共查询到20条相似文献,搜索用时 0 毫秒
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G. Martin D. Caldemaison M. Bornert C. Pinna Y. Bréchet M. Véron J.D. Mithieux T. Pardoen 《Experimental Mechanics》2013,53(2):205-215
A microgrid technique has been developed for the analysis of the high-temperature micro-scale strain distribution between ferrite and austenite into duplex stainless steels. The local strain is measured by micro-extensometry using square microgrids engraved on flat specimens by electro-lithography. The sample with microgrids on the surface and preliminary imaged with high definition scanning electron microscope (SEM), is inserted in a plane strain compression specimen to be deformed under conditions representative of hot rolling. After deformation, the sample is extracted from the compressed block and the surface is again analyzed by SEM and image processing to determine the strain field. The strain is heterogeneously distributed with a strong localization of the deformation, in the form of shear bands located within the ferrite and at the vicinity of the austenite/ferrite interphase boundaries. These strain maps provide useful informations about the rheology of the phases as well as about the local conditions at the origin of the damage process. 相似文献
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Experimental Mechanics - In this paper, strains are monitored in-situ at the surface of a polycrystalline 316 L sample loaded quasi-statically in uniaxial tension. Initial orientation data... 相似文献
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Experimental Investigation of Plastic Strain Recovery and Creep in Nanocrystalline Copper Thin Films
Nanocrystalline metals exhibit a phenomenon called plastic strain recovery whereby plastic strain introduced through a load cycle is gradually recovered under no external loading over a time period of hours and days. In this study, we experimentally explore the diffusive mechanisms and the strain rates for nanocrystalline thin films of copper with an average grain size of about 35 nm during plastic strain recovery and creep. The experiments are performed via the plane strain bulge test and the thin film samples are deposited using thermal evaporation and sputtering. The specimens recover their residual strain in a period of time with two characteristic strain rates, a transient strain recovery rate of the order of 10?7/s and a steady-state strain recovery rate of the order of 10?9/s and there is a characteristic time at which the transition occurs between the two rates. The results suggest that a diffusive mechanism in conjunction with voids within the nanocrystalline material can explain the two plastic strain recovery rates and the transition between the two. 相似文献
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Olver迭代与Newton迭代的比较 总被引:2,自引:0,他引:2
Olver迭代是一个立方收敛的求根公式,而Newton迭代仅是平方收敛,但前者却不如后者为人们所熟知,以至于近来有作者其推导了一个新的高阶迭代公式,而实际就是Olver迭代公式却浑然不如。那么,到底是什么原因导致Olver迭代没有被广大的计算方法教科书介绍呢?本文对Newton迭代与Olver迭代做了详尽的分析,给出了两者各自的精度表达式,并对两者进行了比较,结论是:从计算效率及精度方面综合考虑,Olver迭代公式不如Newton迭代公式实用。 相似文献
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K. N. Jonnalagadda I. Chasiotis S. Yagnamurthy J. Lambros J. Pulskamp R. Polcawich M. Dubey 《Experimental Mechanics》2010,50(1):25-35
A new microscale uniaxial tension experimental method was developed to investigate the strain rate dependent mechanical behavior
of freestanding metallic thin films for MEMS. The method allows for highly repeatable mechanical testing of thin films for
over eight orders of magnitude of strain rate. Its repeatability stems from the direct and full-field displacement measurements
obtained from optical images with at least 25 nm displacement resolution. The method is demonstrated with micron-scale, 400-nm
thick, freestanding nanocrystalline Pt specimens, with 25 nm grain size. The experiments were conducted in situ under an optical
microscope, equipped with a digital high-speed camera, in the nominal strain rate range 10−6–101 s−1. Full field displacements were computed by digital image correlation using a random speckle pattern generated onto the freestanding
specimens. The elastic modulus of Pt, E = 182 ± 8 GPa, derived from uniaxial stress vs. strain curves, was independent of
strain rate, while its Poisson’s ratio was v = 0.41 ± 0.01. Although the nanocrystalline Pt films had the elastic properties
of bulk Pt, their inelastic property values were much higher than bulk and were rate-sensitive over the range of loading rates.
