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1.
This paper describes the details of a novel procedure called the cure-referencing method (CRM) to measure the strains associated
with residual stresses on the surface of composite panels. The CRM involves the replication of diffraction gratings onto the
surface of composite specimens during the autoclave during cycle. Residual strains associated with the curing process are
measured using moiré interferometry at room temperature after the specimens have been taken out of the autoclave. The procedures
for both the grating replication and the moiré interferometry experiment are described in detail. A method of high-temperature
moiré interferometry was developed to resolve the residual strains due to thermal expansion from those due to chemical matrix
shrinkage and stress relaxation. These procedures are demonstrated on unidirectional and multidirectional laminates and on
woven textile composites. 相似文献
2.
Hole-drilling method is one of the most convenient methods for engineering residual stress measurement. Combined with moiré
interferometry to obtain the relaxed whole-field displacement data, hole-drilling technique can be used to solve non-uniform
residual stress problems, both in-depth and in-plane. In this paper, the theory of moiré interferometry and incremental hole-drilling
(MIIHD) for non-uniform residual stress measurement is introduced. Three dimensional finite element model is constructed by
ABAQUS to obtain the coefficients for the residual stress calculation. An experimental system including real-time measurement,
automatic data processing and residual stresses calculation is established. Two applications for non-uniform in-depth residual
stress of surface nanocrystalline material and non-uniform in-plane residual stress of friction stir welding are presented.
Experimental results show that MIIHD is effective for both non-uniform in-depth and in-plane residual stress measurements.
The project supported by the FRAMATOME ANP 相似文献
3.
J. F. Cárdenas-García S. Ekwaro-Osire J. M. Berg W. H. Wilson 《Experimental Mechanics》2005,45(4):301-313
The hole method problem relates to two inverse problems of interest: the first, most commonly addressed by practitioners,
is to obtain residual stresses; the other, generally neglected, inverse problem can be posed as either a stress separation
problem or a material elastic properties identification problem. In both this Paper I and Paper II, we pose and solve this
dual hole method problem in an orthotropic plate, using computer generated moiré isothetics, by means of a non-linear least-squares
approach. In Paper I we address the residual stress problem. In Paper II we pose the use of moiré isothetics as a means to
achieve separation of stresses, but we deal with the determination of the five orthotropic elastic constants, four of which
are independent. 相似文献
4.
An existing method is extended to measure thermal strain distributions on an absolute basis. Free thermal expansion and stress-induced
deformations are separated, allowing the determination of coefficients of expansion, stress-induced strains, normal stresses
and shear stresses. The method is applicable to many steady-state and transient thermal-strain problems.
A crossed-line grating is replicated on the specimen at elevated temperature. A zero-expansion mold is used for the replication,
so that the grating frequency at the replication temperature can be retained to null the moiré interferometer at room temperature.
When the specimen is viewed in the moiré interferometer, the fringe patterns reveal theU andV displacements induced by any change from the replication temperature. In addition, carrier fringe techniques are introduced
for steady-state problems to subtract off the free thermal expansion and produce fringe patterns of the stress-induced deformations
themselves. The method is demonstrated by analysis of a bimaterial plate subjected to a uniform change of temperature.
Paper was presented at the 1988 SEM Fall Conference on Experimental Mechanics held in Indianapolis, IN on November 6–8. 相似文献
5.
Harold E. Gascoigne 《Experimental Mechanics》1994,34(1):27-36
Residual (curing) stresses in a cross-ply laminated plate are related to the strains released when individual plies are separated.
Released displacements are determined using high-sensitivity moiré interferometry and linearized strain-displacement equations
are used to determine residual strains. Elastic orthotropic stress-strain relations are used to calculate residual stresses
remote from free-edges of a [9020/020/9020] graphite-epoxy cross-ply panel. The measured strains compare favorably with those predicted by laminated plate theory. In
a second example, the circumferential and radial residual strains and stresses at the end-section of a thick-walled cross-ply
graphite-epoxy cylinder are determined.
Paper was presented at the 1992 SEM Spring Conference on Experimental Mechanics held in Las Vegas NV on June 8–11. 相似文献
6.
Yinyan Wang 《实验力学》2011,26(5):556-564
Phase-stepping technique is applied to the analysis of fringe patterns of shadow moiré of electronic packages.Sensitivity of the fringe pattern analysis is demonstrated to be significantly increased.Thermally induced warpage of electronic packages is successfully measured in real-time as the sample is driven through a simulated reflow process.The paper discusses the technique of phase stepping,noise filtering and its application to the shadow moiré method.Applications of the technology are presented. 相似文献
7.
