Characterization of the Fracture Work for Ductile Film Undergoing the Micro-Scratch

The interface adhesion strength (or interface toughness) of a thin film/substrate system is often assessed by the micro-scratch test. For a brittle film material, the interface adhesion strength is easily obtained through measuring the scratch driving forces. However, to measure the interface adhesion strength (or interface toughness) for a metal thin film material (the ductile material) by the microscratch test is very difficult, because intense plastic deformation is involved and the problem is a three-dimensional elastic-plastic one. In the present research, using a double-cohesive zone model, the failure characteristics of the thin film/substrate system can be described and further simulated. For a steady-state scratching process, a three-dimensional elastic-plastic finite element method based on the double cohesive zone model is developed and adopted, and the steady-state fracture work of the total system is calculated. The parameter relations between the horizontal driving forces (or energy release rate of the scratching process) and the separation strength of thin film/substrate interface, and the material shear strength, as well as the material parameters are developed. Furthermore, a scratch experiment for the Al/Si film/substrate system is carried out and the failure mechanisms are explored. Finally, the prediction results are applied to a scratch experiment for the Pt/NiO material system given in the literature.

Optimization of the HIRFL-CSR cluster target

A new gas delivery system is designed and installed for HIRFL-CSR cluster target. The original blocked nozzle is replaced by a new one with the throat diameter of 0.12mm. New test of hydrogen and argon gases are performed. The stable jets can be obtained for these two operation gases. The attenuation of the jet caused by the collision with residual gas is studied. The maximum achievable H-2 target density is 1.75x10(13) atoms/cm(3) with a target thickness of 6.3x10(12) atoms/cm(2) for HIRFL-CSR cluster target. The running stability of the cluster source is tested both for hydrogen and argon. The operation parameters for obtaining hydrogen jet are optimized. The results of long time running for H-2 and Ar cluster jets look promising. The jet intensity has no essential change during the test for H-2 and Ar.

Dislocation theory of the fracture criterion for anisotropic solids

A dislocation theory of fracture criterion for the mixed dislocation emission and cleavage process in an anisotropic solid is developed in this paper. The complicated cases involving mixed-mode loading are considered here. The explicit formula for dislocations interaction with a semi-infinite crack is obtained. The governing equation for the critical condition of crack cleavage in an anisotropic solid after a number dislocation emissions is established. The effects of elastic anisotropy, crack geometry and load phase angle on the critical energy release rate and the total number of the emitted dislocations at the onset of cleavage are analysed in detail. The analyses revealed that the critical energy release rates can increase to one or two magnitudes larger than the surface energy because of the dislocation emission. It is also found elastic anisotropy and crystal orientation have significant effects on the critical energy release rates. The anisotropic values can be several times the isotropic value in one crack orientation. The values may be as much as 40% less than the isotropic value in another crack orientation and another anisotropy parameter. Then the theory is applied to a fee single crystal. An edge dislocation can emit from the crack tip along the most highly shear stressed slip plane. Crack cleavage can occur along the most highly stressed slip plane after a number of dislocation emissions. Calculation is carried out step by step. Each step we should judge by which slip system is the most highly shear stressed slip system and which slip system has the largest energy release rate. The calculation clearly shows that the crack orientation and the load phase angle have significant effects on the crystal brittle-ductile behaviours.

Latin hypercube sampling used in the calculation of the fracture probability

The paper proposes Latin hypercube sampling combined with the stratified sampling of variance reduction technique to calculate accurate fracture probability. In the compound sampling, the number of simulations is relatively small and the calculation error is satisfactory.

