Papers by Keyword: Compressive Stress

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Authors: Valentin V. Emtsev, Boris A. Andreev, Gagik A. Oganesyan, D.I. Kryzhkov, Andrzej Misiuk, Charalamos A. Londos, M.S. Potsidi
Abstract: Effects of compressive stress on oxygen agglomeration processes in Czochralski grown silicon heat treated at T= 450OC, used as a reference temperature, and T= 600OC to 800OC are investigated in some detail. Compressive stresses of about P= 1 GPa lead to enhanced formation of Thermal Double Donors in materials annealed over a temperature range of T= 450OC – 600OC. It has been shown that the formation of thermal donors at T= 450OC under normal conditions and compressive stress is accompanied with loss of substitutional boron. In contrast, the concentration of the shallow acceptor states of substitutional boron in silicon annealed under stress at T≥ 600OC remains constant. An enhancement effect of thermal donor formation is gradually weakened at T≥ 700OC. The oxygen diffusivity sensitive to mechanical stress is believed to be responsible for the observed effects in heat-treated silicon.
Authors: Li Ping Liang, Xuan Cheng, Ying Zhang
Abstract: A lanthanum doped lead zirconate titanate (PLZT) ceramic specimen was prepared by the conventional solid state reaction method. The crystal phase and morphology of the PLZT specimen were characterized by XRD and SEM techniques, with the hysteresis loop by RT6000HVS system. The compressive stress was applied to the PLZT specimen through the microtest mechanical loading device. In-situ Raman spectra focused on a fixed grain under various compressive stresses were recorded for different polarization directions of the scattered light. The effects of stresses on the Raman spectra and the intensity ratio between the E+B1 and E(2TO) modes are discussed.
Authors: Katsuaki Furukawa, Yasuo Ochi
Authors: Xiu Shan Wang, Tuan Jie Chen, Xiao Jun Ding
Abstract: In order to study the rutting problem of asphalt pavement, this paper sets up a three-dimensional model of asphalt pavement with finite element. By analyzing the mechanical response of high-modulus asphalt concrete at different layers, this paper finds out the layer set of high-modulus asphalt concrete. At the same time, it further analyzes the influence of the modulus’ size and thickness of the high-modulus asphalt concrete on the load-carrying capability of road structure. The results show that high-modulus asphalt concrete can significantly restrain rutting problem and the recommend ideal modulus is between 2000MPa and 2500MPa; the ideal thickness ranges from 5cm to 7cm.
Authors: Muangjai Unruan, R. Wongmaneerung, Yongyut Laosiritaworn, Supon Ananta, Rattikorn Yimnirun
Abstract: In this work, effects of compressive stress on the ferroelectric properties of 0.7PMN–0.3PT ceramics were investigated. The ceramics with the formula (0.7)Pb(Mg1/3Nb2/3)O3-(0.3)PbTiO were prepared by a conventional mixed-oxide method. The ferroelectric properties under compressive stress were observed at stress up to 80 MPa using a compressometer in conjunction with a modified Sawyer-Tower circuit. The results showed that applied stress had a significant influence on the ferroelectric properties of 0.7PMN–0.3PT ceramics. Ferroelectric characteristics, i.e. the area of the ferroelectric hysteresis (P-E) loop, the saturation polarization (Psat), the remanent polarization (Pr) and loop squareness (Rsq), decreased with increasing compressive stress, while the coercive field (Ec) remained relatively constant. Stress-induced domain wall motion suppression and non-180oC ferroelectric domain switching processes are responsible for the changes observed.
Authors: Bao Sheng Zhang, Michael M. Gasik, A. Facchini, M. Pressacco, P. DallaPria, S. Posocco
Abstract: Computer-integrated safe design of FGM component for hip replacement prosthesis was presented based on principle of optimal stresses distribution in the FGM component. The goals were to create an FGM structure with reasonable compressive stresses on the surfaces (subjected to wear) and to keep them during the entire manufacturing cycle (sintering, machining, assembling and application). The residual stresses developed in the different parts of the composite were implemented into the subsequent process of the surface grinding and assembly to simulate properly the whole processing route to ensure optimal combination of the processing parameters.
