共查询到20条相似文献,搜索用时 15 毫秒
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本文研究了CVD制备的大尺寸石墨烯与柔性PET基底在拉伸变形过程中切向界面载荷传递的问题,采用原位拉曼光谱实验给出了加载过程中石墨烯的正应变、正应力以及界面切应力的分布曲线。分析表明,石墨烯与PET基底间的载荷传递存在四个阶段,分别是初始阶段、粘附阶段、滑移阶段和界面脱粘破坏阶段。在此基础上,本文对50μm、140μm、270μm和600μm四种尺寸石墨烯试件的界面力学性能进行测量,得到了不同尺寸石墨烯试件的界面力学性能参数,并初步给出了基底变形引起的石墨烯切向界面粘接能的变化,同时分析了试件尺寸对石墨烯界面力学性能的影响。实验结果表明,石墨烯材料和柔性基底最大切应力与临界脱粘切向界面粘接能等界面强度指标受到尺寸的显著影响,尺寸越小切向界面强度越高,反之,尺寸越大则越低。 相似文献
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Experimental Mechanics - We report the nanomechanical unfolding of individual self-folded graphene flakes on a flat substrate by using atomic force microscopy techniques. The nanomechanical... 相似文献
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Experimental Techniques - 相似文献
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Ballistic gelatin is widely used as a soft tissue simulant in physical surrogates for the human body to evaluate penetrating impacts and, more recently to evaluate blunt impact and blast loading effects on soft tissues. It is known that the properties of gelatin are sensitive to temperature and aging time, but this has not previously been quantified. The mechanical properties of 10% ballistic gelatin were measured using a compression test apparatus with temperature controlled platens to maintain the sample temperature at a fixed level. Penetration testing was undertaken using a standard BB impact test to assess the effect of aging. The gelatin was found to be within calibration after 3?days (72?h of aging), based on the standard penetration test. The material properties were evaluated using the stress at failure, strain at failure and material stiffness as characterized by the Neo-Hookean constitutive model. The stress at failure and material stiffness increased with decreasing temperature and increasing strain rate, as expected, while the strain at failure remained relatively constant for the test conditions considered (1 to 23??C, strain rate from 0.01 to 1.0?s?1). The study showed that the penetration resistance was consistent after 72?h of aging, while the mechanical study demonstrated increasing failure stress and stiffness with decreasing failure strain at longer aging times, suggesting that these effects offset one another so that the penetration resistance remains relatively constant. The primary contribution of this study was to show the importance of temperature and aging time, through mechanical and penetration testing, to achieve appropriate and consistent response from ballistic gelatin. 相似文献
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航天器太阳阵伸展过程最优控制的遗传算法 总被引:1,自引:0,他引:1
本文讨论航天器太阳阵伸展中航天器姿态的最优控制问题。利用动量矩守恒原理导出带太阳阵航天器的动力方程,指出了系统的非」完整约束性质。将航天器太阳阵展开过程中主体姿态控制问题转化为非线性系统最优控制问题。厚优控制中引入遗传算法,替代传统的牛顿迭代方法。提出基于遗传算法的非完整运动规划最优控制算法。通过数值仿真表明,该方法对太阳阵伸展过程航天器姿态控制是有效的。 相似文献
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A reliable understanding of the properties of 3-D braided composites is of primary importance for proper utilization of these materials. A new method is introduced to study the mechanical performance of braided composite materials using embedded optic fiber sensors. Experimental research is performed to devise a method of incorporating optic fibers into a 3-D braided composite structure. The efficacy of this new testing method is evaluated on two counts. First, the optical performance of optic fibers is studied before and after incorporated into 3-D braided composites, as well as after completion of the manufacturing process for 3-D braided composites, to validate the ability of the optic fiber to survive the manufacturing process. On the other hand, the influence of incorporated optic fiber on the original braided composite is also researched by tension and compression experiments. Second, two kinds of optic fiber sensors are co-embedded into 3-D braided composites to evaluate their respective ability 相似文献
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A laser-based optical technique, the Interferometric Strain/Slope Rosette (ISSR) technique, was used to measure real-time deformations in welding heat-affected zones. This was accomplished by measuring simultaneously real-time in-plane strains, out-of-plane slopes and weld plate temperature from both carbon and stainless steel plates. All strain/slope results demonstrated a strong sensitivity to such welding parameters as temperature, weld length and heat input. Accuracy of the measurements was studied. The strain/slope responses were also proven to be predictable, with measured strains comparable to released strains measured by resistance strain rosette/hole-drilling and ISSR/ring-core cutting. 相似文献
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For critical load bearing structures, it is often necessary to experimentally determine the load distribution on the structure
so that accurate finite element models can be developed for stress and fatigue life predictions. An inverse problem approach
is presented here for computing or calibrating the loads and boundary conditions acting on a structure. This enables the creation
of more accurate finite element models, especially for structures that have complicated load distribution and compliant boundary
conditions. The method presented here involves minimizing the least square error between the strains computed using the finite
element model and the strains and displacements obtained experimentally. The nodal loads and the compliance at fixed boundaries
are treated as the variables in the optimization problem. The compliance is modeled as springs attached at the nodes that
are on the boundary where the structure is restrained. The method is verified by computing the loads and boundary conditions
when displacements, maximum shear strain or both are available at large number of points on the surface of the structure.
