The Experts below are selected from a list of 1818 Experts worldwide ranked by ideXlab platform

M Jahazi - One of the best experts on this subject based on the ideXlab platform.

  • discrepancy between fatigue and dwell fatigue behavior of near Alpha Titanium Alloys simulated by cellular automata
    International Journal of Fatigue, 2013
    Co-Authors: N Boutana, Philippe Bocher, M Jahazi
    Abstract:

    Abstract Cellular automata were used to simulate microstructure heterogeneities at local (one grain) and global (aggregate of grains) levels in an attempt to better understand the large discrepancies observed between fatigue and dwell-fatigue behaviors of some Titanium Alloys. Eshelby theory was used to estimate the local stresses and strains developed in the microstructure. In the case of simple fatigue tests, loading and unloading stages were used to calculate and describe the strain accumulation history. For dwell fatigue analysis, a thirty second steady state at maximum load was applied to simulate the dwell period. In the present study, the local stress, strain and creep rate in each grain are calculated as a function of the mechanical properties of the neighboring grains. The data are then compiled and the overall behavior of the aggregate is predicted. The results can reproduce and explain some specific features observed experimentally in fatigue and dwell-fatigue tests of near Alpha Titanium Alloys.

  • microstructural modeling of cold creep fatigue in near Alpha Titanium Alloys using cellular automata method
    11th World Conf. on Titanium, 2007
    Co-Authors: N Boutana, Philippe Bocher, M Jahazi, David Piot, Frank Montheillet
    Abstract:

    It is well known that the presence of large heterogeneous textured regions in forged near Alpha Titanium Alloys could lead to large variations of mechanical properties when fatigue and creep cycles are applied at room temperature. On the other hand, experimental studies and microtexture investigations are complex to set up, lengthy and costly, and one cannot expect to understand the alloy behavior by relying only on empirical approaches. Hence, numerical methods are excellent alternatives for analyzing the influence of microscopic and macroscopic heterogeneities on mechanical properties in shorter times and with minimum need for experimentation. In the present investigation, a cellular automata (CA) method was used to simulate the effect of texture heterogeneities, on both local and global mechanical properties. A 2D array of cells was used and the stresses and strains developed in various heterogeneous regions were evaluated using the Eshelby theory. Using the CA method, various types of microstructures were modeled and compared with each other to quantify the influence of processing parameters on mechanical properties. The results predict, and are used to explain, the experimentally phenomena observed in creep responses during cold fatigue/creep tests of near Alpha Titanium samples

N Boutana - One of the best experts on this subject based on the ideXlab platform.

  • discrepancy between fatigue and dwell fatigue behavior of near Alpha Titanium Alloys simulated by cellular automata
    International Journal of Fatigue, 2013
    Co-Authors: N Boutana, Philippe Bocher, M Jahazi
    Abstract:

    Abstract Cellular automata were used to simulate microstructure heterogeneities at local (one grain) and global (aggregate of grains) levels in an attempt to better understand the large discrepancies observed between fatigue and dwell-fatigue behaviors of some Titanium Alloys. Eshelby theory was used to estimate the local stresses and strains developed in the microstructure. In the case of simple fatigue tests, loading and unloading stages were used to calculate and describe the strain accumulation history. For dwell fatigue analysis, a thirty second steady state at maximum load was applied to simulate the dwell period. In the present study, the local stress, strain and creep rate in each grain are calculated as a function of the mechanical properties of the neighboring grains. The data are then compiled and the overall behavior of the aggregate is predicted. The results can reproduce and explain some specific features observed experimentally in fatigue and dwell-fatigue tests of near Alpha Titanium Alloys.

  • microstructural modeling of cold creep fatigue in near Alpha Titanium Alloys using cellular automata method
    11th World Conf. on Titanium, 2007
    Co-Authors: N Boutana, Philippe Bocher, M Jahazi, David Piot, Frank Montheillet
    Abstract:

    It is well known that the presence of large heterogeneous textured regions in forged near Alpha Titanium Alloys could lead to large variations of mechanical properties when fatigue and creep cycles are applied at room temperature. On the other hand, experimental studies and microtexture investigations are complex to set up, lengthy and costly, and one cannot expect to understand the alloy behavior by relying only on empirical approaches. Hence, numerical methods are excellent alternatives for analyzing the influence of microscopic and macroscopic heterogeneities on mechanical properties in shorter times and with minimum need for experimentation. In the present investigation, a cellular automata (CA) method was used to simulate the effect of texture heterogeneities, on both local and global mechanical properties. A 2D array of cells was used and the stresses and strains developed in various heterogeneous regions were evaluated using the Eshelby theory. Using the CA method, various types of microstructures were modeled and compared with each other to quantify the influence of processing parameters on mechanical properties. The results predict, and are used to explain, the experimentally phenomena observed in creep responses during cold fatigue/creep tests of near Alpha Titanium samples

J C Williams - One of the best experts on this subject based on the ideXlab platform.

