Non-planar and non-linear second sound wave are experimentally investigated in an open He Ⅱ bath.It is found that second sound wave characterized by a negative tail part in an open He Ⅱ bath is different from that p...Non-planar and non-linear second sound wave are experimentally investigated in an open He Ⅱ bath.It is found that second sound wave characterized by a negative tail part in an open He Ⅱ bath is different from that propagating through a channel,and the shape of the negative tail part of second sound wave varies at different location in an open He Ⅱ bath.Theoretical consideration is also carried out based on two-fluid model and vortex evolution equation.It is found that experimental and theoretical results agree rather well with each other.Second sound wave may develop into the thermal shock wave provided that the heat Hux is large.展开更多
This study presents an integrated method suitable for off-axis tension and compression testing in unidirectional composites,and its application to the testing of in-plane shear characterization.A new rotating-grip tes...This study presents an integrated method suitable for off-axis tension and compression testing in unidirectional composites,and its application to the testing of in-plane shear characterization.A new rotating-grip test fixture,incorporating the attractive features of the existing pinned-end fixture and hydraulic wedge grips,has been developed.The proposed gripping system consists of two sets of jaw faces,each with a pair of self-aligning bearings that allows for loading in the axial and radial directions.Finite element analysis and experiments were performed to evaluate the effectiveness of the rotating-grip test fixture.Results from numerical calculations show that this method reduces stress concentrations near the end and produces relatively uniform stress distributions in the specimen gage section.Mechanical testing results show a considerable increase in the measured shear properties of composites,compared with the existing end grip systems.The results indicated that the new test fixture is significantly better than the conventional fixture,and is also comparable to the method of the oblique end-tab for off-axis testing.展开更多
基金Supported by National Natural Science Foundation of China under Grant No.59876018.
文摘Non-planar and non-linear second sound wave are experimentally investigated in an open He Ⅱ bath.It is found that second sound wave characterized by a negative tail part in an open He Ⅱ bath is different from that propagating through a channel,and the shape of the negative tail part of second sound wave varies at different location in an open He Ⅱ bath.Theoretical consideration is also carried out based on two-fluid model and vortex evolution equation.It is found that experimental and theoretical results agree rather well with each other.Second sound wave may develop into the thermal shock wave provided that the heat Hux is large.
文摘This study presents an integrated method suitable for off-axis tension and compression testing in unidirectional composites,and its application to the testing of in-plane shear characterization.A new rotating-grip test fixture,incorporating the attractive features of the existing pinned-end fixture and hydraulic wedge grips,has been developed.The proposed gripping system consists of two sets of jaw faces,each with a pair of self-aligning bearings that allows for loading in the axial and radial directions.Finite element analysis and experiments were performed to evaluate the effectiveness of the rotating-grip test fixture.Results from numerical calculations show that this method reduces stress concentrations near the end and produces relatively uniform stress distributions in the specimen gage section.Mechanical testing results show a considerable increase in the measured shear properties of composites,compared with the existing end grip systems.The results indicated that the new test fixture is significantly better than the conventional fixture,and is also comparable to the method of the oblique end-tab for off-axis testing.
