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1.
The multiple interferometric strain/slope rosette (Multi-ISSR) is a method extended from the interferometric strain/slope
rosette (ISSR) to measure relative displacements of multiple strain gages and rigid-body-motion. The Multi-ISSR consists of
more than three micro-indentations depressed onto a material surface. Upon laser beam illumination of the Multi-ISSR, light
reflecting and diffracting from the Multi-ISSR indentations interfere to result in fringe patterns. The complicated patterns
are analyzed to measure deformation and rigid-body-motion. Optical theory of the Multi-ISSR is developed and the governing
equation for measuring deformation and rigid-body-motion is derived. Derivation of the general Multi-ISSR governing equation
for the case of three indentations is presented and compared with the governing equation of the published ISSR. 相似文献
2.
The multiple interferometric strain/slope rosette (Multi-ISSR) is a method extended from the interferometric strain/slope rosette (ISSR) to measure relative displacements of multiple strain gages and rigid-body-motion. The Multi-ISSR consists of more than three micro-indentations depressed onto a material surface. Upon laser beam illumination of the Multi-ISSR, light reflecting and diffracting from the Multi-ISSR indentations interfere to result in fringe patterns. The complicated patterns are analyzed to measure deformation and rigid-body-motion. Optical theory of the Multi-ISSR is developed and the governing equation for measuring deformation and rigid-body-motion is derived. Derivation of the general Multi-ISSR governing equation for the case of three indentations is presented and compared with the governing equation of the published ISSR. 相似文献
3.
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
4.
Experimental Techniques - 相似文献
5.
A General Methodology for Full-Field Plastic Strain Measurements Using X-ray Absorption Tomography and Internal Markers 总被引:1,自引:1,他引:0
Probing the strain locally and throughout the bulk of various materials has long been of interest in Materials Science. This
article presents a general methodology for assessing the plastic strain in terms of the displacement gradient tensor throughout
the bulk of opaque samples. The method relies on a homogenous distribution of marker particles throughout the bulk of a sample,
markers which are detected through the application of synchrotron X-ray tomography. Making use of the morphology of individual
markers, motion of individual markers is tracked during deformation allowing the local displacement field to be determined
throughout the bulk. The local displacement gradient tensor is derived from the displacement field. Spatial resolution is
directly related to marker particle density in the sample, here 30 μm. The accuracy of the displacement gradient tensor calculation
is dependent on the accuracy with which each marker position is determined and is shown to be in the range from 0.005 to 0.012.
The software implementation of the procedures and algorithms presented in this work has been collected to form the “3Dstrain”
program package which is intended to be free for use by the scientific community. It is available at under GNU General Public License. 相似文献
6.
As an important factor in evaluating the safety of civil infrastructures, predictions of displacement become the basis for determining the decrease of structural performance and the degree of aging in general. It is, however, well known that it is not easy to measure the displacement response of civil infrastructures such as suspension bridges due to a lack of appropriate measurement techniques, despite the importance of measurements in the displacement response. Thus, as an alternative for predicting the displacement response indirectly, the conversion of the measured strain signal obtained using Fiber optic Bragg-Grating (FBG) sensors into the displacement response is suggested. In previous studies on the prediction of displacement response using FBG sensors, static displacement was mainly predicted. A known complication in the use of the measured strain signal to predict dynamic displacement is the fact that the measured strain signal includes higher modes, and that the predicted dynamic displacement can be inherently contaminated by broad-band noises. To overcome such a problem, a mode decomposition technique was used. This is a method that estimates the total displacement response combined with each displacement response about the major mode of the structure and the quasi-static displacement responses. In order to verify the suggested algorithm to predict the displacement responses from FBG strain signals, a model experiment and field tests were executed. 相似文献
7.
J. M. Teixeira Pinto F. Touchard S. Castagnet C. Nadot-Martin D. Mellier 《Experimental Mechanics》2013,53(8):1311-1321
To improve physical motivation of mechanical modeling for semi-crystalline polymers, a better understanding of micro-mechanisms and a quantification of the mechanical response at the microstructure scale are needed. Strain field evolutions during deformation would be useful information but experimental techniques are still lacking for these materials. In this paper, an in-situ Digital Image Correlation (DIC) technique in the Scanning Electron Microscope (SEM) was developed to access strain fields at the spherulitic scale of a polypropylene. The evolution of strain heterogeneities during deformation were analyzed and correlated to the microstructure. 相似文献
8.
This paper deals with the accurate calculation of strain using the grid method. The strain field is first directly deduced
from the fringe pattern without calculating the displacement field. This procedure is validated with two numerical examples.
Two types of experiment are then carried out: a translation and a tensile test. It is observed that some additional fictitious
strains appear in both cases. They are due to two main reasons which interact with each other: the grid defects and the displacement
of the grid lines during testing. A suitable procedure is proposed to cancel out these fictitious strains. This procedure
is successfully applied in two cases of fringe patterns. 相似文献
9.
