Using the plate/shell elements in commercial software,accurate analysis of interlaminar initial damage in typical composite structures is still a challenging issue.To propose an accurate and efficient model for analys...Using the plate/shell elements in commercial software,accurate analysis of interlaminar initial damage in typical composite structures is still a challenging issue.To propose an accurate and efficient model for analysis of interlaminar initial damage,the following work is carried out:(A)A higher-order theory is firstly proposed by introducing the local Legendre polynomials,and then a novel shell element containing initial damage prediction is developed,which can directly predict transverse shear stresses without any postprocessing methods.Unknown variables at each node are independent of number of layers,so the proposed model is more efficient than the 3D-FEM.(B)Compression experiment is carried out to verify the capability of the proposed model.The results obtained from the proposed model are in good agreement with experimental data.(C)Several examples have been analyzed to further assess the capability of the proposed model by comparing to the 3D-FEM results.Moreover,accuracy and efficiency have been evaluated in different damage criterion by comparing with the selected models.The numerical results show that the proposed model can well predict the initial interlaminar damage as well as other damage.Finally,the model is implemented with UEL subroutine,so that the present approach can be readily utilized to analyze the initial damage in typical composite structures.展开更多
There recently has been increasing interest in the research and application of the rotational Doppler effect(RDE),which paves a promising way to detect rotating objects remotely.In order to obtain more information abo...There recently has been increasing interest in the research and application of the rotational Doppler effect(RDE),which paves a promising way to detect rotating objects remotely.In order to obtain more information about the rotating object from the rotational Doppler signal,composite vortex beams by coaxial superposition of orbital angular momentum(OAM)modes are often used as the probe beam.However,to the best of our knowledge,the RDE of composite vortex beams with arbitrary OAM spectra has not yet been comprehensively studied.In this paper,the correspondence between the OAM spectrum of a probe beam and the frequency spectrum of a rotational Doppler signal is theoretically analyzed.It is explicitly revealed that the RDE frequency spectrum of scattered light is related to the product of two autocorrelation functions:one from the OAM spectrum of probe beam and the other from the spiral spectrum of rotating object.On the basis of this relation,one can regulate the RDE frequency spectrum on demand via tailoring the OAM spectrum of the probe beam.As a proof of concept we design a special composite vortex beam to eliminate the broadening of the RDE spectrum induced by misalignment.These findings are of practical value in applications such as remote sensing and optical metrology.展开更多
The transverse stretching vibration of thick sandwich plates,which is attributed to largely different stiffness at the adjacent layers,is a challenging issue,and efficient approach for such issue is less reported in t...The transverse stretching vibration of thick sandwich plates,which is attributed to largely different stiffness at the adjacent layers,is a challenging issue,and efficient approach for such issue is less reported in the published literature.Thus,natural frequencies corresponding to stretching vibration modes are generally neglected in engineering design,which might impact structural safety as frequencies of the exciting force are close to transverse stretching vibration frequencies.This paper proposes an alternative higher-order model for dynamic analysis corresponding to the higher-order vibration modes.The proposed model is classified in the displacement-based equivalent single-layer theory,as the number of displacement parameters in the proposed model is independent of the layer number.The continuity of displacements and transverse shear stresses can be fulfilled at the interfaces between the adjacent layers of structures.To demonstrate the capability of the proposed model,typical examples are analyzed by utilizing the proposed model,the threedimensional finite element method and the chosen higher-order models.By comparing with the exact three-dimensional elasticity solutions,it is found that the proposed model can yield more accurate natural frequencies corresponding to the higher-order displacement modes than the selected models.Moreover,the factors influencing reasonable prediction of the higher-order frequencies are investigated in detail,which can provide a reference for the accurate prediction of the higher-order frequencies.展开更多