For example, the elastic limit increased by more than 110% with increasing strain rate, and was 2–5 times higher than bulk
Pt reaching 1.37 GPa at 101 s−1. 相似文献
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本文将解决复杂弹塑性问题的有效工具内时理论,引入到岩石衰减的研究中来。根据内时理论,简要推导了在中等应变条件下,岩石衰减与应变振幅的用非弹性参数α表示的具体关系式。在MTS压机上,对砂岩、花岗岩等多种岩石样品进行了一系列的循环加卸载实验。利用应力应变滞回曲线的面积,根据衰减的能量损耗的定义,计算了各种实验条件下的岩石样品的衰减值。实验数据表明,在各次循环平均应力相等的条件下,岩石样品的衰减随应变振幅的增加而增加,与内时理论的推导结果相一致。最后,对表示岩石非弹性的参数α进行了简要的讨论。砂岩的α值较为稳定,在0.5左右;而花岗岩的α值变化较大,但二者都随着应力的增加而增加。该实验结果对地震波在地球介质中的衰减研究有一定的参考意义。 相似文献
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应用复变函数解析延展原理,并通过求解Riemann-Hilbert问题,得到了含共圆弧界面裂纹系的压电材料反平面应变问题的一般解;对单个圆弧界面裂纹的情形,给出了封闭形式的复函数解和场强度因子 相似文献
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Experimental Mechanics - The commercialization of additive manufacturing (AM) is underway in the aerospace and biomedical device industries [1, 2]. However, most metal parts produced by AM are... 相似文献
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Electrophysical, hydro-gas-dynamic, and thermal characteristics of a discharge arising between liquid electrodes are considered. Spatial visualization of flow patterns in the gas discharge region is performed by using the schlieren technique. 相似文献
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弹性杆与结构接触冲击的冲击力计算研究 总被引:2,自引:0,他引:2
本文提出了一种将杆与结构的接触冲击问题简化为集中力与集中阻尼的常规结构动力学问题的计算模型。对于大型结构,可采用一种特殊的人工边界,只需对人工边界域内的结构用有限元法进行计算。这种人工边界是齐次的,可根据冲击影响区的大小人为地确定 相似文献
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Wei Huang Mi Wang Zhou Hu Lingling Wang Junxin Cao Dewen Kong 《Acta Mechanica Solida Sinica》2021,34(1):137-148
In this study,the strain rate-dependent dynamic tensile behavior of ZrB2-20%SiC ceramic composite was investigated using experimental and numerical approaches.The split Hopkinson pressure bar apparatus was used to measure the dynamic splitting tensile response at strain rates of 17-67 s?1.The experiment results demonstrate a significant strain rate dependence of the dynamic tensile behavior of the ZrB2-SiC ceramic composite.The dynamic tensile strength increased linearly with the strain rate,from 288 MPa at 17 s?1to 654 MPa at 67 s?1.Moreover,a strain rate-dependent tensile strength was introduced into a modified JH-2 model to describe the dynamic tensile behavior and fracture process of ZrB2-SiC ceramics.The numerical results of dynamic tensile strength agree well with the experimental result.Moreover,the fracture process of ZrB2-SiC ceramics under dynamic tension was further studied by combining high-speed images and numerical results.The effect of strain rate on the fracture process and failure patterns of the ZrB2-SiC ceramic composite could be verified by the modified JH-2 model. 相似文献
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A new kind of nonlinearity of inertial type caused by accelerated motionof interacting particles is described. The model deals with an ensembleof grains immersed into a vibrating fluid. First, the nonlinearvibration of two connected grains is studied. The temporal behaviours ofdisplacement and velocity, as well as spectrum of vibration, areanalysed. Numerical simulations are performed. Then an infinite chain ofgrains is considered and the corresponding differential-differenceequation is derived. For the continuum limit the inhomogeneous nonlinearwave equation is solved and temporal profiles are calculated. A newresonant phenomenon is described and the resonant curves areconstructed. 相似文献
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Experimental Investigation on Correlation Between Permeability Variation and Pore Structure During Coal Pyrolysis 总被引:1,自引:0,他引:1
Zhao Yangsheng Qu Fang Wan Zhijun Zhang Yuan Liang Weiguo Meng Qiaorong 《Transport in Porous Media》2010,82(2):401-412
Transport in porous media with chemical and thermal effects is a common phenomenon; it is also a complicated scientific problem with applications in the field of mining engineering. In situ pyrolysis for coal gas generation is just such a problem, involving material and structural changes in the coal and surrounding rocks, with massive thermal and chemical effects. The transport properties of the coal are substantially changed, which in turn affect the thermal and chemico-mechanical reactions. A series of laboratory experiments on pore structure and permeability changes during gas coal pyrolysis were carried; the experimental procedure and results are described and analyzed in this study. The pore volume and permeability of tested specimens experienced modest changes during the heating process from 20 to 300°C, but when heated from 300 to 400°C, large pores in the specimens greatly increased and the overall porosity reached 23% at 400°C, which is larger than the percolation threshold value of the rock mass with pores and cracks. The permeability of the specimens increased exponentially with temperature, evidencing the massive structural changes that took place in the specimens during the pyrolysis process. In the high temperature range from 400 to 600°C, fewer changes in the specific surface area of microscopic and small pores in the coal took place, but the pore volume and porosity increased linearly with temperature. 相似文献
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本文对传统的四连杆式紧线器进行了空间力系分析,找到了致其破坏的力学因素.并且采用有限元法和应变电测法,确定了紧线器钳体的应变幅值及高应变区域.再按局部应力应变法考察了钳体的损伤容限.使紧线器达到了负荷容量大、重量轻以及安全可靠的设计要求. 相似文献
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A cyclic biaxial stress measurement method using electrodeposited copper foil was examined. The crystallographic orientations
of individual grains that undergo grain growth in copper foil subjected to cyclic loading were analyzed by electron backscatter
diffraction (EBSD). One of the slip directions in most of the grains corresponded to the direction of maximum shear stress
when the biaxial stress ratio was negative. However, the number of grains with other orientations gradually increased as the
biaxial stress ratio approached zero. On the basis of these features, we propose biaxial stress measurement using EBSD analysis
of grown grains in copper foil. Our new method has excellent resolution compared with other stress-strain measurement methods
since it can measure the average biaxial stress ratios in an area of 500 μm × 500 μm. 相似文献
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Phase shifted moiré interferometry is used to measure full-field strains during uniaxial tension and four-point bend loading
of nitinol test samples. Optical resolution and grating coherence were exceptional and allowed simultaneous resolution of
the strain fields within both the parent and transformed phases of the material. Evidence of localized and uniformly distributed
phase transformation was observed for the samples tested in uniaxial tension while the bending results indicate a clear tension/compression
asymmetry. The results further highlight the effect of the elasticity of the two phases and the complexity associated with
competing martensite and R-phase transformations on the thermomechanical behavior of nitinol. Finally, the technique is applied
to a nitinol implantable medical component to demonstrate the opportunities for improved end-use material characterization,
numerical modeling and design validation. 相似文献