The prediction of the mechanical properties of wood and the evolution of its damage has been essential for its application in many fields such as bridges and houses construction, racks of trucks and so on. In more val...The prediction of the mechanical properties of wood and the evolution of its damage has been essential for its application in many fields such as bridges and houses construction, racks of trucks and so on. In more valorization of biomaterials following the example material wood arouses for a few years a?private interest on behalf of the populations. The experimental characterization?makes it possible to consider the mechanical properties local of Pericopsis elata (Assamela) according to various parameters (the wood turpentine, the orientation of wood fibers, water the content, the type of test …). From the?results, we evaluate the mechanical characteristics of Pericopsis elata (Assamela)?according to the three directions of Orthotropy. Then from the tests of load-discharge we measured the evolution of the damage using the variation of the Young modulus, which enabled us to note the reduction in the modulus of elasticity because of the damage following the three directions. Finally we noted a progressive and irreversible degradation of mechanical properties induced by the development of the microscopic cracks within material.展开更多
Unsteady currents fluids flowing through a baffle with holes found in a mobile storage tank are complex to analyze. This study aims to evaluate the effects of fluid structure interactions (FSI) on baffles in tanks car...Unsteady currents fluids flowing through a baffle with holes found in a mobile storage tank are complex to analyze. This study aims to evaluate the effects of fluid structure interactions (FSI) on baffles in tanks carried on mobile trucks that, more often than not, experience sloshing phenomenon engulfed by turbulences behaviors with respect to different motions of the truck. Mindful of the different types of baffles that are used in the tanks to limit sloshing wave activities and improve safety by allowing fluid to pass through carefully designed holes that are also placed in a specific pattern, the fluid structure interaction around a baffle with a hole is evaluated here through computing. Passing through the solver in COMSOL, an equivalent design tank and baffle with a hole is discretized to point form such that the fluid flowing through each point is evaluated and interpreted on a point graph generated with respect to each point located on the tank or baffle hole. The result obtained not only shows the effects of FSI as a function of turbulence kinetic energy per individual point but also the contour pressure field and velocity magnitude of the entire system.展开更多
Different Baffle designs usable in cylindrical and elliptical storage tanks carried by trucks often used for transporting inflammable liquid materials in Cameroon are investigated to evaluate their safest fluid sloshi...Different Baffle designs usable in cylindrical and elliptical storage tanks carried by trucks often used for transporting inflammable liquid materials in Cameroon are investigated to evaluate their safest fluid sloshing damping response during emergency braking where the magnitude of sloshing waves are the greatest. The uncontrolled fluid sloshing creates thrust on the walls of the tanks usually felt externally on the truck carrying the tank and capable of hindering driver’s effort to maintain steer ability and improve on safety during critical braking moments. The study first passes through COMSOL, to expose the safest margin of each Baffle type at instantaneous fluid pressure wave propagation initiated at a single phase to reflect sloshing in the storage tank during an emergency braking by the truck carrying the tank. The vivid results can be seen in the domain of Acoustic Iso-surface Pressure response;but also acoustic Pressure and Sound pressure response are seen automatically. Secondly, through an experimental finding in which fluid is forced to pass through each Baffle and the resistance to fluid flow is a measured as it’s the Baffle’s damping ability. Either, the fluid is lost through the Baffle and by determination of the surface load exerted on each Baffle due to the reaction of the residual fluid acting on the surface of each Baffle after some of it is Lost, the individual sloshing damping abilities are exposed. By comparing the Experimental outcome with the computational response obtained, an ideal Baffle design is proposed for cylindrical and elliptical tanks and considered to respond to abrupt braking more effciently. The application of the Baffle designs with an average multiple holes rather than the usual face centered proved to be more effcient in fluid sloshing as they provide a more uniformly distributed damping pressure during fluid sloshing in the tank thereby reducing the magnitude of forward thrust that can be created by the conventional Baffle type during emergency braking hence contributing to improving safety. Mindful of the human, material and environmental damages that an accident involving mobile petroleum storage tanks can course, this study is therefore of great significance for design optimization by petroleum storage tank manufacturing companies in Cameroon.展开更多
