model was developed for the pressure distribution inside the compression chamber of the large square baler in the x-, y-, and z-directions by assuming isotropic linear elastic properties for forage materials. In order to validate this model, a tri-axial sensor was designed and used to measure the forces inside the compression chamber when whole green barley, barley straw, and wheat straw were baled. The experimental results proved that the developed analytical model for each of the tested forage materials had a good correlation with the experimental data with a reasonable coefficient of determination (0.95) and standard error (20.0 kPa). Test data were also used to develop an empirical model for the pressure distribution inside the compression chamber of the baler for each of the tested forage materials using least square method in regression analysis. These empirical models were simple equations which were only functions of the distance from the full extension point of the plunger along the compression chamber length.</p><p>Analytical and empirical models were also developed for the pressure-density relationship of the baler for baling alfalfa and barley straw. Results showed that bale density initially decreased with distance from the plunger, and then remained almost constant up to the end of the compression chamber. The developed empirical model for both alfalfa and barley straw was a combination of a quadratic and an exponential equation. In order to validate the developed models, field tests were performed by baling alfalfa and barley straw of different moisture contents, flake sizes, and load settings. The forces on the plunger arms were recorded by a data acquisition system. The actual bale bulk density was calculated by measuring the bale dimensions and weight. Results showed that both load setting and flake size had a significant effect on the plunger force. The plunger force increased with increased load setting and flake size. Comparing analytical and empirical models for bale density as a function of the pressure on the plunger showed that the trend of variation of density with pressure in both models was similar, but the rate of change was different. The variation rate of density with pressure in the analytical model was higher than that of the empirical model. The analytical model underestimated the bale density at low plunger pressures but showed more accurate prediction at higher pressures, while the empirical model accurately predicted the bale density at both low and high pressures. Some crop properties such as coefficient of friction and modulus of elasticity were determined for the development of the pressure distribution model. Results showed that static coefficient of friction of alfalfa on a polished steel surface was a quadratic function of material moisture content, while the relationship between the coefficient of friction of barley straw on a polished steel surface and material moisture content was best expressed by a linear equation. Results of this study also proved that modulus of elasticity of alfalfa and barley straw was constant for the density range encountered in the large square baler.</p>

<p>Soil compaction is an inevitable result of agricultural practices. It alters physical properties of soil and tends to be undesirable as it adversely affects water and nutrient penetration. Furthermore, additional energy is spent to till the soil. Although a tremendous amount of research has been conducted in the area of soil compaction, the focus has been primarily on surface soil displacement.</p> <p>Realizing that the observed soil displacement is the cumulative effect from the compaction of subsurface layers, this research discusses the displacement and distributed pressure through the soil from a surface load. A given volume of soil of known density and moisture content was loaded at the surface with a slowly applied force using an Instron® testing machine. The distribution of the pressure and displacement profile from the surface to depth was measured to provide insight into the formation of the subsurface soil structures. The nonlinear exponential decay of the soil displacement (compaction) from the surface to a given depth converges to zero at the location of a hard, compact layer or a point where no soil movement occurs, regardless of the initial soil compaction. By increasing soil moisture content and decreasing soil bulk density, the vertical soil displacement increased at the surface and within the soil profile, and the pressure distribution decreased with depth. Changing the shape of loading surface had minimal effect on soil displacement.</p>