Entity

Time filter

Source Type


Wang J.,Tianjin University | Zhao N.,State Key Laboratory of Hydraulic Engineering Simulation and Safety | Zhao N.,Tianjin University | Nash P.,Illinois Institute of Technology | And 4 more authors.
Journal of Alloys and Compounds | Year: 2013

Bulk Ti2AlC-Al2O3/TiAl composites were in situ synthesized by vacuum sintering mechanically alloyed Ti-50 at.% Al powders coated with carbon nanotubes (CNTs). The pre-alloyed Ti-50 at.% Al powder was obtained by ball milling Ti and Al powders. The multi-walled carbon nanotubes as the carbon resource were covered on the surface of the pre-alloyed powders by immersing them into a water solution containing the CNTs. A zwitterionic surfactant was used to enhance the dispersion of the CNTs on the powder surface. The samples were cold pressed and sintered in vacuum at temperatures from 950 to 1250 °C, respectively. The results show that the reaction of forming Ti2AlC can be achieved below 950 °C, which is 150 °C lower than in the Ti-Al-TiC system and 250 °C lower than for the Ti-Al-C system due to the addition of CNTs. Additionally, the reinforcement of Al2O3 particles was introduced in situ in Ti2AlC/TiAl by the drying process and subsequent sintering of the composite powders. Dense Ti 2AlC-Al2O3/TiAl composites were obtained by sintering at 1250 °C and exhibited a homogeneous distribution of Ti 2AlC, Al2O3 and precipitated Ti3Al particles and a resulting high hardness. © 2013 Elsevier B.V. All rights reserved. Source


Wang J.-H.,Tianjin University | Wang J.-H.,State Key Laboratory of Hydraulic Engineering Simulation and Safety | Liu J.-L.,Tianjin University | Liu J.-L.,State Key Laboratory of Hydraulic Engineering Simulation and Safety | Zhou Y.-R.,China Oilfield Services Ltd.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2012

Load-controlled model tests are conducted to study the bearing capacities of suction anchors with taut mooring systems under combined static and cyclic loads at the optimal loading point using an electric servo loading apparatus developed by the authors. Failure modes of anchors, effects of static loads on cyclic bearing capacities and variations of cyclic bearing capacities with the number of cycles to failure are analyzed based on test results. The following conclusions are drawn. Failure of anchors is the translational failure mode of pullout from the soft stratum if the vertical ultimate resistance acting on anchors is less than the lateral one acting on anchors under combined static and cyclic loads. The displacement along the mooring direction at the loading point is about 0.6 times the anchor diameter when anchors are in the ultimate states under static loads. The cyclic bearing capacity of anchors increases with the increase of static load ratios and the cyclic load withstood by anchors also depends on static load ratio for a specified number of cycles to failure. The cyclic load withstood by anchors is the maximum when the static load ratio is about 0.5. Cyclic bearing capacities of anchors decrease with the increase of the number of cycles to failure for a specified static load ratio. The effect of loading directions on the variation of the cyclic bearing capacity with the number of cycles to failure is not obvious when the loading direction varies from 30 to 40 degrees for a specified static load ratio. The cyclic bearing capacity of anchors is not less than 75% of the static bearing capacity if the static load ratio is greater than 0.5 and the number of cycles to failure is less than 1000. Source


Wang J.,Tianjin University | Wang J.,State Key Laboratory of Hydraulic Engineering Simulation and Safety | Liu J.,Tianjin University | Liu J.,State Key Laboratory of Hydraulic Engineering Simulation and Safety | Yang Y.,Tianjin Xince Eletronics Apparatus Technology Co.
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2012