The present study is inscribed within the framework of the geotechnical characterization of the soils of the Santchou plain, their classification for employment as pavement subgrade, various identification tests were ...The present study is inscribed within the framework of the geotechnical characterization of the soils of the Santchou plain, their classification for employment as pavement subgrade, various identification tests were carried out on the samples. The results obtained showed that with a wide range of different grain sizes, the studied soils showed low content in clay grains and dominance of either sand grains or silt grains, this can be explaining how most of these soil are poorly graded. According to the USDA textural classification, the grain size distribution of these soils makes them to be classified as Silty Loam types to Sandy Loam types. Despite of their organic matter content which is less than 10%, according to their respective methylene blue values, the soils studied along the section should be mainly loamy soil of medium plasticity to clayed soil, therefore showing a sensibility of its behavior to variation of water content. That last one is confirmed by the consistency parameters of these soils which show intermediate plasticity to highly plastic. Also, the bearing capacity proposed by these soils at their respective optimum dry densities is relatively small, although most of these experimental CBR values of the studied soils are more important than the ones prescribed by the AASHTO Classification system for A5, A6, and A7 types, and the French Highway Earthworks Manual Classifications system (GTR) for the corresponding A2 and A3 types.展开更多
The present study is inscribed within the framework of the amelioration of the soils of the Santchou plain for employment as pavement subgrade. The bearing capacity proposed by these soils at their respective optimum ...The present study is inscribed within the framework of the amelioration of the soils of the Santchou plain for employment as pavement subgrade. The bearing capacity proposed by these soils at their respective optimum dry densities is relatively small, although most of these experimental California Bearing Ratio (CBR) values of the studied soils are more important than the ones prescribed by the American Association of State Highway and Transportation Officials Classification system (AASHTO) for A5, A6, and A7 types. The stabilization of this soils with lime has been chosen to improve the bearing capacity and by association, their resilient modulus. The results of this study show that the increase of lime content is not proportional with the increase of the expected mechanical performances. In fact, the literature explains that when the lime content arrives at an optimum, the mechanical parameters no longer increase, but decrease significantly. After this optimum, the soil stabilization no longer shows advantages in the increase of geo-mechanical properties of soils.展开更多
The bamboo stem, when mature 5 to 6 years, serves as a building material for modest houses and its marrow as packaging purposes. One of the strains related to the uses of bamboo stem is most often the compression towa...The bamboo stem, when mature 5 to 6 years, serves as a building material for modest houses and its marrow as packaging purposes. One of the strains related to the uses of bamboo stem is most often the compression towards the axial direction. The phenomenon of damage is very often observed during such loading. The present study on raffia aims to analyze this phenomenon through cyclical stresses as usual. From the results obtained, it was observed in the stress-strain plane, that the area of <span><span><span style="font-family:;" "="">the </span></span></span><span><span><span style="font-family:;" "="">hysteresis loops and the residual strain evolve with two parameters: the number of cycles and the stress peaks. The study of energy dissipation has shown that it evolves according to an exponential law as a function of the number of cycles. The distribution of the energy rate along a stem shows that the samples from the zone close to the base store twice (0.0412 MJ/m<sup>3</sup>) more energy than the samples taken from the top of the foliage (0.019 MJ/m<sup>3</sup>).</span></span></span>展开更多
文摘The prediction of the mechanical properties of wood and the evolution of its damage has been essential for its application in many fields such as bridges and houses construction, racks of trucks and so on. In more valorization of biomaterials following the example material wood arouses for a few years a?private interest on behalf of the populations. The experimental characterization?makes it possible to consider the mechanical properties local of Pericopsis elata (Assamela) according to various parameters (the wood turpentine, the orientation of wood fibers, water the content, the type of test …). From the?results, we evaluate the mechanical characteristics of Pericopsis elata (Assamela)?according to the three directions of Orthotropy. Then from the tests of load-discharge we measured the evolution of the damage using the variation of the Young modulus, which enabled us to note the reduction in the modulus of elasticity because of the damage following the three directions. Finally we noted a progressive and irreversible degradation of mechanical properties induced by the development of the microscopic cracks within material.
文摘Unsteady currents fluids flowing through a baffle with holes found in a mobile storage tank are complex to analyze. This study aims to evaluate the effects of fluid structure interactions (FSI) on baffles in tanks carried on mobile trucks that, more often than not, experience sloshing phenomenon engulfed by turbulences behaviors with respect to different motions of the truck. Mindful of the different types of baffles that are used in the tanks to limit sloshing wave activities and improve safety by allowing fluid to pass through carefully designed holes that are also placed in a specific pattern, the fluid structure interaction around a baffle with a hole is evaluated here through computing. Passing through the solver in COMSOL, an equivalent design tank and baffle with a hole is discretized to point form such that the fluid flowing through each point is evaluated and interpreted on a point graph generated with respect to each point located on the tank or baffle hole. The result obtained not only shows the effects of FSI as a function of turbulence kinetic energy per individual point but also the contour pressure field and velocity magnitude of the entire system.
