The Experts below are selected from a list of 163641 Experts worldwide ranked by ideXlab platform
P Huang - One of the best experts on this subject based on the ideXlab platform.
-
depth Dependent Strain rate sensitivity and inverse indentation size effect of hardness in body centered cubic nanocrystalline metals
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2014Co-Authors: Jiyuan Zhao, Fei Wang, P HuangAbstract:Abstract Size effects on hardness ( H ) and Strain rate sensitivity ( m ) of nanocrystalline (NC) body-centered cubic Mo thin film were examined under nanoindentation testing. Contrast to existing reports that there was no indentation size effect on hardness in NC metals, inverse indentation size effect (ISE) in NC Mo was observed for the first time at penetration depths ranging from 15 to 200 nm, at all the loading Strain rates applied. In addition, the Strain rate sensitivity of NC Mo exhibited strong dependence on penetration depth, increasing dramatically with decreasing penetration depth. Surface effects related to two deformation mechanisms were proposed to be responsible for the observed inverse ISE on H and depth Dependent m . Specifically, the mobility of screw dislocation/component and the diffusion length of interfacial diffusion were altered as the deformed region underneath the indenter was approaching the free surface, resulting in the unusual size effects in NC Mo.
-
grain size Dependent Strain rate sensitivity in nanocrystalline body centered cubic metal thin films
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2014Co-Authors: Qing Zhou, Fei Wang, Jiyuan Zhao, J Y Xie, P HuangAbstract:Abstract The Strain rate sensitivity (m) and activation volume (v⁎) of three nanocrystalline (NC) body-centered cubic (bcc) metals, i.e., W, Mo and Ta, with various grain sizes were evaluated by nanoindentation testing. Opposite to the conventional trend that NC bcc metals exhibit reduced m as the grain size was decreased, elevated m was observed as the grain size was reduced from ~90 nm to ~30 nm for all the samples concerned. It was proposed that the unusual variation trends of m for NC bcc metals were dominated by GB-related mechanisms when the grain size drops below a critical value.
Jiwei Zhai - One of the best experts on this subject based on the ideXlab platform.
-
effect of different templates on structure evolution and large Strain response under a low electric field in textured lead free bnt based piezoelectric ceramics
Journal of The European Ceramic Society, 2015Co-Authors: Junhua Xi, Jun Zhang, Bo Shen, Jiwei ZhaiAbstract:Abstract -textured 0.83Na0.5Bi0.5TiO3–0.17Bi0.5K0.5TiO3 (BNT–BKT) ceramics with high degree of texturing (>80%) were synthesized by templated grain growth using different perovskite plate-like BaTiO3, SrTiO3 and NaNbO3 as template particles to develop lead-free piezoelectric materials with an excellent actuating performance. The effects of different template particles addition to BNT–BKT ceramics on the grain orientation, structure evolution, phase stability and macroscopic functional properties was systematically investigated. BaTiO3 template particles addition to form -textured BNT–BKT–BT textured ceramics suppresses an electric-field-induced long-range ferroelectric order, giving rise to a high field-induced Smax/Emax of 710 pm/V under a relatively low driving field of 45 kV/cm compared with existing lead-free Bi-perovskite ceramics. In particular, temperature-Dependent Strain response reveals that -textured BNT–BKT–5BT ceramics exhibit not only large Smax/Emax at a low driving field of 45 kV/cm at room temperature but also enhanced the temperature stability of Smax/Emax featured by large Smax/Emax of 517 pm/V at high temperature.
-
the composition and temperature Dependent structure evolution and large Strain response in 1 x bi0 5na0 5 tio3 xba al0 5ta0 5 o3 ceramics
Journal of the American Ceramic Society, 2013Co-Authors: Yanlong Bian, Bo Shen, Jiwei ZhaiAbstract:The (1−x) (Bi0.5Na0.5)TiO3−xBa(Al0.5Ta0.5)O3((1−x)BNT-xBAT) lead-free piezoceramics was fabricated using a conventional solid-state reaction method. The temperature and composition-Dependent Strain behavior, dielectric, ferroelectric (FE), piezoelectric, and pyroelectric properties have been systematically investigated to develop lead-free piezoelectric materials with large Strain response for actuator application. As the BAT content increased, the FE order is disrupted resulting in a degradation of the remanent polarization, coercive field, and the depolarization temperature (Td). A large Strain of 0.36% with normalized Strain d33* = 448pm/V was obtained for the optimum composition x = 0.045 at room temperature. The bipolar and unipolar Strains for the compositions x = 0.035 and x = 0.04 reach almost identical maximum values when the temperature is in the vicinity of their respective depolarization temperature (Td). The Raman-spectra analysis, macroscopic properties, thermal depolarization results, and temperature-Dependent relationships of both polarization and Strain demonstrated that the origin of the large Strain response for this investigated system is attributed to a field-induced relaxor to FE phase transformation.
