This paper comprehensively investigates the buckling load and the stability of a planar linear array deployable structure composed of scissor-like element(SLE)under compression.At present,the researches on deployable ...This paper comprehensively investigates the buckling load and the stability of a planar linear array deployable structure composed of scissor-like element(SLE)under compression.At present,the researches on deployable structure are mainly focused on configuration design and dynamics characteristics of the mechanisms,but less on structural instability.In fact,when the external load exceeds the structural critical load value,the deployable structure will be permanently deformed or even collapse directly and no longer have any bearing capacity.To address this issue,a new stability model is derived using linear elastic analysis method and substructure method to evaluate the buckling characteristics of the deployable structure with n SLEs when it is carried out in space,which can accurately obtain the structural instability load and can be used quantitatively to optimize the structure for making it have the most stable configuration.In addition,the effects of the number of elements,the length,material properties and flexibility of the bar,and the deployment degree on the buckling of the scissor deployable structure are investigated,and the results of the theoretical analysis are compared with simulation and analytical results,respectively,confirming that the proposed stability model not only is able to effectively predict the structural instability load but also determine which part of the deployable structure is unstable.It can be concluded that the stability of the deployable structure gradually decreases with the increase of the number of elements or the bar flexibility.In the calculation process,the critical load of each sub-element should be considered,and the minimum value of the critical loads of all subunits can be regarded as the instability load of the whole structure.展开更多
The ultimate feature size is key in ultrafast laser material processing.A capacity to substantially exceed optical limits and to structure below 100 nm is essential to advance ultrafast processing into the field of me...The ultimate feature size is key in ultrafast laser material processing.A capacity to substantially exceed optical limits and to structure below 100 nm is essential to advance ultrafast processing into the field of metamaterials.Such achievement requires combining the control of optical near-fields and of material reactions while preserving the flexibility of long working distances,compatible with a mature laser process.Using subpicosecond and picosecond nondiffractive Bessel beams,we demonstrate unprecedented feature sizes below a hundredth of the incident 1-um wavelength over an extended focus depth of tens of micrometers.Record features sizes,down to 7 nm,result from self-generated near-field light components initiated by cavities induced by far-field radiation in a back-surface illumination geometry.This sustains the generation of more confined near-field evanescent components along the laser scan with a nanometer pitch,perpendicular to the incident field direction,driving a superresolved laser structuring process via local thermal ablation.The near-field pattern is replicated with high robustness,advancing toward a 10-nm nanoscribing tool with a micrometer-sized laser pen.The process is controllable by the field orientation.The nondiffractive irradiation develops evanescent fields over the focusing length,resulting in high-aspect-ratio trenching with a nanometer section and a micrometer depth.Higher energy doses trigger the self-organization of quasi-periodic patterns seeded by spatially modulated scattering,similarly to optical modelocking.A predictive multipulse simulation method validates the far-field-induced near-field electromagnetic scenario of void nanochannel growth and replication,indicating the processing range and resolution on the surface and in the depth.展开更多
基金the National Natural Science Foundation of China(Grant No.51175422)the Natural Science Basic Research Plan in Shaanxi Province of China(Grant No.2019JQ-753)the Ph D Research Startup Foundation of Xi’an University of Technology(Grant No.102-451119003)。
文摘This paper comprehensively investigates the buckling load and the stability of a planar linear array deployable structure composed of scissor-like element(SLE)under compression.At present,the researches on deployable structure are mainly focused on configuration design and dynamics characteristics of the mechanisms,but less on structural instability.In fact,when the external load exceeds the structural critical load value,the deployable structure will be permanently deformed or even collapse directly and no longer have any bearing capacity.To address this issue,a new stability model is derived using linear elastic analysis method and substructure method to evaluate the buckling characteristics of the deployable structure with n SLEs when it is carried out in space,which can accurately obtain the structural instability load and can be used quantitatively to optimize the structure for making it have the most stable configuration.In addition,the effects of the number of elements,the length,material properties and flexibility of the bar,and the deployment degree on the buckling of the scissor deployable structure are investigated,and the results of the theoretical analysis are compared with simulation and analytical results,respectively,confirming that the proposed stability model not only is able to effectively predict the structural instability load but also determine which part of the deployable structure is unstable.It can be concluded that the stability of the deployable structure gradually decreases with the increase of the number of elements or the bar flexibility.In the calculation process,the critical load of each sub-element should be considered,and the minimum value of the critical loads of all subunits can be regarded as the instability load of the whole structure.
基金The National Key R&D Program of China(2022YFB4600200)the Natural Science Basic Research Program of Shaanxi Province(2022JQ-648)partially supported by the French National Research Agency(ANR)with grants ANR-19-CE30-0036 and ANR-21-CE08-0005.
文摘The ultimate feature size is key in ultrafast laser material processing.A capacity to substantially exceed optical limits and to structure below 100 nm is essential to advance ultrafast processing into the field of metamaterials.Such achievement requires combining the control of optical near-fields and of material reactions while preserving the flexibility of long working distances,compatible with a mature laser process.Using subpicosecond and picosecond nondiffractive Bessel beams,we demonstrate unprecedented feature sizes below a hundredth of the incident 1-um wavelength over an extended focus depth of tens of micrometers.Record features sizes,down to 7 nm,result from self-generated near-field light components initiated by cavities induced by far-field radiation in a back-surface illumination geometry.This sustains the generation of more confined near-field evanescent components along the laser scan with a nanometer pitch,perpendicular to the incident field direction,driving a superresolved laser structuring process via local thermal ablation.The near-field pattern is replicated with high robustness,advancing toward a 10-nm nanoscribing tool with a micrometer-sized laser pen.The process is controllable by the field orientation.The nondiffractive irradiation develops evanescent fields over the focusing length,resulting in high-aspect-ratio trenching with a nanometer section and a micrometer depth.Higher energy doses trigger the self-organization of quasi-periodic patterns seeded by spatially modulated scattering,similarly to optical modelocking.A predictive multipulse simulation method validates the far-field-induced near-field electromagnetic scenario of void nanochannel growth and replication,indicating the processing range and resolution on the surface and in the depth.