Yinyan Wang 《实验力学》2011,26(7):733-739
Phase-stepping technique is applied to the analysis of fringe patterns of shadow moiré of electronic packages. Sensitivity of the fringe pattern analysis is demonstrated to be significantly increased. Thermally induced warpage of electronic packages is successfully measured in real-time as the sample is driven through a simulated reflow process. The paper discusses the technique of phase stepping, noise filtering and its application to the shadow moiré method. Applications of the technology are presented. 相似文献
8.
A finite-element technique to analyze the data obtained by the hole-drilling strain-gage method is presented. In this study,
residual stresses are assumed as initial stresses existing in the structural material or component. It is also assumed that
the elimination of the initial stresses in the region of the drilled hole changes the measured strains. After putting initial
stresses into displacement finite-element equations and comparing the stiffness matrix and the initial stresses matrix with
those of the previous increment, equations relating unknown initial stresses and measured strains were obtained. By solving
these equations, residual stresses were obtained. In this paper three examples are studied. In the first two examples, calibration
constants C1 to be used in determining residual stress were calculated which varied with depth. In the third example, the
data obtained by using the hole-drilling method are analyzed. All examples show good agreement with previous studies. Using
the present method allows greater flexibility of choice of specimen shape, materials, and experimental procedure than would
be possible if only analytic solutions were used. 相似文献
9.
《International Journal of Solids and Structures》2006,43(22-23):6751-6766
The moiré hole drilling method in a biaxially loaded infinite plate in plane stress is an inverse problem that exhibits a dual nature: the first problem results from first drilling the circular hole and then applying the biaxial loads, while the other problem arises from doing the opposite, i.e., first applying the biaxial load and then drilling the circular hole. The first problem is hardly ever addressed in the literature but implies that either separation of stresses or material property identification may be achieved from interpreting the moiré signature around the hole. The second is the well-known problem of determination of residual stresses from interpreting the moiré fringe orders around the hole. This paper addresses these inverse problem solutions using the finite element method as the means to model the plate with a hole, rather than the typical approach using the Kirsch solution, and a least-squares optimization approach to resolve for the quantities of interest. To test the viability of the proposed method three numerical simulations and one experimental result in a finite width plate are used to illustrate the techniques. The results are found to be in excellent agreement. The simulations employ noisy data to test the robustness of this approach. The finite-element-method-based inverse problem approach employed in this paper has the potential for use in applications where the specimen shape and boundary conditions do not conform to symmetric or well-used shapes. Also, it is a first step in testing similar procedures in three-dimensional samples to assess the residual stresses in materials. 相似文献
10.
The paper presents a new study on a tri-layer thin plate.Shadow moiré implemented with an advanced phase unwrapping technique is employed to obtain actual flexural deformation of a real-life plate sample subjected to thermal loads.An analytical model is re-formulated to provide the plate with global closed-form solutions of the plate deflection as well as the interfacial stress and strain.With the measurements and the solutions available,an inverse iterative approach is developed to evaluate and maximize th... 相似文献
11.
Surface topography can be conveniently investigated by a well-known shadow-moiré technique. It is relatively free from stringent
requirements on stability of instrumentation and quality of the light source. The main unresolved problem of the shadow moiré
is its relatively low resolution.
The digital-image-analysis enhanced shadow-moiré technique described here is based on the marriage of two well-known and developed
methods: classical shadow moiré and contemporary digital image analysis. This combination allows a significant increase of
the sensitivity of the classical shadow moiré by utilizing the ability of the digital-image-analysis system to acquire wholefield
light-intensity information and process this information to yield the related displacement field.
The suggested approach was utilized for a three-dimensional curved surface. The obtained topography of the three-dimensional
specimen was compared to the one measured by a high precision dial gage and the differences were on average less than three
percent between the two sets of data. The described combination of the shadow moiré and digital image analysis may prove as
a useful tool for on-line quality control in a variety of manufacturing processes.
Paper was presented at the 1990 SEM Spring Conference on Experimental Mechanics held in Albuquerque, NM on June 3–6. 相似文献
12.
The paper presents a new study on a tri-layer thin plate. Shadow moiré implemented with an advanced phase unwrapping technique is employed to obtain actual flexural deformation of a real-life plate sample subjected to thermal loads. An analytical model is re-formulated to provide the plate with global closed-form solutions of the plate deflection as well as the interfacial stress and strain. With the measurements and the solutions available, an inverse iterative approach is developed to evaluate and maximize the correlation between the measured and the predicted thermal flexure, leading to ascertained materials' constitutive and thermal behaviour. The inverse search algorithm starts with estimated ranges of material property parameters and progressively updates them to finally approach the respective true values. The established model solutions along with the optimized material properties matrix enable the prediction of the interfacial stresses/strains for the specific plate sample under evaluation. 相似文献
13.
