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31.
Damage and fracture prediction of plastic-bonded explosive by digital image correlation processing 总被引:3,自引:0,他引:3
M. Li J. Zhang C.Y. Xiong J. Fang J. M Li Y. Hao 《Optics and Lasers in Engineering》2005,43(8):856-868
By digital correlation processing of Scanning electronic microscopy (SEM) images, the paper presents the deformation and damage analysis of an energetic material—the plastic-bonded explosive (PBX) on mesoscopic scale. The analysis is made by observing the deformation field resulted from the digital image correlation (DIC) processing of the images corresponding to the loading steps and comparing with the surface profiles of the composite material so as to visualize the matter damage near a preset crack. The results show that the local deformation disturbance can reveal the material damage even happened underneath the specimen surface. The strain distribution in the front of the preset crack, can be used to predict the propagating route of the microcrack initiated from the tip of the pre-crack, which is related to the splitting fracture of the granular-based composite under compressive loading. 相似文献
32.
The Coherent Gradient Sensor (CGS) is extended to the optical differentiation of specular, diffracted wave fronts leading
to the combined measurement of in- and out-of-plane displacement field gradients. A derivation of the underlying optical interference
principles is presented along with an analysis of the effective instrument sensitivity. In order to demonstrate the capabilities
of the technique, experimental measurements of crack-tip deformation fields were conducted under various loading conditions
corresponding to mode-I, mode-II, and mixed mode near-tip crack fields. The experimental procedures and results of these tests
are presented as validation of the technique. 相似文献
33.
One major problem with ball and socket artificial discs is the migration of wear particles to the surrounding tissues. This debris can cause inflammation that can lead to implant loosening. Encapsulating the artificial disc with an elastomer sheath could prevent this problem by retaining the wear particles within the disc. The encapsulation sheath will face millions of tensile cycles during the implant life and, therefore, it must have the ability to withstand large strains without fracture. Using cyclic displacement, crack nucleation was applied on dumbbell specimens and crack growth was applied on rectangular specimens with an initial crack. Both tests were performed on Silex silicone and polyurethane ether elastomer specimens, both with a Shore durometer hardness of 40 shore A. No samples completely failed during the crack nucleation tests after five million cycles. The polyurethane ether elastomer showed a slower rate of crack growth life (421 k cycles to reach 70 mm crack length) than silicone elastomer (221 k cycles to reach the same crack length) in the control group. Accelerated ageing decreased the hardness and the crack growth rate of the polyurethane elastomer but had the opposite effect for the silicone elastomer. Gamma sterilization increased the crack growth rate and did not affect the hardness of the polyurethane elastomer. The hardness and the crack growth rate of the silicone elastomer were increased after gamma sterilization. 相似文献
34.
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36.
L.C.S. Nunes 《Optics and Lasers in Engineering》2011,49(5):640-646
The aim of this work is to estimate two important material properties of the polytetrafluoroethylene (PTFE) polymer by means of a single experimental test. The displacement fields around a crack tip are used for estimating the modulus of elasticity (or, Young's modulus) and Poisson's ratio. These parameters are evaluated by fitting linear fracture mechanic expression of displacement fields in the vicinity of the crack, for mode I, to the experimental data. Measurements of these displacements are carried out using digital image correlation (DIC) method. In this way, the experimental procedure is conducted by loading a double-edge-cracked plate specimen. In order to validate the results, two available experimental tests have been performed. The modulus of elasticity is determined by means of the tensile test, using a standard test machine. Moreover, the Poisson's ratio is obtained by measuring lateral compressive and longitudinal extensional strain using DIC method. 相似文献
37.
The aim of this paper is to study the free vibration of nanobeams with multiple cracks. The analysis procedure is based on nonlocal elasticity theory. This theory states that stress at a point is a function of strains at all points in the continuum. The nonlocal elasticity theory becomes significant for small length scale in micro and nanostructures. The effects of nonlocality, crack location and crack parameter are investigated on the natural frequencies of the cracked nanobeam. In this study, analytical solutions are given for cracked Euler–Bernoulli nanobeams of different boundary conditions. 相似文献
38.
Waterborne crackle decorative coatings and crack patterns 总被引:1,自引:0,他引:1
Yongchao ZhaoLinhui Qiang Juntao YanShijin Dong Qiaoyun ZhangLisi Zhang Xuejun Cui Hongyan Wang 《Applied Surface Science》2011,257(9):4377-4383
A preparation method of waterborne crackle decorative coatings was reported in this paper and the factors that influence crack patterns were investigated. The crackle coating consisted of a waterborne basecoat and a waterborne topcoat. The basecoat was made from two-component epoxy emulsion and the topcoat was made from fluorine-containing acrylic emulsion, silicone-acrylic emulsion or styrene-acrylic emulsion. Three junction types of crack patterns were prepared by the three top coatings, which were T-junction, Y-junction and mixed junction. T-junction type with long and straight cracks was prepared from styrene-acrylic emulsion 296DS. Y-junction type with curve and short cracks was prepared from fluorine-containing acrylic emulsion A603C and mixed junctions type was made from silicone-acrylic emulsion. Crack patterns with different spacing were prepared by controlling the thickness of topcoat, dryness of basecoat or conditions of film forming. The characterize methods of type and spacing for crack pattern were developed and properties of coating film including adhesion, water resistance, scrub resistance and so on were tested. The results showed that the crackle coatings possessed satisfactory properties for practical application. 相似文献
39.
An experimental method is developed to examine the near tip deformation at the mesoscopic scale level. The differential interference contrast (DIC) method is used by application of the Nomarski prism in polarized microscope for measuring the out of surface deformation. The method is very sensitive to small height changes detected by different interference color. Discussed are results for the crack tip deformation field. 相似文献
40.
A new experimental technique has been developed to investigate the onset of fracture in metals at low and intermediate stress
triaxialities. The gage section of a flat specimen has been designed such that cracks are most likely to initiate within the
specimen center, remote from the specimen boundaries. Along with the specimen, a biaxial testing device has been built to
apply a well-defined displacement field to the specimen shoulders. The stress state within the specimen is adjusted by changing
the biaxial loading angle. Using this new experimental technique, the crack initiation in metals can be studied experimentally
for stress triaxialities ranging from 0.0 to 0.6. The stress and strain fields within the specimen gage section are determined
from finite element analysis. The reliability of the computational model of the test set-up has been verified by comparing
the simulation results with laser speckle-interferometric displacement measurements during testing. Sample experiments have
been performed on the Al-7Si-Mg gravity die casting alloy. A three-step hybrid experimental–numerical calibration procedure
has been proposed and applied to determine a phenomenological crack formation criterion for the Al-7Si-Mg alloy.
相似文献
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