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激光微弯曲成形机理的数值研究 总被引:9,自引:2,他引:7
利用自行研制的含热传导、冲击动力学大、变形有限元程序 ,模拟了小尺寸梁在脉冲激光加热条件下的变形过程。在此基础上 ,利用商用程序模拟了冷却及残余应力的产生 ,研究了激光参数 (强度及分布 )等对于微弯曲的影响。数值模拟结果与文献中的实验观察相吻合 相似文献
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基板预变形下激光立体成形直薄壁件应力和变形的有限元模拟 总被引:1,自引:0,他引:1
针对单道多层的直薄件激光立体成形过程,建立了基板预变形和无预变形条件下的3D参数化有限元模型,进行了应力和变形的瞬时热弹塑性有限元模拟分析。模拟结果表明,基板预变形处理影响成形件应力和变形的分布与大小,并可减轻基板的翘曲变形。预变形下基板下表面具有初始拉应力点的残余应力值比无预变形要小,基板与熔覆层接触的界面中间位置残余应力也小于无预变形的情况,直薄壁件最大残余压应力所在位置也发生变化。在两模型中,熔覆层两侧边缘位置变形严重,而中间位置变形较小。熔覆层首层的沉积对基板变形量影响最大,后续熔覆层的沉积对基板变形量影响程度逐渐减小并最终趋于稳定。成形前对基板进行适当的预变形处理可以有效控制成形件变形和改善应力分布。 相似文献
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为降低激光沉积修复钛合金基体的残余应力与变形,采用有限元参数化设计语言研究了不同激光扫描路径对修复基体残余应力与变形的影响,模拟了不同扫描路径下修复基体残余应力及不同修复层残余应力的分布情况,并对原因进行了分析。结果表明:不同扫描路径下基体两端残余应力值较大,修复层残余应力值两端高,中间低,采用层间交错扫描路径时,各修复层残余应力值大小和波动幅度降低,修复件表面平整度值最小。采用压痕法对不同扫描方式下修复件表面残余应力进行了测定,得到了不同扫描路径下基体变形曲线,并与模拟结果进行了比较,两者吻合较好,为提高激光修复质量提供了参考依据。 相似文献
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实验研究了不同的光斑间距对SUS304不锈钢板激光冲击的变形影响,并用ABAQUS软件进行了有限元仿真分析.实验和仿真结果均表明:随着光斑间距的减小,受冲区域更加平整.通过数值模拟可优化激光冲击的相关参数,预测板料变形. 相似文献
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脉冲激光冲击LD31薄板变形的实验和数值模拟 总被引:3,自引:0,他引:3
激光冲击板料变形是利用高能脉冲激光和材料相互作用诱导的高幅冲击波的力效应使板料产生塑性变形的新技术 ,本文利用Nd :Glass脉冲激光对厚度为 0 .8mm的LD31薄板进行激光冲击变形实验。所用激光参数为 :脉冲能量 15~ 30J,脉冲宽度 2 5ns ,光斑直径Φ8mm。利用ABAQUS软件对激光冲击下板料的变形过程进行了数值模拟 ,建立了激光冲击波加载的数学模型 ,探索激光冲击的主要参数和板料变形之间的相互关系 ,为激光冲击变形工艺参数的优化、板料变形的理论分析 ,实现大面积金属板料的柔性激光冲压成形提供依据。 相似文献
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为了使TMT三镜系统具有跟踪瞄准功能,同时可以校正由于重力引起的结构变形,设计一个大型的Stewart平台来完成三镜的Tilt调整。根据初始参数对并联机构进行了位置反解的计算,并分别对支腿轴向力和刚度进行了建模,最后使用了Matlab进行优化计算,得出一组最优解。根据所求出的最优解使用ANSYS建立了三镜系统的参数化模型,并与Matlab联合仿真,对三镜系统的各个工况进行了有限元模拟。仿真得到三镜各个工作位置时的支腿的伸长量、重力下的变形、第一阶模态值以及六根支腿内力。模拟结果显示,最终设计的Stewart平台支腿的最大变形量为0.813 mm,与优化前的模型相比下降了20%;第一阶模态最小值为16.7 Hz,与优化前的模型相比上升了18%;六根支腿的轴向力最大值为27 219 N,相比优化前下降了15.9%。 相似文献
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不锈钢-碳钢层合板激光弯曲试验研究 总被引:4,自引:2,他引:2
层状金属复合板以优良的材料和结构性能在舰船、汽车和飞行器等装备中显示了广阔的应用前景。为研究工艺因数对层状金属复合板激光弯曲成形的影响,以不锈钢-碳钢层合板为研究对象,对这种层状金属复合板的激光弯曲角度和规律进行了系统的试验研究。结果表明,不锈钢-碳钢层合板和不锈钢板激光弯曲存在共性,弯曲角度随着激光功率增加而增大,随着扫描速度增加而减小,随着扫描次数增加而增大,随着板厚增大而减小。同时二者也存在差异;随着不锈钢-碳钢层合板宽度的增加,弯曲角度先减小后增大;在相同工艺条件下,不锈钢-碳钢层合板弯曲角度大于不锈钢板的弯曲角度,并在一次固定安装下获得85.6°这一接近直角的极限弯曲角度。 相似文献
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本文对取向硅钢片降低铁损的激光加工过程进行了热弹塑性分析。通过热传导分析和弹塑性应力分析,预测了在激光加工中因不合理的热加工工艺而引起的涂层破坏问题和弯曲变形问题,并确定出了合理的工艺参数范围:既能确保铁损下降,又能防止涂层破坏和弯曲变形,保证激光加工质量。 相似文献
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Ning An August G. Domel Jinxiong Zhou Ahmad Rafsanjani Katia Bertoldi 《Advanced functional materials》2020,30(6)
Kirigami—the Japanese art of cutting paper—has recently inspired the design of highly stretchable and morphable mechanical metamaterials that can be easily realized by embedding an array of cuts into a sheet. This study focuses on thin plastic sheets perforated with a hierarchical pattern of cuts arranged to form an array of hinged squares. It is shown that by tuning the geometric parameters of this hierarchy as well as thickness and material response of the sheets not only a variety of different buckling‐induced 3D deformation patterns can be triggered, but also the stress–strain response of the surface can be effectively programmed. Finally, it is shown that when multiple hierarchical patterns are brought together to create one combined heterogeneous surface, the mechanical response can be further tuned and information can be encrypted into and read out via the applied mechanical deformation. 相似文献
