The Experts below are selected from a list of 37650 Experts worldwide ranked by ideXlab platform
Ravindra Jayaratne - One of the best experts on this subject based on the ideXlab platform.
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Hydraulic roughness – links between Manning’s coefficient, Nikuradse’s equivalent sand roughness and bed grain size
2010Co-Authors: Martin John Marriott, Ravindra JayaratneAbstract:This paper presents and reviews the connection between Manning‘s n and Nikuradse‘s equivalent sand roughness ks, which is well established for pipe flow in the rough turbulent region. The link with bed grain size is less clear, and a survey is made covering pipelines and channels, river and coastal engineering. It is concluded that whilst the equivalent n and ks values are useful alternatives for sewer and culvert design, the link between roughness parameters and bed grain size for river and coastal purposes should be treated with more caution, particularly because the hydraulic resistance is likely to include not only a skin Friction Element which depends on the grain size, but also a form drag component.
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hydraulic roughness links between manning s coefficient nikuradse s equivalent sand roughness and bed grain size
2010Co-Authors: Martin John Marriott, Ravindra JayaratneAbstract:This paper presents and reviews the connection between Manning‘s n and Nikuradse‘s equivalent sand roughness ks, which is well established for pipe flow in the rough turbulent region. The link with bed grain size is less clear, and a survey is made covering pipelines and channels, river and coastal engineering. It is concluded that whilst the equivalent n and ks values are useful alternatives for sewer and culvert design, the link between roughness parameters and bed grain size for river and coastal purposes should be treated with more caution, particularly because the hydraulic resistance is likely to include not only a skin Friction Element which depends on the grain size, but also a form drag component.
Martin John Marriott - One of the best experts on this subject based on the ideXlab platform.
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Hydraulic roughness – links between Manning’s coefficient, Nikuradse’s equivalent sand roughness and bed grain size
2010Co-Authors: Martin John Marriott, Ravindra JayaratneAbstract:This paper presents and reviews the connection between Manning‘s n and Nikuradse‘s equivalent sand roughness ks, which is well established for pipe flow in the rough turbulent region. The link with bed grain size is less clear, and a survey is made covering pipelines and channels, river and coastal engineering. It is concluded that whilst the equivalent n and ks values are useful alternatives for sewer and culvert design, the link between roughness parameters and bed grain size for river and coastal purposes should be treated with more caution, particularly because the hydraulic resistance is likely to include not only a skin Friction Element which depends on the grain size, but also a form drag component.
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hydraulic roughness links between manning s coefficient nikuradse s equivalent sand roughness and bed grain size
2010Co-Authors: Martin John Marriott, Ravindra JayaratneAbstract:This paper presents and reviews the connection between Manning‘s n and Nikuradse‘s equivalent sand roughness ks, which is well established for pipe flow in the rough turbulent region. The link with bed grain size is less clear, and a survey is made covering pipelines and channels, river and coastal engineering. It is concluded that whilst the equivalent n and ks values are useful alternatives for sewer and culvert design, the link between roughness parameters and bed grain size for river and coastal purposes should be treated with more caution, particularly because the hydraulic resistance is likely to include not only a skin Friction Element which depends on the grain size, but also a form drag component.
Leif Kari - One of the best experts on this subject based on the ideXlab platform.
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Nonlinear Isolator Dynamics at Finite Deformations: An Effective Hyperelastic, Fractional Derivative, Generalized Friction Model
Nonlinear Dynamics, 2003Co-Authors: M. Sjoberg, Leif KariAbstract:In presenting a nonlinear dynamic model of a rubber vibration isolator, the quasistatic and dynamic motion influences on the force response are investigated within the time and frequency domain. It is found that the dynamic stiffness at the frequency of a harmonic displacement excitation, superimposed upon the long term isolator response, is strongly dependent on static precompression, dynamic amplitude and frequency. The problems of simultaneously modelling the elastic, viscoelastic and Friction forces are removed by additively splitting them, modelling the elastic force response by a nonlinear, shape factor based approach, displaying results that agree with those of a neo-Hookean hyperelastic isolator at a long term precompression. The viscoelastic force is modeled by a fractional derivative Element, while the Friction force governs from a generalized Friction Element displaying a smoothed Coulomb force. A harmonic displacement excitation is shown to result in a force response containing the excitation frequency and its every other higher-order harmonic, while using a linearized elastic force response model, whereas all higher-order harmonics are present for the fully nonlinear case. It is furthermore found that the dynamic stiffness magnitude increases with static precompression and frequency, while decreasing with dynamic excitation amplitude-eventually increasing at the highest amplitudes due to nonlinear elastic effects-with its loss angle displaying a maximum at an intermediate amplitude. Finally, the dynamic stiffness at a static precompression, using a linearized elastic force response model, is shown to agree with the fully nonlinear model except at the highest dynamic amplitudes.