14.
A hybrid technique of combining moiré measurement and analytical solution is developed to separate the normal and the tangential
components of distributed contact stresses between two co-plane bodies. The moiré interferometry offers the displacement fields
near the deformed contact zone, from which the tangential strains and boundary slopes of the deformed configurations can be
evaluated. Those experimental results provide boundary conditions for the discrete integration of Flamant’s solutions, to
inversely compute the separated components of the contact stresses.
The project supported by the National Basic Research Program (2007CB935602), the National Natural Science Foundation of China
(90607004) and the ICM Fund of CAEP (42105080106). 相似文献
15.
The deflection of micro-structures have been previously measured using optical interferometry methods. In this study, the
classical phase-shift shadow moiré method (PSSM) was applied to measure the deflection of a silicon micro-cantilever and to
determine the Young’s modulus of the cantilever material. The modulus value was determined from the profile based on deflection
equation. A normal white light source and a grating of 40 line pairs per mm were used to generate the moiré fringes. Since
the use of white light and high-resolution grating produces low contrast moiré fringes, the fringe visibility was enhanced
by applying contrast enhancement and filtering techniques. The Young’s modulus of the silicon cantilever material was estimated
to be 165.9 GPa with an uncertainty of ±11.3 GPa (6.8%). The experimental results show that the PSSM method can be successfully
applied for characterizing micro-cantilevers. Comparison of the deflection profile from the proposed method and a commercial
3-D optical profiler showed that the measurement range and sensitivity of PSSM are not affected by the poor contrast images. 相似文献
16.
Study of three-dimensional deformation of a pallet using phase-shiff shadow moiré and finite-element analysis 总被引:3,自引:0,他引:3
We present the results of a comparative study on the static deformation of a pallet, made from oil-palm fiberreinforced composite
material, using the phase-shift shadow moiré method and finite-element analysis (FEA). The pallet was designed and analyzed
using a commerical software package. The effect of various joint types on the deformation profile was studied to obtain a
simplified model to represent the actual design. A one-fifth scale model of the pallet was fabricated and the deformation
due to static loading was measured using the phase-shift shadow moiré method. The comparison between the measurement and FEA
results on the deformed profile showed a maximum difference of 13.7% at the center of the some of the deck boards, but a smaller
difference at other deck boards. The FEA results also produced a larger deformation gradient compared to the measurements. 相似文献
17.
A brief review is presented of the recent activities in the field of experimental mechanics in the People's Republic of China. The current research work covers the following subjects: (1) photoelastic phenomena, such as the classical three-dimensional photoelasticity, the scattered-light technique, birefringent coatings, birefringent materials; (2) holography, holographic interferometry, speckle interferometry and their applications; (3) moiré method; (4) strain-gage techniques and strain indicators. 相似文献
18.
Z-pin复合材料细观模型固化残余应力研究 总被引:1,自引:0,他引:1
针对植入Z-pin后碳纤维增强复合材料的微观结构,通过施加Z-pin周期性边界约束条件,建立了Z-pin复合材料单层板单胞细观模型.考虑固化过程中树脂体积收缩、弹性模量随固化度变化和纤维因Z-pin进入偏转因素,运用有限单元法计算了单胞结构在固化成型工艺过程中树脂和纤维应力发展和分布,并研究了Z-pin直径和分布密度对单层板面内残余应力的影响.结果表明:凝胶点之前,树脂模量和残余应力很小,凝胶点之后,树脂模量和残余应力增加较快;残余应力分布与纤维偏转有关;Z-pin直径和分布密度增加会使固化残余应力增大. 相似文献
19.
Moiré interferometry has been a valuable experimental technique for the understanding of the mechanical behavior of materials and structures. Over the last decade less emphasis has been placed on the development of the technique and more towards applications. This paper is a review article on recent applications using moiré interferometry in the fields of microelectronics devices, material characterization, micromechanics, residual stress, composite materials, fracture mechanics, and biomechanics. The general principles of moiré interferometry and advancement of techniques will not be discussed in this text, but references will be provided. 相似文献
20.
A robust fringe-shifting and image processing scheme is applied to geometric moiré experiments. High quality contour maps
ofU, V andW displacement fields are obtained with sensitivity enhanced by a factor of ten. The method is compatible with complicated
intensity distributions, variable bar-to-space ratios of gratings, and optical noise. It is applicable to large fields for
both in-plane moiré and shadow moiré measurements.
Paper was presented at the 1992 SEM VII International Congress on Experimental Mechanics held in Las Vegas, NV on June 8. 相似文献