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Jeong‐Gyun Kim Haeyong Kang Yourack Lee Jeongmin Park Joonggyu Kim Thuy Kieu Truong Eun Sung Kim Doo Hyun Yoon Young Hee Lee Dongseok Suh 《Advanced functional materials》2017,27(30)
Flexible superconducting yarns consisting of sputter‐deposited NbN nanowires on highly aligned carbon nanotube (CNT) array sheets are reported. In the microscopic view, the NbN nanowires are formed on top of individual CNT fibrils, and the superconductivity property of the twist‐spun NbN–CNT yarn system is comparable to that of a typical NbN thin film on a normal solid substrate. Because of its intrinsic porosity, the system exhibits superior mechanical flexibility with a small bending radius. It also remains a superconducting state even when subjected to severe mechanical deformations, primarily due to the proximity superconductivity through carbon nanotube bundles. The results demonstrate the possibility of fabricating flexible superconducting yarns in a conventional thin‐film deposition process, using ultraflexible free‐standing CNT sheets as a template. In addition, preliminary tests on reducing the normal‐state resistance toward superconducting cable applications are presented. 相似文献
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The mechanical properties of 2D boron—borophene—are studied by first‐principles calculations. The recently synthesized borophene with a 1/6 concentration of hollow hexagons (HH) is shown to have in‐plane modulus C up to 210 N m?1 and bending stiffness as low as D = 0.39 eV. Thus, its Foppl–von Karman number per unit area, defined as C /D , reaches 568 nm?2, over twofold higher than graphene's value, establishing the borophene as one of the most flexible materials. Yet, the borophene has a specific modulus of 346 m2 s?2 and ideal strength of 16 N m?1, rivaling those (453 m2 s?2 and 34 N m?1) of graphene. In particular, its structural fluxionality enabled by delocalized multicenter chemical bonding favors structural phase transitions under tension, which result in exceptionally small breaking strains yet highly ductile breaking behavior. These mechanical properties can be further tailored by varying the HH concentration, and the boron sheet without HHs can even be stiffer than graphene against tension. The record high flexibility combined with excellent elasticity in boron sheets can be utilized for designing advanced composites and flexible devices. 相似文献
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Transparent conductive PVP/AgNWs films for flexible organic light emitting diodes by spraying method
In this study, a simple spraying method is used to prepare the transparent conductive films (TCFs) based on Ag nanowires (AgNWs). Polyvinylpyrrolidone (PVP) is introduced to modify the interface of substrate. The transmittance and bending performance are improved by optimizing the number of spraying times and the solution concentration and controlling the annealing time. The spraying times of 20, the concentration of 2 mg/mL and the annealing time of 10 min are chosen to fabricate the PVP/AgNWs films. The transmittance of PVP/AgNWs films is 53.4%—67.9% at 380—780 nm, and the sheet resistance is 30 Ω/□ which is equivalent to that of commercial indium tin oxide (ITO). During cyclic bending tests to 500 cycles with bending radius of 5 mm, the changes of resistivity are negligible. The performance of PVP/AgNW transparent electrodes has little change after being exposed to the normal environment for 1 000 h. The adhesion to polymeric substrate and the ability to endure bending stress in AgNWs network films are both significantly improved by introducing PVP. Spraying method makes AgNWs form a stratified structure on large-area polymer substrates, and the vacuum annealing method is used to weld the AgNWs together at junctions and substrates, which can improve the electrical conductivity. The experimental results indicate that PVP/AgNW transparent electrodes can be used as transparent conductive electrodes in flexible organic light emitting diodes (OLEDs). 相似文献
