Applied Mechanics and Materials Vols. 29-32

Abstract: Crack prevention of high-rise building foundation is an interesting and difficult issue to engineers. Reasons for the crack are analyzed first. Then, based on project cases, crack control methods of large volume concrete foundation are studied in terms of active part and passive part. Active part includes optimizing design of concrete, optimizing foundation design and improving confining condition. Passive part includes reducing temperature difference and increasing the fracture strength of concrete. Finally, optimum foundation design is emphasized for crack control of large volume concrete foundation.

Abstract: The three dimensional model of a 2-cylinder diesel engine block is established with the P ro/E software, and then the modal analysis of the engine block is carried out using finite element method with ANSYS software . Through the analysis, the inherent frequencies and mode shapes of the first 6 order modes are obtained respectively, and then are compared with the testing result; comparison shows the results of FEA estimation are in good agreement with those of testing which indicates the FEA results’ correctness. The results of the relative distribution of the vibration magnitude in the whole block are given, which provide necessary guides for the dynamic optimal design of the engine block.

Abstract: This text has put forward the basic conception of visual angle, inside the track and outside the track. According to characteristic of controlled five-bar mechanism that can realize track of many points accurately, optimization model of controlled mechanism that can accurately realize track of many points was built. The method of generalized inverse based on windows solves optimal solution to displacement, speed, and acceleration of compensation movement and respond frequency as goal function. The instance calculating indicates that this method is practical and feasible.

Abstract: In this paper, the mechanical behaviours of open-cell and closed-cell aluminium foams against spherical-nosed projectile penetration are studied theoretically. An analytical model based on dynamic cavity expansion theory and previous experiment data is presented. The analytical equations are derived for the penetration resistance and the final penetration depth during the whole penetrating process. The effects of the mass density of target material, the geometry and initial velocity of the projectiles on the final penetration depth are investigated in detail. It is shown that the final penetration depth mostly lie on the density of aluminium foams and the kinetic energy of projectile. When the density of target is smaller, the final penetration depth of projectile in the closed-cell aluminium foams target is obviously smaller than that in the open-cell aluminium foams target. Meanwhile, with the increase of density of target and the decrease of initial impact velocity, the difference of the capacity of absorbing energy between open-cell and closed-cell aluminium foams targets becomes gradually narrow.

Abstract: In order to conduct the cleaning of spilled oil, to protect the marine ecological balance and to prevent the damage to marine environment by oil spill, the simulation of oil spill in deep water with the wave motion, wind and current was built by the user defined function and the volume of fluid in FLUENT. The dispersion and diffusion of oil spill in deep water was simulated dynamically. Also the oil spilling trajectories under the conditions of different current velocities, wavelengths and wind velocities were compared and analyzed, respectively. The results showed that the current, wind and wave decided the location and areas of oil films on the sea surface. The water depth influenced by the wave which increased with the increasing wavelength. Meantime, the areas of oil films on sea surface increased with current velocity decreasing, while the distance between the oil film and the source of oil increased. With the wind velocity increasing, the extended length of oil dispersion underwater and the oil film area on surface increased.

Abstract: Sliding velocity has a direct impact on friction heat and contact situation. Frictional heating and associated temperature seriously affects the material chemical and physical - mechanical properties, and is one of the direct factors on the wear mechanism. To analyze the influence of the sliding speed on the maximum contact temperature, contact pressure, stress, etc, a 3D thermo-mechanical coupling model for the rough surface frictional sliding is established. The rough surface is characterized based on fractal theory. The model considers friction contact between an elastic flat plane and an elasto-plastic rough surface. Also, the model integrates the heat flux coupling between the sliding surfaces and allows the analysis of the effects of elastic-plastic deformation of rough body and the interplay among asperities. The numerical results from the analysis and simulation show that the maximum contact temperature increases with the increasing of the sliding velocity. But the maximum VonMises equivalent stress and the maximum contact pressure have few relationships with sliding speed. They may increase or reduce with the sliding velocity increasing. Some results are validated by research’s results available in the literature.

Abstract: This paper proposes an improved computational algorithm for structure topology optimization. It integrates the merits of Evolutionary Structure Optimization and Level Set Method (LSM) for structure topology optimization. Traditional LSM algorithm has some drawbacks, for instance, its optimal topology configuration is largely dependent on the structural topology initialization. Additionally, new holes cannot be evolved within the updated topology during the optimization iteration. The method proposed in this paper combines the merits of ESO techniques with the LSM scheme, allowing new holes to be automatically inserted in regions with low deformation energy at prescribed iterations of the optimization. The nodal neighboring region is a good selection. For complex structures in which holes cannot be properly inserted in advance, the proposed method considerably improves the ability of LSM to search the optimal topology. In addition to achieving more accurate results, the proposed method also yields higher efficiency during optimization. Benchmark problems are presented to show the effectiveness and robustness of the new proposed algorithm.

Abstract: Magneto-rheological (MR) dampers, recently, have been widely utilized in many different areas of engineering for their high properties. There are two different kinds of problems for MR dampers, the direct model and the inverse one. It is difficult to express of the direct model of the MR damper for its high nonlinearity and hysteretic characteristics. It is much more difficult to get the inverse model of MR damper, which means the determination of the input voltage so as to gain the desired restoring force decided by the control law. When identifying the direct and the inverse model of MR damper with Adaptive Neuro-Fuzzy Inference System (ANFIS), there exists curse of dimensionality of fuzzy system. Therefore, it will take much more time, and even the inverse model may not be identifiable. The paper presents a hierarchical ANFIS to deal with the curse of dimensionality of the fuzzy identification of MR damper and to identify the direct and the inverse model of MR damper. The numerical simulation proves that the proposed hierarchical ANFIS can model the direct and the inverse model of MR damper much more quickly than ANFIS without more changing of identification precision. Such hierarchical ANFIS shows the higher priority for the complicated system, and can also be used in system identification and system control for the complicated system.

Abstract: The paper designs a temperature control system based on AT89C51 and DS18B20. The design uses the DS18B20 digital temperature sensor as the temperature acquisition unit and the AT89C51 microcontroller unit to control them, not only have the advantages that easy to control and with good flexibility, but also can greatly enhance the controlled temperature index.

Abstract: A physics-based material processing simulation is approached to research the machining distortion for high speed milling of titanium alloy aircraft monolithic component by the finite element method (FEM). Several mechanics models, such as material constitutive model, material removal model, and cutting loads application model, have been implemented to improve the accuracy of finite element simulation. The distortion result of aircraft monolithic component resulting from FEM show a good agreement with the experiment result. The research result shows that the distortion law of titanium alloy aircraft monolithic component is bending distortion and protruding upward, and the maximum distortion dimension lies in the middle of monolithic component.