文摘Different Baffle designs usable in cylindrical and elliptical storage tanks carried by trucks often used for transporting inflammable liquid materials in Cameroon are investigated to evaluate their safest fluid sloshing damping response during emergency braking where the magnitude of sloshing waves are the greatest. The uncontrolled fluid sloshing creates thrust on the walls of the tanks usually felt externally on the truck carrying the tank and capable of hindering driver’s effort to maintain steer ability and improve on safety during critical braking moments. The study first passes through COMSOL, to expose the safest margin of each Baffle type at instantaneous fluid pressure wave propagation initiated at a single phase to reflect sloshing in the storage tank during an emergency braking by the truck carrying the tank. The vivid results can be seen in the domain of Acoustic Iso-surface Pressure response;but also acoustic Pressure and Sound pressure response are seen automatically. Secondly, through an experimental finding in which fluid is forced to pass through each Baffle and the resistance to fluid flow is a measured as it’s the Baffle’s damping ability. Either, the fluid is lost through the Baffle and by determination of the surface load exerted on each Baffle due to the reaction of the residual fluid acting on the surface of each Baffle after some of it is Lost, the individual sloshing damping abilities are exposed. By comparing the Experimental outcome with the computational response obtained, an ideal Baffle design is proposed for cylindrical and elliptical tanks and considered to respond to abrupt braking more effciently. The application of the Baffle designs with an average multiple holes rather than the usual face centered proved to be more effcient in fluid sloshing as they provide a more uniformly distributed damping pressure during fluid sloshing in the tank thereby reducing the magnitude of forward thrust that can be created by the conventional Baffle type during emergency braking hence contributing to improving safety. Mindful of the human, material and environmental damages that an accident involving mobile petroleum storage tanks can course, this study is therefore of great significance for design optimization by petroleum storage tank manufacturing companies in Cameroon.
文摘The present study is inscribed within the framework of the geotechnical characterization of the soils of the Santchou plain, their classification for employment as pavement subgrade, various identification tests were carried out on the samples. The results obtained showed that with a wide range of different grain sizes, the studied soils showed low content in clay grains and dominance of either sand grains or silt grains, this can be explaining how most of these soil are poorly graded. According to the USDA textural classification, the grain size distribution of these soils makes them to be classified as Silty Loam types to Sandy Loam types. Despite of their organic matter content which is less than 10%, according to their respective methylene blue values, the soils studied along the section should be mainly loamy soil of medium plasticity to clayed soil, therefore showing a sensibility of its behavior to variation of water content. That last one is confirmed by the consistency parameters of these soils which show intermediate plasticity to highly plastic. Also, the bearing capacity proposed by these soils at their respective optimum dry densities is relatively small, although most of these experimental CBR values of the studied soils are more important than the ones prescribed by the AASHTO Classification system for A5, A6, and A7 types, and the French Highway Earthworks Manual Classifications system (GTR) for the corresponding A2 and A3 types.
文摘The present study is inscribed within the framework of the amelioration of the soils of the Santchou plain for employment as pavement subgrade. The bearing capacity proposed by these soils at their respective optimum dry densities is relatively small, although most of these experimental California Bearing Ratio (CBR) values of the studied soils are more important than the ones prescribed by the American Association of State Highway and Transportation Officials Classification system (AASHTO) for A5, A6, and A7 types. The stabilization of this soils with lime has been chosen to improve the bearing capacity and by association, their resilient modulus. The results of this study show that the increase of lime content is not proportional with the increase of the expected mechanical performances. In fact, the literature explains that when the lime content arrives at an optimum, the mechanical parameters no longer increase, but decrease significantly. After this optimum, the soil stabilization no longer shows advantages in the increase of geo-mechanical properties of soils.
文摘The bamboo stem, when mature 5 to 6 years, serves as a building material for modest houses and its marrow as packaging purposes. One of the strains related to the uses of bamboo stem is most often the compression towards the axial direction. The phenomenon of damage is very often observed during such loading. The present study on raffia aims to analyze this phenomenon through cyclical stresses as usual. From the results obtained, it was observed in the stress-strain plane, that the area of <span><span><span style="font-family:;" "="">the </span></span></span><span><span><span style="font-family:;" "="">hysteresis loops and the residual strain evolve with two parameters: the number of cycles and the stress peaks. The study of energy dissipation has shown that it evolves according to an exponential law as a function of the number of cycles. The distribution of the energy rate along a stem shows that the samples from the zone close to the base store twice (0.0412 MJ/m<sup>3</sup>) more energy than the samples taken from the top of the foliage (0.019 MJ/m<sup>3</sup>).</span></span></span>
