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  • 1
    Electronic Resource
    Electronic Resource
    Molecular Dynamics Simulation of Nanocrystalline Tantalum under Uniaxial Tension (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 139 (Apr. 2008), p. 83-88 
    Details
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: Using molecular dynamics (MD) simulation, we have investigated the mechanicalproperties and the microstructural evolution of nanocrystalline tantalum (NC-Ta, grain size from 3.25nm to ~13.0 nm) under uniaxial tension. The results show the flow stress at a given offset straindecreases as the grain size is decreased within the grain size regime studied, implying an inverseHall-Petch effect. A strain rate sensitivity of ~0.14, more than triple that of coarse-grain Ta, is derivedfrom the simulation results. Twinning is regarded to be a secondary deformation mechanism based onthe simulations. Similar to nanocrystalline iron, stress-induced phase transitions from body-centeredcubic (BCC) to face-centered cubic (FCC) and hexagonal close-packed (HCP) structures take placelocally during the deformation process, The maximum fraction of FCC atoms varies linearly with thetensile strength. We can thus conclude that a critical stress exists for the phase transition to occur. It isalso observed that the higher the imposed strain rate, the further delayed is the phase transition. Suchphase transitions are found to occur only at relatively low simulation temperatures, and are reversiblewith respect to stress
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/24/transtech_doi~10.4028%252Fwww.scientific.net%252FSSP.139.83.pdf
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  • 2
    Electronic Resource
    Electronic Resource
    The Numerical Simulation of a Bird-Impact on an Aircraft Windshield by Using the SPH Method (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 33-37 (Mar. 2008), p. 851-856 
    Details
    ISSN: 1662-8985
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper is focused on the development of an effective numerical method to simulatebird-impact aircraft windshield events. A new Smooth Particle Hydrodynamics (SPH) which hasbeen incorporated as a solver option into the explicit finite element program PAM-CRASH wasused to model the bird. The deformation between the numerical results and the experimental resultsis in good agreement. Simulation results of a bird-impact process indicated that the SPH bird modelis more suitable to model the break-up of the bird into particles. Failure of the windshield in theexperiment was simulated, and the good agreement between the numerical and experiment indicatesthat the failure model established in the present paper is reasonable. Finally, the energy changes ofthe bird and the windshield were calculated
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/40/transtech_doi~10.4028%252Fwww.scientific.net%252FAMR.33-37.851.pdf
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  • 3
    Electronic Resource
    Electronic Resource
    Bio-Fabrication of Patterned Cellulose Nano-Fibers (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 47-50 (June 2008), p. 1359-1362 
    Details
    ISSN: 1662-8985
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In this paper, a new approach for controllable bio-fabrication of patterened cellulosenano-fibers has been proposed by micro-fluidic techniques, via the combination of biologicaltechnology and nanotechnology. We attempted to make sure whether A. xylinum can regularly movewithin micro-fluidic channels and further to clarify how the flow can direct and control the assemblyof cellulose nano-fibers. The movement of A. xylinum within the micro-fluidic channels was observedin vivo by real time video microscopy. The well-patterned materials have great potential utility intissue engineering
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/41/transtech_doi~10.4028%252Fwww.scientific.net%252FAMR.47-50.1359.pdf
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  • 4
    Electronic Resource
    Electronic Resource
    Preparation of Lactic Acid Based Polyurethanes Modified by Castor Oil (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 47-50 (June 2008), p. 1458-1461 
    Details
    ISSN: 1662-8985
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A series of biodegradable lactic acid based Polyurethanes modified by castor oil(PLBA-PUs) have been successfully prepared by using a two steps method as follow: Firstlyprepolymers with hydroxyl terminated are synthesized by copolymerization of L-lactic acid and 1,4-butandiol (BD), and then react with castor oil (C.O.) and hexamethylene diisocynate (HDI). Theeffects of BD/LA monomer ration and C.O./prepolymers mole ratio on the molecular weight andmechanical properties of PLBA-PUs are investigated. The polymers obtained are characterized bygel permeation chromatography, fourier transform infrared spectroscopy, 13C NMR, differentialscanning calorimeter (DSC) and tensile testing. Their average molecular weight is over 280,000.They display excellent mechanical properties, such as a tensile strength as high as 31MPa, a tensilemodulus as low as 20 MPa, and an elongation at break of 176%. Due to the biocompatibility, thesePUs could find applications in biomedical fields, such as soft-tissue engineering
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/41/transtech_doi~10.4028%252Fwww.scientific.net%252FAMR.47-50.1458.pdf
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  • 5
    Electronic Resource
    Electronic Resource
    Optimization of Wavelet Packets Analysis for Damage Detection in Composite Materials (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 334-335 (Mar. 2007), p. 1149-1152 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A method based on entropy-based criteria is present to choose the optimal decompositionof Wavelet Packets Analysis (WPA) for damage detection in composite materials. The structuraldamage indexes constructed based on energy spectrum variation of the structural vibration responsesdecomposed using WPA before and after the occurrence of structural damage usually generate acomplete binary tree to calculate its elements. Date mining is carried out in this paper by adoptionentropy as the criteria to choose the optimal decomposition tree. In the decomposition process, onlythe sub-signals which contain main information of the original signal are decomposed to generatenext level sub-signals. New damage index is constructed based on the optimal decomposition. Thenthe dimension of the damage index is reduced while still keeping its sensitive to damage. WhetherArtificial Neural Network (ANN) or genetic algorithm (GA) is used in the further process of tellingstructural damage status from damage index, this reduction will make remarkable time saving
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/53/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.334-335.1149.pdf
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  • 6
