Applied Mechanics and Materials Vols. 166-169

Abstract: Fractured rocks are the main oil and gas exploration objects offshore in China in recent years, which include the fractured sandstone, carbonate, volcanic rock, coal methane bed, shale gas and so on. The accurate calculation of the rock mechanics parameters (elastic modulus and Poisson’s ratio) play remarkable role in petroleum engineering operations, such as borehole stability, mud density window determination, perforation, EOR, in-situ stress predication and so on. Now the applications show that the in-situ stress estimation based on the rock parameters obtained by acoustic logging is much different from the downhole measurement with wireline formation tester. The pore space of the fractured rock contains fracture and cave and it is different from sandstone. In the paper a novel method based on the effective media theory with well logging for the rock mechanics parameters calculation of the fractured rock is introduced, and some problems and potential application are also discussed.

Abstract: For polycrystalline Beryllium (Be) specimens, data of yield strength, ultimate strength, elastic modulus, inelastic secant modulus elongation and grain size were obtained by using of material testing machine and metaloscope. It showed that: elastic modulus, inelastic secant modulus were basically independent with grain size; ultimate strength appeared at the end of tension process; relation between rate of yield strength to ultimate strength and elongation was found to be linear, but this rate had no clear correlation with grain size; relation between strength (yield, ultimate) and grain size was satisfied with Hall-Petch equation. Based on test data and analysis above, a bilinear model was given to simulate stress-strain constitutive behavior; an equation expressing relation between elongation and grain size was also derived.

Abstract: This paper focuses on mechanical properties of RAC, and other relevant characteristics of RAC, also made lateral comparison with NAC. Paper attend to find some features need to pay attention, at the end of paper author determined strength of RAC.

Abstract: This paper starting from the original grey differential equations, through finding the relationship between the raw data and the derivative of its , constructed a new white differential equation which equal to the original grey differential equation, at the same time, getting the new GM(1,1)model which closer to the changes of data. Through the modeling and prediction of the standard index series, this model not only adapts to low growth index series, but also adapts to high-growth index series, and the simulation accuracy and prediction accuracy are high.

Abstract: The Front-mounted Water Separation Propeller is a new-type energy saving propulsion device, on which it’s necessary to make research. A numerical simulation on the hydrodynamic performance of the Front-mounted Water Separation Propeller by RANS method was performed. The simple ship models with and without Front-mounted Water Separation Propeller were established and meshed by using hybrid grid. The drag performances of the ship model with and without Front-mounted Water Separation Propeller were performed separately by using Kω-SST turbulence model and VOF model. The method provided in this article is proved to be effective by make comparison between the simulation results and the model test results. The results show that the ship resistance can be reduced by using the Front-mounted Water Separation Propeller.

Abstract: LNR and LRB in which the value of shear modulus of inner rubber is 0.392MPa have been widely used in the practical isolation projects, although there are some test researches about dependency of shear property of them, but there is little complete study under high design compressive stress, such as 15MPa, and equations of dependency of shear property of them have seldom been found. In this paper, completely experiments about dependency of shear property of them have been done, and the fitted equations about various dependencies for LNR and LRB are given. Effect of size of rubber bearing on various dependencies is also studied. Formulas of determination of parameters in bilinear model of LRB are proposed, and have been testified well with FEA program.

Abstract: The principle of the structure of displacement function, the establishment of governing equations, level set method were briefly outlined in this paper. Numerical simulations on three dimensional single edge notched specimens with different crack length in tension were performed using Abaqus software based on extended finite element method (XFEM), the stress intensity factor at static crack front was analyzed and the simulated results were in good agreement with analytical solutions. Numerical simulations in the present paper indicated that the extended finite element method is very suitable to deal with nonlinear fracture problems.

Abstract: Finite element model updating using incomplete complex modal data for unsymmetrical damping system with genetic algorithm is presented. The genetic algorithm method and finite element model updating based on optimization method using complex modal eigenvalue are introduced. The updating for simulation example about a flexible rotor system which is a typical unsymmetrical damping system is performed using bearing stiffness, bearing damping and diameter moment of inertia parameters. The results show that the maximum error of updated parameters is 0.15% and the objective function of genetic algorithm is 0.0081. The study demonstrates that the finite element model updating method using incomplete complex modal data with genetic algorithm is feasible and effective for unsymmetrical damping system.

Abstract: Strength theory research in concrete, a brittle material, widely used in civil, hydraulic, mining and other engineerings,is of significant meaning.At first, based on the twin τ2 strength theory in this paper, the twin τ2 strength theory of two parameters is derived under the complex stress state in this paper. The relation among the compressive strength and tensile strength is proposed. Secondly, the brittle failure of concrete is analyzed by using the twin τ2 strength theory of two parameters and compared with the available experimental data for some concrete materials. At last, middle principal stress effect is discussed. The results of the twin τ2 strength theory of two parameters are shown to be satisfactory.

Abstract: Venturi Scrubbers are used in filtered vented containment system (FVCS) for collection of aerosols produced in NPP in severe accidents. Therefore, venturi scrubber (VS) needs an attention to design it properly and improved in all aspects. In this research, CFD simulations of prediction of pressure drop in venturi scrubber has been carried out. ANSYS CFX tool is used to obtain the simulation results. k-ε turbulence model is employed to study the fluid dynamics of the venturi scrubber. Mesh size plays an important role for convergence and accuracy of results. Therefore, the mesh independency is checked for optimized mesh size.