Alistair J. Revell Tim J. Craft Dominique R. Laurence 《Flow, Turbulence and Combustion》2011,86(1):129-151
This paper reports the application of a recently developed turbulence modelling scheme known as the C
as
model. This model was specifically developed to capture the effects of stress-strain misalignment observed in turbulent flows
with mean unsteadiness. Earlier work has reported the approach applied within a linear k-ε modelling framework, and some initial testing of it within the k-ω SST model of Menter (AIAA J 32:1598–1605, 1994). The resulting k-ε-C
as
and SST-C
as
models have been shown to result in some of the advantages of a full Reynolds Stress transport Model (RSM), whilst retaining
the computational efficiency and stability benefits of a eddy viscosity model (EVM). Here, the development of the the high-Reynolds-number
version of the C
as
model is outlined, with some example applications to steady and unsteady homogeneous shear flows. The SST-C
as
form of the model is then applied to further, more challenging cases of 2-D flow around a NACA0012 aerofoil beyond stall
and the 3-D flow around a circular cylinder in a square duct, both being flows which exhibit large, unsteady, separated flow
regions. The predictions returned by a range of other common turbulence modelling schemes are included for comparison and
the SST-C
as
scheme is shown to return generally good results, comparable in some respects to those obtainable from far more complex schemes,
for only moderate computing resource requirements. 相似文献
10.
Experimental Mechanics - In this study, pressure distributions were reconstructed from phase-locked surface deformation measurements on a thin plate. Slope changes on the plate surface were induced... 相似文献
11.
E. Plancher J. Petit C. Maurice V. Favier L. Saintoyant D. Loisnard N. Rupin J.-B. Marijon O. Ulrich M. Bornert J.-S. Micha O. Robach O. Castelnau 《Experimental Mechanics》2016,56(3):483-492
Determining the accuracy of elastic strain measurements in plastically deformed alloys is an experimental challenge. To develop a novel cross-validation procedure, a controlled elasto-plastic strain gradient was created in a stainless steel single crystal by four point bending deformation. The corresponding elastic strain field was probed, with an intragranular spatial resolution, in-situ by Laue microdiffraction and ex-situ by High Resolution EBSD. Good agreement is found for the two independent measurements and the predictions of a mechanical model, at plastic strains below 0.5 %. The accuracy of the measurements is estimated at 3.2 × 10? 4. 相似文献
12.
本文应用平面几何及光学原理,从理论和实践上分析了应用激光多普勒测速仪(LDV)进行实际测量时,在有窗口的情况下应该注意的几个问题,并给出了测量点位置偏差修正的定量公式以及光轴方向上测速精度相对误差的评估方程,省略了繁琐的理论推导. 相似文献
13.
14.
The Integral Method for determining residual stresses involves making surface deformation measurements within a sequence of
small increments of material removal depth. Typically, the associated matrix equation for solving the residual stresses within
each depth increment is ill-conditioned. The resulting error sensitivity of the residual stress evaluation makes it essential
that data measurement errors are minimized and that the residual stress solution method be as stable as possible. These two
issues are addressed in this paper. The proposed method involves using incremental deformation data instead of the total deformation
data that are conventionally used. The technique is illustrated using an example ESPI hole-drilling measurement. 相似文献
15.
Experimental Techniques - Full-field measurement techniques are invaluable tools for investigating material behavior across length-scales. In the current work, a full-field measurement technique,... 相似文献
16.
Y. L. Sun M. J. Roy A. N. Vasileiou M. C. Smith J. A. Francis F. Hosseinzadeh 《Experimental Mechanics》2017,57(5):719-734
Cutting-induced plasticity can lead to elevated uncertainties in residual stress measurements made by the contour method. In this study plasticity-induced stress errors are numerically evaluated for a benchmark edge-welded beam to understand the underlying mechanism. Welding and cutting are sequentially simulated by finite element models which have been validated by previous experimental results. It is found that a cutting direction normal to the symmetry plane of the residual stress distribution can lead to a substantially asymmetrical back-calculated stress distribution, owing to cutting-induced plasticity. In general, the stresses at sample edges are most susceptible to error, particularly when the sample is restrained during cutting. Inadequate clamping (far from the plane of cut) can lead to highly concentrated plastic deformation in local regions, and consequently the back-calculated stresses have exceptionally high values and gradients at these locations. Furthermore, the overall stress distribution is skewed towards the end-of-cut side. Adequate clamping (close to the plane of cut) minimises errors in back-calculated stress which becomes insensitive to the cutting direction. For minimal constraint (i.e. solely preventing rigid body motion), the plastic deformation is relatively smoothly distributed, and an optimal cutting direction (i.e. cutting from the base material towards the weld region in a direction that falls within the residual stress symmetry plane) is identified by evaluating the magnitude of stress errors. These findings suggest that cutting process information is important for the evaluation of potential plasticity-induced errors in contour method results, and that the cutting direction and clamping strategy can be optimised with an understanding of their effects on plasticity and hence the back-calculated stresses. 相似文献
17.
Experimental Mechanics - Micromechanics damage models applied to composites predict stresses and strains in the matrix and fibers as a function of the microstructure, constituting phases mechanical... 相似文献
18.
19.
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