Applied Mechanics and Materials Vol. 197

Abstract: The drivers were hurt seriously by the vehicle steering column in the frontal collision. So a steering column with well energy-absorbing is very useful for the drivers. In this paper, the crashworthiness of a vehicle steering column is investigated by using the explicit dynamics finite element analysis method. Based on the proposed finite element model, the steering column with different material parameters including elastic modulus and yield strength are analyzed. Moreover, the displacement, velocity and energy absorption is discussed. The simulation results show that the crashworthiness of the vehicle steering column is significantly influenced by the yield strength. However, the elastic modulus has little effect on the crashworthiness.

Abstract: As a further generalization of fuzzy set theory, the vague set theory can overcome the shortcomings of fuzzy set by describing the membership from two sides of both TRUE and FALSE, rather than only by a single membership value. Since vague sets can provide more information than fuzzy sets, it is superior in mathematical analysis of system with uncertainty. Thus, vague set is more powerful in the describing and processing of uncertain, inaccurate, even conflicting information. In this paper, a new method vague set-based is proposed to deal with fuzzy decision fusion problem. Compared with traditional fuzzy decision fusion method- such as fuzzy comprehensive evaluation, the new method is more efficient and powerful to fulfill decision fusion with uncertain and inaccurate information. Generally, the new method is the same with group decision fusion and soft fusion.

Abstract: 75% to 80% of the mobile robots cost is determined by product design. Under normal circumstances, the quoted price of the product design is about 12% to 15% mobile robots price during the current market quoted price. The costs and the cost difference between virtual and traditional mobile robots design can be compared quantitatively by fuzzy evaluation using the product design cost function. The quantitative comparison results according to the mobile robots design showed that virtual design costs were significantly lower than traditional designs costs.

Abstract: Pro/E software was utilized to build the three-dimensional model. Then, the large-scale computational fluid dynamics software ICEM software was used to build unstructured grid of wastewater treatment pool. Based on the CFX software，the wastewater treatment pool was numerically simulated by dynamic coordinate system technology and RNG k-ε turbulent model and PIOS algorithm, and fluid flew in the wastewater treatment pool was analyzed. Considering motor rotor system participates as part of the rotor system in calculation, rotor system of submersible mixer was strength analysis and modal analysis based on fluid-solid coupling. The results show that: the fluid in wastewater treatment pool can be propelled by the submersible mixer, and diffuses along the radial. The rotating speed of the submersible mixer is far smaller than critical speed, so the rotating speed is safe and reliable. This methold has certain significance. It can guide submersible mixer hydraulic performance in design, simulation and Engineering application.

Abstract: To improve accuracy and efficiency of the hydraulic design of the guide vanes of the multistage centrifugal pumps, four different-structured guide vanes are investigated, and the design processes of those systems are established. The secondary development platforms of the ObjectArx2000 and the UG/NX OPEN are utilized to develop the hydraulic design systems of the guide vanes. The error triangle method is adopted to calculate the coordinates of the vanes, the profiles of the vanes are constructed by Bezier curves, and then the curves of the flow areas along the flow-path are calculated. Two-dimensional and three-dimensional hydraulic models can be developed by this system.

Abstract: In this paper, the conflux channel of the containment sump strainer in nuclear power station was adopted as the research object. The modal analysis and the stress calculations were conducted in LOCA (Loss-of-Coolant Accident) condition to test the validity of the conflux channel. The research results could provide the basis for designing the double filter cylinder of the compact containment sump strainers.

Abstract: Under cyclic loading, the material weakening processes in structural members inevitably involve multiple cracking originating from some of the spatially-distributed initial flaws and imperfections, and hence diverse cracking behaviors can be expected. It is known from previous studies on multiple cracks that, the cracking behavior in a structural member can abruptly change as a crack or a number of cracks reach a critical value of crack propagation, causing sudden strength degradation. In this study, by applying sequential loads at different locations of the same FE model of a notched beam, it is shown that this unique strength degradation mechanism can repeatedly occur as cracks propagate under sequential loads, leading to multistage strength degradation of the member. This result is in line with early experimental findings that the load-carrying capacity of a notched concrete beam under bending decreases in a similar fashion as the sizes of multiple initial notches are arbitrarily increased. This study has important implications for understanding the fundamental fatigue mechanisms of various engineering materials.

Abstract: Characteristic parameters of joint surfaces are needed in kinetic modeling of the motor frame while analyzing its vibration behavior. In this paper, research on tangential dynamic characteristics of mechanical joint surfaces in the motor frame is executed. In order to get the tangential contact stiffness and contact damping of interfaces in the motor frame under different joint conditions, an experimental method is proposed according to the structure feature and running condition of motors. A test platform is specially designed and set up. The kinetic model of test specimens (including the test joint surfaces) is derived. The experimental system is developed. The tangential dynamic contact stiffness and contact damping are identified by the experimental system. The variation rules of the contact stiffness and contact damping with changing of pre-load, exciting frequency and surface roughness are got and summarized. And the rules are consistent with the physical essence of joint surfaces.

Abstract: Positioning systems with higher speed and accuracy are required in semiconductor package manufacturing, and the product quality and production efficiency can be further improved. So this paper presents a new 2-DOF precision positioning platform with high speed. The platform is directly driven by linear motors, and a novel elastic decoupling mechanism is put forward. High positioning accuracy and good stability in a short stroke, high precision and high speed movement can be achieved using linear motors. The X axis and Y axis kinematic decoupling is realized through the novel elastic decoupling mechanism based on a preloaded spring and flexure hinges, and the dynamic characteristics of the system are improved. The dynamic characteristics of the positioning platform in free state are investigated based on finite element analysis, and the natural frequencies and vibration modes of the positioning platform are obtained, which provides theoretical basis for the further dynamic control of the positioning platform.