The experimental data set was generated using the luminescent photoelastic coating (LPC) technique. 相似文献
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测量高塑性变形用20%大应变应变计 总被引:2,自引:0,他引:2
本文主要介绍了国内最新研制成功,用于测量材料高塑性变形量的新型传感器件-20%大应变应变计的产品性能和应用技术、为分析材料进入塑性变形区复杂的应力应变分布,提供了新型、准确、简便的测量手段。 相似文献
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Digital Image Correlation (DIC) is used to analyze in-situ obtained SEM images of a pearlitic steel. Rather than using a synthetic speckle the microstructure of the material (cementite lamellae embedded in a ferrite matrix) is used as a natural speckle. The impact of the DIC method parameters on the identified motion (displacements and strains) is studied and it is shown that the method is robust, in the sense of being insensitive to the subset size, when it comes to determining the local subset displacements. However, a sufficiently large subset size is required in order for the local subset strains to converge. 相似文献
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Throughout the past decades a considerable amount of work has been dedicated to the development and application of formalisms to simulate flexible bodies in a multibody system (MBS). The two most common approaches to describe the deformation of a flexible body with respect to their floating frame of reference are to apply the linear finite-element formulation and the linearmodal approach using global mode shapes.On the field of flexible body modelling, this paper discusses two topics: (a) the consideration of quadratic terms in the equations of deformation and (b) the presentation of methods for global mode preparation to reduce the computer time for dynamic simulations without loss of accuracy regarding deformations.The proposed methods are applied in two examples, for the deformation of a stabilisation linkage of a car's front suspension and for the simulation of the deployment of a flexible solar array. 相似文献
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Digital image correlation (DIC) of images obtained using scanning electron microscopy has been used to study, quantitatively, the plastic deformation of stainless steel at the microstructural scale. An artificial speckle pattern was generated by the remodelling of a deposited gold layer. A new experimental setup was shown to accelerate the remodelling process and promote the formation of finer nano-scale speckles with sizes ranging 30 nm to 150 nm and of similar spacing. The effects of surface preparation on speckle morphology are discussed. The high density of speckles enabled displacement mapping with resolution of one displacement vector each 0.2?×?0.2 μm2 of surface area. It is shown that sub-micron resolution is necessary to capture the plastic deformation associated with the formation of slip bands in stainless steel, which are an important component of the deformation of these materials at the microscale. Electron backscatter diffraction (EBSD) was used to reconstruct the surface grain boundaries and enabled these deformation features to be linked to the microstructure. 相似文献
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H. Weisbecker B. Cazzolato S. Wildy S. Marburg J. Codrington A. Kotousov 《Experimental Mechanics》2012,52(7):805-815
Three-dimensional scanning laser vibrometers enable extremely accurate non-contact measurement of the three-dimensional displacements on the surface of structures. This paper looks at the feasibility of using such a scanning laser vibrometer for the non-contact measurement of dynamic strain fields across the surface of a planar structure subjected to in-plane loading. Issues such as laser head alignment and choice of differentiation filter parameters are discussed. Finally, experimental results of two test specimens are presented which clearly demonstrate the significant potential of this new experimental technique as well as highlighting several limitations. 相似文献
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用数字散斑相关法研究聚氨酯泡沫塑料的压缩力学性能 总被引:3,自引:0,他引:3
提出了一种改进的数字散班相关计算方法,使其能直接进行应变迭代,灵敏度可达1000με,并对它进行了验证试验。对于两种不同密度的聚氨酯泡沫塑料,采用改进的数字散斑相关法对其压缩力学性能进行了测试,得到了其应力——应变关系及弹性模量等力学参数。 相似文献
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The bottom substrate effect is one of the major sources of error in force map studies of adherent cells and thin soft samples in an atomic force microscope (AFM)-based force spectroscopy. Because of this, samples appear stiffer than the natural. The popular Sneddon’s contact model, which assumes the sample as infinitely thick, fails to correct this error. In the present work, a simple asymptotically correct analytical correction to the bottom substrate effect is derived through contact mechanics approach and later the model is experimentally validated on a wide range of thickness of soft polyacrylamide gel and on adherent cells. 相似文献