Sensitivity Analysis Of The Dimensionless Parameters In Scaling A Polymer Flooding Reservoir

A set of scaling criteria of a polymer flooding reservoir is derived from the governing equations, which involve gravity and capillary force, compressibility of water, oil, and rock, non-Newtonian behavior of the polymer solution, absorption, dispersion, and diffusion, etc. A numerical approach to quantify the dominance degree of each dimensionless parameter is proposed. With this approach, the sensitivity factor of each dimensionless parameter is evaluated. The results show that in polymer flooding, the order of the sensitivity factor ranges from 10(-5) to 10(0) and the dominant dimensionless parameters are generally the ratio of the oil permeability under the condition of the irreducible water saturation to water permeability under the condition of residual oil saturation, density, and viscosity ratios between water and oil, the reduced initial oleic phase saturation and the shear rate exponent of the polymer solution. It is also revealed that the dominant dimensionless parameters may be different from case to case. The effect of some physical variables, such as oil viscosity, injection rate, and permeability, on the dominance degree of the dimensionless parameters is analyzed and the dominant ones are determined for different cases.

Optimization of the multiwavelength erbium-doped fiber laser in a unidirectional cavity without an isolator

A highly uniform multiwavelength erbium-doped fiber ring laser with an intracavity sine phase modulator is demonstrated. The flat output spectrum is achieved by optimizing the cavity structure, modulation amplitude, and frequency of the sine phase modulator. Fifteen lasing lines with wavelength spacing of 0.9 nm appear simultaneously and stably with power differences less than 2 dB and side-mode suppression ratio higher than 32 dB. In addition, the proposed cavity can support unidirectional operation without optical isolators. An output power difference of about 20 dB is realized between the counterclockwise and clockwise directions, which is almost independent of the pump power and lasing wavelengths. (c) 2005 Society of Photo-Optical Instrumentation Engineers.

Optimization of the multiwavelength erbium-doped fiber laser in a unidirectional cavity without an isolator

A highly uniform multiwavelength erbium-doped fiber ring laser with an intracavity sine phase modulator is demonstrated. The flat output spectrum is achieved by optimizing the cavity structure, modulation amplitude, and frequency of the sine phase modulator. Fifteen lasing lines with wavelength spacing of 0.9 nm appear simultaneously and stably with power differences less than 2 dB and side-mode suppression ratio higher than 32 dB. In addition, the proposed cavity can support unidirectional operation without optical isolators. An output power difference of about 20 dB is realized between the counterclockwise and clockwise directions, which is almost independent of the pump power and lasing wavelengths. (c) 2005 Society of Photo-Optical Instrumentation Engineers.

Design optimization of the APF DTL in the SSC-linac

A linear accelerator as a new injector for the SSC (Separated Sector Cyclotron) of the HIRFL (Heavy ton Research Facility Lanzhou) is being designed. The DTL (Drift-Tube-Linac) has been designed to accelerate U-238(34+) from 0.140 MeV/u to 0.97 MeV/u. To the first accelerating tank which accelerates U-238(34+) to 0.54 MeV/u, the approach of Alternating-Phase-Focusing (APF) is applied. The phase array is obtained by coupling optimization software Dakota and beam optics code LINREV. With the hybrid of Multi-objective Genetic Algorithm (MOGA) and a pattern search method, an optimum array of asynchronous phases is determined. The final growth, both transversely and longitudinally, can meet the design requirements. In this paper, the deign optimization of the APF DTL is presented.

Comparison of the shape parameters of DNA-cationic lipid complexes and model polyelectrolyte-lipid complexes

In this study, we used a rheological method to study the shape of DNA-cationic lipid complexes and model polyelectrolyte-lipid complexes. We introduced two kinds of anionic polyelectrolytes, sodium polygalacturonate (PGU) and sodium dextran sulfate (DSS), of varying size, as models for DNA. The prepared complexes were incubated under laminar flow conditions. The results show the same quantitative relation between the shape parameter of lipoplexes and the length of anionic polyelectrolytes, including DNA. The rheological behavior of PGU and DSS were similar to that of DNA. (C) 2004 Elsevier Inc. All rights reserved.

