Applied Mechanics and Materials Vol. 302

Abstract: 7075 aluminum alloy is one of the most popular materials for structure. There are lots of demands for welding these structural materials. During the fast high temperature heating and cooling process serious residual stress is generated that causes the deterioration of structure strength. In this study, we investigate the residual stress induced in 7075 aluminum alloy after gas tungsten arc welding. X-ray diffraction method is applied to measure the residual stress under different joint angles. The angular distortion is also measured by a 3-D imaging system. Results show that both residual stress and angular distortion increase with the preparation angle.

Abstract: Curtain wall system shows good performance for daylighting and openness, but it also causes deterioration of thermal comfort because it brings too much solar irradiation to interior space. So in this study, to reduce heating and cooling loads, some passive items, such as window-wall ratio, air exchange rate, outdoor louver, and composition of window glass were adopted to a university office building and the monthly heating-cooling loads were evaluated by EnergyPlus simulation. The actual energy usages were compared to loads of simulation data to verify simulation accuracy and real data and simulation result showed good match. As a result, air exchange rate and interior setpoint temperature influenced on thermal loads more than the other passive items.

Abstract: In this paper, an optical structure for the aircraft was considered and its vibrational characteristics and weight were optimised using the robust design technology. To acquire the vibration characteristics and the stable line of sight, modal analyses were performed to the optical structure using the commercial multi-body dynamics programme ADAMS. Four design variables, were selected to investigate the vibrational characteristics as well as lightweight effect using the L9(34) type orthogonal array. To fulfill the natural frequency criterion (75Hz), the proper values of each design variable were suggested.

Abstract: One way to achieve lightweight and lubricant-free drive train is, among others, to convert conventional steel to polymer composite materials. This paper describes a part of this endeavor by taking a spur gear pair as a study object. One of the steel gear wheel is replaced with three different materials including Victrex PEEK 650G, Victrex PEEK 650CA30 and Luvocom PEEK 1105-8165 while keeping the gear geometry unchanged. Mechanical stresses and thermal properties are two major criteria for material selection at this stage. Therefore carbon fiber filled PEEK (Victrex PEEK 650CA30) and PEEK filled with thermal conductive minerals (Luvocom 1105-8165) are chosen to benchmark each of the criterion. The evaluation is done by modeling the gear mesh and analyzing the contact forces and heat generated in the gear tooth. The results show surface temperature on the tooth flanks, root tensional stress and contact pressure during the tooth mesh. The work suggests a guideline of materials selection. Depending on actual application a compromisation between mechanical and thermal properties often needs to be considered within the tolerance boundary in order to obtain optimized results. This work only deals with material selection. Gear design such as optimization of tooth geometry for polymer gears is out of the scope of this study and will not be discussed.

Abstract: A particle swarm optimization-based radial basis function network (PSO-RBFN) is presented to diagnose vibration faults of steam turbine-generator sets (STGS) in a power plant. The proposed PSO algorithm is used to automatically tune the control parameters of the RBFN. The test results demonstrate that the proposed PSO-RBFN has a higher diagnostic accuracy than the RBFN and multilayer perceptron network (MLPN) trained by error back-propagation algorithm. Moreover, this paper has demonstrated that the proposed PSO-RBFN can be as a reliable tool for vibration fault diagnosis of STGS.

Abstract: This paper presents the experimental results of a study carried out to investigate the performance of small scale concrete columns retrofitted with unidirectional carbon fiber-reinforced polymer (CFRP) in fire situation. This study aims at the effectiveness of CFRP through the contrast test. In order to observe the residual compressive strength, the specimen was heated to a target temperature and mechanically tested under axial compression. Other similar heated specimen was cooled down to the room temperature and mechanically tested too. This procedure was repeated by temperatures of 200oC, 300oC, 350oC, 400oC, 450oC, 500oC, 600oC, 700oC, 800oC and 1050oC. The heating inside the furnace was controlled in such a way that the average temperature in the furnace followed the standard time-temperature curve, ISO 834 [1]. The experimental results comproved that, due to low temperature resistance, the CFRP systems are not capable of safely and adequately enduring fire for any substantial period of time. This study evaluated a supplementary residual compressive strength of CFRP systems after cooling down to the room temperature. Finally, this study should benefit CFRP-fire research efforts by providing a similitude relationship for the testing of full-scale and small-scale specimens.

Abstract: This paper utilized an intelligent vehicle model for the “Freescale” Cup National College Students' Intelligent Vehicle competition as the main study object. Under the prerequisite of adopting the same control procedures and algorithms, the mechanical structures and its parameters of the model vehicle which influence the running performance, such as front wheel alignment, steering mechanism and rear wheel deceleration mechanism are optimally designed and adjusted .It has been proved that the scheme induced the model vehicle driving fast and stable on the path-complex track and thus to achieve reasonable effects.

Abstract: Motor base is an important component of the traction motor, it is not only the base to install other components of the motor , but also the magnetizer that contact different magnetic poles. In order to ensure its operation performance, the motor base need good rigidity performance. This paper utilizes the finite element technique, analyzing the frame in the strength under four different conditions. The results show that, in the utmost stress condition, the stress is lower than the allowable value, and the frame has a certain degree of safety, the structural parameter of the base meets the requirement of material strength.

Abstract: For deciding the structure and parameters of Skin flesh leaf separation machinery of Stems and leaves separation mechanism of corn stalk,the Skin flesh leaf separation machinery key mechanism—leaf-stripping mechanism was experimented in the paper by Self-designed leaf-stripping equipment. For optimization parameters in structure and motion of leaf-stripping mechanism,the experimental method of the three-factor quadratics rotary orthogonal combination was adopted, and two evaluation indexes were applied in the experiment. By carrying on the experiments, the suitable parameters in structure and motion were obtained as below, rotation speed of leaf-stripping roll was 921～1224rpm. leaf-stripping teeth plate clearance was 36.8～41.5mm. and moisture content of corn stalk was 44.9％~65％ .

Abstract: Mass concrete temperature cracking is an important problem of concrete foundation safety in civil engineering projects, which exists from construction process of concrete foundation to operation period. This paper introduces the simulation method of mass concrete temperature cracking propagation process by Finite Element Method(FEM). With the concrete heat conduction problem, an example to study concrete surface cracks of the whole process of pouring concrete caused by temperature changes and discussed how concrete cracking process brought from temperature decrease is simulated by FEM. The results show that the finite element method can effectively simulate the development of concrete block cracks under temperature stress. The calculation result accord the cracks distribution law of mass concrete blocks in the uniform temperature drop and the basis of strong constraints.