Suction anchors subjected to inclined loads at the optimal load attachment point are an important taut mooring foundation of deepwater floating production and storage facilities. Sediments in the deepwater areas are generally soft clay with high water contents. It is important for designers to understand failure modes and bearing capacities of suction anchors with taut mooring system in soft clay. Geometry characteristic parameters of anchors, shear strengths of strata and loading cases may be main factors affecting failure modes and bearing capacities of suction anchors. In order to better understand variations of failure modes and bearing capacities resulting from variations of various affecting factors, model tests were conducted under 1g condition for suction anchors with taut mooring system in soft clays. Effects of the friction resistance of the outside wall, geometric characteristic parameters, the variation of soil shear strength along the depth, the loading direction and cyclic loads on the failure mode and the bearing capacity of suction anchors with taut system were studied. Following conclusions were obtained based on model test results. There are three typical failure modes for suction anchors subjected to the inclined load at the optimal load attachment point: (1) the anchor failure is the vertical pullout mode if the vertical ultimate resistance of an anchor is less than the lateral ultimate resistance; (2) the anchor failure is the mode of lateral squeezing strata if the vertical ultimate resistance of an anchor is larger than the lateral ultimate resistance; (3) the anchor failure is the mode of squeezing strata along the inclined upward direction if the lateral ultimate resistance of an anchor is close to the vertical ultimate resistance. For specified stratum, the loading direction and the load case, the failure mode can be changed to increase the bearing capacity of an anchor by optimizing geometric parameters of an anchor. If the lateral ultimate resistance of an anchor is less than the vertical ultimate resistance, the bearing capacity of the anchor does not increase with the increase of the vertical ultimate resistance. The failure of anchors is always the vertical pullout mode if the vertical ultimate resistance of an anchor is less than the lateral ultimate resistance when the loading direction angle from the horizontal decreases from 40 degree to 20 degree for suction anchors with taut mooring system. The cyclic load is an important factor affecting the failure mode and the bearing capacity. The degradation of the vertical ultimate resistance is larger than the degradation of the lateral ultimate resistance under cyclic loads. The failure of an anchor is still the vertical pullout mode under combined static and cyclic loads if the failure of an anchor is the vertical pullout mode under static loads. If the failure of an anchor is lateral failure mode strata under static loads, the failure mode of the anchor will depend on the cyclic degradation of the vertical ultimate resistance under combined static and cyclic loads. When model test results were predicted using the limiting equilibrium analysis method, predicted bearing capacities were basically in agreement with model test results and predicted failure modes were only in qualitative agreement with test results. Copyright © 2012 by the International Society of Offshore and Polar Engineers (ISOPE). Source


Li S.,State Key Laboratory of Hydraulic Engineering Simulation and Safety | Yang M.,State Key Laboratory of Hydraulic Engineering Simulation and Safety
Shuili Fadian Xuebao/Journal of Hydroelectric Engineering | Year: 2012

When an automatic tilting water gate is operating, instability could occur such as frequent swinging, flapping and random hydraulic acting, and these instable phenomena directly impact structure security and project efficiency. To simulate the hydrodynamic loads on such a gate, in this paper a 3-D large eddy simulation (LES ) turbulence model is developed in combination with a volume-of-fluid free-surface tracking technique, and its results agree quite well with the measurements of physical model tests. It is used to analyze the the gate conditions of dynamic and static balances. The results show that if the standard deviation of fluctuating pressures on both surfaces of the gate is below 1.4 Kpa or the opening angel is large, the gate will operate in a good stability condition. The stability index proposed in this paper for evaluation of the tilting gate's stability provides a reliable criterion for similar designs. © Right. Source


Le C.-H.,State Key Laboratory of Hydraulic Engineering Simulation and Safety | Le C.-H.,Tianjin University | Ding H.-Y.,State Key Laboratory of Hydraulic Engineering Simulation and Safety | Ding H.-Y.,Tianjin University | Zhang P.-Y.,Tianjin University
Gongcheng Lixue/Engineering Mechanics | Year: 2013

For towing stability, sinking, fine leveling construction and structural strength purposes, it is necessary to set bulkheads in the concrete bucket foundation. Usually the influence of bulkheads on the bearing capacity of a foundation is not considered, however, bulkheads actually have a certain influence on the bearing mode and bearing capacity. The influence of bulkheads on the bearing mode was quantitatively analyzed by the comparison of two concrete bucket foundations with and without bulkheads. The results show that the bearing modes of two foundations with and without bulkheads are similar. No obvious effect on the bearing capacity when the load is small, so it is reasonable that not to consider the role of the bulkheads in foundation design, but as the load increases, the effect of bulkheads on the bearing capacity improvement gradually appears, when the bucket foundation reaches the ultimate bearing capacity, 6.9% of vertical bearing capacity, 18.3% of horizontal bearing capacity and 16.5% of bending bearing capacity increase, which means that in extreme conditions a concrete bucket foundation with bulkheads will have greater safety margin. Source

Discover hidden collaborations