The resolution of the spatial light modulator(SLM)screen and the encoding algorithm of the computer-generated hologram are the primary limiting factors in the generation of large topological charge vortex beams.This p...The resolution of the spatial light modulator(SLM)screen and the encoding algorithm of the computer-generated hologram are the primary limiting factors in the generation of large topological charge vortex beams.This paper attempts to solve these problems by improving both the hardware and the algorithm.Theoretically,to overcome the limitations of beam waist radius,the amplitude profile function of large topological charge Laguerre–Gaussian(LG)beam is properly improved.Then,an experimental system employing a 4K phase-only SLM is set up,and the LG beams with topological charge up to 1200 are successfully generated.Furthermore,we discuss the effect of different beam waist radii on the generation of LG beams.Additionally,the function of the LG beam is further improved to generate an LG beam with a topological charge as high as1400.Our results set a new benchmark for generating large topological charge vortex beams,which can be widely used in precise measurement,sensing,and communication.展开更多
We propose a method for detecting the symmetry of rotating patterns based on the rotational Doppler effect(RDE)of light.The basic mechanisms of the RDE are introduced,and the spiral harmonic distribution of rotating p...We propose a method for detecting the symmetry of rotating patterns based on the rotational Doppler effect(RDE)of light.The basic mechanisms of the RDE are introduced,and the spiral harmonic distribution of rotating patterns is analyzed.By irradiating the rotating pattern using a superimposed optical vortex and analyzing the amplitude of the RDE signal,the spiral harmonic distribution of the pattern can be measured,and then its symmetry can be detected.We demonstrate this method experimentally by using patterns with different symmetries and shapes.As the method does not need to receive the scattered light completely and accurately,it promises potential application in detecting symmetrical rotating objects at a long distance.展开更多
The NiCrAlTi coatings free of N and with N incorporations were deposited on austenitic stainless steel304 L by magnetron sputtering in Ar and in gas mixture of Ar and N2,respectively.The N incorporated in the coatings...The NiCrAlTi coatings free of N and with N incorporations were deposited on austenitic stainless steel304 L by magnetron sputtering in Ar and in gas mixture of Ar and N2,respectively.The N incorporated in the coatings existed as nitride precipitates(from^3 vol.%to^17 vol.%)after vacuum annealing.All the NiCrAlTi coatings,whatever free of N or with N incorporations,exhibited better resistance against cavitation erosion than ion plating Ti N coating and the substrate 304 L in ultrasonic cavitation tests.The NiCrAlTi coating free of N incorporation presents superior cavitation erosion resistance.However,the nitrogen incorporation within the NiCrAlTi coatings showed negative effects on the resistance against cavitation erosion.展开更多
基金supported by the National Natural Science Foundation of China(No.12172295)SKLLIM1902the Natural Science Foundation in Shaanxi Province,China(No.2019JQ-909)。
文摘Using the plate/shell elements in commercial software,accurate analysis of interlaminar initial damage in typical composite structures is still a challenging issue.To propose an accurate and efficient model for analysis of interlaminar initial damage,the following work is carried out:(A)A higher-order theory is firstly proposed by introducing the local Legendre polynomials,and then a novel shell element containing initial damage prediction is developed,which can directly predict transverse shear stresses without any postprocessing methods.Unknown variables at each node are independent of number of layers,so the proposed model is more efficient than the 3D-FEM.(B)Compression experiment is carried out to verify the capability of the proposed model.The results obtained from the proposed model are in good agreement with experimental data.(C)Several examples have been analyzed to further assess the capability of the proposed model by comparing to the 3D-FEM results.Moreover,accuracy and efficiency have been evaluated in different damage criterion by comparing with the selected models.The numerical results show that the proposed model can well predict the initial interlaminar damage as well as other damage.Finally,the model is implemented with UEL subroutine,so that the present approach can be readily utilized to analyze the initial damage in typical composite structures.
基金National Natural Science Foundation of China(61805283,62173342)。
文摘There recently has been increasing interest in the research and application of the rotational Doppler effect(RDE),which paves a promising way to detect rotating objects remotely.In order to obtain more information about the rotating object from the rotational Doppler signal,composite vortex beams by coaxial superposition of orbital angular momentum(OAM)modes are often used as the probe beam.However,to the best of our knowledge,the RDE of composite vortex beams with arbitrary OAM spectra has not yet been comprehensively studied.In this paper,the correspondence between the OAM spectrum of a probe beam and the frequency spectrum of a rotational Doppler signal is theoretically analyzed.It is explicitly revealed that the RDE frequency spectrum of scattered light is related to the product of two autocorrelation functions:one from the OAM spectrum of probe beam and the other from the spiral spectrum of rotating object.On the basis of this relation,one can regulate the RDE frequency spectrum on demand via tailoring the OAM spectrum of the probe beam.As a proof of concept we design a special composite vortex beam to eliminate the broadening of the RDE spectrum induced by misalignment.These findings are of practical value in applications such as remote sensing and optical metrology.
