共查询到20条相似文献,搜索用时 15 毫秒
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Sebastian Stach Stanisaw Roskosz Jan Cwajna Jerzy Cybo 《Materials Characterization》2006,56(4-5):429-435
A methodology is presented of a multifractal image analysis which was applied to real stereometric files from profilographometric examinations of the fractures of WC-Co sintered carbides. The analysis was conducted based on the research scheme and theoretical basis discussed in [Stach S, Cybo J. Multifractal detection of overlaps based on a stereometric analysis of fracture surface: assumptions, Materials Characterization (in this issue).[1]]. The solution presented enables the detection of the locations of overlaps on a fracture surface and their graphic presentation. 相似文献
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直接将入侵检测算法应用在粗糙数据上,其入侵检测分析的效率非常低.为解决该问题,提出了一种基于主成分分析的入侵检测方法.该方法通过提取网络连接中的相关信息,对它进行解码,并将解码的网络连接记录与已知的网络连接记录数据进行比较,发现记录中的变化和连接记录分布的主成分,最后将机器学习方法和主成分分析方法结合实现入侵检测.实验结果表明该方法应用到各种不同KDD99入侵检测数据集中可以有效减少学习时间、降低各种数据集的表示空间,提高入侵检测效率. 相似文献
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A tough thermoplastic polymer may show a transition to brittle behaviour when a skin of different properties forms on, or is painted or bonded onto, its free surfaces. A small-scale yielding, linear elastic analysis of the core material, in combination with an axisymmetric plate analysis of the skin, is used here to explore the role in this phenomenon of skin-core modulus inequality. When applied to the homogeneous (equal modulus) case, this very simple constraint model appears to provide independent support for the ASTM thickness criterion for plane-strain LEFM test validity. When applied to previously published impact fracture data from inhomogeneous (polyethylene-polypropylene) sandwich plates, the model successfully explains the shift in brittle-tough transition temperature precipitated by bonding a polypropylene skin to a polyethylene core. The model offers specific predictions for the effect, on transition temperature shift, of variables such as skin thickness and core properties; these predictions remain to be verified. 相似文献
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In this work, we studied the influence of surface functionality of multi-walled carbon nanotubes (MWCNTs) on the mechanical properties of basalt fiber-reinforced composites. Acid and base values of the MWCNTs were determined by Boehm's titration technique. The surface properties of the MWCNTs were determined FT-IR, and XPS. The mechanical properties of the composites were assessed by measuring the interlaminar shear stress, fracture toughness, fracture energy, and impact strength. The chemical treatments led to a change of the surface characteristics of the MWCNTs and of the mechanical interfacial properties of MWCNTs/basalt fibers/epoxy composites. Especially the acid-treated MWCNTs/basalt fibers/epoxy composites had improved mechanical properties compared to the base-treated and non-treated MWCNTs/basalt fibers/epoxy composites. These results can probably be attributed to the improved interfacial bonding strength resulting from the improved dispersion and interfacial adhesion between the epoxy resin and the MWCNTs. 相似文献
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Collated fracture data for three steels, A533B, A508 and BS1501, and an Aluminium alloy, 2650, were examined to assess the statistical significance of the effect of prior loading on subsequent fracture. Weibull statistical and probabilistic analysis was used throughout. Two prior loading conditions were examined; one associated with warm pre-stress, and a second using pre-compression. For the former, prior loading resulted in an increase in the mean toughness together with an increase in the shape parameter and a decrease in variability compared to the as-received material. In contrast, when prior loading involved out-of-plane compressive loading (or side-punching) statistical evidence revealed that there was a reduction in toughness together with a decrease in the shape parameter and an increase in variability. Two numerical models were applied to steel data and were able to predict the overall trends obtained from the experiments, but could not reproduce accurately the experimental statistical distributions. 相似文献
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基于局部纹理分析的小目标检测方法 总被引:2,自引:0,他引:2
在多分辨率分析的基础上,提出了一种基于局部纹理分析的小目标检测新方法。利用目标与背景的局部纹理特征差异,在局部距离像上完成小目标的检测;而传统的检测方法利用目标点亮度值与背景亮度值不同进行目标与背景的分离,因此本方法更能体现目标与背景的差异,在强杂波背景中实现高效的检测。对实测数据的仿真实验表明,该方法能有效地检测占极少(1-3 个)像素的小目标;同时,在小波分解阶段分别采用 Mallat 算法和 à trous 算法时,该方法都能在 0.65秒内完成单帧检测,具有良好的实时性能。 相似文献
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Robert L. SmithIII John J. MecholskyJr. Stephen W. Freiman 《International Journal of Fracture》2009,156(1):97-102
Past attempts to determine fracture energy by the work of fracture (γ
WOF) technique, in most cases, have resulted in greater estimates due to the use of the cross-sectional area rather than the
actual area of the fracture surface in calculations. The actual fracture surface area A
F
of soda-lime-silica glass chevron-notch flexure specimens was estimated using atomic force microscopy. An equation for A
F
was developed using the data from these tests. The use of A
F
in the equation for γ
WOF resulted in γ
WOF values less than values reported from traditional fracture mechanics tests and from those obtained using the cross-sectional