Jiyuan Zhao - One of the best experts on this subject based on the ideXlab platform.
-
depth Dependent Strain rate sensitivity and inverse indentation size effect of hardness in body centered cubic nanocrystalline metals
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2014Co-Authors: Jiyuan Zhao, Fei Wang, P HuangAbstract:Abstract Size effects on hardness ( H ) and Strain rate sensitivity ( m ) of nanocrystalline (NC) body-centered cubic Mo thin film were examined under nanoindentation testing. Contrast to existing reports that there was no indentation size effect on hardness in NC metals, inverse indentation size effect (ISE) in NC Mo was observed for the first time at penetration depths ranging from 15 to 200 nm, at all the loading Strain rates applied. In addition, the Strain rate sensitivity of NC Mo exhibited strong dependence on penetration depth, increasing dramatically with decreasing penetration depth. Surface effects related to two deformation mechanisms were proposed to be responsible for the observed inverse ISE on H and depth Dependent m . Specifically, the mobility of screw dislocation/component and the diffusion length of interfacial diffusion were altered as the deformed region underneath the indenter was approaching the free surface, resulting in the unusual size effects in NC Mo.
-
grain size Dependent Strain rate sensitivity in nanocrystalline body centered cubic metal thin films
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2014Co-Authors: Qing Zhou, Fei Wang, Jiyuan Zhao, J Y Xie, P HuangAbstract:Abstract The Strain rate sensitivity (m) and activation volume (v⁎) of three nanocrystalline (NC) body-centered cubic (bcc) metals, i.e., W, Mo and Ta, with various grain sizes were evaluated by nanoindentation testing. Opposite to the conventional trend that NC bcc metals exhibit reduced m as the grain size was decreased, elevated m was observed as the grain size was reduced from ~90 nm to ~30 nm for all the samples concerned. It was proposed that the unusual variation trends of m for NC bcc metals were dominated by GB-related mechanisms when the grain size drops below a critical value.
Dirk Mohr - One of the best experts on this subject based on the ideXlab platform.
-
anisotropic plasticity model coupled with lode angle Dependent Strain induced transformation kinetics law
Journal of The Mechanics and Physics of Solids, 2012Co-Authors: Allison M Beese, Dirk MohrAbstract:Abstract A phenomenological macroscopic plasticity model is developed for steels that exhibit Strain-induced austenite-to-martensite transformation. The model makes use of a stress-state Dependent transformation kinetics law that accounts for both the effects of the stress triaxiality and the Lode angle on the rate of transformation. The macroscopic Strain hardening is due to nonlinear kinematic hardening as well as isotropic hardening. The latter contribution is assumed to depend on the dislocation density as well as the current martensite volume fraction. The constitutive equations are embedded in the framework of finite Strain isothermal rate-inDependent anisotropic plasticity. Experimental data for an anisotropic austenitic stainless steel 301LN is presented for uniaxial tension, uniaxial compression, transverse plane Strain tension and pure shear. The model parameters are identified using a combined analytical–numerical approach. Numerical simulations are performed of all calibration experiments and excellent agreement is observed. Moreover, we make use of experimental data from ten combined tension and shear experiments to validate the proposed constitutive model. In addition, punch and notched tension tests are performed to evaluate the model performance in structural applications with heterogeneous stress and Strain fields.
Ulrich W Suter - One of the best experts on this subject based on the ideXlab platform.
-
non linear rate Dependent Strain hardening behavior of polymer glasses
Polymer, 2005Co-Authors: Michael Wendlandt, Theo A Tervoort, Ulrich W SuterAbstract:Abstract This study is concerned with the finite, large Strain deformation behavior of polymeric glasses. True stress–Strain curves in uniaxial compression obtained for five different polymeric glasses: polycarbonate, polystyrene, poly(2,6-dimethyl-1,4-phenylene oxide), and linear and cross-linked poly(methylmethacrylate), revealed a Strain-hardening response during plastic deformation that is Strain-rate Dependent and deviates from neo-Hookean behavior. An empirical modification of the so-called compressible Leonov model by a Strain Dependent activation volume is suggested, which describes the Strain-rate Dependent large Strain behavior of these glassy polymers in good agreement with experimental data.