  • influence of hydrogen on dwell fatigue response of near Alpha Titanium Alloys
    Acta Materialia, 2020
    Co-Authors: V Sinha, R B Schwarz, M J Mills, J C Williams
    Abstract:

    Abstract The prior studies have investigated the influence of internal hydrogen on dwell-fatigue behavior of near-α Titanium Alloys primarily in the lamellar microstructural condition. In the current study, the effects of internal hydrogen, in the range 10–230 ppm (by weight), on the dwell-fatigue behavior of Ti-6242Si alloy were investigated. The examined alloy had a bimodal microstructure comprising approximately 70 vol% primary α grains and 30 vol% transformed β regions. The dwell-fatigue life generally increased with increasing hydrogen content. The dwell-fatigue lives were longer by a factor of as high as 6 for high (≥150 ppm) hydrogen contents than for the low ( 150 ppm) hydrogen contents. Specifically, these facets were inclined at ∼8 – 17° from the basal plane. Therefore, the longer dwell-fatigue lives observed for the Alloys with hydrogen contents ≥150 ppm could not be explained on the basis of any differences in crystallography of the facets at crack-initiation sites. The longer dwell-fatigue lives for higher hydrogen contents can be explained within the framework of time-dependent load shedding from the soft microtextured regions (MTRs) to the hard MTRs if the local stress redistribution at the soft MTR/hard MTR boundary due to the hold at maximum load is reduced with increasing hydrogen content.

  • effects of hydrogen on fatigue behavior of near Alpha Titanium Alloys
    Scripta Materialia, 2018
    Co-Authors: V Sinha, R B Schwarz, M J Mills, J C Williams
    Abstract:

    Abstract The influence of hydrogen content on fatigue response was examined for a near-α Titanium alloy, Ti-6Al-2Sn-4Zr-2Mo-0.1Si, in bimodal microstructural condition with ~70 vol% primary α. The hydrogen content was varied in the range 7–127 ppm (by weight). The fracture mechanism at crack-initiation sites changed from ductile tearing with localized plasticity in low (

Philippe Bocher - One of the best experts on this subject based on the ideXlab platform.

  • discrepancy between fatigue and dwell fatigue behavior of near Alpha Titanium Alloys simulated by cellular automata
    International Journal of Fatigue, 2013
    Co-Authors: N Boutana, Philippe Bocher, M Jahazi
    Abstract:

    Abstract Cellular automata were used to simulate microstructure heterogeneities at local (one grain) and global (aggregate of grains) levels in an attempt to better understand the large discrepancies observed between fatigue and dwell-fatigue behaviors of some Titanium Alloys. Eshelby theory was used to estimate the local stresses and strains developed in the microstructure. In the case of simple fatigue tests, loading and unloading stages were used to calculate and describe the strain accumulation history. For dwell fatigue analysis, a thirty second steady state at maximum load was applied to simulate the dwell period. In the present study, the local stress, strain and creep rate in each grain are calculated as a function of the mechanical properties of the neighboring grains. The data are then compiled and the overall behavior of the aggregate is predicted. The results can reproduce and explain some specific features observed experimentally in fatigue and dwell-fatigue tests of near Alpha Titanium Alloys.

  • dwell fatigue in near Alpha Titanium Alloys a multiscale interdisciplinary challenge
    ICF12 Ottawa 2009, 2009
    Co-Authors: Philippe Bocher, Florent Bridier, Lotfi Toubal, N Boutanai, E Uta, Nathalie Gey, Michel Humbert
    Abstract:

    A study was undertaken to examine the life dispersion of 15 specimens made of near-Alpha Titanium alloy (IMI 834) tested in dwell-fatigue loading conditions. Nucleation and propagation features were examined and results were discussed in relation with results obtained from experiments and simulations undertaken by the various authors of the present paper. Micromechanical mechanisms seem to play critical roles in the nucleation and propagation of cracks and the presence of strong local textures are thought to intensify and explain the dramatic scatter of dwell fatigue lifes.