Tuning The Geometrical Parameters Of Biomimetic Fibrillar Structures To Enhance Adhesion

Fibrillar structures are common features on the feet of many animals, such as geckos, spiders and flies. Theoretical analyses often use periodical array to simulate the assembly, and each fibril is assumed to be of equal load sharing (ELS). On the other hand, studies on a single fibril show that the adhesive interface is flaw insensitive when the size of the fibril is not larger than a critical one. In this paper, the Dugdale Barenblatt model has been used to study the conditions of ELS and how to enhance adhesion by tuning the geometrical parameters in fibrillar structures. Different configurations in an array of fibres are considered, such as line array, square and hexagonal patterns. It is found that in order to satisfy flaw-insensitivity and ELS conditions, the number of fibrils and the pull-off force of the fibrillar interface depend significantly on the fibre separation, the interface interacting energy, the effective range of cohesive interaction and the radius of fibrils. Proper tuning of the geometrical parameters will enhance the pull-off force of the fibrillar structures. This study may suggest possible methods to design strong adhesion devices for engineering applications.

Optimization of single attosecond x-ray pulses by genetic algorithm control of the chirp and initial phase of 5 fs laser pulses

We show that the peak intensity of single attosecond x-ray pulses is enhanced by 1 or 2 orders of magnitude, the pulse duration is greatly compressed, and the optimal propagation distance is shortened by genetic algorithm optimization of the chirp and initial phase of 5 fs laser pulses. However, as the laser intensity increases, more efficient nonadiabatic self-phase matching can lead to a dramatically enhanced harmonic yield, and the efficiency of optimization decreases in the enhancement and compression of the generated attosecond pulses. (c) 2006 Optical Society of America.

Optimization of high-order harmonic by genetic algorithm for the chirp and phase of few-cycle pulses

The brightness of a particular harmonic order is optimized for the chirp and initial phase of the laser pulse by genetic algorithm. The influences of the chirp and initial phase of the excitation pulse on the harmonic spectra are discussed in terms of the semi-classical model including the propagation effects. The results indicate that the harmonic intensity and cutoff have strong dependence on the chirp of the laser pulse, but slightly on its initial phase. The high-order harmonics can be enhanced by the optimal laser pulse and its cutoff can be tuned by optimization of the chirp and initial phase of the laser pulse.

Optimization of operational conditions in a submerged membrane bioreactor

In this study, optimization of operational conditions of a submerged membrane bioreactor treating municipal waste-water was studied. Mixed liquid suspended solid (MLSS), membrane flux (J(v)), aeration (Q), ratio of pumping, time to break time (t(p)/t(b)), and ratio of up flow area to down flow area (A Ad) were chosen as the easily manipulable parameters to study their effects on removal efficiency and membrane fouling. Totally, 16 different runs were designed to compare and select the best combination of the 5 parameters. The results showed that the optimal operational conditions were MLSS = 7g(.)L(-1), J(v) = 10L(.)m(-2.)h(-1), Q = 6 m(3.)h(-1), t(p)/t(b)= 4 min/1 min, and A(r)/A(d) = 1.7 m(2)/m(2). Under such conditions, the SMBR could achieve a double win of high removal efficiency and low membrane fouling.

THE FRACTURE-BEHAVIOR OF PHENOLPHTHALEIN POLYETHER ETHER KETONE AT ELEVATED-TEMPERATURE FOR LONG TERMS

The fracture behavior of phenolphthalein polyether-ether ketone (PEK-C) affected by physical aging at 200 degrees C was studied by tensile experiments, scanning electron microscopy, and differential scanning calorimetry observations. The ductile-brittle fracture transition (DBT) caused by physical aging can be considered as a competition between fracture mechanisms of crazing and shear yielding. The aging time required for the DBT is found to be around 400 h, based on the morphological studies and tensile experiments. The shear yielding component of the mechanical deformation could erase the aging effect, thus a deaging phenomenon occurs. We found that the deaging phenomenon has an intrinsic relationship with the extent of aging in the specimen and as a result of the fracture behavior. (C) 1995 John Wiley and Sons, Inc.