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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
    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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  • 4
    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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  • 5
    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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  • 6
    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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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Study of Initiator’s Shock-Resistibility Through Impact Using Hopkinson Pressure Bar (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 33-37 (Mar. 2008), p. 401-406 
    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 attempted to study the properties of Slapper detonator non-energetic elementsthrough exerting impact on them by Hopkinson Pressure Bar and evaluating the acceleration thatsamples received in accordance with one-dimensional stress wave theory. The results showed that thevelocity pulse width could be controlled and acceleration pulse width be improved by varying thepulse shaper material and strike bar length. And the critical acceleration causing the failure of theinitiator was closely connected with acceleration pulse width as well as acceleration amplitude. Whenthe strike bar length were 126 mm, 190 mm, 270 mm and 460 mm, the acceleration pulse width were58 μs, 93 μs, 130 μs and 160 μs, respectively, and the critical acceleration causing the failure of theinitiator were about 240 000 g, 130 000 g, 74 000 g and 72 000 g, respectively. The accurateness andreliability of acceleration value was accredited to the methods of changing sampling frequency,smoothing velocity and acceleration curve, and fitting curve. The FEM analog simulation was alsoconducted by using the LS-DYNA finite element program. Good agreements were achieved betweenthe acceleration curve and the simulation results
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/40/transtech_doi~10.4028%252Fwww.scientific.net%252FAMR.33-37.401.pdf
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  • 9
    Electronic Resource
    Electronic Resource
    Analysis of the Anti-Bird Impact Performance of Typical Beam-Edge Structure Based on ANSYS/LS-DYNA (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 33-37 (Mar. 2008), p. 395-400 
    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 3-D finite element analysis model of beam-edge structure with spaced multiple layersunder bird impact is established. Numerical simulations are implemented by using the non-linearcontact-impact code ANSYS/LS-DYNA when the birds collide at three locations of the structurerespectively. The failure process of the structure and the equivalent plastic strain at supports areobtained. The residual strength of the structure after impact is predicted. The results show that thefront spars are penetrated or cracked after the leading edge is perforated. The equivalent plastic strainat the support is much higher when the bird impacts the structure at the central location. Both thestructure deformation and failure mode from the simulation are consistent with the results of full scaletest, which proves the validity of the method proposed in this paper
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/40/transtech_doi~10.4028%252Fwww.scientific.net%252FAMR.33-37.395.pdf
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  • 10
    Electronic Resource
    Electronic Resource
    A Simple Method in Preventing Numerical Fractures of SPH Computations (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 33-37 (Mar. 2008), p. 845-850 
    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 non-triangulation inserting particle method is presented to prevent numerical fractures ofSPH computations. The particles in those regions in which numerical fractures may occur are chosenat the beginning of SPH computations. And, the chosen particles are arrayed by the two different rulesrespectively according to the particle position relations. When the distance between each two chosenconnected particles exceeds a certain value and neither of the corresponding two particles hasfractured in SPH computations, a new particle is generated between those two ones and the positionrelation of particles is updated. The physical quantities that the new particle carries are obtainedaccording to some given rules. The method and the same type of method in the reference arecompared. The application of the method is analyzed. Conservation of mass and Conservation ofmomentum of the whole system are kept in this method. Several examples are given to validate theefficiency of the method to prevent numerical fractures
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/40/transtech_doi~10.4028%252Fwww.scientific.net%252FAMR.33-37.845.pdf
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