  • microstructural modeling of cold creep fatigue in near Alpha Titanium Alloys using cellular automata method
    11th World Conf. on Titanium, 2007
    Co-Authors: N Boutana, Philippe Bocher, M Jahazi, David Piot, Frank Montheillet
    Abstract:

    It is well known that the presence of large heterogeneous textured regions in forged near Alpha Titanium Alloys could lead to large variations of mechanical properties when fatigue and creep cycles are applied at room temperature. On the other hand, experimental studies and microtexture investigations are complex to set up, lengthy and costly, and one cannot expect to understand the alloy behavior by relying only on empirical approaches. Hence, numerical methods are excellent alternatives for analyzing the influence of microscopic and macroscopic heterogeneities on mechanical properties in shorter times and with minimum need for experimentation. In the present investigation, a cellular automata (CA) method was used to simulate the effect of texture heterogeneities, on both local and global mechanical properties. A 2D array of cells was used and the stresses and strains developed in various heterogeneous regions were evaluated using the Eshelby theory. Using the CA method, various types of microstructures were modeled and compared with each other to quantify the influence of processing parameters on mechanical properties. The results predict, and are used to explain, the experimentally phenomena observed in creep responses during cold fatigue/creep tests of near Alpha Titanium samples

Vladimir V. Skripnyak - One of the best experts on this subject based on the ideXlab platform.

  • fracture of Titanium Alloys at high strain rates and under stress triaxiality
    Metals, 2020
    Co-Authors: Evgeniya G. Skripnyak, Vladimir V. Skripnyak
    Abstract:

    The present study investigates the effect of stress triaxiality on mechanical behavior and fracture of Ti-5Al-2.5Sn alloy in a practical relevant strain rate range from 0.1 to 1000 s−1. Tensile tests were carried out on flat smoothed and notched specimens using an Instron VHS 40/50-20 servo-hydraulic test machine. High-speed video registration was conducted by Phantom 711 Camera. Strain fields on the specimen gauge area were investigated by the digital image correlation method (DIC). The fracture surface relief was studied using digital microscope Keyence VHX-600D. Stress and strain fields during testing of the Ti-5Al-2.5Sn alloy were analyzed by the numerical simulation method. The evolution of strain fields at the investigated loading condition indicates that large plastic deformation occurs in localization bands. The alloy undergoes fracture governing by damage nucleation, growth, and coalescence in the localized plastic strain bands oriented along the maximum shear stresses. Results confirm that the fracture of near Alpha Titanium Alloys has ductile behavior at strain rates from 0.1 to 1000 s−1, stress triaxiality parameter 0.33 < η < 0.6, and temperature close to 295 K.

  • INVITED: Fracture of Alpha Titanium Alloys at high strain rates and stress triaxiality
    2018
    Co-Authors: Evgeniya G. Skripnyak, Alexander A. Kozulyn, Vladimir V. Skripnyak
    Abstract:

    The aim of this work was the evaluation of combined effect of stress triaxiality and strain rate on the mechanical behavior of the Alpha Titanium Alloys. Mechanical behaviour of Titanium alloy Grade 6 (VT 5-1 or Ti-5Al-22,5Sn ) and Grade 2 (VT1-0) in a range of strain rates from 0.001 to 1000 1/s and stress triaxiality (0.3–0.6) at room temperature was studied using an Instron VHS 40 / 50-20 servo-hydraulic test machine. Analysis of stress state and strain distribution in smooth and notched samples under tension was carried out by means of computer simulation and analytical relations. The Gurson-Tvergaard-Needleman model, complemented with phenomenological laws for voids nucleation, growth and coalescence, was adopted for describing the fracture of the Alpha Titanium Alloys. It was shown that stress triaxiality is important for prediction of damage evolution and fracture of Alpha Titanium Alloys at high strain rates. The constitutive equation and fracture models have been validated by simulating the tension tests. It was obtained that strain localization phenomena play a major role in the fracture process at lower triaxiality. It is found that the strain to fracture of Alpha Titanium alloy is strongly depended on the stress triaxiality and strain rate above 100 s -1 . The strain to failure of Alpha Titanium Alloys at room temperature decrease by 3.7 times with increasing stress triaxiality from 0.3 to 0.6 in wide range of strain rates.