area. The implication is that the tortuosity of the fracture surface contributes to the energy expended during fracture and
should be accounted for in the calculation of the fracture energy. These calculations provide an estimate for the minimum
energy required to break bonds in the fracture process. 相似文献
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This paper describes a model to predict mechanical strength distribution of silicon wafers. A generalized expression, based
on a multimodal Weibull distribution, is proposed to describe the strength of a brittle material with surface, edge, and bulk
flaws. The specific case of a cast, unpolished photovoltaic (PV) wafer is further analyzed. Assuming that surface microcracks
constitute the dominant mechanism of wafer breakage, this model predicts the strength distribution of PV silicon that matches
well the experimental results available in the literature. 相似文献
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Mitchell R Marzolini NL Hancock SA Harridance AM Elder DP 《Drug development and industrial pharmacy》2006,32(2):253-261
Analytical methods for determining the manufacturing process of tablet dosage forms have not been previously reported. The use of surface analysis techniques in particular X-ray Photoelectron Spectroscopy and Time of Flight Secondary Ionization Mass Spectrometry will be described and a model proposed which allows the prediction of the route of manufacture in calcium phosphate and cellulosic-based tablet formulations. Results of the application of this model to evaluate prototype tablet formulations prepared by wet granulation or direct compression will be reported. Strengths and limitations of the model will be discussed. 相似文献
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This paper presents an approach to detect surface cracks in various composite laminates. Carbon/epoxy composite AS4/PEEK was used to fabricate laminated plates, [0]16, [90]16, [(0/90)4]S and [±45/0/90]2S. Surface crack damage was created on one side of the plate using a laser cutting machine. Modal analysis was performed to obtain the mode shapes from both experimental and finite element analysis results. The mode shapes were then used to calculate strain energy using the differential quadrature method (DQM). Consequently, the strain energies of laminated plates before and after damaged were used to define a damage index which successfully identified the surface crack location. 相似文献
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A thin skin of low tensile failure strain, if bonded to the tensile surface of an un-notched impact bend specimen of much
tougher material, can change the global failure mode from ductile to brittle. A novel model of this well-known effect is developed
and applied to results from impact tests on a tough core of polyamide-polyethylene blend, with a single skin of brittle EVOH.
At a fixed crosshead speed, notched specimens of the blend become brittle at a relatively low temperature T
bt. Un-notched bilayer specimens continue to show skin fracture up to a considerably higher temperature T
fs; above this temperature they do not fail at all but below T
bt they too fail in a brittle manner. Within the temperature range from T
fs down to T
bt there is a transition from crack arrest, either at the skin/core interface or further into the core where a crack would not
normally propagate, to brittle fracture. This brittle fracture temperature is predicted by modelling the process as a three-phase
impact event. In the first phase, the striker bends the bilayer quasi-statically. The second phase begins with instantaneous
fracture of the skin at its failure strain. The skin ends retract at finite speed, and a craze grows in the adjacent core
material to accommodate the local strain singularity. The last phase is a striker-driven impact event similar to that in a
notched bend specimen of the core material, except that the crack-tip craze already bears the adiabatic temperature distribution
generated while it was driven open by skin retraction. The criterion for craze decohesion, and hence for a crack jump, is
the same adiabatic decohesion criterion which accounts for the speed-dependence of impact fracture in notched monolayer specimens.
Applied computationally, this model predicts whether a bilayer structure fails in a brittle way or whether cracks initiated
in the skin are arrested, either temporarily or permanently, at the skin/core interface. 相似文献
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In the present investigation it is shown that the effective fatigue threshold is uniquely correlated to the Young's modulus for a wide range of metallic and composite materials (ΔKth,eff=1.64·10−2·E). It is also demonstrated that the crack closure level Kcl increases with increased roughness of the fracture surface
. Kcl and
are quantitatively related via the equation
for steels with widely different mechanical properties and grain sizes (120 MPa<Rp<1100 MPa, 1 μm<λ<100 μm). This relation can be extended to materials other than steels (e.g. aluminium and WC-Co alloys) by normalising against Young's modulus. The roughness value
represents the standard deviation of height of the fracture surface and is shown to be simply related to the length and angle distributions of the linear length elements constituting the fracture profile. 相似文献