Applied Mechanics and Materials Vols. 204-208

Abstract: Through methods, such as microscope analysis, mechanical analysis, chemical analysis, metallography examination and scanning electron microscope etc, the causes resulting in lots of tube socket cracks of supercritical boiler water wall header (15CrMo) have been analyzed. The result indicates failure of the supercritical boiler water wall header tube sockets are the ductile fracture and belong to thermal stress crack. The unreasonable structure, excessive thermal stress between header and sockets are the primarily inducement of crack failure.

Abstract: The structures of nozzle outlet have great effects on jet noise generated by submerged gas jet. Five nozzles with different cross-sections were designed to study the influences of nozzle structures on sound levels by experimental methods. The flow characteristics and sound pressure levels were measured and the gas-liquid flows formed by submerged gas jets under different Weber numbers were also observed. The results show that the gas-liquid flows transformed from bubbling regime to jetting regime with the increase of Weber numbers. With respect to bubbling flow, no significant differences in sound levels for different nozzles were found. However, a remarkable increase of acoustic emission was caused by the transformation of flow patterns over the frequency bands of 0.6-4 kHz for all nozzles. In addition, sound pressure levels for elliptical nozzle were much lower than those of other nozzles over the frequency bands of 0.6-4 kHz. Therefore, it would be a reasonable strategy to adopt several elliptical orifices instead of round nozzle to reduce the gas jet noise in the design of underwater exhaust muffler.

Abstract: The shaft lining under the deep alluvium drainage and grouting settlement stratum are in the complex dynamic force state, the stresses of shaft lining have a relation to the consolidation settlement of strata, the transmission coefficient of bottom aquifer and the coupling effect between shaft lining and surrounding soil. To study the variation law about vertical additional force of shaft lining, this paper analyzes reinforced concrete monolayer shaft lining by numerical simulation method, obtaining that vertical additional force of monolayer shaft lining is proportional to the modulus of elasticity of shaft lining concrete and it is proportional logarithm to the transmission coefficient of bottom aquifer, meanwhile, founding that shaft lining’s stress-strain relationship is dynamic when the composite loads are applied and that the plastic zone of shaft lining is resulted from coupling of multiple loads. Therefore, decreasing the transmission coefficient of bottom aquifer and the elasticity modulus of shaft lining concrete is beneficial to reduce the vertical additional force of shaft lining and increases the stability of shaft lining.

Abstract: A pseudolinear equivalent method is proposed to analyze the nonlinear deformation of reinforced concrete structure member. In this method, the real moment of a bending member is transformed into equivalent moment by means of acquiring the bending moment-curvature relation of the section, and then the equivalent concentrated forces along the member are gained through the differential relationship between bending moment, shear force and distributed force. By this method, the problem of nonlinear system can be transformed into the problem of linear system. This method can analyze the deformation of RC structure members with constant or variant sections, which can be extended to analyze the nonlinear deformation of the structure members made of other kinds of engineering materials. The analyzed result given by this method fits the result attained from finite element method very well, which proves the feasibility of the model.

Abstract: In order to compare precisions of different finite volume schemes for plane stress problems, this paper discussed three typical finite volume schemes(FVM2, FVM3 and FVM4) through theoretical deduction and example verification, and introduced a new scheme(FVM1). Force equilibrium equations were obtained, which derived from the principle of the finite volume method (FVM). Using triangular units and in view of internal cells and boundary elements, this paper put forward these four finite schemes linear equations similar to the finite element method(FEM) stiffness equations but with different coefficients. The analyses and numerical example results show that FVM1 is the optimal finite volume scheme, and suggest that in practical civil, architectural and hydraulic engineering calculations, schemes should be selected carefully and FVM1 is a good option.

Abstract: The composite beam is composed of the brittle material element and ductile material element (for example: concrete and steel), and with shear connectors it decreases the slip between the brittle material element and ductile material element, and ensures the coordination and integrity of the cross section. When there are cracks in brittle material element in use, it will increase interface slip. In this paper, we assume that the brittle material has cracks, and calculate the slip of shear connectors. Letting the end slip equal to the ultimate slip of shear connector, the shear force and ultimate moment of composite beam is gotten.

Abstract: People have widely uesd long- history wooden buildings in the ancient and mordern architecture.But the modulus of elasticity of the wood is smaller as well as the fact that the stiffness of wood is lower. In order to solve the problem of deficiency of the stiffness of large-span wooden beam from the practical engineering, this paper presents the method of external prestressed wooden beam, and the calculation method of deflection of wooden beam through model test of 1:2 scale. In addition to it, the paper also analyzes the factors which affect stiffness of wooden beam. The result shows that stiffness of this kind of wooden beam is greatly improved compared with the common wooden beam in the same cross section. Steel has a predominant tensile characteristics, it is an effective method to reduce undue deflection of large-span wooden beam by external prestress method. This construction techniques has greatly applicational value in the reinforcement and strengthening ancient buildings and modern design and construction of large-span timber structure buildings and bridges.

Abstract: Space fractional advection dispersion equation includes non-local differential operators, which leads to calculating numerical integrals with weakly singular kernel on every subintervals. Oscillations are visible in computed solutions when fractional order tends to 1. Studies show that the stiffness matrix of time semi-discretization can be calculated directly by formulas established from a special variational formulation. Oscillations are eliminated by using adaptive moving mesh and De Boor algorithm, while the number of nodes remains unchanged.

Abstract: In order to study the characteristics about deformation and stress of four-tube concrete-filled steel tubular(CFST) laced columns of no yield point, a test with the parameter of eccentricity on two our-tube concrete-filled steel tubular(CFST) laced columns of no yield point has been finished by means of 500t press. The results of the test shows that the larger the eccentricity, the more obvious the global deformation of laced columns tends to become, and the four-tube CFST laced columns of no yield point under eccentric compression were subjected to overall bending failure and ductile failure with obvious premonition; In the meanwhile, confinement effect of main tubes away from the loading point of laced columns under eccentric compression was inapparent , while confinement effect of the two main tubes close to the loading point begain to play and increase before it was to fail, which made the characteristics about deformation and stress of the the two main tubes close to the loading point similar to the single CFST column under axial compression.

Abstract: Magneto-rheological damper is an adjustable damping smart drive. Its advantage lies that the magneto-rheological fluid can rapidly and reversibly change Newtonian fluid with good liquidity into plastic solid with high viscosity and low liquidity in the millisecond time. And then it can be easily combined with control. MR damper has obtained a certain application in vibration control of automotive, machinery, construction and other areas. In this paper, the writer focus on describing control strategy present situation and the advantages and disadvantages of various control strategies of magneto-rheological damper based on impact load. And he makes a more detailed analysis of difficulties and future trends of magneto-rheological damper based on impact load.