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Here, the development of ordered mesoporous silica prepared by the reaction of layered silicates with organoammonium surfactants is reviewed. The specific features of mesoporous silica are discussed with relation to the probable formation mechanisms. The recent understanding of the unusual structural changes from the 2D structure to periodic 3D mesostructures is presented. The formation of mesophase silicates from layered silicates with single silicate sheets depends on combined factors including the reactivity of layered silicates, the presence of layered intermediates, the variation of the silicate sheets, and the assemblies of surfactant molecules in the interlayer spaces. FSM‐16‐type (p6mm) mesoporous silica is formed via layered intermediates composed of fragmented silicate sheets and alkyltrimethylammonium (CnTMA) cations. KSW‐2‐type (c2mm) mesoporous silica can be prepared through the bending of the individual silicate sheets with intralayer and interlayer condensation. Although the structure of the silicate sheets changes during the reactions with CnTMA cations in a complex manner, the structural units caused by kanemite in the frameworks are retained. Recent development of the structural design in the silicate framework is very important for obtaining KSW‐2‐based mesoporous silica with molecularly ordered frameworks. The structural units originating from layered silicates are chemically designed and structurally stabilized by direct silylation of as‐synthesized KSW‐2. Some proposed applications using these mesoporous silica are also summarized with some remarks on the uniqueness of the use of layered silicates by comparison with MCM‐type mesoporous silica. 相似文献
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Dai‐Ming Tang Cui‐Lan Ren Ling Zhang Ying Tao Peng Zhang Wei Lv Xiang‐Ling Jia Xiaojuan Jiang Guangmin Zhou Takahito Ohmura Ping Huai Feng Li Yoshio Bando Dmitri Golberg Quan‐Hong Yang 《Advanced functional materials》2019,29(19)
It is essential to understand the size scaling effects on the mechanical properties of graphene networks to realize the potential mechanical applications of graphene assemblies. Here, a “highly dense‐yet‐nanoporous graphene monolith (HPGM)” is used as a model material of graphene networks to investigate the dependence of mechanical properties on the intrinsic interplanar interactions and the extrinsic specimen size effects. The interactions between graphene sheets could be enhanced by heat treatment and the plastic HPGM is transformed into a highly elastic network. A strong size effect is revealed by in situ compression of micro‐ and nanopillars inside electron microscopes. Both the modulus and strength are drastically increased as the specimen size reduces to ≈100 nm, because of the reduced weak links in a small volume. Molecular dynamics simulations reveal the deformation mechanism involving slip‐stick sliding, bending, buckling of graphene sheets, collapsing, and densification of graphene cells. In addition, a size‐dependent brittle‐to‐ductile transition of the HPGM nanopillars is discovered and understood by the competition between volumetric deformation energy and critical dilation energy. 相似文献