Applied Mechanics and Materials Vols. 670-671

Abstract: Statics is set up on the basis of 4 axioms of statics. Although these axioms are distillate and summarizing of the accumulated humankind's experience in long-range production and life, introduction of these axioms to statics seems a bit abrupt, especially the critical axiom "resultant of two forces" far fetched. This article was an attempt to present the embodying description of the effect of force and force system, based on the nature of effect of force and the equivalent and equilibrium of force systems. On this basis, theorem of two forces resultant and the theorem of two forces balance were proved, and the theorem of force systems equivalent was brought up. A new framework of static equilibrium system was built up to try to make a more perfect and more reasonable description for static equilibrium.

Abstract: According to the principle of harmonious dimensions, the qualitative distribution model of the internal pressure on elbow pipes were determined; Through FLUENT numerical simulation, the internal pressure were given under 96 kinds of gas fluid conditions; By analyzing the variation of the internal pressure with flow and geometrical parameters, the variation of the internal pressure distribution within the elbow pipes has been studied; By means of 1stOpt nonlinear fitting package, the formula of three-dimensional internal pressure distribution was determined; Compared with the numerical results, the maximum relative error is 0.012%. The formula provides theoretical bases for strength check, the transport pipeline and wall thickness design of the high pressure, high velocity elbow.

Abstract: The flight mechanism of flapping-wing was studied by using the translation-rotation model. We established the flapping-coordinate of the wing, gave the equation of the motion, and simplified the flapping-wing model. The aerodynamic and vortices were simulated by the CFD software of Fluent. The leading-edge vortex generated in the translation phase, and delayed stall mechanism had an important effect on the high lift. In the rotation phase, lift peaks appear due to the wing rapidly rotating and rotational circulation mechanism. The aerodynamics were obtained in different amplitudes, frequencies, angles of attack, the locations of rotating axis and timings of rotation. The influence of these parameters on average lift coefficient is obvious, while it can be ignored to average drag coefficient. Keywords: wing, aerodynamics, vortices, numerical simulation.

Abstract: Intermediate turbine duct represent the flow path between the high pressure and low pressure turbine. Caused by the complex flow mechanism, the outlet flow condition of the high pressure turbine is easily changed. Since the upstream flow condition from the high pressure turbine has a significant effect on the internal flow field of intermediate turbine duct, the study in the upstream condition is of high value. Through numerical simulation, the influence of upstream flow angle variation on intermediate turbine duct is observed. It is found that the main influence of the flow angle variation is near the hub side of the duct, and the quantitative result shows that a larger flow angle has a positive effect on the flow field and can reduce loss.

Abstract: This paper established the nonlinear dynamic model of finished automobile to study the influence of suspension structural parameters, automotive braking and steering on the vehicle driving comfort and handling stability. The simulation results show that in the vehicle steering process, the body roll changed indirectly the tire lateral force, which had the impacts of yaw and lateral movement, and the interaction between the suspension and steering between systems is very significant especially under condition of the uneven road excitation. When the peak of the tire steering angle increased, the roll angle of vehicle body became larger and larger, followed by the change of body posture and the deterioration of ride comfort. With the increase of the steering angle, the lateral acceleration of the vehicle became larger and larger, and even resulted in tire skidding, thus reducing the driving safety of the vehicle.

Abstract: Free-standing museum cultural relics are easy to fall off exhibition booth and get damaged under earthquakes. To find an effective method to mitigate damage of cultural relics due to fall off, influences of soft pad under relic was studied by ANSYS/LS-DYNA program. A bronze relic supported by a soft pad was selected for analysis. Based on material properties of both the relic and the pad, finite element model of the relic was built. By simulation, Von mises stress distributions, acceleration response curves as well as kinetic energy curves of the relic were obtained; effects of the soft pad to mitigate damage of the relic were discussed. Results show that collision between the falling museum cultural relic and ground can be mitigated by soft pad due to its buffer as well as energy absorption effects. It is suggested to use soft pad under relic to provide protection. Besides, by ANSYS/LS-DYNA program, falling off process of free-standing museum cultural relics can be effectively simulated.

Abstract: The distinctive paper is devoted to wavelet-based discrete-continual finite element method (WDCFEM) of structural analysis. Two-dimensional and three-dimensional problems of analysis of structures with piecewise constant physical and geometrical parameters along so-called “basic” direction are under consideration. High-accuracy solution of the corresponding problems at all points of the model is not required normally, it is necessary to find only the most accurate solution in some pre-known local domains. Wavelet analysis is a powerful and effective tool for corresponding researches. Initial continual and discrete-continual formulations of multipoint boundary problems of two-dimensional and three-dimensional structural analysis are presented.

Abstract: The distinctive paper is devoted to wavelet-based discrete-continual finite element method (WDCFEM) of structural analysis. Discrete-continual formulations of multipoint boundary problems of two-dimensional and three-dimensional structural analysis are transformed to corresponding localized formulations by using the discrete Haar wavelet basis and finally, with the use of averaging and reduction algorithms, the localized and reduced governing equations are obtained. Special algorithms of localization with respect to each degree of freedom are presented.

Abstract: Horizontal well hydraulic fracture construction technology has already become the main development means of low permeability reservoir, and the crack initiation pressure is a key factor in fracture construction. Taking ABAQUS as the platform, combined with rock mechanics, elastic mechanics, fracture mechanics, damage mechanics and fluid-solid coupling theory, to establish horizontal well mechanical model, crack initiation law of horizontal well under different conditions were obtained by using finite element method. According to the horizontal well fracture tested data in Daqing peripheral oil fields, the crack initiation pressure and numerical simulation results are in good agreement, it shows that the numerical simulation method is reasonable, then analyze influence factor of crack initiation pressure on the basis.

Abstract: The distinctive paper is devoted to problem of identification the dynamic characteristics of mathematical models based on the measured dynamic characteristics of real constructions. It is describes a problem of discrepancy of measured and modeling eigen pairs. It is shown that the problem is systemic. The creation and verification processes of mathematical (finite element) models used in the design constructions need some work and adjustments. For a reliable analysis of the construction ways are suggested to overcome the identified gaps using adaptive procedures.