    Electronic Resource
    Electronic Resource
    Fatigue Crack Growth Simulation Using S-Version FEM (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 33-37 (Mar. 2008), p. 133-138 
    Details
    ISSN: 1662-8985
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Fatigue crack growth under mixed mode loading conditions is simulated using S-FEM. Byusing S-FEM technique, only local mesh should be re-meshed and it becomes easy to simulate crackgrowth. By combining with auto-meshing technique, local mesh is re-meshed automatically, andcurved crack path is modeled easily. Plural fatigue crack problem is solved by this technique. Fortwo parallel crack problem, criteria of crack coalescence are proposed. By simulating this problem byS-FEM, it is verified these criteria are conservative ones
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/40/transtech_doi~10.4028%252Fwww.scientific.net%252FAMR.33-37.133.pdf
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  • 7
    Electronic Resource
    Electronic Resource
    Research on Mode I and Mode II Dynamic Fracture in High Strength Steels under High Loading Rates (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 33-37 (Mar. 2008), p. 351-356 
    Details
    ISSN: 1662-8985
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The Mode I and Mode II dynamic fracture toughness (DFT) values, KId and KIId for highstrength steels 40Cr and 30CrMnSiNi2A were evaluated using a combined experimental-numericalmethod. The tests were performed on three point bend (3PB) and shear specimens with Hopkinsonpressure bar. The time of crack initiation was determined by a strain gauge. With the assistance of3-D transient finite element analysis, the temporal evolution of the dynamic stress intensity factorunder different loading rates was obtained, and the DFT was determined by the fracture initiationtime. In Mode I tests, a brittle transgranular fracture was found in 40Cr, while evidence for ductilefracture was observed on the failure surface of 30CrMnSiNi2A. In Mode II tests, both tensile cracksand adiabatic shear bands were found for the two steels. The effect of ligament size on fracturetoughness was discussed. The correlations of KId and KIId with loading rate were also investigated.The micromechanisms of loading rate effect on the DFT were discussed for both modes
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/40/transtech_doi~10.4028%252Fwww.scientific.net%252FAMR.33-37.351.pdf
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  • 8
    Electronic Resource
    Electronic Resource
    An Experimental Method for Micro-Scale Uniaxial Tension Test (2006)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 326-328 (Dec. 2006), p. 233-236 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A micro-scale uniaxial tension test method for measuring material mechanical propertiesof thin film materials is introduced in this paper. A self-developed test device is established basedon the CMT8202 tension test machine. The Interference Strain/Displacement Gauge (ISDG)method is used to measure the strain in the micro-samples. The three dimensional finite elementmethod (FEM) is utilized to optimize specimen geometry configuration and to reduce the stressconcentration in specimen around grip region. The experiments are carried out for thepolycrystalline copper thin film. The results show that stress-strain curves and the Young’s modulusof the thin film material can be obtained by micro-scale tension test. The Young’s modulusdetermined by micro-sample for polycrystalline copper thin film has a good agreement withpublished results
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/52/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.326-328.233.pdf
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  • 9
    Electronic Resource
    Electronic Resource
    Temperature and Strain Rate Effects on Mechanical Behavior of a PMMA (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 340-341 (June 2007), p. 1079-1084 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In this paper, the mechanical behavior of a PMMA used as the windshield of aircraft wastested. The experiments were finished under two quasi-static strain rates and a high strain rate withthe testing temperature from 299K to 373K. The results show that the mechanical property of thisPMMA depends heavily on the testing temperature. The Young’s modulus and flow stress werefound to decrease with increasing temperature at low strain rate. At the strain rate of 10-1 1/s, strainsoftening was observed under all experiment temperatures. At high strain rate, with the temperatureincreasing, the flow stress decreases remarkably while the failure strain increases, and the strainsoften was also observed at the temperature above 333K. Comparing the experiments results atsame temperature, it was found the flow stress increases with the rising strain rate. The predictionsof the mechanical behavior using the ZWT theoretical model have a good agreement withexperimental results in the strain range of 8%
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/54/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.340-341.1079.pdf
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  • 10
    Electronic Resource
    Electronic Resource
    Fracture Parameters on Three-Dimensional Sliding Mode Fracture (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 340-341 (June 2007), p. 447-452 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In the recent years three-dimensional (3D) elastic-plastic analyses have been conductedextensively for the opening mode (mode I) fracture and the constraint effects are discussed in detail.However less work is focused on other modes as sliding mode (mode II), tearing mode (mode III)or the mixed mode fracture in three-dimensional. In this paper the thickness effect on pure mode IIcase is discussed by the finite element method (FEM). Modified Boundary Layer (MBL) model isused, which has the ability to take into account the combined effects of the in-plane constraint(T-stress) and the out-of-plane constraint (finite thickness). The result demonstrates the weakthickness dependence on the near tip stress and strain fields under mode II loading. And the size ofthe 3D zone at mode II loading is determined to range from 1.0 to 1.2 times the thickness. Twofracture parameters of J integral and crack tip sliding displacement (CTSD) are discussed, which arealmost same at different thickness planes except those very near the surface. It is interesting to findthat the relations between J and CTSD keep linear at different thickness planes. T-stress issymmetry on stress and strain distributions along the crack plane. However its effects indicate weakthickness dependent on the CTSD and J integral fracture parameter
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/54/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.340-341.447.pdf
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