Authors: Sasiporn Prasertpalichat, Muangjai Unruan, Thanapong Sareein, Jirapa Tangsritrakul, Athipong Ngamjarurojana, Supon Ananta, Rattikorn Yimnirun
Abstract: Apart from aging effect, barium titanate ceramics usually subjected to the mechanical loading when it is used in electronic device. Thus, it is very interesting to investigate the influence of various compressive stresses on ferroelectric aging behavior of Ba(Ti0.99-xFe0.01Nbx)O3 , x=0.005-0.015. In this study, the P-E hysteresis loops were observed by using compressometer in conjunction with a modified Sawyer-Tower circuit. The stress level was varied from 0 to 185 MPa. The results showed that the dissipation energy, saturation polarization (Psat), remnant polarization (Pr) and the coercive field (Ec) decreased with increasing of stress. The aging behavior was still observed in acceptor-dominant of hybrid doped ceramics. The aging was also enhanced under application of the external stress. The explanation based on the defect-dipole and domain-reorientation processes was discussed.
Authors: Chang Hai Zhou, Rui Yun Pan, Hai Tao Ma
Abstract: The oxidation behavior of Fe-20Ni alloy under compressive stress in air was studied at 800, 900 °C. The results examined by using scanning electron microscope (SEM) and X-ray diffraction (XRD) indicates that the oxide scales were consisted of an external scale and a subscale which has an intragranular scale (above 5 h at 800 °C and 900 °C) and an intergranular scale. Compared with the unstressed specimen, the growth kinetics of external scale was accelerated by an applied compressive stress. Besides, the compressive stress induced an increase in the growths of intragranular scale and intergranular scale formed on the specimens oxidized at 900 °C. However, the effect of compressive stress on the growth of intergranular scale and intragranular scale was not obvious in the case of 800°C. In addition, cracks developed in the subscale for the specimens oxidized under 2.5 MPa compressive stress when the oxidation time exceeded 20 h.
Authors: Bin Peng, Zhen Xing Yue
Abstract: Uniaxial compressive stress was applied during fatigue process of soft lead zirconate titanate piezoelectric ceramics and their fatigue resistance was improved when the stress was larger than 20MPa. Before fatigue, compressive stress had a strong depolarization effect and restricted domains switching behavior under large electric field and domain walls motion under small electric field. However, in a partially fatigued state, while domains switching behavior was still restricted by compressive stress, domain walls motion was enhanced. Removal of the applied stress after partial fatigue induced the remnant polarization restored significantly.
Authors: Shou Bin Zhang, Wei Juan Li
Abstract: The thermal expansion curves are measured by Gleeble-1500 thermomechanical simulator for Cr-Mo steel during continuous cooling transformation at the cooling rate ranging from 1°/s to 90° /s, and CCT curve is also determined; The thermal expansion curves of continuous cooling transformation are measured under the axial compressive stresses (40MPa, 80MPa and 120MPa) at the cooling rates of 50° /s, 70° /s and 90° /s respectively, then the CCT curves with applied compressive stress are determined. The transformation microstructures of steel after continuous cooling with and without stress are observed by SEM and TEM, and the hardness is measured by Vickers hardness tester. The results show that the Bs is increased and Bf is decreased owing to the effect of applied compressive stress; At the meantime the microstructure is also changed, with increasing applied compressive stress, the quantity of granular bainite, bulk ferrite and carbide increase gradually except lath bainite,the lath width of lath bainite becomes narrower gradually, and original grain boundaries become bent from straight; The hardness of transformation structure becomes lower with increasing applied compressive stress exceeding 40Mpa after continuous cooling.
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