M. Sjoberg - One of the best experts on this subject based on the ideXlab platform.
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Nonlinear Isolator Dynamics at Finite Deformations: An Effective Hyperelastic, Fractional Derivative, Generalized Friction Model
Nonlinear Dynamics, 2003Co-Authors: M. Sjoberg, Leif KariAbstract:In presenting a nonlinear dynamic model of a rubber vibration isolator, the quasistatic and dynamic motion influences on the force response are investigated within the time and frequency domain. It is found that the dynamic stiffness at the frequency of a harmonic displacement excitation, superimposed upon the long term isolator response, is strongly dependent on static precompression, dynamic amplitude and frequency. The problems of simultaneously modelling the elastic, viscoelastic and Friction forces are removed by additively splitting them, modelling the elastic force response by a nonlinear, shape factor based approach, displaying results that agree with those of a neo-Hookean hyperelastic isolator at a long term precompression. The viscoelastic force is modeled by a fractional derivative Element, while the Friction force governs from a generalized Friction Element displaying a smoothed Coulomb force. A harmonic displacement excitation is shown to result in a force response containing the excitation frequency and its every other higher-order harmonic, while using a linearized elastic force response model, whereas all higher-order harmonics are present for the fully nonlinear case. It is furthermore found that the dynamic stiffness magnitude increases with static precompression and frequency, while decreasing with dynamic excitation amplitude-eventually increasing at the highest amplitudes due to nonlinear elastic effects-with its loss angle displaying a maximum at an intermediate amplitude. Finally, the dynamic stiffness at a static precompression, using a linearized elastic force response model, is shown to agree with the fully nonlinear model except at the highest dynamic amplitudes.
Walter Dipl Ing Krenkel - One of the best experts on this subject based on the ideXlab platform.
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safety braking device for elevator
2001Co-Authors: Walter Dipl Ing Krenkel, Ralph RenzAbstract:A Friction Element for use in a safety braking device for braking elevators co-operating with at least one elevator guide rail. The Friction Element has at least one Friction surface that can be pressed against the guide rail to decelerate the elevator. The Friction Element is formed of a fiber-reinforced, ceramic composite material, containing silicon carbide and carbon with carbon fibers as reinforcing components. Preferably, the composite material is formed by a matrix of silicon carbide and carbon and the reinforcing component are exclusively carbon fibers with a minimum length of 10 mm and the volume content of carbon fibers in the Friction Element being between 30% and 70%.
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method of manufacturing a Friction Element
1995Co-Authors: Walter Dipl Ing Krenkel, Richard KochendörferAbstract:Disclosed is a method for manufacturing a Friction Element designed for Frictional contact with a body and for use, in particular, in brakes or clutches. In the method, a porous carbon block, which approximately matches the shape of the end of the abrasion unit, is produced, liquid silicon is infiltrated into the pores of the carbon block, and the block is ceramized by initiating a chemical reaction to form silicon carbide. In order to further fashion a Friction Element of this kind to increase its resistance to thermal stresses and so that it is also easy to manufacture, the porous carbon block is shaped, before the silicon is infiltrated into it, in such a way that cavities and/or recesses are formed in certain internal and/or external zones for cooling and/or reinforcement purposes, the cavities and/or recesses retaining essentially the same shape and size after ceramization.
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verfahren zur herstellung einer reibeinheit mittels infiltration eines porosen kohlenstoffkorpers mit flussigem silizium
1994Co-Authors: Walter Dipl Ing Krenkel, Richard Prof Dip KochendoerferAbstract:Proposed is a method of manufacturing a Friction Element designed for Frictional contact with a body and for use, in particular, in brakes or clutches. The method calls for a porous carbon block to be produced which approximately matches the shape of the end of the abrasion unit, liquid silicon to be infiltrated into the pores of the carbon block and the block to be ceramized by initiating a chemical reaction to form silicon carbide. In order to further fashion a Friction Element of this kind to increase its resistance to thermal stresses and so that it is also easy to manufacture, the porous carbon block is shaped, before the silicon is infiltrated into it, in such a way that cavities and/or recesses are formed in certain internal and/or external zones for cooling and/or reinforcement purposes, the cavities and/or recesses retaining essentially the same shape and size after ceramization.
