This present paper deals with a mathematical description of linear axial and torsional vibrations. The normal and tangential stress tensor components produced by axial-torsional deformations and vibrations in the prop...This present paper deals with a mathematical description of linear axial and torsional vibrations. The normal and tangential stress tensor components produced by axial-torsional deformations and vibrations in the propeller and intermediate shafts, under the influence of propeller-induced static and variable hydrodynamic excitations are also studied. The transfer matrix method related to the constant coefficients of differential equation solutions is used. The advantage of the latter as compared with a well-known method of transfer matrix associated with state vector is the possibility of reducing the number of multiplied matrices when adjacent shaft segments have the same material properties and diameters. The results show that there is no risk of buckling and confirm that the strength of the shaft line depends on the value of the static tangential stresses which is the most important component of the stress tensor.展开更多
A new static de Sitter solution with torsion in the model of de Sitter gauge theory of gravity is obtained. The torsion only contains Q（3）-symmetric tensor part according to irreducible decomposition. Some propertie...A new static de Sitter solution with torsion in the model of de Sitter gauge theory of gravity is obtained. The torsion only contains Q（3）-symmetric tensor part according to irreducible decomposition. Some properties of the new solution are discussed.展开更多
In this study, it shows how the main indicators of torsional vibrations of the crankshaft change when its materials change. In the study, the crankshaft of diesel engine with four cylinders in line was taken, in which...In this study, it shows how the main indicators of torsional vibrations of the crankshaft change when its materials change. In the study, the crankshaft of diesel engine with four cylinders in line was taken, in which the material is changing from steel to cast iron, due to the technological possibilities of production. For study of torsional vibration of crankshaft system, the construction of equivalent reduced scheme is carried. Reduced inertia moments of discs are determined for each crank of crankshaft, by receiving the impact of piston group and rod mass. Reduced rigidities of crank are determined by experimental method. The results show that the rigidity of crank for the same crankshaft varies up to 6%, while the change between crankshafts goes up 10%. At the end, frequency and vibration forms are calculated using Tole-Holxer method. From calculations, it results that the frequencies are 19% smaller, while the vibration forms varies slightly. In this case, the change of the materials leads to the first frequency in the area of engine rotations and it can worsen the level of torsional vibration, therefore, it should check the resonance areas and vibration amplitude.展开更多
The viscous pump,which has a rotor with a helical square channel,is studied experimentally.The non-dimen-sional channel curvature is taken to be about 0.1.Three types of torsion of the channel are made to investigate ...The viscous pump,which has a rotor with a helical square channel,is studied experimentally.The non-dimen-sional channel curvature is taken to be about 0.1.Three types of torsion of the channel are made to investigate the torsion effect on the flow characteristics.We measure the flux through the channel at a constant rotor speed by changing the pressures at the entrance and exit of the pump.We also observe the secondary flow at a cross-section of the channel.Some of the results obtained are shown as follows:The friction factor along the channel to get the same flux is large for large channel torsion at a constant rotation,and becomes small when the favorable rotation of the rotor to the flow is applied.As for the secondary flow in a cross-section,there appear several types of vortex.When there is no rotation,the secondary flow is almost a symmetric two-vortex type for small flux as is the ordinary Dean vortex,but it changes to a four-vortex type when the flux is large.The secondary flow becomes asymmetric as the rotation is applied.We have unsteady flow patterns at large flux and rotation.展开更多
We consider there is a vacancy in the plasma in the solar system,and calculate the vector potential produced by the magnetic field frozen in the plasma.The result shows that,in the vacancy,the vector potential produce...We consider there is a vacancy in the plasma in the solar system,and calculate the vector potential produced by the magnetic field frozen in the plasma.The result shows that,in the vacancy,the vector potential produced by the magnetic field frozen in the plasma is much less than the large scale cosmic vector potential.This means if our earth is in such a vacancy,the total vector potential on the surface of the earth is dominated by the cosmic magnetic vector potential,which gives a further support of the reliability of the limit on photon mass given by rotating torsion balance experiment [Phys.Rev.Lett.90(2003) 081801].展开更多
文摘This present paper deals with a mathematical description of linear axial and torsional vibrations. The normal and tangential stress tensor components produced by axial-torsional deformations and vibrations in the propeller and intermediate shafts, under the influence of propeller-induced static and variable hydrodynamic excitations are also studied. The transfer matrix method related to the constant coefficients of differential equation solutions is used. The advantage of the latter as compared with a well-known method of transfer matrix associated with state vector is the possibility of reducing the number of multiplied matrices when adjacent shaft segments have the same material properties and diameters. The results show that there is no risk of buckling and confirm that the strength of the shaft line depends on the value of the static tangential stresses which is the most important component of the stress tensor.
基金Supported by National Natural Science Foundation of China under Grant Nos.10775140,10975141Knowledge Innovation Funds of CAS under Grant No.KJCX3-SYW-S03
文摘A new static de Sitter solution with torsion in the model of de Sitter gauge theory of gravity is obtained. The torsion only contains Q（3）-symmetric tensor part according to irreducible decomposition. Some properties of the new solution are discussed.
文摘In this study, it shows how the main indicators of torsional vibrations of the crankshaft change when its materials change. In the study, the crankshaft of diesel engine with four cylinders in line was taken, in which the material is changing from steel to cast iron, due to the technological possibilities of production. For study of torsional vibration of crankshaft system, the construction of equivalent reduced scheme is carried. Reduced inertia moments of discs are determined for each crank of crankshaft, by receiving the impact of piston group and rod mass. Reduced rigidities of crank are determined by experimental method. The results show that the rigidity of crank for the same crankshaft varies up to 6%, while the change between crankshafts goes up 10%. At the end, frequency and vibration forms are calculated using Tole-Holxer method. From calculations, it results that the frequencies are 19% smaller, while the vibration forms varies slightly. In this case, the change of the materials leads to the first frequency in the area of engine rotations and it can worsen the level of torsional vibration, therefore, it should check the resonance areas and vibration amplitude.
文摘The viscous pump,which has a rotor with a helical square channel,is studied experimentally.The non-dimen-sional channel curvature is taken to be about 0.1.Three types of torsion of the channel are made to investigate the torsion effect on the flow characteristics.We measure the flux through the channel at a constant rotor speed by changing the pressures at the entrance and exit of the pump.We also observe the secondary flow at a cross-section of the channel.Some of the results obtained are shown as follows:The friction factor along the channel to get the same flux is large for large channel torsion at a constant rotation,and becomes small when the favorable rotation of the rotor to the flow is applied.As for the secondary flow in a cross-section,there appear several types of vortex.When there is no rotation,the secondary flow is almost a symmetric two-vortex type for small flux as is the ordinary Dean vortex,but it changes to a four-vortex type when the flux is large.The secondary flow becomes asymmetric as the rotation is applied.We have unsteady flow patterns at large flux and rotation.
文摘We consider there is a vacancy in the plasma in the solar system,and calculate the vector potential produced by the magnetic field frozen in the plasma.The result shows that,in the vacancy,the vector potential produced by the magnetic field frozen in the plasma is much less than the large scale cosmic vector potential.This means if our earth is in such a vacancy,the total vector potential on the surface of the earth is dominated by the cosmic magnetic vector potential,which gives a further support of the reliability of the limit on photon mass given by rotating torsion balance experiment [Phys.Rev.Lett.90(2003) 081801].
