Advanced Materials Research Vols. 472-475

Abstract: This paper describes the cast structure study of A357 aluminum alloy stress frame casting under consecutive solidification and simultaneous solidification by test and numerical simulation methods, with the conclusions of tensile tests by using of SEM and EDS analysis, the mechanical properties and fracture morphology were observed both under the cast and T6 heat-treatment state. Intergranular fracture cracks were observed to be the main failure mode in the casting state condition, cracks originated from the tissue defects and continued to proliferate until the tensile specimens were ruptured. Simultaneous solidification can decrease the casting shrinkage and micro-cavity and improve the mechanical properties of the castings. Dimple fracture was the dominated failure mode after T6 heat treatment state, the distribution of some intergranular cracks staggered with dimple fracture can surveyed under the fractography analysis. The superiority of simultaneous solidification was demonstrated by the numerical simulation of China casting CAE.

Abstract: A three-dimensional extended finite element algorithm coupled with the level set method is developed for curvilinear crack front problems. This method does not need to force the discontinuities to be in conformity with the mesh. In order to compute the pointwise stress intensity factors along the curvilinear crack front, an orthogonal curvilinear coordinate system is constructed at the intersection point between the crack front and a surface of the crack front element. As the crack surface is expressed by the level set method, no explicit meshing of the crack geometry emerges on the crack front. This makes the domain integral more difficult. An independent grid of hexahedral cells around the crack front needs to be built as the virtual extension domain for accomplishing the domain integral. To assess the accuracy of the approach, an example with semi-elliptic crack surface is considered. The results show excellent agreement with the results calculated by the standard finite element method and those obtained from the literature.

Abstract: The main purpose of the paper is using multi-functional sensors to detect the vehicle attitude (the tilt angle of vehicle), and many other vehicle information. Combining all the information, the adaptive front-lighting system can achieve the real-time control of the pitman arm and yaw angle for automobile headlight system. The feasible control methodology could highly enhance the safety of driving and electronic additional value in automobile industry. In the paper, various conditions of HID (High Intensive Discharge) headlight system could be controlled, such as the control of pitman arm and yaw angle, are widely discussed. In the pitman arm angle control, we use G-sensor to detect the unbalanced vehicle caused by load, rugged road, uphill and downhill. Finally, combining the velocity obtained from the ECM (Engine Control Module), the leveling motor control for headlight pitman arm angle real time and adjust will be realized. On the other hand, we use the potentiometer and micro switch to sense the direction and quantity of steering wheel angle, the swivel motor control for headlight yaw angle real-time adjustment is completed.

Abstract: By using the Reynolds stress turbulence model at big Reynolds number condition and computational fluid dynamics, the data simulating calculation was carried out to the safety valve inner flow field with different opening size and different valve structural parameters. The result were showed in visual graphics , and the study showed that the valve structural parameters impact on the flow field distribution , the cavitation creation and the flow noise greatly.

Abstract: Hydropower project investment decisions facing the market risk mainly for electricity price volatility. In this thesis, we are using Monte Carlo method analyzes market risk of XiLuoDu hydropower project. Result shows the practicability and effectiveness of Monte Carlo method.

Abstract: The selection of the mold parting surface, gating system, core-pulling mechanism, injection machine and computational problems of injection mold structure is described by analyzing the structural characteristics and requirements of the plastic thermos shell. In order to improve productivity and reduce production costs, Pro/E is applied to the design of injection molding mold. At the same time, Plastic Adviser is used in the liquidity analysis of shell .This method can reduce design time and production cycle.

Abstract: The velocity of the wiper arms is a key factor which can influence the clarity of the windshield and the comfort of the driver’s view. So how to control the velocity of the wiper arms is important. To solve the problem, a method is elaborated based on feedforward-feedback composite controller. It introduces the hardware and software design based on the feedforward-feedback algorithm, controlling the velocity of the wiper arms by adjusting the duty of PWM. The experimental results indicate that the smart wiper system is reliable, and has good accuracy and real-time performance.

Abstract: The porous Cu film was deposited on soft PVDF substrate by magnetron sputtering at different sputtering pressure. The microstructure and electrical properties of Cu films were investigated as a function of sputtering pressure by X-ray diffraction XRD and Hall effect method. The results show that the surface morphology of Cu film is porous, and the XRD revealed that there are Cu diffraction peaks with highly textured having a Cu-(220) or a mixture of Cu-(111) and Cu-(220) at sputtering pressure 0.5 Pa. The electrical properties are also severely influenced by sputtering pressure, the resistivity of the porous Cu film is much larger than that fabricated on Si substrate. Furthermore, the resistivity increases simultaneously with the increasing of Cu film surface aperture, but the resistivity of Cu film still decreases with the increasing grain size. It can be concluded that the crystal structure is still the most important factor for the porous Cu film resistivity.

Abstract: In order to study the wavefield response of heterogeneous structure in seismic section, firstly, we have got the 2-D P-wave data for two kinds of heterogeneous structure in the physical model of a 3-D heterogeneous sand layer. Then, we choose several typical single shot seismic records and minimum offset gathers for wavefield analysis. Finally, we show two images generated by using reverse time migration (RTM) on the recording data. Experimental results indicate that, heterogeneous structure’s information is included in every single shot record; each heterogeneity forms a diffractor whose diffraction response, which affects the imaging of the interface between the heterogeneous region and the homogeneous region, is especially obvious in the minimum offset gathers; diffraction wave could be eliminated by RTM imaging, which could reflect the position of heterogeneous structure in reality; the differences of the wavefield response of the two kinds of heterogeneous structures are mainly reflected in the divergences of the events’ scale and power of the heterogeneities.

Abstract: The paper established the mechanical model of SFD-sliding bearing flexible rotor system, adopting Runge-Kutta method to solve nonlinear differential equation, thus acquiring the dynamic response and the unbalanced response curve. The study has shown: from stable periodic motion, the route of the flexible rotor system to go into chaos is: periodic motion—quasi-periodic motion—chaos—period doubling bifurcation—chaos. The paper analyzed the sensitivity of the first two critical speeds of flexible rotor system, offering design variables for optimization analysis, improving the efficiency of optimization and shortening the design cycle.