基金co-supported by the National Natural Science Foundation of China(No.12172295)SKLLIM1902the Natural Science Foundation in Shaanxi Province,China(No.2019JQ-909)。
文摘The transverse stretching vibration of thick sandwich plates,which is attributed to largely different stiffness at the adjacent layers,is a challenging issue,and efficient approach for such issue is less reported in the published literature.Thus,natural frequencies corresponding to stretching vibration modes are generally neglected in engineering design,which might impact structural safety as frequencies of the exciting force are close to transverse stretching vibration frequencies.This paper proposes an alternative higher-order model for dynamic analysis corresponding to the higher-order vibration modes.The proposed model is classified in the displacement-based equivalent single-layer theory,as the number of displacement parameters in the proposed model is independent of the layer number.The continuity of displacements and transverse shear stresses can be fulfilled at the interfaces between the adjacent layers of structures.To demonstrate the capability of the proposed model,typical examples are analyzed by utilizing the proposed model,the threedimensional finite element method and the chosen higher-order models.By comparing with the exact three-dimensional elasticity solutions,it is found that the proposed model can yield more accurate natural frequencies corresponding to the higher-order displacement modes than the selected models.Moreover,the factors influencing reasonable prediction of the higher-order frequencies are investigated in detail,which can provide a reference for the accurate prediction of the higher-order frequencies.
基金supported by the National Natural Science Foundation of China(Nos.62173342 and 61805283)the Key Research Projects of Foundation Strengthening Program(No.2019-JCJQ-ZD)。
文摘The resolution of the spatial light modulator(SLM)screen and the encoding algorithm of the computer-generated hologram are the primary limiting factors in the generation of large topological charge vortex beams.This paper attempts to solve these problems by improving both the hardware and the algorithm.Theoretically,to overcome the limitations of beam waist radius,the amplitude profile function of large topological charge Laguerre–Gaussian(LG)beam is properly improved.Then,an experimental system employing a 4K phase-only SLM is set up,and the LG beams with topological charge up to 1200 are successfully generated.Furthermore,we discuss the effect of different beam waist radii on the generation of LG beams.Additionally,the function of the LG beam is further improved to generate an LG beam with a topological charge as high as1400.Our results set a new benchmark for generating large topological charge vortex beams,which can be widely used in precise measurement,sensing,and communication.
基金supported by the National Natural Science Foundation of China(Nos.11772001 and 61805283)Key Research Projects of Foundation Strengthening Program(No.2019-JCJQ-ZD)。
文摘We propose a method for detecting the symmetry of rotating patterns based on the rotational Doppler effect(RDE)of light.The basic mechanisms of the RDE are introduced,and the spiral harmonic distribution of rotating patterns is analyzed.By irradiating the rotating pattern using a superimposed optical vortex and analyzing the amplitude of the RDE signal,the spiral harmonic distribution of the pattern can be measured,and then its symmetry can be detected.We demonstrate this method experimentally by using patterns with different symmetries and shapes.As the method does not need to receive the scattered light completely and accurately,it promises potential application in detecting symmetrical rotating objects at a long distance.
基金the National Key Research and Development Program of China(No.2018YFB2003601)。
文摘The NiCrAlTi coatings free of N and with N incorporations were deposited on austenitic stainless steel304 L by magnetron sputtering in Ar and in gas mixture of Ar and N2,respectively.The N incorporated in the coatings existed as nitride precipitates(from^3 vol.%to^17 vol.%)after vacuum annealing.All the NiCrAlTi coatings,whatever free of N or with N incorporations,exhibited better resistance against cavitation erosion than ion plating Ti N coating and the substrate 304 L in ultrasonic cavitation tests.The NiCrAlTi coating free of N incorporation presents superior cavitation erosion resistance.However,the nitrogen incorporation within the NiCrAlTi coatings showed negative effects on the resistance against cavitation erosion.
